NEW YORK: US researchers say that lowering cholesterol levels with statins, a class of drugs, might increase the risk of cancer.

The researchers who studied 40,000 people, however, could not say if this was a side effect of the drugs or due to the low cholesterol.

Cholesterol is a waxy, fat-like substance that occurs naturally in all parts of the body. Our body needs some cholesterol to work properly. But if the substance increases in blood, it can stick to the walls of arteries. This is called plaque, which can narrow arteries or even block them.

There are two types of cholesterols - High-Density Lipoprotein (HDL) and Low-Density Lipoprotein (LDL). HDL cholesterol is known as good cholesterol, because high levels of HDL seem to protect against heart attack. High levels of LDL cholesterol or bad cholesterol in the blood can, however, increase the risk of heart disease.

Statins are a class of drugs that help lower cholesterol levels in the blood.

Researchers looked at summary data from 13 trials of people taking statins - a total of 41,173 patients. They found that groups with low cholesterol levels had one more cancer case per 1,000 people than those with higher levels, reported the online edition of BBC News.

The researchers at the Tufts University School of Medicine in Boston examined the relationship between low, medium and high doses of statins and rates of newly diagnosed cancer.

Higher rates of the disease were observed in the group with the lower levels.

The authors noted their findings were particularly important at a time when more and more trials show significant reductions in cholesterol levels can greatly benefit cardiovascular health.

However, writing in the Journal of the American College of Cardiology, the researchers said their findings do not change the message that the benefits of taking statins greatly outweigh any potential risks.