The Fall 2009 issue of Vegetarian Voice magazine, the newsletter of the North American Vegetarian Society, has an article by Amy Joy Lanou and Michael Castleman, “A Whole Diet Approach to Building Better Bones.”
I will quote from the article to sum up their arguments:
“[W]e have known for at least 20 years that fracture rates are highest in areas where dairy and calcium consumption are also the highest.”
“Research shows that a low-acid diet, one that is high in fruits and vegetables and devoid of (or low in) animal protein (meats, poultry, fish, milk, eggs and cheese) helps keep calcium in bones.”
“[Osteoporosis is] actually a disease of calcium imbalance. Drinking milk and eating dairy foods provides calcium – but these foods are so high in protein that they draw more calcium out of bone then they replace.”
“We do need some calcium. The World Health Organization recommends 400 to 500 mg/day for people in countries at high risk of osteoporosis.”
“The best approach to osteoporosis prevention – the only one that makes scientific sense – is a diet very low in or devoid of animal foods and high in fruits and vegetables, combined with walking or equivalent exercise for 30 to 60 minutes a day, every day.”
If you have been following vegan nutrition advocacy for the past two decades, nothing above should be new to you. And here are the major problems I have with it:
1. Most non-vegans in Western countries get around 800 to 1200 mg of calcium per day. At this level of intake, I agree that there is little evidence that to prevent osteoporosis one needs even more calcium. However, Lanou and Castleman imply that all you need is a vegan diet containing 400 – 500 mg of calcium per day and walking for 30 to 60 minutes for strong bones. And they leave out the most important study published to date on bone health and vegans, a 2007 report from the EPIC-Oxford study which showed that vegans had a 30% higher rate of bone fractures than did meat-eaters and lacto-ovo vegetarians!
In that study, the vegans who got more than 525 mg of calcium had the same rate of bone fractures as the meat-eaters and lacto-ovo vegetarians, showing that vegans need more than 525 mg of calcium. (In the study, 32% of vegans had calcium intakes between 525 and 699 mg per day, and 24% had greater than 699 mg per day.)
This is the only study looking at the bone fracture rates of vegans.
2. Lanou and Castleman base most of their argument on the idea that animal protein leeches calcium from the bones. As I posted a few weeks ago, a meta-analysis looking at bone health and fractures found that “Overall, the weight of the evidence shows that the effect of dietary protein [including animal protein] on the skeleton appears to be favorable to a small extent or, at least, is not detrimental.”
In my opinion, the argument that a primary cause of osteoporosis is animal protein has always been on shaky ground.
3. Lanou and Castleman leave vitamin D out of their final recommendations (they briefly mention you can get it from the sun earlier in the article). Vitamin D can be a significant problem for many vegans and needs to be addressed in discussions of bone health.
4. I do not see why it is necessary to make an argument that people only need 400 to 500 mg of calcium per day, when the evidence is so lacking (and actually points in the other direction). What harm could come from encouraging vegans to get at least the low end of what is a normal amount of calcium (like 700 to 800 mg/day) in Western countries? None. But what harm could come from vegans not getting that much? Only osteoporosis!
In summary, there is no direct evidence that a vegan diet with only 400 to 500 mg of calcium per day prevents osteoporosis. The direct evidence is just the opposite.
More info on vegan diets and bone health.
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