Increased Dietary Vitamin C Intake May Help Reduce Gout Risk, Study Finds

New research is calling attention to an inverse association between dietary vitamin C intake and the risk of developing gout.¹

The analysis of data from more than 10,000 National Health and Nutrition Examination Survey (NHANES) 2013-2018 participants revealed a reduced risk of gout among those who reported consuming greater quantities of dietary vitamin C. Results also pointed to a reduced risk of hyperuricemia with increased vitamin C intake.¹

Gout is the most common type of inflammatory arthropathy in adults, affecting an estimated 3.9% of adults in the US. Although its etiology is multifaceted and involves genetics, diet, and lifestyle, high serum uric acid is a key risk factor for gout. The antioxidant properties of vitamin C have led to speculation that it may indirectly reduce uric acid production.^1,2

“Currently, evidence regarding the association between dietary vitamin C levels and gout is insufficient,” Shengguang Li, of the department of rheumatology and immunology at Peking University International Hospital in China, and colleagues wrote.¹

To fill this gap in research, investigators assessed cross-sectional data on gout, dietary vitamin C intake, and other variables from individuals > 20 years of age who participated in NHANES 2013-2018. Pregnant females or those with missing data on gout, dietary vitamin C intake, or covariates were excluded from the analysis.¹

Vitamin C intake from the first survey in the NHANES database was measured through a 24-hour dietary recall during an interview using the automated multiple-pass method to collect detailed information about all foods and beverages consumed in the previous 24 hours. Nutrient content, including vitamin C, was calculated using the food composition database.¹

Vitamin C intake from the second survey was measured through a second 24-hour dietary recall conducted via telephone a few days after the initial interview. The same automated multiple-pass method was used to collect detailed dietary information about the participants’ consumption over the previous 24 hours, and vitamin C content was calculated using the same food composition database, measuring vitamin C intake from a different time point to account for day-to-day variability in the participant’s diet.¹

Participants were categorized into 4 quartiles based on their calculated dietary vitamin C intake:

• Q1 (≤19.9 mg/day)
• Q2 (19.9-49.7 mg/day)
• Q3 (49.7–110.375 mg/day)
• Q4 (≥110.375 mg/day)

Gout was defined as a positive answer to the question “Has a doctor or other health professional ever informed you that you had gout?”. Serum uric acid (SUA) concentration was measured at the NHANES Laboratory for all 3 cycles, and hyperuricemia was defined as an SUA concentration >6mg/dL.¹

In total, 12,589 participants from the NHANES 2013-2018 were included in the present analysis, 652 (5%) of whom experienced gout. The average age was 49.9 ± 17.5 years and 50.7% of participants were female. There were 3177 participants in Q1, 3142 in Q2, 3148 in Q3, and 3122 in Q4.¹

Investigators pointed out a significant difference in age across quartiles (P <.001). Specifically, age increased from 48.3 ± 17.3 years in Q1 to 50.3 ± 17.6 years in Q4. The sex distribution also varied, with males comprising 48.9% of Q1 and 53% of Q4 (P <.001).¹

Results showed the prevalence of gout decreased across quartiles, with Q1 showing the highest percentage at 5.40% (n = 169) and Q4 showing the lowest at 4.60% (n = 142). After adjusting for other risk factors, investigators observed a significant correlation between vitamin C intake and gout (odds ratio [OR], 0.88; 95% CI, 0.79–0.97; P = .015). Additionally, when dietary vitamin C consumption was analyzed using quartiles, there was a significant inverse association between dietary vitamin C and gout after adjusting for potential confounders.¹

Compared with individuals with lower vitamin C consumption in Q1, the adjusted OR values for dietary vitamin C intake and gout were 0.87 (95% CI, 0.69–1.1; P = .237) in Q2, 0.81 (95% CI, 0.64–1.02; P = .076) in Q3, and 0.77 (95% CI, 0.6–0.99; P = .042) in Q4. Subgroup analyses revealed significant interactions between vitamin C levels and gout, notably influenced by sex. Investigators observed a similar inverse association between vitamin C intake and gout when they used data on dietary vitamin C from the second survey, even after adjusting for all covariates (OR, 0.81; 95% CI, 0.72–0.91; P <.001).¹

Vitamin C was also negatively associated with hyperuricemia (OR, 0.94; 95% CI, 0.9–0.98; P = .005). Compared with Q1, the adjusted OR values for dietary vitamin C from the first survey and hyperuricemia were 0.77 (95% CI, 0.69–0.86; P = .65) for Q2, 0.81 (95% CI, 0.72–0.91; P = .014) for Q3, and 0.72 (95% CI, 0.64–0.81; P <.001) for Q4.¹

Investigators acknowledged multiple limitations to these findings, including the cross-sectional study design; the inability to establish causality between vitamin C intake and gout; the potential lack of generalizability to other populations due to dietary differences; residual confounding; and recall bias for vitamin C intake.¹

“There is a negative association between dietary vitamin C intake and gout prevalence among adults in the United States,” investigators concluded.¹ “The results of this study highlight the association between dietary vitamin C intake and gout.”

References

1. ^{Zou Y, Liu Y, Li S, et al. Association between dietary vitamin C intake and gout among American adults. Front. Immunol. https://doi.org/10.3389/fimmu.2024.1431323}
2. ^{National Kidney Foundation. Quick Facts: Gout and Chronic Kidney Disease. Accessed October 11, 2024. https://www.kidney.org/kidney-topics/quick-facts-gout-and-chronic-kidney-disease}