Dietary calcium intake does not meet the nutritional requirements of children with chronic kidney disease and on dialysis

BACKGROUND: Adequate calcium (Ca) intake is required for bone mineralization in children. We assessed Ca intake from diet and medications in children with CKD stages 4–5 and on dialysis (CKD4–5D) and age-matched controls, comparing with the UK Reference Nutrient Intake (RNI) and international recommendations. METHODS: Three-day prospective diet diaries were recorded in 23 children with CKD4–5, 23 with CKD5D, and 27 controls. Doses of phosphate (P) binders and Ca supplements were recorded. RESULTS: Median dietary Ca intake in CKD4–5D was 480 (interquartile range (IQR) 300–621) vs 724 (IQR 575–852) mg/day in controls (p = 0.00002), providing 81% vs 108% RNI (p = 0.002). Seventy-six percent of patients received < 100% RNI. In CKD4–5D, 40% dietary Ca was provided from dairy foods vs 56% in controls. Eighty percent of CKD4–5D children were prescribed Ca-based P-binders, 15% Ca supplements, and 9% both medications, increasing median daily Ca intake to 1145 (IQR 665–1649) mg/day; 177% RNI. Considering the total daily Ca intake from diet and medications, 15% received < 100% RNI, 44% 100–200% RNI, and 41% > 200% RNI. Three children (6%) exceeded the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) upper limit of 2500 mg/day. None with a total Ca intake < RNI was hypocalcemic, and only one having > 2 × RNI was hypercalcemic. CONCLUSIONS: Seventy-six percent of children with CKD4–5D had a dietary Ca intake < 100% RNI. Restriction of dairy foods as part of a P-controlled diet limits Ca intake. Additional Ca from medications is required to meet the KDOQI guideline of 100–200% normal recommended Ca intake. [Figure: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00467-020-04571-x) contains supplementary material, which is available to authorized users.