Vitamin E Benefits and Dosage Information
Vitamin E, also known as tocopherol
, is a fat-soluble vitamin that is an essential nutrient for humans. It is believed that vitamin E is a potent antioxidant
that protects cell membranes and other fat-soluble parts of the body, such as low-density lipoprotein (LDL) cholesterol from damage. It also appears to provide support for the cardiovascular and immune systems.
Vitamin E deficiency typically occurs as a result of a number of malabsorption syndromes and as a result of protein-energy malnutrition. It is possible that vitamin E deficiency in some individuals may be caused by genetic defects, fat malabsorption syndromes, as well as by a wide range of hepatobiliary, pancreatic, and intestinal disorders including cystic fibrosis, primary biliary cirrhosis, chronic pancreatitis, short bowel syndromes, Crohn's disease, celiac disease, mesenteric vascular thrombosis, blind loop syndrome, intestinal pseudo-obstruction, intestinal lymphangiectasia, Whipple's syndrome, and sclerodermal bowel disease. The effects of vitamin E deficiency in children can many times be reversed by supplementation with vitamin E.
The primary condition that occurs as a result of vitamin E deficiency in humans is peripheral neuropathy which is characterized by the degeneration of axons in the sensory neurons. There are many other syndromes and long lasting effects of severe vitamin E deficiency. However, serious vitamin E deficiencies are rare in the U.S.
In addition to its antioxidant activity, vitamin E is also believed to act via other mechanisms, including direct effects on blood cell regulation, connective tissue growth, inflammation and cell division.Natural vs. Synthetic Vitamin E
While there is only a slight difference between the natural and synthetic forms of most vitamins, when it comes to Vitamin E, natural is better. Natural vitamin E contains alpha-tocopherol exclusively in an active form, either as d-alpha tocopherol or stabilized as d-alpha tocopheryl acid succinate or d-alpha-tocopheryl acetate). Synthetic vitamin E (sometimes referred to as dl-alpha-tocopherol) contains both active and inactive forms of alpha-tocopherol. Natural vitamin E may also contain other types of tocopherols, including beta-tocopherol, delta-tocopherol, and gamma-tocopherol. Some manufacturers use the term mixed tocopherols when referring to these different types.
While little is known about the value of the beta and delta forms of vitamin E some researcher believe that gamma tocopherol may be as important as alpha-tocopherol. The results of a few test tube studies indicate gamma tocopherol might be more effective than alpha tocopherol in protecting against certain types of oxidative damage. Other research shows that supplementation with high doses of alpha tocopherol (such as 1,200 IU per day) increases the breakdown, and decreases blood levels, of gamma tocopherol.
To date, most human trials with vitamin E have been conducted using the alpha (not gamma) form. Historically the synthetic dl form was used in most trials, but much research is now focusing on the natural form. The relative value and effect of alpha vs. gamma form requires more research to be fully understood.The most important thing that research supports is that alpha-tocopherol is the most biologically active form of vitamin E. In it natural form alpha-tocopherol consists of one isomer. In contrast, synthetic alpha-tocopherol contains eight different isomers, of which only one is the same as the natural form. The other seven isomers found in synthetic alpha-tocopherol range in potency from 21 percent to 90 percent of natural d-alpha-tocopherol. So what does all this mean? It means that the body is able to assimilate natural vitamin E far better than synthetic E. Specific binding and transport proteins produced in the human liver select the natural d-alpha form of vitamin E and largely ignore all other forms - those prevalent in synthetic E.
In one experiment, Japanese researchers gave natural and synthetic vitamin E to seven healthy young women. It took 300 mg of synthetic vitamin E to achieve the blood levels provided by a 100-mg dose of natural vitamin E.
In other long-term tissue assimilation studies on two cancer patients one patient was given 30 mg/day half natural, half synthetic vitamin E for one year, and the other patient was given 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.
Neither the U.S. government nor any other agency is responsible for routinely testing vitamin E supplements or other dietary supplements for their contents or quality so make sure that any supplement you take that contains vitamin E contains the natural form, most don't. Precautions
Analysis of a variety of clinical trials suggests that doses of Vitamin E that exceed 400 IU per day may actually increase the risk of death slightly in older individuals that have existing medical conditions.Dosage Recommendations
Almost all research shows that, when positive results are obtained from vitamin E supplementation, hundreds of units per day are required-an amount easily obtained with supplements but nearly impossible to obtain in the average diet. Consequently, using purely food sources to get enough vitamin E as suggested by some researchers may not be practical for many individuals.
The recommended dietary allowance (RDA) for vitamin E is quite low, 15 mg to 20 International Units (IU) per day. The most commonly recommended dosage of supplemental vitamin E for adults is approximately 300 to 800 IU per day.Supporting LiteratureAzzi A, Breyer I, Feher M, et al. Specific cellular responses to a-tocopherol. J Nutr 2000;130:1649-1652.
Balz F. Antioxidant vitamins and heart disease. Presented at the 60th Annual Biology Colloquium, Oregon State University, Corvallis, Oregon, February 25, 1999.
Christen S, Woodall AA, Shigenaga MK, et al. Gamma-tocopherol traps mutagenic electrophiles such as NO+ and complements alpha-tocopherol: physiological implications. Proc Natl Acad Sci 1997;94:3217-3222.
Kiyose C, et al. Biodiscrimination of alpha-tocopherol stereoisomers in humans after oral administration Am J Clin Nutr 1997 (Mar); 65 (3): 785-789
Morinobu T, Yoshikawa S, Hamamura K, Tamai H. Measurement of vitamin E metabolites by high-performance liquid chromatography during high-dose administration of alpha-tocopherol. Eur J Clin Nutr 2003;57:410-414.