This section is compiled by Frank M. Painter, D.C. Send all comments or additions to:
If there are terms in these articles you don't understand, you can get a definition from the Merriam Webster Medical Dictionary. If you want information about a specific disease, you can access the Merck Manual. You can also search Pub Med for more abstracts on this, or any other health topic.
Flawed Meta-Analysis Misrepresents Vitamin E Research November 16, 2004 ––
A flawed "retrospective review" published in the Annals of Internal Medicine took a narrow look at only 19 of the more than 2,170 published papers addressing the efficacy and safety of Vitamin E. Strangely, "18 of those 19 clinical studies showed no increase in the risk for health complications or fatalities with Vitamin E versus a control group. Only one study out of the 19 demonstrated a higher risk and that study was with patients who were using estrogen hormone replacement therapy (HRT) along with Vitamin E."
Advice to Patients: Don't Throw Away Your Vitamin E Dietary Supplement Information Bureau
"Do not throw away your vitamin E," said C. Wayne Callaway, MD, Internal Medicine, Endocrinology, Metabolism and Clinical Nutrition. "One study does not outweigh the many studies that document the benefits of vitamin E in people who need it and the lack of harm in people who do not." In response to the meta-analysis, the DSIB launched a new Web site - www.vitaminEfacts.org - to help consumers obtain accurate information on vitamin E.
Military Program Proposes Saving Money Through Vitamin E Supplementation WASHINGTON, May 22, 1997 –– A new report by the National Defense Council Foundation finds that the federal government could save up to $6.3 billion annually by increasing the health of active and retired military personnel through a anti–aging program that includes the use of Vitamin E supplementation.
Vitamin E's Powerful Family Of Antioxidants
Eight natural compounds have vitamin E activity. These are the four tocopherols, designated as alpha, beta, gamma and delta, and four tocotrienols also designated as alpha, beta, gamma and delta. Yet, alpha-tocopherol has become synonymous with vitamin E. It is the most bioactive form based on the rat foetal resorption test, the classical assay for vitamin E activity. Recent research, however, shows that the other tocopherols and tocotrienols have important and unique antioxidant and other biological effects in nutrition and health. [1, 2] This paper will review the biological function of tocopherols and tocotrienols and their role in health and disease.
Natural vs. Synthetic Vitamin E
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.
Vitamin E 2000
For decades vitamin E has maintained a position along with vitamin C and calcium as one of the three most popular single-ingredient dietary supplements. As scientists continue to examine the role of free radicals in disease initiation and promotion, research substantiates this potent antioxidant's ability to treat stroke, cardiovascular disease and cancer.
Vitamin E Gains New Protective Role for the Heart
Researchers have discovered a new role for vitamin E in heart disease protection. Vitamin E supplements lowered blood levels of two key substances that contribute to atherosclerosis, according to a study conducted at the University of Texas Southwestern Medical Center in Dallas. This may be especially important for diabetics who are at high risk of heart disease and have circulatory problems.
Vitamin E: Weighing the Tocopherols
Next to vitamin C, vitamin E is probably the most well-known vitamin. In an informal survey I conducted among acquaintances, adults could tell me that alpha-tocopherol is vitamin E and that it is an antioxidant. Many people were aware of claims that vitamin E supplementation slows aging, improves immunity, protects against cancer and heart disease, and is generally good for health. But not many people knew if they got enough. Not even doctors are clear if vitamin E supplements are necessary to prevent deficiency.
Two New Studies Find Natural Vitamin E Better Absorbed, Retained Than Synthetic
Researchers have long known that natural vitamin E, milligram for milligram, is about 36 percent more potent than the synthetic form of the vitamin. In fact, the "international unit," or IU, standard was developed to compensate for these differences. But two new studies using different groups of people - not laboratory animals - have found that natural vitamin E is utilized twice as efficiently as the synthetic form.
