How Alcohol Weakens Body Defenses Against Illness

Chronic drinkers may appear to be healthy, but if they do become ill or injured, they may find it more difficult to heal. Alcohol consumption places stress on the hormone system and alter's the body's immune function.

A Salk Institute study of laboratory animals found that long-term alcohol consumption can harm the body's ability to respond to stressors like illness or injury. Too much alcohol can cause you to get sick by weakening your body's defenses, the researchers claim.

Catherine Rivier, a professor at the Clayton Foundation Laboratories for Peptide Biology at the Salk Institute in La Jolla, Calif., examined the effects of alcohol on the stress response in laboratory rats. One group of rats was exposed to alcohol vapors, while another, normal population of rats served as a control group.

Fight or Flight Reaction

The rats were exposed to alcohol vapors for six hours a day for eight days. All of the rats were then exposed to two types of stressors — an electric shock and injection of a toxin and their hormonal levels were observed.

The stress response, also known as the "fight-or-flight" reaction, is initiated in a region of the brain called the hypothalamus, which is seated deep in the center of the brain.

When the body is exposed to a stressor, the hypothalamus releases hormones called corticotropin-releasing factor (CRF) and vasopressin (VP). These two hormones travel to the pituitary gland, causing the secretion of adrenocorticotropin (ACTH), Rivier reported.

ACTH then goes into the bloodstream and causes the adrenal glands to produce corticosteroids. These chemicals cause the redirection of nutrients, like glucose, to the areas of the body that are under stress.

Stress Can Bring on Sickness

In the control rats, hormone levels remained normal and as expected. In the alcohol group, levels of CRF and VP and cellular response in the hypothalamus were greatly decreased.

If CRF levels are low, the body's responses will probably not be adequate during periods of stress, Rivier said. "CRF is absolutely central to our stress response."

"Stress can bring on sickness by altering the body's immune function, as when students get sick during an exam or when people have a death in the family," said Dipak Sarkar, professor, and chair of the department of animal sciences at Rutgers.

Consequences of Drinking Alcohol

Rivier said she would like to perform related research on alcohol-preferring rats, rats that drink alcohol voluntarily. Past studies have shown differences in the brains of rats who drank alcohol voluntarily and those who, like the rats in this study, were given alcohol without a choice.

"Most of what we and others have found regarding the consequences of alcohol have been found to occur in humans too," she said.