By David Liu, PHD

Thursday May 2, 2013 (foodconsumer.org) -- Low vitamin E in the blood has been associated with increased cancer risk.  But some large scale human trials show that high doses of alpha-tocopherol do not seem to have a protective effect against cancer.

A new study led by Chung S. Yang and Nanjoo Suh and published in Topics in Current Chemistry has confirmed that not all forms of vitamin E prevent cancer.   To be specific, delta- and gamma-tocopherols, but not alpha -tocopherol are effective in preventing cancers.

Early studies by the same authors show that a naturally occurring tocopherol mixture which is high in gamma-tocopherol inhibits chemically induced lung, colon and mammary cancers and the growth of xenograft tumors originated from human lung and prostate cancer cells.

The authors say that the natural vitamin E mixture has the anticancer activity because they are able to trap reactive oxygen and nitrogen species and inhibit arachidonic acid metabolism.  In preventing mammary cancer development, vitamin E can activate peroxisome proliferator-activated receptor γ and inhibit estrogen signaling.

Additionally, δ-tocopherol seems more potent than γ-tocopherol in inhibiting the growth of human lung cancer cells in a xenograft tumor and the development of aberrant crypt foci in rats treated with azoxymethane. Alpha-tocopherol does not work in these models. 

Food consumers should make sure that the vitamin E supplement they use is a natural delta- or gamma-tocopherol or a natural mixture of tocopherols.  It should not be a mixture of synthetic vitamin E or inactive alpha-tocopherol.