By Lucy Piper, Senior medwireNews Reporter
Long-term daily use of multivitamins could help to reduce the risk of cataracts, but has no effect on the risk of visually significant age-related macular degeneration (AMD), suggests research.
Considerable observational evidence has pointed towards lower rates of cataract and AMD in people with higher dietary intake or blood levels of nutrients with antioxidant capabilities, note the study authors, led by William Christen (Harvard Medical School, Boston, Massachusetts, USA).
But in their study of 14,641 US male physicians aged at least 50 years, daily multivitamin use for an average of 11.2 years reduced only the risk of cataracts, by a significant 9% in 5736 men versus placebo taken by 5761 men. This was particularly evident for the 175 men with the nuclear sclerosis subtype, for which multivitamin use was associated with a 13% reduced risk.
The findings indicate a “small to moderate beneficial effect on risk of cataract, particularly nuclear cataract”, the researchers comment in Ophthalmology.
“Given that an estimated 10 million adults in the United States have impaired vision due to cataract, even a modest reduction in risk of cataract would have a large public health impact”, they say.
The benefits of daily multivitamin use were greater in older than younger men, and were independent of baseline characteristics, such as cigarette smoking, alcohol use, body mass index and history of hypertension, high cholesterol or diabetes.
By contrast, taking daily multivitamins did not have a beneficial effect on the risk of AMD. Indeed, the 7111 men taking supplements had a nonsignificant 19% increased risk of visually significant AMD, compared with the 7122 men taking placebo. There was also a significant 22% increased risk of total AMD and a nonsignificant 22% increased risk of advanced AMD.
Christen and colleagues suggest that this lack of benefit may be partly due to the dose of multivitamin being too low or because their study population had a low risk profile.
They therefore recommend further confirmation of the effects of multivitamin use in visually significant AMD in other populations of men and women.
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