HONG KONG, Oct 13 (Reuters) - Folic acid, found in leafy vegetables, can cut drastically arsenic levels in the blood of people who have suffered long-term exposure to the poison in groundwater, a new study in Bangladesh has found.

Arsenic is a toxin naturally present in some soils and water. Chronic arsenic poisoning occurs after long-term exposure to such tainted drinking-water and it has been linked to skin, liver and bladder cancers, skin lesions and cardiovascular disease.

Chronic arsenic exposure affects 100 million people worldwide. The problem is especially severe in Bangladesh, where millions of shallow tubewells were installed from the 1970s to provide drinking water that was considered safe until 1993, when it was found to be contaminated with arsenic.

In a study funded by the National Institute of Environmental Health Sciences (NIEHS) at the U.S. National Institutes of Health (NIH), researchers found consuming 400 micrograms a day of folic acid reduced total blood arsenic levels in a Bangladeshi population by 14 percent.

The study was published in the October issue of the American Journal of Clinical Nutrition.

Folate is a B vitamin found in leafy vegetables, citrus fruits, beans and whole grains. Folic acid can also be taken as a vitamin supplement. In the United States, it is added to flour and other fortified foods.

Folate deficiency, however, is very common in Bangladesh.

"Folic acid supplementation enhanced the detoxification of arsenic to a form that is more readily excreted in urine," said Mary Gamble of Columbia University and the study's lead author.

"The results of this study suggest that a simple, low-cost nutritional intervention may help to prevent some of the long-term health consequences associated with arsenic exposure for the many populations at risk."

Arsenic levels in drinking water in some parts of Bangladesh reach as high as 100 times the limit of 10 micrograms per litre set by the World Health Organization.

In the study, 200 folate-deficient participants received either a daily tablet of 400 micrograms per day of folic acid or a placebo for twelve weeks and the researchers collected blood and urine samples at the beginning and end of the study.

Additional studies were needed to determine the optimal dose and duration of treatment, the researchers said.

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