Postprandial metabolic responses to milk enriched with milk calcium are different from responses to milk enriched with calcium carbonate.

The purpose of this study was to assess whether there are any differences in postprandial physiological responses to skim milk powder enriched with milk calcium (SMP + milk calcium) and skim milk powder enriched with calcium carbonate (SMP + CaCO3), with each of the milks providing 1200 mg calcium. This was a randomised, controlled, crossover study involving 16 men and 29 women over 55 years of age. Measurements of calcium and bone metabolism were taken after an overnight fast before each drink, and postprandially every hour for 8 h. The impact of time and drink on the responses was analysed by repeated measures of analysis of variance. Serum calcium was significantly higher between 2 and 8 h after consumption of SMP + CaCO3 compared with SMP + milk calcium (P < 0.0001). Serum phosphate was significantly higher between 2 and 5 h after drinking the SMP + milk calcium compared with SMP + CaCO3 (P < 0.0001). The level of parathyroid hormone (PTH) was virtually unchanged after consumption of SMP + milk calcium, but decreased between 1 and 4 h after SMP + CaCO3 (P = 0.02). The serum C-telopeptide level, a marker of bone resorption, was significantly lower after SMP + CaCO3, compared with SMP + milk calcium, between 4 and 8 h after drinking the milk (P < 0.05). We conclude that serum calcium levels have a higher increase after SMP + CaCO3 consumption than after SMP + milk calcium consumption, and that this is associated with lower serum PTH concentrations and a more prolonged postprandial decrease in bone resorption.

Impact of supplementary high calcium milk with additional magnesium on parathyroid hormone and biochemical markers of bone turnover in postmenopausal women.

The aim of this study was to investigate the impact of magnesium-enriched, high-calcium milk on serum parathyroid hormone (PTH) and biochemical markers of bone turnover in postmenopausal women. We recruited 50 healthy postmenopausal women to take part in this randomised controlled study. Half of the women consumed two serves of high-calcium skim milk enriched with magnesium (milk group) and half consumed two serves apple drink per day (apple group), each for 4 weeks. The milk provided 1200 mg calcium and an additional 106 mg magnesium. We investigated the responses of serum PTH, as well as the serum and urinary calcium, magnesium and biochemical markers of bone turnover. There was no effect of time or drink on the clinical biochemistry, serum PTH or urine markers of bone resorption (free deoxypyridinoline and N-telopeptides). Serum C-telopeptides (CTX), another marker of bone resorption, did not change with time in the apple group. However, in the milk group, serum CTX deceased significantly from 0.43 +/- 0.04 ng/mL to 0.32 +/- 0.02 at 2 weeks (p < 0.0001) and 0.28 +/- 0.02 at 4 weeks (p < 0.0001). In the milk group, urinary calcium and magnesium each increased during the night but not during the day. Overall, these data suggest that milk has an antiresorptive effect on bone, but that this is not accompanied by measurable changes in serum PTH.

High intake, but not low intake, of CLA impairs weight gain in growing mice.

CLA has a range of biological properties, including effects on lipid metabolism and body composition in experimental animals. The prevalent isomer of CLA found in the human diet is 9c,11 t-CLA, and it is predominantly found in products containing fat from ruminant animals. This study investigated the effect of dietary CLA on energy balance in mice. Synthetic CLA reduced body fat in growing male BALB/c mice in a dose-dependent manner over the range 0.25-1.0% w/w CLA in the diet. Weight gain was also reduced at the highest levels of dietary CLA, being only 5.88 +/- 2.68 g/4 mice (mean +/- 1 SD) after 4 wk of 2.0% CLA in the diet, compared with weight gains of 7.51 +/- 2.22 to 8.17 +/- 2.34 g/4 mice in the 0-0.5% CLA groups. There was no significant effect on weight gain if diets contained 0.5% synthetic CLA or less. These results suggest that high levels of a synthetic mixture of CLA isomers modify energy metabolism and body composition and that high levels of synthetic CLA impair weight gain and reduce body fat pad mass in growing mice.

Assessment of a rapid method for assessing adequacy of calcium intake.

The purpose of this study was to assess the agreement between the 24 h diet recall and a short 17-item 24 h food intake recall in assessing calcium intake. The calcium intakes of 21 women over the age of 50 were assessed by both methods on four occasions. The mean calcium intakes were similar using both methods, being 1034+/-398 mg/day by 24 h diet recall and 822+/-412 mg/day (SD) by 17-item 24 h food intake recall. The 17-item 24 h food intake recall tended to underestimate calcium intake compared with the 24 h diet recall, with the limits of agreement being between -1197 and -727 below and 370 and 682 mg/day above 24 h diet recall values over the four assessments. The 17-item 24 h food intake recall identified 8% more women with inadequate calcium intakes than the 24 h diet recall method did. Although there is poor agreement in calcium intake between the 24 h diet recall method and the 17-item 24 h food intake recall, the latter provides a quick and simple means for assessing extremes of calcium intake and whether day to day calcium intake is adequate.

Impact of ambulatory blood pressure monitoring on daily activity.

We evaluated the impact of wearing an ambulatory blood pressure (ABP) monitor on the usual daily activity of 16 healthy men and women. Daily ABP and heart rate (HR) were recorded on 2 days using the DynaPulse 5000 A system. Daily HR and activity were recorded on two further days using a dedicated HR monitoring system. All four sets of measurements were made for 8 h during which time the volunteers kept a simultaneous diary record of their physical activity. There was no detectable difference in physical activity records on any day. Mean daily HR was lower during ABP monitoring than during the dedicated HR monitoring carried out on different occasions (73+/-7 versus 81+/-7 beats min(-1), P<0.001). The lower mean HR observed during ABP monitoring compared with dedicated HR monitoring may reflect subtle differences in the physical behaviour of subjects being monitored, which could not be detected from the diary records.