Vitamin E

Uses

Supplementation with vitamin E may be necessary in people who have digestive disorders, including chronic bowel disease, or those who have undergone gastrointestinal surgeries since their systems are less able to absorb fat-soluble vitamins.

Heart Disease

Many population studies have found that people with higher levels of vitamin E in their bodies have a lower risk of heart disease. Researchers have investigated whether taking vitamin E supplements might help prevent heart disease, but the results have not shown any benefit.

One of the largest studies, the Heart Outcomes Prevention Evaluation (HOPE) trial, found that taking 400 IU of vitamin E (d-alpha-tocopherol) daily did not lower the number of heart attacks, strokes, or deaths from heart disease among men and women who already had heart disease, or those who were at high risk for developing it.

Among otherwise healthy people who were at low risk for heart disease, two large trials also found no protection from vitamin E. In one, the Physicians' Health Study II, vitamin E was associated with a higher risk of stroke. This study generated a lot of controversy and is still being debated today.

One large clinical study suggested that vitamin E from foods, not supplements, may reduce the risk of death from stroke in postmenopausal women.

Cancer

Population studies (observing large groups of people over time) suggest that eating foods high in vitamin E and other antioxidants may help prevent cancer. Other studies show that people with cancer often have lower levels of vitamin E. Researchers wondered if antioxidants like vitamin E can help prevent cancer. But evidence about vitamin E supplements has not backed this up.

Several large studies show that women who take vitamin E supplements do not have a lower risk of developing breast cancer. One large study found that men who took 400 IU of vitamin E every other day for 8 years did not have a lower risk of overall cancer than those who took placebo.

Vitamin E also does not seem to protect against colorectal cancer in women or people with diabetes. There is some evidence that taking vitamin E, along with vitamin A and vitamin C, or as part of a multivitamin, may offer some protection to people who had colorectal adenomas. Colorectal adenomas are considered to be a precursor to developing colon cancer.

Vitamin E does not seem to protect against lung cancer or pancreatic cancer. In fact, one study of more than 77,000 men showed a small but significant increase in lung cancer associated with taking vitamin E supplements.

The evidence about vitamin E and prostate cancer is mixed. Some population studies suggest that people who take more vitamin E have a lower risk of prostate cancer. Other studies suggest the opposite: One study found that men who took a multivitamin more than 7 times per week, along with a separate vitamin E supplement, had a higher risk of prostate cancer. Another study of 35,000 men found that those who took a vitamin E supplement had a 17% increase in the risk of developing prostate cancer than those who took placebo.

One study found that taking a combination of 30 mg vitamin E (alpha-tocopherol), 120 mg vitamin C, 6 mg beta-carotene, 100 mcg selenium, and 20 mg zinc did not lower the overall risk of prostate cancer, but it might reduce the risk in men whose PSA levels were normal. High PSA levels can indicate prostate cancer.

Another large study of 29,133 smokers found that those taking 50 mg daily of vitamin E (dl-alpha-tocopherol, or synthetic vitamin E) had a lower risk of prostate cancer and deaths caused by prostate cancer.

Researchers note that taking antioxidant supplements may not work as well as eating antioxidant foods. Many experts believe getting antioxidants from foods may be the best way to protect against cancer.

Also, there is only limited evidence that taking large doses of vitamin E may help with cancer treatment. One study of 108 people taking the chemotherapy therapy drug cisplatin found that taking a vitamin E supplement during, and as long as 3 months after, treatment reduced nerve damage that can happen when taking cisplatin. However, some doctors worry that large doses of antioxidants from supplements could interfere with chemotherapy medications. If you are undergoing chemotherapy, talk to your doctor before taking vitamin E or any supplement.

The most recent evidence seems to suggest that dietary vitamin E and low-dose tocopherols are cancer preventive, while high-dose supplementation with alpha tocopherol is not. Research is ongoing. Consult a physician to determine the role of vitamin E in specific cases.

Photodermatitis

This condition involves an allergic type reaction to the UV rays of the sun. An 8-day clinical study comparing treatment with vitamins C and E to placebo found that people who took the vitamins became significantly less sensitive to the sun. Another clinical study, lasting for 50 days, also showed a protective effect of the vitamin C and E combination.

