Epidemiologists attributed 2 percent of European and North American breast cancer cases to light drinking and 50,000 instances of breast cancer throughout the world to heavy drinking, according to the study.
One alcoholic drink raised the risk of breast cancer by about 5 percent, and three or more drinks per day increased the risk by almost 50 percent over women who abstained from drinking.
Alcohol consumption is causally related with breast cancer, the researchers, led by Dr. Helmut Seitz, professor of medicine, gastroenterology and alcohol research at the University of Heidelberg, wrote in the study. Women at an elevated risk for breast cancer should avoid alcohol or consume alcohol only occasionally.
Researchers have examined the potential benefits of one alcoholic drink per day and found a variety of health effects.
- Heart Attack: Men who survived a heart attack may benefit from a drink or two per day. A survey of 1,800 men found that male heart attack survivors had a 42 percent lower risk of dying from cardiovascular problems than non-drinkers. Our study indicates that for men already consuming moderate amounts of alcohol, continuing to consume moderate amounts after a heart attack may be beneficial for long-term survival, Dr. Jennifer Pai, lead author of the study and assistant professor of medicine at and Harvard Medical School, told ABC News on Wednesday.
- Artery Hardening: People who have two drinks per day are at a 50 percent less risk of coronary calcification, a condition that occurs when cholesterol, fat and other waste material turn into a hard substance called plaque, according to a study. Plaque can restrict blood flow and lead to chest pain and heart attacks.
- Bone Loss: A drink per day increased the bone density in men and women and may reduce risk of osteoporosis or bone loss. A study of 360 people found that people who consumer moderate amounts of alcohol had significantly higher bone density in their neck and spine.
- Hearing: Researchers tested the hearing of the over 3,500 people residing in Beaver Dam, Wis., in 1987 and 1988 and then again in 1993 and 1995. Residents who had two drinks a day had less hearing loss than people who didn't drink or drank in excess of 4 drinks a day.
- Rheumatoid Arthritis: Rheumatoid arthritis patients who drink at least 10 alcoholic beverages per month have 20-30 percent less pain than non-drinkers. We found that arthritis was progressively less severe as alcohol frequency increased, with a definite difference compared to nondrinkers even in the least frequent alcohol consumption group, James Maxwell, study author and rheumatologist at the Rotherham Hospital, told HealthDay.
- Diabetes: A 20-year Finnish study found that moderate consumption of alcohol was linked to a reduced rate of type 2 diabetes. The survey began in 1975 and tracked all same-sex twins born in Finland since 1958. The twins answered questionnaires about their alcohol use, diet, physical activity and medical history in 1975, 1981 and 1990. The follow-up found only 580 cases of type 2 diabetes out of the almost 23,000 people tracked over the course of the study.
- High Blood Pressure: Women who drink moderate amounts of alcohol daily have a lower risk of hypertension. An 8-year study followed over 4,000 women found that The association between alcohol consumption and risk of chronic hypertension in young women follows a J-shaped curve, with light drinkers demonstrating a modest decrease in risk. Excess consumption, however, led to an increased risk of hypertension.
- Dementia: People who drink one to six alcoholic beverages per week have a lower rate of dementia. Researchers followed almost 6,000 adults ages 65 and older and found moderate drinkers had a 54 percent less chance of developing dementia than non-drinkers.
An alcoholic drink per day also comes with risks, researchers found.
- Cancer: Epidemiologists linked moderate alcohol consumption with mouth, pharynx, larynx, esophagus, colon and breast cancer, according to a 2007 report by the World Cancer Research Fund. From the point of view of cancer prevention, the best level of alcohol consumption is zero, the authors wrote in the report.
- Irregular heartbeat: A 2011 study found that alcohol consumption is directly correlated to risk of atrial fibrillation, a type of irregular heartbeat. Not consuming alcohol is most favorable in terms of AF risk reduction, researchers wrote.
- Liver disease: A 2005 study linked moderate alcohol consumption to liver disease, high blood pressure and increased violence.
The breast cancer study released Thursday is one of a long line of studies that examine the effects of daily drinking on health.
Moderate alcohol intake is one lifestyle factor well documented to have varying health effects in women - the increase in breast cancer risk and decrease in heart disease risk are both very well confirmed, Susan Hankinson, professor of medicine at Harvard Medical School, told Susan G. Komen for the Cure. Until we learn more about the mechanism, and possible ways to limit or eliminate the small increase in breast cancer risk with alcohol use, it will be important for individual women to weigh these risks and benefits.
Even researchers who found benefits in moderate alcohol consumption saw those benefits disappear as alcohol consumption increased pass a glass or two a day.
The message continues to be know your health, maintain your health, see your doctor regularly and understand your risk for cancer and heart disease, Susan Gapstur, vice president of epidemiology research at the American Cancer Society, told ABC News.
The researcher's findings echo those of a similar study, published in November, which found that consuming three to six alcoholic beverages per week raised the risk of breast cancer by 15 percent.
The American Cancer Society guidelines say that for women who don't drink, there is no reason to start drinking, and not just to prevent breast cancer, Susan Gapstur, vice president of epidemiology research at the American Cancer Society, who was not involved in the study, told ABC News. [Not drinking] can even prevent heart disease. This study underscores that these guidelines are reasonable.
However, women shouldn't stop drinking because of this study, Dr. Stefan Gluck, an oncologist at the Sylvester Cancer Center, who was not involved in the study, told ABC News. The 5 percent increased risk that comes from having one drink per day is minimal,
There are many other things that are more important, he said. If you look at the American Association for Cancer Research report from last year, 30 percent of all cancer deaths were attributable to smoking and another 30 percent were attributable to obesity.
The journal Alcohol and Alcoholism published the study on Thursday.