Anatomy of the New Year's Hangover

You knew it was coming--the throbbing head, the dry mouth, the muscles of jelly. The morning after a night of holiday celebration and you feel anything but jolly. You know you have a hangover and you know it was caused by drinking alcohol, but what really happened inside you?

In a timely article Andy Coghlan of New Scientist magazine detailed the path of alcohol through the human body and its painful effects along the way.

The hangover begins with a drink of a beverage containing alcohol, which has the chemical name ethanol. When someone drinks, ethanol reaches his or her stomach, where it passes to the bloodstream. A portion of the ethanol leaves the body without being processed--some is exhaled after it reaches the lungs; some makes it straight to the kidneys and leaves with a stream of urine. Most of the ethanol doesn't leave the body in a raw state. It ends up in the liver, which immediately begins processing.

In liver cells called hepatocytes, enzymes begin converting ethanol into acetaldehyde, a substance even more poisonous than alcohol. Some researchers think an acetaldehyde buildup is the cause of hangovers. Another enzyme removes acetaldehyde and converts it to acetic acid, which is relatively harmless. The acetic acid then drains from the liver into the bladder.

All types of alcohol drinks contain some methanol, a substance blamed for the worst hangovers. Whiskey, cheap red wine, fruit brandy and other dark spirits contain the most methanol, sometimes as much as two percent by volume. Vodka and other clear drinks contain the least. In the liver, methanol takes 10 times longer than ethanol to break down.

The most obvious source of headaches due to hangovers is dehydration caused by alcohol blocking the signals that control the body's plumbing. Alcohol riding the bloodstream eventually makes its way to the pituitary gland at the base of the brain. There, it suppresses an anti-diuretic hormone that tells the kidneys to reabsorb water from urine. The hormone normally orders the body to conserve water, but alcohol dulls the command, causing people to lose far more water to urination than they take in with the alcohol.

The body reacts to the open floodgates by borrowing water from other organs, such as the brain. As a result, the brain shrinks. While that may not cause pain by itself, the brain has a covering called the dura that's connected to the skull by pain-sensitive filaments. Deformation of the dura might cause the headaches that come with a hangover.

Alcohol also alters the flow of electrolyte ions through brain cells, possibly causing morning-after grogginess by slowing the speed at which neurons fire. The shakiness and feeling of weakness following a night of drinking is caused by alcohol causing the body's store of blood sugar to be depleted. The liver stores sugar as glycogen, which alcohol breaks down to glucose, which is then lost with urine.

Coghlan points out that science could probably come up with a hangover cure, but researchers have resisted because of the hangover's function of deterring repeat bouts of heavy drinking. Coghlan did ask a research physician his remedy for a hangover, though. The doc's advice: eat plenty of food before and after drinking to slow the uptake of alcohol, drink plenty of water before bed to stave off dehydration, and drink a cup of sugary tea in the morning.