People who regularly take vitamin E supplements over the years may have a decreased risk of developing the fatal neurological condition amyotrophic lateral sclerosis (ALS), a new study suggests.
ALS — also known as Lou Gehrig's disease — is an invariably fatal disease in which the nerve cells that control movement progressively degenerate, leading to paralysis and death from respiratory failure. It is diagnosed in about 5,000 Americans each year.
Up to 10 percent of ALS cases are an inherited form of the disease. In most cases, though, ALS occurs for no known reason.
Some research has suggested that people with higher intakes of vitamin E have a lower risk of ALS. Those findings do not prove that vitamin E is the reason, but lab research has found that the vitamin, which acts as a cell-protecting antioxidant, can delay the onset of symptoms in mice genetically altered to develop an ALS-like condition.
Since ALS is so rare, researchers need to study large groups of people to see what lifestyle factors might be related to the disease.
So for the new study, researchers at Harvard University combined the results of five large U.S. studies involving more than 1 million adults in all.
They found that there was a relationship between the length of vitamin E use and ALS.
People who, at the start of their study, had been using vitamin E supplements regularly for at least five years were about one-third less likely than non-users to develop ALS.
However, it's too soon to make any recommendations on vitamin E, Dr. Eilis J. O'Reilly and her Harvard colleagues report in the American Journal of Epidemiology.
For one, the findings do not prove that vitamin E, itself, provided the benefit. The researchers did try to account for other lifestyle factors, like people's weight, smoking habits, overall diet and exercise levels. And longer use of vitamin E supplements (from multivitamins or single supplements) was still linked to a lower ALS risk.
But there could still be other explanations for the finding. And promising findings on vitamin E have failed to pan out in the past.
Researchers once thought vitamin E supplements might prevent heart disease, based on studies showing lower rates among vitamin E users. But clinical trials — where people were randomly assigned to take vitamin E or a placebo — later showed no such benefit.
In addition, the current findings are based on small numbers. Of the 1 million-plus study participants, 805 were eventually diagnosed with ALS. And of those who had been using vitamin E for at least five years at the outset, just 18 developed ALS; there were 19 cases among people who had used the vitamin for fewer years.
Further studies, O'Reilly's team writes, are needed to see whether vitamin E does in fact affect ALS risk.
In general, experts recommend that adults get 15 milligrams, or 22 international units (IU), of vitamin E each day.
Food sources include wheat germ, nuts such as almonds and hazelnuts, vegetable oils such as sunflower and safflower oils, and some green vegetables, such as spinach and broccoli.
It's unlikely that people could get too much vitamin E from food. But high doses of vitamin E from supplements carry a risk of bleeding. Experts advise that adults consume no more than 2,500 IU of synthetic vitamin E per day.
Multivitamins usually contain 30 IU of vitamin E, while the typical dose in single supplements is 400 IU.