Dietary acid load and chronic kidney disease among adults in the United States

BACKGROUND: Diet can markedly affect acid-base status and it significantly influences chronic kidney disease (CKD) and its progression. The relationship of dietary acid load (DAL) and CKD has not been assessed on a population level. We examined the association of estimated net acid excretion (NAE(es)) with CKD; and socio-demographic and clinical correlates of NAE(es). METHODS: Among 12,293 U.S. adult participants aged >20 years in the National Health and Nutrition Examination Survey 1999-2004, we assessed dietary acid by estimating NAE(es) from nutrient intake and body surface area; kidney damage by albuminuria; and kidney dysfunction by eGFR < 60 ml/min/1.73 m(2) using the MDRD equation. We tested the association of NAE(es) with participant characteristics using median regression; while for albuminuria, eGFR, and stages of CKD we used logistic regression. RESULTS: Median regression results (β per quintile) indicated that adults aged 40-60 years (β [95% CI] = 3.1 [0.3-5.8]), poverty (β [95% CI] = 7.1 [4.01-10.22]), black race (β [95% CI] = 13.8 [10.8-16.8]), and male sex (β [95% CI] = 3.0 [0.7- 5.2]) were significantly associated with an increasing level of NAE(es). Higher levels of NAE(es) compared with lower levels were associated with greater odds of albuminuria (OR [95% CI] = 1.57 [1.20-2.05]). We observed a trend toward greater NAE(es) being associated with higher risk of low eGFR, which persisted after adjustment for confounders. CONCLUSION: Higher NAE(es) is associated with albuminuria and low eGFR, and socio-demographic risk factors for CKD are associated with higher levels of NAE(es). DAL may be an important target for future interventions in populations at high risk for CKD.