Of all the nutrients of special interest to vegans, calcium may require the most effort to get. Sure, other nutrients demand attention too, but for the most part they’re all quite easy to obtain. Needs for Vitamins D and B12 are easily covered by popping supplements every two or three days. As for protein, there are tons of vegan foods loaded with it, plus you can always turn to vegan protein powder if you’re falling a bit short. Omega 3 needs can be met with a daily tablespoon of ground chia, plus a capsule or two of vegan DHA/EPA.
Attending to your body’s requirements for calcium requires greater care than what’s required for any of the above nutrients, since most foods are relatively low in calcium and most people don’t supplement for this nutrient, although supplementing would indeed by a wise choice for many.
Dairy Products and Calcium
Sometimes (often, really), people on both sides of an argument get their main points spectacularly wrong. That’s never been more the case than in the dispute between dairy interests and vegans regarding calcium. The dairy people seem times deliberately misleading, whereas the vegans have trotted out their share of misinformation as well.
The dairy industry has put calcium at the very center of their marketing. By repeating calcium at every turn, and holding up milk as a uniquely good source of this nutrient, they’ve created the impression that no source of calcium rivals milk. But that just isn’t true.
By contrast, a number of vegan books and websites have advanced a counterargument claiming that dairy is actually a poor source of calcium. The basis of this assertion is that because milk products have a lot of protein, most of the calcium in dairy is rendered non-absorbable. Often, this argument is accompanied by charts showing the rates of hip fracture in various countries, making it appear that the more dairy consumed the greater the rates of hip fracture. Both of these arguments have been thoroughly debunked. It turns out that protein content is only a tiny factor in calcium absorption, and that the calcium from milk is indeed well absorbed. As for the hip fracture argument, there are two confounding factors to make pointing to hip fracture rates dishonest. First, hip fracture rates are highest in high-latitude locations with lots of ice—and ice is of course closely associated with falls. On top of that, these high latitude areas tend to mean people have lower Vitamin D status, which plays a big role in bone health.
As we’re about to see, it’s nonsense to assert that dairy plays a unique and essential role in ensuring better bone health. But the response of many vegans is even less aligned with the truth. The reality is that it’s quite possible for a daily milk drinker to see her calcium status decline by going vegan—if she doesn’t make the effort to add calcium-rich foods to replace the dairy products she has given up.
How much calcium does a person need?
Before we compare the calcium content of milk to vegan foods, let’s first get a sense of how much calcium people actually need.
As with every other nutrient, there’s no hard and fast intake number that applies to everyone. Also, calcium needs vary at different ages, being highest during teen years, old age, and during pregnancy or lactation. Absorption rates differ from person to person, so when governments and nutritional councils set targets they try to err on the high side to ensure that the number suggested is sufficient to meet the needs of upwards of 95 percent of the population. Setting the target level for any nutrient is an inexact science, but an informed guess is obviously more helpful than no guess at all.
The most prestigious health advisory body in the United States sets calcium recommendations at 1300 mg. for people age nine to eighteen, 1000 mg for adults, and 1200 mg. for women over fifty and men over seventy. These numbers are probably not exactly right, but they’re the best we’ve got and it therefore makes sense to plan your diet in a way so that you can hit these recommendations.
Meeting Your Calcium Needs
Now that we know that you require something like 1000 to 1300 milligrams of calcium each day, meeting your needs becomes largely a matter of simple arithmetic. Here is what various calcium-rich vegan foods deliver:
Tofu (1 Cup. Must have calcium sulfate listed in the ingredients): 861 mg. (181 Calories)
Soy Milk (1 Cup calcium-fortified, unsweetened): 300 mg. (79 Calories)
Collard greens (1 cup cooked): 268 mg. (63 Calories)
Mustard greens (1 cup, cooked): 165 mg. (36 Calories)
Bok-Choy (1 Cup cooked) 158 mg. (20 Calories)
Kale (1 Cup chopped, cooked): 94 mg. (36 Calories)
Black Beans (1 Cup Canned) 84 mg (218 Calories)
Tahini (1 tablespoon, roasted): 64 mg. (89 Calories)
Broccoli (1 cup chopped, cooked): 31 mg. (27 Calories)
For comparison, whole milk supplies 276 mg. of calcium per cup, while containing 149 calories. So you can see that cow’s milk is an excellent source of calcium, but fortified soy milk is even better. And on a per-calorie basis, bok-choy has more than four times as much calcium than whole cow’s milk.
