Dietitian Perspectives on Protein, Calcium and Vegan Bone Health

Note: this article is co-authored by Jack Norris, RD and Ginny Messina, MPH, RD and appears on Ginny’s blog as well as this one.

Vegans typically have lower calcium intakes than other vegetarians and meat-eaters. But just how much does this matter?

The popular thinking has long been that it doesn’t matter much at all. According to the acid-ash hypothesis of osteoporosis, vegans experience smaller calcium losses since we don’t eat animal protein. The theory is that calcium is “leached” from bones to counter acidic conditions caused by animal protein.

It’s supported by studies that find higher levels of both calcium and acidic compounds in the urine when people are fed big doses of animal protein (1). This is also supposedly why hip fracture rates are higher in countries with high animal protein intakes (2).

But while the theory had great support several decades ago, it hasn’t held up to the scientific evidence. An article by vegan dietitian Dr. Reed Mangels, based on a presentation she gave at the Sixth International Congress on Vegetarian Nutrition sums up the more recent research very well (3). It should be required reading for all vegan and vegetarian nutrition professionals.

Unfortunately, a quick Google search of “vegan-calcium-bone-health” shows that many vegan educators, including some who are health professionals, are still promoting the idea that protein causes calcium loss from bones.

We thought it would be interesting to see where vegetarian dietitians fit into all of this. So, we created a true/false questionnaire about bone health, protein and vegan diets. We asked dietitians who subscribe to the email list for the Vegetarian Nutrition Dietetic Practice Group (VNDPG) to answer the questions.

Although this was a small, unscientific survey, the results were interesting. They showed that VNDPG members were more aware of the issues than the general vegan community and are sharing better information than what is often available on the internet and elsewhere. But in some cases, even RDs weren’t aware of the newer research on protein and bone health.

Here is the survey with our answers.

1. Protein contributes to bone structure. TRUE

Most RDs got this one right. Bone contains collagen and other proteins and you can’t build and maintain bones without protein (4).

2. Protein from animal foods causes calcium loss from bones. Probably FALSE

According to a 2009 meta-analysis of epidemiological studies, protein is not harmful to bone health and may be beneficial (5). Particularly relevant to vegetarians, in the Adventist Health Study-2, vegetarians who ate the most protein-rich foods like legumes and veggie meats, had the fewest fractures (6). It’s true that studies link higher protein intake with higher urinary calcium losses. But this is in response to eating isolated proteins, not protein-rich foods (7). The phosphorus in those higher-protein foods seems to cancel out the effect on bone loss. Protein also improves calcium absorption when calcium intakes are low (8), so it’s possible that the higher amounts of calcium in the urine simply reflect that greater amounts being absorbed from the diet.

In fact, another 2009 meta-analysis—this one looked at clinical studies—found that the amount of calcium lost in the urine didn’t correlate with calcium balance in the body or with markers of bone health (9). That is, acidic conditions didn’t produce a net loss of calcium from the bones.

The studies comparing hip fracture rates among countries have also been called into question. Since they’re ecological studies, they don’t control for anything and are only marginally useful.

Better information comes from The Hong Kong Osteoporosis Study. This research found that hip fracture rates were lower in Hong Kong than Sweden but that spinal fracture rates were higher (10). And while that seems conflicting, it’s really not. Hip fracture rates are affected less by bone health and more by the likelihood of falling. Spinal fractures, on the other hand, actually reflect bone health. In fact, the researchers said that despite lower hip fracture rates, the Hong Kong women had more osteoporosis.

3. Drinking cow’s milk promotes osteoporosis. Probably FALSE but maybe TRUE

Given the discussion above, it doesn’t seem that the protein in milk would raise risk for osteoporosis. But, research published just last week did raise questions about the effects of milk-drinking on bone health.

The Swedish researchers found that women who drank more than 3 glasses of milk per day had a much higher rate of fracture than those who drank less than a serving (11). In contrast, though, they found that cheese and yogurt were associated with lower rates of fracture. Earlier research in Adventists also found a protective effect of cheese on bone health (12).

One possible explanation, according to the Swedish researchers, is that the sugar galactose—high in milk, but low in cheese and yogurt—is the factor affecting fractures. The research supporting this is in animals, though.

