Natural Health News — Long-term daily multivitamin supplement use may lower cataract risk in men, according to a new study.
Past observational studies have indicated a relationship between nutritional supplement use and eye health. However, randomized trial data on the effects of long-term multivitamin supplement use and risk of eye diseases are can be thin on the ground.
To address this, researchers based at Brigham and Women’s Hospital and Harvard Medical School – as part of the Physicians’ Health Study II (PHS II) – conducted a randomised, double-blind study of 14,641 US male doctors age 50 and older.
Half took a common daily multivitamin, as well as vitamin C, vitamin E and beta carotene supplements. The other half took a placebo.
The researchers followed the participants from 1997 to 2011 to see how many in each group developed new cases of two common eye diseases: cataract, which is a clouding of the eye’s lens, and age-related macular degeneration (AMD), the deterioration of the eye’s macula that is responsible for the ability to see fine details clearly.
The results were published in the journal Ophthalmology.
Good news for cataracts
The result showed that in the placebo group 945 cases of cataract developed, which were self-reported and confirmed by medical records, while only 872 cases of cataract developed in the multivitamin group, representing a 9% decrease in risk.
This risk was even lower, at 13%, for nuclear cataract, which occurs at the centre of the lens and is the most common variety of cataract associated with the ageing process.
The current study only looked at men, but in 2008 a study found that higher dietary intake of lutein/zeaxanthin and vitamin E, from food and supplements, significantly reduced the risk of cataracts in women.
A growing problem
The World Health Report published in 1998 by the World Health Organization estimated that there were 19.34 million people who are bilaterally blind (less than 3/60 in the better eye) from age-related cataract. This represented 43% of all blindness. The number of blind people in the world and the proportion due to cataract is increasing due to population growth and increasing longevity. These figures it said would hold true for less economically developed countries as well as the industrialised world.
These figures have not improved. The WHO now calculates that cataract is responsible for 51% of world blindness, which represents about 20 million people.
“If multivitamins really do reduce the risk of cataract, even by a modest 10%, this rather small reduction would nonetheless have a large public health impact,” said William Christen, ScD, the study’s lead author and researcher from Harvard Medical School.
Not enough to prevent AMD
In terms of AMD risk, the researchers found there were 152 new cases of visually significant AMD in the multivitamin group compared to 129 in the placebo group, but the difference was not considered statistically significant.
While this finding may seem to contradict results of other studies, such as Age-Related Eye Disease Study (AREDS) – long considered the gold standard for nutritional research into AMD – the researchers note that the studies had different nutrient supplements, dosing and objectives.
AREDS included daily zinc and a high-dose antioxidant combination of vitamin E, vitamin C and beta carotene, and found that these reduced the risk of developing advanced age-related macular degeneration (AMD) by about 25%.
The supplement in PHS II included these nutrients at much lower doses, alongside many others, which were given at US Recommended Dietary Allowance dose levels, which are the minimum necessary to prevent deficiency, rather than the optimum needed to maintain health.
The American Academy of Ophthalmology recommends the use of antioxidant vitamin and mineral supplements as recommended in the AREDS reports, including high daily doses of vitamin C, vitamin E, beta-carotene, zinc and copper only for patients who have intermediate or advanced AMD.
Current smokers and patients with a smoking history should take advice before taking beta-carotene because of the potential for an increased risk of lung cancer. The recent AREDS2 results would suggest other nutrients such as lutein and zeaxanthin may be an appropriate substitution for beta-carotene in the formulation.
In spite of these good outcomes, The Academy does not yet have a recommendation for the use of nutritional supplements to prevent cataracts or delay their progression.
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