ANH-Intl exposes flaws in study showing increased stroke risk associated with vitamin E
By Adam Smith, Science & Communications Officer, ANH-Intl
Every few months with monotonous regularity, it seems, another study appears in a prestigious, peer-reviewed medical journal that questions the benefits of vitamin supplementation. Never mind the obvious advantages of extra vitamins in an age of restricted diets, due to industrialised agriculture and poor eating habits: the message appears to be, vitamins will kill you or at least do you harm. But, of course, pharmaceutical drugs are exactly what you need to live a happy and healthy life!
After previous supplement-trashing efforts by Miller et al and Bjelakovic et al – the flaws in which were revealed by ANH at the time – a new study in the British Medical Journal (Schürks M et al. BMJ 2010;341:c5702. doi: 10.1136/bmj.c5702) proudly continues this trend. The authors performed a systematic review and meta-analysis of nine randomised, placebo-controlled trials (RCTs) that investigated the effect of vitamin E on stroke risk. Their findings, reported from among a total of 118,765 patients, indicate that vitamin E supplementation increases the risk for haemorrhagic stroke by 22%, and reduces the risk of ischaemic stroke by 10%. Based on these results, the authors caution against the “widespread, indiscriminate use of vitamin E”.
A matter of interpretation
There are different ways of looking at these data, however. The authors themselves go on to point out that the percentage, or relative, risks translate into absolute risks of one additional haemorrhagic stroke for every 1,250 people taking vitamin E, compared with one ischaemic stroke prevented among every 476 individuals taking vitamin E. Because ischaemic stroke is so much more common than haemorrhagic stroke, this begins to look suspiciously like a reduction in the overall stroke risk! The authors are also somewhat mute about the fact that vitamin E is an essential vitamin without which you can’t survive, and they fail to provide a view on the best forms to take – in your food, in supplements or both – or the optimal dose for wellbeing.
The importance of dose and form
With every trial or meta-analysis of trials involving vitamins, it’s always worth checking the doses and types of vitamin used in the studies. The authors looked exclusively for RCTs that examined the effect of alpha-tocopherol on stroke risk, presumably because alpha-tocopherol is the form (isomer) of vitamin E most commonly used in supplements. Out of 22 trials thus identified, they excluded 14 for various reasons, such as lack of a control group or for using tocopheryl nicotinate instead of alpha-tocopherol. However, pertinent as the exclusion criteria certainly are, they do not address a deeper problem with the main search criteria: namely, that alpha-tocopherol is either a highly purified natural form of vitamin E, missing the isomers that accompany it in nature, or, it is a completely synthetic, in a form never found in nature.
Disconcertingly, it’s a synthetic form of vitamin E found, often in inadequate quantities, in our diets. That honour goes to gamma-tocopherol, the main form of vitamin E found in good-quality vegetable oils, including olive oil,and high-quality vitamin E supplements. And wait for this: absorption of gamma-tocopherol is actually reduced in people taking high-dose alpha-tocopherol supplements. Interestingly, the paper alludes to the different properties of vitamin E molecular forms, by making a distinction between “natural source” and “synthetic” forms of vitamin E. Unfortunately, the authors classified “natural source” as a highly purified form of alpha-tocopherol and “synthetic” as a mixture of different subtypes of alpha-tocopherol!
Importantly, in this review, the studies included in the analysis were mostly of high-dose alpha-tocopherol supplements. Apart from one study among smokers – who were given 50 mg vitamin E/day – doses ranged from 270 mg/day to 540 mg/day. To put this in context, these levels are around 4 to over 22 times the European recommended daily allowance (RDA) of alpha-tocopherol, which is 12 mg.
Two serious flaws
So, thus far, we potentially have two quite serious problems with this paper. Firstly, in examining the effects of vitamin E on stroke risk, it describes a reduction in the overall risk of haemorrhagic and ischaemic stroke as an increase; and secondly, the papers it chooses for the analysis concern a non-food matrix, highly purified or, synthetic molecular form of vitamin E that may acts as a pro-oxidant in the high doses used in those studies.
Synergy in nature
When considering supplementation of any vitamin or mineral, it is important to consider both the form of the vitamin being taken and the effects of synergy – or positive interactions – between itself, associated nutrients and the body. The case of vitamin E is similar to that of pro-vitamin A carotenoids: both occur in nature as families of different molecular forms (tocopherols/tocotrienols and carotenoids, respectively), which should be consumed in their natural complexes as nature intended. Vitamin E found in many high-quality supplements is not usually provided in the combinations or proportions found in nature.
To ensure that you are consuming full-spectrum, natural vitamin E in supplements, have a look at the label or associated marketing materials.You’ll generally see a full breakdown of four tocopherols and four tocotrienols listed on the Nutrition/Supplement Facts or ingredients listing: these are the 8 main isomers of vitamin E. You may also see the phrase “mixed tocopherols and tocotrienols” or similar listed as an ingredient on the product label.
A predictable recommendation
Getting back to the paper, the kicker comes right near the end. What do the authors suggest as alternatives to the killer substance, vitamin E, for reducing stroke risk? Why, our old friends “antihypertensive medication” and “lipid-lowering medication”, otherwise known as beta-blockers, acetylcholinesterase (ACE) inhibitors and statins, among others. It's up to you to decide whether a lifetime spent popping these pills is worth it, given their increased risks of muscle damage, liver, kidney and heart problems and cataracts. We’ll pass, though, thanks – and bring on the vitamin E!
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