EFFECT OF CALCIUM SUPPLEMENT PREPARATION CONTAINING SMALL AMOUNTS OF CITRATE ON THE ABSORPTION OF ALUMINUM IN NORMAL SUBJECTS AND IN RENAL-FAILURE PATIENTS

It is well known that Al absorption is markedly enhanced by citrate. T he aim of the study was to document whether low-dose citrate ingestion (4 g/day) contained in a well-known effervescent calcium supplement w as sufficient to increase Al absorption in 16 normal volunteers and 15 subjects with stable chronic renal failure under conditions of either Ca carbonate or Al hydroxide supplementation. Serum and urine Al leve ls were measured using flameless atomic absorption spectrophotometry a s previously described. After Ca carbonate plus Ca citrate ingestion, there was no rise over baseline (Ca Carbonate alone) serum or urine Al levels in either group. Ca carbonate and Al hydroxide taken together produced a significant rise in serum and urine Al levels in both group s. Maintain Al hydroxide but substituting Ca citrate for the carbonate (same dose of elemental Ca) produced a further significant increment in serum Al (0.47+/-0.28-1.15+/-0.8 mu mol/l; p<0.001) and in urine Al (1.37+/-0.46-5.77+/-5.21 mu mol/l; p<0.001) in the chronic renal failu re group as well as in serum Al (0.42+/-0.2-0.76+/-0.48 mu mol/l; p<0. 001) and urine Al (2.70+/-1.24-8.24+/-3.96 mu mol/l; p<0.001 in the no rmal volunteer group. Due to decreased urine excretion, the increment in serum Al in the CRF group was significantly greater than in the nor mal subjects (p<0.02). Thus small quantities of citrate present in eff ervescing Ca supplements can significantly enhance intestinal Al absor ption even in normal subjects. All citrate-containing preparations are totally contra-in dicated in chronic renal failure patients ingesting Al-containing compounds. Patients themselves should be warned of the dangers.