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Also indexed as: Alpha Tocopherol, Tocopherol, Tocopheryl (Acetate, Succinate)
What does it do? Vitamin E is an antioxidant that protects cell membranes and other fat-soluble parts of the body, such as LDL cholesterol (the "bad" cholesterol), from damage. Only when LDL is damaged does cholesterol appear to lead to heart disease, and vitamin E is an important antioxidant protector of LDL.1 Several studies,2 3 including two double-blind trials,4 5 have reported that 400 to 800 IU of natural vitamin E per day reduces the risk of heart attacks. However, other recent double-blind trials have found either limited benefit,6 or no benefit at all from supplementation with synthetic vitamin E.7 One of the negative trials used 400 IU of natural vitamin E8 —a similar amount and form to previous successful trials. In attempting to make sense of these apparently inconsistent findings, the following is clear: less than 400 IU of synthetic vitamin E, even when taken for years, does not protect against heart disease. Whether 400 to 800 IU of natural vitamin E is, or is not, protective remains unclear.
Vitamin E also plays some role in the body's ability to process glucose. Some, but not all, trials suggest that vitamin E supplementation may eventually prove to be helpful in the prevention and treatment of diabetes.
In the last ten years, the functions of vitamin E in the cell have been further clarified. In addition to its antioxidant functions, vitamin E is now known to act through other mechanisms, including direct effects on inflammation, blood cell regulation, connective tissue growth, and genetic control of cell division.9
Where is it found? Wheat germ oil, nuts and seeds, whole grains, egg yolks, and leafy green vegetables all contain vitamin E. Certain vegetable oils should contain significant amounts of vitamin E. However, many of the vegetable oils sold in supermarkets have had the vitamin E removed in processing. The high amounts found in supplements, often 100 to 800 IU per day, are not obtainable from eating food.
Who is likely to be deficient? Severe vitamin E deficiencies are rare. People with a genetic defect in a vitamin E transfer protein called thrombotic thrombocytopenic purpura (TTP) have severe vitamin E deficiency, characterized by low blood and tissue levels of vitamin E and progressive nerve abnormalities.10 11
Low vitamin E status has been associated with an increased risk of rheumatoid arthritis 12 and major depression.13 Women with preeclampsia have been found to have lower blood levels of vitamin E than women without the condition.14
Very old people with type 2 diabetes have shown a significant age-related decline in blood levels of vitamin E, irrespective of their dietary intake.15
Which form is best? The names of all types of vitamin E begin with either "d" or "dl," which refer to differences in chemical structure. The "d" form is natural (also known as RRR-alpha tocopherol) and "dl" is synthetic (more correctly known as all-rac-alpha tocopherol). The natural form is more active and better absorbed. Little is known about how the "unnatural" "l" portion of the synthetic "dl" form affects the body, though no clear toxicity has been discovered.
In theory, when a vitamin E supplement is labeled "400 IU" it should have the same level of activity regardless of its source. This is purportedly achieved by using more synthetic vitamin E to reach the same potency as a lesser amount of natural vitamin E. For example, 100 IU of vitamin E requires about 67 mg of the natural form but closer to 100 mg of the synthetic. However, a recent review of the scientific evidence suggests that natural vitamin E probably has greater activity in the body than indicated on the label.16 Natural vitamin E may be as much as twice as bioavailable as synthetic vitamin E, not 1.36 times as is generally accepted.17 Many doctors advise people to use only the natural, the "d" form, of vitamin E.
After the "d" or "dl" designation, often the Greek letter "alpha" appears, which also describes the structure. Synthetic "dl" vitamin E is found only in the alpha form—as in "dl-alpha tocopherol." Natural vitamin E may be found either as alpha—as in "d-alpha tocopherol"—or in combination with beta, gamma, and delta, labeled "mixed"—as in mixed natural tocopherols.
Little is known about the importance of the beta and delta forms of vitamin E, but a debate has arisen concerning gamma tocopherol. In a test tube study, gamma tocopherol was found to be more effective than alpha tocopherol in protecting against certain specific types of oxidative damage.18 In addition, some researchers have hypothesized that alpha tocopherol might interfere with the activity of gamma tocopherol, although this idea remains unproven.
Human trials with vitamin E have almost always been done with the alpha (not gamma) form. Historically the synthetic "dl" form was used in most trials, but some trials are now using the natural form. The issue of alpha vs. gamma form requires more research before it can be fully understood.
Almost all vitamin E research shows that, when positive results are obtained, hundreds of units per day are required—an amount easily obtained with supplements but impossible with food. Therefore, switching to food sources, as suggested by some researchers, is impractical. On the other hand, the vitamin E occurring naturally in food contains gamma tocopherol and other tocopherols. Thus, it possibly may turn out to be more effective than the vitamin E taken in supplement form. Additional research is needed in this area.
