Nutritional Effect on Age-Related Cataract Formation and Progression

Ruti Sella; Natalie A. Afshari

Disclosures

Curr Opin Ophthalmol. 2019;30(1):63-69. 

In This Article

Recent Publications (2014–2108)

Fatty Acids and Sterols

The lipid composition of the lens changes during cataract formation,[34] and previous studies demonstrated a correlation between dietary linoleic acid and an increase risk of nuclear cataract.[35] Studies aiming to identify key molecules in the prevention of lens protein aggregation have pointed at lanosterol as a promising agent in in-vivo studies.[36] Zhao et al. in their innovative study, showed that small molecules derived from diet may reduce the risk of cataract and, moreover, hold the potential to reverse existing cataracts. Makley et al.[37] reported two oxysterols, which hold the potential to reverse cataract. Lanosterol synthase pathway was later found to be associated with alleviation of lens opacity in age-related cortical cataract,[38] and to disrupt the aggregation of lens crystallins.[39] Its influence over cataract by means of phytosterol supplements or nutritional enrichment, or by means of eye drops is yet to be assessed in clinical trials in human subjects. Given the above studies, the increased risk of cataract with statin use has been extensively evaluated and is summarized in a metanalysis by Yu et al..[40] The authors concluded that there is no current evidence for the increased risk of cataract with the use of statins.

Vitamin E, Vitamin C and Vitamin A

Three meta-analysis point at a correlation between a higher intake of vitamin E,[41] vitamin C[42] and vitamin A[43] and a reduced risk for the progression of cataract; dietary as well as dietary and supplemental vitamin E intake, were associated with decreased risk of ARC. Dose response analysis showed a nonlinear association between dietary vitamin E intake and ARC, and the risk of ARC decreased with an intake from 7 mg/day. High-serum tocopherol levels showed the same significant association by this meta-analysis, which included 27 relevant articles, which met the inclusion criteria.[41] Fifteen articles for vitamin C intake and eight for serum ascorbate were included in the Wei et al. meta-analysis. The authors concluded that higher intake of vitamin C and serum ascorbate might be inversely associated with risk of cataract, hence vitamin C intake should be considered for primary prevention.[42] To summarize the epidemiologic studies of vitamin A and ß-carotene potential protective effect against the progression of cataract, Wang et al.[43] published their summery including twenty-two papers, and concluded that a great vitamin A and ß-carotene intakes are inversely associated with cataract risk.

Folic Acid, Vitamin B6 and Vitamin B12

An interesting study evaluated the effect of a supplement of folic acid, vitamin B6 and vitamin B12 on the incidence of cataract and cataract surgery in a randomized controlled fashion.[44] In this study, 5442 female health professionals aged 40 years or older, with preexisting cardiovascular disease were assigned to placebo or a combination supplement of folic acid (2.5 mg/day), vitamin B6 (50 mg/day) and vitamin B12 (1 mg/day). The study's endpoint was not only cataract extraction but also the incident of age-related lens opacity, which reduces visual acuity to worse than 20/30, during 7.3 years of treatment based on both exam and self-report. Interestingly there was no documented effect of the supplement on cataract; however, more risk of cataract extraction in the treatment group.

Vitamin D

As an antioxidant, vitamin D is known to play a role in the pathogenesis of several ocular diseases, namely age-related macular degeneration,[45,46] diabetic retinopathy[47,48] and glaucoma[49] through its role in the reduction of oxidative stress.[50–52] On one hand, vitamin D may have a preventive effect in the cataractogenous process because of its beneficial effect on proteins photooxidation;[53,54] however, ultraviolet (UV) light exposure is a well established independent risk factor for the progression of ARC, and the majority of vitamin D is produced in the skin secondary to direct UV light exposure. The study by Jee et al.[55] was the first epidemiological study to attempt to evaluate the association between serum 25-hydroxyvitamin D levels and age-related cataract in a population of 18 804 patients. The authors concluded that the ARC risk was lower in the presence of highest quintile serum 25-hydroxyvitamin D levels compared with the lowest quintile in men only (24% lower risk for cataracts), after adjusting for confounders. No such association was found in women. This sex difference can theoretically be attributed to the sun exposure differences between men and women as well as dietary variances between the sexes; however, genetic differences may play an important role as well.[32] Whether vitamin D supplements will prove to be beneficial in the prevention of cataract progression is yet to be clarified.

