Nutrition and eye disease of the elderly

Changes in carotenoid intake from fruit and vegetables in the Spanish population over the period 1964–2004

Objective

To assess changes in carotenoid intake based on the variations in the consumption of fresh fruit and vegetables in the Spanish population over the period 1964–2004.

Design

Consumption data of fresh fruit and vegetables from Family Budget Surveys carried out in 1964, 1980, 1990 and 2004. Consumption data (g per person per day) accounted for >90% of fruit and vegetable consumption at each time point. Quality controlled high-performance liquid chromatography analysis of the carotenoid composition of Spanish fruit and vegetable was used.

Subjects

Randomly selected, private households throughout Spain (20 800 households in 1964, 30 311 households in 1980, 21 155 households in 1990 and 6000 households in 2004). Twelve vegetables and 16 fruits representing 89–96% of the total consumption of fresh fruit and vegetables were used.

Results

Individual consumption of fruit and vegetables has changed over this period, altering the total and individual intake of carotenoids. Total carotenoid intake increased from 2.5 mg per person per day in 1964 to 4.1 mg per person per day in 1990, with a decrease to 3.3 mg per person per day in 2004. These increments are due to an increase in lycopene, α- and β-carotene, while a decrease in lutein and zeaxanthin is observed during the last decade. A continuous and consistent decrease in the relative contribution of lutein in the diet is observed over the period studied.

Conclusion

Although the consumption of fruit and vegetables is still consistent with a Mediterranean-type pattern, modifications in the consumption of individual fruits and vegetables have provoked changes in total and specific carotenoid intake with potential relevance in human health.

Assessment of carotenoid status and the relation to glycaemic control in type I diabetics: a follow-up study

OBJECTIVE

To assess the carotenoid status in young type I diabetic patients and its relationship to the glycaemic control of the disease.

DESIGN

A follow-up study.

SETTING

Hospital Universitario Puerta de Hierro, Health Area VI of Madrid (Spain).

SUBJECTS

Forty-seven type I diabetic patients, followed for 2.5 years.

INTERVENTIONS

Coinciding with physical examination and laboratory tests, serum levels of carotenoids were analysed by HPLC, and dietary intake of carotenoids was evaluated by a semiquantitative food frequency questionnaire and 3-day prospective dietary records.

RESULTS

In type I diabetic patients, average intake, serum levels and correlations between diet and serum levels of carotenoids were comparable to those in reference non-diabetic groups. Between-subjects seasonal variations were observed for beta-cryptoxanthin intake and serum levels (higher in winter) and serum lycopene (higher in summer). Significant within-subjects seasonal changes were shown for dietary and serum beta-cryptoxanthin and serum beta-carotene. Serum carotenoids were unrelated to glycaemic control markers. Subjects with clinically acceptable glycaemic control showed lower lycopene intake than those with unacceptable control. Intake of carotenoids did not explain variance in insulin dose, fasting glycaemia, fructosamine or HbA1c. With the exception of lycopene, serum carotenoids were predicted by dietary intake, but in no case by fasting glycaemia, HbA1c or fructosamine.

CONCLUSION

In type I diabetic patients, serum carotenoid concentrations and their variance are determined by dietary intake patterns, and are unrelated to the glycaemic control of the disease, as assessed by biochemical markers.

Assessment of Aqueous Humor Zinc Status in Human Age-Related Cataract

Age-related cataract is an ever-increasing health problem among the elderly population worldwide. In recent years, there has been speculation that the levels of micronutrients in ocular tissue may play a role in the pathogenesis of cataract, especially zinc, since it is found in high concentrations in the eye tissues, including the aqueous humor. 44 subjects diagnosed with cataract were chosen for study and matched with 21 healthy controls to determine the concentration of zinc in aqueous humor. The findings revealed that a significantly higher concentration of zinc was present in the aqueous humor of our study population compared to controls (p < 0.001). These findings, in agreement with several previous studies, amplify the need for further investigation to determine if these higher levels are in actuality a consequence of the disease or a factor in the formation of cataract.

Carotenoids, retinol and tocopherols in blood: comparability between serum and plasma (Li-heparin) values

OBJECTIVE

To assess the comparability of concentrations of retinol, alpha- and gamma-tocopherols and individual carotenoids in serum and (Li-hep) plasma over a wide range of concentrations.

MATERIAL AND METHODS

One hundred sixty-six pairs of samples (serum and lithium-heparin plasma) were analyzed by a quality-controlled HPLC method. Means and 95% confidence intervals, differences, interchangeability and the degree of agreement (Bland-Altman plot) were calculated.

RESULTS

Distribution of all analytes in the two matrices are comparable and interchangeable with minor quantitative adjustments. Within the range of concentrations assessed, the degree of agreement was high, although some differences were observed for minor components with greater analytical imprecision.