Vitamin E forms are listed as either plain "tocopherol" or tocopheryl followed by the name of what is attached to it, as in "tocopheryl acetate." The two forms are not greatly different. However, plain tocopherol may be absorbed a little better, while tocopheryl attached forms have a slightly better shelf life. Both forms are active when taken by mouth. However, the skin utilizes the tocopheryl forms very slowly,19 20 so those planning to apply vitamin E to the skin should buy plain tocopherol. In health food stores, the most common forms of vitamin E are d-alpha tocopherol and d-alpha tocopheryl acetate or succinate. Both of these d (natural) alpha forms are frequently recommended by doctors. Although the succinate form is slightly weaker than the acetate form, more milligrams of the succinate form are added to supplements to compensate for this small difference in potency. Therefore, 400 IU of either form should have equivalent potency.
How much is usually taken? The recommended dietary allowance for vitamin E is low, just 15 mg or approximately 22 International Units (IU) per day. The most commonly recommended amount of supplemental vitamin E for adults is 400 to 800 IU per day. However, some leading researchers suggest taking only 100 to 200 IU per day, since trials that have explored the long-term effects of different supplemental levels suggest no further benefit beyond that amount. In addition, research reporting positive effects with 400 to 800 IU per day has not investigated the effects of lower intakes.21 For tardive dyskinesia, the best results have been achieved from 1,600 IU per day,22 a large amount that should be supervised by a healthcare practitioner.
Are there any side effects or interactions? Vitamin E toxicity is very rare and supplements are widely considered to be safe. The National Academy of Sciences has established the daily tolerable upper intake level for adults to be 1,000 mg of vitamin E, which is equivalent to 1,500 IU of natural vitamin E or 1,100 IU of synthetic vitamin E.23
In contrast to trials suggesting vitamin E improves glucose tolerance in people with diabetes, one trial reported that 600 IU per day of vitamin E led to impairment in glucose tolerance in obese people with diabetes.24 The reason for the discrepancy between reports is not known.
Patients on kidney dialysis who are given injections of iron frequently experience "oxidative stress." This is because iron is a pro-oxidant, meaning that it interacts with oxygen molecules in ways that may damage tissues. These adverse effects of iron therapy may be counteracted by supplementation with vitamin E.25
A diet high in unsaturated fat increases vitamin E requirements. Vitamin E and selenium work together to protect fat-soluble parts of the body.
What does it do? Vitamin E is an antioxidant that protects cell membranes and other fat-soluble parts of the body, such as LDL cholesterol (the "bad" cholesterol), from damage. Only when LDL is damaged does cholesterol appear to lead to heart disease, and vitamin E is an important antioxidant protector of LDL.1 Several studies,2 3 including two double-blind trials,4 5 have reported that 400 to 800 IU of natural vitamin E per day reduces the risk of heart attacks. However, other recent double-blind trials have found either limited benefit,6 or no benefit at all from supplementation with synthetic vitamin E.7 One of the negative trials used 400 IU of natural vitamin E8 —a similar amount and form to previous successful trials. In attempting to make sense of these apparently inconsistent findings, the following is clear: less than 400 IU of synthetic vitamin E, even when taken for years, does not protect against heart disease. Whether 400 to 800 IU of natural vitamin E is, or is not, protective remains unclear.
Vitamin E also plays some role in the body's ability to process glucose. Some, but not all, trials suggest that vitamin E supplementation may eventually prove to be helpful in the prevention and treatment of diabetes.
In the last ten years, the functions of vitamin E in the cell have been further clarified. In addition to its antioxidant functions, vitamin E is now known to act through other mechanisms, including direct effects on inflammation, blood cell regulation, connective tissue growth, and genetic control of cell division.9
Where is it found? Wheat germ oil, nuts and seeds, whole grains, egg yolks, and leafy green vegetables all contain vitamin E. Certain vegetable oils should contain significant amounts of vitamin E. However, many of the vegetable oils sold in supermarkets have had the vitamin E removed in processing. The high amounts found in supplements, often 100 to 800 IU per day, are not obtainable from eating food.
Who is likely to be deficient? Severe vitamin E deficiencies are rare. People with a genetic defect in a vitamin E transfer protein called thrombotic thrombocytopenic purpura (TTP) have severe vitamin E deficiency, characterized by low blood and tissue levels of vitamin E and progressive nerve abnormalities.10 11
Low vitamin E status has been associated with an increased risk of rheumatoid arthritis 12 and major depression.13 Women with preeclampsia have been found to have lower blood levels of vitamin E than women without the condition.14
Very old people with type 2 diabetes have shown a significant age-related decline in blood levels of vitamin E, irrespective of their dietary intake.15
Which form is best? The names of all types of vitamin E begin with either "d" or "dl," which refer to differences in chemical structure. The "d" form is natural (also known as RRR-alpha tocopherol) and "dl" is synthetic (more correctly known as all-rac-alpha tocopherol). The natural form is more active and better absorbed. Little is known about how the "unnatural" "l" portion of the synthetic "dl" form affects the body, though no clear toxicity has been discovered.
