Dietary butyric acid intake, kidney function, and survival: The National Health and Nutrition Examination Surveys, 2005-2018.

BACKGROUND

Although preclinical data support the hypothesis that butyric acid supplementation improves kidney health, the clinical significance of dietary butyric acid intake in patients with chronic kidney disease (CKD) remains unconfirmed in large-sample studies. This study aimed to investigate the association between dietary butyric acid intake and all-cause mortality in the United States population, stratified by kidney function.

METHODS

We examined the relationship between dietary butyric acid intake, assessed through a 24-h dietary recall, and all-cause mortality among 23,008 consecutive adult participants from the National Health and Nutrition Examination Surveys (NHANES, 2005-2018), categorized by impaired versus normal kidney function (estimated glomerular filtration rate <60 vs ≥ 60 mL/min/1.72 m2), using multivariable Cox models. We also employed a restricted cubic spline based on Cox regression models to elucidate the nonlinear relationship between dietary butyric acid intake and mortality in patients.

RESULT: In participants with impaired kidney function, high dietary butyric acid intake was associated with lower mortality, while lower intake levels (reference) showed no such association: adjusted HRs (aHRs) were 0.67 (95 % CI: 0.45, 1.00), 0.65 (95 % CI: 0.45, 0.94), and 0.58 (95 % CI: 0.38, 0.89) for intake levels of the square root of butyric acid 0.25-0.45, 0.45-0.75, and >0.75 g/day, respectively. However, in participants with normal kidney function, no association between butyric acid levels and mortality was observed. Additionally, we identified an L-shaped association between the levels of the square root of dietary butyric acid intake and all-cause mortality in the CKD population, reaching a plateau at 0.52 g/day (butyric acid intake of approximately 0.27 g/day).

CONCLUSION

This study revealed a nonlinear association between high dietary butyric acid intake and reduced all-cause mortality in patients with chronic kidney disease. A plateau occurs after 0.27 g/day, and for individuals with CKD whose butyric acid intake is below approximately 0.27 g/day, increasing a butyrate-rich diet or supplementing with butyric acid preparations may help prevent progression to renal failure and associated adverse outcomes in CKD patients, thereby reducing mortality. Therefore, it can be considered a new therapeutic strategy for the treatment of chronic kidney disease.