Natural vs Synthetic
Until recently, a debate raged about whether natural versus synthetic alpha-tocopherol was better. Now it is generally accepted that natural alpha-tocopherol is twice as bioavailable as synthetic. We'll explain later, but be careful because the majority of vitamin E produced and sold is synthetic alpha-tocopherols.
It is important to note that synthetic vitamin E only refers to one member of the vitamin E family - alpha-tocopherol. None of the other members are commercially produced as synthetic compounds. In addition, none of the other compounds are sold commercially as an individual compound, such as just beta-tocopherol. So this debate only refers to alpha-tocopherol, which is only one member of the family.
To understand the dilemma, it is important to understand the history. Vitamin E was first discovered in 1922 by Dr. Evans (embryologist) and Karen Bishop, his assistant, who were feeding laboratory rats a semipurified diet at the University of California at Berkeley. They noted that female rats fed this diet would become pregnant but fetuses would die in utero. However, supplementation of the semipurified diet with fresh lettuce or wheat germ resulted in healthy offspring. Obviously, there was some compound missing in the semi-purified diet that is present in wheat germ or lettuce. Dr. Evans named this compound Factor X and isolated it in 1936. In 1938, Dr Fernholtz identified the chemical structure and Hoffman-LaRoche synthesized Factor X - named tocopherol (not alpha- tocopherols which was later added to differentiate it from the other vitamin E family members).
Since vitamin E was thought to aid in reproduction and because alpha-tocopherol was later found to be the most potent in the clinical assays measuring this property, alpha-tocopherol became synonymous with Vitamin E.
Synthetic alpha-tocopherol is different than natural alpha-tocopherol. The reason is that synthetic alpha-tocopherol is a combination of eight different isomers while natural alpha-tocopherol is only found as one isomer (RRR-alpha-tocopherol or d- alpha-tocopherol). Actually only 12.5% of synthetic vitamin E is RRR or d-alpha-tocopherol. Do not confuse this with the eight family members that include the different tocopherols and tocotrienols - here we are talking about eight conformations not only alpha-tocopherol. The body absorbs the natural alpha-tocopherol (RRR or d) the best. Since the synthetic form includes eight isomers (also called allrac or dl-alpha-tocopherol), the body cannot absorb the other isomers as readily as the RRR-alpha-tocopherol. This results in a decreased bioavilability (the amount the body can use) of synthetic versus natural.
d is for natural (example d-alpha-tocopherol)
dl is for synthetic (example dl-alpha-tocopherol)
Until recently, organizations such as the Food and Drug Administration and the World Health Organization have recognized that the natural form is 1.36 times more bioavailable than the synthetic form. However, research conducted at the National Research Council of Canada has shown that the natural form is actually 2 times as bioavailable as the synthetic form.
Natural doesn't mean much when it comes to vitamins, with vitamin E probably the only exception.... -The New York Times, February 3, 1993
The results indicated that natural Vitamin E has roughly twice the availability of synthetic Vitamin E. - Dr. Graham W. Burton, National Research Council of Canada