The isomeric form of alpha-tocopherol found in foods is RRR-alpha-tocopherol (also referred to as “natural” or d-alpha-tocopherol). Synthetic alpha-tocopherol, which is labeled all-rac- or dl-alpha-tocopherol, has only one-half the biological activity of RRR-alpha-tocopherol (see Supplements). Often vitamin E-fortified foods contain synthetic alpha tocopherol, and the amounts are given as a percentage of the daily value of 30 IU. Throughout this article, amounts of alpha-tocopherol are expressed in both international units (IU) and milligrams (mg).
So, the vitamin E used in soylent, is the synthetic form of vitamin E, not the natural form. It is always your safest bet (if there is not any evidence available) to choose the natural form over the synthetic form. As our body is evolved for thousand of years on those natural forms, common sense tells us, that your body is better adapted to the natural form.
But now the evidence:
The bioavailability of RRR-alpha-tocopherol was greater than that of all-rac-alpha-tocopheryl acetate.
The results indicated that natural vitamin E has roughly twice the availability of synthetic vitamin E.
You may think that this is not a problem. Just increase the dosage of this synethetic form of vitamin E! I’m not sure if that is a good idea. Is has also been shown that this synthetic form of vitamin E depletes an other form of vitamin E in the body. see this study: http://www.ncbi.nlm.nih.gov/pubmed/3998871
This form of vitamin E is called gamma-tocopherol. And is inversely associated with the incidence of cardiovascular disease and prostate cancer.
Some human and animal studies indicate that plasma concentrations of γ-tocopherol are inversely associated with the incidence of cardiovascular disease and prostate cancer. These distinguishing features of l and its metabolite suggest that γ-tocopherol may contribute significantly to human health in ways not recognized previously. This possibility should be further evaluated, especially considering that high doses of α-tocopherol deplete plasma and tissue γ-tocopherol, in contrast with supplementation with γ-tocopherol, which increases both.
No wonder that 400 IU daily of this synthetic version of vitamin E increases the risk of prostate cancer with 17%.