Alzheimer Disease

Evidence is mixed as to whether vitamin E can help prevent or treat Alzheimer disease. Some researchers believe that antioxidants may help prevent Alzheimer disease. One study found that people who had levels of all the forms of vitamin E, not just d-alpha-tocopherol, the kind usually found in supplements, were less likely to develop Alzheimer's. But another study found that people who had early symptoms of Alzheimer's and took vitamin E supplements went on to develop the disease at the same rate as those who took placebo.

In one study with positive results, 341 people with Alzheimer disease took either 2,000 IU of vitamin E (dl-alpha-tocopherol), the drug selegiline, or placebo. Those who were given vitamin E took about 200 days longer for the disease to progress to severe than those who took placebo. However, selegiline worked even better.

Eye Health

Vitamin E (400 IU) combined with other antioxidants, including zinc (80 mg), beta-carotene (15mg), and vitamin C (500 mg), seems to protect against developing age-related macular degeneration (AMD). AMD is the leading cause of legal blindness in people over 55 in the United States. People with advanced AMD seemed to get the biggest benefit. Researchers do not know whether this combination of nutrients helps prevent AMD or helps people with less advanced AMD.

Vitamins E and C may also help treat uveitis. Uveitis is inflammation of the uvea, the middle layer of the eye between the sclera (white outer coat of the eye) and the retina. A clinical study of 130 people with uveitis found that those who took these vitamins had clearer vision than those who took placebo.

Menstrual Pain

A few studies have found that vitamin E may help relieve menstrual pain or dysmenorrhea. In one study, women who took 500 IU of vitamin E for 2 days before and 3 days after their periods started had less pain than those who took placebo.

A few studies also suggest that vitamin E supplements may help reduce PMS symptoms, including anxiety, food cravings, and depression.

Diabetes

People with diabetes tend to have low levels of antioxidants, which has led some researchers to believe that this might explain why they are at increased risk for conditions such as heart disease.

Vitamin E supplements and other antioxidants may help reduce the risk of heart disease and other complications in people with diabetes. Research shows that antioxidants may help control blood sugar levels and lower cholesterol levels in people with type 2 diabetes while protecting against the complications of eye damage (retinopathy) and kidney damage (nephropathy) in those with type 1 diabetes. One study found that people with type 2 diabetes who took 400 IU of vitamin E daily reduced their risk of heart attack and of dying from heart disease.

However, not all studies have found that taking vitamin E supplements helps people with diabetes. If you have diabetes, ask your doctor whether a vitamin E supplement is right for you.

Pre-eclampsia

Some studies suggest that taking vitamin E along with vitamin C may help prevent pre-eclampsia in women who are at high risk. Women with pre-eclampsia have high blood pressure and too much protein in the urine. Pre-eclampsia is a common cause of premature births. Not all studies agree, however. Women should speak with their physicians before taking vitamin E during pregnancy.

Tardive dyskinesia

Some small studies have suggest that vitamin E supplements may help treat tardive dyskinesia, involuntary, repetitive movements that are a side effect of taking certain medications for a long time. However, not all studies have found that vitamin E can help. The largest study found that taking 1,600 IU of vitamin E daily for at least one year was no better at reducing tardive dyskinesia symptoms than placebo.

Rheumatoid arthritis

One study suggests that taking vitamin E, along with standard medications for rheumatoid arthritis, may help reduce pain, but not inflammation, better than standard medications alone.

Dietary Sources

The richest source of vitamin E is wheat germ.

Other foods that contain a significant amount of vitamin E include:

• Liver
• Eggs
• Nuts -- almonds, hazelnuts, and walnuts
• Sunflower seeds
• Corn-oil margarine
• Mayonnaise
• Cold-pressed vegetable oils, including olive, corn, safflower, soybean, cottonseed, and canola
• Dark green leafy vegetables like spinach and kale
• Cereal grains
• Greens -- beet, collard, mustard, turnip
• Sweet potatoes
• Avocado
• Asparagus
• Yams

Available Forms

There are natural and synthetic forms of vitamin E. Health care providers usually recommend natural vitamin E (d-alpha-tocopherol) or natural mixed tocopherols. Some prefer mixed tocopherols because they most closely represent whole foods. The synthetic form is called dl-alpha-tocopherol. Dosages are usually listed in international units (IU).