Although it would be premature to say that milk raises fracture risk, there isn’t much evidence that milk-drinkers have any particular health advantage, either. Since we oppose dairy consumption on ethical grounds, it seems like it’s enough to know that nobody actually needs dairy foods in their diet.

4. Research shows that vegans have fewer bone fractures than meat-eaters. FALSE

What evidence we have for this — and admittedly, it’s very little — isn’t especially favorable for vegans. In the EPIC-Oxford study, vegans had a 30% higher risk for fracture after adjusting for numerous variables like age, smoking, alcohol consumption, and physical activity. After adjusting for calcium intake, however, there was no difference in fracture rates. Vegans who got enough calcium were no more likely to break a bone than milk-drinkers (13).

Likewise, in the Adventist Health Study-2, there was a trend toward higher fracture rates among the vegans compared to other vegetarians as well as non-vegetarians (6). (This study didn’t test for statistical significance.)

5. People eating plant-based diets have lower calcium needs than meat-eaters. Probably FALSE

If protein doesn’t have a negative effect on bone health, then there is no reason to think that vegans have lower calcium needs. The EPIC-Oxford study mentioned above suggests that the lower calcium intakes that are typical of vegans may be harmful.

6. The US RDAs for calcium are similar to the World Health Recommendations. TRUE

A common belief is that the WHO recommends just 400 to 500 milligrams of calcium per day. But, the WHO recommends 1000 mg of calcium for adults which is the same as the US RDAs.

Two last questions on our survey looked at the more holistic story of diet and bone health.

7. Weight-bearing exercise is important for bone health TRUE

8. A variety of nutrients including vitamin D, potassium, magnesium, and calcium is needed for healthy bones. TRUE

No surprise that 100% of our respondents knew that bone health is about much more than calcium. No single nutrient or food can make or break the strength of your bones. Keeping bones strong takes a whole diet and lifestyle approach. Getting enough calcium is just one part of that, but it is still an important part. Right now, there is no reason to think that vegans have any particular advantage where this is concerned.

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References

1. Schuette SA, Linkswiler HM. Effects on Ca and P metabolism in humans by adding meat, meat plus milk, or purified proteins plus Ca and P to a low protein diet. J Nutr 1982;112:338-49.

2. Frassetto LA, Todd KM, Morris RC, Jr., Sebastian A. Worldwide incidence of hip fracture in elderly women: relation to consumption of animal and vegetable foods. J Gerontol A Biol Sci Med Sci 2000;55:M585-92.

3. Mangels AR. Bone nutrients for vegetarians. Am J Clin Nutr 2014;100:469S-475S.

4. Boskey AL, Coleman R. Aging and bone. J Dent Res 2010;89:1333-48.

5. Darling AL, Millward DJ, Torgerson DJ, Hewitt CE, Lanham-New SA. Dietary protein and bone health: a systematic review and meta-analysis. Am J Clin Nutr 2009.

6. Lousuebsakul-Matthews V, Thorpe DL, Knutsen R, Beeson WL, Fraser GE, Knutsen SF. Legumes and meat analogues consumption are associated with hip fracture risk independently of meat intake among Caucasian men and women: the Adventist Health Study-2. Public Health Nutr 2013:1-11.

7. Spencer H, Kramer L, DeBartolo M, Norris C, Osis D. Further studies of the effect of a high protein diet as meat on calcium metabolism. Am J Clin Nutr 1983;37:924-9.

8. Kerstetter JE, O’Brien KO, Insogna KL. Dietary protein affects intestinal calcium absorption. Am J Clin Nutr 1998;68:859-65.

9. Fenton TR, Lyon AW, Eliasziw M, Tough SC, Hanley DA. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res 2009;24:1835-40.

10. Bow CH, Cheung E, Cheung CL, Xiao SM, Loong C, Soong C, Tan KC, Luckey MM, Cauley JA, Fujiwara S, et al. Ethnic difference of clinical vertebral fracture risk. Osteoporos Int 2012;23:879-85.

