From The November 2001 Issue of Nutrition Science News
by Jack Challem
There is little difference between the natural and synthetic forms of most vitamins. But with vitamin E, natural is better.
On a supplement label, natural vitamin E is listed as d-alpha tocopherol, d-alpha tocopheryl acetate, or d-alpha tocopheryl succinate. In contrast, synthetic forms of vitamin E are labeled with a dl- prefix.
Alpha-tocopherol is the most biologically active form of vitamin E, and its natural form consists of one isomer. In contrast, synthetic alpha-tocopherol contains eight different isomers, of which only one (about 12 percent of the synthetic molecule) is identical to natural vitamin E. The other seven isomers range in potency from 21 percent to 90 percent of natural d-alpha-tocopherol.
This may appear to be arcane nutritional chemistry, but it is key to understanding how the body absorbs natural and synthetic supplements differently. Molecular structure determines how the body uses vitamin E. Researchers have found that natural vitamin E assimilates far better than synthetic versions. Specific binding and transport proteins produced in the liver select the natural d-alpha form of vitamin E and largely ignore all other forms.
In one experiment, Japanese researchers alternately gave natural and synthetic vitamin E to seven healthy young women. It took 300 mg synthetic vitamin E to equal the blood levels achieved by a 100-mg dose of natural vitamin E. 
In other studies at East Tennessee State University, Johnson City, researchers gave a variety of subjects either 30 mg/day or 300 mg/day vitamin E. Each supplement contained half-natural and half-synthetic vitamin E. Both forms were chemically labeled to distinguish one from other vitamin sources.
In blood levels, natural vitamin E increased twice as much as the synthetic form in healthy subjects and pregnant women. In umbilical cords, natural vitamin E levels were three times higher than synthetic vitamin levels.
Blood, however, is not vitamin E's final destination. So in the same study, researchers tracked short-term tissue assimilation of natural and synthetic vitamin E in study participants prior to elective surgery. Tissue takes longer than blood to absorb nutrients, but after seven to 23 days of supplementation, natural vitamin E levels rose higher than synthetic levels. [2 ]
Researchers conducted long-term tissue assimilation studies on two cancer patients. One patient took 30 mg/day half natural, half synthetic vitamin E for one year, and the other took 300 mg/day for almost two years. In both patients, blood and tissue levels of natural vitamin E rose twice as high as the synthetic. 
Researchers at Oregon State University, Corvallis, found the human body excretes synthetic vitamin E three times faster than the natural form. 
Although the international unit (IU) standard for vitamin E was meant to equalize the differences between natural and synthetic vitamin E, studies show otherwise. Last year, the National Academy of Sciences recognized natural vitamin E as the standard by which to judge synthetics. Natural vitamin E contains the molecule humans assimilate most effectively.
Jack Challem, known as the The Nutrition Reporter, has been writing about vitamin research for 25 years and is the author of Syndrome X: The Complete Nutritional Program to Prevent and Reverse Insulin Resistance (Wiley, 2000).
1. Kiyose C, et al.
Biodiscrimination of alpha-tocopherol stereoisomers in humans after oral administration
Am J Clin Nutr 1997 (Mar); 65 (3): 785-9
2. Burton GW, et al.
Human plasma and tissue alpha-tocopherol concentrations in response to supplementation with deuterated natural and synthetic vitamin E
Am J Clin Nutr 1998; 67: 669-84
4. Traber MG, et al.
Synthetic as compared with natural vitamin E is preferentially excreted as a-CEHC in human urine: studies using deuterated a-tocopheryl acetate
FEBS Letters 1998 (Oct 16); 437: 145-8