Getting Enough Calcium on a Plant Based Diet

When I was in university studying nutrition, it was ingrained in us that it was essential to eat dairy to get enough calcium. We would have representatives from the dairy industry come and talk to our classes of 300+ students about the importance of dairy, and we even visited local dairy farms for Agricultural Science class.

"What about plant based sources like broccoli and tahini?" I would ask, the professor would respond with "well you'd have to eat 10 cups of broccoli a day".

This was over 10 years ago, so I am hoping there is more dialogue in university nutrition programs about meeting calcium needs from plant foods now, especially since approximately 65% of the population is actually lactose intolerant (5, 6). Also, higher milk consumption does not seem to lower the risk of bone fractures (7), but it does seem to be  associated with higher rates of cancer (8, 9, 10, 11). 

So, how can we meet our calcium needs on a plant based diet? Do we have to eat cups of broccoli all day? Is it something vegans even need to worry about? 

The recommended dietary allowance (RDA) of calcium for adults 19-50 years old is 1000mg per day (2). For children 9-18 years old it is 1300mg, and for adults over 50 years old is it 1200mg (2)

When you start looking at the calcium content of your favourite plant foods, it may first seem difficult to reach 1000mg each day.

Incorporating fortified plant milks is a great way to increase your calcium intake, as one cup provides about 300-400mg. 

Calcium-set tofu is another great source of calcium. It provides about 250mg per 1/2 cup serving, but do check the labels as the calcium amount does vary.

When it comes to dark leafy greens, the amount of calcium we are able to absorb depends on the amount of oxalates in the greens.

For spinach, beet greens, and Swiss chard, only about 5-10% of the calcium in is absorbed (1).

With lower oxalate greens like kale, broccoli, Chinese greens, turnip greens, and mustard greens, the absorption of calcium is between 50-65% (1). Collards can be considered a good source as well, even though they are slightly higher in oxalates.

One cup of cooked, lower oxalate greens provides: 

Broccoli............................................................72mg*
Kale..................................................................94mg
Mustard Greens.............................................104mg
Chinese Cabbage (Boy Choy/Pak Choi)........158mg
Turnip Greens.................................................179mg
Collards...........................................................266mg

If you're eating any of these raw, just double the serving size to 2 cups since cooking reduces the amount of oxalates.

The absorption rates for calcium carbonate fortified plant based milks and tofu are similar to that of dairy, at about 30% (3, 4). These absorption rates were taken into account when the RDA was determined. 

If you are including fortified plant milks, calcium-set tofu, and cooked low oxalate greens on a daily basis it shouldn't be too difficult to reach 1000mg of calcium per day as small amounts will be coming from the other foods you eat as well, like beans and seeds.

*Looking back at what the professor said about having to eat multiple cups of broccoli to reach our calcium needs. Yes, if your only source of calcium is broccoli, you’d need almost 14 cups. But we do not have to meet our specific nutrient needs from a single food, nor should we, as diet diversity is the best way to support our gut microbiome and overall health. 

The key to getting enough calcium from a plant based diet is to include a variety of sources. Plus, diets high in fruits and vegetables have positive effects on bone density (12, 13).

If you are not sure about your diet, please feel free to get in touch with me for a free 15 minute call, order a custom meal plan, or a full in-depth consultation about your specific plant based nutrition needs.

References:

1. Choices for achieving adequate dietary calcium with a vegetarian diet.
​2. Vitamin D and Calcium: Updated Dietary Reference Intakes.
3. Bioavailability of Calcium from Tofu Compared with Milk in Premenopausal Women.
4. Calcium bioavailability of calcium carbonate fortified soymilk is equivalent to cow's milk in young women.
5. Lactose Intolerance (American Family Physician).
6. Lactose Intolerance (US National Library of Medicine).
7. Milk intake and risk of mortality and fractures in women and men: cohort studies.
8. Dairy, soy, and risk of breast cancer: those confounded milks.
9. Dairy products, calcium, and prostate cancer risk in the Physicians' Health Study.
10. Association between Neu5Gc carbohydrate and serum antibodies against it provides the molecular link to cancer: French NutriNet-Santé study.
11. The possible role of female sex hormones in milk from pregnant cows in the development of breast, ovarian and corpus uteri cancers.
12. Fruit and vegetable intakes and bone mineral status: a cross sectional study in 5 age and sex cohorts.
13. Potassium, Magnesium, and fruit and vegetable intakes are associated with greater bone mineral density in elderly men and women.