VITAMIN E

TOCOPHEROLS a group of fat-soluble vitamin E molecules

Vitamin E encompasses a group of fat-soluble compounds found primarily in vegetable oils. The compounds are known as tocopherols—a name derived from Greek words related to fertility (tókos [birth] and phérein [to bear or carry]), since researchers originally discovered that these oil components prevent sterility in rats. However, only alpha-tocopherol supplements have been shown to reverse vitamin E deficiency symptoms in humans. For this reason, it is the only form defined by the Food and Nutrition Board of the Institute of Medicine as meeting human vitamin E requirements.

Sources of vitamin E

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Some foods (such as breakfast cereals) are fortified with vitamin E, but vitamin E is also found naturally in plant-based oils—primarily those from nuts and seeds (safflower and sunflower oils are good sources), and products made with these oils (such as margarine and salad dressings). Other natural sources include wheat germ, whole nuts and seeds, and leafy green vegetables. The RDA for vitamin E for adults 19 years and older is 15 mg (22.4 IU). (INFOGRAPHIC 10.9)

INFOGRAPHIC 10.9 Dietary Sources of Vitamin E It is found in a variety of foods but the best sources are many nuts and some oils.
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Question 10.8

image What foods that you consume regularly are good sources of vitamin E?

Good sources of vitamin E include almonds, sunflower oil, avocado, olive oil, and peanut butter.

Functions of vitamin E in the body

Because of its unique ability to effectively be incorporated into cell membranes, vitamin E acts within membranes as an antioxidant, protecting cells throughout the body from the oxidative damage that results from exposure to free radicals produced in the body or present in the environment. It also helps prevent oxidative changes in low-density lipoproteins (LDLs) that may play a role in reducing plaque formation in blood vessels. (INFOGRAPHIC 10.10)

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INFOGRAPHIC 10.10 The Antioxidant Functions of Vitamin E Vitamin E can break the chain of oxidation by donating an electron to free radicals without becoming unstable. Because it is a fat-soluble vitamin it is particularly good at performing this function in cell membranes, and even in lipoproteins like LDL.
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Question 10.9

image What might be the consequences of free-radical damage to the cell's DNA?

Free-radical damage to the cell’s DNA could cause cancer.

Vitamin E appears to be of particular importance in maintaining healthy immune function by protecting white blood cells from oxidative damage, particularly in aging adults. Adequate intake of vitamin E is also necessary to prevent damage to nervous tissue. Many claims have been made about vitamin E’s potential to promote health and prevent and treat disease. Despite its role as an antioxidant, rigorous studies have not produced consistent and convincing evidence that vitamin E supplements (which are almost always alpha-tocopherol) reduce the risk of cancer or heart disease. However, recent research suggests that other forms of vitamin E that are abundant in our diet may reduce our risk of cancer, cardiovascular, and neurodegenerative diseases.

Vitamin E deficiency and toxicity

Nutrition surveys suggest Americans may be getting less vitamin E than they should, but researchers have only rarely documented deficiency in healthy adults, so specific symptoms are unclear. So, too, for toxicity—vitamin E is less likely to be toxic than either vitamin A or vitamin D, and is only observed with very high intakes from supplements, which increase the tendency to bleed. Because adverse effects have only been seen at very high levels, the UL for vitamin E (1,000 mg, or 1,500 IU) is set at more than 60 times the RDA.