Vitamin E

Vitamin E

Vitamin E is a fat-soluble vitamin that has eight chemical forms (4 tocopherols and 4 tocotrienols). The two most significant forms for humans are alpha and gamma tocopherols. They are major direct antioxidants, along with vitamin A, vitamin C and the carotenoid phytochemicals.

Biochemical roles in the body

Vitamin E ‘s direct antioxidant properties are due to its ability to donate a hydrogen atom (a proton plus electron) to free radical and reactive oxygen species formed when fat undergoes oxidation. It thus protects the DNA from mutagens. It also has anti-inflammatory and is important for a healthy immune system. Vitamin E has some enzymatic activities which help smooth muscle growth, has a role in eye and neurological functions, and inhibits platelet coagulation.

Recommended daily amounts and serum levels

The RDA of vitamin E is 15 mg/day with women needing slightly more. Lactating women need around 19mg/day.   Most of the vitamin E in foods is the gamma-tocopherol isoform, whereas most vitamin E supplementation studies used α-tocopherol. Normal blood ranges for α-tocopherol are 25-60 micromol/l and Gamma tocopherol are 2.0- 8.5 micromol/l.

Vitamin E deficiency

Severe vitamin E deficiency is rare and usually caused by malabsorption of fats due to bowel surgery, disease of the bowel (e.g. Crohn’s) or diseases of the pancreas (which produces the enzymes required to absorb fat from the gut). Severe deficiency can cause neuromuscular problems such as ataxia (loss of balance and poor movement), muscle and nerve damage, anaemia, impaired immunity, eye damage and infertility. Furthermore, moderate vitamin E deficiency over long periods of time may increase our susceptibility to mutagenic carcinogens.

Health benefits

There is no doubt that maintaining adequate vitamin E levels will have long-term benefits for health, particularly in regard to degenerative conditions. The relationship with cancer, however, is not so straight-forward. In laboratory studies, tocopherols have been shown to prevent less aggressive tumours changing to a more aggressive type (differentiation). An RCT conducted in France studying a daily capsule supplement of a combination of low dose antioxidants (ascorbic acid 120mg, vitamin E 30 mg, beta-carotene 6 mg, selenium 100 μg, and zinc 20 mg) found a reduction in cancer after 7.5 years in men but not women. Further analysis of dietary patterns of the male participants in the trial revealed that many were likely to have had pre-existing deficiencies in these vitamins, explaining the effectiveness of the capsule. In another interventional trial, four different combinations of daily mineral and vitamin supplements were administered to 29,584 adults in Linxian, China, at a time when its population was known to have widespread micronutrient deficiencies. The study found a reduced risk of oesophagal cancer after five years of supplementation for the group receiving supplementation with beta-carotene, vitamin E and selenium.

Concerns with vitamin E supplementation

There are considerable concerns about over-correcting serum vitamin E levels. The Alpha-Tocopherol, Beta-Carotene cancer prevention trial (ATBC) involved 29,133 male smokers taking vitamin E (alpha-tocopherol) and vitamin A (Beta-carotene) or a placebo. After several years, the treatment group had a statistically significant reduction in the incidence of prostate cancer, but the incidence of lung cancer, the main trial endpoint, was higher. The relationship between smokers, risk of prostate cancer and vitamin E was confirmed in the Cancer Prevention II (CPII) Nutrition Cohort study. As well as a detailed dietary history, this study also measured participants’ blood levels for vitamin E. It observed that blood vitamin E was indeed lower in smokers, and that there was a correlation between low blood vitamin E levels and higher incidence of prostate cancer. This correlation was particularly high with the isoform gamma-tocopherol, the main vitamin E found in health foods, as opposed to the alpha-tocopherol found in man-made supplements.

An Australian study analysing over a thousand individuals who had been treated for skin cancer outline how the risk of a further cancer was reduced if individuals ate foods with a high level of dietary vitamin E, but individuals who took supplements of vitamin E actually had a higher rate of recurrent skin cancers. Moreover, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) randomised 43,887 men to receive either selenium supplementation alone, vitamin E supplementation alone, a supplement containing both, or placebo and demonstrated a significantly increased risk of prostate cancer with vitamin E supplementation compared with the other three groups.

Conclusion

The published data suggests that vitamin E is an important anti-oxidant and a deficiency increases the risk of chronic diseases, including cancer. Levels are particularly low in smokers, who should take extra care to eat vitamin E-rich foods. Correcting a vitamin E deficiency with low dose supplements is likely to be beneficial, but higher dose supplements for people with adequate starting levels are harmful and will increase the cancer risk. It is best to concentrate on vitamin E-rich dietary sources, or better still, measure your serum levels and correct accordingly (measure your micronutrient levels).

Dietary sources of Vitamin E

Most vitamin E comes from oils within plants. Cold-pressed (extra-virgin) oils have significantly better preservation of the vitamin E, while fish oil capsules also contain vitamin E because it is found in fish and is also often added to prevent oxidation of the oil.

Pistachios (1 cup)     9 mg

Almonds (1 cup)       8 mg

Spinach (1 bunch)     7 mg

Hazelnuts (1 cup)     5 mg

Chard (1 cup)            3 mg

Sweet Potato (1 large tablespoon)  4.5 mg

Wheat germ (1 tablespoon)             4.5 mg

Sunflower seeds (2 tablespoons)   4.2 mg

Extra virgin olive oil (1 tablespoon)  2.9 mg

Avocado (1)     2.7 mg

Butternut squash (1 cup)  2mg

Sunflower, corn, safflower and standard olive oils (I tablespoon)  2mg

Trout (1 medium serving of fish)  2mg

Soya beans (1 cup)  1mg

References:

Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Institute of Medicine (US) Panel on Dietary Antioxidants and Related Compounds. Washington (DC): National Academies Press (US); 2000

Bjelakovic et al( 2012). Antioxidant supplements for prevention of mortality in healthy participants. The Cochrane database of systematic reviews (3): CD007176. PMID 22419320. DOI:10.1002/14651858.CD007176.pub2.

Haber D (2006). Health promotion and ageing: practical applications for health professionals (4th ed.). New York, NY: Springer Pub. p. 280. ISBN 978-0-8261-8463-4.

Meyer F et al. (2005) Antioxidant vitamin and mineral supplementation and prostate cancer prevention in the SU.VI.MAX trial. Int J Cancer 116: 182-186.

Blot WJ et al. (1993) Nutritional intervention trials in  China supplementation with specific vitamin/mineral combinations cancer incidence. J Natl Cancer Inst 85: 1483-1492.

Omenn GS et al. (1996) Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial. J Natl Cancer Inst 88: 1550-1559.

Klein EA et al. (2011) Vitamin E and the risk of prostate cancer the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 306: 1549-1556.

Albanes D et al. (1996) Alpha-tocopherol and beta-carotene supplements and lung cancer RISK in the alpha-tocopherol, beta-carotene cancer prevention study. J Natl Cancer Inst 88: 1560-1570.

Heinonen OP et al. (1998) Prostate cancer and supplementation with alpha-tocopherol and beta-carotene incidence and mortality in a controlled trial. J Natl Cancer Inst 90: 440-446.