Most vitamin E supplements are fat soluble. However, people who have trouble absorbing fat, such as those with pancreatic problems or cystic fibrosis, can take water-soluble E.

Vitamin E is available in softgels, tablets, capsules, and topical oils.

How to Take It

Doses for oral vitamin E generally range from 50 to 1,000 IU. Experts recommend getting vitamin E mostly from food rather than supplements.

The Food and Nutrition Board of the Institute of Medicine has set an upper tolerable intake level (UL) for vitamin E at 1,000 mg (1,500 IU) per day for supplemental vitamin E.

Based on clinical trials, the dose often used for disease prevention and treatment for adults is 400 to 800 IU per day. As with all supplements, you should check with a health care provider before giving vitamin E to a child.

Daily intakes of dietary vitamin E are listed below. (Note: 1 mg vitamin E equals 1.5 IU.)

Pediatric

• Newborn to 6 months: 6 IU
• Infants 7 months to 1 year: 7.5 IU
• Children 1 to 3 years: 9 IU
• Children 4 to 8 years: 10.4 IU
• Children 9 to 13 years: 16.4 IU
• Adolescents 14 to 18 years: 22.4 IU

Adult

• Older than 18 years: 22.4 IU
• Pregnant females: 22.4 IU
• Breast-feeding females: 28.4 IU

Precautions

Always check with your doctor before taking vitamin E supplements. Vitamin E may increase the risk of bleeding, especially if you are taking blood thinners, such as warfarin (Coumadin), aspirin, or clopidogrel (Plavix).

Possible Interactions

If you are being treated with any of the following medications, you should not use vitamin E supplements without first talking to your health care provider:

Antidepressant medications. Vitamin E interferes with the absorption of the antidepressant desipramine (Norpramin). Desipramine belongs to a class of drugs known as tricyclics. Other tricyclics include imipramine (Tofranil) and nortriptyline (Pamelor).

Antipsychotic medications. Vitamin E can interfere with the body's absorption of the antipsychotic medication called chlorpromazine (Thorazine). Chlorpromazine belongs to a class of drugs known as phenothiazines.

Aspirin. Because vitamin E can increase the risk of bleeding, people who take aspirin should talk to their doctor before taking vitamin E supplements.

AZT. Vitamin E may protect against toxicity and side effects from AZT, a medication used to treat HIV and AIDS.

Beta-blockers. This type of medication is used to treat high blood pressure. Vitamin E interferes with the body's absorption of propranolol (Inderal), a kind of beta-blocker. Other beta-blockers include:

• Acebutolol (Sectral)
• Atenolol (Tenormin)
• Bisoprolol (Zebeta)
• Carteolol (Cartrol)
• Metoprolol (Toprol XL)
• Nadolol (Corgard)
• Propranolol (Inderal)

Bile acid sequestrants. These medications, used to lower cholesterol, may reduce how much vitamin E your body absorbs. These medications include:

• Cholestyramine (Questran, Prevalite)
• Cholestipol (Colestid)

Statins. Taking a combination of antioxidants, including vitamins E and C, selenium, and beta-carotene, along with niacin and simvastatin (Zocor) seems to keep niacin and Zocor from raising HDL (good) cholesterol. Researchers do not know whether vitamin E alone would have the same effect, or whether it would happen with other statins. Ask your doctor before taking vitamin E if you also take a statin. Statins include:

• Lovastatin (Mevacor)
• Simvastatin (Zocor)
• Pravastatin (Pravachol)
• Atorvastatin (Lipitor)
• Fluvastatin (Lescol)
• Rosuvastatin (Crestor)

Gemfibrozil. This medication, used to lower cholesterol, may also reduce vitamin E levels.

Cyclosporine. Vitamin E may interact with cyclosporine, a medication used to treat cancer, making both vitamin E and cyclosporine less effective. However, another study suggests that the combination of vitamin E and cyclosporine may actually make cyclosporine work better. Ask your doctor before taking vitamin E if you take cyclosporine.

Chemotherapy drugs. Some doctors worry that antioxidants like vitamin E may reduce the effectiveness of chemotherapy drugs, including chlorambucil, busulfan, doxorubicine, carmustine, thiopeta, and cyclophosphamideradicals. However, other researchers think that antioxidants may make chemotherapy work better. Talk to your oncologist before taking vitamin E or any supplement.

