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Last Updated: Tuesday, 15 July, 2003, 06:30 GMT 07:30 UK
Genetic link to heartburn

Heartburn is not just caused by lager and curry - but also our genes, say researchers.

Scientists have examined the condition which causes heartburn, known as acid reflux or gastro-oesophageal reflux disease (GORD).

The condition has been linked to unhealthy living and a poor diet.

But they found that our genes play a significant role in determining the likelihood of developing the condition - one of the most common digestive disorders in the developed world.

Eating large meals
Being overweight
Bending a lot
Wearing tight clothing around the waist
It is thought that up to 20% of the population have symptoms of the condition every week.

The condition is caused by small amounts of acid from the stomach rising up into the gullet.

The gullet, unlike the stomach, does not have a protective lining. So when it is exposed to the acid, it can become inflamed and painful - leading to the sensation we call heartburn.

But although heartburn is the most common symptom of acid reflux, it is not the only problem. Regular sufferers are at increased on cancer of the gullet.

New cases of this form of cancer have been rising faster than any other cancer over the past three decades.

The latest research is based on data from 2,000 pairs of identical and non-identical twins.

Overall, 18% of those who took part showed symptoms of acid reflux.

But an identical twin was over 1.5 times as likely as a non-identical twin to have the condition if their fellow twin was affected.

After taking account of known risk factors, the researchers calculated that 43% of the chance of developing acid reflux is attributable to genes.

Immune response

Lead researcher Dr Nigel Trudgill, from Sandwell General Hospital, West Bromwich, told BBC News Online it was unclear whether some people were prone to acid reflux because of structural weakness in the muscle separating the stomach from the gullet, or because they were more vulnerable to the effects of stomach acid once it had escaped.

However, he thought the second option more likely.

Some people's genetic make-up may have weakened the ability of cells in their gullet to defend themselves against stomach acid, he said.

Alternatively, it was possible that their inflammatory response was more pronounced than usual.

Dr Trudgill stressed that environmental factors, such as bad diet, were still important.

"Some people who are genetically predisposed may get acid reflux whatever they do," he said.

"But for most people although genetics may be important, environmental factors are equally or more so.

"And people who have symptoms of acid reflux in their family should be even more careful about what they eat, or they may ultimately pay the price and end up with cancer."

Dr Martin Sarner, secretary of the Digestive Disorders Foundation, told BBC News Online that in cases where acid reflux was linked to structural abnormality then it was not surprising that this was governed by genetic factors.

However, he said: "There is no question that the symptoms are much worse if you put yourself in a horizontal position with a stomach full of food and fluid so the best way to treat it is not to go to bed after you have eaten."

The research is published in the journal Gut.

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