Vitamin E – the food stabiliser and important antioxidant in your body (part 3).
As you know there are many forms of Vitamin E. In this part of the article, conversions factors between them and equations, which help you correctly calculate the active ingredient, are presented. Based on this knowledge we will look on intake limits and recommendations for Vitamin E supplementation.
Calculations and conversions for different forms of Vitamin E.
If you dont' know what is the International Unit, please read this article.
1 IU of Vitamin E is the biological equivalent of:
- about 0.667 mg of RRR-alpha-Tocopherol (a natural form of Vitamin E formerly named d-alpha-Tocopherol or sometimes ddd-alpha-Tocopherol),
- about 0.909 mg of an equal mix of the eight stereoisomers, which is a racemic mixture called all-rac-alpha-Tocopherol or dl-alpha-Tocopherol (or more precisely dl,dl,dl-alpha-Tocopherol),
- 1 mg of an equal mix of the eight stereoisomers, which is a racemic mixture called all-rac-alpha-Tocopheryl acetate or dl-alpha-Tocopheryl acetate (or more precisely dl,dl,dl-alpha-Tocopheryl acetate).
However, 1 IU of this racemic mixture is not now considered equivalent to 1 IU of natural RRR-alpha-Tocopherol, and the Institute of Medicine and the USDA now convert IU's of the racemic mixture to milligrams of equivalent RRR form using 1 IU of racemic mixture = 0.45 mg of RRR-alpha-Tocopherol.
Base on above to convert an amount of Vitamin E from mg to IU (and reverse) please use equations:
- 1 mg of alpha-Tocopherol is equivalent to 1.49 IU of the natural form of Vitamin E or 2.22 IU of the synthetic form of Vitamin E,
- 1 IU of the natural form of Vitamin E is equivalent to 0.67 mg of alpha-Tocopherol,
- 1 IU of the synthetic form of Vitamin E is equivalent to 0.45 mg of alpha-Tocopherol.
Intake limits and recommendations for Vitamin E.
To fully understand presented below values read Understand Nutritional Daily Values.
Before we will look on recommendations, it is good to remember that naturally sourced Vitamin E is called RRR-alpha-Tocopherol (and commonly it is labelled as d-alpha-Tocopherol). The synthetically produced form of Vitamin E is all-rac-alpha-Tocopherol (and commonly it is labelled as dl-alpha-Tocopherol).
There are set Recommended Daily Amounts (RDA) for Vitamin E. For example, RDA for a 25-year old male for Vitamin E is 15 mg/day. Because Vitamin E can act as an anticoagulant and may increase the risk of bleeding problems (hemorrhagic effects), many agencies (like The Food and Nutrition Board ) have set an upper tolerable intake level (UL) for Vitamin E at 1000 mg (1500 IU) per day. For details please review the table below.
We have to remember that, for composing foods or supplements with Vitamin E, as well as, for labelling them, the U.S. Food and Drug Administration (FDA) mandates that older conversion factors can be used (published by the Food and Nutrition Board in 1968, where 1 IU = 0.67 mg for d-alpha-Tocopherol = 0.90 mg for dl-alpha-Tocopherol). Under FDA's new labelling regulations for foods and dietary supplements that take effect by July 26, 2018 (for companies with annual sales of $10 million or more) or July 26, 2019 (for smaller companies), Vitamin E will be listed only in mg and not IUs.
(Food and Nutrition Board. Recommended Dietary Allowances, 7th ed. Washington, DC: National Academy of Sciences; 1968; Food and Drug Administration. Food labelling: Revision of the Nutrition and Supplement Facts labels. Federal Register 2016;81:33741-999)
The RDA for Vitamin E was last revised by the Food and Nutrition Board of the US Institute of Medicine in 2000. Current values are presented below.
The European Food Safety Authority (EFSA) set dietary reference values (DRVs) for Vitamin E as:
- 13 mg/day for men
- 11 mg/day for women
- 9 mg/day for boys and girls aged 3 to < 10 years
- 13 mg/day for boys and 11 mg for girls aged 10 to < 18 years
As you can see, recommendations in various regions are slightly different. For an adult, the EU RDA is about 12 mg (18 IU), while the US RDA is 15mg (22.5 IU). However, in general, we can say “the more polyunsaturated fatty acids you eat, the more Vitamin E you need as an antioxidant”.
Global, average intake of Vitamin E is around 11 mg per day, and about 90% of the population obtaining less than the recommended daily amount. For that reason, supplementation seems to be needed. The tolerable upper intake level at which no adverse effects are observed during long-term use supplements is 540mg Vitamin E/day (around 800 IU/day). However, in the EU a safety factor, established as the Upper Safe Level, is 300 mg/day (450 IU/day) from supplements. In the US upper safe level for Vitamin E depends on the source. For supplements made from natural forms of Vitamin E the Upper Intake Level for adults is suggested as 1000 mg/day (1500 IU/day), but for supplements containing synthetic Vitamin E is lower and equals 737 mg/day (1100 IU/day).
In different countries are local recommendations. For example, in India, the recommended dietary allowance of Vitamin E is approximately 8-10 mg/day (set by Indian National Institute of Nutrition). The best Vitamin E sources on Indian market are: wheat germ oil, sunflower seeds and almonds, as well as, cooking oils (most of them are fortified with Vitamin E). More about sources of Vitamin E and its bioavailability you can find in the next part of this article.
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