Six-year supplementation with alpha-tocopherol and beta-carotene and age-related maculopathy

Carotenoids for lung cancer chemoprevention and chemotherapy: Promises and controversies

BACKGROUND

Lung cancer is one of the leading causes of malignancy in the world. Several therapeutical and chemopreventive approaches have been practised to mitigate the disease. The use of phytopigments including carotenoids is a well-known approach. However, some of the prominent clinical trials interrogated the efficacy of carotenoids in lung cancer prevention.

METHODS

A elaborate literature survey have been performed investigating in vitro, in vivo, and clinical studies reported on the administration of carotenoids for chemoprevention and chemotherapy.

RESULTS

Tobacco consumption, genetic factors, dietary patterns, occupational carcinogens, lung diseases, infection, and sex disparities are some of the prominent factors leading to lung cancer. Significant evidence has been found underlining the efficiency of carotenoids in alleviating cancer. In vitro studies have proven that carotenoids act through PI3K/ AKT/mTOR, ERK-MAPK pathways and induce apoptosis through PPAR, IFNs, RAR, which are p53 intermediators in lung cancer signaling. Animal models and cell lines studies showed promising results, while the outcomes of clinical trials are contradictory and require further verification.

CONCLUSION

The carotenoids exert chemotherapeutic and chemopreventive effects on lung tumors which has been evidenced in numerous investigations. However, further analyses are necessary to the answer the uncertainties raised by several clinical trials.

Nutritional supplementation in the prevention and treatment of Glaucoma

Glaucoma is a chronic optic neuropathy that creates a significant burden on public health. Oxidative stress is hypothesised to play a role to glaucoma progression, and its reduction is being analysed as a therapeutic target. Dietary antioxidants play a crucial role in helping provide insight into this hypothesis. We reviewed 71 trials, interventional, I -vivo and I -vitro, including 11 randomised controlled trials, to determine if adjunctive nutritional supplementation could lead to a reduction in oxidative stress and prevent glaucomatous progression. Many laboratory findings show that vitamins and natural compounds contain an abundance of intrinsic antioxidative, neuroprotective and vasoprotective properties that show promise in the treatment and prevention of glaucoma. Although there is encouraging early evidence, most clincial findings are inconclusive. The group of B vitamins appear to have the greatest amount of evidence. Other compounds such as flavonoids, carotenoids, curcumin, saffron, CoQ10, Ggngko Biloba and Resveratrol however warrant further investigation in glaucoma patients. Studies of these antioxidants and other nutrients could create adjunctive or alternative preventative and treatment modalities for glaucoma to those currently available.

Treatments for dry age-related macular degeneration and Stargardt disease: a systematic review

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of visual loss in older people. Advanced AMD takes two forms, neovascular (wet) and atrophic (dry). Stargardt disease (STGD) is the commonest form of inherited macular dystrophy.

OBJECTIVE

To carry out a systematic review of treatments for dry AMD and STGD, and to identify emerging treatments where future NIHR research might be commissioned.

DESIGN

Systematic review.

METHODS

We searched MEDLINE, EMBASE, Web of Science and The Cochrane Library from 2005 to 13 July 2017 for reviews, journal articles and meeting abstracts. We looked for studies of interventions that aim to preserve or restore vision in people with dry AMD or STGD. The most important outcomes are those that matter to patients: visual acuity (VA), contrast sensitivity, reading speed, ability to drive, adverse effects of treatment, quality of life, progression of disease and patient preference. However, visual loss is a late event and intermediate predictors of future decline were accepted if there was good evidence that they are strong predictors of subsequent visual outcomes. These include changes detectable by investigation, but not necessarily noticed by people with AMD or STGD. ClinicalTrials.gov, the World Health Organization search portal and the UK Clinical Trials gateway were searched for ongoing and recently completed clinical trials.

RESULTS

The titles and abstracts of 7948 articles were screened for inclusion. The full text of 398 articles were obtained for further screening and checking of references and 112 articles were included in the final report. Overall, there were disappointingly few good-quality studies (including of sufficient size and duration) reporting useful outcomes, particularly in STGD. However we did identify a number of promising research topics, including drug treatments, stem cells, new forms of laser treatment, and implantable intraocular lens telescopes. In many cases, research is already under way, funded by industry or governments.

LIMITATIONS

In AMD, the main limitation came from the poor quality of much of the evidence. Many studies used VA as their main outcome despite not having sufficient duration to observe changes. The evidence on treatments for STGD is sparse. Most studies tested interventions with no comparison group, were far too short term, and the quality of some studies was poor.

FUTURE WORK

We think that the topics on which the Health Technology Assessment (HTA) and Efficacy Mechanism and Evaluation (EME) programmes might consider commissioning primary research are in STGD, a HTA trial of fenretinide (ReVision Therapeutics, San Diego, CA, USA), a visual cycle inhibitor, and EME research into the value of lutein and zeaxanthin supplements, using short-term measures of retinal function. In AMD, we suggest trials of fenretinide and of a potent statin. There is epidemiological evidence from the USA that the drug, levodopa, used for treating Parkinson's disease, may reduce the incidence of AMD. We suggest that similar research should be carried out using the large general practice databases in the UK. Ideally, future research should be at earlier stages in both diseases, before vision is impaired, using sensitive measures of macular function. This may require early detection of AMD by screening.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016038708.

FUNDING

The National Institute for Health Research HTA programme.

Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration

BACKGROUND

There is inconclusive evidence from observational studies to suggest that people who eat a diet rich in antioxidant vitamins (carotenoids, vitamins C, and E) or minerals (selenium and zinc) may be less likely to develop age-related macular degeneration (AMD).

OBJECTIVES

To determine whether or not taking antioxidant vitamin or mineral supplements, or both, prevent the development of AMD.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 2), MEDLINE Ovid (1946 to 29 March 2017), Embase Ovid (1947 to 29 March 2017), AMED (Allied and Complementary Medicine Database) (1985 to 29 March 2017), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/); searched 29 March 2017, the ISRCTN registry (www.isrctn.com/editAdvancedSearch); searched 29 March 2017, ClinicalTrials.gov (www.clinicaltrials.gov); searched 29 March 2017 and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 29 March 2017. We did not use any date or language restrictions in the electronic searches for trials.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing an antioxidant vitamin or mineral supplement (alone or in combination) to control.

DATA COLLECTION AND ANALYSIS

Both review authors independently assessed risk of bias in the included studies and extracted data. One author entered data into RevMan 5; the other author checked the data entry. We pooled data using a fixed-effect model. We graded the certainty of the evidence using GRADE.

MAIN RESULTS

We included a total of five RCTs in this review with data available for 76,756 people. The trials were conducted in Australia, Finland, and the USA, and investigated vitamin C, vitamin E, beta-carotene, and multivitamin supplements. All trials were judged to be at low risk of bias.Four studies reported the comparison of vitamin E with placebo. Average treatment and follow-up duration ranged from 4 to 10 years. Data were available for a total of 55,614 participants. There was evidence that vitamin E supplements do not prevent the development of any AMD (risk ratio (RR) 0.97, 95% confidence interval (CI) 0.90 to 1.06; high-certainty evidence), and may slightly increase the risk of late AMD (RR 1.22, 95% CI 0.89 to 1.67; moderate-certainty evidence) compared with placebo. Only one study (941 participants) reported data separately for neovascular AMD and geographic atrophy. There were 10 cases of neovascular AMD (RR 3.62, 95% CI 0.77 to 16.95; very low-certainty evidence), and four cases of geographic atrophy (RR 2.71, 95% CI 0.28 to 26.0; very low-certainty evidence). Two trials reported similar numbers of adverse events in the vitamin E and placebo groups. Another trial reported excess of haemorrhagic strokes in the vitamin E group (39 versus 23 events, hazard ratio 1.74, 95% CI 1.04 to 2.91, low-certainty evidence).Two studies reported the comparison of beta-carotene with placebo. These studies took place in Finland and the USA. Both trials enrolled men only. Average treatment and follow-up duration was 6 years and 12 years. Data were available for a total of 22,083 participants. There was evidence that beta-carotene supplements did not prevent any AMD (RR 1.00, 95% CI 0.88 to 1.14; high-certainty evidence) nor have an important effect on late AMD (RR 0.90, 95% CI 0.65 to 1.24; moderate-certainty evidence). Only one study (941 participants) reported data separately for neovascular AMD and geographic atrophy. There were 10 cases of neovascular AMD (RR 0.61, 95% CI 0.17 to 2.15; very low-certainty evidence) and 4 cases of geographic atrophy (RR 0.31 95% CI 0.03 to 2.93; very low-certainty evidence). Beta-carotene was associated with increased risk of lung cancer in people who smoked.One study reported the comparison of vitamin C with placebo, and multivitamin (Centrum Silver) versus placebo. This was a study in men in the USA with average treatment duration and follow-up of 8 years for vitamin C and 11 years for multivitamin. Data were available for a total of 14,236 participants. AMD was assessed by self-report followed by medical record review. There was evidence that vitamin C supplementation did not prevent any AMD (RR 0.96, 95% CI 0.79 to 1.18; high-certainty evidence) or late AMD (RR 0.94, 0.61 to 1.46; moderate-certainty evidence). There was a slight increased risk of any AMD (RR 1.21, 95% CI 1.02 to 1.43; moderate-certainty evidence) and late AMD (RR 1.22, 95% CI 0.88 to 1.69; moderate-certainty evidence) in the multivitamin group. Neovascular AMD and geographic atrophy were not reported separately. Adverse effects were not reported but there was possible increased risk of skin rashes in the multivitamin group.Adverse effects were not consistently reported in these eye studies, but there is evidence from other large studies that beta-carotene increases the risk of lung cancer in people who smoke or who have been exposed to asbestos.None of the studies reported quality of life or resource use and costs.

