My last post addressed a common myth about protein and bone health—probably the most widely disseminated myth in the vegan community.
In contrast to long-held beliefs, current thinking is that protein either has little impact on bone health or it might have some small benefits. This suggests that the lower protein intake of vegans and our avoidance of animal protein doesn’t confer any particular protection for bones. Instead, we vegans need to make sure we are getting enough protein and calcium in our diets.
If your diet is built around a variety of whole plant foods including at least three servings of legumes (beans, soyfoods and peanuts) per day, and your calorie intake is sufficient, you won’t have any trouble getting enough protein. If you are on a reduced calorie diet or you’re an athlete, you may need more than the three servings of legumes.
Calcium is a little different. It’s not that it’s difficult to meet needs, but you do need to make a bit of effort to include calcium-rich foods in your diet. Both the Institute of Medicine (the government agency that establishes the RDAs) and the World Health Organization recommend 1,000 milligrams of calcium per day for adults (or 1200 for those over 50).
The recommendation is based on the assumption that we absorb about 30 percent of the calcium in our diet—since that’s the absorption rate for calcium from cow’s milk. That is, our biological need for calcium is around 250 to 300 milligrams of calcium per day, but we need to consume as much as 1000 milligrams in order to absorb enough. Or at least that’s true if you get most of your calcium from cow’s milk.
For certain leafy green vegetables, absorption rates are considerably higher. For example, we absorb between 50 and 60 percent of the calcium in cruciferous leafy green vegetables like kale and turnip greens. In contrast, absorption rates for calcium from beans is fairly low at about 17 percent. And for oxalate-rich vegetables like spinach, absorption is extremely low, only around five percent.
So, it’s really better to pay attention to our biological needs and the amount of calcium we’re likely to absorb from a food, rather than the amount that is actually in foods. Unfortunately, we don’t have this information for very many foods.
The table below shows the amount of calcium absorbed from a few foods that are relevant to vegan diets (with cow’s milk included for comparison). And we can use a couple of extreme examples to show just how important the absorption issue is. For example, if you ate three cups of cooked turnip greens as your sole source of calcium, your intake—about 600 milligrams—would be well below the calcium RDA. But you’d still absorb enough to meet biological needs. Alternatively, you could meet the calcium RDA by eating about 4 1/2 cups of white beans, but you’d absorb only around 170 milligrams which is well below biological needs.
I typically get my calcium from a mix of fortified orange juice, tofu, and greens. I mostly aim for the RDA, but on the days when I’m eating a lot of greens, I don’t worry about it quite as much. I don’t exactly micromanage this, but I do pay attention to it. I don’t depend on beans and nuts for my calcium too much because the absorption is so poor, but I know that they contribute at least some calcium to my overall intake.
Getting calcium from fruits and vegetables might have some advantages since diets rich in these foods are linked to improved bone health. This may be because plant sources of calcium are often high in potassium, vitamin C, and vitamin K, all important for keeping bones strong. There has also been interest in the idea that isoflavones in soymilk and tofu might protect bone health, but the findings on this are pretty conflicting.
So, bottom line: Vegans cannot ignore calcium, but it’s relatively easy to get enough. And there may be benefits for everyone to getting calcium from plants.
|
Plant sources of calcium. Amounts are 1 cup cooked unless otherwise noted. |
Milligrams of calcium (RDA is 1000-1200) |
Milligrams of calcium actually absorbed (Biological need is 250-300) |
| Fortified orange juice |
300 |
108 |
| Soymilk w/ calcium carbonate |
300 |
92 |
| Cow’s milk |
300 |
92 |
| Tofu, calcium set, ½ cup |
258 |
80* |
| Soymilk w/ tricalcium phosphate |
300 |
72 |
| Collard greens |
266 |
133** |
| Turnip greens |
196 |
102 |
| Chinese cabbage |
158 |
85 |
| Mustard greens |
128 |
74 |
| Kale |
94 |
55 |
| Broccoli |
70 |
37 |
| Cabbage |
50 |
32 |
| Almonds, ¼ cup |
80 |
17 |
| White beans |
226 |
38 |
| Pinto beans |
89 |
15 |
| Spinach |
244 |
12 |
*amount will vary considerably depending on firmness of tofu
**absorption from collards hasn’t been measured but I think it’s safe to assume that it is at least 50%
References for calcium absorption:
Weaver CM, Plawecki KL. Dietary calcium: adequacy of a vegetarian diet. Am J Clin Nutr 1994;59:1238S-1241S.