11. Michaelsson K, Wolk A, Langenskiold S, Basu S, Warensjo Lemming E, Melhus H, Byberg L. Milk intake and risk of mortality and fractures in women and men: cohort studies. Bmj 2014;349:g6015.

12. Matthews VL, Knutsen SF, Beeson WL, Fraser GE. Soy milk and dairy consumption is independently associated with ultrasound attenuation of the heel bone among postmenopausal women: the Adventist Health Study-2. Nutr Res 2011;31:766-75.

13. Appleby P, Roddam A, Allen N, Key T. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr 2007;61:1400-6.

18 Responses to “Dietitian Perspectives on Protein, Calcium and Vegan Bone Health”

  1. Dima Says:

    Thank you for this review!!

  2. Catherine Turley Says:

    i’m very interested in this subject because i am a vegan with low calcium which has actually resulted in calcium deposits in my breasts. i currently am taking a supplement, but don’t yet know if it’s having any effect.

  3. Adam Says:

    Great article. It’s interesting that in the EPIC-Oxford study, the difference between the vegans and others disappeared when calcium intake was adjusted for. I know many vegans that are vegan for ethical reasons and are essentially on junk food diets. Whenever I see a study showing that vegans are deficient in a certain nutrient compared to omnivores, I am always suspicious, since a vegan diet is not necessarily healthy.

  4. Ernest Says:

    Good article. I agree on most.

    I do think milk is bad for bones but cheese and yogurt is good. I think there are some substances produced in the fermentation that benefit bones (and other things). Maybe K2, maybe others (not yet discovered).

    I know some vegan fermented foods but I don’t know how many are popular (nowadays cheese is in everything).

    I’m vegan and I do eat natto regularly (believe or not I really like it).
    I also do take a 300 supplement of calcium everyday (that also contains some zinc).

    The article doesn’t mention K2. I don’t know how solid are the K2 studies on bones, but I do know that many people comment that it seems to work in the forums.

  5. Marek Says:

    Jack, below is a question I asked here about a year ago. I got a reply that the question is interesting and that you would try to find some information about it. Any news?

    Jack, I’ve recently come back to this question while preparing a lecture about vegan myths: Is there any reason why someone with a low calcium intake but normal serum PTH and Ca levels should still increase their calcium intake?

    I know quite a few vegans who don’t eat any calcium supplements, calcium-fortified foods or high calcium greens (so I assume their daily intake could be around 300-500 mg per day) but have normal blood Ca and PTH levels. I understand this doesn’t mean that everyone can do well on such low intakes, but it makes me much less convinced than I used to be about encouraging all vegans to increase calcium consumption to 700/1000 mg per day – especially since I feel a certain risk that it might do more harm than good in some cases (e.g. by possibly decreasing iron absorption). There are some practical reasons as well – we don’t have that many calcium fortified food and high-calcium greens in Central Europe.

    So I wonder whether regular checks for blood PTH and Ca levels first might actually be a better option – or at least a good alternative to – preventively struggling for 700/1000 mg calcium per day.

    What do you think?

  6. Jack Norris RD Says:

    Hi Marek,

    I’m sorry, I haven’t had a chance. In the past 8 months I’ve had very little chance to do any significant nutrition research. I hope to get back to it in the next few. In the meantime, perhaps you should contact some people at universities who research osteoporosis and are experts in how PTH affects bones?

  7. Jack Norris RD Says:

    Marek,

    I finally got around to checking out your question. First, normal calcium levels don’t indicate anything other than that you’re not in terrible metabolic shape–I should have pointed that out previously. But as for PTH levels, I emailed with Dr. Connie Weaver who has done a lot of research on calcium and she said:

    Typically PTH is measured fasting so wouldn’t have had Ca in the diet for maybe 12 hours. PTH responds minute to minute to serum Ca falling below normal due to inadequate amounts coming in from diet. But regardless of dietary intake, everyone’s PTH would return to their fasting state by the morning draw. The relationship between calcium intake and PTH shows up when you do a serial blood draw following a standardized test breakfast in order to plot PTH response.

    In other words, you cannot use one PTH measurement to assume you are getting enough calcium. I hope that helps.