AUTHORS' CONCLUSIONS

Taking vitamin E or beta-carotene supplements will not prevent or delay the onset of AMD. The same probably applies to vitamin C and the multivitamin (Centrum Silver) investigated in the one trial reported to date. There is no evidence with respect to other antioxidant supplements, such as lutein and zeaxanthin. Although generally regarded as safe, vitamin supplements may have harmful effects, and clear evidence of benefit is needed before they can be recommended. People with AMD should see the related Cochrane Review on antioxidant vitamin and mineral supplements for slowing the progression of AMD, written by the same review team.

Many tocopherols, one vitamin E

Four tocopherols are available in nature and are absorbed with the diet, but only one RRR-α-tocopherol satisfies the criteria of being a vitamin. The biological activity of the different tocopherols studied in the rat by the resorption-gestation test has been inconsistently extrapolated to human beings where the tocopherols have no influence on a successful pregnancy. Diminution of RRR-α-tocopherol intake results in diseases characterized by ataxia, whose pathogenetic mechanism, despite vigorous claims, has not been clarified. The calculation of the Daily Reference Intake (DRI), necessary to prevent disease, is based on an obsolete test, the peroxide-induced erythrocyte hemolysis, called the gold standard, but of highly questioned validity. If many epidemiological studies have given positive results, showing prevention by high vitamin E containing diets of cardiovascular events, neurodegenerative disease, macular degeneration and cancer, the clinical confirmatory intervention studies were mostly negative. On the positive side, besides preventing vitamin E deficiency diseases, vitamin E has shown efficacy as anti-inflammatory and immune boosting compound. It has also shown some efficacy in protecting against nonalcoholic hepato-steatosis. At a molecular level, vitamin E and some of its metabolites have shown capacity of regulating cell signaling and modulating gene transcription.

The Age-Related Eye Disease 2 Study: Micronutrients in the Treatment of Macular Degeneration

Age-related macular degeneration (AMD) is one of the leading causes of vision loss in the elderly. With an increasingly aged population worldwide, the need for the prevention of AMD is rising. Multiple studies investigating AMD with the use of animal models and cell culture have identified oxidative stress-related retinal damage as an important contributing factor. In general, diet is an excellent source of the antioxidants, vitamins, and minerals necessary for healthy living; moreover, the general public is often receptive to recommendations made by physicians and health care workers regarding diet and supplements as a means of empowering themselves to avoid common and worrisome ailments such as AMD, which has made epidemiologists and clinicians enthusiastic about dietary intervention studies. A wide variety of nutrients, such as minerals, vitamins, ω-3 (n-3) fatty acids, and various carotenoids, have been associated with reducing the risk of AMD. Initial results from the Age-Related Eye Disease Study (AREDS) indicated that supplementation with antioxidants (β-carotene and vitamins C and E) and zinc was associated with a reduced risk of AMD progression. The AREDS2 follow-up study, designed to improve upon the earlier formulation, tested the addition of lutein, zeaxanthin, and ω-3 fatty acids. In this review, we examine the science behind the nutritional factors included in these interventional studies and the reasons for considering their inclusion to lower the rate of AMD progression.

Dietary modification and supplementation for the treatment of age-related macular degeneration

Age-related macular degeneration (AMD) causes a significant proportion of visual loss in the developed world. Currently, little is known about its pathogenesis, and treatment options are limited. Dietary intake is one of the few modifiable risk factors for this condition. The best-validated therapies remain oral antioxidant supplements based on those investigated in the Age-Related Eye Disease Study (AREDS) and the recently completed Age-Related Eye Disease Study 2 (AREDS2). In this review, current dietary guidelines related to AMD, along with the underlying evidence to support them, are presented in conjunction with current treatment recommendations. Both AREDS and AREDS2 are discussed, as are avenues for further research, including supplementation with vitamin D and saffron. Despite the considerable disease burden of atrophic AMD, few effective therapies are available to treat it, and further research is required.

Nutritional supplements in age-related macular degeneration

Age-related macular degeneration (AMD) is the most frequent cause of blindness in the Western World. While with new therapies that are directed towards vascular endothelial growth factor (VEGF), a potentially efficient treatment option for the wet form of the disease has been introduced, a therapeutic regimen for dry AMD is still lacking. There is evidence from several studies that oral intake of supplements is beneficial in preventing progression of the disease. Several formulations of micronutrients are currently available. The present review focuses on the role of supplements in the treatment and prevention of AMD and sums up the current knowledge about the most frequently used micronutrients. In addition, regulatory issues are discussed, and future directions for the role of supplementation in AMD are highlighted.

Excessive retinol intake exacerbates choroidal neovascularization through upregulated vascular endothelial growth factor in retinal pigment epithelium in mice

As a part of the visual cycle, all-trans-retinol (all-trans-ROL), the major form of vitamin A in circulating blood, is transported to the retinal pigment epithelium (RPE). All-trans-ROL is essential for normal retina function. However, recent researches have shown that excessive retinol intake can cause increase of all-trans-retinal. This can lead to the accumulation of lipofuscin, which is important in the pathogenesis of retina degeneration disease, such as dry type age-related macular degeneration (AMD). Since there are few reports regarding the involvement of all-trans-ROL in exudative AMD, we investigated the effects of all-trans-ROL in vitro and in vivo. We evaluated vascular endothelial growth factor (VEGF) expression in ARPE-19 cells and THP-1 cells after all-trans-ROL treatment using ELISA and real-time RT-PCR. In-vitro tube formation assay was performed with HUVEC cells using the conditioned medium (CM) obtained from ARPE-19 cells treated with all-trans-ROL. Transcriptional activity of retinoic acid receptor (RAR) was evaluated using luciferase assay. In mice, VEGF expressions were investigated in the retina and RPE/choroid after three weeks of excessive oral retinol intake. Laser-induced choroidal neovascularization (CNV) models were evaluated after they were fed with various doses of retinol. VEGF mRNA expression and VEGF production were significantly increased in all-trans-ROL treated ARPE-19 cells, which were inhibited by an RAR antagonist LE540. In contrast, there were no significant changes in VEGF production in THP-1 cells. Transcriptional activity of RAR was upregulated by all-trans-ROL treatment in ARPE-19 cells. The CM, obtained from ARPE-19 cells treated with all-trans-ROL, induced more capillary-like tube formation than cells treated with control vehicles. In vivo, the high retinol diet group has increased VEGF expression in the RPE/choroid and larger lesion size was induced. Our results suggest that all-trans-ROL is a pro-angiogenic factor. Excessive retinoid intake may be a potential risk factor for exudative AMD.

Do nutritional supplements have a role in age macular degeneration prevention?

Purpose. To review the proposed pathogenic mechanisms of age macular degeneration (AMD), as well as the role of antioxidants (AOX) and omega-3 fatty acids ( ω -3) supplements in AMD prevention. Materials and Methods. Current knowledge on the cellular/molecular mechanisms of AMD and the epidemiologic/experimental studies on the effects of AOX and ω -3 were addressed all together with the scientific evidence and the personal opinion of professionals involved in the Retina Group of the OFTARED (Spain). Results. High dietary intakes of ω -3 and macular pigments lutein/zeaxanthin are associated with lower risk of prevalence and incidence in AMD. The Age-Related Eye Disease study (AREDS) showed a beneficial effect of high doses of vitamins C, E, beta-carotene, and zinc/copper in reducing the rate of progression to advanced AMD in patients with intermediate AMD or with one-sided late AMD. The AREDS-2 study has shown that lutein and zeaxanthin may substitute beta-carotene because of its potential relationship with increased lung cancer incidence. Conclusion. Research has proved that elder people with poor diets, especially with low AOX and ω -3 micronutrients intake and subsequently having low plasmatic levels, are more prone to developing AMD. Micronutrient supplementation enhances antioxidant defense and healthy eyes and might prevent/retard/modify AMD.

