Short Term Intake of Undaria pinnatifida Does Not Affect Bone Biomarkers in Young Korean Women with Low Calcium Intake

Calcium intake is essential for bone health, but young Korean women have low calcium intakes. Seaweeds have high calcium content, which may affect calcium metabolism. Twenty nine females aged 18–39 years with low calcium intake (< 400 mg/day) participated in a 19-day open-label randomized controlled trial. During the first five days, participants adhered to a controlled-feeding protocol followed by a two-week supplementation period in free-living conditions. The treatment group (n = 14) received an additional 200 mg Ca/day through Undaria pinnatifida and Porphyra in meals during the controlled-feeding period, and as U. pinnatifida noodles during days 6–19. Mineral intake (Ca, P, Mg, Na, and K) was assessed from diet composites and three 24-hour recalls during the controlled-feeding and free-living periods, respectively. Fasting serum levels of calcium, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D (1,25[OH]D), phosphorus, parathyroid hormone (PTH), and alkaline phosphatase (ALP) were assessed at baseline, day 6, and day 19. Statistical analyses were performed by Student's t-test and mixed ANOVA. Mean intakes of all minerals during days 1–5 and mean Ca and Mg intakes during days 6–19 were greater in the treatment group compared to the control group. No group effect or group and time interaction was observed in serum biomarkers. Serum 1,25(OH)D increased while PTH and ALP tended to decrease on day 6 but returned to baseline values on day 20. Short-term intake of U. pinnatifida and Porphyra does not affect calcium metabolism in young Korean women with low calcium intakes. TRIAL REGISTRATION: Clinical Research Information Service Identifier: KCT0003307