Tamoxifen. Tamoxifen, a treatment for breast cancer, boosts blood levels of triglycerides, increasing the risk of developing high cholesterol. In a study of 54 women with breast cancer, vitamins C and E, taken along with tamoxifen, reduced this side effect. These vitamins reduced LDL (bad) cholesterol and triglyceride levels while raising HDL (good) cholesterol. Vitamins C and E also made the anticancer action of the tamoxifen stronger.

Warfarin (Coumadin). Taking vitamin E at the same time as other blood thinners can increase the risk of bleeding.

Orlistat (Alli). This medication is used for weight loss. It stops your body from absorbing some fat and calories. It may also prevent the absorption of fat-soluble vitamins, including vitamin E. Doctors who prescribe orlistat may add a multivitamin with fat-soluble vitamins.

Vitamin E may also interact with:

Calcium channel blockers, including:

• Nifedipine (Procardia)
• Amlodipine (Norvasc)
• Verapamil (Calan, Isoptin)
• Diltiazem (Cardizem)
• Felodipine (Plendil)
• Nisoldipine (Sular)
• Bepridil (Vascor)

Others include:

• Cisapride (Propulsid)
• Fluoxetine (Prozac)
• Fexofenadine (Allegra)
• Omeprazole (Prilosec)

Supporting Research

Albanes D, Malila N, Taylor PR, et al. Effects of supplemental alpha-tocopherol and beta-carotene on colorectal cancer: results from a controlled trial (Finland). Cancer Causes Control. 2000;11:197-205.

Ames BN. Micronutrient deficiencies: A major cause of DNA damage. Ann NY Acad Sci. 2000;889:87-106.

Babu JR, Sundravel S, Arumugam G, Renuka R, Deepa N, Sachdanandam P. Salubrious effect of vitamin C and vitamin E on tamoxifen-treated women in breast cancer with reference to plasma lipid and lipoprotein levels. Cancer Lett. 2002;151:1-5.

Bhardwaj P, Thareja S, Prakash S, Saraya A. Micronutrient antioxidant intake in patients with chronic pancreatitis. Trop Gastroenterol. 2004 Apr-Jun;25(2):69-72.

Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2008 Apr 16;(2):CD007176. Review.

Cai J, Nelson KC, Wu M, Sternberg P Jr, Jones DP. Oxidative damage and protection of the RPE. Prog Retin Eye Res. 2000;19(2):205-21.

Capuron L, Moranis A, Combe N, Cousson-Gélie F, Fuchs D, De Smedt-Peyrusse V, Barberger-Gateau P, Layé S. Vitamin E status and quality of life in the elderly: influence of inflammatory processes. Br J Nutr. 2009 Nov;102(10):1390-4.

Chae CU, Albert CM, Moorthy MV, Lee IM, Buring JE. Vitamin E supplementation and the risk of heart failure in women. Circ Heart Fail. 2012;5(2):176-82.

Choi HK. Dietary risk factors for rheumatic diseases. Curr Opin Rheumatol. 2005 Mar;17(2):141-6.

Chrubasik S. Vitamin E for rheumatoid arthritis or osteoarthritis: low evidence of effectiveness. Z Rheumatol. 2003 Oct;62(5):491.

Collaborative Group of the Primary Prevention Project. Low-dose aspirin and vitamin E in people at cardiovascular risk: a randomised trial in general practice. Lancet. 2001;357:89-95.

Debreceni B, Debreceni L. Why do homocysteine-lowering B vitamin and antioxidant E vitamin supplements appear to be ineffective in the prevention of cardiovascular disease? Cardiovasc Ther. 2012;30(4):227-33.

Dutta A, Dutta SK. Vitamin E and its role in the prevention of atherosclerosis and carcinogenesis: a review. J Am Coll Nutr. 2003 Aug;22(4):258-68.

Farina N, Isaac MG, Clark AR, Rusted J, Tabet N. Vitamin E for Alzheimer's dementia and mild cognitive impairment. Cochrane Database Syst Rev. 2012;11:CD002854.

Flood A, Schatzkin A. Colorectal cancer: does it matter if you eat your fruits and vegetables? J Natl Cancer Inst. 2000;92(21):1706-7.

