Carbohydrate intake and glycemic index in relation to the odds of early cortical and nuclear lens opacities

Proteostasis in aging-associated ocular disease

Vision impairment has devastating consequences for the quality of human life. The cells and tissues associated with the visual process must function throughout one's life span and maintain homeostasis despite exposure to a variety of insults. Maintenance of the proteome is termed proteostasis, and is vital for normal cellular functions, especially at an advanced age. Here we describe basic aspects of proteostasis, from protein synthesis and folding to degradation, and discuss the current status of the field with a particular focus on major age-related eye diseases: age-related macular degeneration, cataract, and glaucoma. Our intent is to allow vision scientists to determine where and how to harness the proteostatic machinery for extending functional homeostasis in the aging retina, lens, and trabecular meshwork. Several common themes have emerged despite these tissues having vastly different metabolisms. Continued exposure to insults, including chronic stress with advancing age, increases proteostatic burden and reduces the fidelity of the degradation machineries including the ubiquitin-proteasome and the autophagy-lysosome systems that recognize and remove damaged proteins. This "double jeopardy" results in an exponential accumulation of cytotoxic proteins with advancing age. We conclude with a discussion of the challenges in maintaining an appropriate balance of protein synthesis and degradation pathways, and suggest that harnessing proteostatic capacities should provide new opportunities to design interventions for attenuating age-related eye diseases before they limit sight.

‏Impact of Food Habit on Cataracts Development Among Adults in Aseer Region, Saudi Arabia: A Retrospective Study

Background: Cataracts are the main cause of visual impairment among the aging population, with a high impact on patients’ quality of life. It has been suggested that the antioxidant carotenoids lutein and zeaxanthin may play a role in cataract prevention. Recently, significant evidence has associated abnormal glucose metabolism with an increased likelihood of the development of cataracts.

Aim: The current study aims to assess the relationship between nutrition and cataracts among adults in the Aseer Region, Saudi Arabia.

Methods: A retrospective study was conducted targeting all accessible patients diagnosed with cataracts at Aseer Central Hospital during the period from August 8, 2019, to March 3, 2021, and at Khamis Mushayt General Hospital during the period from June 11, 2018, to March 3, 2021. Data were collected using a pre-structured data collection sheet that covered patients’ socio-demographic data, including age, gender, education, work type, and marital status. Also, the type of cataract diagnosed for the study patients was recorded with associated risk factors of cataracts, including chronic diseases, trauma, eye surgery, and family history. The last section covered patients’ dietary habits and frequency of dietary intake. 

Results: A total of 140 patients with cataracts who fulfilled the inclusion criteria were included in the study. Patients' ages ranged from 21 to 65 years, with a mean age of 54.2 ± 12.9 years old. Additionally, 12.1% of the study patients were smokers, 44.3% were diagnosed with hypertension, and 45% were diabetic, which was type 1 diabetes mellitus (T1DM) among 36.5% and type 2 diabetes mellitus (T2DM) among 52.4%. A family history of congenital cataracts was reported among 12.9%, and 12.9% had a history of eye trauma. Moreover, 37.1% of the study patients had vegetables once per week. Eating fruits or having juice was reported as once per week among 40% of the study patients and three times per week among 20%. Finally, 31.4% take nutritional supplements or vitamins.

Conclusion: There is currently an inquiry to endorse or exclude a specific diet or dietary intake that may reduce or even prevent the development and progression of cataracts. It appears beneficial for people to have some antioxidants in their daily food.

Exposure to Porphyromonas gingivalis and Modifiable Risk Factors Modulate Risk for Early Diabetic Retinopathy

Purpose

We hypothesized that exposure to Porphyromonas gingivalis (Pg) increases the risk for early diabetic retinopathy (DR) and that the risk can be modulated.

Methods

We identified 116 early DR cases, and 116 non-DR controls were selected randomly by frequency matching for age, sex, race, and education from the US Third National Health and Nutrition Examination Survey. DR was assessed using non-mydriatic fundus photographs and graded by trained graders using the Modified Airlie House Classification scheme and the Early Treatment for Diabetic Retinopathy Study severity scale. Serum Pg immunoglobulin G (IgG) antibody (Ab) was measured in enzyme-linked immunosorbent assay units. Logistic regression was used to relate serum Pg IgG Ab levels to the risk for early DR.

Results

Per tenfold increase in Pg IgG Ab levels, there was an over 60% increased risk for early DR (odds ratio = 1.64; 95% confidence interval, 1.36–1.97), and a linear trend was noted for the estimated probabilities of early DR at various Pg IgG Ab levels (P for trend = 0.0053). The analysis also suggested that moderate alcohol consumption (less than 12 drinks in the past 12 months; P for interaction = 0.0003) and maintaining a normal serum glycated hemoglobulin level (HbA1c ≤ 5.7%; P for interaction < 0.0001) helped reduce the Pg-related DR risk.

Conclusions

The increased Pg-related DR risk could be alleviated by managing alcohol consumption and maintaining a normal blood glucose level.

Translational Relevance

Findings from this study provide new directions for developing novel therapeutics and prevention strategies for DR.

Major dietary patterns in relation to age-related cataract

BACKGROUND AND AIMS

Dietary pattern (DP) may play an important role in the formation of Age-related cataract (ARC). The objective of the study was to investigate the association between DP and ARC.

