Most animal species, including humans, need vitamin E. In 1922, researchers discovered that if rats ate a diet lacking in vitamin E, they became unable to reproduce. When wheat germ oil was added to the diet, fertility reappeared. Scientists later isolated vitamin E and called it the "anti-sterility" vitamin. The chemical name for the most active form of vitamin E is alpha-tocopherol. The term tocopherol comes from the Greek words tokos., Which means "offspring", and phero, which means "to bring". Tocopherol, therefore, means "to bring children".
Although the recommended daily allowance for vitamin E (alpha-tocopherol) is fixed at 10 mg (about 15 IU of vitamin E activity), the amount of vitamin E needed is largely dependent on the amount of polyunsaturated fat in the diet. The more polyunsaturated fats are consumed, the greater the risk of them being damaged. Since vitamin E prevents this damage, the increase in polyunsaturated fatty acids is accompanied by a parallel increase in the need for vitamin E.
Fortunately, in nature, where there are high levels of polyunsaturated fatty acids, there are also higher levels of vitamin E. The best sources of vitamin E are polyunsaturated vegetable oils, seeds, nuts and whole grains. Cooking and processing foods, especially flour, reduce their vitamin C content. Valuable sources of vitamin E are asparagus, avocado, berries, green leafy vegetables and tomatoes.
Signs and symptoms of deficiency
Vitamin E acts mainly as an antioxidant in the protection of cell membranes. In the absence of vitamin E, the body's cells, especially nerve cells, would be very sensitive to damage. Serious vitamin E deficiencies are quite rare, however there are four situations in which low vitamin E levels are common.
- In fat malabsorption syndrome, such as celiac disease, cystic fibrosis and post-gastrectomy syndrome.
- In premature babies.
- In hereditary diseases of red blood cells, such as sickle cell disease and thalassemia.
- In hemodialysis patients.
Symptoms of vitamin E deficiency in adults include nerve damage, muscle weakness, poor coordination, involuntary eye movements and breakdown of red blood cells, which can lead to anemia (haemolytic anemia). In premature babies, vitamin E deficiency is characterized by haemolytic anemia and a serious eye disorder known as retrolental fibroplasia.
Recommended daily dose
|RECOMMENDED DAILY DOSE FOR VITAMIN E
|Infants up to 1 year||4.5-6.0UI|
|Children 1-10 years||9-10.5|
|Adolescents and adults
Males over 11 years
Females over 11 years
women Breastfeeding women
Vitamin E is the main antioxidant in the "lipid phase" in the body. It is found within the lipid (fat) fraction of cell membranes and transport molecules and has a stabilizing and protecting function of these structures from substances such as: lead, mercury and other heavy metals; toxic compounds such as benzene, carbon tetrachloride and cleaning solvents; medications; radiation; free radicals of the organism. Thanks to its antioxidant effects, vitamin E supplements, or a diet rich in this vitamin, exert a protective effect in many common diseases.
Vitamin E is essential for the immune function. In addition to being beneficial for the thymus and putting white blood cells into circulation in case of danger, it is responsible for protecting the immune system from possible damage in the event of oxidative stress and chronic viral diseases, such as AIDS and chronic viral hepatitis.
Vitamin E is available in many different forms, both natural and synthetic. Natural forms of vitamin E are marked with the prefix das in d-alpha-tocopherol, while synthetic forms have the prefix dl-, as in dl-alpha-tocopherol. The letters d and l reflect the mirror image of the vitamin E molecule. Of these mutually mirror images, you have an analogy in your hands: a right hand (d) and a left hand ( l ). Only the d form is recognized in the human body . Although the l- form has antioxidant activity, it can inhibit the entry of the d-form into cell membranes (1-3). Natural vitamin E (form d ), therefore, brings greater benefits than the synthetic one ( dl ). My advice is to carefully avoid synthetic vitamin E. Here are some of the names of each type of vitamin E.
|d-alpha-tocopheryl acetate||d-alpha-tocopheryl acetate|
|d-alpha-tocopheryl succinate||d-alpha-tocopheryl succinate|
There are several natural tocopherols that exhibit vitamin E activity. The most active tocopherol in terms of antioxidant activity is d-alpha-tecopherol, however also d-beta-, d-gamma-, d-delta-tocopherol and a group of related compounds known as tocoaienols have antioxidant activity. Natural sources of vitamin A, such as soy, are usually only 10% alpha-tocopherol; the remaining part of the vitamin E content is made up of other "less active" tocopherols; only recently the benefits brought by these other tocopherols are being discovered, for example, while the vitamin E activity of alpha-tocotrienol is calculated in 30% compared to 100% of alpha-tocopherol, alpha-tocotrienol has demonstrated greater antitumor activity (4). In a study of male subjects with coronary heart disease, d-gamma-tocopherol was low, unlike d-alpha-tocopherol; this suggests that d-gamma- may be just as important as d-alpha-tocopherol in the prevention of heart disease (5) .
