Calcium on a Plant-Based Diet

Calcium is one of the most controversial nutrients on a plant-based diet. Can you get enough without eating dairy? What are good food sources? Is dairy really the only source? Let’s answer these questions and more.

Tofu skewers
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Digestion of Dairy

Calcium can be consumed from both plant-sources and dairy. Many people don’t know this, as nutrition education campaigns are often focused on the dairy sources of calcium as they are funded by the dairy industry. However, not everyone is able to or chooses to eat or drink dairy. Typically, after the age of weaning (after people stop drinking breast milk), 70% of the enzyme needed to break down lactose, called lactase, is diminished in our guts. Through natural selection, most Western cultures have developed the trait to be able to break down lactose past the age of weaning to allow proper digestion of dairy. However, over 50% of the population in South America, Africa and Asia experience lactose intolerance, with symptoms such as abdominal pain, bloating, excess gas and diarrhea.

Function of Calcium

In the simplest term, calcium gives structure to bones and teeth. Getting enough calcium during growth and adolescence helps to avoid fractures later in life, and we actually reach our peak bone mass by the age of 28.

Forming and maintaining strong bones and teeth uses about 99% of the calcium in the body. The other 1% is used to help blood coagulate after injury, help our muscles relax, regulate blood pressure and regulate cell metabolism (1). Even though these functions only require about 1% of the calcium in our body, ensuring that the level stays consistent is very important. Our body will essentially do anything to make sure that this 1% stays consistent.

If our body has too little calcium, our parathyroid gland activates vitamin D into action. Our body can quickly increase our calcium stores by increasing the amount that is absorbed from our food, and decreases the amount lost in urine. If severely low, our body will resort to taking calcium from our bones and teeth to keep this 1% stable.

Plant-based milk

How much do we need?

Adults over 19 years old should get 1,000 mg of calcium per day. As we get older our calcium stores start depleting, which is why women over the age of fifty and men over the age of seventy should aim to get 1200 mg.

When reading a food label, simply look at the percentage of calcium the particular serving of food provides. Add an extra 0 to the amount to get the mg of calcium the food provides. For example, if a one cup serving of fortified cashew milk provides 45% of your daily calcium needs, you know that this is 450 mg  per cup.

Chia seeds
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Calcium on a plant-based diet

Calcium levels can be as low as 50-94% of required intake when following a poorly planned, plant-based diet. However, it’s important to note that even those not following a plant-based diet should be cognizant of their calcium intake, with studies showing that even non-vegetarians are often below the recommended amount of calcium per day. Because of this, whether you choose to consume meat, dairy, eggs, or choose to omit them from your diet, everyone should be aware of their calcium intake and make sure you’re consuming enough.

Calcium found in plant-based milk, plant-based yogurts and tofu is absorbed at the same rate as those found in cows milk. Therefore, these foods should be a vital part of a plant-based diet. When using plant-based milks, make sure to shake the container well before use as the supplemented part of the beverage (calcium, vitamin D and vitamin B12) often fall to the bottom.

Many people often opt to make their own plant-based milks. In theory, this sounds like a good idea. However, plant-based milks are often fortified with nutrients that are lacking in the typical Western diet- calcium, vitamin D, and Vitamin B12. Because of this, I recommend consuming store-bought, fortified plant-based milks more often than homemade. If making homemade plant-based milk is a better option for you, try consuming at least two servings of calcium set tofu or plant-based yogurts daily.

High calcium foods

Oxalate

Calcium is abundant in many vegetables, particularly those low in a compound called Oxalate. Oxalates are oxalic acids that binds to minerals in food such as calcium, magnesium, iron and zinc. When oxalic acids and these minerals are combined, it means that our bodies can’t absorb as much of that nutrient.

This doesn’t mean that we should be avoiding these foods!  Foods that contain oxalates are high in other important such as folate, vitamin K, beta-carotene and fibre, meaning the benefits of eating them outweigh the cons. Instead, it’s important to be cognizant that high oxalate foods shouldn’t be your main source of iron, calcium, magnesium and zinc. If these minerals are of concern to you, try consuming low oxalate foods more often than high oxalate foods.

High oxalate foods:

  • amaranth
  • Beets
  • Beet greens
  • Cassave
  • Chives
  • Miso
  • Parsley
  • Spinach
  • Starfruit
  • Swiss chard
  • Whole sesame seeds

Medium oxalate foods:

  • Collard greens
  • Dandelion greens

Low oxalate foods:

  • Broccoli
  • Bok choy
  • Kale
  • Napa cabbage
  • Watercress
  • Mustard greens
  • Turnip greens

Plant-based Calcium Rich Foods

  • Oranges: 52 mg
  • Bok choy : 84 mg
  • Basil (1 cup chopped): 79 mg
  • Dandelion greens (1 cup): 109 mg
  • Kale (1 cup): 100 mg
  • parsley (1 cup): 89 mg
  • Almond butter (2 tbsp): 113 mg
  • Almonds* (1/4 cup): 96 mg
  • Chia seeds* (1/4 cup): 269 mg
  • Poppy seeds (1/4 cup): 490 mg
  • Fortified soy milk (1/2 cup): 158-163 mg
  • Soybeans/edamame (1/2 cup): 93mg
  • Tempeh (1/2 cup): 97 mg
  • Tofu** (calcium set, 1/2 cup): 268-909 mg
  • Black strap molasses (1 tbsp): 80-200 mg

*Soaking nuts and legumes for 8-24 hours before consumption makes calcium more absorbable. Nuts and legumes can be soaked form 8-24 hours before consumption to make calcium more absorbable.

** Calcium-set tofu is pressed in a calcium sulphate brine. Look on the nutrition label to see if the tofu you’re purchasing is high in calcium.

Kale smoothie
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What Impacts absorption

Absorption of calcium can be decreased from excessive salt, alcohol and caffeine consumption. It can also be decreased from oxalates, smoking and vitamin D. If you live somewhere with limited sunlight exposure, consult a physician or dietitian about taking a vitamin D supplement (1).

Are calcium supplements necessary?

Obtaining nutrients from food first is always recommended, as food also contains other nutrients, fibre, antioxidants and energy. Individuals following a plant-based diet may benefit from taking a calcium supplement to cover the amount of recommended daily amount that they are not getting from food. This is likely about 200-400 mg of calcium (1). Consuming too much calcium is not necessarily better, as it can inhibit the absorption of other nutrients such as iron and zinc, can cause heart attacks due to hardening of artery walls, and can cause gastric upset.

Summary

  1. Kale, broccoli, bok choy (and other dark leafy greens) almond butter, chia seeds, fortified soy/plant-based milks and calcium set tofu are excellent sources of calcium.
  2. Ensure you are getting enough vitamin D to optimize calcium absorption in the body.
  3. Aim to consume 2-3 servings of fortified plant-based milk or calcium-set tofu per day.
  4. Only consider a calcium supplement if you are not able to meet your needs with food first. Do not take more calcium than necessary.

As always, please consult your physician or registered dietitian if you have any concerns about bone health/calcium intake.

Want to Learn More?

Complete Guide to Weekly Grocery Shopping

Facts on Fats- My Philosophy on Fats and Oils

The Beef on Soy- Debunking Common Soy Myths

Common Plant-Protein Myths Debunked

Other References

Davis, B., & Melina, V. (2014). Becoming Vegan: The Complete Reference to Plant-Base Nutrition. Book Publishing Company.

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