Vitamin E Drug and Food Interactions
Safety Considerations when Taking Vitamin E Supplements
Vitamin E supplements, when taken in the recommended amounts, can be beneficial when, in fact, there is a need for them, but taking them in excess of those amounts or self-prescribing these supplements when not needed at all can be dangerous. You should only take vitamin E supplements if advised by your doctor to do so and exactly as prescribed. The following are some additional guidelines.
If you plan on taking vitamin E supplements, you need to know that they come not only in a wide range of dosages but also in many different forms. For example, you can buy vitamin E by itself, as part of an antioxidant “cocktail,” or as one ingredient in a multivitamin/mineral supplement. Doses range from 10 to 800 IU. Both natural and synthetic alpha/tocopherol and combined tocopherol and tocotrienol supplements are all available. Given this tremendous variety, it is easy to be confused and wind up getting a supplement with a higher dosage than necessary. Your doctor or nutritionist can advise you which, if any, of these supplements, is appropriate for you.
The results of several research studies indicate that alpha-tocopherol in its natural form has greater bioavailability than synthetic forms of vitamin E. The absorption rate of dietary alpha-tocopherol typically ranges between 20% and 70%, whereas absorption decreases to less than 10% with synthetic supplements.
The labels on vitamin E supplements express vitamin E in International Units (IUs), whereas the RDAs are expressed in mg. You can use the following conversion guidelines. If the supplement contains natural vitamin E, multiply the IU by 0.67. If the supplement contains a synthetic form of vitamin E, multiply the IU by .45.
If you are first starting to take vitamin E supplements, here are some possible side effects to watch out for, which might mean the treatment is not agreeing with you, Stop use and call your doctor immediately if you experience abdominal pain, diarrhea, nausea, flu-like symptoms, or blurred vision. Or call your doctor when convenient if you experience a headache, dizziness, tiredness, or breast enlargement.
Interaction with Other Substances and Medications
If you are taking or plan to take a vitamin E supplement, you need to be aware of the possible interactions with other substances and medications you are taking, including other vitamins and minerals For example, because vitamin E has blood thinning properties of its own, it may have an added effect when used together with a prescribed anticoagulant such as warfarin or heparin or even daily baby aspirin or large amounts of fish oil, gingko, or garlic.
On the other hand, vitamin E can produce the opposite effect with other substances and reduce their effectiveness. A good example of this is, high doses of vitamin E can interfere with the absorption and utilization of vitamin K. Also, supplements taken entirely in the form of alpha-tocopherol can reduce the blood levels of gamma and delta-tocopherols. Similarly, some substances such as chlorine, inorganic iron, mineral oil, polyunsaturated oils, and estrogen interfere with the absorption of vitamin E.
The following chart summarizes some of the important interactions between vitamin E and other substances. This is not intended to be a complete list, however. Before starting any vitamin E supplement regimen, you are strongly advised to review with your doctor all of the medications and supplements you are currently taking to make sure the combination is safe and see if any adjustments might be in order.
Medication or Substance Interactive Effect
Antacids Decreased the absorption of vitamin E.
Anticoagulants (e.g., Coumadin) May increases spontaneous or hidden bleeding.
Aspirin (long-term use) May reduces blood clotting and causes excessive bleeding
Beta-Carotene High intake of vitamin E inhibits beta-carotene absorption and metabolism.
Bile acid sequestrants Decreased the absorption of vitamin E.
For lowering cholesterol
(e.g., cholestyramine or colestipol)
Chemotherapy medications Reduced efficacy of these drugs.
Cyclosporine (immune suppressant Enhanced effects.
Given to prevent transplant rejection)
Estrogen Decreased absorption of vitamin E.
Griseofulvin (antifungal drug for Increased blood levels of griseofulvin.
Iron supplements (especially Decrease in the effectiveness of iron
in the inorganic form) supplements in those with iron deficiency anemia; decreased the effectiveness of vitamin E in healthy individuals. Iron supplements and vitamin E supplements should not be taken together.
Mineral oil Decreased the absorption of vitamin E.
Olestra Decreased absorption of vitamin E.
Selenium Increases the effectiveness of vitamin E.
Sucralfate (treatment for stomach Decreased absorption of vitamin E
Tobacco Decreased the absorption of vitamin E.
Vitamin A Vitamin E facilitates absorption, storage, and utilization of vitamin A. However, excessive doses of vitamin E cause depletion of vitamin A.
Vitamin K High intake of vitamin E inhibits vitamin K absorption and metabolism. Increased risk for bleeding due to interference with vitamin K blood clotting function.