Vitamin E

By Dr. Carol Yu

Introduction and overview

One of the fat-soluble vitamins, vitamin E is dissolvable in fat, and is typically found in a wide range of foods. Vitamin E is well known for its anti-oxidant properties [1], meaning that it can protect cells in the body against damaging substances called free radicals. These free radicals – as a result of factors including aging – can cause harm to our cells, tissues, and organs. Therefore, vitamin E is believed to be beneficial for us by slowing down these damaging processes. Our body needs it for red blood cell formation, proper functioning of our immune system, and for cells to interact with each other to carry out proper functions.

Structure of vitamin E

The chemical formula of vitamin E is C29H50O2 containing 29 carbons, 50 hydrogens, and 2 oxygens.

Dietary sources of vitamin E

Vitamin E is naturally found in our foods including fruits, vegetables, nuts, seeds, oils, meat, eggs, and poultry. Any products that are made from these, such as margarine, canola, corn, or other vegetable oils, would also contain vitamin E [2, 3]. Vitamin E is added in some other foods and can also be found as a dietary supplement.

Functions of vitamin E

Vitamin E has many functions, but it is mainly recognized by antioxidant effects [1], suggesting that it has improving effects in chronic disease [4] which will be described in greater detail later. Also, vitamin e helps protect red blood cells [5] and prevent destruction of vitamins A and C.

Recommended intake

The recommended dietary intake for vitamin E depends on the individual based on various factors including age, gender, health status, pregnancy, and breast-feeding. Based on the Food and Nutrition Board at the Institute of Medicine, recommended intakes for individuals for vitamin E is:

Age	Male	Female	Pregnancy	Breast-feeding
0-6 months	4 mg	4 mg
7-12 months	5 mg	5 mg
1-3 years	6 mg	6 mg
4-8 years	7 mg	7 mg
9-13 years	11 mg	11 mg
14+ years	15 mg	15 mg	15 mg	19 mg

Information from the Food and Nutrition Board at the Institute of Medicine of the National Academies.

Individuals at risk for vitamin E deficiency

Deficiency for vitamin E is rare in human beings but can occur in people with certain genetic disorders [6]. Because vitamin E is soluble in fat, people with troubles digesting/absorbing fat or with reduced fat could end up with vitamin E deficiency. Supplementation of vitamin E is an effective therapy against vitamin E deficiency. Diagnosis and treatment should be managed by a medical professional.

Deficiency of vitamin E

In human, severe vitamin E can lead to neuromuscular abnormalities [7]. In newborns, vitamin e deficiency can result in very low birth weight. These babies may benefit from vitamin E supplementation but may risk infections [8]. Deficiency of vitamin E due to poor fat absorption may suffer from nerve damages, lack of voluntary coordinated movements, muscle abnormalities and weakness, problems in the retina and immune response [9].

Toxicity

It is recommended that the intake of antioxidants such as vitamin E comes from a well-balanced diet that is high in fruits, vegetables, and whole grains, instead of supplements of vitamin E. In fact, so far, there is no report showing adverse effects from vitamin E consumption from food. However, with supplements, there is a set upper limit of tolerable intake of vitamin E equivalent to 1000 mg per day, according to the Institute of Medicine. Shown below is an adapted table for tolerable vitamin E upper intake levels.

Age	Male	Female	Pregnancy	Breast-feeding
1-3 years	200 mg	200 mg
4-8 years	300 mg	300 mg
9-13 years	600 mg	600 mg
14-18 years	800 mg	800 mg	800 mg	800 mg
19+ years	1000 mg	1000 mg	1000 mg	1000 mg

Recently, a large clinical trial showed that about 250 mg of vitamin E supplement taken per day can even increase the risk of prostate cancer in adult men [10].

