Beyond deficiency: new roles for vitamins2001 assessment of nutritional influences on risk for cataract
Introduction
I had the pleasure of meeting Larry Machlin approximately 15 y ago. The man I met was kind and friendly. We had some cause for a natural friendship when it became clear that, although many years separated us, we had attended neighboring high schools in the Bronx.
Larry encouraged me to pursue studies regarding correlations between nutrient intake and eye health, with the first step being to determine whether there was a correlation between intake of specific nutrients and levels of the nutrients in eye tissues. This was a large challenge because I was relatively junior and unestablished, there had been only one publication regarding nutrition and risk for eye disease, and there was no clearly established discipline of nutritional ophthalmologic epidemiology. Another obstacle was that I had training as a chemist, not a nutritionist. We achieved the initial goal and several others, and those papers are some of the most frequently quoted papers in the literature on ophthalmologic nutrition and epidemiology. His appreciation of the literature and constantly keeping his ear to the ground also allowed Larry to act as an unofficial coordinator of much of the ophthalmologic nutrition effort. Indeed, many of the questions we subsequently asked were inspired by questions he had asked.
Larry was also a friend. He always asked a heartfelt question about the family and shared his own situation. In the workplace such humility and friendship means a lot, especially to those beginning their careers. His friendship and unique mixture of supportive questioning and the resources that he brought to bear on the questions leave a gap that will be hard to fill.
Section snippets
Cataract as a public health issue
It is clear that oxidative stress is associated with compromises to the lens. Recent literature has indicated that antioxidants may ameliorate that risk and actually decrease risk for cataract. This article briefly reviews the etiology of cataract. It also reviews the epidemiologic information, with an emphasis on roles for vitamins C and E and carotenoids. More thorough recent reviews are available.1, 2
Annual cost of age-related prevalence
Cataract is one of the major causes of preventable blindness throughout the world.3, 4, 5 In the United States, the prevalence of visually significant cataract increases from approximately 5% at age 65 y to about 50% for persons older than 75 y.6, 7, 8 In less-developed countries, such as India,9 China,10 and Kenya,11 cataracts are more common and develop earlier in life than in more-developed countries.8, 9 The impact of cataract on impaired vision is much greater in less-developed countries,
Age-related damage involves oxidative insult and declines in protective capabilites
The primary function of the eye lens is to collect and focus light on the retina (Fig. 1). To do so, it must remain clear throughout life. The lens is exquisitely organized. A single layer of epithelial cells is directly under the anterior surface of the collagenous membrane in which it is encapsulated (Fig. 1b). The epithelial cells at the germinative region divide, migrate posteriorly, and differentiate into lens fibers. As their primary gene products, the fibers elaborate the predominant
Epidemiologic studies regarding associations between antioxidants and cataract
Because cataract is due in part to oxidative stress on lens constituents and the enzymes that might normally remove these damaging moieties (reviewed in Fig. 2 and Taylor82), considerable effort is being dedicated to determine whether antioxidants can be used to diminish risk for cataract. The overall impression created by the data indicates that nutrient intake is related to risk for cataract and that nutrition might be exploited to diminish the risk for this debility.
The data regarding a
Conclusion
Light and oxygen appear to be a boon and a bane. Although necessary for physiologic function, when present in excess or in uncontrolled circumstances, they appear to be causally related to cataractogenesis. With aging, compromised function of the lens is exacerbated by depleted or diminished primary antioxidant reserves, antioxidant enzyme capabilities, and diminished secondary defenses such as proteases. Smoking15 and light exposure14 appear to provide oxidative challenges and are associated
Acknowledgements
The authors acknowledge the assistance of Tom Nowell in the preparation of figures and Paul Jacques and Suzen Moeller for invaluable assistance in evaluating the epidemiologic data.
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Major dietary patterns in relation to age-related cataract
2021, Clinical Nutrition ESPENCitation Excerpt :Accumulation of free radicals and other reactive species damages lens proteins and antioxidants which can be endogenous (eg, antioxidant enzymes) or obtained exogenously (dietary). The lens may be protected against oxidative stress through several mechanisms [28]. The main dietary sources of multiple types of antioxidants (such as carotenoid, xantophylls, lutein, zeaxanthin, vitamin C, vitamin E and β-carotene) were from vegetables, fruits and egg yolks.
Inhibiting effects of dietary polyphenols on chronic eye diseases
2017, Journal of Functional FoodsCitation Excerpt :Developing and/or identifying functional foods that could prevent or delay the onset of cataracts would decrease the number of those suffering from blindness. Studies have shown that consumption of fruits and vegetables is associated with a reduced risk of chronic and degenerative diseases of aging and may have potential to prevent cataracts as well (Mares, 2004; Taylor & Hobbs, 2001). In a report on cataract risk in American women, eating habits and cataracts were investigated in 479 women between the ages of 52 and 73 years and the prevalence of cataracts in the high fruit consumption group (3.9 portions/day) was 42% lower than in the control group (1.3 portions/day) (Moeller et al., 2004).
Ascorbate stimulates endothelial nitric oxide synthase enzyme activity by rapid modulation of its phosphorylation status
2012, Free Radical Biology and MedicineCitation Excerpt :Mean plasma levels of ascorbate are between 50 and 60 μM for healthy, well-nourished, nonsmoking individuals and can be increased up to 100 μM by oral supplementation [7–11]. Low levels of plasma ascorbate are observed in several diseases linked to increased oxidative stress, such as cancer, diabetes mellitus, cataract, HIV infection, and sepsis, or in smokers [12–19]. In cultured endothelial cells ascorbate was shown to stabilize the eNOS cofactor BH4 [20,21].
Controversy over "Contradiction": Should Randomized Trials Always Trump Observational Studies?
2009, American Journal of OphthalmologyMicroemulsions as carriers for drugs and nutraceuticals
2006, Advances in Colloid and Interface ScienceCitation Excerpt :The carotenoids are situated in the macula (macula lutea, yellow spot) between the incoming photons and the photoreceptors. As a result, lutein can function as a blue light filter (400–460 nm) [95–98]. Garti and colleagues used microemulsion systems (Fig. 24) similar to those used by Spernath et al. [83], using glycerol instead of propylene glycol as the co-solvent, and a lower oil to co-surfactant ratio [90].
The potential role of nutrition on lens pathology: a systematic review and meta-analysis
2019, Survey of OphthalmologyCitation Excerpt :We included only observational studies, a fact that could influence the overall strength of evidence and shows the need for new meta-analyses based only on interventional trials. A detailed list of all studies that have been excluded from analysis is presented as Supplementary Material (Characteristics of included and excluded studies).1-3,5,6,9-12,14-16,24,25,29,35,39,43,46-49,55 Follow-up periods of included studies varied from months to 15 years.