Calcium on a Plant-Based Diet

Calcium and bone health

Calcium is a mineral found in food, and it's important to obtain calcium from our diet for the structural integrity of our bones. We achieve our peak bone mass at around 20 years of age, and after this, our bone density gradually declines. Although we can't stop the decline from happening, we can slow it down by making sure we get enough calcium from our food.

Calcium recommendations

Obtaining calcium from foods is always recommended over supplementation, where possible.

It is absolutely possible to obtain all calcium needs solely from food, at the exclusion of any animal products or direct supplementation.

The general calcium recommendations are:

• Adults < 50 years: 1000 mg calcium daily
• Adults > 50 years: 1200 mg calcium daily
• Maximum: stay below 2000 mg/day from food + supplement combined

Plant-based calcium sources

The following is a simplified summary of how we can meet the recommended amounts from food:

• 300 mg/day is commonly offered by a well-balanced diet, excluding calcium-rich foods. This comes from little contributions that add up, and includes ingredients such as dark green vegetables such as spinach, chard, kale, broccoli, almonds, and the white part on the outer layer of oranges.
• 700 – 900 mg/day is to be consumed from calcium-rich food sources. A list of these foods is shared below.

200-300 mg elemental calcium (per serving)

• Black beans, uncooked (1 cup)
• Bok choy or kale, cooked (1 cup)
• Tofu, extra firm, in calcium sulphate brine (1 cup)
• Tofu, pressed, in calcium sulphate brine (½ cup)
• Fortified orange juice (1 cup)
• Fortified rice, soy, almond, coconut milk (1 cup)
• Fortified rice, soy, almond, coconut yogurt (¾ cup)

100-200 mg elemental calcium (per serving)

• Cream of wheat, cooked (1 cup)
• Soybeans or white beans, cooked (1 cup)
• Broccoli, cooked (1½ cup)
• Kale, raw (½ cup)
• Almonds (½ cup)
• Dried fig (5 medium)
• Almond butter (2 tbsp)
• Sesame seeds, whole (2 tbsp)
• Tahini (2 tbsp)

Bottom line: the easiest way to achieve 700 - 900 mg of calcium per day is to aim to consume 2 - 3 servings of calcium-fortified foods per day.

• Adults under 50 years: aim for 2 servings of calcium-fortified non-dairy milk/yogurt or calcium-set tofu daily.
• Adults over 50 years: aim for 3 servings of calcium-fortified non-dairy milk/yogurt or calcium-set tofu daily.

Reading labels for calcium

When purchasing items that are packaged, such as plant-based milks, yogurts, tofu, or almonds, how can we know how much calcium is in each serving? According to Canadian guidelines, the following trick helps:

1. When reading a label, always look at the serving size first.
2. Skim down the label and find the % daily value of calcium (in this case 30%).
3. To know how many milligrams of calcium is in the serving size, simply add a ‘zero’ (in this case 300 mg).

Calcium absorption in plant-based foods

Calcium from fortified non-dairy drinks, non-dairy yogurts, and tofu are absorbed at the same rate and efficiency as those from cow's milk.

With that said, there are components naturally found in some plant-based foods that can interfere with calcium absorption. We'll briefly explore these two components, called oxalates and phytates.

Oxalates may negatively affect calcium absorption, but these foods should not necessarily be avoided. The benefits they offer far outweigh the small amount of calcium that is lost due to binding with these components. If you're concerned about calcium intake it's always best to speak with a healthcare professional. However, eating low-oxalate foods more often than high-oxalate foods may be beneficial though:

• Low-oxalate foods include broccoli, bok choy, kale, napa cabbage, watercress, mustard greens, and turnip greens.
• Medium-oxalate foods include collards and dandelion greens.
• High-oxalate foods include beet greens, spinach, and Swiss chard.

Due to the presence of phytates, absorption of calcium from beans and nuts is moderate, but again: some calcium is still absorbed and the overall nutrition offered by these foods is great, so no need to avoid them.