Effects of multivitamin supplement on cataract and age-related macular degeneration in a randomized trial of male physicians

PURPOSE

To test whether long-term multivitamin supplementation affects the incidence of cataract or age-related macular degeneration (AMD) in a large cohort of men.

DESIGN

Randomized, double-blind, placebo-controlled trial.

PARTICIPANTS

A total of 14,641 US male physicians aged ≥ 50 years.

INTERVENTION

Daily multivitamin or placebo.

MAIN OUTCOME MEASURES

Incident cataract and visually significant AMD responsible for a reduction in best-corrected visual acuity to 20/30 or worse based on self-reports confirmed by medical record review.

RESULTS

During an average of 11.2 years of treatment and follow-up, a total of 1817 cases of cataract and 281 cases of visually significant AMD were confirmed. There were 872 cataracts in the multivitamin group and 945 cataracts in the placebo group (hazard ratio [HR], 0.91; 95% confidence interval [CI], 0.83-0.99; P = 0.04). For visually significant AMD, there were 152 cases in the multivitamin group and 129 cases in the placebo group (HR, 1.19; 95% CI, 0.94-1.50; P = 0.15).

CONCLUSIONS

These randomized trial data from a large cohort of middle-aged and older US male physicians indicate that long-term daily multivitamin use modestly and significantly decreased the risk of cataract but had no significant effect on visually significant AMD.

Diminishing risk for age-related macular degeneration with nutrition: a current view

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Clinical hallmarks of AMD are observed in one third of the elderly in industrialized countries. Preventative interventions through dietary modification are attractive strategies, because they are more affordable than clinical therapies, do not require specialists for administration and many studies suggest a benefit of micro- and macro-nutrients with respect to AMD with few, if any, adverse effects. The goal of this review is to provide information from recent literature on the value of various nutrients, particularly omega-3 fatty acids, lower glycemic index diets and, perhaps, some carotenoids, with regard to diminishing risk for onset or progression of AMD. Results from the upcoming Age-Related Eye Disease Study (AREDS) II intervention trial should be particularly informative.

Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration

BACKGROUND

There is inconclusive evidence from observational studies to suggest that people who eat a diet rich in antioxidant vitamins (carotenoids, vitamins C and E) or minerals (selenium and zinc) may be less likely to develop age-related macular degeneration (AMD).

OBJECTIVES

To examine the evidence as to whether or not taking antioxidant vitamin or mineral supplements prevents the development of AMD.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 12), MEDLINE (January 1950 to January 2012), EMBASE (January 1980 to January 2012), Open Grey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 26 January 2012.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing an antioxidant vitamin and/or mineral supplement (alone or in combination) to control.

DATA COLLECTION AND ANALYSIS

Both review authors independently assessed risk of bias in the included studies and extracted data. One author entered data into RevMan 5 and the other author checked the data entry. We pooled data using a fixed-effect model.

MAIN RESULTS

We included four RCTs in this review; 62,520 people were included in the analyses. The trials were conducted in Australia, Finland and the USA and investigated vitamin E and beta-carotene supplements. Overall the quality of the evidence was high. People who took these supplements were not at decreased (or increased) risk of developing AMD. The pooled risk ratio for any antioxidant supplement in the prevention of any AMD was 0.98 (95% confidence interval 0.89 to 1.08) and for advanced AMD was 1.05 (95% CI 0.80 to 1.39). Similar results were seen when the analyses were restricted to beta-carotene and alpha-tocopherol alone.

AUTHORS' CONCLUSIONS

There is accumulating evidence that taking vitamin E or beta-carotene supplements will not prevent or delay the onset of AMD. There is no evidence with respect to other antioxidant supplements, such as vitamin C, lutein and zeaxanthin, or any of the commonly marketed multivitamin combinations. Although generally regarded as safe, vitamin supplements may have harmful effects and clear evidence of benefit is needed before they can be recommended. People with AMD should see the related Cochrane review 'Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration' written by the same review team.

Vitamins E and C and medical record-confirmed age-related macular degeneration in a randomized trial of male physicians

PURPOSE

To test whether supplementation with alternate-day vitamin E or daily vitamin C affects the incidence of the diagnosis of age-related macular degeneration (AMD) in a large-scale randomized trial of male physicians.

DESIGN

Randomized, double-masked, placebo-controlled trial.

PARTICIPANTS

We included 14 236 apparently healthy United States male physicians aged ≥50 years who did not report a diagnosis of AMD at baseline.

METHODS

Participants were randomly assigned to receive 400 international units (IU) of vitamin E or placebo on alternate days, and 500 mg of vitamin C or placebo daily. Participants reported new diagnoses of AMD on annual questionnaires and medical record data were collected to confirm the reports.

MAIN OUTCOME MEASURES

Incident diagnosis of AMD responsible for a reduction in best-corrected visual acuity to ≤20/30.

RESULTS

After 8 years of treatment and follow-up, a total of 193 incident cases of visually significant AMD were documented. There were 96 cases in the vitamin E group and 97 in the placebo group (hazard ratio [HR], 1.03; 95% confidence interval [CI], 0.78-1.37). For vitamin C, there were 97 cases in the active group and 96 in the placebo group (HR, 0.99; 95% CI, 0.75-1.31).

CONCLUSIONS

In a large-scale, randomized trial of United States male physicians, alternate-day use of 400 IU of vitamin E and/or daily use of 500 mg of vitamin C for 8 years had no appreciable beneficial or harmful effect on risk of incident diagnosis of AMD.

Nutritional modulation of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly worldwide. It affects 30-50 million individuals and clinical hallmarks of AMD are observed in at least one third of persons over the age of 75 in industrialized countries (Gehrs et al., 2006). Costs associated with AMD are in excess of $340 billion US (American-Health-Assistance-Foundation, 2012). The majority of AMD patients in the United States are not eligible for clinical treatments (Biarnes et al., 2011; Klein et al., 2011). Preventive interventions through dietary modulation are attractive strategies because many studies suggest a benefit of micro- and macronutrients with respect to AMD, as well as other age-related debilities, and with few, if any, adverse effects (Chiu, 2011). Preservation of vision would enhance quality of life for millions of elderly people, and alleviate the personal and public health financial burden of AMD (Frick et al., 2007; Wood et al., 2011). Observational studies indicate that maintaining adequate levels of omega-3 fatty acids (i.e. with 2 servings/week of fish) or a low glycemic index diet may be particularly beneficial for early AMD and that higher levels of carotenoids may be protective, most probably, against neovascular AMD. Intervention trials are needed to better understand the full effect of these nutrients and/or combinations of nutrients on retinal health. Analyses that describe effects of a nutrient on onset and/or progress of AMD are valuable because they indicate the value of a nutrient to arrest AMD at the early stages. This comprehensive summary provides essential information about the value of nutrients with regard to diminishing risk for onset or progress of AMD and can serve as a guide until data from ongoing intervention trials are available.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Our systematic review has demonstrated that antioxidant supplements may increase mortality. We have now updated this review.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements for prevention of mortality in adults.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index Expanded, and Conference Proceedings Citation Index-Science to February 2011. We scanned bibliographies of relevant publications and asked pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Random-effects and fixed-effect model meta-analyses were conducted. Risk of bias was considered in order to minimise the risk of systematic errors. Trial sequential analyses were conducted to minimise the risk of random errors. Random-effects model meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Seventy-eight randomised trials with 296,707 participants were included. Fifty-six trials including 244,056 participants had low risk of bias. Twenty-six trials included 215,900 healthy participants. Fifty-two trials included 80,807 participants with various diseases in a stable phase. The mean age was 63 years (range 18 to 103 years). The mean proportion of women was 46%. Of the 78 trials, 46 used the parallel-group design, 30 the factorial design, and 2 the cross-over design. All antioxidants were administered orally, either alone or in combination with vitamins, minerals, or other interventions. The duration of supplementation varied from 28 days to 12 years (mean duration 3 years; median duration 2 years). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects model meta-analysis (21,484 dead/183,749 (11.7%) versus 11,479 dead/112,958 (10.2%); 78 trials, relative risk (RR) 1.02, 95% confidence interval (CI) 0.98 to 1.05) but significantly increased mortality in a fixed-effect model (RR 1.03, 95% CI 1.01 to 1.05). Heterogeneity was low with an I(2)- of 12%. In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. Meta-regression analysis did not find a significant difference in the estimated intervention effect in the primary prevention and the secondary prevention trials. In the 56 trials with a low risk of bias, the antioxidant supplements significantly increased mortality (18,833 dead/146,320 (12.9%) versus 10,320 dead/97,736 (10.6%); RR 1.04, 95% CI 1.01 to 1.07). This effect was confirmed by trial sequential analysis. Excluding factorial trials with potential confounding showed that 38 trials with low risk of bias demonstrated a significant increase in mortality (2822 dead/26,903 (10.5%) versus 2473 dead/26,052 (9.5%); RR 1.10, 95% CI 1.05 to 1.15). In trials with low risk of bias, beta-carotene (13,202 dead/96,003 (13.8%) versus 8556 dead/77,003 (11.1%); 26 trials, RR 1.05, 95% CI 1.01 to 1.09) and vitamin E (11,689 dead/97,523 (12.0%) versus 7561 dead/73,721 (10.3%); 46 trials, RR 1.03, 95% CI 1.00 to 1.05) significantly increased mortality, whereas vitamin A (3444 dead/24,596 (14.0%) versus 2249 dead/16,548 (13.6%); 12 trials, RR 1.07, 95% CI 0.97 to 1.18), vitamin C (3637 dead/36,659 (9.9%) versus 2717 dead/29,283 (9.3%); 29 trials, RR 1.02, 95% CI 0.98 to 1.07), and selenium (2670 dead/39,779 (6.7%) versus 1468 dead/22,961 (6.4%); 17 trials, RR 0.97, 95% CI 0.91 to 1.03) did not significantly affect mortality. In univariate meta-regression analysis, the dose of vitamin A was significantly associated with increased mortality (RR 1.0006, 95% CI 1.0002 to 1.001, P = 0.002).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.

