Spanish research appearing to show that very heavy drinking can reduce men's risk of heart disease has come under fire from scientists who say the study is flawed and should not encourage anyone to drink more.

The controversial study found that men who drank moderate, high and very high levels of alcohol had a lower risk of coronary heart disease.

Many previous studies have suggested that moderate drinking -- usually defined as a drink or two per day -- can be a healthy habit, particularly when it comes to heart disease risk.

But experts have warned that heavy drinking can damage organs and lead to early death.

The Spanish study, released in the British Medical Journal's Heart publication on Thursday, assessed the alcohol intake of 15,500 men and 26,000 women aged between 29 and 69, who were asked how much they had drunk in the preceding year.

People were classed as non-drinkers, former drinkers, low, moderate, high and very high drinkers. The latter drank more than 90 grams of alcohol a day, equivalent to around a dozen drinks.

Following the patients for 10 years and mapping the number of coronary problems they had, the researchers said the overall results for men showed that drinking alcohol cut the risk of heart disease by 30 percent, and that heavy drinking cut the risk even more than moderate drinking.

No significant effect was found in women.

Spain is the world's third largest producer of beer and wine and its per capita consumption of alcohol places it sixth in the world. But it also has one of the lowest death rates from coronary heart disease in the world, the researchers wrote.

But they warned that according to the World Health Organization, 76 million of the estimated 2 billion people in the world who drink alcohol suffer ill health as a result, and alcohol causes around 1.8 million deaths every year.

Robert Sutton, professor of surgery at the University of Liverpool, said the study had several flaws and should not be taken to suggest heavy drinking could improve health.

This ... study was based on self-reported information in which those drinking more stated they had less heart disease, but those drinking more would probably be less likely to see doctors and have heart disease identified, he said in a statement.

Martin McKee, professor of European public health at the London School of Hygiene and Tropical Medicine, said that while there was evidence that moderate drinking can help protect against heart problems, the relationship between alcohol and heart disease is controversial.

Certainly, people should not be encouraged to drink more as a result of this research, he said.