 -- Drinking as few as one alcoholic beverage a day can increase your breast cancer risk, according to a new report released today by the American Institute for Cancer Research and the World Cancer Research Fund.

The good news is that the report also revealed a way to decrease the risk of breast cancer: vigorous exercise.

The study examined data on 12 million women and 260,000 cases of breast cancer from 119 studies to understand how certain lifestyle factors can affect breast cancer risk.

"With this comprehensive and up-to-date report the evidence is clear: Having a physically active lifestyle, maintaining a healthy weight throughout life and limiting alcohol -- these are all steps women can take to lower their risk," Anne McTiernan, MD, PhD, a lead author of the report, said in a statement.

Drinking one small glass of wine or beer a day can increase your pre-menopausal breast cancer risk by five percent and your post-menopausal breast cancer risk by 9 percent, according to the report. The report characterized a small glass of an alcoholic beverage as containing around 10 grams of alcohol, but noted that a standard drink contains 14 grams of alcohol.

The most active pre-menopausal women had a 17 percent lower risk of developing breast cancer, and very active post-menopausal women had a 10 percent lower risk of developing breast cancer, according to the report's findings on vigorous exercise. The report said that moderate activity was linked to a 13 percent lower risk of breast cancer in comparison to the least active women it looked at.

The report also found that being overweight or obese can increase your risk of post-menopausal breast cancer. Additionally, mothers who breastfeed are at a lower risk for breast cancer than mothers who do not.

Alice Bender, MS, RDN, the AICR's Head of Nutrition Programs, added in a statement that the report reveals that there are steps that all women can take to lower their risk of breast cancer.

"Wherever you are with physical activity, try to nudge it up a bit, either a little longer or a little harder," Bender said. "And if you drink alcohol, stick to a single drink or less."

"There are no guarantees when it comes to cancer," she added. "But it's empowering to know you can do something to lower your risk."