Calcium and Stress Fractures in Adolescent Girls
From March 20, 2012:
I was wondering if you saw this study [showing that increased vitamin D intake, but not increased dairy and calcium, protected adolescent girls against stress fractures] that went around yesterday, and saw PCRM’s release on it. I only read the abstract, but didn’t see that higher intakes of calcium was correlated with higher risk of bone fracture. I was wondering what you thought about this, because I remember you referencing some studies showing that vegans have higher rates of bone fracture, and that the difference went away when the vegans had high enough intakes of calcium. Was that because they were getting the calcium from plant sources, you reckon?
Answer:
It is only one study (EPIC-Oxford, 2007) showing vegans to have a higher fracture rate, the only study measuring fracture rates in Western vegans. It showed that the category of vegans getting less than 525 mg/day of calcium had a higher fracture rate than other diet groups, but that vegans getting more calcium had the same rate.
I did see PCRM’s press release on this study and have since obtained a copy of the paper. Although not mentioned in the abstract, the study found a trend towards increased risk of stress fracture with increased calcium intakes, among girls in the high impact activity category, though the finding was not statistically significant.
These results have little bearing, one way or the other, on my recommendations that vegans get more than 525 mg/day of calcium (and preferably 700 – 1,000 mg/day). The lowest category of calcium intake was 541 mg/day. The second lowest was 825 mg/day and that category didn’t have a practically different risk compared to the lowest category. It wasn’t until the middle category of calcium intake, an average of 1,111 mg per day, that there was a strong trend towards higher risk of stress fracture (though, again, it wasn’t statistically significant).
Here are some excerpts from the paper’s discussion:
“Our findings are not consistent with those reported in a prospective study of 125 young adult female competitive distance runners, which found that higher intakes of calcium and dairy products predicted lower rates of stress fracture and that higher intakes of vitamin D, calcium, and dairy foods were all associated with significant gains in hip bone mineral density during the 2 years of follow-up.
“Our findings are supported by several studies that have found no association between dairy intake and bone health in children and adolescents. While 2 randomized trials reported a positive relationship between dairy product consumption and measures of bone health, most cross-sectional, retrospective, and prospective studies did not. A review of calcium intake, dairy product intake, and bone health found that the vast majority of controlled studies of dairy supplementation or total dietary calcium intake show that, although very low calcium intake may be harmful to bone development, increases in dairy or total dietary calcium intakes higher than 400 to 500 mg/d are not correlated with nor represent a predictor of bone mineral density or fracture rate in children or adolescents.”
The evidence appears to be mixed as to whether calcium intakes higher than 400 to 500 mg in children and adolescents is protective, harmful, or neutral. EPIC-Oxford remains the most important finding for vegans.
Reference
Sonneville KR, Gordon CM, Kocher MS, Pierce LM, Ramappa A, Field AE. Vitamin D, Calcium, and Dairy Intakes and Stress Fractures Among Female Adolescents. Arch Pediatr Adolesc Med. 2012 Mar 5. [Epub ahead of print] | link