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Gout more linked to genes than diet

Genes more important than diet in causing gout, says study

Adrian O'Dowd

Friday, 12 October 2018

A person’s genes are more important than their diet when it comes to developing high blood urate levels that often precede gout, claims a study* published in The BMJ.

Researchers found evidence that genes play more of a role in the condition, which is contrary to the widely held belief that gout is primarily caused by diet.

The joint disease gout causes extreme pain and swelling and is most common in men aged 40 and older, caused by excess uric acid in the blood (known as hyperuricaemia) which forms crystals that collect around the joints.

For centuries, diet has been seen as a risk factor for the development of gout and recent studies have suggested that certain foods, such as meat, shellfish, alcohol and sugary soft drinks, are associated with a higher risk of gout, while others such as fruit, vegetables, low-fat dairy products and coffee, have a protective effect.

Other previous studies have shown that genetic factors play an important role, so to better understand how both diet and genes might influence the development of gout, 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.

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

Their serum urate levels were measured and their genetic profiles recorded. The researchers took into account factors that could have affected results, including sex, age, BMI, daily calorie intake, education, exercise levels, and smoking status.

Their dietary analysis revealed seven foods associated with raised urate levels (beer, liquor, wine, potato, poultry, soft drinks, and meat) and eight foods associated with reduced urate levels (eggs, peanuts, cold cereal, skimmed milk, cheese, brown bread, margarine, and non-citrus fruits).

However, each of these foods explained less than 1% of variation in urate levels.

Similarly, three diet scores based on healthy diet guidelines, were also associated with lowered urate levels, while a fourth, based on a diet high in unhealthy foods, was associated with increased urate levels, but each of these scores explained less than 0.3% variance in urate levels.

In contrast, genetic analysis revealed that common genetic factors explained almost a quarter (23.9%) of variation in the participants’ urate levels.

The researchers said: “Our data are important in showing the relative contributions of overall diet and inherited genetic factors to the population variance of serum urate levels.”

They concluded: “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.”

In a linked editorial**, researchers at Keele University in Staffordshire, said people with gout often experienced stigma from the misconception that it was a self-inflicted condition caused by unhealthy lifestyle habits and, consequently, were often reluctant to seek medical help.

They said: “The study … provides important evidence that much of patients’ preponderance to hyperuricaemia and gout is non-modifiable, countering these harmful but well-established views and practices and providing an opportunity to address these serious barriers to reducing the burden of this common and easily treatable condition.”

*Major T J, Topless R K, Dalbeth N and Merriman T R. An evaluation of the diet-wide contribution to serum urate levels: meta-analysis of population based cohorts. BMJ 2018;363:k3951. DOI:10.1136/bmj.k3951
**Watson L and Roddy E. Editorial: The role of diet in serum urate concentration. BMJ 2018;363:k4140. DOI:10.1136/bmj.k4140

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