METHODS

Participants (120 cases and 240 controls) aged 50-80 years were selected from the ophthalmology clinic of Urmia Imam Khomeini Educational Hospital in the Northwest of Iran by the simple random sampling method between 2017 and 2018. Participants in matched case-control study were free of diabetes, autoimmune diseases and cancer. Factor analysis method was used to identify the major DPs. The association between participants' DPs and ARC were evaluated using logistic regression analysis in SPSS20.

RESULTS

Four major DPs were found and nominated: "Unhealthy", "Healthy", "Salty foods" and "Mixed" patterns. In continues model the Unhealthy pattern was positively associated with the risk of ARC disease (odds ratio in adjusted model was 5.71; 95% CI: 3.68-8.87, P _trend< 0.001). The Healthy pattern was inversely associated with the ARC (odds ratio in adjusted model was 0.48; 95% CI: 0.34-0.67, P_trend = 0.02). The Salty foods pattern was associated with ARC (odds ratio in adjusted model was 1.45; 95% CI; 1.04-2.02, P_trend = 0.03). The association between ARC disease and Mixed patterns was not statistically significant.

CONCLUSION

The results indicate that Unhealthy and Salty foods patterns were associated with increased risk of ARC. Further prospective studies are needed to confirm such an association.

Impact of Diet on the Incidence of Cataract Surgery among Diabetic Patients: Findings from the 45 and Up Study

OBJECTIVE

To examine the impact of diet on the incidence of cataract surgery among the working-aged diabetic population in Australia.

METHODS

This cohort study was conducted among 8,752 participants with diabetes aged 45-65 years who were recruited to the 45 and Up Study from 2006 to 2016. The data was linked to the Medicare Benefits Schedule to obtain data on cataract surgery. Diabetes was defined as self-reported on questionnaire or diabetes medication history based on Pharmaceutical Benefits Scheme. Diet was assessed at baseline, using a self-administered questionnaire and healthy diet scores were calculated based on Australian Dietary Guidelines. Cox regression was used to evaluate the association between diet and the incidence of cataract surgery during the follow-up.

RESULTS

During a mean follow-up of 8.4 years (73,431 person-years), 914 diabetic participants underwent cataract surgery with a corresponding rate of 12.4 cases per 1,000 person-years. After adjusting for age and gender, the hazard ratios (HR) of cataract surgery for the highest compared to the lowest intake quintile of red meat and poultry were 1.24 (95% CI, 1.00-1.55) and 1.24 (95% CI, 1.02-1.51), respectively. Further adjustment for demographic, lifestyle and dietary factors resulted in no significant difference between cataract surgery risk and healthy diet scores or specific diet groups. In gender-stratified analyses, increasing consumption of red meat (HR for highest versus lowest quintile, 1.39; 95% CI, 1.00-1.93; P for trend = 0.01) and poultry (HR for highest versus lowest quintile, 1.40; 95% CI, 1.05-1.87; P for trend = 0.01) were associated with a higher risk of cataract surgery in women after adjustment of age, gender, income, education level, body mass index, hypertension, cardiovascular disease, family history of diabetes, diabetes duration, insulin use, lifestyle, and other dietary factors.

CONCLUSION

Higher consumption of red meat and poultry is related to an elevated risk of cataract surgery in the working-aged female population with diabetes.

Studies of advanced glycation end products and oxidation biomarkers for type 2 diabetes

Advanced glycation end products (AGEs) are formed upon nonenzymatic reactions of sugars or their metabolites with proteins and other cellular constituents. Many AGEs are long lived. Recent findings suggest that AGEs may predict diabetes and its complications and thus may warrant further study. The objective of this study was to assess the validity of our experimental procedures for measuring AGEs in stored blood sample and to conduct a pilot study for developing AGE biomarkers for diabetes and/or age-related changes of glucose metabolism. We conducted a reliability study of the samples and methods using liquid chromatography-tandem mass spectrometry (LC-MS)/MS assays for 10 AGEs (including methylglyoxal-derived hydroimidazolone (MG-H1), glucosepane (GSP) and two oxidation measures, in stored repository blood samples from the Nurses' Health Study and the Health Professionals Follow-up Study. We also analyzed data relating blood GSP levels to type 2 diabetes status in a case-control study (25 cases and 15 controls). Among the AGEs, GSP, and MG-H1 showed the highest reliability across the various measures: reliability in duplicate samples and stability with delayed processing and storage over 1-2 year period. Furthermore, plasma GSP was associated with older age (P = 0.04) and type 2 diabetes status (age-adjusted P = 0.0475). Our findings suggest that analysis of these AGEs may be developed as biomarkers for diabetes and/or age-related changes of glucose metabolism. © 2018 BioFactors, 44(3):281-288, 2018.

Healthy Eating Index in Patients With Cataract: A Case-Control Study

Background:

Nutritional factors play an important role in cataract disease and the healthy eating index (HEI) is a unique approach to study the relationships between diet and diseases.

Objectives:

The current study aimed to evaluate and compare healthy eating index among the patients with cataract and healthy individuals.

Patients and Methods:

This case-control study was conducted on 97 patients with cataract and 198 healthy people (as a control group) in Iran. Individuals were selected by the convenience sampling method and the food frequency questionnaire (FFQ) was completed for them. At first, HEI was calculated and then the HEI scores were compared in cataract patients and healthy individuals.

