Second meal effects of dietary calcium and vitamin D.

OBJECTIVE

To determine the second meal effects of calcium and vitamin D on postprandial glucose, insulin, non-esterified fatty acids (NEFA) and glycerol.

METHODS

Eight volunteers aged (mean+/-s.e.m.) 55.5+/-1.2 years and body mass index 29.0+/-1.6 kg/m(2), completed a randomized within-subject design that compared a low calcium-low vitamin D breakfast and an isocaloric high calcium-high vitamin D breakfast (HCB). Four hours following each breakfast, a very low calcium standard lunch was ingested. Serial blood collections were made on the hour over a duration of 8 h. Postprandial responses were calculated as the percentage change (Delta) from the fasting value for breakfast meals, and the 4th hour breakfast value for each lunch, respectively. Non-parametric tests of significance were employed.

RESULTS

The change in glucose, insulin, serum ionized calcium (iCa(2+)) and intact parathyroid hormone was not different between the two breakfasts, or the two lunches. However, HCB resulted in a lesser suppression of NEFA that significantly carried over to lunch (P=0.036, Wilcoxon test). A similar pattern of change in glycerol did not attain overall statistical significance. DeltaNEFA and Deltaglycerol were related at lunch (Spearman's r=0.52, P=0.04). Relative to breakfast, both lunches resulted in significantly higher glucose and insulin responses (P=0.011, Wilcoxon test).

CONCLUSIONS

The data are suggestive of second meal effects of calcium and vitamin D. Our observations of higher glucose and insulin after lunch may include the involvement of second meal factors as well.