Vitamin K1

High intake of fruit and vegetables was previously associated with a lower cataract prevalence.[55] Green vegetables such as Parsley, kale, spinach, endive, brussels sprouts, broccoli and asparagus, to name a few, are known to contain high vitamin K1 levels. Due to the known dual antioxidant and anti-inflammatory role of vitamin K1, its risk in the process of cataract progression was investigated by Camacho-Barcia et al.[12] among an elderly Mediterranean population. The authors used the database of the PREDIMED study, a randomized clinical trial in participants at a high cardiovascular risk and evaluated patients' dietary vitamin K1 intake using food questionnaires. Their study finds that high intake of dietary vitamin K1 is associated with a reduced risk of cataracts in this cohort of patients. Specifically, patients in the highest tertile of dietary intake had a lower risk of cataracts (hazard ratio 0.71, P = 0.02) after adjusting for confounders. Study's limitations mainly included the use of questionnaires rather than the direct evaluation of vitamin K1 plasma levels and the focus on elderly patients with high cardiovascular risk, which do not necessarily represent the healthy population. The results, however, call for further studies to investigate and prove the importance of dietary vitamin K1 intake on cataract progression.

Mediterranean Diet

Metabolic syndrome, which is known to be diet-dependent through its influence over obesity, impaired fasting glucose and high blood pressure, was also shown to have an impact over age-related cataract formation.[56] Men with metabolic syndrome were found to have a 64% increased risk of nuclear cataract, whereas women had a 56% increased risk of cortical cataract. Both sexes had almost 50% increased risk of any cataract.[56] Mediterranean diet has long been considered a healthy diet with a potential to decrease oxidative stress and metabolic syndrome.[57,58] The incidence of cataract surgery in elderly patients was compared between a low-fat diet group and a Mediterranean diet (either enriched with olive oil or with nuts) in 5802 men and women participating in a clinical trial.[15] During a 7-year follow-up, the incidence of cataract surgery was found similar in all groups.

Dairy Intake

Dairy products contain micronutrients, which may all play a role in the progression of cataract, and most were separately investigated in the past for their protective effect with mixed results. These include calcium, magnesium, phosphorus, potassium and vitamins A and B12.[43,44,59] Dairy products also contain carbohydrates and lipids, which were shown to be associated with the incidence of cataract in previous studies.[3,4,60,61] Older studies investigating the relation between total dairy product consumption and the progression of cataract had not had a unanimous conclusion; Back in the 80s, two studies concluded that milk consumption may pose a risk for cataract formation,[62,63] however, in a more recent case–control study,[64] dairy products did not seem to change the risk of cataract. In addition, studies regarding yogurt consumption have pointed at a potential protective effect in contrast to milk.[65] Camacho-Barcia et al.,[66] therefore, looked at the association of total dairy intake as well as consumption of specific dairy products, and their association with the incidence of cataract surgery in an elderly Mediterranean population with a high cardiovascular risk (based on the database of the PREDIMED study). The authors concluded that patients in the higher (second and third tertiles) of skimmed yogurt intake were at a lower risk of cataracts. Milk consumption and total dairy products were not significantly associated with a higher risk of needing a cataract surgery. Although the study was done on a large cohort of patients, it does separately analyze risk factors for the progression of cataract, but rather the incidence of cataract surgery. Major studies are needed to further understand, which dairy products are protective, and which may be considered as culprit agents in the cataractogenous process.

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