Vitamin E and health

Cancer treatment: Due to its antioxidant activities, many believe that vitamin E can counteract the effects of free radicals that could contribute to cancer development when left unchecked [11]. However, there are also clinical studies showing no beneficial effects on cancer outcomes resulting from vitamin E intake [12, 13] and may even increase risk of prostate cancer in adult men [10] as mentioned above. In post-menopausal women, vitamin E intake also did not result in any benefits from vitamin E intake [14]. All in all, there is insufficient data to support a beneficial role of vitamin E intake on combating cancer.

Diabetes treatment: Free radicals play a major role in the development of diabetes and because of this, vitamin E is believed to prevent type 1 or 2 diabetes, and can help with blood sugar control, clotting problems and clogged arteries in diabetic patients [15].

Cardiovascular health: Because of its antioxidant effects, some studies have shown that long-term vitamin E supplement intake can improve vascular health [16, 17]. However, there are also many clinical studies using rigorous scientific evaluation that found no benefits with vitamin E intake on risk of development coronary artery disease [18]. Therefore, better understanding of the science behind vitamin E and cardiovascular health is still needed.

High-cholesterol treatment: Vitamin E was proposed to inhibit the oxidation of low-density lipoprotein (LDL) cholesterol [19], which is a major player in the development of atherosclerosis.

Skin health: Vitamin E can help absorb the energy from ultraviolet (UV) light, therefore it is believed that vitamin E can help prevent sun-induced damages to the skin. It can also act as an anti-inflammatory agent in the skin [20]. Vitamin E can be applied on the skin topically.

Brain disease treatment: There is evidence suggesting that free radicals contribute to brain disease including Alzheimer’s disease, and a clinical trial conducted in patients with Alzheimer’s disease showed that vitamin E could slow down functional deterioration [21]. Another study showed that in a group of elderly (age 65 – 102), vitamin E intake from foods and supplements was associated with less cognitive decline [22]. Because the brain has high oxygen demand, it is highly prone to damages from free radicals or oxidative stress, which results from energy consumption, and may explain the benefits from vitamin E intake. Of course, there are also studies showing no benefits on cognitive function from vitamin E intake in patients with Alzheimer disease [23] and in healthy older women [24]. Altogether, while some research supports the use of vitamin E supplement for improving or maintaining cognitive performance, other reports suggest no benefits from vitamin E. More research is needed to clarify the role of vitamin E in cognitive function.

Drug interactions

Drug	Interaction with vitamin E
Anti-depressant medications	Vitamin E decreases body absorption of some antidepressant medications
Antipsychotic medications	Vitamin E decreases body absorption of some antidepressant medications
Aspirin	Combined intake of aspirin and vitamin E may benefit patients at risk for stroke
AZT (HIV/AIDS drug)	Vitamin E could decrease side effects from AZT
Beta-blockers	Vitamin E decreases body absorption of some classes of beta-blockers
Cholesterol-lowering medications	These drugs can lower absorption of vitamin E
Cyclosporine	May reduce effectiveness of both vitamin E and cyclosporine, an anti-cancer drug, when taken together
Mebendazole	May reduce effectiveness of mebendazole when taken with vitamins A, C, E, and selenium
Tamoxifen	Vitamin E may enhance anti-cancer effects of tamoxifen, an anti-breast cancer drug
Warfarin	May increase risks for abnormal bleeding
Weight loss products	Olistat, a weight loss drug, or other fat-reducing drugs, could decrease absorption of vitamin E

REFERENCE

1. Singh, U., S. Devaraj, and I. Jialal, Vitamin E, oxidative stress, and inflammation. Annu Rev Nutr, 2005. 25: p. 151-74.

2. Dietrich, M., et al., Does gamma-tocopherol play a role in the primary prevention of heart disease and cancer? A review. J Am Coll Nutr, 2006. 25(4): p. 292-9.

3. Munteanu, A., J.M. Zingg, and A. Azzi, Anti-atherosclerotic effects of vitamin E–myth or reality? J Cell Mol Med, 2004. 8(1): p. 59-76.