Dietary supplementation: effects on visual performance and occurrence of AMD and cataracts

OBJECTIVE

To evaluate results of studies that have provided information regarding the effects of dietary supplementation on visual performance, development and progression of age-related macular degeneration (AMD), and risk for cataracts.

RESEARCH DESIGN AND METHODS

Studies with information about the effects of dietary supplementation were identified via PubMed searches that combined (in separate searches) the terms 'supplement' OR 'supplementation' OR 'diet' AND 'cataract' or 'macular degeneration' or 'visual' OR 'vision'. Additional references concerned with biologic effects of specific agents, measurement of visual function, and the etiology and epidemiology of cataracts and AMD were identified on the basis of PubMed conventional literature searches.

RESULTS

Studies of the effects of dietary supplementation, primarily with preparations including lutein and zeaxanthin, have demonstrated improvements in contrast sensitivity and visual performance under glare conditions that, in some studies, have been correlated with effects of treatment on macular pigment optical density. Results from both observational and prospective interventional studies generally support the conclusion that dietary supplements including these xanthophylls significantly decrease the occurrence of AMD and the development of nuclear lens opacities. However, there is variability in results regarding effects of dietary supplementation that may be related to limitations of long-term observational or interventional studies and which cannot be easily controlled or which may also be related in some studies to other important, yet unrecorded, diet- and lifestyle-related factors that are capable of influencing the risks for AMD and/or cataracts.

CONCLUSIONS

The multiple benefits of dietary supplementation support the development and use of these preparations to promote optimal visual function and decrease risk for AMD and cataracts. Increasing understanding of the optimal approach to supplementation will depend upon results from interventional studies that also carefully evaluate and analyze well-established factors for these two conditions.

Vitamin E and age-related macular degeneration in a randomized trial of women

OBJECTIVE

To test whether alternate day vitamin E affects the incidence of age-related macular degeneration (AMD) in a large-scale randomized trial of women.

DESIGN

Randomized, double-masked, placebo-controlled trial.

PARTICIPANTS

Thirty-nine thousand eight hundred seventy-six apparently healthy female health professionals aged 45 years or older.

INTERVENTION

Participants were assigned randomly to receive either 600 IU of natural-source vitamin E on alternate days or placebo.

MAIN OUTCOME MEASURES

Incident AMD responsible for a reduction in best-corrected visual acuity to 20/30 or worse based on self-report confirmed by medical record review.

RESULTS

After 10 years of treatment and follow-up, there were 117 cases of AMD in the vitamin E group and 128 cases in the placebo group (relative risk, 0.93; 95% confidence interval, 0.72-1.19).

CONCLUSIONS

In a large-scale randomized trial of female health professionals, long-term alternate-day use of 600 IU of natural-source vitamin E had no large beneficial or harmful effect on risk of AMD.

Smoking history and the incidence of age-related macular degeneration--results from the Muenster Aging and Retina Study (MARS) cohort and systematic review and meta-analysis of observational longitudinal studies

To compare the association of smoking with age-related macular degeneration (AMD) in the Muenster Aging and Retina Study (MARS) cohort with current evidence. Adjusted risk ratios for incident AMD in MARS were compared with findings of a systematic review and meta-analysis of observational prospective studies. 9.6% of MARS participants progressed to AMD over a median of 30.9 months. In MARS the adjusted risk ratio in current versus never smokers was 3.25 (95% confidence interval [1.50-7.06]), and 1.28 [0.70-2.33] in former smokers versus never smokers. The meta-analysis of previous studies showed a pooled adjusted risk ratio of 2.51 [1.09-5.76] in current versus never smokers. Inclusion of the MARS findings removed between-study heterogeneity and accentuated the pooled adjusted risk ratio for current smokers to 2.75 [1.52-4.98]. Specific analyses in MARS revealed a protective effect for time since smoking cessation in former smokers with an adjusted risk ratio=0.50 [0.29-0.89] per log(year). Current smoking nearly triples AMD incidence, while smoking cessation lowers AMD incidence in a non-linear fashion even in the elderly.

Dietary glycemic index and the risk of age-related macular degeneration

BACKGROUND

Dietary factors are known risk factors for age-related macular degeneration (AMD) -- the leading cause of visual loss among persons aged > or =65 y. High-glycemic-index diets have been hypothesized as a risk factor for AMD, but prospective data are unavailable.

OBJECTIVE

The objective was to examine the association between dietary glycemic index and the 10-y incidence of AMD in the Blue Mountain Eye Study population.

DESIGN

This was a population-based cohort study with 3,654 participants (> or =49 y) examined at baseline (1992-1994); 2,335 patients were reexamined after 5 y and 1952 after 10 y. The Wisconsin System was used to grade 10-y incident early and late AMD from retinal photographs. A food-frequency questionnaire was used to collect dietary information at baseline, and an Australian database was used to calculate the mean glycemic index.

RESULTS

Over 10 y, 208 of 1,810 persons (cumulative incidence: 14.1%) developed early AMD. After age, smoking, other risk factors, and dietary constituents were adjusted for, a higher mean dietary glycemic index was associated with an increased 10-y risk of early AMD in a comparison of quartiles 1 and 4 [relative risk (RR): 1.77; 95% CI: 1.13, 2.78; P for trend = 0.03]. Conversely, a greater consumption of cereal fiber (RR: 0.68; 95% CI: 0.44, 1.04; P for trend = 0.05) and breads and cereals (predominantly lower glycemic index foods such as oatmeal) (RR: 0.67; 95% CI: 0.44, 1.02; P for trend = 0.03) was associated with a reduced risk of incident early AMD. No relation was observed with late AMD.

CONCLUSIONS

A high-glycemic-index diet is a risk factor for early AMD -- the recognized precursor of sight-threatening late AMD. Low-glycemic-index foods such as oatmeal may protect against early AMD.

Antioxidant supplements for preventing gastrointestinal cancers

BACKGROUND

Oxidative stress may cause gastrointestinal cancers. The evidence on whether antioxidant supplements are effective in preventing gastrointestinal cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements in preventing gastrointestinal cancers.

SEARCH STRATEGY

We identified trials through the trials registers of the four Cochrane Review Groups on gastrointestinal diseases, The Cochrane Central Register of Controlled Trials in The Cochrane Library (Issue 2, 2007), MEDLINE, EMBASE, LILACS, SCI-EXPANDED, and The Chinese Biomedical Database from inception to October 2007. We scanned reference lists and contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing antioxidant supplements to placebo/no intervention examining occurrence of gastrointestinal cancers.