Synthetic vs. Natural Vitamins
Infants Discriminate Between Natural and Synthetic Vitamin E
Am J Clin Nutr. 2003 (Apr); 77 (4): 899–906 ~ FULL TEXT
Animal and human studies show that the biological activity of tocopherols is dependent on their particular stereochemistry and chemical form. [1-8] Tocopherols have a saturated phytyl group attached to the 2 position of the chromanol ring. Natural vitamin E (2R,4'R,8'R-α-tocopherol or more simply, RRR-α-tocopherol) has a particular stereochemistry in which the methyl groups in the 2, 4', and 8' positions are all in the R configuration. For synthetic vitamin E (all-rac-α-tocopherol), the configuration at the 2, 4', and 8' positions can be R or S. Natural vitamin E is a single stereoisomer, whereas synthetic vitamin E contains equimolar amounts of 8 isomers, half of which are 2R isomers.
Vitamin E: Function and Metabolism
FASEB J. 1999 (Jul); 13 (10): 1145–1155 ~ FULL TEXT
Although vitamin E has been known as an essential nutrient for reproduction since 1922, we are far from understanding the mechanisms of its physiological functions. Vitamin E is the term for a group of tocopherols and tocotrienols, of which alpha–tocopherol has the highest biological activity. Due to the potent antioxidant properties of tocopherols, the impact of alpha–tocopherol in the prevention of chronic diseases believed to be associated with oxidative stress has often been studied, and beneficial effects have been demonstrated. Recent observations that the alpha–tocopherol transfer protein in the liver specifically sorts out RRR–alpha–tocopherol from all incoming tocopherols for incorporation into plasma lipoproteins, and that alpha–tocopherol has signaling functions in vascular smooth muscle cells that cannot be exerted by other forms of tocopherol with similar antioxidative properties, have raised interest in the roles of vitamin E beyond its antioxidative function.
Human Plasma and Tissue Alpha-tocopherol Concentrations in Response
to Supplementation with Deuterated Natural and Synthetic Vitamin E
Am J Clin Nutr. 1998 (Apr); 67 (4): 669–684
We report a comparison of natural and synthetic vitamin E in humans using deuterium labeling to permit the two forms of vitamin E to be measured independently in plasma and tissues of each subject. Differences in natural and synthetic vitamin E concentrations were measured directly under equal dosage conditions using an equimolar mixture of deuterated RRR-alpha-tocopheryl acetate and all-rac-alpha-tocopheryl acetate. Two groups of five adults took 30 mg of the mixture as a single dose and as eight consecutive daily doses, respectively. After a 1-mo interval the schedule was repeated but with a 10-fold higher dose (ie, 300 mg). In each case, the ratio of plasma d3-RRR-alpha-tocopherol to d6-all-rac-alpha-tocopherol (RRR:rac) increased from approximately 1.5-1.8 to approximately 2 after dosing ended.
Biodiscrimination of Alpha-tocopherol Stereoisomers in Humans
After Oral Administration
Am J Clin Nutr. 1997 (Mar); 65 (3): 785–789
We investigated changes in the concentrations of the stereoisomers of alpha-tocopherol in serum and lipoproteins in seven normal, healthy women aged 21-37 y who had received oral administration of natural and synthetic alpha-tocopheryl acetate. When bioavailability was estimated from the increase in the concentration of RRR- or all-rac-alpha-tocopherol in serum, bioavailability of RRR-alpha-tocopherol administered at 100 mg/d was not different from that of all-rac-alpha-tocopheryl acetate administered at 300 mg/d.
Therapeutic Uses of Vitamin E in Prevention of Atherosclerosis
Alternative Medicine Review 1999 (Dec); 4 (6): 414–423 ~ FULL TEXT
On the basis of the literature search, the authors recommend 400 IU or more per day of vitamin E to patients at high risk or already diagnosed with coronary artery disease. Vitamin E supplementation may also be beneficial in the prevention of cerebro- and peripheral vascular diseases.
Vitamin E and Macrophage Cyclooxygenase Regulation in the Aged
J Nutr 2001 (Feb); 131 (2): 382S–388S
Researchers have found that vitamin E supplements can improve rheumatoid arthritis symptoms and reduce markers of inflammation. In a recent study with laboratory mice, Simin Nikbin Meydani, D.V.M., Ph.D., of Tufts University in Boston, found that peroxynitrite, a free radical built around an oxygen and nitrogen molecule, in-creased activity of cyclooxygenase-2 (cox-2), an enzyme involved in making inflammatory prostaglandins. Giving the mice extra vitamin E reduced cox-2 and proinflammatory prostaglandin E2 levels.