Acid reflux, also known as gastro-oesophageal reflux (GERD), is common and one of the most frequent causes of indigestion.
Symptoms arise when stomach acid flows back into the oesophagus or gullet - often as far as the mouth - usually as a result of a weakened muscle at the bottom of the gullet.
Typical symptoms include heartburn, excessive belching, and even respiratory problems.
Researchers from Stockholm, Norway undertook a study to evaluate the lifestyle-related risks associated with GERD.
The research group based their work on 47,556 people, who had previously taken part in two major public health surveys in Nord-Trondelag, a county in Norway.
The first survey, involving more than 74,000 people, was conducted between 1984 and 1986; the second spanned the period 1995 to 1997 and included more than 65,000 people.
In the second survey, researchers identified 3153 people who complained of severe heartburn and reflux into the mouth within the preceding 12 months as having acid reflux. Their average age was 52.
The research team quizzed the participants about their lifestyles, including diet, exercise, alcohol intake, and tobacco habit.
The researchers then compared their responses with those from 40,210 people without symptoms, whose average age was 48.
|Heavy coffee drinkers (around 7 cups a day) were 40% less likely to develop acid reflux than those who drank 1 or fewer cups a day|
The research group found that lifestyle was strongly linked to acid reflux symptoms.
People who had smoked every day for more than 20 years were 70% more likely to have acid reflux than non-smokers.
In addition, the researchers noted that salt intake proved to be as great a risk factor.
Participants who routinely added salt to meals were 70% more likely to have acid reflux than those who did not.
Salted meat or fish eaten three or more times a week ensured participants were 50% more likely to have acid reflux than those who never ate these foods.
The investigators found that some lifestyle factors seemed to confer protection.
Regular consumption of high fibre brown bread and 30 minutes of strenuous exercise at least once a week both halved the risk of developing acid reflux.
The researchers suggested that the protective capacity of dietary fibre might lie in the fact that it mops up large amounts of nitric oxide in the stomach, produced from nitrites in the diet, say the authors.
Nitric oxide relaxes the muscle at the bottom of the gullet, so promoting reflux.
Surprisingly, the researchers found that heavy coffee drinkers (around 7 cups a day) were also around 40% less likely to develop acid reflux than those who drank one or fewer cups a day.
However, the authors point out that people with acid reflux might abstain from coffee drinking, which could potentially skew the results.
Neither tea nor alcohol, irrespective of the quantities drunk, had any impact on risk.