Drinking milk may help lower your risk of colon cancer. An analysis of 10 large studies found that people who drank more than 1 glass (8 ounces) of milk each day were 15% less likely to develop the disease than people who drank less than 2 glasses each week.

A group led by researchers from Harvard Medical School and Brigham and Women's Hospital in Boston published their findings in the Journal of the National Cancer Institute (Vol. 96, No. 13: 1015-1022).

"While researchers and physicians do not yet know what causes colorectal cancer, the results of this study have brought us even closer to understanding how to reduce the risk of this disease," lead researcher Eunyoung Cho, ScD, said in a statement.

Colorectal cancer is the third most common cancer among both men and women in the United States (excluding skin cancers). More than 146,000 people will be diagnosed with this disease in 2004, and more than 56,000 people are expected to die from it.

Doctors know that some food choices -- like eating a diet high in animal fat -- can increase a person's risk of developing this disease. But it's less clear whether specific foods or nutrients can also protect against colon cancer.

Many studies have examined the relationship between calcium and colon cancer risk, and some have found a protective effect. By looking at data from 10 large studies, the new research provides stronger evidence of that effect.

The studies contained information about both dietary calcium -- from dairy foods like milk, cheese and yogurt -- as well as total calcium -- from food and from supplements.

Calcium intake overall had a significant effect on colon cancer risk. People who got the highest amounts of total calcium -- 1,100 milligrams a day or more -- reduced their risk by about 21% compared to people who got only 500 milligrams of calcium a day.

When the researchers examined the effects of calcium from food alone, only milk had a significant effect on colon cancer risk. However, milk was the most common dairy product consumed; fewer people ate yogurt or cheese, so if those foods had an effect it may not have been apparent in the analysis.

The calcium in milk may not be the only nutrient at work, though. Milk also contains vitamin D, which may also have a protective effect. Or the two nutrients may work together to provide protection. It is difficult for researchers to tease out the effects of individual nutrients, especially when found in the same foods.

So should you start drinking more milk or taking calcium supplements?

The American Cancer Society doesn't have specific recommendations about calcium, said Marji McCullough, ScD, RD, a nutritional epidemiologist with ACS, because there is some evidence that too much calcium (more than 1,500 or 2,000 milligrams per day) may increase the risk of prostate cancer.

"Currently, nutritional advice has focused on eating plenty of fruit and vegetables, limiting red and processed meats, avoiding obesity, and getting regular physical activity," she said. "Nevertheless, following national recommendations for milk (ideally low-fat) and calcium intake appears prudent."

Current US government guidelines recommend 2 or 3 servings of milk, yogurt or cheese every day for most people. According to the Institute of Medicine, people over age 18 should get 1,000 milligrams of calcium each day; after age 50, most people should get 1,200 milligrams a day.