Dosing and Safety
How is vitamin E measured? We have all heard of international units (IU) and they were meant to be the vitamin E currency. Unfortunately, the criteria were created when alpha-tocopherol was thought to be the only compound in vitamin E. The IU was based on alpha-tocopherol acetate.
For your reference:
- 1 mg alpha-tocopherol acetate = 1.0 IU alpha-tocopherol acetate, BUT
- 1 mg alpha-tocopherol = 1.49 IU alpha tocopherol
IU's do not refer to the other seven compounds.
Thus, they must be measured in milligrams. To further confuse you, the Food and Nutrition Board of the National Research Council scrapped the IU and replaced it with the alpha-tocopherol equivalent (alpha-TE) in order to account for all 8 members of the vitamin E family - but only in foods NOT in supplements. One alpha-TE is one milligram of natural d-alpha-tocopherol. However, the IU is still the industry standard in the United States and many other countries and unfortunately, the alpha-TE on the label does not tell us much more than the IU.
IUs do not tell us whether:
- The product has tocopherols other than alpha or tocotrienols.
- The alpha-tocopherol is natural or synthetic.
- The alpha-tocopherol is esterified.
What is the RDI? The National Academy of Science's Recommended Daily Intake (RDI) for vitamin E is 15 milligrams. This is equivalent to 22 International Units (IU) of natural alpha-tocopherol or 33 IUs of the synthetic form. Of course, if you are reading this webpage you understand that the RDI is a measure of vitamin E used to prevent deficiency and NOT the amount that is necessary to prevent disease and promote wellness. The RDA (Recommended Daily Allowance) is still used on food labels and is 30 IU of alpha- tocopherol.
Where is vitamin E found? Vitamin E is found in oils, grains, nuts and green leafy vegetables. Corn and soybean oil have proportionally more gamma-tocopherol than other oils. You can get 400 IU from food instead of supplements. That depends if you can eat 1000 almonds (658g of fat) or 120 cups of broccoli.
How safe is vitamin E? Vitamin E is very safe. But it is important that you talk to your physician before starting any new supplements, especially if you are taking other medications. We recommend specifically that you speak with a physician if you have problems with blood clotting or you are taking blood thinners.
Scientists use a graph to show the safety of nutrients. The conclusions from many studies are represented in the graph below. The horizontal axis shows the dose of alpha-tocopherol in international (IU). The perpendicular axis shows the relative health risk. When intake of alpha-tocopherol is below the RDI the health risk secondary to deficiency is dramatically increased. As intake increases and approaches the RDI the relative risk to health decreases and remains low all the way up to 1200 IU. The yellow zone of caution starts at 1200 IU and the red zone of health risk starts at 3200 IU.
The safe Upper Intake Level (UL) for vitamin E has been set at 1000 IU. A landmark study of Alzheimer's and vitamin E used 2000 IU of vitamin E for two years without significant complications as compared to placebo. Another study used doses at 3200 IU/day - so even at higher doses vitamin E has been found to be relatively safe.
