Calcium. We all need this massive and important mineral and it’s no surprise that many people – omnivores and plant-based eaters alike – fall short of meeting calcium needs. Inadequate calcium intake can lead to poor bone health. Let’s look at calcium requirements, bioavailability, and then talk about where to find calcium in a vegan diet.
Calcium Requirements and Bioavailability
The Institute of Medicine (the government agency that establishes the RDAs) and the World Health Organization recommend 1,000 mg of calcium per day for all adults over 18 years old and 1200mg for those over 50 years old.
It’s more about how much calcium you absorb compared to how much you consume. Interestingly, people generally consume about 30% of the calcium in the diet. If you’re meeting your RDA of 1000mg calcium, you may be absorbing about 300mg per day which does seem to meet the needs of many people. There are many factors that affect how much calcium we actually absorb including:
- Sodium consumption – high sodium intake decreases calcium in the body by increasing calcium excretion
- Caffeine consumption – high caffeine consumption can increase the amount of calcium excreted in the body
- Alcohol consumption – alcohol can also interfere with the absorption process of calcium
- Phytic acid and Oxalic acid – these are naturally found in some foods like spinach and whole grains and can impair the amount of calcium absorbed but is highly variable
- Vitamin D – this helps to increase amount of calcium absorbed
- Fruit and vegetable consumption – a diet high in fruits and vegetables can help to neutralize many of the acids in the body that decreases calcium excretion in the body
- Age – as we age, calcium absorption decreases
Given the above factors, calcium from plant-based foods can be absorbed anywhere from 5-70%! That’s a huge range and usually when I counsel plant-based eaters on increasing calcium, I focus on the vegan calcium sources that are also easily bioavailable to help ensure needs are being met.
When thinking about this large range, there are some common threads that may be helpful to know:
- Many leafy greens are high in calcium. However, many are high in that oxalic acid I mentioned earlier that binds to the spinach and makes it less likely to be absorbed. High oxalate vegetables that are fantastic but shouldn’t be considered a calcium source include spinach and beet greens (which I’m sure are your favorite!).
- Kale, collard greens and other greens like mustard greens and turnip greens (also your favorite I’m sure!) are low in oxalates and calcium can easily be absorbed in these greens (estimated that 50% is absorbed from these vegetables).
- Beans have variable amounts of calcium that isn’t well absorbed unless you soak them ….however the exception is edamame and soy beans in general which is easier absorbed.
- Speaking of soy, tofu is often set in calcium sulfate which means that it can be a good source of calcium but depending on the brand and how it’s prepared, the amount can vary significantly although well absorbed.
- Calcium carbonate is the form of calcium added to many plant-based milks and similar to cow’s milk, only about 30% of that is absorbed.
What this might look like….aka Good Sources of Vegan Bioavailable Calcium
Again, because absorption can vary, it’s important to try and consume multiple sources (at least 3 servings) of bioavailable vegan calcium foods per day instead of 1 large glass of plant-based milk in the morning and calling it good. No one has the time to track absorption rates and the information isn’t as black and white as you think it might be so again, go for a varied diet with at least 3 cups of calcium rich foods per day (vegan or not).
Rich Vegan Calcium Sources that are Highly Absorbed:
- 1 cup cooked bok choy
- 1 cup cooked collard greens
- 1 cup cooked kale (any variety)
- 1 cup cooked turnip greens
- 1 cup cooked mustard greens
- 1 cup cooked tofu set in calcium sulfate
- 1 cup fortified plant-based milk
- 1 cup fortified orange juice
Other foods you may be consuming will have smaller amounts of calcium and will help make up the difference. Vegan foods like almonds, beans, sweet potatoes, okra, and others. However, if you don’t eat these foods often or regularly, taking a 300mg calcium citrate supplement may be a good idea and absorption from calcium citrate supplements is generally pretty good. If you regularly take a calcium supplement, take it with a meal to avoid kidney stones.
Vegans like omnivores cannot forget about calcium but with a bit of planning ahead, it’s easy to get enough. If you have questions about calcium in the vegan diet, comment below!