Zhao Y, Martin BR, Weaver CM. Calcium bioavailability of calcium carbonate fortified soymilk is equivalent to cow’s milk in young women. J Nutr 2005;135:2379-82.
Heaney RP, Dowell MS, Rafferty K, Bierman J. Bioavailability of the calcium in fortified soy imitation milk, with some observations on method. Am J Clin Nutr 2000;71:1166-9
Nothing in this excellent post that I can dispute. I do have one question though.
I have noticed that there is a fair amount of calcium in many whole grain products, and three that I eat are hemp protein powder, wheat germ and wheat bran (all very recent additions to my diet). The table you present does not contain any data on grains – is that because grain calcium is relatively scant, poorly absorbed, or for some other reason not considered a reliable source of dietary calcium intake? Or is there just a lack of studies on using grain to fulfill biological calcium requirements?
Right–I didn’t include grains for all the reasons you mentioned. There really aren’t many current studies on absorption. But wheat germ and wheat bran are both pretty low in calcium, and I’m guessing that it’s not well-absorbed from either. So I don’t think I’d depend on these very much. I don’t know about the hemp protein powder.
The only grain that might be a good source of calcium are corn tortillas if they are processed in the traditional way with lime. Some older research shows that it’s fairly well absorbed.
Do you happen to know anything about the calcium in Teff? I’ve seen it listed as a high calcium grain, but I guess it may fall into the same category as other grains with being less absorbable?
Dr. Gregor did a video on nutrient absorption from grains, though he did use rice and focused on iron and zinc but I wonder if a similar thing happens with calcium absorption from grains. http://nutritionfacts.org/video/new-mineral-absorption-enhancers-found/
Teff has about 120 milligrams of calcium in a cup, but I don’t know about the absorption. I probably wouldn’t depend on it as a major source of calcium, but it will certainly contribute to your intake.
Awesome info! Can you tell me the absorption rate of calcium in sesame seeds and blackstrap molasses?
I don’t have info for molasses, and I’m actually a little confused about the information I found for sesame seeds. The research is showing that very little is absorbed–about 8 milligrams of calcium per ounce (about 2 tablespoons). But they are also showing sesame seeds to be generally low in calcium content–just 37 milligrams per ounce.
More recent data from the USDA suggests that sesame seeds contain about 180 milligrams of calcium per 2 tablespoons. I think the difference may be because the absorption research was done on hulled sesame seeds which have less calcium than regular whole sesame seeds. I don’t know how well the absorption would be from whole sesame seeds, though. So–I just don’t know!
>the most widely disseminated myth in the vegan community.
I dunno — there’s some crazy still competition!
Can we assume the calcium carbonate in instant oatmeal absorbs at about the same rate as that in soy milk?
I don’t know. The food matrix has some effect on absorption, but I would expect absorption from fortified oatmeal to be fairly good. Absorption of calcium carbonate is generally good.
Thanks!
What should one do if one already has osteoporosis? The medications are dismal and most likely not vegan. Is there a dietary solution?
Barbara, I do hear from people who reverse their osteoporosis with calcium and vitamin D supplements and lots of weight bearing exercise. And I would add lots of fruits and vegetables to that mix.
Take a look at this post from Jack, which has some interesting anecdotal information: http://jacknorrisrd.com/strontium-for-increasing-bone-mineral-density/
This is a question for Virginia Messina. We met at the Vegetarian Food Festival in St. Catharines ON. I have been reading the book Vegan for Life and am blessed. I have been reading articles stating that we need a supplement of K2 and somehow the vitamin K2 that is produced by bacteria in the gut is not made available/absorbable to be utilized by the body. What is the latest on that? Should I be advising people to take vegan vitamin K2.?
maybe stupid question: so if my levels are fine according to my recent bloodwork, then I’m fine, right? a year ago I ditched all supplements but B12 (even D) as an experiment. I don’t eat fortified foods. And calcium was fine, as was D, though it was on the low side of acceptable (one or 2 units above the mimimum). And I get WAY more sun than the average person, all year long, here in South Florida. My takeaway was that everyone (even me, but I was skeptical) needs to supplement with D, and that calcium can be done even without fortified foods. Is that fair? B12 was actually high. I think I take too much out of fear.
