The Vitamin E Minefield

Vitamin E is a widely recognised as possessing a number of important health benefits, most notably on the cardiovascular system and skin. Because vitamin E is a fat soluble vitamin, it is incorporated into cell membranes and here it provides protection to the lipid membranes that surround our cells. Although it does possess other functions, the main role of vitamin E is as an antioxidant within these membranes, and here it interacts with vitamin C to help maintain high cellular levels of the cellular antioxidant reduced glutathione, via a complex recycling system. Some foods do contain substantial amounts of vitamin E, but in reality supplementation is necessary to take full advantage of the health benefits. Although you might have expected that supplementation with vitamin E was a straight forward task, its complex chemistry along with the myriad of supplements on the market make choosing the right vitamin E a tricky process.

Difficulties in supplement selection begin when you realise that vitamin E is actually a mixture of eight different chemicals with the same biological activity. Called vitamers, these compound are named alpha, beta, gamma and delta tocopherol and alpha, beta, gamma and delta tocotrienol. Vitamin E is synthesised only in photosynthetic organisms like plants, with the tocopherols being found mainly in leafy plant foods and the tocotrienols being found in legumes, and the bran and germ sections of cereal grains such as oats. The tocopherols and tocotrienols have a similar ring like structure (chromanol head), but possess differences in their side chains which gives them slightly different properties. While the tocopherols have straight chains, chemical double-bonds give the tocopherols kinks to their chains and this alters their antioxidant activity. The main form of the vitamin in our diet is alpha and gamma tocopherol, and it is these forms that most frequently accumulates in animal and human tissues.

As well as there being different isomers of vitamin E, there are also two similar forms of each of the eight vitamin E vitamers. These isomers are structurally identical to each other, but are mirror images. Just like the right and left hand of a pair of gloves, they are the same but opposite. The right and left forms of the vitamin E vitamers are designated as D- for dextro (right) and L- for levo (left) respectively. If vitamin E is synthesised artificially in the laboratory through a chemical process it will be roughly a 50 / 50 mixture of both the D- and the L- forms as the process cannot differentiate the two forms. In nature, plants use complex metabolic pathways using precise enzymatic steps to synthesise only the D-form. This is important because studies show that the L- form of the vitamin is not utilised by the body. For this reason cheaper artificially synthesised DL-forms of vitamin E in supplements are only about 50 % as potent as the all natural D-form extracted from plants.

Most commonly, vitamin E vitamers are packaged in supplements in their alcohol form as tocopherol or tocotrienol. Because the alcohol form is fat soluble it is usually added to oil filled capsules containing plant oils such as wheat germ or soy oil. Wheat germ itself is a great source of vitamin E and is often sold as oil containing its natural alcohol form of vitamin E. However, manufacturers can also react the alcohol form of vitamin E with an acetate or succinate group for form an ester of vitamin E called tocopheryl acetate or tocopheryl succinate. Once ingested the body uses digestive enzymes to hydrolyse the ester bond, thus freeing the tocopherol or tocotrienol alcohol, which is absorbed through the gut wall. The esterification of tocopherol in this way increases the shelf life of vitamin E and allows it to be incorporated into dry tablets such as multivitamin with no detrimental impact on bioavailability.

Because of its ability to protect cell membranes, vitamin E may be able to protect skin from free radicals and prevent the adverse affects of aging. Vitamin E is therefore placed in many skin formulations and anti-wrinkle creams for topical application with this thought in mind. Many creams now contain tocopherol forms of vitamin E and evidence suggests that this increases the vitamin E content of the skin cell membranes and protects them from free radical damage. However, care must be taken to read the ingredients on any such formulations because unlike the digestive system, the skin does not possess the enzymes necessary to cleave the ester bonds in the acetate or succinate forms of the vitamin. Therefore if the formulation contains these versions, which many do, then they are useless. For it to be absorbed dermally vitamin E must be in the oily alcohol tocopherol form. Application of vitamin E following sun exposure will decrease the inflammation associated with sunburn.

However, is dermal application the best way to deliver the vitamin E to the skin? After ingestion vitamin E is absorbed from the gut and plasma levels rise. Vitamin E is transported in the plasma bound to the tocopherol binding protein and other lipoproteins and is subsequently incorporated into cell membranes throughout the body. The sebaceous glands secrete vitamin E containing sebum onto the skin and as a result skin concentrations of vitamin E rise with oral intake. Ingestion of vitamin E therefore results in high concentrations of vitamin in the skin. Areas that produce more sebum, such as the face, tend to have higher concentrations of vitamin E, where it is most required for protection. The skin exhibits a graduated concentration of vitamin E which is higher in the inner dermis and lower in the outer parts of the skin (stratum corneum). Therefore oral supplementation of vitamin E is also effective at protecting the skin from free radical damage, and will also protect you internally.

The advantage of oral vitamin E supplementation is that it may also protect against cardiovascular disease. Evidence suggests that cardiovascular disease is caused by low-grade systemic inflammation, one cause of which may be free radical damage. Because vitamin E is part of the cellular defences against free radicals, vitamin E may be protective of cardiovascular disease. Although the weight of evidence suggests that vitamin E is indeed protective of cardiovascular disease, not all research agrees with this conclusion and results from studies are controversial. The reason for this is likely that researchers have focused on administering alpha tocopherol to subjects, high intakes of which may decrease plasma levels of gamma tocopherol. Low levels of gamma tocopherol are found in patients with coronary heart disease, yet most of these individuals have normal levels of alpha-tocopherol. This illustrates the importance of taking a mixed tocopherol supplement, rather than single vitmer, something most researchers have been slow to acknowledge.

Therefore if you are going to supplement with vitamin E for its cardio-protective effects, try to find a formulation that contains a mix of the different vitamers of vitamin E as it is likely they have slightly different effects in the body, and evidence suggests that high doses of a single isomer may have detrimental effects on the absorption and utilisation of the other isomers. In addition, make sure that the supplement contains only the D- form of the vitamin. Just because the word ‘natural’ appears on the label does not mean it is the D-form, so make sure you check the label carefully. Avoid all of the inferior supplements that contain the DL-form of the vitamin as you will need twice the dose to get the same effect. Supplements that contain the alpha, beta, gamma and delta tocopherols are usually labelled as mixed tocopherols, but check the ingredients carefully. Skin creams should only contain the tocopherol or tocotrienol alcohol version of the vitamin. If you can not find a tocotrienol supplement eat oats every day to keep plasma levels high.