All Rac-Alpha-Tocopherol, Alpha-Tocopherol, Alpha Tocopherol Acetate, Alpha Tocopheryl Acetate, d-Alpha-Tocopherol, d-alpha Tocopherol, d-Alpha Tocopheryl Acetate, d-Alpha-Tocopheryl Acid Succinate, d-Alpha Tocotrienol, dl-Alpha-Tocopherol, d-Beta-Tocopherol, d-Delta-Tocopherol, d-Gamma-Tocopherol, d-Gamma Tocotrienol, Fat-Soluble Vitamin, Mixed Tocopherols, RRR-Alpha-Tocopherol, Tocopherol, Mixed Tocotrienols, Tocotrienol, Beta-Tocopherol, Delta-Tocopherol, Gamma-Tocopherol, Alpha Tocotrienol, Beta Tocotrienol, Delta Tocotrienol, Gamma Tocotrienol, Palm Tocotrienols, Tocopherol Acetate, Tocopheryl Acetate, Tocotrienols, Vitamin E Acetate, Vitamin E Succinate.
Vitamin E exists in eight different forms ("isomers"): alpha, beta, gamma, and delta tocopherol; and alpha, beta, gamma, and delta tocotrienol. Alpha-tocopherol is the most active form in humans. Dosing and daily allowance recommendations for vitamin E are often provided in Alpha-Tocopherol Equivalents (ATE) to account for the different biological activities of the various forms of vitamin E, or in International Units (IU), which food and supplement labels may use. Vitamin E supplements are available in natural or synthetic forms. The natural forms are usually labeled with the letter "d" (for example, d-gamma-tocopherol), whereas synthetic forms are labeled "dl" (for example, dl-alpha-tocopherol).
Vitamin E is a fat-soluble antioxidant that stops the production of ROS formed when fat undergoes oxidation. [1] Dietary and supplemental vitamin E is absorbed and delivered to the liver, but of the various antioxidants with vitamin E activity, only alpha-tocopherol is preferentially recognized by the alpha-tocopherol transfer protein (alpha-TTP) and is transferred to plasma, while the other vitamin E forms (e.g., gamma-tocopherol or tocotrienols) are removed from the circulation. Hepatic alpha-TTP is required to maintain plasma and tissue alpha-tocopherol concentrations. The liver is the master regulator of the body's vitamin E levels in that it not only controls alpha-tocopherol concentrations, but also appears to be the major site of vitamin E metabolism and excretion. Vitamin Es are metabolized similarly to xenobiotics they are initially omega-oxidized by cytochrome P450s, undergo several rounds of beta-oxidation, and then are conjugated and excreted. As a result of these various mechanisms, liver alpha-tocopherol and other vitamin E concentrations are closely regulated; thus, any potential adverse vitamin E effects are limited. [Traber MG, Annu Rev Nutr. 2007;27:347-62]
Vitamin E is an important component of our antioxidant system. It is considered a master antioxidant because: [Papas AM. The Vitamin E Factor, HarperCollins Publishers, Inc., New York, NY. 1999]
- Tocopherols and tocotrienols are chain-breaking antioxidants – they break the chain reaction of lipid peroxidation, the process that turns lipid rancid.
- The structure of vitamin E makes it unique and indispensable in protecting cell membranes. Vitamin E, primarily alpha-tocopherol, anchors itself strategically in the membrane with the hydrophobic (water hating) tail in the interior of the membrane. The hydrophilic (water loving) head is in the hydrophilic area of the membrane.
- Vitamin E is the master inhibitor of oxidation of the bad cholesterol LDL - which is believed to be the first step in atherosclerosis.
- Vitamin E inhibits the activity of the enzyme PKC (protein kinase C) which is associated with inflammation.
- Vitamin E exhibits anticoagulant properties. Oxidized alpha-tocopherol (called alpha-tocopheryl quinone) is also a powerful anticoagulant.
- Vitamin E compounds reduce the production of inflammatory compounds such as prostaglandins.
- Tocotrienols and gamma-tocopherol have other unique functions.
Table: Recommended Dietary Allowances (RDAs) for Vitamin E (Alpha-Tocopherol) [4]
Table lists the RDAs for alpha-tocopherol in both mg and IU of the natural form; for example, 15 mg x 1.49 IU/mg = 22.4 IU. The corresponding value for synthetic alpha-tocopherol would be 33.3 IU (15 mg x 2.22 IU/mg).
