Calcium Part 1—Basics 2


by Jack Norris, RD

More Information on Calcium

Contents

Vegans and Calcium Intake

Americans are regularly being urged to consume more calcium in order to prevent osteoporosis, but it’s practically impossible to meet the recommendations without large amounts of dairy, calcium-fortified foods, or supplements. Because vegans don’t eat dairy products, without fortified foods or supplements their calcium intakes tend to be low (about 400–600 mg per day compared to the U.S. recommended intake of 1,000 mg per day for adults aged 19–50 years).

During the 1990s, the vegan community responded to our lower calcium intakes by promoting the idea that osteoporosis is a disease of calcium loss from the bones rather than a lack of calcium in the diet. This view was based on research showing that there are more hip fractures in countries with higher dairy product intake and research showing that animal protein causes an increase in calcium loss through the urine. Therefore—the thinking went—calcium intake isn’t important for preventing osteoporosis and vegans are protected due to the lack of animal protein in their diets.

But both of these ideas have turned out to be misleading.

Further research showed that between countries, hip fractures are more indicative of the risk of falling than of osteoporosis. A recent study from Hong Kong found that while men and women in Hong Kong had lower rates of hip fractures, they had higher rates of vertebral fractures, and the women had higher rates of osteoporosis than Caucasian women.

As for protein leaching calcium from bones into the urine—the studies showing this used protein isolates whereas eating protein from whole foods does not result in a calcium imbalance. Population studies and clinical trials show that protein, including animal protein, doesn’t have a negative effect on bones.

So where does it leave vegans?

Vegans and Bone Health

Bone mineral density, a measure of osteoporosis, has been shown in many studies to be slightly lower in vegans than non-vegans. More importantly, two studies on Western vegans measuring fracture rates over time found that vegans had higher rates.

In the more thorough of the two studies, one from Oxford, vegans eating less than 525 mg of calcium per day had a higher fracture rate than vegans eating more than 525 mg. The vegans in the higher calcium intake group had the same fracture rates as the meat-eaters and lacto-ovo vegetarians.

This indicates that if vegans eat enough calcium they should be at no higher risk for fractures than meat-eaters.

Plant Sources of Calcium

High-calcium, lower-oxalate, dark leafy greens are the best sources of calcium for vegans—turnip greens, mustard greens, kale, bok choy, and collard greens. In addition to calcium, greens also contain vitamin K, potassium, and magnesium, which contribute to better bone health.

While spinach, Swiss chard, and beet greens are high in calcium, the calcium isn’t well absorbed due to their high content of oxalate, which binds calcium and prevents absorption from the digestive tract.

Other sources of calcium are fortified drinks, calcium-set tofu, oranges, figs, and supplements.

It’s safe for vegans to take 500 mg of calcium per day or less if you aren’t getting large amounts of calcium from other sources. Research is mixed about whether calcium intakes above 1,400 mg per day can put people at risk for chronic disease.

Please see Daily Needs for our most up-to-date calcium recommendations.


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2 thoughts on “Calcium Part 1—Basics

  • Robert Bessen

    “Low-oxalate, dark leafy greens are the best sources of calcium for vegans—collard greens”

    My sources indicate that collard greens are not a low oxalate food…..that they contain almost half as much oxalate as spinach, which is an extremely high oxalate food.

    My source is the USDA: https://www.ars.usda.gov/northeast-area/beltsville-md-bhnrc/beltsville-human-nutrition-research-center/nutrient-data-laboratory/docs/oxalic-acid-content-of-selected-vegetables/

    Oxalic Acid Content of Selected Vegetables

    Appreciate your comments on this

    • JackNorrisRD Post author

      Robert,

      > “Low-oxalate, dark leafy greens are the best sources of calcium for vegans—collard greens”

      In the article Calcium–Part 2: Research, I separate collards from those other greens, and I shouldn’t have listed it first on this page. I’ve changed the statement to:

      High-calcium, lower-oxalate, dark leafy greens are the best sources of calcium for vegans—turnip greens, mustard greens, kale, bok choy, and collard greens.

      > My sources indicate that collard greens are not a low oxalate food

      I agree that as foods go, collards are not a low-oxalate food and if you’re following a low-oxalate diet, they might not be a good choice. I got my oxalate number for raw collards from a table Harvard published in 2007 as distinct from the USDA’s table which was published in 1984. I was also checking my numbers against another table of oxalate content that I couldn’t completely verify the source for (and thus didn’t cite) and it listed numbers on the lower end for collards. That said, I don’t know for sure which table is more accurate and the USDA’s info is, I agree, significantly higher.

      In reviewing the number just now, I saw that I listed boiled, drained collards as having 5 mg of oxalate per 1/2 cup and cited the Harvard table although that table doesn’t list boiled, drained collards. I’m not sure where I got that number so I’ve removed it. I’m sorry for that mistake.

      To sum up my view, I think collards are a decent source of calcium for vegans, but I wouldn’t promote them as a food for people trying to minimize their oxalate intake.