Fotuhi M, Zandi PP, Hayden KM, et al. Better cognitive performance in elderly taking antioxidant vitamins E and C supplements in combination with nonsteroidal anti-inflammatory drugs: the Cache County Study. Alzheimers Dement. 2008;4(3):223-7.

Gomez JA, Molero X, Vaquero E, Alonso A, Salas A, Malagelada JR. Vitamin E attenuates biochemical and morphological features associated with the development of chronic pancreatitis. Am J Physiol Gastrointest Liver Physiol. 2004;287(1):G162-9.

Gray SL, Anderson ML, Crane PK, Breitner JC, McCormick W, Bowen JD, Teri L, Larson E. Antioxidant vitamin supplement use and risk of dementia or Alzheimer's disease in older adults. J Am Geriatr Soc. 2008 Feb;56(2):291-5.

Hamilton KL. Antioxidants and cardioprotection. Med Sci Sports Exerc. 2007 Sep;39(9):1544-53.

Heart Outcomes Prevention Evaluation Study Investigators. Vitamin E supplementation and cardiovascular events in high-risk patients. N Engl J Med. 2000;342:154-60.

Helzlsouer KJ, Huang HY, Alberg AJ, et al. Association between alpha-tocopherol, gamma-tocopherol, selenium and subsequent prostate cancer. J Natl Cancer Inst. 2000 Dec 20;92(24):2018-23.

Hernandez J, Syed S, Weiss G, Fernandes G, von Merveldt D, Troyer DA, Basler JW, Thompson IM. The modulation of prostate cancer risk with alpha-tocopherol: a pilot randomized, controlled trial. J Urol. 2005;174(2):519-22.

Jänne PA, Mayer RJ. Chemoprevention of colorectal cancer. N Engl J Med. 2000;342(26):1960-8.

Jenab M, Salvini S, van Gils CH, Brustad M, Shakya-Shrestha S, Buijsse B, et al. Dietary intakes of retinol, beta-carotene, vitamin D and vitamin E in the European Prospective Investigation into Cancer and Nutrition cohort. Eur J Clin Nutr. 2009 Nov;63 Suppl 4:S150-78.

Jialal I, Devaraj S. Scientific evidence to support vitamin E and heart disease health claim: research needs. J Nutr. 2005;135(2):348-53.

Joshi YB, Practico D. Vitamin E in aging, dementia, and Alzheimer's disease. Biofactors. 2012;38(2):90-7.

Klein EA, Thompson IM Jr, Tangen CM, et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2011;306(14):1549-56.

Kline K, Lawson KA, Yu W, Sanders BG. Vitamin E and cancer. Vitam Horm. 2007;76:435-61.

Krauss RM, Eckel RH, Howard B, Appel LJ, Daniels SR, Deckelbaum RJ, et al. AHA Scientific Statement: AHA Dietary guidelines Revision 2000: A statement for healthcare professionals from the nutrition committee of the American Heart Association. Circulation. 2000;102(18):2284-99.

Laight DW, Carrier MJ, Anggard EE. Antioxidants, diabetes and endothelial dysfunction. Cardiovasc Res. 2000;47:457-64.

Lippman SM, Klein EA, Goodman PJ, Lucia MS, et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA. 2009 Jan 7;301(1):39-51.

Loprinzi CL, Barton DL, Rhodes D. Management of hot flashes in breast-cancer survivors. Lancet. 2001;2:199-204.

Major JM, Yu K, Weinstein SJ, et al. Genetic variants reflecting higher vitamin e status in men are associated with reduced risk of prostate cancer. J Nutr. 2014;144(5):729-33.

Malafa MP, Neitzel LT. Vitamin E succinate promotes breast cancer tumor dormancy. J Surg Res. 2000 Sep;93(1):163-70.

Mangialasche F, Klvipelto P, et al. High plasma levels of vitamin E forms and reduced Alzheimer's disease risk in advanced age. J Alzheimers Dis. 2010:20(4):1029-37.

Mangialasche F, Solomon A, Kareholt I, et al. Serum levels of vitamin E forms and risk of cognitive impairment in a Finnish cohort of older adults. Exp Gerontol. 2013;48(12):1428-35.

Masaki KH, Losonczy KG, Izmirlian G. Association of vitamin E and C supplement use with cognitive function and dementia in elderly men. Neurology. 2000;54:1265-72.