DATA COLLECTION AND ANALYSIS

Two authors (GB and DN) independently selected trials for inclusion and extracted data. Outcome measures were gastrointestinal cancers, overall mortality, and adverse effects. Outcomes were reported as relative risks (RR) with 95% confidence interval (CI) based on random-effects and fixed-effect model meta-analysis. Meta-regression assessed the effect of covariates across the trials.

MAIN RESULTS

We identified 20 randomised trials (211,818 participants), assessing beta-carotene (12 trials), vitamin A (4 trials), vitamin C (8 trials), vitamin E (10 trials), and selenium (9 trials). Trials quality was generally high. Heterogeneity was low to moderate. Antioxidant supplements were without significant effects on gastrointestinal cancers (RR 0.94, 95% CI 0.83 to 1.06). However, there was significant heterogeneity (I(2) = 54.0%, P = 0.003). The heterogeneity may have been explained by bias risk (low-bias risk trials RR 1.04, 95% CI 0.96 to 1.13 compared to high-bias risk trials RR 0.59, 95% CI 0.43 to 0.80; test of interaction P < 0.0005), and type of antioxidant supplement (beta-carotene potentially increasing and selenium potentially decreasing cancer risk). The antioxidant supplements had no significant effects on mortality in a random-effects model meta-analysis (RR 1.02, 95% CI 0.97 to 1.07, I(2) = 53.5%), but significantly increased mortality in a fixed-effect model meta-analysis (RR 1.04, 95% CI 1.02 to 1.07). Beta-carotene in combination with vitamin A (RR 1.16, 95% CI 1.09 to 1.23) and vitamin E (RR 1.06, 95% CI 1.02 to 1.11) significantly increased mortality. Increased yellowing of the skin and belching were non-serious adverse effects of beta-carotene. In five trials (four with high risk of bias), selenium seemed to show significant beneficial effect on gastrointestinal cancer occurrence (RR 0.59, 95% CI 0.46 to 0.75, I(2) = 0%).

AUTHORS' CONCLUSIONS

We could not find convincing evidence that antioxidant supplements prevent gastrointestinal cancers. On the contrary, antioxidant supplements seem to increase overall mortality. The potential cancer preventive effect of selenium should be tested in adequately conducted randomised trials.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Animal and physiological research as well as observational studies suggest that antioxidant supplements may improve survival.

OBJECTIVES

To assess the effect of antioxidant supplements on mortality in primary or secondary prevention randomised clinical trials.

SEARCH STRATEGY

We searched The Cochrane Library (Issue 3, 2005), MEDLINE (1966 to October 2005), EMBASE (1985 to October 2005), and the Science Citation Index Expanded (1945 to October 2005). We scanned bibliographies of relevant publications and wrote to pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention. Included participants were either healthy (primary prevention trials) or had any disease (secondary prevention trials).

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Trials with adequate randomisation, blinding, and follow-up were classified as having a low risk of bias. Random-effects and fixed-effect meta-analyses were performed. Random-effects meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Sixty-seven randomised trials with 232,550 participants were included. Forty-seven trials including 180,938 participants had low risk of bias. Twenty-one trials included 164,439 healthy participants. Forty-six trials included 68111 participants with various diseases (gastrointestinal, cardiovascular, neurological, ocular, dermatological, rheumatoid, renal, endocrinological, or unspecified). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects meta-analysis (relative risk [RR] 1.02, 95% confidence interval [CI] 0.99 to 1.06), but significantly increased mortality in a fixed-effect model (RR 1.04, 95% CI 1.02 to 1.06). In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. In the trials with a low risk of bias, the antioxidant supplements significantly increased mortality (RR 1.05, 95% CI 1.02 to 1.08). When the different antioxidants were assessed separately, analyses including trials with a low risk of bias and excluding selenium trials found significantly increased mortality by vitamin A (RR 1.16, 95% CI 1.10 to 1.24), beta-carotene (RR 1.07, 95% CI 1.02 to 1.11), and vitamin E (RR 1.04, 95% CI 1.01 to 1.07), but no significant detrimental effect of vitamin C (RR 1.06, 95% CI 0.94 to 1.20). Low-bias risk trials on selenium found no significant effect on mortality (RR 0.91, 95% CI 0.76 to 1.09).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Vitamin A, beta-carotene, and vitamin E may increase mortality. Future randomised trials could evaluate the potential effects of vitamin C and selenium for primary and secondary prevention. Such trials should be closely monitored for potential harmful effects. Antioxidant supplements need to be considered medicinal products and should undergo sufficient evaluation before marketing.

Dietary Antioxidants and the Long-term Incidence of Age-Related Macular Degeneration

PURPOSE

To assess the relationship between baseline dietary and supplement intakes of antioxidants and the long-term risk of incident age-related macular degeneration (AMD).

DESIGN

Australian population-based cohort study.

PARTICIPANTS

Of 3654 baseline (1992-1994) participants initially 49 years of older, 2454 were reexamined after 5 years, 10 years, or both.

METHODS

Stereoscopic retinal photographs were graded using the Wisconsin Grading System. Data on potential risk factors were collected. Energy-adjusted intakes of alpha-carotene; beta-carotene; beta-cryptoxanthin; lutein and zeaxanthin; lycopene; vitamins A, C, and E; and iron and zinc were the study factors. Discrete logistic models assessed AMD risk. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated after adjusting for age, gender, smoking, and other risk factors.

MAIN OUTCOME MEASURES

Incident early, late, and any AMD.

RESULTS

For dietary lutein and zeaxanthin, participants in the top tertile of intake had a reduced risk of incident neovascular AMD (RR, 0.35; 95% CI, 0.13-0.92), and those with above median intakes had a reduced risk of indistinct soft or reticular drusen (RR, 0.66; 95% CI, 0.48-0.92). For total zinc intake the RR comparing the top decile intake with the remaining population was 0.56 (95% CI, 0.32-0.97) for any AMD and 0.54 (95% CI, 0.30-0.97) for early AMD. The highest compared with the lowest tertile of total beta-carotene intake predicted incident neovascular AMD (RR, 2.68; 95% CI, 1.03-6.96; P = 0.029, for trend). Similarly, beta-carotene intake from diet alone predicted neovascular AMD (RR comparing tertile 3 with tertile 1, 2.40; 95% CI, 0.98-5.91; P = 0.027, for trend). This association was evident in both ever and never smokers. Higher intakes of total vitamin E predicted late AMD (RR compared with the lowest tertile, 2.83; 95% CI, 1.28-6.23; and RR, 2.55; 95% CI, 1.14-5.70 for the middle and highest tertiles, respectively; P = 0.22, for trend).

CONCLUSIONS

In this population-based cohort study, higher dietary lutein and zeaxanthin intake reduced the risk of long-term incident AMD. This study confirmed the Age-Related Eye Disease Study finding of protective influences from zinc against AMD. Higher beta-carotene intake was associated with an increased risk of AMD.

Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration

BACKGROUND

Some observational studies have suggested that people who eat a diet rich in antioxidant vitamins (carotenoids, vitamins C and E) or minerals (selenium and zinc) may be less likely to develop age-related macular degeneration (AMD).

OBJECTIVES

The aim of this review was to examine the evidence as to whether or not taking vitamin or mineral supplements prevents the development of AMD.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) in The Cochrane Library (2007, Issue 3), MEDLINE (1966 to August 2007), SIGLE (1980 to 2005/03), EMBASE (1980 to August 2007), National Research Register (2007, Issue 3), AMED (1985 to January 2006) and PubMed (on 24 January 2006 covering last 60 days), reference lists of identified reports and the Science Citation Index. We contacted investigators and experts in the field for details of unpublished studies.

SELECTION CRITERIA

We included all randomised trials comparing an antioxidant vitamin and/or mineral supplement (alone or in combination) to control. We included only studies where supplementation had been given for at least one year.

DATA COLLECTION AND ANALYSIS

Both review authors independently extracted data and assessed trial quality. Data were pooled using a fixed-effect model.

MAIN RESULTS

Three randomised controlled trials were included in this review (23,099 people randomised). These trials investigated alpha-tocopherol and beta-carotene supplements. There was no evidence that antioxidant vitamin supplementation prevented or delayed the onset of AMD. The pooled risk ratio for any age-related maculopathy (ARM) was 1.04 (95% CI 0.92 to 1.18), for AMD (late ARM) was 1.03 (95% CI 0.74 to 1.43). Similar results were seen when the analyses were restricted to beta-carotene and alpha-tocopherol.

AUTHORS' CONCLUSIONS

There is no evidence to date that the general population should take antioxidant vitamin and mineral supplements to prevent or delay the onset of AMD. There are several large ongoing trials. People with AMD should see the related Cochrane review "Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration" written by the same author.