Results:

The analysis of FFQ showed that the scores of vegetables (7.81 v. 10), nutritional variation (5.5 v. 7) and sodium (2 v. 6) groups (P < 0.001) were significantly lower among the patients with cataract than the healthy individuals. Also this significant difference was observed in the scores of total HEI and fruits (respectively 73.26 v.79.30 and 7.1 v. 9.8) (P < 0.01). On the other hand, the scores of saturated fatty acids (10 v. 9; P = 0.02), total fat (8 v. 7; P = 0.004) and cereals (10 v. 10; P < 0.001) were higher among the patients with cataract than the healthy individuals. The comparison of dietary intake among all types of cataract shows that the scores of the meat group were significantly higher in the patients with nuclear cataract and mixed cataract than the ones with posterior cataract (respectively 9.4 v. 6.5 and 9 v. 6.5) (P = 0.02). In addition, after adjusting the confounding factors the results showed that the HEI high score was associated with reducing the risk of coming down with cataract (OR = 0.18, CI: 95%, P < 0.001, 0.08 - 0.41).

Conclusions:

The results of the current study suggest that increasing the quality of the diet calculated according to HEI can reduce the risk of coming down with cataract.

Dietary glycemic index, glycemic load and risk of age-related cataract extraction: a case-control study in Italy

PURPOSE

Although a role of glycemic index (GI) and glycemic load (GL) in age-related cataract development is plausible, a few studies, all conducted in USA or Australia, provided results on this issue. The aim of the present study was to provide new original data from a Mediterranean population.

METHODS

We analyzed data from an Italian case-control study including 761 cases with cataract extraction and 1,522 hospital controls, frequency-matched with cases by center, sex, and age. Multivariate odds ratios (ORs) for GI and GL intakes were obtained from logistic regression models after allowance for major confounding factors, including non carbohydrate energy intake, smoking, and diabetes.

RESULTS

The ORs of cataract extraction for the highest versus the lowest tertile were 1.20 (95% confidence interval, CI 0.91-1.57) for GI and 1.57 (95% CI 1.16-2.13) for GL, with a statistically significant trend in risk for GL (p < 0.01). Results were materially unchanged when diabetics were excluded from the analysis. No heterogeneity emerged across strata of sex, age, education, smoking habits and body mass index.

CONCLUSIONS

The present study supports a positive association between dietary GL and the risk of cataract extraction, independently from diabetes, and a lack of association for GI.

Relationship between dietary macronutrient intake and the risk of age-related cataract in middle-aged and elderly patients in northeast China

AIM

To examine the association between dietary macronutrient intake and the risk of age-related cataract (ARC) in middle-aged and elderly men.

METHODS

A hospital-based case-control study was conducted from December 2009 to November 2011. Cases (n=360) were patients with cataract aged 45-85 years old, and controls (n=360) were patients who had been admitted to the same hospital for diseases not related with cataract. All subjects were interviewed using a structured interviewer-administrated questionnaire that included information on socio-demographic characteristics, lifestyle habits and detailed medical history, simultaneously, the dietary intakes of nutrients were collected via a valid semi-quantitative food frequency questionnaire (FFQ). The odds ratios (OR) and corresponding 95% confidence intervals (CI) of three types of ARC were estimated using multiple logistic regression models.

RESULTS

After adjusting for multiple potential confounders, total dietary intake of carbohydrate was positively associated with cortical cataract, compared to controls in the lowest quartile, and the OR for cases in the highest quartile of intake was 2.471 (95%CI: 1.348-6.043, P=0.027). Higher dietary intakes of protein were protective for posterior subcapsular cataract (PSC) (OR=0.528, 95%CI: 0.148-0.869, P=0.023). Dietary fat intake was not associated with any type of cataract, however, participants in the highest quartile of polyunsaturated fatty acids intake had 2.7 times the risk of nuclear cataract as did those in the lowest quartile (OR=2.742, 95%CI: 1.790-4.200, P=0.033).

CONCLUSION

A high intake of carbohydrate and polyunsaturated fatty acid may increase the odds of cortical and nuclear cataract, respectively, whereas high intake of protein, especially animal protein, may protect against PSC cataract. It is possible that dietary changes of target population may reduce the risk of ARC.

Nutritional modulation of cataract

Lens opacification or cataract reduces vision in over 80 million people worldwide and blinds 18 million. These numbers will increase dramatically as both the size of the elderly demographic and the number of those with carbohydrate metabolism-related problems increase. Preventative measures for cataract are critical because the availability of cataract surgery in much of the world is insufficient. Epidemiologic literature suggests that the risk of cataract can be diminished by diets that are optimized for vitamin C, lutein/zeaxanthin, B vitamins, omega-3 fatty acids, multivitamins, and carbohydrates: recommended levels of micronutrients are salutary. The limited data from intervention trials provide some support for observational studies with regard to nuclear - but not other types of - cataracts. Presented here are the beneficial levels of nutrients in diets or blood and the total number of participants surveyed in epidemiologic studies since a previous review in 2007.

