Here’s a meta-analysis that went a step further than the study in my previous post which merely advised “caution” to saying high-dose vitamin E “should be avoided.”
Meta-Analysis: High-Dosage Vitamin E Supplementation May Increase All-Cause Mortality, Annals of Internal Medicine, January 2005
Conclusion: High-dosage (≥400 IU/d) vitamin E supplements may increase all-cause mortality and should be avoided.
A dose–response analysis showed a statistically significant relationship between vitamin E dosage and all-cause mortality, with increased risk of dosages greater than 150 IU/d. … Precise estimation of the threshold at which risk increases is difficult.
What’s the mechanism? Why would taking vitamin E cause people to die sooner? They said:
- Vitamin E may have pro-oxidant effects at high doses.
- Vitamin E may inhibit cytosolic glutathione S-transferases, which help detoxify drugs.
- Vitamin E has anticoagulant properties. (The ATBC Cancer Prevention Study showed a statistically significant increased risk for hemorrhagic stroke among participants assigned to vitamin E.)
- Irregular use of high-dose vitamin E may lead to withdrawal effects, e.g. angina.
Is low-dose beneficial? They said:
The effect of vitamin E in low-dosage studies, however, must be interpreted with caution because these studies were often performed in malnourished populations or used other vitamins or minerals in combination with vitamin E. Further research is needed to determine whether low-dosage vitamin E supplementation is beneficial in western populations.
So, risk may start at just 100 mg (150 IUs is 100 mg). Recall that the upper limit is 1000 mg. Risk occurs at dosages much lower than what the NIH says are safe.