Macular pigment optical density in the elderly: findings in a large biracial Midsouth population sample

PURPOSE

To report the macular pigment optical density (MPOD) findings at 0.5 degrees of eccentricity from the fovea in elderly subjects participating in ARMA, a study of aging and age-related maculopathy (ARM) ancillary to the Health, Aging, and Body Composition (Health ABC) Study.

METHODS

MPOD was estimated with a heterochromatic flicker photometry (HFP) method in a large biracial population sample of normal 79.1 +/- 3.2-year-old adults living in the Midsouth (n = 222; 52% female; 23% black, 34% users of lutein-containing supplements). Within a modified testing protocol, subjects identified the lowest and the highest target intensity at which the flicker sensation disappeared, and the exact middle of this "no-flicker zone" was interpolated by the examiner.

RESULTS

An MPOD estimate was obtained successfully in 82% of the participants. The mean MPOD in our sample was 0.34 +/- 0.21 (SD). The interocular correlation was high (Pearson's r = 0.82). Compared with lutein supplement users, mean MPOD was 21% lower in nonusers (P = 0.013). MPOD was also 41% lower in blacks than in whites (P = 0.0002), even after adjustment for lutein supplement use. There were no differences in MPOD by gender, iris color, or history of smoking.

CONCLUSIONS

Older adults in the Midsouth appear to have average MPOD and interocular correlation comparable to those in previous studies. Lutein supplement use and white race correlated with higher MPOD. No evidence of an age-related decline in MPOD was seen in the sample. The HFP method for the measurement of MPOD is feasible in epidemiologic investigations of the elderly, the group at highest risk of ARM.

Beta carotene supplementation and age-related maculopathy in a randomized trial of US physicians

OBJECTIVE

To test whether beta carotene supplementation affects the incidence of age-related maculopathy (ARM) in a large-scale randomized trial.

DESIGN

Randomized, double-masked, placebo-controlled trial among 22 071 apparently healthy US male physicians aged 40 to 84 years. Participants were randomly assigned to receive beta carotene (50 mg every other day) or placebo. Main Outcome Measure Incident ARM responsible for a reduction in best-corrected visual acuity to 20/30 or worse.

RESULTS

After 12 years of treatment and follow-up, there were 162 cases of ARM in the beta carotene group vs 170 cases in the placebo group (relative risk [RR], 0.96; 95% confidence interval [CI], 0.78-1.20). The results were similar for the secondary end points of ARM with or without vision loss (275 vs 274 cases; RR, 1.01; 95% CI, 0.86-1.20) and advanced ARM (63 vs 66 cases; RR, 0.97; 95% CI, 0.69-1.37).

CONCLUSIONS

These randomized data relative to 12 years of treatment among a large population of apparently healthy men indicate that beta carotene supplementation has no beneficial or harmful effect on the incidence of ARM. Long-term supplemental use of beta carotene neither decreases nor increases the risk of ARM.

Multivitamin-multimineral supplements and eye disease: age-related macular degeneration and cataract

The prevalence and effects of age-related macular degeneration (AMD) and cataract are increasing dramatically as the proportion of elderly in our population continues to rise. A multivitamin-multimineral supplement with a combination of vitamin C, vitamin E, beta-carotene, and zinc (with cupric oxide) is recommended for AMD but not cataract. Weak support exists for multivitamins or other vitamin supplements from observational studies of cataract. The results of observational studies suggest that a healthy lifestyle with a diet containing foods rich in antioxidants, particularly lutein and zeaxanthin, as well as n-3 fatty acids, appears beneficial for AMD and possibly cataract. The Age-Related Eye Disease Study II will evaluate some of these additional nutrients as dietary supplements in a randomized trial.

Nutritional antioxidants and age-related cataract and maculopathy

Loss of vision is the second greatest, next to death, fear among the elderly. Age-related cataract (ARC) and maculopathy (ARM) are two major causes of blindness worldwide. There are several important reasons to study relationships between risk for ARC/ARM and nutrition: (1) because it is likely that the same nutritional practices that are associated with prolonged eye function will also be associated with delayed age-related compromises to other organs, and perhaps, aging in general, (2) surgical resources are insufficient to provide economic and safe surgeries for cataract and do not provide a cure for ARM, and (3) there will be considerable financial savings and improvements in quality of life if health rather than old age is extended, particularly given the rapidly growing elderly segment of our population. It is clear that oxidative stress is associated with compromises to the lens and retina. Recent literature indicates that antioxidants may ameliorate the risk for ARC and ARM. Given the association between oxidative damage and age-related eye debilities, it is not surprising that over 70 studies have attempted to relate antioxidant intake to risk for ARC and ARM. This article will review epidemiological literature about ARC and ARM with emphasis on roles for vitamins C and E and carotenoids. Since glycation and glycoxidation are major molecular insults which involve an oxidative stress component, we also review new literature that relates dietary carbohydrate intake to risk for ARC and ARM. To evaluate dietary effects as a whole, several studies have tried to relate dietary patterns to risk for ARC. We will also give some attention to this emerging research. While data from the observational studies generally support a protective role for antioxidants in foods or supplements, results from intervention trials are less encouraging with respect to limiting risk for ARC/ARM prevalence or progress through antioxidant supplementations, or maintaining higher levels of antioxidants either in diet or blood. Without more information it is difficult to parse these results. It would be worthwhile to determine why the various types of studies are not yielding similar results. However, there are many common insults and mechanistic compromises that are associated with aging, and proper nutrition early in life may address some of these compromises and provide for extended youthful function later in life. Indeed, proper nutrition, possibly including use of antioxidant supplements for the nutritionally impoverished, along with healthy life styles may provide the least costly and most practical means to delay ARC and ARM. Further studies should be devoted to identifying the most effective strategy to prevent or delay the development and progress of ARC/ARM. The efforts should include identifying the right nutrient(s), defining useful levels of the nutrient(s), and determining the age when the supplementation should begin.

Modifiable risk factors for age‐related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in Australia and other Western countries. As there is no cure for AMD, and treatments to stop its progression have met with limited success, there is an interest in identifying modifiable risk factors to prevent or slow disease progression. To date, smoking is the only proven modifiable risk factor for AMD. Other factors under study include (i) cardiovascular risk factors such as hypertension, body mass index, and atherosclerosis; and (ii) dietary risk factors including fat and antioxidant intake, but so far these studies have produced conflicting results. Dietary fat in relation to AMD has recently attracted media attention. Despite very limited work supporting an association between vegetable fat and AMD, widespread publicity advocating margarine as a cause of AMD and encouraging use of butter instead has caused confusion and anxiety among sufferers of AMD and the general public, as well as concern among health professionals. The antioxidant carotenoids--lutein and zeaxanthin--found in dark green or yellow vegetables exist in high concentrations in the macula and are hypothesised to play a protective role. Of nine controlled trials of supplementation with carotenoids and other antioxidants, three suggested that various combinations of antioxidants and carotenoids were protective. While a low-fat diet rich in dark green and yellow vegetables is advocated in general, any specific recommendations regarding certain fats or antioxidant supplementation and AMD are not based on consistent findings at this stage.

Tocotrienols: Vitamin E beyond tocopherols

In nature, eight substances have been found to have vitamin E activity: alpha-, beta-, gamma- and delta-tocopherol; and alpha-, beta-, gamma- and delta-tocotrienol. Yet, of all papers on vitamin E listed in PubMed less than 1% relate to tocotrienols. The abundance of alpha-tocopherol in the human body and the comparable efficiency of all vitamin E molecules as antioxidants, led biologists to neglect the non-tocopherol vitamin E molecules as topics for basic and clinical research. Recent developments warrant a serious reconsideration of this conventional wisdom. Tocotrienols possess powerful neuroprotective, anti-cancer and cholesterol lowering properties that are often not exhibited by tocopherols. Current developments in vitamin E research clearly indicate that members of the vitamin E family are not redundant with respect to their biological functions. alpha-Tocotrienol, gamma-tocopherol, and delta-tocotrienol have emerged as vitamin E molecules with functions in health and disease that are clearly distinct from that of alpha-tocopherol. At nanomolar concentration, alpha-tocotrienol, not alpha-tocopherol, prevents neurodegeneration. On a concentration basis, this finding represents the most potent of all biological functions exhibited by any natural vitamin E molecule. An expanding body of evidence support that members of the vitamin E family are functionally unique. In recognition of this fact, title claims in manuscripts should be limited to the specific form of vitamin E studied. For example, evidence for toxicity of a specific form of tocopherol in excess may not be used to conclude that high-dosage "vitamin E" supplementation may increase all-cause mortality. Such conclusion incorrectly implies that tocotrienols are toxic as well under conditions where tocotrienols were not even considered. The current state of knowledge warrants strategic investment into the lesser known forms of vitamin E. This will enable prudent selection of the appropriate vitamin E molecule for studies addressing a specific need.

