7 April 2010
The potential of fruit and vegetables to reduce the risk of cancer is only very weak, according to a new study.
08 November 2010
Long-term use of vitamin E and C supplements may have only little effect on cataracts among the elderly, a new US study says.
In the randomized controlled trial, 11,545 apparently healthy male physicians aged 50 and above were randomly assigned to receive 400 IU of vitamin E or placebo on alternate days and 500 mg of vitamin C or placebo daily (1). After 8 years of treatment, there was no significant difference in the number of participants diagnosed with cataracts in the group receiving supplements when compared to placebo.
The researchers commented that the participants were generally well nourished, and thus these findings may not apply to the general less well-nourished population. In addition, the duration and timing of the trial may also be an issue of concern: cataracts develop slowly over many years and may require even longer periods of treatment than 8 years, and perhaps treatment at earlier ages. A detailed analysis showed that supplementation with vitamin E or vitamin C had little effect on earlier stages of disease development.
In the United States, an estimated 20.5 million people aged 40 and above show some evidence of age-related cataracts. Nutrition is suspected to be an important factor in cataract development. Because oxidative damage is a prominent feature of cataracts, one focus of nutrition research has been the link between dietary intake of nutrients with antioxidant potential, particularly vitamins E and C, and the risk of developing cataracts.
Data from observational studies generally support the antioxidant hypothesis by indicating an association between high dietary and supplemental intake of vitamins E and C or other antioxidant nutrients and a decreased risk of age-related eye diseases such as cataract and macular degeneration. The results of several randomized controlled trials to date have shown only marginal benefits.
Research also indicates that the need for and efficacy of antioxidant micronutrients may depend on genetic variants: some individuals may be at a higher risk of age-related diseases and more susceptible to positive antioxidant effects than others.