Vitamins: Do They or Don't They Prevent Cataracts?

There are different types of cataracts, depending on their location in the lens of the eye. The outermost layer is called the posterior subcapsular cataract. Cataracts in the next layer are called cortical cataracts and the most central location of the lens is called the nuclear cataract. The type that occurs the least is the posterior subcapsular type. This type and the cortical type cataracts were analyzed as to their relation to vitamin supplements and were covered in a 2002 report from the American Journal of Clinical Nutrition. A group of 492 nurses were studied, aged 53 to 73 years, who had been followed for at least seventeen years. Foodstuffs and vitamin uses were investigated many times during the study period.

This report stated that the number of posterior subcapsular cataracts came to 86 and 248 cortical types of cataracts were determined. The investigators announced that their results found no connection between any antioxidants or vitamins. Furthermore they performed a sub analysis and found that Vitamin C, if taken in dosages of 360 milligrams or more (far over the recommended 70 milligrams daily) reduced the risk of cortical cataracts by almost 60 percent in women under the age of 60. However, among women taking 240 to 360 milligrams, the risk actually appeared to increase to more than double the number. Women under the age of 60 years who were taking Vitamin C containing supplements for at least five years showed a 67 percent reduction in cortical cataracts. But women over the age of 60 years, taking vitamin C supplements for 5 to 9 years, had a doubled risk of cortical cataracts.

Another finding was that for those who never smoked cigarettes and increased their total carotenoid intake (alpha and beta carotenes, lycopenes, lutein) - the result was a reduction in posterior subcapsular cataract risk by 66 percent. The reduction was even greater with those with increased folic acid intake (more than 70 percent). The authors concluded that "Our results support a role for Vitamin C in thwarting the risk of cortical cataracts in women less than 60 years of age and for carotenoids which diminished the risk of posterior subcapsular cataracts in women who have never smoked."

Reviewers have commented that many inconsistencies exist. It makes sense that antioxidants could reduce the risk of cataracts because the lens of the eye is exposed to oxidant changes. This is the same chemical process that rusts iron and makes cooking oil turn rancid. In the eye, the oxidative process can occur as part of normal metabolism as well as in the presence of light, which creates harmful unstable molecules called free radicals. These free radicals grasp electrons from your body's healthy molecules to balance themselves, causing an ever escalating molecular free for all that ends up hurting perfectly innocent cells. The lens can partially protect itself from this free radical damage. It relies on certain nutrients to keep its defense strong. It has been established that vitamins C and E and beta carotene are helpful. The evidence shows that when these nutrients are taken together they work best.

In addition to the vitamins mentioned above it is recommended that minerals such as selenium, zinc and copper may all play roles in the protection goals for the lens of the eye. Even B Vitamins such as riboflavin and B12 as well as an amino acid called cysteine may help. But evidence for the benefits of these substances is very slim. Some show no benefits at all from antioxidants and among the studies that show positive results there is little consistency concerning which antioxidants are providing the benefits. Vitamin C, Vitamin E, folic acid, beta carotene and other carotenoids previously mentioned all have been found to protect against cataracts in some studies, but do nothing in other research results.

For instance, why did Vitamin C reduce risk only in women under the age of 60 years of age? Why in women over 60 years of age using Vitamin C supplements for 5 to 9 years should there be an increased risk? It also appears that that the authors analyzed cataracts by eyes, not person. Before, if a woman had a cataract in both eyes or two types of cataracts in one eye they were considered separately. This could have markedly biased the results.

There was no noticeable beneficial or harmful effect on the risk of cataract, according to William Christen, ScD, OD of Brigham and Women's Hospital in Boston, and his colleagues. Their findings come from a randomized placebo-controlled trial, the longest yet to test antioxidant supplements as a potential preventative measure for cataracts as reported in the Archives of Ophthalmology. While the outcome showed no effect, the study doesn't put to bed the notion that antioxidants may help prevent cataracts. The researchers noted that cataracts develop slowly and prevention may require even longer periods of treatment and perhaps at earlier ages. The analysis was based on the Physician's Health Study II which looked at the effects of Vitamin E, Vitamin C and a multivitamin on the prevention of cancer and cardiovascular disease in some 14,641 male doctors. As a secondary endpoint, the researchers also studied cataract incidence among the doctors, all ages of 50 or greater.

The cataract data, they added, "represent the longest treatment duration for Vitamin E in men and the first trial data for Vitamin C alone." Half of the participants were randomly assigned to get Vitamin E or placebo every other day. Within each arm the doctors were assigned to get either daily Vitamin C or placebo. During an average follow up of eight years the researchers reported, 1,174 cataract extractions were confirmed. There were 579 cataracts in the Vitamin E group and 595 in the placebo group, for a hazard ratio of 0.99 which was not significant. There were also no significant effects of Vitamin E on the incidence of nuclear, cortical or posterior subcapsular cataracts. In the Vitamin C group, there were 593 cataracts, compared with 581 in the placebo group, for an non-significant hazard ratio of 1.02. As with Vitamin E there were no significant effects based on subtype.

Some studies agree that Vitamin E may play a role in preventing cataracts. In a large, long term study of more than 3,000 adults (Ages 43 to 86) in Wisconsin, risk for cataracts was 60 percent lower among people who reported using multivitamins or any supplement containing Vitamin E or Vitamin C for more than 10 years, compared with non users. In a 2008 study that evaluated the dietary intake of more than 35,000 female health professionals, women whose diets (including supplements) had the highest levels of lutein and Vitamin E had a lower relative risk of cataracts than women whose diets were in the lowest 20 percent for levels of these nutrients. However, other studies provide conflicting findings and some eye doctors say more research is required before a clear conclusion can be reached.

The majority of researchers suggest additional food tips: Daily alcohol imbibers up their odds for cataracts by about a third with people who rarely drink. A Harvard University study found that women who ate spinach more than five times a week had a 47 percent decrease in the risk of cataract surgery compared with those who ate spinach less than once per month. In fact, it is a good idea to eat a variety of fruits and vegetables.

Doctors agree that the following nutrients may help to delay the development of cataracts:

Beta Carotene: 25,000 international units.

Copper: 1 milligram for every 10 milligrams of zinc, but no more than 2 milligrams.

Selenium: 50-200 micrograms.

Vitamin C: 500-3000 milligrams.

Vitamin E: 400 international units.

Zinc: 15-50 milligrams.

Users are alerted not to take 100 micrograms of selenium daily without medical supervision. If a person is taking anticoagulant drugs, then Vitamin E supplement should be avoided. It would require bowls and bowls of wheat germ ingestion to equal the capsules that offer the daily requirements. Also, more than 15 milligrams of zinc may need medical supervision. The case for zinc indicates that it helps to prevent retinal deterioration as we age. The body needs zinc to make several antioxidant enzymes found in the eye.