increase oxidative stress.4
Yet population studies show that individuals with diets high in Vi- tamin E fare better, with lower cardiovascular disease and mor- tality. A consensus is emerging that we should follow nature— she offers us eight different frac- tions of Vitamin E, and all of them are good for us.
Because alpha-tocopherol has its own transport protein, it is pref- erentially absorbed, and when it is given in excessively high dos- es, it can interfere with absorp- tion of tocotrienols. But does al- pha-tocopherol actually prevent us from absorbing tocotrienols, period? According to Chandan Sen, concerns about alpha-to- copherol are primarily based on a 1997 finding that “the transport system, TTP, responsible for car- rying tocopherol to vital organs has a poorer efficiency to trans- port tocotrienols to tissues. The lack of relative specific affinity of TTP for tocotrienols led to the ‘urban legend’ that availability of dietary tocotrienol to vital organs is negligible.”5,6
Yet biology is never that simple. It turns out that nature didn’t just create one pathway by which Vi- tamin E fractions could do their work. New research shows there are other, as yet undiscovered pathways by which tocotrienols can be absorbed. This was stun- ningly obvious when a study of mice without the TTP gene (thus unable to efficiently absorb al- pha-tocopherol, and theoreti-
cally, unable to reproduce), had their fertility restored. How? By supplementing with alpha-to- cotrienol. The tocotrienol was successfully delivered to the rel- evant tissues and the mice repro- duced. When scientists discover that as-yet-unknown pathway for
tocotrienols, a whole new branch of research may open.
In addition, tocotrienols can im- pact biology at far lower doses than tocopherols—a little goes a long way. As Chandan Sen notes in his interview elsewhere in this issue (see pp 9), alpha-tocopher- ol can be measured in micromo- lars in blood, while tocotrienol can be found in the nanomolar range—a thousandth less, and yet potent and effective. “It is clear,” says Sen, “that natu- ral isomers of vitamin E do get transported to vital organs even in the absence of TTP.”
Absorption and excretion of to- cotrienols can be an issue, how- ever. According to a 2012 review from the Institute of Biological Chemistry and Nutrition, the low bioavailability and rapid excre- tion of tocotrienols represents a major hurdle in their preventive use…bioavailability may be en- hanced by ingestion with a high- fat meal, self-emulsifying deliv- ery systems, or phytochemicals that inhibit their metabolism and excretion.7
“In a study investi-
gating the pharmacokinetics and bioavailability of tocotrienols un- der fed and fasted conditions in eight healthy volunteers,” Chan- dan Sen reports, “the postab-
sorptive fate of tocotrienol iso- mers and their association with lipoprotein subfractions were examined.” Peak plasma con- centrations of tocotrienols were two to three times higher using self-emulsifying blends than the peak concentrations report- ed in previous studies using ge- neric tocotrienols.6,8,9
The take-away? All isomers of Vitamin E have benefit. Although alpha-tocopherol has preferred absorption in the body, tocot- rienols have another, as-yet-un- identified way of delivering themselves to cells. In addition, tocotrienols are potent at lower doses than tocopherols. Finally, special delivery systems protect tocotrienols further from poten- tial competitive inhibition by alpha-tocopherol, and insure a consistant and increased absorp- tion of tocotrienols.
References:
1. Lonn E, Bosch J, Yusuf S, Sheridan P, Pogue J, Arnold JM, Ross C, Arnold A, Sleight P, Prob- stfield J, Dagenais GR; HOPE and HOPE-TOO Trial Investigators. Effects of long-term vitamin E supplementation on cardiovascular events and cancer: a randomized controlled trial. JAMA. 2005 Mar 16;293(11):1338-47.
2. Miyamoto K, Shiozaki M, Shibata M, Koike M, Uchiyama Y, Gotow T. Very-high-dose alpha-to- copherol supplementation increases blood pres- sure and causes possible adverse central nervous system effects in stroke-prone spontaneously hy- pertensive rats. Neurosci Res. 2009 Feb;87(2):556- 66. doi: 10.1002/jnr.21851. PMID: 18942769.
3. Schürks M, Glynn RJ, Rist PM, Tzourio C, Kurth T. Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. BMJ. 2010 Nov 4;341:c5702. doi: 10.1136/bmj. c5702. PMID: 21051774
4. de Oliveira BF, Veloso CA, Nogueira-Machado JA, Martins Chaves M. High doses of in vitro be- ta-carotene, alpha-tocopherol and ascorbic acid induce oxidative stress and secretion of IL-6 in peripheral blood mononuclear cells from healthy donors. Curr Aging Sci. 2012 Jul;5(2):148-56. PMID: 22894740
5. Hosomi A, Arita M, Sato Y, Kiyose C, Ueda T, Igarashi O, Arai H, Inoue K. Affinity for al- pha-tocopherol transfer protein as a determinant
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