The following two studies were conducted by the same authors. They were published within 3 months of each other, but have different conclusions.
Veganism, Bone Mineral Density, And Body Composition: A Study In Buddhist Nuns, Osteoporosis International, April, 2009
Ho-Pham LT, Nguyen PL, Le TT, Doan TA, Tran NT, Le TA, Nguyen TV
Effect Of Vegetarian Diets On Bone Mineral Density: A Bayesian Meta-Analysis, American Journal of Clinical Nutrition, July, 2009
Lan T Ho-Pham, Nguyen D Nguyen and Tuan V Nguyen
The first study, published in April of this year, compared the bone mineral density (BMD) of:
- 105 monastery-dwelling Buddhist nuns, vegans for ~33 years
- 105 monastery-dwelling women, omnivores
- There was no significant difference between vegans and omnivores in BMD
- There was no significant difference between vegans and omnivores in lean body mass or fat mass
- There was no significant difference between vegans and omnivores in prevalence of osteoporosis
- Intake of dietary calcium was lower in vegans compared to omnivores (330 mg/day vs. 682) however, there was no significant correlation between dietary calcium and BMD.
"Although vegans have much lower intakes of dietary calcium and protein than omnivores, veganism does not have adverse effect on bone mineral density and does not alter body composition."
The second study, published in July of this year, was not an original investigation, but a meta-analysis (a review of previously-conducted studies). It included 9 observational studies that addressed the association between vegetarianism and BMD.
- Vegetarians' bones were ~5% less dense than meat-eaters.
- Vegans' bones were ~6% less dense than meat-eaters.
"The results suggest that vegetarian diets, particularly vegan diets, are associated with lower BMD, but the magnitude of the association is clinically insignificant. ... [Such that] the effect size is unlikely to result in a clinically important increase in fracture risk."
Why, after conducting and publishing a more in-depth study on veganism and bone density, including a literature review, and discovering that life-long vegans have bones essentially identical in density to meat-eaters, did these researchers hastily assemble and publish a review (a meta-analysis, a type of study prone to bias since you can cherry pick which studies to include and which statistics to run) that, lo-and-behold, found a slight decrease in BMD in vegetarians?
And why did this second study, with less clinically significant results, get more attention in the media?
I don't know. But the second study was funded by Amber Alliance of Malaysia, which owns F&B Nutrition Sdn Bhd, "a dairy products producer and wholesaler." (See Update below.)
Update, July 8: It has been brought to my attention (thank you, Mr. Nguyen) that the grant provided this study from "the AMBeR alliance" may refer to the Australian Medical Bioinformatics Resource. However, the Australian Medical Bioinformatics Resource does not on their website refer to themselves as the "AMBeR alliance."
The Australian Medical Bioinformatics Resource is affiliated with the Garvan Institute of Medical Research, which is funded by "CRC for Innovative Dairy Products."