Gout patients can eat soy products, local study finds

SINGAPORE - Soy products do not increase the risk of gout, and people who already have the condition can eat them, a new local study has found.

This goes against the common belief that gout sufferers should avoid eating soy and legume products as they are high in the organic compound purine.

Although purine-rich foods like shellfish and meat are known to cause higher levels of uric acid in one's blood, which may be retained, soy does not appear to have the same effect. Other purine-rich foods may cause sodium urate crystals forming in the joints, causing aches and pains, said researchers from the Duke-NUS Graduate Medical School and the National University Hospital, who did the study.

This myth is so common that even health professionals believe it, they said.

But their study - involving more than 50,000 Chinese in Singapore - found that those who consumed the most soy products were at lower risk of gout than those who ate the least.

The interviewees were 45 to 74 years old when they were recruited from 1993 to 1998. Researchers asked about their dietary habits then, and followed up with with questions on their medical status from 1999 to 2004 and 2006 to 2010. Out of the 51,114 they followed up on, 2,197 had developed the condition.

"Based on our study, soy might in fact have a protective effect against gout but this needs to be further studied," said Dr Teng Gim Gee, senior consultant at the division of rheumatology at the National University Hospital.

The finding, that soy is not associated with higher risk of gout, confirms six other studies done in places like Japan and Taiwan, which show that consuming soy does not increase uric acid in one's blood, said Professor Koh Woon-Puay, who studies population health at the Duke-NUS Graduate Medical School.

The local study is the first to draw a direct link between gout and soy. Also, increased uric acid, though a necessary condition, may not be sufficient for causing gout. Other factors like genes play a part too.

Scientists have yet to confirm why soy, though high in purine, is not associated with higher uric acid retention. But they suspect, based on a study in Japan, that soy may increase uric acid excretion and thus play no role in increasing the risk of gout.

In the local study, the group which ate the most red meat had an 8 per cent higher risk of gout. Surprisingly, the group which consumed the most poultry had a significantly higher 27 per cent increased risk.

Up to 97 per cent of the red meat consumed by those polled was pork as older Chinese seldom eat beef and lamb, unlike in Western countries.

The trend has to be studied further as previous research did not break meat up into different categories to look at their associations with gout, Prof Koh said.

"Though the study surveyed only Chinese, we have no reason to expect different results in other racial groups," she added.

About 4 per cent of Singaporeans over the age of 45 suffer from gout, which is more common in males.

kashc@sph.com.sg