What is vitamin E?
Even though its name makes it sound like a single substance, vitamin E is actually a family of fat-soluble vitamins that are active throughout the body. Some members of the vitamin E family are called tocopherols. These members include alpha tocopherol, beta tocopherol, gamma tocopherol, and delta tocopherol.
Other members of the vitamin E family are called tocotrienols. These members include alpha, beta, gamma, and delta tocotrienol. As increasing information has become available about these forms of vitamin E, more and more of them are understood to have unique functions.
What is the function of vitamin E?
Prevention of oxidative stress
Although humans must breathe oxygen to stay alive, oxygen is a risky substance inside the body because it can make molecules overly reactive. When oxygen-containing molecules become too reactive, they can start damaging the cell structures around them. In chemistry, this imbalanced situation involving oxygen is called oxidative stress.
Vitamin E helps prevent oxidative stress by working together with a group of nutrients that prevent oxygen molecules from becoming too reactive. This group of nutrients includes vitamin C, glutathione, selenium, and vitamin B3. Some researchers believe that vitamin E is the most important member of this oxidative stress-preventing group.
Supporting healthy skin
Vitamin E has sometimes been described as the "lightening rod" of the cell, allowing reactive molecules to strike the cell, like lightening, without causing damage. This "lightening rod" function of vitamin E is particularly apparent in the case of the skin, since vitamin E directly protects the skin from ultraviolet radiation (also called UV light). In numerous research studies, vitamin E applied topically to the skin has been shown to prevent UV damage. When the diet contains vitamin E-rich foods, vitamin E can travel to the skin cell membranes and exert this same protective effect.
Protection against Bladder Cancer
One of the benefits of making foods rich in vitamin E-nuts, seeds, spinach, mustard greens, peppers and olive oil-a part of your healthy way of eating is an up to 50% reduction in risk of developing bladder cancer, according to research presented at the annual meeting of the American Association of Cancer Research,
Bladder cancer, which kills 12,500 Americans annually, is the fourth leading cancer killer among men, and is four times more common in men than women. The study, which included 468 bladder cancer patients and 534 cancer-free controls drawn from residents of
Increasing vitamin E intake to the amount consumed by those in the top group would not be difficult since the actually difference in the amount of vitamin E-rich foods the two extremes consumed was small-the equivalent of a single daily serving of spinach or a handful of almonds.
The research team looked at the two most common forms of vitamin E, alpha- and gamma-tocopherol, and found that only alpha-tocopherol was associated with lower bladder cancer risk. Also, whether study participants got their vitamin E from food alone or from vitamin pills, the reduction in risk was roughly the same. Those with the highest intake of alpha-tocopherol from food had a 42% reduced risk of bladder cancer, and those with a vitamin E rich diet who also took vitamin E supplements had a 44% reduced risk.
Vitamin E from Foods, but not Supplements Offers Protection against Prostate Cancer and Alzheimer's Disease
While the type of vitamin E usually used in supplements is alpha-tocopherol, research published in the December 2004 issue of the Proceedings of the National Academy of Sciences indicates another form of vitamin E, gamma-tocopherol, but not alpha-tocopherol, inhibits prostate cancer cell proliferation, without affecting healthy prostate cells.
Plus, the anti-cancer effect of gamma-tocopherol, when combined with other forms of vitamin E such as delta-tocopherol, appears to be additive.
As noted above, Vitamin E is a generic term for a family of at least eight structurally related molecules. When the first research was conducted on vitamin E by the Shute brothers early in the 19th century, in rats, one fraction of vitamin E, alpha tocopherol, appeared more potent since it was necessary for successful pregnancy and production of offspring. For this reason, the Shutes named the vitamin "tocopherol," from the Greek word meaning "to give birth."
More recent research has revealed that, in humans, other vitamin E fractions may be even more beneficial. Gamma-tocopherol has been found to exhibit anti-inflammatory effects, which has led researchers to think this fraction may be more cardioprotective than the alpha-tocopherol found in most supplements. Not only is gamma-tocopherol anti-inflammatory, but it is also highly attracted to the nucleus in cells-the site where mutations in the genetic code can promote the development of cancer.
When Dr. Jiang and his team investigated the anti-carcinogenic potential of various forms of vitamin E, they found that gamma-tocopherol, particularly in combination with other forms of vitamin E such as delta-tocopherol, induced apoptosis (cell death) in androgen-sensitive prostate cancer cells within 3 days of treatment. Alpha-tocopherol alone did not have this effect.
The gamma and delta E fractions appear to induce apoptosis by interrupting the synthesis of sphingolipid, a fatty molecule in cell membranes that acts as a signaling messenger to modulate events inside the cell. In the cell membranes of human prostate cancer cells, the interruption of sphingolipid's synthesis by gamma and delta tocopherols causes the cancerous cells to self-destruct, while leaving healthy cells unaffected. Both fractions, as well as alpha tocopherol, are naturally present in foods rich in vitamin E, which include a number of greens (mustard greens, turnip greens, spinach, collard greens, and kale), sunflower seeds and almonds.
A high intake of vitamin E from food, but not from supplements (which usually contain just alpha-tocopherol) is also inversely associated with Alzheimer's disease.
Other roles for vitamin E
While most of the research on vitamin E has focused on its role in prevention of oxidative stress, a variety of new roles have recently been suggested. Most of these new roles involve the transfer of chemical information from one cell to another, or across different structures inside of a cell. This transfer of chemical information is referred to as "cell signaling," and many researchers believe that cell signaling cannot accurately take place without the help of vitamin E.
What are deficiency symptoms for vitamin E ?
Deficiency symptoms for vitamin E are difficult to pinpoint and controversial in the research literature. The area of broadest agreement involves malabsorption. In many research studies, low levels of vitamin E are associated with digestive system problems where nutrients are poorly absorbed from the digestive tract. These problems include pancreatic disease, gallbladder disease, liver disease, and celiac disease.
A second area of focus for vitamin E deficiency symptoms is called peripheral neuropathy. This area focuses on nervous system problems in the arms, hands, legs, and feet. Pain, tingling, and loss of sensation in these extremities have been associated with vitamin E deficiency. Although many healthcare practitioners report that skin problems appear closely linked to vitamin E deficiency, there are limited human research studies to support this view.
What forms of vitamin E are found in dietary supplements?
The vast majority of vitamin E supplements contain a single form of the vitamin, alpha-tocopherol. More specifically, most supplements contain a natural form of alpha-tocopherol, called d-alpha tocopherol (or d-alpha tocopheryl acetate). Practitioners often prefer this form of the vitamin over a synthetic version called l-alpha tocopherol.
However, because vitamin E is actually a family of vitamins involving many tocopherols and many tocotrienols, some practitioners recommend vitamin E supplements containing not only d-alpha tocopherol, but other tocopherol and tocotrienol forms of vitamin E.
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