Kiwi scientists have discovered a "Jekyll and Hyde" human gene variant that can "turn bad" when affected by sugary drinks and raise the risk of developing gout.
The study by University of Otago and Auckland scientists has found that sugary drinks reverse the benefits of a gene variant that would usually protect against gout.
Gout is a common and debilitating arthritic disease which is caused by high levels of uric acid in the blood.
The acid crystallises in the joints causing a painful inflammatory response.
It's the most common form of arthritis in New Zealand, with particularly high rates in men.
The study, published online on Thursday in the international journal Annals of the Rheumatic Diseases, shows that when the variant of the gene SLC2A9 behaves correctly, it helps transport uric acid out of the blood stream and facilitates its excretion through the kidney.
"But when people with this gene variant consume sugary drinks, it takes on Jekyll and Hyde characteristics," Associate Professor Tony Merriman said.
"The apparent function of the gene variant reverses, such that we think uric acid is instead transported back into the blood-stream and the risk of gout is increased.
"So, not only does sugar raise uric acid in the blood due to processing in the liver, but it also appears to directly interfere with excretion of uric acid from the kidney. This was a quite unpredictable interaction."
The scientists also found that consuming sugar-sweetened soft drinks increases the risk of gout in New Zealanders, including for Maori and Pacific people, independent of their weight.
"Each daily 300ml serving of sugar-sweetened drink increases the chance of gout by 13 per cent," Prof Merriman said.
Gout attacks can be prevented by the prescribed daily use of the medicine allopurinol, which lowers the production of uric acid in the blood.
Now, as a result of the new research, Prof Merriman also recommends people with gout should not drink any sugary drinks.