Vitamin E

Functions

Vitamin E is the name given to a group of eight fat-soluble chemical compounds derived from plants. The group consists of four tocopherol compounds and four tocotrienol compounds. Alpha-tocopherol is the most biologically active of the eight compounds and so vitamin E activity is usually defined in terms of 'alpha-tocopherol equivalents'.

The key role of vitamin E is as an antioxidant. Crucially it protects the polyunsaturated fats found in the lipid layer of cell membranes from oxidation by free radicals. Vitamin E also protects the fats in LDL cholesterol from oxidation during transportation around the body.

Vitamin E most likely works in combination with other antioxidants such as selenium and vitamin C to perform its role as an antioxidant. When a molecule of vitamin E quenches a free radical its structure is altered (it is now 'oxidised') such that it cannot perform any further antioxidant activities. Other vitamins such as vitamin C regenerate vitamin E (so it reverts to an unoxidised form) and then it regains its antioxidant ability. Clearly demonstrating the inter-related roles of vitamins and minerals in our bodies and therefore the necessity of maintaining a balanced diet and supply of these nutrients.

Role in Disease Prevention

Fighting Chronic Diseases

Epidemiological studies suggest that vitamin E intake reduces the risk of cardiovascular disease, diabetic complications, certain cancers and even cataracts. However, clinical trials of vitamin E supplementation in groups at high risk of these health conditions have produced mixed results and overall shown little benefit. Further research is required.

Food Sources

Natural sources of vitamin E are fats and oils, although it is also found in some vegetables, cereals, dairy foods and the fats of meat, poultry and fish. The major food sources of vitamin E are broccoli, dark green leafy vegetables, peas, avocado, kiwifruit, nuts and wholegrains. Vitamin E is also found in vegetable-derived oils such as wheat germ, sunflower, safflower, canola, olive, cottonseed, soybean and corn oils.

Typical Contributions from Food

Food	Total Vitamin E (mg alpha-tocopherol equivs)
Broccoli, boiled (1/2 cup)	0.08
Spinach, boiled (1/2 cup)	1.43
Peas, boiled (1/2 cup)	0.53
Avocado, flesh (1/2 avocado)	2.20
Kiwifruit, flesh (one)	1.70
Almonds, raw (five nuts)	1.44
Oats, rolled (1/2 cup)	0.72
Sunflower oil (1 tbsp)	6.77
Canola oil (1 tbsp)	3.06
Olive oil (1 tbsp)	0.70

Source: FoodWorks 2007.

Recommended Dietary Intake (RDI)

Following are the recommended dietary intake (RDI) levels for New Zealand and Australia.
 

Vitamin E RDIs – New Zealand and Australia

Life Stage	Age	Males (mg/day alpha-tocopherol equivs)	Females (mg/day alpha-tocopherol equivs)
Children	1-3 yr	5	5
	4-8 yr	6	6
	9-13 yr	9	8
	14-18 yr	10	8
Adults	19+ yr	10	7
Pregnancy	14-18 yr	-	8
	19+ yr	-	7
Breastfeeding	14-18 yr	-	12
	19+ yr	-	11

Suggested Dietary Target for Reducing Chronic Disease Risk

The New Zealand and Australian governments have set a suggested dietary target (SDT) for vitamin E intake of 19mg/day for men and 14mg/day for women. There is some evidence to suggest that vitamin E intake above the RDI level may reduce the risk of various chronic diseases, in the opinion of the NZ and Australian health authorities. Hence, this higher SDT target is provided for the information purposes of individuals and is based on current scientific evidence relating diet to chronic disease risk.

Deficiency

A deficiency of vitamin E is highly uncommon and as such no specific symptoms have been attributed to a deficiency of this nutrient. Typically vitamin E deficiency occurs as a result of genetic abnormalities, fat malabsorption issues and protein-energy malnutrition where-in the key symptom is peripheral neuropathy.

Toxicity

The highest level of average daily intake of vitamin E for adults (aged 19 years and over) that is believed to not cause any adverse health effects is 300mg/day. Adolescents and children's tolerance is considerably less than this.

References

Lister C. (2003). Antioxidants: a health revolution. Christchurch: New Zealand Institute for Crop and Food Research.

Ministry of Health. (2006). Nutrient reference values for Australia and New Zealand. Canberra: Commonwealth of Australia.

Last Updated: 9 October 2008

The material provided by Thinking Nutrition Ltd on this website is for information purposes only. It is not a substitute for appropriate health advice from a qualified medical practitioner.