Mary, you can’t really find much from measuring blood levels of calcium because they tend to stay within a narrow range and aren’t affected by diet. So I would aim for getting the RDA for calcium in whatever way works for you.
Can you comment on the bioavailability of calcium in supplements, specifically the Trader Joe’s Cal-Mag-Zinc supplement?
I never eat enough greens (but do better with beans). I make my own soymilk, so it’s unfortified, and I don’t think the tofu I usually buy is made with calcium sulfate. I don’t drink much orange juice, either, but I probably should, just to assist with absorption.
Thanks for a great article.
Here are the specs on the TJ supplement (2 tablets):
Calcium 1000mg/100%
Magnesium 500mg/125%
Zinc 15mg/100%
That’s calcium carbonate in those supplements, right? Absorption is usually pretty good. If anything, the calcium might lower the absorption of the zinc a little bit from the supplements, but that’s okay since there is plenty of it in the pill.
Do you take the supplement with meals? It’s absorbed better that way.
And I don’t think you need to start drinking orange juice necessarily. I would look for tofu that is made with calcium sulfate though since tofu is something you already eat.
Ginny, thanks for your reply about grains.
I am curious as to whether there is strong evidence that achieving the recommended calcium intake actually prevents osteoporosis, in vegans or non-vegans. Do randomized trials support this? From what I have read, the mechanism underlying the recommendation is that calcium is necessary for normal skeletal homeostasis – which sounds obvious, but has anyone actually tested this to see if it is true? (I am aware that in EPIC the vegans who ate less than ~530 mg of calcium per day had significantly higher rates of osteoporosis). I also wonder if widespread screening for osteoporosis is warranted and we are scaring and treating large numbers of healthy, asymptomatic people into taking drugs and supplements who would never get a fracture. That hasn’t been answered to my satisfaction in the literature. Obviously people at risk of OP should get screening, but I don’t think everyone over a certain age should.
Two different questions here.
Dan, I agree that these questions haven’t been answered conclusively. Calcium is related to bone mineral density, but the association with fracture risk is less clear. We know that calcium is needed for bone health, but how much is needed is hard to determine. Especially since needs probably vary a lot among individuals.
But there is no harm in aiming for the calcium RDA, even if you achieve that through a little bit of supplementation.
As for screening–I just don’t know. Right now the recommendations are to screen post-menopausal women who have risk factors, and all women over the age of 65. (I don’t think there are any screening recommendations for men.) Is that overkill? Osteoporosis is a serious disease with the potential to be debilitating, so catching it early would seem to be a good thing.
Ginny, thank you so much for your thoughtful reply.
As to population-based screening – i.e. based on certain age and sex demographics – this is what UpToDate(R) had to say:
“EFFECTIVENESS OF EARLY DETECTION — The gold standard that would support screening for osteoporosis is the demonstration in a well-designed randomized trial that screening reduces fracture risk. Determining the relative effectiveness of screening would also depend upon the quality of the BMD measurements and the risk factor analysis, the ability of the clinician to prescribe appropriate treatment, and the compliance of the patient.
In the only published trial, 4800 postmenopausal women (aged 45 to 54 years) were randomly assigned to osteoporosis screening (BMD measurement) or no screening [51]. Follow-up data were obtained via questionnaire. After a mean of nine years, a greater proportion of screened women reported current or past use of hormone therapy (52 versus 45 percent) or other osteoporosis medications (37 versus 22 percent). In an intention-to-treat analysis, there was a nonsignificant reduction in the incidence of fracture in the screened group (8.8 versus 9.4 percent, HR 0.79, 95% CI 0.60-1.04). Limitations of trial include a low (60 percent) response rate and self-report of hormone therapy (HT) or other osteoporosis medications.
