A gene variant (变体) that causes the "alcohol flush (脸红)" reaction increases the risk of heart disease by causing inflammation of blood vessels (脉管), especially in drinkers. Around 8 percent of the world's populations has a gene variant called ALDH2*2 that impairs the body's ability to break down alcohol and causes unpleasant symptoms such as flushing soon after people drink. Now, researchers have shown why this change also raises the risk of heart disease.

"We are trying to understand why ALDH2*2 is associated with a higher risk of coronary arte (冠状动脉) disease at a cellular (细胞的) level," says Hongchao Guo at Stanford University in California.

The ALDH2*2 gene encodes one version of the enzyme (酵素) alcohol dehydrogenase (脱氢酶), which breaks down the toxic acetaldehydes (乙醛) produced when alcohol is metabolized (代谢), and also mops up other harmful substances known as free radicals.

The gene variant also impairs the growth of new blood vessels. "That means that when there is a heart attack, when there is a need of blood vessel growth, carriers have less ability to generate new blood vessels," says Guo.

The team found that an existing diabetes (糖尿病) drug called empagliflozin may reduce these harmful effects in people with ALDH2*2 who drink a lot of alcohol. But for Wu, the take-home message is clear. "If you're missing this enzyme, try not to drink," he says. "If you drink consistently, you are at much higher risk of heart disease, hypertension, diabetes and cancer."

Given its many negative consequences, there has been debate about why this change spread and became common, today being found in more than a third of people of cast Asian origin.

"My only explanation is that if you are missing this enzyme, you tend to drink less and there's therefore less chance of you becoming alcoholic," says Wu.