Vitamin E

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Definition of Vitamin E

The most active form of vitamin E, a-tocopherol, is a 6-hydroxychroman derivative with methyl groups in position 2,5,7, and 8 and a phytyl side chain attached at carbon 2. There are 8 known forms of vitamin E: a-,b-,g-, and d-tocopherols contain saturated phytol side chains and a-, b-, g-, and d-tocotrienols have 3 double bonds in the side chain.

Structure of Vitamin E

Molecular structure of Vitamin E

It seems that d-tocotrienol is the earliest member of the group to be formed in plants, methylation leading to the other tocotrienols and hydrogenation producing the respective tocopherols.  Natural a-tocopherol, termed d-a-tocopherol, may be described chemically as 2R-(4'R,8'R)-5,7,8-trimethyltocol, the term tocol being the name for the 2-ring structure basic to all vitamin E compounds.

The term "Vitamin E" should be used for all tocopherol and tocotrienol derivatives exhibiting the biological activity of d-a-tocopherol. The term "tocopherol" should be used for all methyl tocols. Since tocotrienols have some vitamin E activity, "tocopherol" is not synonymous with "vitamin E".  http://www.cyberlipid.org/vite/vite0001.htm

Sources of Vitamin E

Note that vitamin E cannot be manufactured in the human body and is it is therefore essential that we include foods in our diets that contain this vitamin. Primarily, vitamin E can be found in the following foodstuffs:

  • Oils such as wheat germ oil, palm oil, sunflower, soybean, canola and olive
  • Nuts
  • Sunflower seeds
  • seabuckthorn berries
  • Whole grains
  • The leaves of green vegetables
  • Milk
  • Fish

General functions of Vitamin E

Vitamin E is the primary fat-soluble antioxidant. It is found notably in cellular membranes.  This fat-soluble vitamin acts as an antioxidant and may have life prolonging affects (although this is still debatable) due to its free radical scavenging ability in lipid membranes, such as those of the cells.

Effects of reduced levels of Vitamin E

The affects of greatly reduced levels of vitamin E/dietary fatty acids is associated with an increase in lipid peroxidation in fatty tissues. There are not really any obvious symptoms of vitamin E deficiency initially as this vitamin is not essential for or involved in any enzmatic reactions. This is why vitamin E is often considered more of an antioxidant, than an actual vitamin. Prolongued absence of this antioxidant from the diet however (over several decades) has been linked to such diseases as cancer and atherosclerosis (heart disease).

Effects of too much Vitamin E

If an individual overdoses on vitamin E, then they may experience the following symptoms:

  • Fatigue
  • Weakness
  • Headache
  • Flatulence
  • Diarrhoea
  • Blurred vision
  • Nausea

Vitamin E as an antioxidant

In lipid structures, it has been shown that vitamin E acts to neutralise peroxide free radicals.  When vitamin E does this it becomes itself a radical, using vitamin C to once again return to its antioxidant state.  One theory suggests that vitamin E may protect against cardiovascular disease by preventing LDL (Low density lipoprotein) oxidation from HDL (High density lipoprotein) – this is the process by which the arteries, including notably the coronary arteries become clogged with a fatty plaque.

One study (De la Fuente, M. et al 1998) was conducted of 30 elderly woman.  10 of these woman were considered healthy, 10 suffered from depression and 10 had been diagnosed with heart disease.  All of the participants took daily doses of 1000 mg of vitamin C, together with 200 mg of vitamin E for 16 weeks.  The results showed that the serum MDA levels (used to measure lipid peroxidation – damage to membranes by free radicals) dropped by 40% in the healthy woman, 65% in the woman who had been suffering from depression and by 60% in the woman with heart disease.

Vitamin E and cancer

Vitamin E has been shown to stimulate the immune system. This may result in the prevention of certain cancers due to a more competant immune sytem destroying cancerous cells at an early stage. Vitamin E also has been shown to inhibit the conversion of nitrates into nitrosamines in the stomach. These nitrates can be ingested in pickled, cured or smoked foods. Nitrosamines are STRONG tumour promotors.

Vitamin E and Athletic performance

General experimentation has not yielded results pointing towards a link between the ingestion of antioxidants and the enhancement of athletic performance. This is however with the notable exception of Vitamin E. A placebo controlled study conducted on mountaineers at altitude showed that those participants who supplemented their diet with vitamin E demonstrated less free radical damage and a reduced decline in their anaerobic threshold than did the control group. These results are not conclusive, but do point towards the benefits to physical performance of ingesting vitamin E.

To comment on vitamin E as as antioxidant or it's role in health and aging, click on this link Discussion

Mark S D'Arcy

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