Other estimates of the fracture prevention benefits of screening and intervention are largely based upon trials of bisphosphonates that enrolled postmenopausal women who were at high risk for fracture. The fracture benefits noted are not applicable to a screening program because patients were not identified for participation in the trials by screening the general population [52].
In the absence of definitive data, population-based screening remains controversial.
Arguments supporting screening — There are a number of arguments to support screening for osteoporosis:
It is a common disease with significant morbidity and mortality and without screening many high-risk patients would go undetected. (See ‘Epidemiology’ above.)
Screening through risk factor assessment and bone mineral density (BMD) testing is available to many clinicians in some countries.
The risk for most fractures is inversely proportional to BMD (figure 1) [53-60].
A number of effective therapies (both pharmacological and nonpharmacological) are available to reduce fracture risk in patients who are diagnosed with osteoporosis. (See “Overview of the management of osteoporosis in postmenopausal women” and “Treatment of osteoporosis in men” and “Calcium and vitamin D supplementation in osteoporosis”.)
Knowledge of fracture risk, which includes but is not limited to BMD, could improve compliance with both lifestyle changes and pharmacotherapy.
Arguments against screening — There are several arguments against widespread screening for osteoporosis [42].
As noted above, the only published randomized trial did not find a significant fracture benefit from screening but had some design limitations [51].
There is no discrete value for BMD that discriminates clearly between patients who will fracture and those who will not. In addition, many fractures occur in those without osteoporosis by BMD criteria, which decreases the value of using BMD (alone) as a tool for identifying individuals at high risk for fracture.
A single measurement indicates only current BMD, not the anticipated rate of bone loss. Other factors may be more important in predicting the risk of fracture than BMD [9]. (See ‘Assessment of fracture risk’ above.) As an example, fall-related risk factors may be more important in predicting hip fracture than BMD since more than 90 percent of hip fractures result from falls onto the greater trochanter [61]. (See “Falls in older persons: Risk factors and patient evaluation”.)
Certain preventive measures, such as adequate calcium and vitamin D intake, exercise, and smoking cessation, should be recommended regardless of BMD.
Furthermore, there is some evidence that women with normal BMD are less likely to follow these preventive measures [62].
The availability of DXA and willingness to pay for healthcare varies from country to country and with differing clinical practices [63].”
Thanks, Dan. I don’t really keep up with recommendations on screening since it’s outside my area of expertise. This was all very interesting–and leaves me feeling still like it’s hard to know what to recommend!
So the only way I know I’m getting enough is to make sure I’m putting enough in and the bloodwork is useless? I do watch what I put in, but I soooo thought that the way to make sure I was doing it right was to do the bloodwork. Thanks!
Thank you so much! Your statement of eating at least 3 servings of legumes a day to meet my protein requirement was an eye opener. I only eat legumes once a day, assuming I get enough protein from other sources. My question is: how much is a serving?
A serving is 1/2 cup of cooked beans or tofu, 1 cup of soymilk, 1 oz veggie meat, 1/4 cup peanuts, or 2 tablespoons of peanut butter. So not just beans. Maybe you get more than you think!
I try to eat calcium rich food but since my dexa tests keep getting worse I started taking an antacid product as a supplement for calcium . I have started taking a 1000 mg chewable tablet which has 1000 mg. but 400 elemental calcium (carbonate). Thanks Ginny. I value your opinion.
The USDA’s data is different from yours, for example:
Broccoli, 1 cup, cooked — 31
http://ndb.nal.usda.gov/ndb/foods/show/2921
Cabbage, 1 cup, cooked — 36
http://ndb.nal.usda.gov/ndb/foods/show/2938
White beans, 1 cup, cooked — 161
http://ndb.nal.usda.gov/ndb/foods/show/4772
Oh sorry, my mistake. A cup of broccoli is actually have 62 mg of calcium and a cup of cabbage have 72.
Okay–so smaller differences, but still different!
I took some of the numbers from the studies on absorption, which were done quite some time ago and therefore used older USDA data. But since total calcium content is going to vary from one food sample to another, those numbers do change. They constantly need to be updated.
What about chia seeds? I read that they are high in calcium. What about their absorption rate?
