Over half of US adults take vitamins and supplements, many with the hopes of preventing chronic medical conditions such as cardiovascular disease and cancer, despite a growing body of evidence that suggests such benefits are lacking. Much like the case with vitamin D, the issue of potential health benefits associated with multivitamin use remains controversial, and many clinical studies continue to investigate the topic.
This week, a study released in Ophthalmology examines the relationship between multivitamins and vision, with mixed results. The researchers found there may be a small beneficial effect on the prevention of cataracts, but no beneficial effect on the prevention of age-related macular degeneration.
Researchers at Harvard Medical School looked at final data from the Physicians’ Health Study II, a large randomized trial that began in 1999 with a group of over 14 000 male physicians. About half of these physicians were randomly assigned to take a daily multivitamin and the other half were assigned to take a placebo. During the 11 years of follow-up, a large number of health outcomes were investigated, including the development of cataracts and age-related macular degeneration.
Based on the physicians’ self-report, which was then confirmed by medical records, there were 1817 cases of cataracts during the follow-up period, 872 in the multivitamin group, and 945 in the placebo group. This translated into a 15.2% rate of cataracts in the multivitamin group vs a 16.4% rate in the control group, a small but statistically significant difference given the large number of individuals in the trial. There was no difference in the rates of age-related macular degeneration in the 2 groups.
The authors stated that even if the magnitude of benefit of taking multivitamins for cataract prevention is small, given that 10 million adults in the United States have impaired vision due to cataracts, the public health implication may still be important. However, these results are not strong enough to make a definitive conclusion about the effects of multivitamins on vision in the general population, and given conflicting results from previous studies looking at both cataracts and macular degeneration in relation to multivitamin use, further research is needed, they said.
In November 2013, the US Preventive Services Task Force issued a draft statement about multivitamin supplements that states there is currently insufficient evidence to make a recommendation regarding the use of multivitamins for the prevention of cardiovascular disease and cancer. No other specific health conditions are mentioned in this statement.