Killer Anti-Oxidant Vitamins: When Excess Could Be Exceedingly Dangerous

Vitamin E today ranks as the second highest single vitamin consumed in the world after vitamin C, following well organized marketing campaigns extolling its anti-oxidative properties. Anti-oxidation is today a key marketing buzzword for the growing market segment of anti-aging dietary supplements, although how it affects human life spans is poorly understood. According to Wellcome Trust [1] there is no evidence in humans that anti-oxidative vitamins (A, C and E) slows aging; only in laboratory mice have they led to a sight increase in lifespan. Nevertheless, these vitamins are widely sold today without prescription as tablets, fish oils and capsules across chemists, superstores and even eBay.

Brand new research [2] from a study of over 77,000 people has shown that higher than recommended doses of Vitamin E can lead to a “significant” increase in the risk of developing lung cancer, irrespective of whether they smoked or not. The strength of the findings was somewhat unexpected — a 7% rise in lung cancer for every extra 100 mg of Vitamin E taken daily for 10 years. With an average daily Vitamin E supplement of 400 mg, this could mean a 28% excess risk for someone to develop lung cancer taking just one pill a day.

An important question is: do we need Vitamin E supplementation at all on top of an average diet? The UK Food Standard Agency website estimates daily dietary requirements of Vitamin E to be just 4 mg for men and 3 mg for women. It also mentions that not enough is known about the side-effects of high-dose vitamin E supplements, and that 540 mg or less a day is “unlikely” to be harmful. This new study could change all that.

While the protective effects of Vitamin E against heart disease and many forms of cancer are acknowledged, dietary deficiency is rare today [3]. This is mainly related to the fact that vitamin E intake in modern diets is mainly dependent on polyunsaturated fatty acids, and with diets rich in vegetable oils and green leafy vegetables, the amount of daily vitamin E intake could well exceed 20-40 mg — just a tablespoon of sunflower oil has 6 mg, while wheatgerm oil has 20 mg or so.

Do we actually need any extra vitamin E supplements if we can make up for our daily requirement through diet? An editorial from the American Journal of Clinical Nutrition in 2006 [4] concluded that intervention studies did not support a beneficial effect of antioxidant supplements, and there was a growing body of evidence that with anti-oxidant vitamins, “just enough” was more than adequate. About 15 mg per day of Vitamin E was enough to provide us with maximum protection against chronic disease, according to the journal.

Death ValleyThe debate about Vitamin E supplementation as a potential cause of premature death is however not new. In 2004, the Times [5] reported the results from a John Hopkins study [6] that pooled the result of 19 studies on vitamin E supplementation worldwide. The study found that doses of 400 international units (IU) of Vitamin E, “often the equivalent of a single capsule were associated with a 10% increased risk of death.” Ominously, the study found that many people were taking as much as 400-800 mg of Vitamin E a day. Even the Lancet had earlier estimated that out of a million people taking Vitamin E supplements, 9,000 were expected to die premature deaths.

The question therefore is not “if,” but rather “how much.” Supplementation can increase the intake of Vitamin E by up to a hundred times of that of daily requirements, and as the latest study shows, the increase in risk of lung cancer can also be substantial. Dietary adjustment can well increase our intake of Vitamin E to well above our recommended daily allowances. The question therefore remains: is it at all justifiable to use “killer” doses of a supplement that has no demonstrable benefits at all above its physiological limits?


1. Wellcome Trust. Anti-ageing treatments.

2. Byers, T. (2007). Nutrition and Lung Cancer: Lessons from the Differing Effects of Foods and Supplements. American Journal of Respiratory and Critical Care Medicine, 177(5), 470-471. DOI: 10.1164/rccm.200711-1681ED

3. British Nutrition Foundation. (2004). Vitamins.

4. Traber, M.G. (2006). How much vitamin E? … Just enough! American Journal of Clinical Nutrition, 84(5), 959-960.

5. Lister, S. (2004). The vitamin boost that could cause early death. TimesOnline.

6. MILLER, E., PASTORBARRIUSO, R., DALAL, D., RIEMERSMA, R., APPEL, L., GUALLAR, E. (2005). Meta-Analysis: High-Dosage Vitamin E Supplementation May Increase All-Cause Mortality. ACC Current Journal Review, 14(5), 17-17. DOI: 10.1016/j.accreview.2005.04.017

Sudip Ghosh, MD

Sudip Ghosh, MD, is a surgeon at the University of Manchester, UK and a medical writer.
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