McSorley PT, Bell PM, Young IS, Atkinson AB, Sheridan B, Fee JP, McCance DR. Endothelial function, insulin action and cardiovascular risk factors in healthy adult offspring of parents with Type 2 diabetes: effect of vitamin E in a randomized, double-blind, controlled clinical trial. Diabet Med. 2005 Jun;22(6):703-10.

Meydani M. Vitamin E modulation of cardiovascular disease. Ann N Y Acad Sci. 2004 Dec;1031:271-9.

Michels KB, Giovannucci E, Joshipura KJ, et al. Prospective study of fruit and vegetable consumption and incidence of colon and rectal cancers. J Natl Cancer Inst. 2000;92:1740-52.

Naziroglu M. Simsek M, Simsek H, Aydilek N, Ozcan Z, Atilgan R. The effects of hormone replacement therapy combined with vitamins C and E on antioxidant levels and lipid profiles in postmenopausal women with type 2 diabetes. Clin Chim Acta. 2004 Jun;344(1-2):63-71.

Nishida Y, Ito S, Ohtsuki S, Yamamoto N, et al. Depletion of vitamin E increases amyloid beta accumulation by decreasing its clearances from brain and blood in a mouse model of Alzheimer disease. J Biol Chem. 2009 Nov 27;284(48):33400-8.

Pace A, Giannarelli D, Galiè E, et al. Vitamin E neuroprotection for cisplatin neuropathy: a randomized, placebo-controlled trial. Neurology. 2010 Mar 2;74(9):762.

Peters U, Littman AJ, Kristal AR, Patterson RE, Potter JD, White E. Vitamin E and selenium supplementation and risk of prostate cancer in the Vitamins and lifestyle (VITAL) study cohort. Cancer Causes Control. 2007 Oct 18; [Epub ahead of print].

Pruthi S, Allison TG, Hensrud DD. Vitamin E supplementation in the prevention of coronary heart disease. Mayo Clin Proc. 2001;76:1131-6.

Roberts LJ 2nd, Oates JA, Linton MF, et al., The relationship between dose of vitamin E and suppression of oxidative stress in humans. Free Radic Biol Med. 2007 Nov 15;43(10):1388-93.

San Giovanni JP, Chew EY, Clemons TE, et al., The relationship of dietary carotenoid and vitamin A, E, and C intake with age-related macular degeneration in a case-control study: AREDS Report No. 22. Age-Related Eye Disease Study Research Group. Arch Ophthalmol. 2007 Sep;125(9):1225-32.

Sano M, Ernesto C, Thomas RG, et al. A controlled trial of selegiline, alpha-tocopherol, or both as treatment for Alzheimer's disease. N Engl J Med. 1997;336:1216-22.

Schatzkin A, Lanza E, Corle D, et al. Lack of effect of a low-fat, high-fiber diet on the recurrence of colorectal adenomas. N Engl J Med. 2000;342(16):1149-55.

Schürks M, Glynn RJ, Rist PM, Tzourio C, Kurth T. Effects of vitamin E on stroke subtypes: meta-analysis of randomised controlled trials. BMJ. 2010;341:c5702.

Sesso HD, Buring JE, Christen WG, et al. Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial. JAMA. 2008;300:2123-33.

Trottier G, Boström PJ, Lawrentschuk N, Fleshner NE. Nutraceuticals and prostate cancer prevention: a current review. Nat Rev Urol. 2009 Dec 8. [Epub ahead of print].

Wang L, Sesso HD, Glynn RJ, et al. Vitamin E and C supplementation and risk of cancer in men: posttrial follolw-up in the Physicians' Health Study II randomized trial. Am J Clin Nutr. 2014;100(3):915-23.

Weinberg PD. Analysis of the variable effect of dietary vitamin E supplements on experimental atherosclerosis. J Plant Physiol. 2005 Jul;162(7):823-33.

Yang CS, Suh N, Kong AN. Does vitamin E prevent or promote cancer? Cancer Prev Res. 2012;5(5):701-5.

Yochum LA, Folsom AR, Kushi LH. Intake of antioxidant vitamins and risk of death from stroke in postmenopausal women. Am J Clin Nutr. 2000;72:476-83.