Diet ‘may be less important than genes’ in causing gout

Diet may be substantially less important than genes in the development of gout, a disease more common in men over 40 and which causes extreme pain and swelling in the joints, new research suggests.

The study published in the British Medical Journal says the widely held belief that gout is primarily caused by diet is not backed up by new evidence that genes may account for the development of high serum (blood) urate levels (hyperuricaemia), that often precede the rheumatoid condition.

In an editorial, researchers at Keel University say that people with gout often experience stigma from the misconception that it is a self-inflicted condition caused by unhealthy lifestyle habits and, as a result, are often reluctant to seek medical help.

The view is also “pervasive among healthcare professionals and in portrayals of gout in lay media”.

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The research authors write that, for centuries, diet has been seen as a risk factor for the development of gout.

“Recent studies suggest that certain foods (eg meat, shellfish, alcohol and sugary soft drinks) are associated with a higher risk of gout, while others (eg fruit, vegetables, low-fat dairy products and coffee) have a protective effect. Studies also show that genetic factors play an important role,” they wrote.

A team of researchers based in New Zealand analysed dietary survey data for 8,414 men and 8,346 women of European ancestry from five US cohort studies.

Participants were aged over 18 without kidney disease or gout and were not taking urate-lowering or diuretic drugs.

The researchers recorded all the factors that could have affected the results, such as sex, age, body mass index, daily calorie intake, education, exercise levels, and smoking status. They also measured levels of urate in the blood and recorded genetic profiles.

Analysis of the diets of those in the study revealed seven foods associated with raised urate levels - beer, liquor, wine, potato, poultry, soft drinks, and meat. Eight foods were associated with reduced urate levels - eggs, peanuts, cold cereal, skimmed milk, cheese, brown bread, margarine, and non-citrus fruits.

But the researchers also found that each of these foods explained less than 1 per cent of variation in urate levels. Scoring the participants’ diets, they found healthy diets were associated with lowered urate levels. An unhealthy diet was associated with increased levels. But again, each of the diet scores explained less than 0.3 per cent variance in urate levels.

The researchers point to some limitations, such as the use of different food questionnaires between studies, and the fact that the study was limited to individuals of European ancestry without gout.

Nevertheless, they say their data “are important in showing the relative contributions of overall diet and inherited genetic factors to the population variance of serum urate levels”.

“Our data challenge widely held community perceptions that hyperuricaemia is primarily caused by diet, showing for the first time that genetic variants have a much greater contribution to hyperuricaemia than dietary exposure,” the researchers said.