Tips to increase calcium intake

Lifestyle Factors That Diminish Calcium Stores

Addressing concerns surrounding plant-based milks

There are some circulating questions surrounding specific ingredients in store-bought plant-based milks. For example, there are some concerns over carrageenan and its effect on gut health. Carrageenan is a type of carbohydrate used in many dairy-based products for its thickening, gelling, and stabilizing properties. Essentially, it helps give plant-based milk the same creamy, thick texture as dairy milk. The evidence on this is a bit inconsistent, some claiming it to have potential health concerns, and others ensuring its safety. Many studies have not been done on humans and/or study very large concentrations (more than the average person would consume). Another carbohydrate called guar gum is used for the same purposes as carrageenan. Some studies are actually researching its possible effect of lowering cholesterol. Soy lecithin is another ingredient sometimes added to plant-based milks. This is a mixture of various lipids (fats) and is used in food products for its emulsification properties, essentially meaning it helps to keep particles in solution.

In addition, some readers ask, "Can we make our own homemade plant-based milk and dissolve a couple of calcium supplement tablets in there?" In theory, this sounds like a good idea, but there are a few concerns. There is little known about how these dissolved supplements will hold up in your homemade milk, as they may degrade or deteriorate. For some people, determining the dosage may be unprecise and even dangerous if too much is accidentally supplemented. There are many unknowns, and if you rely on plant-based milks and yogurts for a large portion of your calcium intake, it's better to be safe with store-bought plant-based milks that are regulated. As an added plus, these store-bought varieties are also commonly supplemented with vitamin D and vitamin B12. If you choose to make your own plant milks at home, though, it'd be preferred to simply take a supplement with your meal, rather than trying to dissolve it in your homemade milk.

Calcium supplements

It is recommended to obtain calcium from food sources over supplements wherever possible. This is because food sources provide added benefits such as energy, fibre, vitamins, minerals, and antioxidants. If it's not possible to obtain the recommended amount of calcium from food, then supplements may be taken. It's very important to note that more is not better though! Calculate your average daily calcium intake from food, and only supplement with the difference. Below are a few things to consider if taking supplements:

With supplementation, more is not always better!

• Multivitamins: remember these can also contain calcium - consider this when calculating your total intake.
• Reading labels: look for the word "elemental" on the supplement label when determining the amount of calcium it provides. If you have questions, ask a pharmacist.
• With food: take calcium carbonate and calcium phosphate with food. Other types of calcium can be taken anytime, with or without food.
• Max dose: avoid taking more than 500 mg in one dose as our bodies can't absorb calcium as efficiently in larger doses.
• Vitamin D: although it's true that vitamin D increases calcium absorption, it doesn't have to be taken at the same time as the calcium supplement. It can be taken at the same time if desired though.
• Supplement type: there is no difference in absorption if calcium supplements are liquid, chewable, or tablets.

Note that there are side effects of consuming too much calcium, especially when done over a long period of time. Taking too much calcium can increase the risk of heart attack and stroke due to excess calcium being deposited in our arteries, thereby hardening them. Also, excess calcium is hard on our digestive system and can cause constipation and bloating. These side effects haven't been as commonly documented when calcium is obtained solely from food, which is why food first is preferred.

If you do require a calcium supplement, check the label and note that calcium carbonate must be consumed together with food, while calcium citrate can be consumed on an empty stomach.

Summary

1. Eat a well-varied diet, especially once rich in dark green vegetables such as spinach, chard, kale, and broccoli daily. These offer just small bits of calcium, but the little bits add up!
2. If possible, soak raw nuts or seeds, and dry beans or lentils overnight to increase calcium availability.
3. Get enough vitamin D, from the sun or supplements.
4. Shake the container of your non-dairy milk and yogurt well to bring the calcium into suspension.
5. Aim to consume calcium from foods first. Consume 2 servings (if under 50 years old) to 3 servings (if over 50 years old) of fortified non-dairy milk/yogurt or calcium-set tofu daily.
6. Limit salt, caffeine, and alcohol intake and try to refrain from smoking.
7. Avoid calcium supplements unless unable to achieve the above recommendation. Do not take more supplements than what is needed to avoid harmful side effects and potential complications.
8. Consult with a local registered dietitian or with your family physician if you have any concerns surrounding your bone health and/or calcium in your diet.

Want to learn more?

As mentioned, calcium is especially important for bone health. Learn more about how insufficient calcium, and other factors, can lead to osteoporosis in our PUL article on bone health, or learn more about the important role vitamin D plays in bone health as well.