Diet and cataract: a case-control study

We conducted a case-control study to assess the association between diet and risk of cataract in Athens, Greece. Totals of 314 cases and 314 frequency-matched controls of both sexes, aged 45-85 years and attending the ophthalmology department of a major teaching hospital in Athens, Greece, were included in the study. All participants were interviewed using a semi-quantitative food-frequency questionnaire, covering the average frequency of consumption of about 120 food items. Analyses were conducted through multiple logistic regression. The analysis was carried out taking cataract as a general outcome (all types of cataract combined) and repeated by the specific type of cataract. We found significant inverse associations of cataract with dietary consumption of fish (OR = 0.69, p < 0.001), vegetables (OR = 0.47, p < 0.001), fruits (OR = 0.53, p < 0.001), and potatoes (OR = 0.76, p = 0.004), while consumption of meat was positively associated with cataract (OR = 1.46, p = 0.001). High intake of total fat (OR = 2.00, p < 0.001) and cholesterol (OR = 1.65, p < 0.001) increased the risk of cataract. There was a protective association between cataract risk and intake of carbohydrates (OR = 0.39, p < 0.001), carotene (OR = 0.56, p < 0.001), vitamins C and E (OR = 0.50, p < 0.001 and OR = 0.50, p < 0.001 respectively). We identified an association between the risk of cataract and several food groups and nutrients. Diets rich in fruits, vegetables, fish, pulses and starchy foods may protect against cataract. In addition, high intake of vitamins C and E and carotene with reduction of intake in total fat and cholesterol may be beneficial. Dietary advice along these lines may provide adequate public health guidelines for the delay of age-related cataract.

ILSI Brazil International Workshop on Functional Foods: a narrative review of the scientific evidence in the area of carbohydrates, microbiome, and health

To stimulate discussion around the topic of ‘carbohydrates’ and health, the Brazilian branch of the International Life Sciences Institute held the 11th International Functional Foods Workshop (1–2 December 2011) in which consolidated knowledge and recent scientific advances specific to the relationship between carbohydrates and health were presented. As part of this meeting, several key points related to dietary fiber, glycemic response, fructose, and impacts on satiety, cognition, mood, and gut microbiota were realized: 1) there is a need for global harmonization of a science-based fiber definition; 2) low-glycemic index foods can be used to modulate the postprandial glycemic response and may affect diabetes and cardiovascular outcomes; 3) carbohydrate type may influence satiety and satiation; glycemic load and glycemic index show links to memory, mood, and concentration; 4) validated biomarkers are needed to demonstrate the known prebiotic effect of carbohydrates; 5) negative effects of fructose are not evident when human data are systematically reviewed; 6) new research indicates that diet strongly influences the microbiome; and 7) there is mounting evidence that the intestinal microbiota has the ability to impact the gut–brain axis. Overall, there is much promise for development of functional foods that impact the microbiome and other factors relevant to health, including glycemic response (glycemic index/glycemic load), satiety, mood, cognition, and weight management.

Informing food choices and health outcomes by use of the dietary glycemic index

Considerable epidemiologic evidence links consuming lower glycemic index (GI) diets with good health, particularly upon aging. The GI is a kinetic parameter that reflects the ability of carbohydrate (CHO) contained in consumed foods to raise blood glucose in vivo. Newer nutritional, clinical, and experimental data link intake of lower dietary GI foods to favorable outcomes of chronic diseases, and compel further examination of the record. Based upon the new information there are two specific questions: 1) should the GI concept be promoted as a way to prolong health, and 2) should food labels contain GI information? Further, what are the remaining concerns about methodological issues and consistency of epidemiological data and clinical trials that need to be resolved in order to exploit the benefits of consuming lower GI diets? These issues are addressed in this review.

Dietary hyperglycemia, glycemic index and metabolic retinal diseases

The glycemic index (GI) indicates how fast blood glucose is raised after consuming a carbohydrate-containing food. Human metabolic studies indicate that GI is related to patho-physiological responses after meals. Compared with a low-GI meal, a high-GI meal is characterized with hyperglycemia during the early postprandial stage (0-2h) and a compensatory hyperlipidemia associated with counter-regulatory hormone responses during late postprandial stage (4-6h). Over the past three decades, several human health disorders have been related to GI. The strongest relationship suggests that consuming low-GI foods prevents diabetic complications. Diabetic retinopathy (DR) is a complication of diabetes. In this aspect, GI appears to be useful as a practical guideline to help diabetic people choose foods. Abundant epidemiological evidence also indicates positive associations between GI and risk for type 2 diabetes, cardiovascular disease, and more recently, age-related macular degeneration (AMD) in people without diabetes. Although data from randomized controlled intervention trials are scanty, these observations are strongly supported by evolving molecular mechanisms which explain the pathogenesis of hyperglycemia. This wide range of evidence implies that dietary hyperglycemia is etiologically related to human aging and diseases, including DR and AMD. In this context, these diseases can be considered as metabolic retinal diseases. Molecular theories that explain hyperglycemic pathogenesis involve a mitochondria-associated pathway and four glycolysis-associated pathways, including advanced glycation end products formation, protein kinase C activation, polyol pathway, and hexosamine pathway. While the four glycolysis-associated pathways appear to be universal for both normoxic and hypoxic conditions, the mitochondria-associated mechanism appears to be most relevant to the hyperglycemic, normoxic pathogenesis. For diseases that affect tissues with highly active metabolism and that frequently face challenge from low oxygen tension, such as retina in which metabolism is determined by both glucose and oxygen homeostases, these theories appear to be insufficient. Several lines of evidence indicate that the retina is particularly vulnerable when hypoxia coincides with hyperglycemia. We propose a novel hyperglycemic, hypoxia-inducible factor (HIF) pathway, to complement the current theories regarding hyperglycemic pathogenesis. HIF is a transcription complex that responds to decrease oxygen in the cellular environment. In addition to playing a significant role in the regulation of glucose metabolism, under hyperglycemia HIF has been shown to increase the expression of HIF-inducible genes, such as vascular endothelial growth factor (VEGF) leading to angiogenesis. To this extent, we suggest that HIF can also be described as a hyperglycemia-inducible factor. In summary, while management of dietary GI appears to be an effective intervention for the prevention of metabolic diseases, specifically AMD and DR, more interventional data is needed to evaluate the efficacy of GI management. There is an urgent need to develop reliable biomarkers of exposure, surrogate endpoints, as well as susceptibility for GI. These insights would also be helpful in deciphering the detailed hyperglycemia-related biochemical mechanisms for the development of new therapeutic agents.

