Folate, a B vitamin, may protect against a form of childhood leukemia, reducing risk by up to 60%, said a report in The Lancet (Vol. 358, No. 9297: 1935-1940).

Acute lymphoblastic leukemia (ALL) is the most common cancer among children in developed countries. Treatment advances in recent years have led to cure rates higher than 75%, yet ALL still accounts for more than 25% of childhood cancer deaths.

Despite treatment advances, little is known about what causes ALL, much less how to prevent it.

With this in mind, Australian researchers set out to determine if some factors might be more common among children with this form of leukemia.

Judith Thompson, MMedSc, and colleagues from the Cancer Foundation of Western Australia surveyed the parents of 83 children with ALL and 166 children without it.

They were asked questions about possible risk factors, including family history, exposure to radiation, medication use, tobacco and alcohol use, and workplace exposures.

The authors found that the use of folate and iron during pregnancy was associated with a lower rate of ALL — about a 60% reduced risk. This was much weaker among mothers who took only iron. This led them to believe that the protective effect was mainly caused by folate.

When the pregnant women started taking folate and how long they took it did not seem to matter. Aside from having the parents born in Australia, no other factors seemed to be associated with reduced risk.

While the results of this study may point to a connection between folate and this type of cancer, there are still many questions to be answered before recommending adding folic acid (the form of this vitamin found in supplements) to the diet, the authors said.

"A deficiency in folate or iron has not been shown to cause ALL, nor have folate or iron supplements been shown to protect against the disease," the authors wrote.

They also point to the fact that while folate use to prevent birth defects has become more common in Western Australia in recent years, the incidence of ALL has not changed. However, neural tube defects have decreased in number.

Folate is a vitamin found naturally in many fruits and vegetables and is used to maintain DNA, the genetic blueprint in each of our body's cells.

Folic acid is often recommended for women of childbearing age. Studies have shown that it reduces the chance of neural tube defects, such as spina bifida, when taken during early pregnancy. Any woman planning a pregnancy should discuss folic acid with her doctor.

In theory, a deficiency of folate may result in damage to DNA that could lead to cancer. Increased folate levels have been associated with lower risks for certain cancers, especially colon cancer. Evidence for other forms of cancer is not as strong.

At this point, no studies have shown that folic acid supplements decrease cancer risk.

And, since 1998, all grain products (breads, cereals, pastas) in the US have been fortified with folic acid.

Eating five (or more) servings of fruits and vegetables, along with grain products each day, provides the recommended levels of folate, and many other nutrients important for good health.