Effect of calcium derived from lithothamnion sp. on markers of calcium metabolism in premenopausal women

A double-blind crossover pilot trial tested the hypothesis that botanically derived calcium could demonstrate greater influence over calcium metabolism markers compared with a nonplant-derived calcium carbonate supplement or placebo. Twelve fasting female subjects received a single oral dose of Aquamin F™ (derived from the marine algal Lithothamnion sp.), or calcium carbonate, or placebo. Blood and urine samples were collected at baseline and over 12 h to evaluate ionized and total calcium and parathyroid hormone (PTH). Subjects treated with Aquamin F demonstrated significantly greater urinary clearance of calcium after 12 h compared with placebo (P = .004). Following a meal at 90 min, subjects treated with Aquamin F demonstrated a more prolonged suppression of serum PTH concentration (significantly lower than placebo at 90, 120, and 240 min). Calcium carbonate provided an intermediate response; urinary clearance was not significantly different from placebo treatment and PTH was only significantly lower than placebo at 90 min. Aquamin F may demonstrate greater influence over these markers of calcium metabolism than calcium carbonate or placebo, as suggested by a greater calciuric response and a more prolonged suppression of serum PTH concentrations following a meal in premenopausal women.