Healthy diets and the subsequent prevalence of nuclear cataract in women

OBJECTIVE

To assess the association between healthy diet scores and prevalence of nuclear cataract in women.

METHODS

The association between healthy diet scores, which reflect adherence to the US dietary guidelines, and prevalence of nuclear cataract determined 4 to 7 years later was assessed in a sample of Women's Health Initiative Observational Study participants (aged 50-79 years) residing in Iowa, Wisconsin, and Oregon. Scores on the 1995 Healthy Eating Index, which reflect adherence to 1990 guidelines, were assigned from responses to food frequency questionnaires at the Women's Health Initiative baseline (1994-1998). Presence of nuclear cataract was determined from slitlamp photographs and self-reports of cataract extractions were assessed from May 1, 2001, to January 31, 2004, in 1808 women participating in the Carotenoids in Age-Related Eye Disease Study.

RESULTS

Having a high 1995 Healthy Eating Index score was the strongest modifiable predictor of low prevalence of nuclear cataract among numerous risk factors investigated in this sample. The multivariate-adjusted odds ratio for high vs low quintile for diet score was 0.63 (95% confidence interval, 0.43-0.91). Higher prevalence of nuclear cataract was also associated with other modifiable factors (smoking and marked obesity) and nonmodifiable factors (having brown eyes, myopia, and high pulse pressure). Vitamin supplement use was not related to cataract.

CONCLUSION

These data add to the body of evidence suggesting that eating foods rich in a variety of vitamins and minerals may contribute to postponing the occurrence of the most common type of cataract in the United States.

Dietary carbohydrate in relation to cortical and nuclear lens opacities in the melbourne visual impairment project

PURPOSE

In vitro and in vivo animal studies suggest that dietary carbohydrates play a role in cataractogenesis. Few epidemiologic studies have been conducted to evaluate this association. The objective of this study was to examine the cross-sectional associations between total carbohydrate intake, dietary glycemic index (dGI), and the risk of cortical and nuclear cataracts.

METHODS

After excluding 864 persons from 2473 eligible participants, 1609 eligible nondiabetic participants (mean age, 57.6 years, 55.9% female) in the Melbourne Visual Impairment Project (VIP) were enrolled. Dietary information derived from a semiquantitative food-frequency questionnaire and cataract status graded by the Wilmer protocol (cortical cataract: opacity >or=4/16; nuclear cataract grade >or=2) were collected. With the use of the generalized estimating approach to logistic regression to account for the lack of independence between the eyes of an individual, the associations between dietary carbohydrates and risk of cataract in eyes with no or a single type (pure) of cataract were examined.

RESULTS

Multivariate adjustment showed that pure cortical cataract (197 eyes) was significantly associated with total carbohydrate intake (odds ratio [OR] comparing the highest quartile with the lowest quartile = 3.19, 95% confidence interval [CI] = 1.10-9.27; P(trend) = 0.017). The OR for nuclear cataract (366 eyes) comparing the third quartile of dGI with the first quartile (OR = 1.64, 95% CI = 1.02-2.65) was significant, but there was not a consistent dose-response association (P(trend) = 0.75).

CONCLUSIONS

Carbohydrate intake may be optimized to prolong eye lens function. Because of the high proportion of subjects with missing covariates, these results warrant further study.

Diabetic cataracts: mechanisms and management

Diabetes mellitus is associated with a 5-fold higher prevalence of cataracts, which remains a major cause of blindness in the world. Typical diabetic cataracts contain cortical and/or posterior subcapsular opacities. Adult onset diabetic cataracts also often contain nuclear opacities. Mechanisms of diabetic cataractogenesis have been studied in less detail than those of other diabetic complications. Both animal and human studies support important contribution of increased aldose reductase activity. Surgical extraction is the only cure of diabetic cataract today. An improved understanding of pathogenetic mechanisms, together with finding effective therapeutic agents, remain highest priority for diabetic cataract-related research and pharmaceutical development.

