All you need to know about Vitamin E
The most important form of Vitamin E are tocopherol and tocotrienol.
Physiological Function of Vitamin E
Vitamin E has many important biological functions.
- As an antioxidant, vitamin E acts as a peroxyl radical scavenger, disabling the production of damaging free radicals in tissues, by reacting with them to form a tocopheryl radical, which will then be reduced by a hydrogen donor (such as vitamin C) and thus return to its reduced state. As it is fat-soluble, it is incorporated into cell membranes, which protects them from oxidative damage. Vitamin E has also found use as a commercial antioxidant in ultra high molecular weight polyethylene (UHMWPE) used in hip and knee replacements, to help resist oxidation.
- As an enzymatic activity regulator, for instance, protein kinase C (PKC), which plays a role in smooth muscle growth, can be inhibited by α-tocopherol. α-Tocopherol has a stimulatory effect on the dephosphorylation enzyme, protein phosphatase 2A, which in turn, cleaves phosphate groups from PKC, leading to its deactivation, bringing the smooth muscle growth to a halt.
- Vitamin E also has an effect on gene expression. Macrophages rich in cholesterol are found in the atherogenetic tissue. Scavenger receptor CD36 is a class B scavenger receptor found to be up-regulated by oxidized low density lipoprotein (LDL) and binds it. Treatment with α-tocopherol was found to downregulate the expression of the CD36 scavenger receptor gene and the scavenger receptor class A (SR-A) and modulates expression of the connective tissue growth factor (CTGF). The CTGF gene, when expressed, is responsible for the repair of wounds and regeneration of the extracellular tissue lost or damaged during atherosclerosis.
- Vitamin E also plays a role in neurological functions, and inhibition of platelet aggregation.
- Vitamin E also protects lipids and prevents the oxidation of polyunsaturated fatty acids.
Deficiency of Vitamin E
Vitamin E is transported in plasma in the lipoproteins and it serves as the most important membrane protective antioxidant and free radical scavenger in the body. Although alpha-tocopherol is the major component in foods and human tissues, the beta, delta and gamma isomers are sometimes included in profiles to show detail of tissue composition. Experimental vitamin E deficiency is difficult to produce in humans because of the intricate system of checks and balances in the antioxidant cascade.
Health concerns due to Vitamin E deficiency
Symptoms of vitamin E deficiency are subtle and following clinical effects are well documented due to deficiency of Vitamin E:
- Heart Disease
- Hemolytic anemia
- Neurological disease (including ataxia)
- Ocher neuropathes
Assessment of Vitamin E Status
Plasma or serum alpha-tocopherol should be above 12 mgfL. Since patients with pertnglyceridemia have elevated levels of lipoproteins, vitamin E concentrations also tend to rise, leading to overestimation of vitamin E total body status. The ratio of measured tocopherol to triglycerides in plasma or serum may be calculated as a way of correcting for this effect. Vitamin E deficiency is indicated when the ratio of serum tocopherol to total lipids is less than 0.8 mg/g
Supplementation of Vitamin E
Adult Repletion: 200 to 1,600 IU/day
Best or most Bio-Available or Active form of Vitamin E
Alpha, beta, Gamma and Delta Tocopherol; Alpha, beta, Gamma and Delta Tocotrienol
Dietary sources of Vitamin E
Dietary sources of Vitamin E – alpha-tocopherol are:
- Vegetable oils
- Green leafy vegetables
- Wheat germ oil
- Sunflower seeds
- Sunflower oil
Dietary sources of Vitamin E – Gamma-tocopherol are: