Vitamin E and Antioxidants
As a holistic veterinarian, I feel it is incredibly important to take the whole animal into consideration when it comes to nutrition. And, whenever practical, my preference is to provide nutrients, minerals and vitamins in their natural forms. In this post, I’d like to talk to you specifically about vitamin E, to review both the strengths and weaknesses of natural and synthetic forms.
Vitamin E is an incredibly complex and important nutrient that, among other things, functions as an antioxidant. Antioxidants are naturally occurring nutrients that promote health by slowing the destructive aging process of cells (a breakdown called “peroxidation”). In peroxidation, damaged molecules known as free radicals steal pieces from other cells, like fat, protein or DNA. The damage can spread, damaging and killing entire groups of cells. While peroxidation can be useful to destroy old cells or germs and parasites, when left unchecked, free radicals produced by peroxidation also damages healthy cells. Antioxidants can help to stem the tide of peroxidation, thus stabilizing free radicals.
Antioxidants like vitamin E are crucial to the health of companion animals of any age. They can improve the quality of the immune response and the effectiveness of vaccines in young pets, and help maintain a vital immune system in seniors.
Vitamin E occurs in one of two forms, either natural or synthetic. Natural vitamin E is a collection of eight chemically unique compounds that are derived from plants, including four tocopherols and four tocotrienols. More commonly used and less expensive, synthetic vitamin E is one compound – alpha-tocopherol.
For me, the choice of using natural or synthetic vitamin E in my formulas couldn’t be clearer, and neither could the evidence. The synthetic form of vitamin E is not as active or easily absorbed as the natural form of vitamin E. The molecular structure of vitamin E determines how well the body can utilize it. In human trials, researchers found that proteins in the liver specifically select the natural form of vitamin E and largely ignore the synthetic form. In a Japanese study, scientists found that it took three times the amount of synthetic vitamin E to equal the blood levels of natural vitamin E. In the U.S., researchers found that body tissues and blood retained far higher levels of natural vitamin E versus synthetic. In addition, synthetic alpha-tocopherol vitamin E has only half the vitamin activity of the natural alpha-tocopherol vitamin E.
Why is there such a difference between synthetic and natural forms of vitamin E? The key to understanding how the body absorbs these two types differently lies on the molecular level. The cellular structure of mammals more easily recognizes natural forms of vitamins. And cellular proteins and blood plasma bind to natural forms more readily than their synthetic counterparts. Unfortunately, synthetic vitamins are cheaper and, therefore, are more prevalent in many products on the market today.
So, how can you determine if the products you are using contain the synthetic or natural form of vitamin E? Simply check out the ingredient labels! Natural vitamin E is listed as a-tocopherol acetate, d-alpha tocopherol, d-alpha tocopheryl acetate or d-alpha tocopheryl succinate. Alternately, synthetic forms of vitamin E are labeled with a “dl-“ prefix.
Kiyose C, et al. Biodiscrimination of alpha-tocopherol stereoisomers in humans after oral administration. Am J Clin Nutr 1997 (Mar); 65 (3): 785-9
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
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
Yu W, Jia L, Wang P, et al. In vitro and in vivo evaluation of anticancer actions of natural and synthetic vitamin E forms. Mol Nutr Food Res. 2008;52:447-456.
Blatt DH, Pryor WA, Mata JE, et al. Re-evaluation of the relative potency of synthetic and natural α-tocopherol: experimental and clinical observations. Journal of Nutritional Biochemistry. 2004;15:380-395.
Weiss WP, Hogan JS, and Wyatt DJ. Relative bioavailability of all-rac and RRR vitamin E based on neutrophil function and total α-tocopherol and isomer concentrations in periparturient dairy cows and their calves. J Dairy Sci. 2009;92:720-731.
Lauridsen C, Engel H, Jensen SK, et al. Lactating sows and suckling piglets preferentially incorporate RRR- over All-rac-α-tocopherol into milk, plasma and tissues. J Nutr. 2002;132:1258-1264.
Sen CK, Khanna S, and Roy S. Tocotrienols in health and disease: The other half of the natural vitamin E family. Molecular Aspects of Medicine. 2007;28-692-728.
Hayek MG, et al. Dietary vitamin E improves immune function in cats. In: Reinhart GA, Carey DP eds. Recent Advances in Canine and Feline Nutrition, Vol III: 2000 Iams Nutrition Symposium Proceedings. Wilmington, OH: Orange Frazer Press, 2000; 555-564.