CONCLUSIONS

The results indicate an acceptable degree of agreement using either of the two matrices for the analytes assessed except possibly for minor blood components. For retinol and alpha-tocopherol, the comparability and interchangeability of results below the cut-off points for inadequacy need further confirmation.

Nutrition Surveys in Burma and Northeast Brazil

Participation of the author in the Interdepartmental Committee on Nutrition for National Defense sponsored nutrition surveys of Burma and northeast Brazil is described. These surveys not only collected important data on nutritional status but also guided the subsequent research interests of the author. The Brazil survey results contributed to the creation of legislation that mandated the addition of water-dispersible vitamin A to skimmed-milk powder products. This additive has greatly diminished the likelihood of vitamin A deficiency syndrome occurring in children after famine relief efforts.

Carotenoid Depletion in Serum of Young Type-1 Diabetics Fed Low-Carotenoid Diets

BACKGROUND/AIMS

Type-1 diabetics have been considered to be at risk for increased oxidative stress which has been implicated in the development of long-term diabetes complications. Evidence suggests that antioxidant activity may be an important mechanism by which carotenoids could confer protection in human health. Our aim was to compare the serum carotenoid depletion rate in type-1 diabetics and control subjects consuming low-carotenoid diets.

METHODS

Ten type-1 diabetics and 8 controls followed a very low-carotenoid diet for 21 days. Dietary intake was recorded daily and fasting blood samples collected at baseline and after 1, 2, 3, 6, 11, 15, 16, 17, and 21 days. Individual carotenoids in serum were analyzed by a validated HPLC method.

RESULTS

In both groups, carotenoid intake was less than 5% of the season-adjusted carotenoid reference intake. These diets resulted in decreased serum carotenoid levels in both groups, although depletion curves, final mean concentrations and the estimated half-life of carotenoids in serum revealed no differences between type-1 diabetics and controls. Levels of other minor serum carotenoids, cis-isomers and keto-carotenoids, also decreased whereas serum retinol and alpha- and gamma-tocopherol did not change during the study.

CONCLUSION

Upon a low-carotenoid intake, the depletion rate of carotenoids in serum in young type-1 diabetics does not differ from that observed in matched related controls.

Lutein, but not alpha-tocopherol, supplementation improves visual function in patients with age-related cataracts: a 2-y double-blind, placebo-controlled pilot study

OBJECTIVE

We investigated the effect of long-term antioxidant supplementation (lutein and alpha-tocopherol) on serum levels and visual performance in patients with cataracts.

METHODS

Seventeen patients clinically diagnosed with age-related cataracts were randomized in a double-blind study involving dietary supplementation with lutein (15 mg; n = 5), alpha-tocopherol (100 mg; n = 6), or placebo (n = 6), three times a week for up to 2 y. Serum carotenoid and tocopherol concentrations were determined with quality-controlled high-performance liquid chromatography, and visual performance (visual acuity and glare sensitivity) and biochemical and hematologic indexes were monitored every 3 mo throughout the study. Changes in these parameters were assessed by General Linear Model (GLM) repeated measures analysis.

RESULTS

Serum concentrations of lutein and alpha-tocopherol increased with supplementation, although statistical significance was reached only in the lutein group. Visual performance (visual acuity and glare sensitivity) improved in the lutein group, whereas there was a trend toward the maintenance of and decrease in visual acuity with alpha-tocopherol and placebo supplementation, respectively. No significant side effects or changes in biochemical or hematologic profiles were observed in any of the subjects during the study.

CONCLUSIONS

Visual function in patients with age-related cataracts who received the lutein supplements improved, suggesting that a higher intake of lutein, through lutein-rich fruit and vegetables or supplements, may have beneficial effects on the visual performance of people with age-related cataracts.

Carotenoids: separation methods applicable to biological samples

Epidemiologic and clinical studies have shown that a high intake of vegetables and fruit, with consequently high intakes and circulating concentrations of carotenoids, is associated with reduced risk of cardiovascular and other chronic diseases. The antioxidant properties of carotenoids are thought to contribute to these effects. The analysis of carotenoids in plasma, foods and tissues has thus become of interest in studies examining the role of diet in chronic disease prevention and management. High-performance liquid chromatography with ultra-violet or photodiode array detection is most often employed in routine use. We review these and other current methods for carotenoid analysis and information on sample stability relevant to epidemiological studies. The carotenoids remain an important and intriguing subject of study, with relevance to prevention of several important "lifestyle-related" diseases. Research into their physiological functions and their use as dietary markers requires sensitive, accurate and precise measurement. Further advances in these methodological areas will contribute to basic, clinical and public health research into the significance of carotenoid compounds in disease prevention.