4. Shiva Shankar Reddy, C.S., et al., In vitro models of oxidative stress in rat erythrocytes: effect of antioxidant supplements. Toxicol In Vitro, 2007. 21(8): p. 1355-64.

5. Iwasa, K., et al., Retinitis pigmentosa and macular degeneration in a patient with ataxia with isolated vitamin E deficiency with a novel c.717 del C mutation in the TTPA gene. J Neurol Sci, 2014. 345(1-2): p. 228-30.

6. Sokol, R.J., et al., Isolated vitamin E deficiency in the absence of fat malabsorption–familial and sporadic cases: characterization and investigation of causes. J Lab Clin Med, 1988. 111(5): p. 548-59.

7. Brion, L.P., E.F. Bell, and T.S. Raghuveer, Vitamin E supplementation for prevention of morbidity and mortality in preterm infants. Cochrane Database Syst Rev, 2003(4): p. CD003665.

8. Kowdley, K.V., et al., Vitamin E deficiency and impaired cellular immunity related to intestinal fat malabsorption. Gastroenterology, 1992. 102(6): p. 2139-42.

9. Klein, E.A., et al., Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA, 2011. 306(14): p. 1549-56.

10. Iqubal, M.A., et al., Role of vitamin e in prevention of oral cancer:-a review. J Clin Diagn Res, 2014. 8(10): p. ZE05-7.

11. Kirsh, V.A., et al., Supplemental and dietary vitamin E, beta-carotene, and vitamin C intakes and prostate cancer risk. J Natl Cancer Inst, 2006. 98(4): p. 245-54.

12. Lee, I.M., et al., Vitamin E in the primary prevention of cardiovascular disease and cancer: the Women’s Health Study: a randomized controlled trial. JAMA, 2005. 294(1): p. 56-65.

13. Graham, S., et al., Diet in the epidemiology of postmenopausal breast cancer in the New York State Cohort. Am J Epidemiol, 1992. 136(11): p. 1327-37.

14. Xu, Y.J., et al., Prevention of diabetes-induced cardiovascular complications upon treatment with antioxidants. Heart Fail Rev, 2014. 19(1): p. 113-21.

15. Montero, D., et al., Effect of antioxidant vitamin supplementation on endothelial function in type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials. Obes Rev, 2014. 15(2): p. 107-16.

16.Joris, P.J. and R.P. Mensink, Effects of supplementation with the fat-soluble vitamins E and D on fasting flow-mediated vasodilation in adults: a meta-analysis of randomized controlled trials. Nutrients, 2015. 7(3): p. 1728-43.

17. Tinkel, J., H. Hassanain, and S.J. Khouri, Cardiovascular antioxidant therapy: a review of supplements, pharmacotherapies, and mechanisms. Cardiol Rev, 2012. 20(2): p. 77-83.

18. Wallert, M., et al., Regulatory metabolites of vitamin E and their putative relevance for atherogenesis. Redox Biol, 2014. 2: p. 495-503.

19. Godic, A., et al., The role of antioxidants in skin cancer prevention and treatment. Oxid Med Cell Longev, 2014. 2014: p. 860479.

20. Sano, M., et al., A controlled trial of selegiline, alpha-tocopherol, or both as treatment for Alzheimer’s disease. The Alzheimer’s Disease Cooperative Study. N Engl J Med, 1997. 336(17): p. 1216-22.

21. Morris, M.C., et al., Vitamin E and cognitive decline in older persons. Arch Neurol, 2002. 59(7): p. 1125-32.

22. Petersen, R.C., et al., Vitamin E and donepezil for the treatment of mild cognitive impairment. N Engl J Med, 2005. 352(23): p. 2379-88.
23. Kang, J.H., et al., A randomized trial of vitamin E supplementation and cognitive function in women. Arch Intern Med, 2006. 166(22): p. 2462-8.