  8. Jossi Says:

    Thanks a lot for this review (and this whole blog). I’m mostly vegan (actually vegetarian with very low intake of dairy and eggs) and believed for quite a long time all this “to much protein is bad for the bones-and-milk-is-a-bad-calcium-source”-stuff (but was wondering if the high osteoporesis rate in northern countries might be connected to Vitamin D deficiency).
    I now watch my calcium intake more carefully. I already preferred calcium-enriched soymilk (curls less in coffee, very nice), ate green vegetabIes regulary and liked sesame and pumpkin seeds a lot, but try to eat more of these foods. After I found out that poppy seeds are amazingly high in calcium (about 12times higher than milk) I now put some in my homemade bread and my muesli.

    This blog is altogether a very good source of information. I’m living in Germany and it’s quite difficult to get evidence-based information on vegan nutrition — it’s getting better, but the official nutrition organisation still proclaims, that eating vegan and healthy is nearly impossible and very risky even for adults. Non-official sources are not always very accurat and quite often based on out-dated information.

  9. Ron Says:

    Fermented cheeses have the MK-4 form of vitamin K2. I know of no vegan source of it besides supplements.

  10. Alex Says:

    Hi Jack, is the “true/false questionnaire” publicly available? This got me thinking of a longer questionnaire with Yes/No/Maybe answers ordered from most important/misunderstood to more obscure/less important.

    The history of the protein-calcium research is fascinating. It’s a great example of the subtle or profound evolution of knowledge. Thanks for sharing.

  11. Jack Norris RD Says:

    Alex,

    You can see the survey questions in Ginny’s post:

    http://www.theveganrd.com/2014/11/dietitian-perspectives-on-protein-calcium-and-vegan-bone-health.html

  12. Georges Washington Says:

    >People eating plant-based diets have lower calcium needs than meat-eaters. Probably FALSE

    I am not sure but I think this one may deserve to be revisited to “Unknown”, although while still mentioning that there is evidence that it is not considerably smaller, and people should not run the risk of discovering it by themselves.

    To my understanding, it is still unclear if the difference between the increased need in calcium and increase calcium absorption due to protein intakes is perfectly neutral.

    See the following quote from a study on which the DRI is based (which is somehow in line with the EPIC Oxford study results showing that increased fracture risk starts at <525mg/d):

    "The new estimation is in line with the previous consideration that individuals with low, but nutritionally adequate, intakes of sodium and protein may have calcium requirements as low as 500 mg/d"

    -Calcium requirements: new estimations for men and women by cross-sectional statistical analyses of calcium balance data from metabolic studies

    http://ajcn.nutrition.org/content/86/4/1054.full

    "Protein increases urinary calcium excretion, but its effect
    on calcium retention is controversial."

    -Dietary Reference Intakes for Calcium, Phosphorus,
    Magnesium, Vitamin D, and Fluoride

  13. Jack Norris RD Says:

    Georges,

    You make a good point and might be right. The one thing that gives me pause is that the average calcium intake in the EPIC-Oxford study for the vegans who had the same fracture rates was not 525 mg–that was just the lower cut-off. Not to mention that it was only one study and we shouldn’t conclude much from one study. But I would not be surprised if the average need for vegans is less than the DRI of 1,000 mg.

  14. Georges Washington Says:

    Thanks for your answer!

    I am probably a bit more prone to extrapolate on the basis of the first study (bone homeostatis being impaired under 741mg/day of calcium for the average american diet). But I may be comparing apples with oranges; I guess it’s also possible that fracture rate would only increase to any statistically significant level at a lower threshold than 741mg/day for the average american.

  15. Elyse Sokoloff Says:

    I have a question about the WHO recommendation. Every thing I find when I google their recommendation says 400-500 mg as a minimum for calcium intake but I can’t find anything saying 1000mg. Can you direct me to that? Thank you.

  16. Jack Norris RD Says:

    Elyse,

    See this post:

    http://jacknorrisrd.com/who-calcium-recommendations/

  17. mpe Says:

    Hi
    Any info on the absorption of dicalcium phosphate or Iron(II) fumarate, also known as ferrous fumarate,couldn’t find any on this & veganhealth.org website
    Thanks!

  18. Jack Norris RD Says:

    mpe–

    I don’t have any info on that.

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