Does it matter how and when you take calcium supplements - Minerals - Brief Article

Nutrition Research Newsletter, Oct, 2001

Recent discussion and attention has been focused on the recommended intake of dietary calcium. However, as dietary calcium has direct metabolic effects by decreasing parathyroid hormone (PTH) secretion, it is crucial to ascertain the optimal time and method of calcium dosing.

The goal of a recent investigation was to determine the acute effects of oral calcium loads on PTH secretion and on markers of bone resorption and formation. The emphasis of the investigation was to determine differences and benefits of different dosages of calcium and the timing of the dosages on calcium and bone metabolism, in order to make effective recommendations to the public. A calcium supplement widely used in Europe and found to be as absorbable as calcium carbonate was used in this investigation. Thirty young, healthy women aged 21-34 years participated in the study. The investigation was performed in three parts, each with ten participants. Study 1 was to evaluate the effect of the timing of the calcium dose. Study 2 was conducted to evaluate the effect of the size of the calcium dose and study 3 was to determine the effect of small repetitive doses on calcium and bone metabolism. Calcium was administered as a single dose of calcium slat (Calcium Sandoz: 6810 mg calcium lactate gluconate, 300 mg calcium carbonate, 1350 mg acid citrate anhydrous, and 40 mg aspartame; Laboratories Sandoz, Sari, France) in water with a sma41, standardized meal. The calcium and phosphorus intakes from the meal were kept as low as possible. All of the meals combined were calculated to provide 375 m Ca and 878 mg P daily in study 1,100 mg Ca and 365 mg P daily in study 2, and 200 mg Ca and 803 mg P daily in study 3.

In study 1, subjects took part in two morning and two night sessions. Calcium doses were 0 or 25 mg/kg body weight. In study 2, subjects took part in three sessions: a control session (water), a session in which they received a 250-mg Ca load with water, and a session in which they received a 1000-mg Ca load with water. In study 3, subjects took part in two sessions. In addition to the meals, the subjects were given either water Or 800 mg Ca divided into four 200-mg doses spaced evenly throughout the day. Serum intact PTH concentrations were measured along with serum osteocalcin concentrations. Serum concentrations of the carboxy terminal propeptide of collagen type I procollagen (PICP), a marker of bone collagen formation, and cross-linked telopeptide of type I collagen (ICTP), a marker of bone resorption, were measured. Serum total calcium, serum phosphate, urinary calcium, urinary phosphate, and urinary creatinine concentrations were measured by using routine laboratory methods.

Investigators found no significant difference in the response of serum PTH to the calcium load taken either in the morning or in the evening. There was a significant dose-response effect observed of the calcium load on serum ionized calcium and serum PTH. Small calcium doses given throughout the day kept the PTH secretion at a lower level than during the control day. None of the doses were found to cause significant changes in the markers of bone formation and resorption measured. Because investigators did not see any significant effect of the timing of the dose or the amount of the dose of calcium on the bone markers evaluated, they are unable to make any definite conclusions regarding which regimen is best for bone health. Further, long-term studies are needed for recommendations to be formulated upon.

M. Karkkainen, C. Lanberg-Allardt, S. Ahonen, et al. Does it make a difference how and when you take your calcium? The acute effects of calcium on calcium and bone metabolism. Am J Clin Nutr; 74:335-342 (September 2001) [Correspondence: C.J.E Lanberg-Allardt, Dept. of Applied Chemistry and Microbiology, Calcium Research Unit, University of Helsinki, PO Box 27, FIN-00014 Helsinki, Finland E-mail: christel.lamberg-allardt@helsinki.fi].