Vitamin E supplements containing tocopherol blends, including tocotrienols, appear to offer the greatest benefits. The best forms of natural vitamin E in these products are probably those where d-alpha-tocopherol is bound to acetate or succinate, two weak natural acids of cellular metabolism. The bond gives rise to the formation of d-alpha-tocopheryl acetate and d-alpha-tocopheryl succinate, respectively. These forms of vitamin E may be more beneficial due to their greater stability than d-alpha-tocopherol IIbero. After ingestion of these vitamin forms, the acetate or succinate are separated from the molecule, allowing the alpha-tocopherol to reform (3) .
Comparison between fat-soluble vitamin E and water-soluble vitamin E
Another commercial form of vitamin E is the water-soluble one. This form is much more expensive than the fat-soluble one (about 10 times), but is it worth the extra money? Clinical research on cystic fibrosis patients gives a negative answer (6). Patients affected by this disease, a genetic disease characterized by severe pancreatic insufficiency and fat malabsorption, often suffer from deficiencies of fat-soluble vitamins, particularly vitamin E. Children and adults with cystic fibrosis therefore need supplements of this vitamin. While many doctors recommend reverting to the expensive water-soluble form, in reality the fat-soluble form (aka regular vitamin E supplements) provides similar results at a much lower cost. A double-blind study comparing the two forms showed equally good results with both. Since they are equally effective, the choice should be based on economic issues. Based on current prices, the use of the fat-soluble form would lead to savings of approximately $ 500 per year. Since people with cystic fibrosis need long-term vitamin E supplements, for an indefinite period, over 20 years this would lead to savings of $ 10,000.
|Table 5.1 Vitamin E activity of various tocopherols|
|The activity is expressed in International Units of cmplace per mg|
Warnings and Precautions
Although vitamin E is fat soluble, it has an excellent safety standard. Recent clinical trials on vitamin E supplements at doses even higher than 3200 IU daily, in subjects belonging to different groups, for periods of up to two years, have not shown any negative side effects. Several studies have been concerned with evaluating safety measures in detail.Per example, a double-blind study on 32 elderly people (over 60 years of age) allowed to determine the effect of the daily supplement of 800 VI of dl-alpha-tocopheryl. acetate administered for 30 days, by assessing general health, nutritional conditions, liver and kidney function, metabolism, blood cells, serum levels of nutrients and antioxidants,(7) . The only significant effect appeared to be an increase in serum vitamin E levels. At these doses, vitamin E was very well tolerated and no side effects were reported. The results of this study should not surprise, to the contienteer, they are consistent with a large amount of data, demonstrating the extreme safety of vitamin E supplements.
Vitamin E interacts extensively with other antioxidant nutrients, especially vitamin C and selenium. Vitamin E also improves the use of vitamin A and may be needed in the conversion of vitamin B12 to its most active form, and in protecting against any damage to essential fatty acids.
Vitamin E can enhance the effects of anticoagulant drugs such as warfarin and stimulate the procoagulative activity of vitamin K. Finally, it can also increase the inhibition of platelet aggregation caused by acetylsalicylic acid.
1. Horwitt MK, Vitamin E: A re-examination. Am J Clin Nutr 29, 569-578, 1976.
2. Ingold KU, et al., Biokinetics of and discrimination between dietary RRR- and SRRR-alpha-Tocopherols in the male rat. Lipids 22, 163-172, 1987.
3. Burton GW and Traber MG, Vitamin E: Antioxidant activity, biokinetics, and bioavailability. Annu Rev Nutr 10, 357-382, 1992.
4. Komyama K. el aI., Studies on the biological activity tocotrienols. Chem Pharm Bull 37, 1369-1381, 1989.
5. Ohrvall M. Sundlof G, and Vessby B, Gamma, but not alpha, tocopherol levels in serum are reduced in coronary heart disease patients. J Int Med 239, 111-117, 1996.
6. Nasr SZ, et al., Correction of vitamin E deficiency with fat-soluble versus water-miscible preparations of vitamin E in patients with cystic fibrosis. J Pediatr 122, 810-812, 1993.
7. Meydani SN. et al., Assessment of the safety of high-dose, short-term supplementation with vitamin E in healthy older adults. Am J Clin Nutr 60, 704-709, 1994.