Chia seeds have about 180 milligrams of calcium per ounce. I’m not sure how much that is–maybe 2 tablespoons? I suspect that it isn’t very well absorbed because calcium absorption tends to be low from intact seeds. If they were ground up, it might be better.
Very odd. My peanut butter says that 1 tablespoon (15 g) meets 0% of the RDA of calcium. I think this must be wrong. The sole ingredient is roasted peanuts (no other additives). I will check peacounter. I am sure that peanut butter must contain some calcium!
[…] Vegan Diets for Healthy Bones […]
As always a great post – thank you for sharing that.
People focus so much on getting food in that they forget that the most important part of that equation is what actually gets absorbed.
Hello,
Thanks for the article, I translated into Spanish and posted it on my website and I got two questions from readres, that I am no qualified to answer myself.
1) Is there any data on the absortion rate of sesame seeds?
2) Given that fortified orange juice does not exist in Chile, would it be just as effective, absortion wise, to home fortify bevarages with calcium carbonate?
Thanks in advance!
Sprouted chia would probably provide better absorption of the calcium than the intact seeds – http://www.nutraways.com/Sprouted-Chia-Seed-Powder_p_5614.html
I have been under the impression that Calcium supplements were a “no-no,” and the better preventative for weak bones is weight-bearing exercise. My Chinese herbalist tells me to eat black sesame seeds for Calcium (I grind them with chia and flax) .
I find this article really disheartening.
It doesn’t seem reasonable to consistently meet the RDA.
I mean 1000mg + low absorption rates?
According to your chart you would have to eat nearly everything on that list EVERYDAY to meet your RDA.
I don’t even eat that much food in a day little lone those foods specifically.
Josh, I’m not sure why you think you need to eat all of the foods on the chart to meet calcium needs. You could meet needs by eating 1 cup of collards + 1 cup of a fortified plant milk or juice + 1/2 cup of tofu. That would be enough to provide the biological need of 250 to 300 milligrams of calcium.
I got the rda confused with the biological need.
Here is what I have done to ensure I get enough calcium in my diet (please feel free to comment):
1) I consume 0.5 cup of almond milk per day (that gives me about 150 mg of Ca2+).
2) In a breakfast shake, I pulverize 2 tablespoons of sesame seeds, and add to this hemp protein powder, wheat germ, wheat bran and a diverse assortment of nuts and seeds.
3) I eat two servings of legumes per day (lunch and dinner). Usually black chick peas and black soybeans or green soybeans.
4) I eat tahini – 3-4 tablespoons – with lunch.
5) Forgot to mention – I add a teaspoon of blackstrap molasses, which is very high in calcium, to the breakfast shake.
6) I eat 2 large tablespoons of peanut butter at breakfast.
My best guess is that my intake of calcium is somewhere around 700-1000 mg per day (likely on the higher side of this range).
I also ensure I take vitamin D supplement daily, even in the summer.
I still worry this is not enough calcium, and I definitely do not wish to supplement, given the randomized trials showing increased rates of MI and stroke with calcium supplements. It was for this reason that the ongoing 20,000 patient VITAL trial decided not to include a calcium arm (it is studying 2000 IU of vitamin D3 and 1000 mg of omega-3 in a 2 x 2 factorial design with matching placebos for both).
Dan
Great article, Ginny — all of this updated info about protein and calcium interrelationships is very helpful !
I’m a relatively new vegan and have been including about 2 cups of fortified soy milk, a couple of servings of almond butter, garbanzo beans thrown into salads, cannellini beans added to pasta and some kale blended into smoothies in my diet to try to meet my calcium requirements: at the outset of my dietary change, I picked up copies of ‘Vegan for Life’ and ‘Becoming Vegan’ to make sure I went about my new diet in a healthy way, both of which were extremely helpful, and both of which also made me realize that I couldn’t just take calcium for granted in my diet. I also try to use blackstrap molasses and maple syrup often when making baked goods, since these appear to contain some calcium, and also drink mineral water, which lists about 4 to 8 % RDA calcium for the higher-mineral-content waters, depending upon the brand.