Quercetin metabolism in the lens: role in inhibition of hydrogen peroxide induced cataract

Oxidative stress is implicated in the initiation of maturity onset cataract. Quercetin, a major flavonol in the diet, inhibits lens opacification in a lens organ culture oxidative model of cataract. The aim of this research was to investigate the metabolism of quercetin in the lens and show how its metabolism affects the ability to prevent oxidation-induced opacity. The LOCH model (Free Radical Biology & Medicine 26:639; 1999) was employed, using rat lenses to investigate the effects of quercetin and metabolites on hydrogen peroxide-induced opacification. High-performance liquid chromatography analysis showed that the intact rat lens is capable of converting quercetin aglycone to 3'-O-methyl quercetin (isorhamnetin). Over a 6 h culture period no further metabolism of the 3'-O-methyl quercetin occurred. Loss of quercetin in the lens was accounted for by the increase in 3'-O-methyl quercetin. Incubation with 3,5-dinitrocatechol (10 microM), a catechol-O-methyltransferase (COMT) inhibitor, prevented the conversion of quercetin to 3'-O-methyl quercetin. The presence of both membrane-bound and soluble COMT was confirmed by immunoblotting. The results demonstrate that in the rat lens COMT methylates quercetin and that the product accumulates within the lens. Quercetin (10 microM) and 3'-O-methyl quercetin (10 microM) both inhibited hydrogen peroxide- (500 microM) induced sodium and calcium influx and lens opacification. Incubation of lenses with quercetin in the presence of COMT inhibitor revealed that the efficacy of quercetin is not dependent on its metabolism to 3'-O-methyl quercetin. The results indicate dietary quercetin and metabolites are active in inhibiting oxidative damage in the lens and thus could play a role in prevention of cataract formation.

Can drugs or micronutrients prevent cataract?

Cataract is the major cause of blindness and of visual impairment worldwide, so its prevention is of the greatest importance. At present no drug therapy is licensed for use in the UK or the US, so the only treatment for cataract is by surgery, which is expensive and has adverse effects. This article reviews research on prevention of cataract by a variety of agents, including micronutrients as well as drugs. Benefits have been claimed for many compounds or mixtures and this review concentrates on those most extensively studied. Information on possible benefits of putative anticataract agents comes from a variety of approaches, from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients. Sorbitol-lowering drugs were the first to be examined systematically and progressed to clinical trials which were disappointing, and now the entire rationale for their use in prevention of cataract is questionable. Micronutrients showed little promise in animals but came to clinical trial in patients with cataract without the publication of any major benefit. Pantethine showed more promise in animal studies but the only clinical trial was abandoned early. A variety of laboratory and epidemiological evidence supports the benefits of aspirin-like drugs but there has been no trial specifically in patients with cataract. Add-on studies to trials of aspirin for other indications have not been encouraging. Research into other compounds is interesting but less advanced.

Quercetin inhibits hydrogen peroxide-induced oxidation of the rat lens

Cataract results from oxidative damage to the lens. The mechanism involves disruption of the redox system, membrane damage, proteolysis, protein aggregation and a loss of lens transparency. Diet has a significant impact on cataract development, but the individual dietary components responsible for this effect are not known. We show that low micromolar concentrations of the naturally-occurring flavonoid, quercetin, inhibit cataractogenesis in a rat lens organ cultured model exposed to the endogenous oxidant hydrogen peroxide. Other phenolic antioxidants, (+)epicatechin and chlorogenic acid, are much less effective. Quercetin was active both when incubated in the culture medium together with hydrogen peroxide, and was also active when the lenses were pre-treated with quercetin prior to oxidative insult. Quercetin protected the lens from calcium and sodium influx, which are early events leading to lens opacity, and this implies that the non-selective cation channel is protected by this phenolic. It did not, however, protect against formation of oxidized glutathione resulting from H2O2 treatment. The results demonstrate that quercetin helps to maintain lens transparency after an oxidative insult. The lens organ culture/hydrogen peroxide (LOCH) model is also suitable for examining the effect of other dietary antioxidants.