Effects of lutein and zeaxanthin on aspects of eye health

Lutein and zeaxanthin are members of the oxygenated carotenoids found particularly in egg yolks and dark-green leafy vegetables. A great deal of research has focused on their beneficial roles in eye health. The present article summarises the current literature related to the bioactivity of these carotenoids, emphasising their effects and possible mechanisms of action in relation to human eye health. Available evidence demonstrates that lutein and zeaxanthin are widely distributed in a number of body tissues and are uniquely concentrated in the retina and lens, indicating that each has a possible specific function in these two vital ocular tissues. Most of epidemiological studies and clinical trials support the notion that lutein and zeaxanthin have a potential role in the prevention and treatment of certain eye diseases such as age-related macular degeneration, cataract and retinitis pigmentosa. The biological mechanisms for the protective effects of these carotenoids may include powerful blue-light filtering activities and antioxidant properties. Although most studies point towards significant health benefits from lutein and zeaxanthin, further large-scale randomised supplementation trials are needed to define their effects on ocular function in health and disease.

Validity of carbohydrate, glycaemic index and glycaemic load data obtained using a semi-quantitative food-frequency questionnaire

Objective

To assess the ability of a food-frequency questionnaire (FFQ) to rank Australians according to their intake of total carbohydrate, sugar, starch, fibre, glycaemic index (GI) and glycaemic load (GL).

Design

Cross-sectional sample from a population cohort.

Setting

Two postcode areas west of Sydney, Australia.

Subjects

From 1992 to 1994, a total of 2868 older Australians provided dietary data using a 145-item Willett-derived FFQ. A representative sub-sample of 78 subjects completed three 4-day weighed food records (WFRs). Pearson and Spearman correlations, Bland–Altman plots and weighted kappa values were calculated.

Results

Compared with the WFR, the FFQ provided higher mean estimates of all nutrients except starch and GI. All Pearson and/or Spearman correlations were greater than 0.5, except for GL. For GI, sugar, starch and fibre, the regression lines from the Bland–Altman analysis indicated a non-significant linear trend (P = 0.07, P = 0.36, P = 0.28 and P = 0.10, respectively). For GL and total carbohydrate, however, there was a significant linear trend (P = 0.006 and P < 0.0001, respectively), indicating that as the GL and carbohydrate intake of individuals increased, so did the magnitude of the error between the FFQ and WFR. Weighted kappa values all indicated moderate to good agreement, with the exception of GL which was only fair. The proportions of subjects correctly classified within one quintile for all of the nutrients were over 50% and gross misclassification was low (<10%).

Conclusion

This FFQ was able to rank individuals according to their intakes of total carbohydrate, sugar, starch, fibre and GI, but not as well for GL.

Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies

BACKGROUND

Inconsistent findings from observational studies have prolonged the controversy over the effects of dietary glycemic index (GI) and glycemic load (GL) on the risk of certain chronic diseases.

OBJECTIVE

The objective was to evaluate the association between GI, GL, and chronic disease risk with the use of meta-analysis techniques.

DESIGN

A systematic review of published reports identified a total of 37 prospective cohort studies of GI and GL and chronic disease risk. Studies were stratified further according to the validity of the tools used to assess dietary intake. Rate ratios (RRs) were estimated in a Cox proportional hazards model and combined by using a random-effects model.

RESULTS

From 4 to 20 y of follow-up across studies, a total of 40 129 incident cases were identified. For the comparison between the highest and lowest quantiles of GI and GL, significant positive associations were found in fully adjusted models of validated studies for type 2 diabetes (GI RR = 1.40, 95% CI: 1.23, 1.59; GL RR = 1.27, 95% CI: 1.12, 1.45), coronary heart disease (GI RR = 1.25, 95% CI: 1.00, 1.56), gallbladder disease (GI RR = 1.26, 95% CI: 1.13, 1.40; GL RR = 1.41, 95% CI: 1.25, 1.60), breast cancer (GI RR = 1.08, 95% CI: 1.02, 1.16), and all diseases combined (GI RR = 1.14, 95% CI: 1.09, 1.19; GL RR = 1.09, 95% CI: 1.04, 1.15).

CONCLUSIONS

Low-GI and/or low-GL diets are independently associated with a reduced risk of certain chronic diseases. In diabetes and heart disease, the protection is comparable with that seen for whole grain and high fiber intakes. The findings support the hypothesis that higher postprandial glycemia is a universal mechanism for disease progression.

Carbohydrate nutrition, glycemic index, and the 10-y incidence of cataract

BACKGROUND

Although dietary carbohydrates are thought to play a role in cataractogenesis, few epidemiologic studies have examined links between carbohydrate nutrition and cataract.

OBJECTIVES

We investigated the associations between dietary glycemic index (GI), glycemic load (GL), total carbohydrate intake, and 10-y incident nuclear, cortical, and posterior subcapsular cataract.

DESIGN

Of 3654 baseline participants in an Australian population aged >/=49 y (1992-1994), 933 were seen after 5 and/or 10 y, had completed a detailed semiquantitative food-frequency questionnaire, had no previous cataract surgery or baseline cataract, and had photographs taken to assess incident cataract with the Wisconsin Cataract Grading System. Dietary information was collected with a validated food questionnaire. GI was calculated from a customized database of Australian foods. GI, GL, and all other nutrients were energy adjusted. Hazard ratios (HRs) and 95% CIs were calculated with the use of discrete logistic models.