In theory, when a vitamin E supplement is labeled "400 IU" it should have the same level of activity regardless of its source. This is purportedly achieved by using more synthetic vitamin E to reach the same potency as a lesser amount of natural vitamin E. For example, 100 IU of vitamin E requires about 67 mg of the natural form but closer to 100 mg of the synthetic. However, a recent review of the scientific evidence suggests that natural vitamin E probably has greater activity in the body than indicated on the label.16 Natural vitamin E may be as much as twice as bioavailable as synthetic vitamin E, not 1.36 times as is generally accepted.17 Many doctors advise people to use only the natural, the "d" form, of vitamin E.
After the "d" or "dl" designation, often the Greek letter "alpha" appears, which also describes the structure. Synthetic "dl" vitamin E is found only in the alpha form—as in "dl-alpha tocopherol." Natural vitamin E may be found either as alpha—as in "d-alpha tocopherol"—or in combination with beta, gamma, and delta, labeled "mixed"—as in mixed natural tocopherols.
Little is known about the importance of the beta and delta forms of vitamin E, but a debate has arisen concerning gamma tocopherol. In a test tube study, gamma tocopherol was found to be more effective than alpha tocopherol in protecting against certain specific types of oxidative damage.18 In addition, some researchers have hypothesized that alpha tocopherol might interfere with the activity of gamma tocopherol, although this idea remains unproven.
Human trials with vitamin E have almost always been done with the alpha (not gamma) form. Historically the synthetic "dl" form was used in most trials, but some trials are now using the natural form. The issue of alpha vs. gamma form requires more research before it can be fully understood.
Almost all vitamin E research shows that, when positive results are obtained, hundreds of units per day are required—an amount easily obtained with supplements but impossible with food. Therefore, switching to food sources, as suggested by some researchers, is impractical. On the other hand, the vitamin E occurring naturally in food contains gamma tocopherol and other tocopherols. Thus, it possibly may turn out to be more effective than the vitamin E taken in supplement form. Additional research is needed in this area.
Vitamin E forms are listed as either plain "tocopherol" or tocopheryl followed by the name of what is attached to it, as in "tocopheryl acetate." The two forms are not greatly different. However, plain tocopherol may be absorbed a little better, while tocopheryl attached forms have a slightly better shelf life. Both forms are active when taken by mouth. However, the skin utilizes the tocopheryl forms very slowly,19 20 so those planning to apply vitamin E to the skin should buy plain tocopherol. In health food stores, the most common forms of vitamin E are d-alpha tocopherol and d-alpha tocopheryl acetate or succinate. Both of these d (natural) alpha forms are frequently recommended by doctors. Although the succinate form is slightly weaker than the acetate form, more milligrams of the succinate form are added to supplements to compensate for this small difference in potency. Therefore, 400 IU of either form should have equivalent potency.
How much is usually taken? The recommended dietary allowance for vitamin E is low, just 15 mg or approximately 22 International Units (IU) per day. The most commonly recommended amount of supplemental vitamin E for adults is 400 to 800 IU per day. However, some leading researchers suggest taking only 100 to 200 IU per day, since trials that have explored the long-term effects of different supplemental levels suggest no further benefit beyond that amount. In addition, research reporting positive effects with 400 to 800 IU per day has not investigated the effects of lower intakes.21 For tardive dyskinesia, the best results have been achieved from 1,600 IU per day,22 a large amount that should be supervised by a healthcare practitioner.
Are there any side effects or interactions? Vitamin E toxicity is very rare and supplements are widely considered to be safe. The National Academy of Sciences has established the daily tolerable upper intake level for adults to be 1,000 mg of vitamin E, which is equivalent to 1,500 IU of natural vitamin E or 1,100 IU of synthetic vitamin E.23
In contrast to trials suggesting vitamin E improves glucose tolerance in people with diabetes, one trial reported that 600 IU per day of vitamin E led to impairment in glucose tolerance in obese people with diabetes.24 The reason for the discrepancy between reports is not known.
Patients on kidney dialysis who are given injections of iron frequently experience "oxidative stress." This is because iron is a pro-oxidant, meaning that it interacts with oxygen molecules in ways that may damage tissues. These adverse effects of iron therapy may be counteracted by supplementation with vitamin E.25
A diet high in unsaturated fat increases vitamin E requirements. Vitamin E and selenium work together to protect fat-soluble parts of the body.