The Vitamin E story
Vitamin E Story
Relatively recent research has pointed to the need for Vitamin E in the maintenance of normal body metabolism, and in the protection of body tissues and skin from damage caused by normal body processes.
The human skin is an organ, which is constantly embattled by the environment. Chemicals and environmental influences attack its health and appearance.
A well-known phenomenon is skin aging due to sun exposure (photo aging): ultraviolet (UV) and infrared (IR) radiation accelerates the aging process. An exposure to ultraviolet rays leads to the formation of free radicals. Anti-oxidative substances in the skin such as vitamin E and vitamin C are destroyed after exposure to ultraviolet rays.
Free radicals are highly reactive molecules. Their damaging potential may be counteracted by anti-oxidative substances in the skin such as the lipid-soluble vitamin E and the water-soluble vitamin C: If these antioxidants are topically applied or if they are replenished with food or dietary intake, they implement a protective effect by destroying the vitamins first, before destroying DNA, proteins and other important molecules.
With increasing UV exposure the anti-oxidative defence is compromised and an increasing amount of free radical species escapes destruction through the anti-oxidative defence system. These free radicals may then cause various types of cell damage, including lipid peroxidation as well as a modification of protein and DNA. Such damage may lead to premature aging and more serious consequences, such as initiation of skin cancer.
In its esterified form, Vitamin E may have anti-inflammatory effects and may provide protection from UVR damage. In nature, Vitamin E appears as Tocopherols, of which the alpha form has the highest biological potency. The unesterfied form is present in oil and other vegetable oils. Unesterified a-tocopherol has antioxidant properties, and is a physiological antioxidant.
Although the main claim for Vitamin E in cosmetics has been as a "natural moisturiser," extensive studies conducted in the last decade point to significant benefits beyond moisturisation.
Vitamin E is soluble in alcohol, fats and oils. Like vitamin A palmitate, it can be emulsified in aqueous solutions with polysorbate 80. Vitamin E can be added to the oil phases of topical formulations without special precautions. Vitamin E is now considered to be essential for the stabilisation of biological membranes, particularly those containing large amounts of polyunsaturated fatty acids. The oxidation of polyunsaturated fat produce lipid peroxides unsaturated fats production which interfere with the structure and function of biological membranes.
Absorption through the skin occurs with both the alcohol and acetate. A relatively high proportion of topically applied material has been found in the stratum corneum and in the lower viable skin layers. It has also been shown that the vitamin is absorbed directly into the hair cortex.
It is now known that Vitamin E acts as an antioxidant, and can inhibit the formation of lipid peroxides. It might thus play a role against ageing- particularly of the skin -since lipid peroxidation in tissues is one of the causes of skin ageing. Vitamin E appears to improve decreased function of the sebaceous gland; it is also expected to ameliorate excessive pigmentation in the skin - a possible cause of decreased elasticity and poor water-retention, which are characteristics of aged skin. For these reasons, it is now recommended that vitamin E be added to cosmetics.
UV light is the most important cause of premature ageing of the skin. For many years, it has been recognised that UVR induces production of free radicals in the skin. aTocopherol is an excellent lipid radical scavenger; thus, it is especially useful in terminating lipid radical chain reactions. In these reactions, the stabilised, low energy tocopheroxyl radical is formed. This radical is unable to function by itself as an initiator of new radical chain reactions with membrane lipids, but it can be regenerated by other reducing antioxidants (e.g., Vitamin C).
Vit E & Vit C Interact with each other
The picture (left) shows how vitamin E traps free radicals in the skin cells, while vitamin C supports this function. The free radical molecules (symbolized in red) damage the skin in the cell membrane (see (1) enlarged area), DNA in the cell nucleus (2) as well as in the collagen fibres (3), which are responsible for the tightness of the skin. Vitamin E may be stored in the cell membrane and may take away -- figuratively spoken the "point" of the molecule -- thus quenching its damaging potential. The free radical molecules (symbolized in red) thus lose their damaging effect (symbolized in green). Vitamin C then has the task to remove the "point" from the vitamin E and to release it again. Thus, vitamin C and vitamin E interact with each other and constitute an interplay between water-soluble and lipid-soluble antioxidants in protection against free radical damage.
Sources: wheat germ, wheat germ oil, whole grain, unrefined vegetable oil, nuts, seeds, eggs, whole grains, green leafy vegetables; supplements: "dry" E acetate or succinate, d-alpha tocopherol, gamma/alpha tocopherols, multi-vitamin, multi-mineral-vitamin formulations;
Absorption: from small intestine, along with fats; 40 to 60% is absorbed into lymph (inchylomicrons); remainder is discarded in feces;
Improved by: edible fats & oils; being taken with a meal; vitamin C, which prevents its oxidation; vitamin A, which aids in transport; manganese & selenium;
Antagonized by: salts & sugar/acid chelates of iron & copper (oxides, carbonates, gluconates, succinates, acetates, etc.); oxygen; rancid food oils; processed foods; mineral oil; oral contraceptives; freezing; oxidizing agents, ozone, & nitrogen oxides;
Stability: destroyed by light & oxygen; heat-stable in boiling, but destroyed during frying & deep frying; some lost in frozen storage; storage at room temperature may decrease vitamin E content of foods by up to 50% within 2 weeks; encapsulation protects vitamin E against destruction;
Storage: largely in adipose tissue, liver, & muscle; high concentrations also found in blood platelets, pituitary, adrenals, testes, ovaries;
Metabolism: plasma levels drop to half within a few days when vitamin E is withdrawn from foods; frank deficiency may take several months to develop.
Supplements: In oral administration for therapy against deficiency of this vitamin, a-tocopheryl acetate is used, since this ester is more stable against oxidation than free tocopherol. Gastrointestinal absorption of Vitamin E acetate is similar to that of other fat-soluble vitamins. The ester is first hydrolysed in the intestinal lumen by the bile and pancreatic juice. The tocopherol formed is dispersed by formation micelles with bile salts, then is absorbed from the intestinal tract by passive diffusion.