Vitamin review offers balanced perspective to recent negative findings17 years ago
Posted on Apr 20, 2005, 4 p.m.
By Bill Freeman
A review of the evidence on vitamins C and E, currently one of the most controversial nutritional products, will give industry support following the safety questions raised by recent studies.Published in this month's issue of the American Journal of Clinical Nutrition (vol 81, no 4, pp736-745), leading vitamin experts including Lester Packer, Maret Traber and Frank Kelly study the evidence for the two vitamins and conclude that vitamin E supplements appear safe for most adults in amounts of 1600 IU and that vitamin C supplements of 2000 mg per day are also safe for most adults.
Published in this month's issue of the American Journal of Clinical Nutrition (vol 81, no 4, pp736-745), leading vitamin experts including Lester Packer, Maret Traber and Frank Kelly study the evidence for the two vitamins and conclude that vitamin E supplements appear safe for most adults in amounts of 1600 IU and that vitamin C supplements of 2000 mg per day are also safe for most adults.
The review offers some balance to recent negative findings on vitamin E that have had some negative impact on consumer confidence and sales, particularly in the US.
A meta-analysis released last autumn by the Annals of Internal Medicine concluded that daily dosages of 400 IU of vitamin E or more can increase the risk of death and should be avoided.
However critics have noted that combining studies that did not use consistent forms or doses unfairly added variables while ignoring positive effects of the vitamin. Also, the authors themselves acknowledged that their findings do not apply to healthier populations and are not definitive.
The new review states that after adjusting for variables in supplementation, the actual dose of vitamin E that may have been slightly harmful to these seriously ill patients was statistically significant only at levels where patients took over 2,000 IU per day, well above the 400 IU suggested by the original Annals analysis.
Neil Levin, a member of the International & American Associations of Clinical Nutritionists and nutrition educator, also notes that a recent JAMA article on vitamin E again used very sick patients but subjected positive data on vitamin E’s benefits to different, more stringent statistical methods than the 'skimpy negative data' to produce another negative result.
In a press release on the new AJCN report, he writes: "The National Institute of Medicine’s safe upper limit of 1,500 IU per day of natural vitamin E is based on their own expert review of hundreds of well-designed studies."
He points to the trial being run by the US government's National Institutes of Health (NIH), looking at the long-term use of selenium and vitamin E on prostate cancer prevention. Called SELECT, the multi-centre, long-term, double-blind, randomized trial includes 35,534 men taking 400 IU of vitamin E daily.
NIH researchers carefully examined the data from recent negative reports and decided not to change their protocol, still believing that vitamin E at this dose is unlikely to cause any harm to their patients, said Levin.
Further, two large observational studies (the Nurses' Health Study and the Health Professionals Follow-up Study) have found that people taking vitamin E supplements of 400 IU or more for at least two years had between 20-40 per cent reduction in coronary heart disease.
And in the GISSI Prevention Trial of 11,000 heart attack survivors, vitamin E reduced the number both of sudden deaths and deaths due to cardiovascular disease.
"The scientific method of giving only one isolated nutrient has generated some brutal publicity for individual members of the antioxidant 'family' because antioxidants function inter-dependently," writes Levin.
He cites beta-carotene as an example, found in one study to put smokers at greater risk of lung cancer. A more thorough follow-up analysis - looking at their diet plus other dietary supplements taken - revealed that the smokers’ actual danger was due to low total antioxidant levels.
People should not try to take a high dose of any one supplement without considering that it may increase their need for other nutrients, adds Levin. And elderly, sick people especially need a more holistic approach, rather than using a single nutrient in high doses as if it were a drug.
He concludes that there is no published evidence that the average person taking a mixture of antioxidants is at greater risk of any disease, but plenty of studies show that people eating a variety of antioxidant nutrients receive some protection from various diseases.
"In the case of antioxidants, there is safety in numbers."