Alcohol: Toxic or Tonic?

For some people, drinking in moderation can be beneficial. But at higher levels, it's deadly.

The health effects of alcohol have been debated for hundreds of years. The consensus today is that alcohol, like many things in life, can be either beneficial or damaging depending on how it's used.

After much investigation, researchers still share uncertainty about the benefits of alcohol, and whether benefits from modest drinking can offset alcohol’s risks.

Many researchers feel convinced that heart health benefits can be gained from mild to moderate alcohol drinking, defined as 1 drink per day for women and 2 drinks per day for men. (A "drink" equals 12 ounces of beer or wine cooler, 5 ounces of wine, or an ounce and a half of distilled spirits.)

Some experts disagree, saying that alcohol has not been proven to improve heart health. These experts worry that much-discussed surveys suggesting a heart benefit from alcohol have fooled us.

With heavier drinking, possible benefits are lost, and significant risks are present.

When it comes to alcohol, women are at a disadvantage that has very little to do with body size: A 250-pound woman is more likely to be damaged by alcohol than is a 140-pound man. That's because women absorb alcohol much more efficiently after it is consumed. Women also have higher levels of the liver enzyme that breaks down alcohol in the body, which allows them to metabolize alcohol about 20% faster than men. Although faster alcohol metabolism may seem to be an asset, it isn't a good thing. Much of the damage done to the body is caused not by alcohol itself but by acetaldehyde, a highly reactive byproduct of alcohol metabolism. When alcohol is broken down quickly, as it is in women, more of this toxic chemical is produced in less time, causing more damage.

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Health benefits, still debated

The greatest potential health benefit of alcohol is its apparent ability to protect the arteries and the heart. Studies that observed the drinking patterns and heart health of very large groups of people have linked mild or moderate alcohol consumption to a lower risk of death from coronary heart disease. Similar research indicates that moderate alcohol use is linked with a lower risk of stroke.

Scientists have identified several reasons that alcohol may have a beneficial effect. Four theories have been suggested: First, alcohol increases blood levels of the "good" HDL (high-density lipoprotein) cholesterol, which clears plaque from the arteries. Second, alcohol affects the body's clotting mechanisms, decreasing the likelihood that a clot will block a blood vessel. Third, alcohol is linked to lower levels of C-reactive protein, a substance that is linked to lower levels of inflammation in the bloodstream. Finally, some researchers feel that alcohol may have anti-oxidant effects that may prevent injury in blood vessels.

Regardless of whether you drink beer, wine or spirits, the possible beneficial (and harmful) effects of alcohol are the same. However, there is some controversy about whether red wine has additional heart benefits that stem from something other than its alcohol content. Red wine — and red grape juice, for that matter — has high levels of flavonoids, natural chemicals that act as antioxidants and may decrease the harmful effects of "bad" LDL (low-density lipoprotein) cholesterol.

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Health hazards

Despite any social benefits and despite its potential heart health benefits, alcohol has dangers. Even at moderate levels (just a drink or two per day), alcohol can cause serious problems:

• Drug interactions. Many drugs, like alcohol, are metabolized by the liver. Because the liver has limited processing capacity at any given time, these substances can compete with alcohol for prompt processing. Additionally, alcohol can block the function of selected enzymes (proteins) that line the intestine. These enzymes are part of a system well-known to doctors as the "cytochrome P450" system and are responsible for breaking down many medications and toxins. Alcohol, when consumed, may block the effects of some drugs and augment the effects of others.
• Night blindness. Alcohol can decrease the retina’s ability to adapt to low light.
• Accidents. Alcohol affects judgment and slows reflexes, which can lead to falls or to accidents involving vehicles or other machinery.
• Breast cancer. Even consuming just one drink per day may increase the risk of breast cancer in women. Women may be able to decrease their breast cancer risk by taking extra folic acid daily, because use of this vitamin was linked to a lower breast cancer rate among drinkers in one large survey.

• Liver disease. Alcoholic hepatitis and cirrhosis are the two most common liver problems that result as a consequence of heavy drinking. Alcoholic hepatitis is inflammation of the liver, which ultimately can cause permanent damage if drinking continues. Cirrhosis occurs when damage to the liver is so severe that scarring interferes with blood flow and liver function.
• Cancers. In addition to breast cancer (which can result from mild to moderate alcohol use), heavy alcohol use can cause other cancers. Alcohol appears to be especially dangerous when it is combined with smoking, significantly increasing the risk of cancer of the throat and esophagus. The risk of liver cancer increases in alcoholics who have hepatitis or cirrhosis. 
• Hypertension and stroke. Heavy drinking leads to high blood pressure, which increases the risk of stroke.
• Heart problems. Alcoholism can cause cardiomyopathy and heart failure. If this happens, the heart enlarges, weakens and ultimately loses its ability to pump effectively. Consuming very large quantities of alcohol can cause sudden death from heart arrhythmias.
• Pancreatitis. Overuse of alcohol can result in recurrent attacks of severe pain caused by inflammation of the pancreas, the organ that makes enzymes for digestion and the hormone insulin. Continued alcohol use can permanently damage the pancreas, leading to malnutrition and diabetes.
• Gastrointestinal symptoms. Alcohol can cause a wide range of common, uncomfortable but reversible problems, including gastritis (inflammation of the lining of the stomach), diarrhea and weight loss. These interrelated problems are all due to the effects that alcohol has on the lining of the stomach, as well as impairment of intestinal enzymes and transport systems.
• Anemia and low platelets. Alcohol limits the productivity of your bone marrow, so you can have a low hematocrit (anemia) or a low platelet count. A low platelet count makes you more susceptible to bleeding or bruising.
• Insomnia. After a heavy alcohol exposure wears off, your brain may become overstimulated in recovery. This is an early symptom of alcohol withdrawal.
• Fractures and osteoporosis. In addition to causing thinned bones, alcohol can lead to falls. Both of these events make a drinker more likely to get a fractured hip or other bone injury.
• Dementia. Continued alcohol exposure causes steady injury to brain cells. It is a major cause of dementia.
• Reproductive effects. People who drink heavily may become infertile. In men, alcohol lowers sperm count and can cause impotence. In women, alcohol can cause hormonal changes that can result in irregular menstruation and infertility.