Lutein ester in serum after lutein supplementation in human subjects

Lutein, one of the major carotenoids present in serum, is also widely consumed by most populations. For the purpose of testing the potential health benefits of several carotenoids, lutein was supplied as part of an intervention trial to test whether the consumption of these food constituents reduces oxidative damage to human tissue components. Lutein from a natural source (15 mg/d as mixed ester forms) was supplied for 4 months to eighteen non-smoking, apparently healthy volunteers (nine men, nine women) aged 25-45 years. The serum carotenoid profile was analysed at baseline and monthly thereafter. On average, lutein concentrations increased 5-fold after the first month of supplementation (mean 1.34 (range 0.6-3.34) mumol/l). On reviewing the results, in those volunteers whose lutein levels surpassed 1.05 mumol/l (fourteen of seventeen), we tentatively identified lutein monopalmitate along with another unidentified ester (possibly from a monoketocarotenoid) in serum. Lutein levels returned to baseline values and ester forms were not present 3 months after supplementation was discontinued. Their concentrations did not correlate with, and represented less than 3% of, lutein levels achieved in serum. They were observed before development of, and despite the presence of, carotenodermia. To our knowledge, this is the first time xanthophyll esters have been described in human serum. In view of the fact that xanthophyll esters have not been previously reported in serum and chylomicrons, it seems unlikely that these ester forms would be a reflection of the contents of the capsule. They may indicate a 'ceiling effect' on or saturation of the transport capacity for xanthophylls, and may have been re-esterified in vivo because of the unusual dietary conditions. The determination of the physiological importance of this finding will require further investigation, although neither haematological nor biochemical changes were detected.

Vision testing in atrophic macular degeneration

PURPOSE

To determine the correlation between a group of vision tests in atrophic macular degeneration (AMD) in an office setting.

METHODS

Patients with documented vision loss from atrophic macular degeneration in one eye were invited to attend an eye clinic every three months for a series of six vision tests for their good eye followed by fundus photography. Modified contrast sensitivity, blue/yellow anomaloscopy, flicker fusion frequency, Amsler grid, and photostress recovery time were correlated with Snellen acuity using the Pearson correlation coefficient. The regression of the Snellen acuity on sex, age and the presence of disciform macular degeneration in the other eye was obtained using a general linear model.

RESULTS

The correlation with Snellen acuity result was low for all tests. It was highest for Amsler grid abnormality (r = -0.33345) and blue/yellow anomaloscopy matching range (r = -0.20742), where r denotes the correlation coefficient. Patient age was strongly correlated with Snellen results (P = 0.0001), but it was not significantly related to sex (P = 0.1187) or the presence of disciform macular degeneration in the other eye (P = 0.9989). The photostress recovery time showed enormous inter-visit variations and poor correlation with Snellen acuity (P = 0.0526).

CONCLUSIONS

The course of AMD is routinely assessed by Snellen acuity and any of several additional tests. When employing a test battery in an office setting, a clinician needs to know the relative utility and correlation between the tests at his disposal. Of the tests used in this study, the Amsler grid was the most useful addition to the Snellen acuity at all stages of atrophic macular degeneration, and blue/yellow anomaloscopy was useful only in mild macular degeneration where Snellen acuity was 6/12 or better.

Antioxidants and age-related eye disease. Current and future perspectives

Oxidative mechanisms may play an important role in the pathogenesis of age-related eye disease, in particular cataract and macular degeneration, the two most important causes of visual impairment in older adults. For this reason, there is considerable interest in determining whether vitamins and trace minerals with antioxidant properties can be of benefit in preventing the onset or progression of disabling eye disease. Basic research studies have shown that antioxidants can protect against the cumulative effects of oxidative stress in animal models of cataract and macular degeneration. Data from observational epidemiological studies in humans, however, are inconclusive. While results from several studies, primarily cross-sectional and case-control, are compatible with a possible protective role for micronutrients in disease development, data for specific nutrients or specific disease types have often been inconsistent. Further, these observational studies are limited because of the inherent imprecision of dietary exposure data and the likely effects of uncontrolled confounding. Thus, reliable data regarding a potentially important benefit of vitamin supplementation in eye disease will emerge mainly from well-designed, large-scale, randomized trials.

[Antioxidative vitamins and cataracts in the elderly]

Senile cataract indicates the opacity of ocular lenses occurring in old and especially in very old people. Lens proteins are extremely long-living and often show oxidative damages. Aging and smoking appear to be the greatest risk factors for the development of lens opacities. The sufficient antioxidant protection of young lenses decreases with the aging process. Consequently, the importance of other protective factors increases. Nutritional factors, particularly vitamins with antioxidant properties, may influence the development of senile cataracts in the ocular lens. Meanwhile an association between the supply with vitamin C, E and beta-carotene and the risk of cataract development was demonstrated in animal studies and also in an increasing number of epidemiological studies. These epidemiological studies mainly support the hypothesis that higher vitamin intakes reduce the risk of developing cataracts in old age. The antioxidant properties of the named nutrients give a plausible explanation for the mechanism of cataractogenesis. On the basis of the present data definitive recommendation, necessary for cataract prevention can not yet be established. Some results seem to support higher recommendations. At the moment several large human intervention trials are carried out. Form these studies a further confirmation of the antioxidant hypothesis and of a dose-response-relationship are expected.