RESULTS

After age, sex, diabetes, and other factors were controlled for, each SD increase in GI significantly predicted incident cortical cataract (HR: 1.19; 95% CI: 1.01, 1.39). Participants within the highest compared with the lowest quartile of GI were more likely to develop incident cortical cataract (HR: 1.77; 95% CI: 1.13, 2.78; P for trend = 0.035). These findings were similar after excluding participants with diabetes, although they were slightly attenuated and marginally nonsignificant (HR: 1.16; 95% CI: 0.98, 1.37, per SD increase in GI). No association was found between GI and nuclear or posterior subcapsular cataract and between GL or carbohydrate quantity and any cataract subtype.

CONCLUSION

In an Australian cohort, poorer dietary carbohydrate quality, reflected by high GI, predicted incident cortical cataract.

Dietary carbohydrate and the progression of age-related macular degeneration: a prospective study from the Age-Related Eye Disease Study

BACKGROUND

Cross-sectional studies indicate that diets that provide a higher dietary glycemic index (dGI) are associated with a greater risk of age-related macular degeneration (AMD). No prospective studies have addressed this issue.

OBJECTIVE

The objective was to prospectively evaluate the effect of baseline dGI on the progression of AMD.

DESIGN

dGI was calculated as the weighted average of GIs from foods and was evaluated as being above or below the sex median (women: 77.9; men: 79.3) for 3977 participants aged 55-80 y (58% women) in the Age-Related Eye Disease Study. The 7232 eligible eyes without advanced AMD were classified into 1 of 3 AMD categories: group 1 (nonextensive small drusen), group 2 (intermediate drusen, extensive small drusen, or pigmentary abnormalities), or group 3 (large drusen or extensive intermediate drusen). With the use of multifailure Cox proportional-hazards regression, we modeled the time to the maximal progression to evaluate the relation between dGI and the risk of AMD.

RESULTS

Overall, the multivariate-adjusted risk of progression over 8 y of follow-up (x: 5.4 y) was significantly higher (risk ratio: 1.10; 95% CI: 1.00, 1.20; P = 0.047) in the high-dGI group than in the low-dGI group. The risk of progression for groups 1, 2, and 3 eyes was 5%, 8%, and 17% greater, respectively (P for trend < 0.001). The latter gives an estimate that 7.8% of new advanced AMD cases would be prevented in 5 y if people consumed the low-dGI diet.

CONCLUSION

Persons at risk of AMD progression, especially those at high risk of advanced AMD, may benefit from consuming a smaller amount of refined carbohydrates.

Association between dietary glycemic index and age-related macular degeneration in nondiabetic participants in the Age-Related Eye Disease Study

BACKGROUND

Age-related macular degeneration (AMD) is the major cause of irreversible blindness. AMD appears to share several carbohydrate-related mechanisms and risk factors with diabetes-related diseases, including retinopathy and cardiovascular disease (CVD); however, to date, only one small study has addressed this issue.

OBJECTIVE

The objective was to test the hypothesis that dietary glycemic index (dGI), which has been related to the risk of diabetes and CVD, is associated with the risk and severity of AMD in nondiabetic elderly populations.

DESIGN

Dietary information was obtained from 4099 participants aged 55-80 y (56% women) in the Age-Related Eye Disease Study (AREDS). A total of 8125 eligible eyes at baseline were classified into 1 of 5 AMD groups according to the size and extent of drusen, the presence of geographic atrophy, and neovascular changes. We used a generalized estimating approach to evaluate the relations between dGI and risk and severity of AMD with eyes as the unit of analysis.

RESULTS

Compared with eyes in the first quintile of dGI, eyes in the fourth and fifth quintiles had a significantly or suggestively higher risk of large drusen, geographic atrophy, and neovascularization. The multivariate-adjusted odds ratios (95% CIs) for the highest quintile were 1.42 (1.09, 1.84), 1.78 (0.81, 3.90), and 1.41 (0.95, 2.08), respectively, of which only the odds ratio for large drusen was significant. A significant positive relation between dGI and severity of AMD was also noted (P for trend < 0.001). There was a 49% increase in the risk of advanced AMD (geographic atrophy plus neovascularization) for persons with a dGI higher than the sex median (women: >or=77.9; men: >or=79.3). This result indicated that 20% of prevalent cases of AMD would have been eliminated if the AREDS participants consumed diets with a dGI below the median.

CONCLUSION

The association between dGI and AMD from the AREDS cross-sectional analysis at baseline suggests that a reduction in the dGI, a modifiable risk factor, may provide a means of diminishing the risk of AMD.

Dietary macronutrient intake and five-year incident cataract: the blue mountains eye study

PURPOSE

To investigate the relationships between dietary macronutrient intake at baseline and the five-year incidence of the three main types of cataract in older people.

DESIGN

Population-based cohort study.

METHODS

SETTINGS

An urban community near Sydney, Australia.

STUDY POPULATION

The Blue Mountains Eye Study (BMES) examined 3,654 predominantly Caucasian participants aged 49+ years during 1992 to 1994, and then 2,335 survivors (71.5%) after five years. Of these 2,335 subjects, 1988 (85%) completed a Willett-derived food frequency questionnaire (FFQ) at baseline.