Treatment of age-related macular degeneration

Age-related macular degeneration (AMD) is the greatest cause of legal blindness in the western world. Established treatments include argon laser photocoagulation of extrafoveal choroidal neovascularisation (CNV) and photodynamic therapy of selected sub-foveal CNV. Newer approaches are targeting the angiogenic pathway in CNV development. Currently, other treatment modalities, such as radiotherapy and transpupillary thermotherapy do not have a clear role to play. Surgical options are experimental and only available in some centres for selected patients. Prevention of AMD remains elusive. Dietary supplements may have a role, while statins and prophylactic laser photocoagulation of drusen remain experimental. This paper explains the principles behind these approaches.

Evidence for the use of nutritional supplements and herbal medicines in common eye diseases

PURPOSE

To provide a perspective by reviewing the evidence for the role of nutritional supplements and herbal medicines in the common causes of visual impairment.

DESIGN

Retrospective literature review.

METHODS

Published studies and information found in PubMed, International Bibliographic Information of Dietary Supplements, and selected websites were reviewed for the role of nutritional and herbal medicines in the treatment of age-related macular degeneration, cataract, diabetic retinopathy, and glaucoma. The studies were evaluated systematically for their study design, study population, benefits, risks, biases, and criteria for the categorization of the level of evidence.

RESULTS

The available evidence does support the use of certain vitamins and minerals in patients with certain forms of age-related macular degeneration. For cataracts, the available evidence does not support these supplements to prevent or treat cataracts in healthy individuals. For diabetic retinopathy and glaucoma, the available evidence does not support the use of these supplements. In the category of herbal medicines, the available evidence does not support the use of herbal medicines for any of these ocular diseases.

CONCLUSION

Because of the widespread use of nutritional supplements and herbal medicines, ophthalmologists should be aware of their use so that they can inform patients properly when the supplements and herbal medicine are being used for eye disease.

Awareness of and compliance with recommended dietary supplement among age-related macular degeneration patients

BACKGROUND

The age-related eye disease study suggested that taking zinc and anti-oxidants supplements could reduce the progression of age-related macular degeneration (AMD). In Australia, the available supplement is Macu-Vision. The study aimed to assess the awareness of and compliance with taking this supplement and the public health implication.

METHODS

The fundus photograph database of patients aged 55 years and older at the ophthalmology department of a public teaching hospital in Adelaide, Australia was reviewed. In total, 125 patients with category 3 and 4 AMD were identified. A total of 100 patients participated in this cross-sectional study.

RESULTS

In total, 53% of participants were aware of the availability of the formulae available in Australia, 38% were taking the supplement and only 1% were taking the correct dose. Of those taking the supplement 95% (36/38) were taking half the recommended dosage. Among those who were aware of the supplement but not taking it, cost was the most common reason (31%). Another 31% were not taking it because of actual side-effects experienced, fear of potential side-effect and/or fear of interaction with other medications. There was no predictive factor for failing to take the formulae available in Australia among age, sex, smoking status, living arrangement and category of AMD.

CONCLUSIONS

Clinicians need to emphasize that the recommended dosage is twice that on the supplement label. If the trend demonstrated here of underutilizing the formulae available in Australia among public hospital patients continues, it is unlikely to have any major public health impact in similar settings in Australia.

Possible contraindications and adverse reactions associated with the use of ocular nutritional supplements

The role of oxidation in the development of age-related eye disease has prompted interest in the use of nutritional supplementation for prevention of onset and progression. Our aim is to highlight possible contraindications and adverse reactions of isolated or high dose ocular nutritional supplements. Web of Science and PubMed database searches were carried out, followed by a manual search of the bibliographies of retrieved articles. Vitamin A should be avoided in women who may become pregnant, in those with liver disease, and in people who drink heavily. Relationships have been found between vitamin A and reduced bone mineral density, and beta-carotene and increased risk of lung cancer in smoking males. Vitamin E and Ginkgo biloba have anticoagulant and anti-platelet effects respectively, and high doses are contraindicated in those being treated for vascular disorders. Those patients with contraindications or who are considered at risk of adverse reactions should be advised to seek specialist dietary advice via their medical practitioner.

AMD and micronutrient antioxidants

Age-related maculopathy (ARM) is a common clinical entity. The late-stage manifestations of ARM, which are known as age-related macular degeneration (AMD), have devastating consequences for vision. Various risk factors have been identified in the development of the condition, which are consistent with the premise that oxidative stress plays an important role in its pathogenesis. Thus, the possibility that antioxidant balance can be manipulated through diet or supplementation has created much interest. Associations between diet and nutrition and the clinical features of ARM have been described. Scrutiny of the literature shows consistency in the report of notable reductions in serum micronutrients in wet AMD, however, the evidence for causation is still circumstantial. In this comprehensive review of the clinical literature, we have assessed the evidence for a link between diet and nutrition as risk factors for the development of ARM and AMD. All published case control, population-based, and interventional studies on ARM were examined. Although initial support appeared to be moderate and somewhat contradictory, the evidence that lifetime oxidative stress plays an important role in the development of ARM is now compelling. The positive outcomes in the Age-Related Eye Diseases Study, a major controlled clinical trial, have given hope that modulation of the antioxidant balance through supplementation can help prevent progression of ARM to AMD.

An ideal ocular nutritional supplement?

The role of nutritional supplementation in prevention of onset or progression of ocular disease is of interest to health care professionals and patients. The aim of this review is to identify those antioxidants most appropriate for inclusion in an ideal ocular nutritional supplement, suitable for those with a family history of glaucoma, cataract, or age-related macular disease, or lifestyle factors predisposing onset of these conditions, such as smoking, poor nutritional status, or high levels of sunlight exposure. It would also be suitable for those with early stages of age-related ocular disease. Literature searches were carried out on Web of Science and PubMed for articles relating to the use of nutrients in ocular disease. Those highlighted for possible inclusion were vitamins A, B, C and E, carotenoids beta-carotene, lutein, and zeaxanthin, minerals selenium and zinc, and the herb, Ginkgo biloba. Conflicting evidence is presented for vitamins A and E in prevention of ocular disease; these vitamins have roles in the production of rhodopsin and prevention of lipid peroxidation respectively. B vitamins have been linked with a reduced risk of cataract and studies have provided evidence supporting a protective role of vitamin C in cataract prevention. Beta-carotene is active in the prevention of free radical formation, but has been linked with an increased risk of lung cancer in smokers. Improvements in visual function in patients with age-related macular disease have been noted with lutein and zeaxanthin supplementation. Selenium has been linked with a reduced risk of cataract and activates the antioxidant enzyme glutathione peroxidase, protecting cell membranes from oxidative damage while zinc, although an essential component of antioxidant enzymes, has been highlighted for risk of adverse effects. As well as reducing platelet aggregation and increasing vasodilation, Gingko biloba has been linked with improvements in pre-existing field damage in some patients with normal tension glaucoma. We advocate that vitamins C and E, and lutein/zeaxanthin should be included in our theoretically ideal ocular nutritional supplement.

Antioxidant supplements for preventing gastrointestinal cancers

BACKGROUND

Oxidative stress may cause gastrointestinal cancers. The evidence on whether antioxidant supplements are effective in preventing gastrointestinal cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements in preventing gastrointestinal cancers.

SEARCH STRATEGY

We identified trials through the trials registers of the four Cochrane Review Groups on gastrointestinal diseases, The Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 1, 2003), MEDLINE, EMBASE, LILACS, and SCI-EXPANDED from inception to February 2003, and The Chinese Biomedical Database (March 2003). We scanned reference lists and contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing antioxidant supplements to placebo/no intervention examining the incidence of gastrointestinal cancers.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials for inclusion and extracted data. The outcome measures were incidence of gastrointestinal cancers, overall mortality, and adverse events. Outcomes were reported as relative risks (RR) with 95% confidence interval (CI) based on fixed and random effects meta-analyses.

