Breast cancer is the most common form of cancer in women. Hundreds of thousands of new cases are identified worldwide every year.

Now, one of the largest cancer prevention studies of its kind has reported some sobering findings. Just one alcoholic drink a day can increase the risk of developing breast cancer. But, the researchers also found there are things people can do to reduce their risk.

The American Institute for Cancer Research did the study. It examined 119 past studies involving 12 million women. 260,000 of them had breast cancer.

Anne McTiernan was the lead writer of the report. McTiernan is with the Fred Hutchinson Cancer Research Center in Seattle, Washington.

She said the research showed a connection between drinking alcohol and increased risk of breast cancer in 10 studies involving 4,000 women. The women were of childbearing age and had developed breast cancer.

The study found that the women who drank about 10 grams of alcohol a day had a five percent increased risk of breast cancer.

Although five percent seems like a small amount, the study's chance of mistake was very low, said McTiernan.

Another group of studies involved 35,000 women who were post-menopausal and had developed breast cancer.

"We found that there was a nine percent increased risk of drinking that same amount of alcohol, an average of 10 grams a day of alcohol. Again, a small glass of wine, eight ounce(s) of beer, one ounce of hard liquor."

McTiernan said the World Health Organization considers alcohol to be a carcinogen – a substance that can cause cancer. It contains a liquid called acetaldehyde, which damages DNA.

Investigators also found ways to lower risk. They say forceful exercise, such as running or fast bicycling, decreased the risk of breast cancer. Young women who were the most physically active had about a 17 percent decrease. A 10 percent decrease was found for post-menopausal women who took part in similar exercise.

Moderate activity, such as walking and gardening, was found to reduce the risk of breast cancer by 13 percent in the most active women compared to the least active.

There was also evidence that eating a non-starchy, plant-based diet lowers the risk. However, that does not mean people must eat only vegetables, McTiernan said.

"It just means eating a lot of fresh vegetables and fruit: making sure most of the vegetables are non-starchy, not potatoes; eating dairy products because they are high in calcium and they have some benefit on their own."

McTiernan said eating a diet with lots of fruits and vegetables can help women keep their weight down. That is important, since being overweight can increase an older woman's breast cancer risk.

The Institute says one in three breast cancer cases in the U.S. could be prevented if women cut alcohol from their diets, stayed physically active and kept a healthy weight.

The American Institute for Cancer Research is part of the World Cancer Research Fund, which collects and studies information from around the world on cancer prevention.

I'm Alice Bryant.

VOA's Jessica Berman reported this story. Alice Bryant adapted it for Learning English. Caty Weaver was the editor.

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sobering - adj. making you feel serious and thoughtful

childbearing - adj. a word describing the process of giving birth to children

post-menopausal - adj. having gone through the time in a woman's life when blood stops flowing from her body each month

DNA - n. a substance that carries genetic information in the cells of plants and animals — often used before another noun

gardening - n. taking care of plants in an area of ground where they are grown

starchy - adj. a substance that is found in certain foods, such as bread, rice and potatoes

diet - n. the food that a person or animal usually eats

benefit - n. a good or helpful result or effect