Additionally, I have decided to include calcium supplements morning and night, just to be on the safer side. The product I’ve been buying combines calcium citrate and magnesium in a vegcap, as I’ve read that the citrate form is a bit better-absorbed than is the carbonate form of calcium, one pill of which supplies 20 % of the RDA or 200 mg Ca. I usually take either one or two capsules of these morning and night, supplying 40 to 80 % of the RDA total in a day, but I’m wondering if two tablets (400 mg Ca) is too much calcium to be taking all at once: I heard somewhere that calcium is absorbed best when consumed in moderate amounts throughout the day, rather than all at once. On the other hand, the bottle of my calcium supplement says that it’s perfectly okay to take five capsules (100 % RDA) all at once or to spread them throughout the day O_o …why does this mineral absorption stuff have to be so complicated LOL ?
Thank you for your great article =)
Do you know anything about calcium-rich mineral water as a source of calcium for vegans?
I have a current German dietetics book listing some brands of mineral water as having around 500-600 mg of calcium per liter. (Most mineral water used in Germany, not all, is carbonated – not sure if that influences absorption.) Depending on the region tap water might also be high in calcium.
If calcium rich mineral water was indeed a good source, this could also be useful for vegans in other (eg less industrialized) countries, where fortified foods aren’t as widely availble.
I did a quick search on pubmed:
(I only read the abstracts)
“All the high-calcium mineral waters had absorbabilities equal to milk calcium or slightly better.” (http://www.ncbi.nlm.nih.gov/pubmed/16895885)
“The urinary excretion of Ca was higher (0.5 mmol/d more) with water than with milk (P<0.001). An examination of all the dietary factors known to influence calciuria suggested that the acidogenic action of SO4 was responsible for this increased calciuria. Thus, despite an equal Ca intake and assuming an unchanged intestinal absorption, these results suggest that Ca balance is better with milk consumption than with CaSO4-rich water." (http://www.ncbi.nlm.nih.gov/pubmed/15788116)
"The calcium from the mineral water is thus highly bioavailable, at least as bioavailable as milk calcium" (http://www.ncbi.nlm.nih.gov/pubmed/15365401)
"Mineral waters, on the other hand, were generally found to contain higher calcium concentrations, an average of 208 mg/L of calcium. Filtration was found to remove a considerable amount of calcium from the water, removing 89% on average." "[…] certain waters may be used as a source of calcium that may provide over 40% of the recommended daily intake for calcium." (http://www.ncbi.nlm.nih.gov/pubmed/18751825)
"A meta-analysis based on published p values indicated calcium absorption from mineral waters was significantly higher (p = 0.03) than that from dairy products. Although only few studies with a relatively small number of subjects are available to date, the bioavailability of calcium from calcium-rich mineral waters thus seems to be at least comparable to, and possibly better than, that from dairy products." (http://www.ncbi.nlm.nih.gov/pubmed/11193246)
"Mineral waters containing calcium are recommended as a supplemental source of calcium to achieve optimal calcium requirements, especially in aged people with lactose intolerance." (http://www.ncbi.nlm.nih.gov/pubmed/9252974)
"Therefore, calcium from the CS-W [calcium- and sulfate-rich mineral water] was as well absorbed and retained as that from milk, and no calciuric effect of sulfate was found, showing that such mineral waters can be valuable dietary sources of calcium." (http://www.ncbi.nlm.nih.gov/pubmed/7491887)
"The calcium of Sangemini water is thus highly bioavailable, and at least as bioavailable as milk calcium" (http://www.ncbi.nlm.nih.gov/pubmed/7696826)
"We report herein that the bioavailability of Ca from the water was generally as good as or better than that from milk, a food product well known for its very high Ca bioavailability" (http://www.ncbi.nlm.nih.gov/pubmed/1790046)
[…] •A great read from Ginny Messina (The Vegan R.D.) about vegan diets for healthy bones. […]
[…] http://www.theveganrd.com/2013/08/vegan-diets-for-healthy-bones-2.html […]
[…] by reading Ginny Messina’s vegan calcium primer, then check out her posts on vegan diets for healthy bones (which includes good information on absorption) and her post on protein and bone health, which […]
Thanks for sharing.