MAIN RESULTS

We identified 14 randomised trials (170,525 participants), assessing beta-carotene (9 trials), vitamin A (4 trials), vitamin C (4 trials), vitamin E (5 trials), and selenium (6 trials). Trial quality was generally high. Heterogeneity was low to moderate. Neither the fixed effect (RR 0.96, 95% CI 0.88 to 1.04) nor random effects meta-analyses (RR 0.90, 95% CI 0.77 to 1.05) showed significant effects of supplementation with antioxidants on the incidences of gastrointestinal cancers. Among the seven high-quality trials reporting on mortality (131,727 participants), the fixed effect (RR 1.06, 95% CI 1.02 to 1.10) unlike the random effects meta-analysis (RR 1.06, 95% CI 0.98 to 1.15) showed that antioxidant supplements significantly increased mortality. Two low-quality trials (32,302 participants) found no significant effect of antioxidant supplementation on mortality. The difference between the mortality estimates in high- and low-quality trials was significant by test of interaction (z = 2.10, P = 0.04). Beta-carotene and vitamin A (RR 1.29, 95% CI 1.14 to 1.45) and beta-carotene and vitamin E (RR 1.10, 95% CI 1.01 to 1.20) significantly increased mortality, while beta-carotene alone only tended to do so (RR 1.05, 95% CI 0.99 to 1.11). Increased yellowing of the skin and belching were non-serious adverse effects of beta-carotene. In four trials (three with unclear/inadequate methodology), selenium showed significant beneficial effect on gastrointestinal cancer incidences.

REVIEWERS' CONCLUSIONS

We could not find evidence that antioxidant supplements prevent gastrointestinal cancers. On the contrary, they seem to increase overall mortality. The potential cancer preventive effect of selenium should be studied in adequately conducted randomised trials.

Hormones and Supplements: Do They Work?: Micronutrient Supplementation in Later Life: Limited Evidence for Benefit

The importance of attaining adequate macronutrient and micronutrient intake throughout the life course is essential for the maintenance of health. Claims have been made for the benefits of micronutrient supplementation in later life, and this review considers the strength of the evidence behind these claims focusing on studies with cardiovascular, cancer, eye health, immune, and cognitive end points. While observational data suggest the presence of a link between dietary micronutrient intake and health outcomes, evidence from large randomized controlled trials does not support the use of antioxidant vitamin or mineral supplements among well-nourished older populations. Moreover, there is evidence of possible adverse affects of micronutrient supplementation. In conclusion, the considerable enthusiasm for the use of micronutrient, especially antioxidant, supplements as anti-aging treatments or as treatments for specific diseases of later life is not supported by the currently available scientific literature.

Oxidative stress in childhood—in health and disease states

The accumulated information concerning the involvement of reactive oxygen species in many clinical disorders and disease states has led to the potential for intervention with antioxidants in these cases. There are currently numerous clinical trials involving administration of antioxidants in a variety of conditions such as coronary heart disease, cataract, cancer and neurodegenerative diseases. At the same time therapeutic trials aimed at preventing and delaying the aging process are also under investigation. Numerous disorders, in childhood, have also been linked to oxidative damage. The aim of this review is to provide an overview of oxidative stress, its mechanisms, targets and damage incurred, as pertaining specifically to clinical disorders during childhood. The defense mechanisms against oxidation; the enzymatic antioxidants and low molecular weight antioxidants are defined and a number of methods commonly used for evaluation of oxidative stress (methods for measurement of lipid and protein oxidation end products and methods for measurement of antioxidant defense capacity) described. Specific diseases related to oxidative stress in infancy and childhood are reviewed and the possible effect of nutritional intake on oxidative stress in the healthy child discussed. Other issues addressed include the ability of oxidative stress, as measured in plasma to reflect intratissue oxidation, the need for a simple laboratory method for characterization of an oxidative stress 'profile', the proposed role of oxidative stress in biological processes pertaining to growth and maturation and possible implications of unrestricted antioxidant supplementation.

Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye

The macular region of the primate retina is yellow in color due to the presence of the macular pigment, composed of two dietary xanthophylls, lutein and zeaxanthin, and another xanthophyll, meso-zeaxanthin. The latter is presumably formed from either lutein or zeaxanthin in the retina. By absorbing blue-light, the macular pigment protects the underlying photoreceptor cell layer from light damage, possibly initiated by the formation of reactive oxygen species during a photosensitized reaction. There is ample epidemiological evidence that the amount of macular pigment is inversely associated with the incidence of age-related macular degeneration, an irreversible process that is the major cause of blindness in the elderly. The macular pigment can be increased in primates by either increasing the intake of foods that are rich in lutein and zeaxanthin, such as dark-green leafy vegetables, or by supplementation with lutein or zeaxanthin. Although increasing the intake of lutein or zeaxanthin might prove to be protective against the development of age-related macular degeneration, a causative relationship has yet to be experimentally demonstrated.

Age-related macular degeneration and nutritional supplementation: a review of randomised controlled trials

Age-related macular degeneration (AMD) is the leading cause of severe vision loss in the developed world. The lack of effective treatment modalities, coupled with evidence supporting an oxidative pathogenesis, has increased interest in the potential preventative role of nutritional supplementation. This article reviews seven randomised controlled trials (RCTs) that have investigated the role of nutritional supplementation in AMD. Three of these trials reported a positive effect of nutritional supplementation on AMD; the Age-related eye study (AREDS), the Lutein Antioxidant Supplementation Trial (LAST), and the oral zinc trial by Newsome et al. (1988). However, the oral zinc trial by Newsome et al. (1988) was unlikely to detect any difference between treatments smaller than 72%, and the AREDS results were based on a subgroup of their study population. Lutein was considered for the AREDS formulation, but was not commercially available at that time. The findings of the LAST support a possible therapeutic role of lutein in AMD.

Long term dietary supplementation with zeaxanthin reduces photoreceptor death in light-damaged Japanese quail

The purpose of these studies was to evaluate the effects of light damage on Japanese quail whose retinal carotenoids had been experimentally manipulated through altered diets. The birds were raised 6 months on a commercial turkey diet (T), on a custom carotenoid-deficient diet (C-) containing 90% less carotenoid than the T diet, or on Z+ diet [the C- diet supplemented with natural zeaxanthin (35mgkg(-1) food)]. Equal numbers of males and females on each diet were exposed to nine intervals (1hr on, 2hr off) of 3200lux cool white light, then placed in the dark for 14hr before tissue collection. One retina was immediately frozen for HPLC analysis; the other eye was immediately fixed and processed for microscopy. There were no significant differences in the retinal carotenoid concentrations in hatch-mates that were and were not exposed to light. Supplementation resulted in three- to four-fold increases in retinal zeaxanthin and no change in retinal lutein or alpha-tocopherol, but the C- diet did not reduce the retinal carotenoid concentration in C- birds below that in T birds. The light-exposed retinas had significant numbers of apoptotic photoreceptors and photoreceptor ghosts. The number of ghosts was negatively correlated with the number of dying photoreceptors (P<0.05), and with retinal concentrations of zeaxanthin, alpha-tocopherol or gamma-tocopherol (P<0.04, 0.02, 0.04, respectively), but not with lutein. The number of dying photoreceptors was positively correlated with alpha-tocopherol and the sum alpha-tocopherol plus zeaxanthin (P<0.1; P0.04). Photoreceptor death was semi-quantitatively scored, assuming that ghosts were formed by removal of apoptotic photoreceptors with nuclear condensation. Stepwise regression produced a good model (r(2)=0.67;P <0.0001) for predicting death scores from retinal concentrations of zeaxanthin (Standard Coefficient=-0.76) and lutein (Standard Coefficients=+0.43). Absence of lutein in gender-specific analyses suggests lutein served as surrogate marker for gender. Combined analysis of the C- and T birds also demonstrated that dying photoreceptors were negatively correlated with retinal zeaxanthin. These data confirm our previous report that retinal carotenoids prevent photoreceptor cell death, and provide the first direct evidence that retinal zeaxanthin protects photoreceptors from light-induced death.

The role of aging, high fat diet and blue light exposure in an experimental mouse model for basal laminar deposit formation

We sought to investigate the role of aging as a susceptibility factor for the capacity of dietary fat intake to increase the development of subretinal deposits. Mice of various ages (2, 9 and 16 months) were fed a normal diet or a diet high in saturated and unsaturated fats for a total four and a half months. Some eyes were also exposed to non-phototoxic levels of blue-green light. The outer retina and choroid were examined by light and transmission electron microscopy, and the characteristics, frequency and severity of subRPE deposits was determined. Aged mice fed normal diets developed only very mild subretinal deposits. However, many eyes of mice aged 9 months or older at the time of initiation of diet developed frequent basal laminar deposits of moderate severity, and only 16 month old mice developed more severe deposits after exposure to blue-green light. Some eyes in this older group also developed endothelial invasion into Bruch's membrane. None of the eyes developed classic drusen or linear deposits. These observations demonstrate that age increases the capacity of dietary fat, especially in the presence of environmental light, to induce subRPE deposits.