- Mirkka Narva: Institute of Biomedicine, Pharmacology, Helsinki University, Helsinki, Finland.
BACKGROUND: Milk fermented with Lactobacillus helveticus ( L. helveticus) has been shown to lower blood pressure and to increase bone mineral content in spontaneously hypertensive rats. The effect of L.helveticus may be due to better calcium availability.
AIM OF THE STUDY: In the present study the effect of milk fermented with L. helveticus on acute changes in calcium metabolism and bone resorption in postmenopausal women was studied.
METHODS: The study was performed as a randomised double-blind crossover study of 20 postmenopausal women (mean age 65, range 50-78). The study was carried out in two parts. Firstly, L. helveticus fermented milk was compared to a control milk. Secondly, juice containing peptides formed with L. helveticus bacteria was compared to a control juice. The acute effect on calcium metabolism was measured during the study day by serum ionised calcium (iCa), parathyroid hormone (PTH), calcium (Ca), phosphate (P), and urinary calcium. A direct marker of bone turnover, carboxyterminal telopeptide of type I collagen (ICTP), was measured from the serum.
RESULTS: L. helveticus fermented milk reduced serum PTH (405.3 +/- 37 ng/l vs. 454.9 +/- 37, p = 0.012) and increased serum calcium (19.1 +/- 0.2 mmol/l vs. 18.8 +/- 0.2, p = 0.031) compared to the control milk. L. helveticus derived peptides had no significant acute effect on calcium metabolism, in fact, ionised calcium was lower and PTH higher after the juice containing peptides compared to the control juice.
CONCLUSIONS: Fermentation of milk with Lactobacillus helveticus had a positive acute effect on calcium metabolism. This effect was not explained by the small peptides formed by L. helveticus.