There are eight forms of vitamin E: four tocopherols (alpha, beta, gamma, delta) and four tocotrienols (alpha, beta, gamma, delta). Alpha-tocopherol is the main source found in supplements and in the European diet, while gamma-tocopherol is the most common form in the American diet.
There have been reports that vitamin E in its tocopherol form may deplete levels of tocotrienols in tissues, but new data published in the journalLipidssuggests that this alpha-tocopherol does not deplete tocotrienols in various tissues, nor does it increase the excretion of their metabolites into urine.
In this study, Japanese researchers fed rats with a gamma-tocopherol-rich diet (containing 150mg gamma-tocopherol/kg) for 6 weeks followed by a gamma-tocopherol-free diet with or without alpha-tocopherol (100mg/kg) for 7 days. In order to investigate the effect of alpha-tocopherol on tocotrienol depletion, researchers fed rats with a tocotrienol-rich diet (containing 103mg alpha-tocotrienol/kg and 150mg gamma-tocotrienol/kg) for 6 weeks followed by a tocotrienol free diet with or without alpha-tocopherol (100mg/kg) for 7 days.
The results showed that dietary alpha-tocopherol did not influence gamma-tocopherol and tocotrienol concentration in the serum and tissues - including liver, adrenal glands, small intestine, heart, muscle as well as adipose tissues.
In addition, the urinary excretion of gamma-tocopherol and tocotrienol metabolites was not affected by dietary alpha-tocopherol.
Commenting on the study’s findings, WH Leong, Vice President of Carotech Inc, said:“Prof. Chandan Sen of OSU Medical Center, in his paper published recently in the Journal of Nutrition, showed that the absorption and distribution of tocotrienols, from Tocomin SupraBio, to vital human organs and tissues were not affected by the presence of alpha-tocopherol. This is the first ever actual human tissue distribution study with tocotrienols.
“I am pleased to see that this latest rat study lends further support that alpha-tocopherol does not interfere with the catabolism of other vitamin E isoforms, including tocotrienols and gamma-tocopherol. It also did not increase the excretion of metabolites of these important vitamin E isoforms.”
Volume 48, Number 7, Pages 687-695
“Alpha-tocopherol does not accelerate depletion of gamma-tocopherol and tocotrienol or excretion of their metabolites in rats”
Authors: T. Uchida T, et al.