Vegetarian diet weakens bones according to journalist, but not researchers

It's raining so I can't go out dumpster diving. And I haven't found any new veg specific info in a while. But a friend recently sent me this email:

"I found this article which says that vegans have weaker bones than omnis/ovolactoveggies. Is it true?"

The article on Google News has the misleading headline "Vegetarian diet 'weakens bones'". It tells of a study which found "practically no difference" between the bone mineral density (BMD) of meat eaters and vegetarians who consume eggs and dairy. However, vegans seemed to have lower BMD than the others. But then, lead researcher Tuan Nguyen said "but the magnitude of the association is clinically insignificant."

Hmmm, clinically insignificant. Doesn't really match the headline, does it?

This study is a meta analysis, where instead of conducting research on a single sample group the researchers pool data from several different studies to create a big picture from these different populations. However the relationship is too weak to say that it is the result of diet, and of course the diets are categorised in the overly simplified manner of "meat eater, vegetarian, vegan" etc which is the flaw common to most nutritional research.

However the comments the authors make in their discussion are very interesting:
"BMD is a complex trait, in the sense that it is affected by multiple environmental and genetic factors. It is therefore unrealistic to expect that any single modification, including dietary change, can result in a significant change in the trait. The complexity and possible interaction between dietary calcium and protein makes it difficult to attribute the modest effect of vegetarianism on bone density to either dietary factor.

All studies included in this analysis were observational; therefore, no cause and effect relation between vegetarian diets and BMD can be drawn from the finding."

So... I wonder what Dr Nguyen thought when he saw the headline?

Source: Lan T Ho-Pham, Nguyen D Nguyen, and Tuan V Nguyen (2009). Effect of vegetarian diets on bone mineral density: a Bayesian meta-analysis. Am J Clin Nutr 90:943–50.