Vitamin E is an antioxidant whose main tasks are to limit free radical production and activity and to help with immune system functioning, cell signaling, and various metabolic processes. Vitamin E is actually not one substance but a group of chemically related, naturally occurring substances called tocopherols and tocotrienols. Alpha-tocopherol is perhaps the best known of the group; the other forms are beta-, gamma-, and delta-tocopherol; and alpha-, beta-, gamma-, and delta-tocotrienol.
Although alpha-tocopherol is the most common form of vitamin E found in supplements and also the one used in many of the studies, recent research has shown that gamma-tocopherol has excellent antioxidant abilities and may help fight prostate cancer. Scientists have also found that gamma-tocopherol functions independently as well as synergistically with the alpha-tocopherol form of vitamin E. Some studies have also shown that taking high doses of supplemental alpha-tocopherol can deplete levels of gamma-tocopherol in the body. One clinical prostate health supplement, Prost P10x, contains substantially less d-alpha-tocopherol (18 IU, or about 16 mg) than gamma-tocopherol (120 mg) and maintains the correct ratio for maximum prostate health.
Alpha-Tocopherol vs Gamma-Tocopherol
Gamma-tocopherol is a form of vitamin E that is lacking in almost all commercial vitamin E supplements. Yet gamma-tocopherol is critically important, because while alpha-tocopherol inhibits the production of free radicals, it is the gamma-tocopherol that is required to trap and neutralize free radicals.
A study published in the Proceedings of the National Academy of Sciences USA evaluated how gamma-tocopherol and alpha-tocopherol protect against peroxynitrite-induced lipid oxidation. Peroxynitrite is a powerful oxidant that is formed by a reaction of nitric oxide and superoxide during activation of cells called phagocytes, which are involved in chronic inflammation and thus a major contributor to cancer and other degenerative diseases. The study’s authors discovered that gamma-tocopherol was more effective at inhibiting lipid hydroperoxide formation than was alpha-tocopherol. They concluded that “because large doses of dietary alpha T [tocopherol] displace gamma T in plasma and other tissues, the current wisdom of vitamin E supplementation with primarily alpha T should be reconsidered.” (Christen 1997)
Alpha-Tocopherol, Gamma-Tocopherol, and Prostate Cancer
In a study conducted in 1989, a total of 10,456 males donated blood for a specimen bank. Plasma and toenail samples to determine levels of selenium, alpha-tocopherol, and gamma-tocopherol were available from 117 of 145 men who developed prostate cancer and 233 matched controls. Overall, the investigators found that men who had the highest blood levels of gamma-tocopherol were five times less likely to develop prostate cancer than men who had the lowest levels. Researchers also observed that alpha-tocopherol and selenium protected against prostate cancer only when gamma-tocopherol intake was high. They concluded that given their findings,“the use of combined alpha- and gamma-tocopherol supplements should be considered in upcoming prostate cancer prevention trials.” (Helzlsouer 2000)
This information is important when men consider the results of the Selenium and Vitamin E Cancer Prevention Trial (SELECT), which the National Cancer Institute stopped early because the results showed a small but not statistically significant increase in the number of cases of prostate cancer among the more than 35,000 men age 50 and older in the study who were taking vitamin E only. (Lippman 2009) However, the vitamin E used in SELECT was alpha-tocopherol rather than gamma-tocopherol or a combination of both alpha- and gamma-tocopherol, which may explain the small increase in the number of prostate cancer cases. Read more on the SELECT Trial and Vitamin E
A review published in Carcinogenesis in September 2009 noted that studies on alpha-tocopherol in animals have not shown significant anti-cancer effects, and that one possible explanation may be that high doses of alpha-tocopherol reduce the body’s levels of gamma- and delta-tocopherols. (Ju 2009) These findings support those of the earlier Helzlsouer study with evidence that gamma-tocopherol, which has strong anti-inflammatory abilities, is a more effective anti-cancer form of vitamin E than alpha-tocopherol.
Other studies have also shown vitamin E to be helpful in the fight against prostate cancer. A 2006 trial, for example, reported that vitamin E significantly suppressed the multiplication of prostate cancer cells and also prompted them to “commit suicide.” (Malafa 2006) In the Alpha-Tocopherol Beta-Carotene Cancer Prevention Trial, which examined 29,133 male smokers in Finland, the investigators found that taking 50 mg of alpha-tocopherol daily for five to eight years could reduce the risk of developing prostate cancer by 32 percent, and the risk of dying from the disease by 41 percent. (Syed 2007)
In an Italian study, researchers found a significant relationship between intake of vitamin E and a reduced risk of prostate cancer. (Bidoli 2009) The study included 1,294 men who had prostate cancer and 1,451 healthy controls. Information about vitamin E intake was gathered from a food frequency questionnaire. The investigators found that dietary intake of vitamin E was associated with a reduced incidence of prostate cancer. It’s significant to note here that the authors’ findings likely reflect the influence of diet rather than supplementation, since taking vitamin supplements is not a common practice among the Italian population.
It is suggested that men get their vitamin E from food or, if taking a supplement, to take gamma-tocopherol or a supplement that contains a combination of the two. The RDA for vitamin E is 15 mg (22.4 IU) for adults. Vitamin E is found primarily in nuts, sunflower seeds, and various vegetable oils.
Bidoli E et al. Dietary vitamins E and C and prostate cancer risk. Acta Oncol 2009; 48(6): 890-94
Christen S, et al. gamma-tocopherol traps mutagenic electrophiles such as NO(X) and complements alpha–tocopherol: physiological implications. Proc Natl Acad Sci U S A 1997 Apr 1;94(7):3217-22
Helzlsouer KJ et al. Association between alpha-tocopherol, gamma-tocopherol, selenium, and subsequent prostate cancer. J Natl Cancer Inst 2000; 92:2018-23.
Ju J et al. Cancer preventive activities of tocopherols and tocotrienols. Carcinogenesis 2009 Sep 11.
Lippman SM et al. Effect of Selenium and Vitamin E on Risk of Prostate Cancer and Other Cancers: The Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 2009 Jan; 301(1):39-51.
Malafa MP et al. Vitamin E succinate suppresses prostate tumor growth by inducing apoptosis. Int J Cancer 2006; 118(10):2441-47.
Syed DN et al. Chemoprevention of prostate cancer through dietary agents: progress and promise. Cancer Epidemiol Biomarkers Prev 2007; 16(11):2193-2203.