Symptoms of vitamin E deficiency include muscle weakness, visual problems (especially at night), and a poor sense of balance. Over a long period, vitamin E deficiency may progress to blindness, heart disease, and impaired thinking. Supplements are usually only necessary or recommended for people with vitamin E deficiency or a condition that puts them at risk for this deficiency. [5] Possible Risks of Vitamin E Use include increased bleeding and inhibition of clotting function (if taken in excess of 1,000 mg/day). And, some studies indicate an increase risk of heart problems among people who are taking high doses of vitamin E (more than about 300 mg/day). Vitamin E has no known side effects when taken in moderate doses. It’s rare for anyone to be allergic to Vitamin E. But if you do experience a severe reaction (rash, itching, swelling, severe dizziness, trouble breathing) see a doctor immediately. [6]
Vitamin E, a potent peroxyl radical scavenger, is a chain-breaking antioxidant that prevents the propagation of free radical damage in biological membranes. Scientist consider the evidence for potential sites in cellular metabolism and signal transduction where vitamin E may have a structure-specific role in addition to its antioxidant function. The roles of tocopherol-binding proteins in cellular trafficking of vitamin E, especially the incorporation of RRR-alpha-tocopherol into nascent lipoproteins, and the delivery of RRR-alpha-tocopherol to the nucleus are considered. [7] Scientists are investigating whether, by limiting free-radical production and possibly through other mechanisms, vitamin E might help prevent or delay the chronic diseases associated with free radicals. [8]
Perhaps not surprisingly, vitamin E which has been touted to be potentially beneficial for a variety of disorders, including cancer, heart disease, and Other health benefits of vitamin E, based on its function as an antioxidant. [9] The most reliable studies on this issue are controlled clinical trials, such as a large 1994 study of antioxidant vitamins and cancer conducted by the National Cancer Institute (NCI) and the National Public Health Institute of Finland. The study was designed to find out whether antioxidant vitamins in higher doses than the RDA (50 milligrams) could reduce the incidence of lung cancer, other types of cancer, and other illnesses among 29,000 male smokers. The study found no beneficial effect of vitamin E supplements on lung cancer incidence. It found lower rates of prostate and colorectal cancer among those who received vitamin E, but higher rates of bladder, stomach, and other types of cancer. [10,11]
Vitamin E has been linked to the prevention of cardiovascular disease (CVD) based on the hypothesis that oxidation of LDL initiates the development of atherosclerotic plaque. This hypothesis, although not universally accepted, is supported by studies in vitro, in animals, and in humans. This background in basic science and a number of epidemiological studies, led to the initiation of clinical intervention trials.
G. Oriani et. al. in their study suggest that vitamin E plays an important role in the regulation of serum concentrations of cholesterol and lipoproteins in weanling rabbits. Consequently, the maintenance of an adequate nutritional status of vitamin E in the postweaning period is important to avoid alterations of serum lipid pattern ( J Anim Sci. 1997 Feb;75(2):402-8.) [12].
Support for the role of vitamin E in heart disease prevention has come from observational studies, particularly 2 cohort studies which were published in 1993. In the 1st study, the Nurses' Health Study, the researchers concluded that among 83,234 middle-aged women who participated in the study, there was a 40% reduced risk of coronary artery disease for those who took vitamin E supplements compared to those who did not (New England Journal of Medicine 1993;328: 1444-9). The 2nd study, the Health Professionals Follow-up Study, involved over 39,000 males and showed evidence of a significant association between a high intake of vitamin E from supplements and a lower risk of heart disease (New England Journal of Medicine 1993; 328:1450-1456). [13]
The following is a very brief overview of the role of vitamin E in wellness and disease prevention, Andreas M. Papas, Ph.D in NutriNews, January/February 2008 to explain other health benefits of vitamin E including Alzheimer’s disease, aging and immunity, cataracts, and skin health.
- Alzheimer’s disease: A collaborative study at major medical centers across the United States found that in Alzheimer’s patients taking large doses of vitamin E (2,000 IU/day), progression of the memory-robbing disease was delayed by approximately seven months.
- Aging and immunity: Studying healthy elderly people, researchers at Tufts University, reported that vitamin E increased the power of disease-fighting T-cells, improved delayed-type hypersensitivity skin response (DTH) by 65 percent and antibody response to hepatitis B six-fold. It also increased significantly the antibody titer to tetanus vaccine. A recent study in Netherlands reported no benefit in acute respiratory tract infections in elderly person from vitamin E supplementation.
- Cataracts: A Canadian study compared the consumption of vitamin supplements by 175 cataract patients with that of 175 cataract-free controls. People in the control group were taking significantly more supplements of vitamins C and E than the cataract group.
- Skin health: Vitamin E has been shown to reduce the damage to skin from exposure to UV radiation and ozone.
Updated : Benefits of Vitamin E