The above calcium figures are useful to keep in mind, but they’re also a lot to take in and make sense of. With many calcium-rich vegan foods, the limiting factor of how much you’d want to eat in a day isn’t how many calories they contain, but how bulky these foods are. For instance, kale contains a great deal of calcium per calorie. The trouble is that this calcium is accompanied by a whole lot of bulk. If you tried to meet your daily calcium needs solely through cooked kale, for instance, you’d have to eat ten cups a day. You’d have to be deranged to attempt that! Even worse would be the prospect of trying to meet your calcium needs solely through eating black beans. Just imagine what eating more than 10 cups of beans in a day would do to you.
Now there’s no question that you could eat some combination of beans, greens, and broccoli and get sufficient calcium. But your diet would be on the strange side, and would be too bulky for many people. That’s why the addition of some calcium fortified soy milk or some calcium-set tofu can make all the difference (If your tofu does not contain calcium sulfate in the ingredients, it’s not a good source of calcium. For the remainder of this article anytime I’m referring to calcium-set tofu, and that all references to vegan milks denote calcium-fortified varieties).
Together, tofu and fortified vegan milks transform the task of getting sufficient calcium from tricky to easy. For example, if you simply drink a cup of soy milk with breakfast, and then include a half-cup of tofu as part of your dinner, through those two choices alone you’ve already met half your daily calcium needs. From there, you need only eat a relatively small amount of beans and greens to put yourself over the top.
The reason the tofu and soy milk delivers such a big hit of calcium is because these foods have pure calcium carbonate listed in their ingredients. Some vegans might object that this isn’t “natural,” but there isn’t any reason why calcium obtained this way is inferior to getting calcium from vegetables or from cow’s milk. For the same reason, a vegan calcium supplement is also a great way to lift your daily intake up to the recommended 1000 to 1300 mg level. Depending on the brand (check the label), just one tablet could give you a whopping 500 to 1000 mg. calcium, enabling you to easily elevate your status from insufficient to excellent.
We’ve just seen that leafy greens contain a great deal of calcium; this is true for every variety, not just those we’ve listed above. But there’s an important caveat to keep in mind: several popular greens are loaded with oxalates (oxalic acid). These oxalates interfere with calcium absorption. Oxalates won’t cancel out all the calcium in greens, but they can interfere with absorbing most of it. So if you’re eating greens for the sake of getting enough calcium, you’ll want to avoid spinach, chard, and rhubarb—all of which are rich in oxalates. Note that if you choose to boil oxalate-rich greens, much of the oxalic acid will leech out into the water, thereby calcium absorption assuming the cooking water is discarded.
The greens mentioned in the previous section—collard greens, mustard greens, bok-choy, and kale—are all low in oxalates, and are therefore superb sources of calcium.
It doesn’t make any difference to the body whether you meet your needs through foods that are naturally calcium-rich or through fortified foods. If you’re having a hard time getting sufficient calcium through food alone, calcium supplements can be an easy way to close the gap. Deva Nutrition manufactures an excellent and affordable vegan calcium & magnesium supplement.
Be aware that too much calcium can lead to kidney stones, so make sure that your combined calcium intake from food and supplements doesn’t exceed 1300 mg. per day.
Exercise and Fitness
For further reading: “Protecting Bone Health on a Vegan Diet,” by Virginia Messina, MPH, RD.