Your Health: Vegan diets are a bone of contention

By Kim Painter, USA TODAY

 

Are vegan diets bad to the bone?

 

There's no reason they have to be. But "it's a question that comes up a lot" as more people consider a diet free of all animal products, including the dairy foods that are part of other vegetarian diets, says Virginia Messina, a vegan and registered dietitian in Bellingham, Wash.

And it's a question that made for some confusing headlines recently. Just as the American Dietetic Association declared that "appropriately planned" vegetarian and vegan diets could be healthful at all stages of life, researchers in Australia and Vietnam reported that vegetarians and especially vegans had less dense bones than omnivores.

The bone study got much more attention than the ADA's position paper, despite the fact that the researchers found no proof that the modest bone differences would translate into more fractures.

Picking the right foods

It was another frustrating example of mainstream "bias against the nutritional benefits of a vegan diet," Messina wrote in a blog post. Yet she and other experts concede that there is reason to be concerned about the bones of some vegans, especially still-growing teens. It's not that vegans can't get enough bone-building calcium in their diets. With enough leafy green vegetables, nuts, beans and fortified foods ranging from tofu to orange juice, vegans can get recommended amounts (1,300 milligrams daily for teens, 1,000 mg for adults under age 50 and 1,200 mg for older adults).

"But there is evidence that a greater number of vegans have low calcium intakes," says Messina, who helped write previous ADA position papers.

Those vegans may well pay a price in broken bones, says Reed Mangels, a vegan registered dietitian who helped write the new ADA report. In a study of bone fracture risk, vegans in the United Kingdom did break significantly more bones than omnivores or vegetarians if they also consumed less than 500 mg of calcium a day, she says.

It's not clear how many vegans are that low on calcium. Vegans remain a small, little-studied group: 1.3% of adults reported vegan diets in a survey this spring by Harris Interactive; 3% reported vegetarian diets — they never eat meat, poultry or seafood but might eat eggs and dairy products.

Less protein shouldn't mean less calcium

One common belief among vegans is that they need less calcium because they eat less protein, and high-protein diets are known to speed up bone loss. But Mangels says: "Even if you are eating a relatively low amount of protein, you still need calcium to build strong bones." Vitamin D, which most Americans get from fortified milk, also is crucial and is in many products acceptable to vegans.

Of course, many omnivores don't get enough calcium or vitamin D either, says Felicia Cosman, clinical director of the National Osteoporosis Foundation. Dairy products are great sources of both nutrients, she adds, but other foods and supplements are just fine. Exercise, body size and genetics also play roles in bone health, she notes.

While vegans might need to think a bit more about calcium and vitamin D sources, they've got fiber, fruits and vegetables covered and can reap many health benefits, Messina says. "I think that most people really just don't understand that all diets have strengths and weaknesses."