High consumption of sugar-sweetened beverages is a risk factor for gout, even among individuals who carry a gout-protective variant of a gene involved in renal excretion of uric acid, researchers in New Zealand found.
Compared with controls who never drank sugar-sweetened beverages, New Zealanders of European Caucasian ancestry who consumed four of these drinks daily had an almost seven times greater adjusted risk for gout (OR 6.89, 95% CI 1.05-45.44, P=0.020), according to Tony R. Merriman, PhD, of the University of Otago in Dunedin, New Zealand, and colleagues.
And among those of Maori and Pacific Islander ancestry, the adjusted odds ratios were 5.19 (95% CI 1.48-18.17) and 2.84 (95% CI 1.04-7.77, P=0.050), respectively, the researchers reported online in Annals of the Rheumatic Diseases.
And for all the groups combined, carriers of the protective allele of SLC2A9 had a 15% increase in gout risk for each additional extra sugary drink consumed per day, compared with a 12% increase for noncarriers (P=0.002).
These findings "imply a physiologic mechanism whereby high simple sugar exposure derived from soft drinks over-rides the positive versus negative risk discrimination of the SLC2A9 gout risk alleles by interfering with the ability of SLC2A9 to transport uric acid," Merriman and colleagues observed.
To see what the effects might be on prevalent gout in a country where the typical beverage sweetener was sucrose rather than high-fructose corn syrup, and to examine the potential genetic interaction, the researchers recruited 925 patients who had been diagnosed with gout and 709 controls. They also included 7,075 participants in the U.S. Atherosclerosis Risk in Communities (ARIC) study as additional controls.
On an unadjusted analysis, there was no evidence of an association between sugar-sweetened drink consumption and gout. However, significant differences emerged after adjustment for gout risk factors including age, sex, body mass index, hypertension, renal disease, and alcohol and fruit consumption, the researchers noted.
Age was an important confounder, they pointed out, possibly because young people tend to drink more of these beverages.
When they looked at the relationship between increased sugar-sweetened beverage intake and the protective ALC2A9 C allele, they found that in some ethnic groups, those with the protective allele had higher risks for gout than without the allele :
- New Zealand Pacific Islanders, 71% increased risk with the allele versus 11% increased risk without the allele
- New Zealand European Caucasians, 27% versus 16%
- ARIC, 16% versus 5%
However, the reverse was seen in the New Zealand Maori group, where the odds ratios for gout were 1.19 (95% CI 1.03-1.37) for the major, unprotective allele and 0.76 (95% CI 0.49-1.16) for the protective C allele.
Because of this difference in the Maori group, there was heterogeneity in the data for interaction between the genetic variant and sugary drinks (P for interaction = 0.39).
Therefore, further analysis in other groups is needed to confirm the association, the researchers cautioned.
The researchers also looked at the effects of sugar-sweetened drink consumption on serum urate levels according to SLC2A9 genotype, and found that increased consumption among carriers of the protective C allele was associated with a greater increase in urate levels (0.005 mmol/L, P=8.7 x 10-5).
"Our data support the recommendation that reduction of [sugar-sweetened beverage] consumption should be pursued in established gout," they concluded.
A limitation of the study was the fact that little information was available on other dietary factors that could influence gout risk, such as consumption of purine-rich foods. In addition, this was a case-control study so other causal factors may be involved.
The study was funded by the Health Research Council of New Zealand, Arthritis New Zealand, New Zealand Lottery Health, the National Institues of Health, and the University of Otago.
The authors reported no conflicting interests.
- Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner