Vitamins C and E and Prevention of Cataracts

In the U.S., more than 20 million people age 40 and older have age-related cataracts — 50 percent of them with impaired vision as a result.

Although many ways to prevent cataracts have been tested, smoking is the only well-documented modifiable risk factor that is known to increase the risk of cataracts. The use of vitamins, especially antioxidant vitamins such as vitamins C and E, has been touted as a way to prevent cataracts. But the results of previous randomized trials, comparing these vitamins to placebos, have thus far been disappointing.

A new large study sought to examine the use of vitamins C and E in ways that had not previously been studied. The authors of the study, which was recently published in the Archives of Ophthalmology, stated, “There have been no data for vitamin E treatment durations longer than 6.5 years in men and no data for supplementation with vitamin C alone in men or women.” Previous longer-term studies in women had failed to show any benefit of vitamin E for cataract prevention.

The study participants, 11,545 men age 50 or older without cataracts at the start of the study, were randomized to receive 400 international units (IU) of vitamin E or placebo on alternate days and 500 milligrams of vitamin C or placebo daily for eight years. This meant there were four groups being studied: One group got both vitamins C and E; another, vitamin C and a placebo; a third, vitamin E and a placebo; and the fourth, two placebos. There were between 2,800 and 2,900 men in each of the four groups.

During the course of the study, 1,174 new cataracts were confirmed in the men. However, there was no decrease in the rate of new cataracts in any of the treated groups compared to the groups getting no treatment. There also was no decrease in the rate of new cataracts between the group getting both vitamins and the groups getting one vitamin or no vitamins.

The study’s authors pointed out that this was the first randomized trial to report on the individual effect of vitamin C supplementation in the prevention of cataracts. The previous studies tested vitamin C as one ingredient in an antioxidant cocktail, and thus its individual effect on cataracts could not be estimated.

It had been previously thought that these antioxidant vitamins might be most effective in people with higher levels of oxidative stress, such as smokers or individuals with hypertension or diabetes. However, the study did not demonstrate this, even when the data were analyzed to focus on people in these groups.

The authors’ conclusion adds cataracts to the list of diseases not prevented by vitamins C or E: “Long-term alternate-day use of 400 IU of vitamin E and daily use of 500 mg of vitamin C had no notable beneficial or harmful effect on the risk of cataracts.”

The following information is from WorstPills.org and represents the updated version of our reviews of studies testing whether vitamin C or E can prevent certain other diseases, in addition to cataracts:

Vitamin C and your health

Vitamin C deficiency, known as scurvy, is rare. It is seen occasionally in people whose diet does not supply enough vitamin C — for example, some older adults who live alone, alcoholics and drug abusers. Symptoms of scurvy include anemia, loose teeth, red and swollen gums, wounds that do not heal and small broken blood vessels that cause tiny purplish-red spots on the skin. Scurvy is easily prevented and is treated by increasing the intake of vitamin C through diet and a supplement.

Common cold

One of the most common uses for large doses of vitamin C has been to prevent or reduce the severity of colds. A recent study randomized people to receive either a supplement containing 30 milligrams of vitamin C (less than one-half of the recommended daily allowance) or 1 or 3 grams of vitamin C upon the onset of a cold and for two subsequent days. There was no difference in the duration or severity of colds in people getting 1 or 3 grams of vitamin C and those getting only 30 milligrams a day.

A 2004 review of short-term, randomized controlled trials published by the Cochrane Collaboration, a highly respected nonprofit organization, found that taking vitamin C does not prevent upper respiratory infections such as the common cold.

Decreasing mortality

A meta-analysis of three small trials in older adults published in the Aug. 28, 1999, British Medical Journal found no beneficial effect of vitamin C on decreasing mortality.

Kidney stones

Editors of The Medical Letter caution that high doses of vitamin C — more than 1,000 milligrams — are poorly absorbed, cause diarrhea and can increase the risk of kidney stones in people prone to develop them.

Vitamin C and cancer

A large study published in the January 2009 Journal of the American Medical Association refutes the belief that vitamins, specifically large quantities of vitamins C and E, can prevent cancer. The study’s authors concluded that their data provided “no support for the use of these supplements in the prevention of cancer in middle-aged and older men.”

Vitamin C could be recommended as a cancer preventive only if it reduced the number of cases of cancer in a randomized controlled trial. For almost a decade, such a randomized study has been under way in China in which patients with precancerous lesions in their stomachs receive either a combination of drugs, or vitamins (C and E) and a micronutrient, or garlic. The trial found that neither garlic nor the combination of the vitamins and a micronutrient (selenium) had any effect on reducing the occurrence of gastric cancer.

Vitamin E and your health

Vitamin E deficiency is extremely rare and has not been known to occur solely from an inadequate diet. It has occurred mainly in people who have certain conditions of their intestines, pancreas or liver that interfere with their body’s ability to absorb this fat-soluble vitamin.

Vitamin E and cancer

A major international clinical trial published in the March 16, 2005, Journal of the American Medical Association found that 400 IU of natural vitamin E taken daily did not reduce the overall risk of cancer or cardiovascular disease in men and women age 50 to 75 who had existing cardiovascular disease or diabetes. Actually, there was an increase in the risk of heart failure in the patients taking vitamin E.

Another large, randomized study of the use of vitamin E found that, compared to a placebo, vitamin E did not have a significant effect on the incidence of mortality from pancreatic cancer.

Respiratory tract infections

A randomized, placebo-controlled study of 200 IU of vitamin E supplements (the recommended daily dietary intake is about 15 IU in men and 12 IU in women) in well-nourished people age 60 or older failed to show that vitamin E decreased the incidence of acute respiratory tract infections. Instead, it showed that those people taking vitamin E had a significantly increased severity of respiratory infections when they did occur, compared to people taking a placebo.

Osteoarthritis

A randomized, placebo-controlled trial of vitamin E for six months failed to show any benefit for the management of symptomatic osteoarthritis of the knee.

Heart problems

A randomized, placebo-controlled trial found that vitamin E supplementation did not result in any significant improvements in heart failure or quality of life in patients with advanced heart failure.

In another large study of women and men age 55 or older at high risk for cardiovascular events (e.g., heart attacks, strokes), the use of 400 IU of vitamin E for an average of 4.5 years had no beneficial effect on cardiovascular outcomes.

At this time, there is insufficient evidence to recommend the use of vitamin E for the prevention of heart attacks — or for any other medical purpose.