OTTAWA, CANADA. A team of American and Canadian researchers has released a major report that conclusively proves that natural vitamin E is absorbed at about twice the rate of synthetic vitamin E. The researchers tested the biological activity (bioavailability) of a labelled (deuterated) mixture of natural and synthetic vitamin E in a variety of subjects. They noted that a 30 mg daily dose (as found in most multivitamin tablets) caused only a very slight increase in the vitamin E concentration in blood plasma whereas a daily dose of 300 mg of tocopheryl acetate (about 400 IU) increased plasma content by 50 per cent after one day and 100 per cent after eight consecutive days of supplementation. Biopsy results showed that vitamin E (alpha-tocopherol) concentrations in the body are highest in blood plasma and the liver followed by the gallbladder, the veins, skin, muscle, and adipose (fat) tissue; the lowest vitamin E concentrations were found in the nerves. The researchers also found that gamma-tocopherol is quite abundant in fat tissue (31 per cent of all vitamin E), muscle tissue (38 per cent), and skin (53 per cent). They conclude that the current "official" assumption that it takes 136 mg of synthetic vitamin E to equal 100 mg (100 IU) of natural vitamin E is in error and should be replaced by the assumption that 100 mg of natural vitamin E is equivalent to 200 mg of the synthetic version. Dr. Max Horwitt of the St. Louis University School of Medicine sums up the team's findings in the following terms: 100 mg of natural alpha-tocopherol (d-alpha- tocopherol) is equivalent to 100 IU of vitamin E; 100 mg of natural d-alpha-tocopheryl acetate is equivalent to 91 IU of vitamin E; 100 mg of synthetic alpha-tocopherol (dl-alpha- tocopherol) is equivalent to 50 IU; and 100 mg of synthetic dl-alpha-tocopheryl acetate is equivalent to 45.5 IU of vitamin E. NOTE: This work was supported in part by grants from the Natural Source Vitamin E Association and the National Foundation for Cancer Research.
Burton, Graham E., et al. Human plasma and tissue alpha-tocopherol concentrations in response to supplementation with deuterated natural and synthetic vitamin E. American Journal of Clinical Nutrition, Vol. 67, April 1998, pp. 669-84
Horwitt, Max K. My valedictory on the differences in biological potency between RRR- alpha-tocopheryl and all-rac-alpha-tocopheryl acetate. American Journal of Clinical Nutrition, Vol. 69, February 1999, pp. 341-42