Simin Nikbin Meydani, DVM, PhD; Joseph Lau, MD; Gerard E. Dallal, PhD; Mohsen Meydani, DVM, PhD
Potential Financial Conflicts of Interest: None disclosed.
Meydani S., Lau J., Dallal G., Meydani M.; High-Dosage Vitamin E Supplementation and All-Cause Mortality. Ann Intern Med. 2005;143:153. doi: 10.7326/0003-4819-143-2-200507190-00023
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Published: Ann Intern Med. 2005;143(2):153.
TO THE EDITOR:
Miller and colleagues (1) reported that supplemental intake of vitamin E at dosages greater than 150 IU/d progressively increases all-cause mortality. There are several problems with their analysis and interpretation of the data. The harmful effect above 150 IU/d is an artifact of the model they chose to fit. When researchers fit a quadratic-linear spline, the result must be a quadratic-linear spline regardless of whether the data behave that way. In another reasonable model, the favorable response to vitamin E is constant until a certain dose, above which the change in all-cause mortality risk difference is linear. The constant response to vitamin E persists up to a dosage of 330 IU/d, and the risk difference favors vitamin E until the dosage is 400 IU/d. The sum of weighted squared differences between observed and predicted all-cause mortality risk differences shows that this model fits the data better than does the quadratic-linear spline.
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