OBSERVATION PROCEDURES

A 145-item FFQ was used to assess nutrient intakes and lens photography was used to assess the presence of cataract at both time points.

MAIN OUTCOME MEASURES

Incidence of cortical, nuclear, and posterior subcapsular (PSC) cataract was assessed via lens photographic grading following the Wisconsin cataract grading method.

RESULTS

After adjusting for multiple known cataract risk factors, higher dietary intakes of omega-3 polyunsaturated fatty acids (n-3 PUFA) were associated with a reduced incidence of nuclear cataract. The odds ratio (OR) for subjects in the highest quintile of intake compared to those in the lowest quintile was 0.58 (95% confidence interval [CI] 0.35 to 0.97), P(trend) = .027. Similarly, for PSC cataract, higher dietary intakes of protein were protective (OR 0.28; 95% CI 0.10 to 0.76), P(trend) = .015. Dietary macronutrient intake was not associated with incident cortical cataract.

CONCLUSIONS

Higher dietary intakes of n-3 PUFA may decrease the five-year risk of nuclear cataract, whereas higher dietary intakes of protein may decrease risk for PSC cataract.

Oxidative stress in cataracts

Oxidative stress is the result of an imbalance of antioxidants and pro-oxidants. Since toxic free radicals are the result of normal metabolism, their destruction is imperative. Cataracts are the leading cause of blindness worldwide. Opacity of the lens is a direct result of oxidative stress. Cataracts occur primarily due to age, but also are common in diabetes where superoxide in the mitochondria is elevated as a result of hyperglycemia. This review will investigate the risk factors of cataract including diet (vitamins, fat and alcohol) as well as UV light and diabetes. The pathophysiology of lens opacification will be discussed and related to the biochemistry, especially during the aging process and in diabetes. Animal and human supplemental antioxidant studies will be reviewed and the mechanisms discussed for cataract prevention and treatment. New genetic engineering approaches to overexpress antioxidant enzymes have given intriguing results and show promise. Lastly, a new approach to target mitochondrial superoxide with antioxidant molecules will be outlined.

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.

Dietary carbohydrate intake and glycemic index in relation to cortical and nuclear lens opacities in the Age-Related Eye Disease Study

BACKGROUND

Little is known about the association between dietary carbohydrates and cataract in nondiabetic persons.

OBJECTIVE

The aim was to test whether recent dietary carbohydrate intakes or glycemic index (GI; a measure of carbohydrate intake quality) was associated with the presence of cortical or nuclear opacities.

DESIGN

A modified Block food-frequency questionnaire was used to obtain dietary information from 3377 participants (aged 60-80 y; 56% were women) in the Age-Related Eye Disease Study (AREDS). Lens status was evaluated by using the AREDS System for Classifying Cataracts. Associations were examined for eyes with only a single, or pure, type of lens opacity by using the generalized estimating approach to logistic regression to account for the lack of independence between the eyes of a person.

RESULTS

For participants in the highest quartile, dietary GI was associated with a higher prevalence of all pure nuclear opacities [grade >2; odds ratio (OR): 1.29; 95% CI: 1.04, 1.59; P for trend = 0.02] and moderate nuclear opacities (grade > or =4; OR: 1.43; 95% CI: 0.96, 2.14; P for trend = 0.052). The OR in a comparison of the highest with the lowest quartile of intake was 1.27 (95% CI: 0.99, 1.63; P for trend = 0.09) for cortical opacities of any severity (>0% of area opaque), and the OR increased somewhat for moderate cortical opacities (>5% of area opaque; OR: 1.71; 95% CI: 1.00, 2.95; P for trend = 0.056).

CONCLUSIONS

Results from the cross-sectional analysis of AREDS baseline data suggest that dietary glycemic quality and dietary carbohydrate quantity may be associated with prevalent nuclear and cortical opacities, respectively.

Dietary glycemic index and carbohydrate in relation to early age-related macular degeneration

BACKGROUND

Several dietary factors have been linked to age-related maculopathy (ARM), the early form of age-related macular degeneration, and there is reason to think that dietary carbohydrate may play a role in the development of ARM.

OBJECTIVE

The purpose of the present study was to examine the relation between dietary carbohydrate quality, as measured by dietary glycemic index (GI) or total carbohydrate intake, and ARM.

DESIGN

From the Nurses' Health Study, 1036 eyes from 526 Boston-area participants without a previous ARM diagnosis were included in the present study. The presence and degree of ARM were classified by the Age-Related Eye Diseases Study system. Long-term dietary information was based on data from an average of 4 food-frequency questionnaires collected over a 10-y period before the assessment of ARM. With eyes as the unit of analysis, we used a generalized estimating approach to logistic regression to estimate the odds ratios for ARM in a manner that accounted for the lack of independence between the 2 eyes from the same subject.

RESULTS

After multivariate adjustment, dietary GI was related to ARM (specifically to retinal pigmentary abnormalities), whereas total carbohydrate intake was not. The odds ratio for ARM being in the highest tertile of dietary GI (> or =77.0) versus the lowest (<74.6) was 2.71 (95% CI: 1.24, 5.93; P for trend = 0.01). Neither dietary GI nor total carbohydrate intake was related to drusen.

CONCLUSION

Our results suggest that dietary GI may be an independent risk factor for ARM.