The reason: Drinking too much can double the weight loss that typically occurs with cancer, claims a Washington State University study that was based on research with lab mice. That weight loss, which includes a depletion of body fat, can cut down on survival time.
"The amount of alcohol we fed to the animals is at a level that would be consumed by alcoholics," says study author Gary G. Meadows, a professor of pharmaceutical sciences.
Typically, that means 30 percent or more of total daily calories are coming from alcohol. "We don't know if lower levels would cause the same effect," Meadows adds.
To study alcohol's effect on cancer, Meadows and his colleagues injected some mice with melanoma cells and left others cancer-free. They fed some mice water and others alcohol. The mice with cancer that were fed alcohol had nearly twice the weight loss as the mice with cancer that were given water.
The weight loss wasn't due to decreased food intake or dehydration, says Meadows, whose study appears in the new issue of Alcoholism: Clinical & Experimental Research.
Past studies about alcohol and its effect on cancer have been contradictory, Meadows says. Alcohol consumption has been linked to the development of oral cancers, liver cancer and possibly breast cancer. Some studies have found alcohol increases the spread of cancer cells, while others found it decreases it.
In the latest study, Meadows and his colleagues looked at the effect of alcohol on weight loss, not the tumor's spread. However, even if alcohol decreases metastasis (the spread of cancer cells), the overall effect of excessive drinking on cancer is still bleak due to the weight loss, he says.
"In another [mouse] study we did, this level of alcohol decreased the metastatic spread, but it shortened survival and induced the wasting process. Overall, [excessive] alcohol consumption has a negative impact on the prognosis of cancer," he says.
In the latest study, Meadows didn't measure how much the survival time was shortened, but in an earlier animal study he found excessive alcohol intake shortened survival by 20 percent to 30 percent.
Exactly how excessive alcohol intake adversely affects the progression of cancer isn't known, Meadows says. "But the combination of alcohol and a tumor result in some sort of interaction that induces fat loss. If you give a cancer-free animal alcohol, they put on fat," he explains.
When alcohol increases metastasis, it may do so by depleting the natural killer cells that try to contain the spread of the cancer, says Carl Waltenbaugh, a professor of microbiology and immunology at Northwestern University Medical School. He studies the effect of alcohol on immune-system response and reviewed the Meadows' study for the journal.
Alcohol can cause weight loss in mice with cancer by increasing the levels of leptin, a multipurpose hormone that can, among other things, speed up fat metabolism, he says.
Waltenbaugh says Meadows' latest findings aren't surprising. Still, they're useful.
An alcoholic with cancer would probably be wise to stop drinking immediately. "But that's not so easy," Waltenbaugh says.
It's not unusual for alcoholics to take in half of their daily calories from alcohol, Waltenbaugh adds.
Meadows says it's premature to make recommendations on alcohol use for cancer patients, but, clearly, heavy drinking increases the disease's toll.
Future studies should focus on such areas as the amount and duration of alcohol intake that leads to body fat loss, and whether abstinence helps slow cancer's progression, Waltenbaugh and Meadows agree.
What To Do: For more information on alcoholism, see the National Institute on Alcohol Abuse and Alcoholism. For information on cancer, visit the American Cancer Society.