Location: Obesity and Metabolism ResearchTitle: Is bone equally responsive to calcium and vitamins D intake from food vs. supplements? Use of 41Ca tracer kinetic model Author
|Rogers, Tara - University Of California|
|Demmer, Elieke - University Of California|
|Richardson, Christine - University Of California|
|Buchholz, Bruce - Lawrence Livermore National Laboratory|
|Hillegonds, Darren - Lawrence Livermore National Laboratory|
|Van Loan, Marta|
Submitted to: Bone Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2016
Publication Date: 5/6/2016
Citation: Rogers, T.S., Demmer, E., Richardson, C., Gertz, E.R., Buchholz, B., Hillegonds, D., Garrod, M.G., Van Loan, M.D. 2016. Is bone equally responsive to calcium and vitamins D intake from food vs. supplements? Use of 41Ca tracer kinetic model. Bone Reports. 5:117-123. doi: 10.1016/j.bonr.2016.05.001.
Interpretive Summary: Fifty percent of women over the age of 50 years and 25% of men will experience an osteoporosis fracture in their life time accounting for two million broken bones and $19 billion in related costs every year. By 2025, experts predict that osteoporosis will be responsible for approximately three million fractures and $25.3 billion in health care related costs each year. Interventions that focus on lifestyle changes like improved dietary intake and exercise can be beneficial. Therefore, we conducted a study with early postmenopausal women who participated in two experiments one experiment included 4 servings/day of milk and yogurt and the second experiment had an equal amount of calcium and vitamin D, but from supplements. To monitor the improvement in calcium metabolism the women consumed a rare calcium isotope, 41Ca, which incorporates into the skeleton and is excreted in urine when changes occur in calcium intake. The 41Ca method is so sensitive that changes in calcium metabolism can be observed in short periods of time, e.g. in just weeks compared to changes from bone density test which require a longer period of time from 9 to 12 months –to observe changes. Our results demonstrated that both dairy foods and calcium and vitamin D supplements reduced the amount of calcium lost in urine within 1 week of increased calcium and vitamin D intake. The lower level of urinary calcium excretion was maintained for the 6 week duration on the interventions. Withdrawal of the increased calcium and vitamin D intake resulted in greater urinary loss of calcium also within 1 week on lower calcium and vitamin D intakes. These results suggest that the surface of the bone may serve as a reservoir of easily available calcium for release when calcium intake is low and as a repository when intakes are increased. More research is needed, however, to determine how long it takes for increased calcium and vitamin D intakes to actually result in calcium transfer into the skeleton.
Technical Abstract: Background: Few interventions directly compare equivalent calcium and vitamin D from dairy vs. supplements on the same bone outcomes. The radioisotope calcium-41 (41Ca) holds promise as a tracer method to directly measure changes in bone resorption with differing dietary interventions. Objective: Using 41Ca tracer methodology, determine if 4 servings/d of dairy foods reduces calcium excretion more than an equivalent amount of calcium and vitamin D from supplements. Secondary objective was to evaluate the time course for the change in calcium excretion. Methods: In this crossover trial, postmenopausal women (n=12) were dosed orally with 100nCi of 41Ca and received dairy (4 servings/d of milk or yogurt; ~1300 mg calcium, 400 IU cholecalciferol (vitamin D3/d) or supplement treatments (1200 mg calcium carbonate/d and 400 IU vitamin D3/d) in random order. Treatments lasted 6 wks separated by a 6 wk washout (WO). Calcium was extracted from weekly 24 hr urine collections; accelerator mass spectrometry (AMS) was used to determine the 41/40Ca ratio. Primary outcome was change in 41/40Ca excretion. Secondary outcome was the time course for change in 41Ca excretion during intervention and WO periods. Results: The 41/40Ca ratio decreased significantly over time during both treatments; there was no difference between treatments. Both treatments demonstrated a significant reduction in 41Ca excretion within one wk (p = 0.0007 and p < 0.001 for dairy and supplements, respectively). WO demonstrated a significant increase (p = 0.0024) in 41Ca excretion within 1 wk; back to pre-intervention levels. In conclusion, these data suggest that changes in urinary Ca excretion with increases or decreases in Ca intake occur within 1 wk; most likely via the miscible pool to maintain Ca homeostasis.