Bone Mineral Density in Vegan Buddhist Nuns in Vietnam
In April, a cross-sectional study was published looking at the bone mineral density (BMD) of vegan, Buddhist nuns in Vietnam:
Ho-Pham LT, Nguyen PL, Le TT, Doan TA, Tran NT, Le TA, Nguyen TV. Veganism, bone mineral density, and body composition: a study in Buddhist nuns. Osteoporos Int. 2009 Apr 7. [Epub ahead of print]
The nuns were lifelong and mostly vegan (some ate some dairy). They were matched with meat-eaters from the community. Participants were 50 to 85 years old. The nuns had the same BMD as the meat-eaters, while only eating about half the calcium: 330 mg per day vs. 682 mg for the meat-eaters. The researchers reported that the osteoporosis rates in these groups were about the same as in the greater population (approximately 20%).
Cross-sectional studies are very limited in their ability to determine cause-and-effect. We do not know if there were nuns who stopped being vegan after getting osteoporosis. It seems that the researchers could have made an effort to investigate this possibility, but they didn’t report that they did.
While this was good news for these nuns, it concerns me that the take home message is that vegans only need 300 mg/day of calcium.
A more relevant study – the most important to date on vegan bone health – is a 2007 analysis from EPIC-Oxford which found that vegans had higher rates of fracture than those in other diet groups. When they adjusted for calcium intake, they found that vegans who ate 525 mg of calcium per day had the same fracture rates as the other diet groups. This was a prospective study which means they followed vegans (and other diet groups) through time, which is a better way to find associations than are cross-sectional studies. It is the only prospective study ever done on vegan bone health.
To date, the best evidence shows that vegans should get at least 525 mg of calcium per day. I recommend at least 700 mg for adults and 1,000 mg for teens.
For more detailed information on vegans, calcium, and vitamin D click here.
May 9th, 2009 at 8:25 pm
525 mg of calicum pe day is a lot lower than the USRDA. Even that amount is very hard to get from vegan food that isn’t fortified with calcium. The natural sources of vegan calcium, with a lot of calcium per calorie are leafy greens. You have to pick the high calcium and the ones with high calcium absorbability. Even then you have to eat at least 2 cooked cups a day. That is hard to do. I find that greens make me feel very full and they aren’t always easy to digest.
The reasoning I am mentioning all of this is if I wonder how much of the USRDA and the 525 mg figure is padding to compensate for high calcium foods with poor calcium absorbability.
The USRDA is between 1 – 2 grams of calcium per day depending on who you are. No doubt that is a bit higher than it needs to be because the dairy industry wants to sell milk. Even so, cows milk has only a 30% rate of absorption for calcium. If the USRDA is basing its padding on what you can actually absorb from cows milk maybe people need much less if they use sources with better absorption rates.
My problem with that idea is that I only found good listing for rates of calcium absorption in Brenda Davis “Becoming Vegetarian”. I have the feeling that the USDA has not updated its research for calcium absorption and oxalic acid in a long time.
My other problem is that many of the high calcium greens with the better absorption rates mentioned in Davis’ book are not the common ones. I am fortunate enough to have a really good Asian supermarket near me that carries some of them.
July 4th, 2009 at 5:47 am
Hi, Jack. Do you have anything to say in response to this article? It was what my meat- and dairy-loving friend presented me with at lunch the other day. A study just came out saying vegans have lower bone density. I said that’s one study. I have many more that prove I’m fine. Then I went to read the article and it doesn’t sound that bad. It says vegans’ bone density is 5% lower, but their rate of fracture is the same. But still, I don’t want lower bone density. Please let me know if you’ve seen this study/article and what you think of it.
http://www.abc.net.au/science/articles/2009/07/02/2615211.htm
August 4th, 2009 at 2:17 pm
Marty Davey, RD said this to me privately which I thought was a good point:
One thought is that the nuns probably do physical labor more than the average vegan in the EPIC study. Personally, I think Vitamin D and resistance exercise or activity does more to maintain bone health than calcium.