Vitamin E shows promise in diabetes prevention

Try at least minimal doses for better outcomes

A growing body of evidence points to high doses of vitamin E as a way of addressing diabetes prevention and the prevention of comorbidities for patients already diagnosed with diabetes.

Harvard researchers are assessing research that suggests that high doses of vitamin E — naturally found in wheat germ, vegetable oils, margarine, whole grain breads, nuts, and peanut butter — may help prevent the decline of insulin resistance to full-blown Type 2 diabetes and may protect against vascular complications.

Vitamin E’s antioxidant (AO) capabilities have been well-documented in inhibiting the formation of free radicals — potentially damaging by-products of the body’s metabolism and of environmental factors such as air pollution and smoke.

Now Harvard researcher George King, MD, research director of the Joslin Diabetes Center in Boston, says there is a strong indication that very high doses of vitamin E — up to 2,000 IU daily — appear to arrest the effects of high glucose.

"For some reason that isn’t clear yet, vitamin E in high doses not only is an antioxidant, it also inhibits the production of the protein kinase C (PKC) enzyme. When this is done, you reverse, stop, or prevent many of the blood vessel complications we find in diabetes," says King.

King has led research resulting in several papers over the past three years showing that vitamin E normalizes PKC activation induced by hyperglycemia in vascular tissues.

King’s previous research has shown the effectiveness of vitamin E in preventing diabetic retinopathy and nephropathy.

"We need larger and longer trials to be sure that high doses of vitamin E given over a prolonged period of time will not be harmful," says King. "We know there are no harmful effects associated with low doses of vitamin E — in the range of 200 to 400 IU — taken over a long period of time, and our data show no adverse effects from taking 1,200-2,000 IU daily for a year. Beyond that, we simply still need to do the research," he says.

Yet King’s data also show that low doses have little or no effect on prevention of the early stages of diabetes, before complications develop.

For clinicians, King says there is certainly no harm — and there may be some help — in taking vitamin E in doses of 400-800 IU daily, particularly for patients with diabetes.

King’s recommendation for medium-range vitamin E supplementation is seconded by antioxidant researcher Roger McDonald, PhD, professor of nutrition at the University of California at Davis.

However, McDonald says he thinks the mechanism at work in preventing diabetic comorbidities is probably more complex than simply one of adding vitamin E.

"I have never seen anything in a single nutrient that turns out to have a long-range effect. It usually is a combination of factors. I would suggest in this case that beta-carotene and vitamin C also may play a role," says McDonald.

Key Points

  • Vitamin E works as an antioxidant, preventing disease-causing oxidative damage.
  • In patients with diabetes, vitamin E also appears to have an independent effect in reducing PKC enzyme activity and reducing vascular complications of the disease.
  • Recent research also suggests that high doses of vitamin E may delay or prevent diabetic retinopathy and nephropathy.