By Donald R. Davis, Ph.D.
Cataracts are a leading, but treatable, cause of vision loss occurring primarily in elderly persons. Vision is impaired by foggy or opaque areas in the front of the eye that scatter or block light from its path to the retina. About 20% of Americans between 65 and 74 years old have impaired vision due to cataracts, and the incidence increases to 45% in those 75 and older. Diabetic individuals are especially vulnerable.
There is growing evidence that cataracts can be delayed or prevented by good nutrition and other measures …
A few cataracts occur in the cornea at the very front of the eye, but most appear in the crystalline lens, a transparent organ immediately behind the iris. This lens is about the size and shape of an M & M candy: It has no blood supply, so it must sustain itself by obtaining nutrients and eliminating waste products through its surroundings. The fluid around the lens is normally extremely rich in vitamin C, apparently because it helps protect the lens interior from oxidative stress, including the ultraviolet part of sunlight.
There is growing evidence that cataracts can be delayed or prevented by good nutrition and other measures that support and protect the lens. Because most cataracts become troublesome only near the end of life, even a few years of delay could have a major public health impact. Modern cataract surgery by a skilled surgeon is highly successful, but it is costly to society. The clouded lens is removed and replaced with an artificial implant. About 2 million cataract surgeries are performed in the U. S. annually, at a direct cost of over $5 billion. Cataract care, including doctor visits, accounts for about five percent of our Medicare budget. The indirect costs of cataract-associated accidents, broken hips and errors of reading medication labels may be greater still.
Even before the 20th century there were suspicions that nutrition played a role in cataract prevention. In an 1876 book on cataract, scientist R. B. Carter wrote, “there can be no doubt that under the influence of a suitable diet and regimen … a person may preserve his eyesight.”
In 1952, ophthalmologist D. T. Atkinson published a professional article about his experience using nutrition to counter cataracts in a poorly nourished Texas community. He emphasized vitamin C-rich fruits and vegetables, a pint of milk and two eggs daily, plenty of water, and supplements of vitamins C and A. Among his 450 treated patients with early cataracts, he reported that many had not progressed for up to 11 years, whereas in the past nearly all his untreated patients progressed rapidly to surgery.
These and other early reports are supported by dozens of later studies in animals and humans. Two recent examples come from Harvard researchers. In the large Harvard Nurses study, middle-aged nurses who reported consuming the most carotene-containing vegetables had about a 35% lower risk of cataracts in the next 10 years than those who consumed the least. Interestingly, spinach and other greens seemed protective, perhaps because green vegetables contain different types of carotenes or other protective substances. Nurses who had taken vitamin C supplements for at least 10 years had a 45% lower risk. In a smaller, five-year study of U. S. male physicians, those who took only multivitamin supplements had about a 25% lower incidence of new cataracts or cataract surgery than those who took no supplements.
So far there are no results from more definitive studies in which subjects are randomly assigned to receive either nutritional intervention or a placebo, except for one positive finding in China. Such studies are currently underway in the U. S., and they should advance our knowledge about the role of nutrition in slowing, preventing, and possibly even reversing some early cataracts. But, unfortunately, it will be difficult to assess possible large individual differences in which foods or nutrients, and their amounts, may be most valuable for a given individual. Many diverse nutrients play potentially important roles, and these nutrients likely interact in complex ways with genetic differences and several known environmental hazards.
Based on present limited knowledge, those wishing to prevent or slow the development of cataracts should consider the following ten nutritional and other measures:
• Eat a high quality diet, especially the currently recommended five to nine servings per day of fruits and vegetables. Spinach and other green, leafy vegetables may be especially valuable.
• Eat less prepared foods containing added sugars, added fats, and white flour, because these major sources of depleted calories crowd out of our diets other, far more nutritious foods.
• Use daily supplements of vitamins C and E (at least 500 mg and 200 IU) and a broad multivitamin and mineral supplement containing selenium (50 micrograms).
• Use ultraviolet-absorbing glasses or dark glasses to reduce the oxidative stress of midday sunlight on our eyes.
• Reduce or eliminate smoking.
• If blood sugar levels or blood pressure are high, follow recommended measures to lower them, including regular exercise and possibly chromium supplements.
• Use supplements of cysteine or N-acetyl cysteine (along with vitamin C, selenium, and other nutrients) to help produce and maintain glutathione, which seems to be a major part of the antioxidant defense system of the eye lens. (Glutathione itself is not well absorbed.)
• Try a three-to six-month trial with little or no milk consumption to identify unusual cataracts caused by lenses that are not able to handle the galactose part of lactose (milk sugar). Rare hereditary galactose intolerance can cause cataracts even in infants. Yogurt seems to pose no risk, and was reported beneficial in one study.
• There is anecdotal evidence that riboflavin intakes of 100 to 500 mg per day may halt or regress some cataracts, and both riboflavin and vitamin B6 play known roles in the synthesis of protective glutathione.
• Try to avoid or reduce use of steroid drugs, especially oral forms, but also inhaled steroids used to treat asthma