Vitamin E: What you need to know

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Vitamin E: What you need to know

By Liu, Ph.D.

What is vitamin E?

Vitamin E is a group of eight nutrients including four tocopherols,

(alpha-, beta-, gamma- and delta-) and four tocotrienols (alpha-,

beta-, gamma- and delta-). Alpha-tocopherol is the only form of

vitamin E that is active in the body.

What does vitamin E do in the body?

The form of vitamin E most known today is alpha-tocopherol, which is

believed to be used in the body mainly as an antioxidant.

Antioxidants are expected to neutralize free radials endogenously and

oxidative environmental pollutants.

Alpha-tocopherol is fat-soluble and helps protect against oxidation

of fatty components in the cell membrane and also protect fats in low

density liporpoteins (LDLs), which transport cholesterol from the

liver to the tissue of the body. Oxidation of LDLs could lead to

development of cardiovascular diseases.

Alpha-tocopherol also affects some enzymes and the production of

immune and inflammatory cells among other things.

The functions of other forms of vitamin E are not as well understood.

What are the consequences of vitamin E deficiency?

Vitamin E deficiency could be caused either by low intake of the

vitamin or by some conditions that disable the alpha-tocopherol

transfer protein or by some problem with fat absorption. Those who

can't absorb fat such as patients with cystic fibrosis or cholesterol

liver disease would have a problem with absorbing this vitamin from

the diet, potentially leading to vitamin E deficiency.

The main consequences of severe vitamin E deficiency are neurological

symptoms such as ataxia (impaired balance and coordination),

peripheral neuropathy (injury to sensory nerves, myopathy (muscle

weakness) and pigmented retinopathy (damage to the eye retina).

People who experience these symptoms should be checked for their

vitamin E status. Children are more sensitive and thus more

vulnerable to vitamin E deficiency and they can quickly show

neurological symptoms while adults may not develop symptoms due to

the deficiency for 10 to 20 years.

Vitamin E deficiency due to low intake of this nutrient rarely

results in any reported symptoms. In effect, vitamin E deficiency

due to low dietary intake is rare although suboptimal intake of this

nutrient is found common in the U.S. population. A study known as the

U.S. National Health and Nutrition Examination Survey III (NHANES

III) showed 27 % of whites, 41% of blacks, 28% Mexican Americans and

32% of others have less than 20 micromoles/liter, a level of vitamin

E that is believed to pose a risk for cardiovascular disease.

What is the recommended dietary allowance for vitamin E?

The RDA set by the Food and Nutrition Board of the Institute of

Medicine in 2000 varies with age. The RDA for both adult males and

females is 15 mg or 22.5 IU per day. Pregnancy does not require

extra vitamin E, but breastfeeding mother need 19 mg or 28.5 IU per

day.

What are the conditions or diseases on which vitamin E may have an

effect?

Observational studies have showed an association between increased

vitamin E intake and decreased risk of myocardial infarction or heart

attack or death from heart disease in both men and women. Studies

also found plasma levels of alpha-tocopherol were inversely linked to

the severity of carotid atherosclerosis. But trials often failed to

see any protective effect of this vitamin on heart attacks and death.

Observational studies also showed vitamin E may protect against

cataracts, but interventional trials did not find any protective

effect when 400 IU of vitamin E was used for 7 years.

Alpha-tocopherol was also found to boost the immune response. One

study showed 200 mg of synthetic-tocopherol daily for a few months

increased production of antibodies in response to hepatitis B vaccine

and tetanus vaccine in elderly people.

Because free radials are believed to cause damage to DNA,

neutralization of these compounds by antioxidant vitamins such as

vitamin E is believed to have a preventative effect against cancer.

But many studies showed that vitamin E supplements were not linked to

reduced risk of cancer. In a recent study, vitamin E supplementation

for ten years was found even to increase the risk of lung cancer in

current smokers.

What are the foods that contain high levels of vitamin E?

The major dietary sources of alpha-tocopherol include vegetable oils

such as olive, sunflower and safflower oils; nuts such as almonds,

hazelnuts and peanuts; whole grains products; and green leafy

vegetables such as spinach. All eight forms of vitamin E occur

naturally in foods.

Those who would use vitamin E supplements should check and see if the

form they buy is natural or synthetic. They may better off buying

and using only the natural form. The synthetic form of vitamin is

biochemically not usable by the body and potentially cause a

physiologic problem in the body. The natural form in food (not the

fortified) is the form of the isomer, RRR-alpha-tocopherol. In

supplemental vitamin E, dl-alpha-tocopherol or all-rac-alpha-

tocopherol means the vitamin is synthetic.

There are some other forms of vitamin E or derivatives used in

supplements. Foodconsumer.org recommends use of the natural form d-

alpha-tocopherol.

What are the possible side effects of vitamin E?

Vitamin E is fat-soluble and too much of its intake through

supplements may cause some side effects. But the Food and Nutrition

Board of the Institute of Medicine believes 1000 mg or 1500 IU of

alpha-tocopherol per day can be tolerated by adults aged 19 or

older. The dietary intake of this vitamin rarely poses any risk.