The most common side effect from high doses is gastrointestinal with nausea, flatulence and diarrhea. Supplementation can exacerbate hypertension. Vitamin E may reduce insulin requirements and the insulin dosage in diabetics may need to be readjusted. Vitamin E succinate may be more effective in preventing free radical damage than alpha tocopherol. Vitamin E and selenium have similar mechanisms of action and a clinical deficiency of one can be treated with either nutrient.
Zinc deficiency can aggravate the effects of vitamin E deficiency.
Intake of a large dose of vitamin E may reduce intestinal absorption of vitamin K and antagonize the effect of vitamin K on coagulation at the level of prothrombin formation. Supplementation may increase grand mal seizures in epileptics, possibly related to a reduction in blood manganese levels. In epileptics, manganese supplementation should be started before the use of zinc. Supplementation is best taken separate from meals as eggs, milk, cereal and other foods will decrease its bioavailability. Zinc picolinate is significantly better absorbed than zinc citrate with decreasing absorption of gluconate, orotate and sulfate in that order.