Alcohol’s impact affected by age, sex, consumption and health
How much alcohol does it take to get intoxicated? Many people think a few beers at the football or a couple of glasses of wine with dinner won’t put them over the legal limit for driving. But how alcohol affects people is highly individual, with several factors in the mix.
Quick shots of liquor hit the bloodstream faster than slow sips of wine. Drinking on an empty stomach impairs reflexes more than consuming alcohol with food. And women and older drinkers generally hit legal intoxication levels sooner than men and younger people.
Carbonated beverages raise alcohol levels faster because the gas irritates the stomach lining, causing alcohol to be absorbed faster. (Sweet or caffeinated alcoholic drinks aren’t absorbed any faster; it just seems that way because people often consume more of them than they realise.) And factors such as fatigue, stress, illness and depression can magnify alcohol’s impact.
Drinkers who think they can tell when they’ve had enough are very often wrong. “Alcohol can affect your reflexes even if you feel fine,” says Samir Zakhari, former director of the division of metabolism and health effects at the US National Institute of Alcohol Abuse and Alcoholism.
In Australia, it is illegal to drive with a blood-alcohol concentration at or above .05 per cent, which represents the percentage of alcohol in the bloodstream. For learners and P-plate drivers, any alcohol in the blood is illegal. But how does BAC work? One of the most important factors is how fast the alcohol is consumed. It goes first to the stomach, then to the small intestine, where it is absorbed into the bloodstream and carried to the liver, where it is metabolised by liver enzymes.
“The liver can only break down the alcohol at the rate of about one drink per hour,” says Zakhari, who compares it with how fast a ticket-taker can let concertgoers through a gate.
Consuming one drink over an entire hour is unlikely to make a person inebriated. But drinking more than that amount, or the same amount faster, will overwhelm the liver. The excess alcohol “goes into the bloodstream and every other organ in the body, including the brain”, he says.
Once that happens, only time can unwind the effects. BAC generally falls by .015 per cent an hour for both men and women. Drinking coffee, having a shower or splashing cold water on your face may make you feel more alert but won’t change your BAC.
Consuming food along with alcohol causes it to be absorbed more slowly, since a valve at the base of the stomach closes to allow for digestion before sending it along. Without this stop, the alcohol travels to the small intestine and into the liver faster.
What you eat along with the alcohol doesn’t matter very much in terms of BAC. Fat in, say, a marbled steak slows the passage of food through the intestine, but only to a small extent. Likewise, drinking milk before consuming alcohol would have a negligible effect on blood levels.
Weight matters more than height, Zakhari says. A man who is 190cm and weighs 80kg will be as affected as a man who is 170cm and 80kg. But a man who is 190cm and 100kg will have a lower BAC after consuming the same amount. Women’s bodies also tend to have less water than men’s, which means the same amount of alcohol will yield an even higher BAC.
Age matters, too. Older people’s livers metabolise alcohol more slowly than younger people’s. But excess alcohol can do more damage to young brains, since some portions are still developing, particularly those that govern impulse control and executive function.
People who drink heavily and regularly don’t get as intoxicated as novice drinkers do on the same amount of alcohol and tend to have a lower BAC because their livers eventually produce more of a particular enzyme (Cytochrome P450 IIE1) that breaks down alcohol more quickly.
The Wall Street Journal
Source: The Wall Street Journal, Melinda Beck, 24th December 2015
