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Many plant-based foods contain calcium
Can we get enough calcium without dairy? The short answer is yes, without a doubt.
However, we cannot assume that ALL plant-based diets provide enough calcium. Plant-based diets need to be designed to include adequate calcium sources, especially for children and teens who have high needs while they are growing.
It is also important to recognize that calcium intake is notthe only factor affecting the body’s calcium balance - calcium absorption and excretion (what is lost mainly in urine and feces) also come into play.
There are three important steps we can take to help ensure excellent calcium statuson a dairy-free, plant-based diet.
1. Load up on plant sources of calcium
Aim to meet the recommended intake which varies from about 700 to 1300 mg, depending on your age and country of origin. The best plant sources of calcium include:
· low oxalate, dark, leafy greens (e.g. bok choy, broccoli, Chinese greens, kale, mustard greens, Napa cabbage, turnip greens, watercress)
· calcium-fortified plant-based foods(e.g. calcium-fortified non-dairy milks, cereals, juices)
· Tofu made with calcium (compare calcium content on labels)
· Nuts and seeds (especially almonds, chia seeds,sesame seeds)
· Blackstrap molasses
From low-oxalate greens, we absorb about 40-60 percent of the calcium present.
Absorption of calcium is about 30-32 percent in tofu and nondairy milks, which is comparable to cow’s milk. We absorb an estimated 50 percent of the calcium in fortified orange juice, and around 20 percent from almonds, tahini, beans, and sweet potatoes.
(See the table below for the calcium content of common foods).
2. Be aware of inhibitors of calcium absorption
Some foods contain plenty of calcium, but due to the presence of oxalates (a key inhibitor of calcium absorption), the calcium is largely unavailable. Oxalates are tightly bound combinations of oxalic acid and minerals (e.g. calcium) that resist breakdown during food preparation and digestion.
Spinach is a good example of a high oxalate green.It provides 243mg calcium per cup of cooked spinach, however, because of its high oxalate content, we only absorb about five percent of what is present.
The story is similar for other high oxalate greens such as beet greens and Swiss chard. Some greens such as collard and dandelion greens have medium oxalate content, so we absorb intermediate amounts of calcium. If you use higher oxalate greens such as spinach in a salad, the oxalates from the spinach do not interfere with the absorption of calcium from lower oxalate greens such as kale.
Boiling high-oxalate greens can reduce oxalate content by 30 to 87 percent, depending on the boiling time. Steaming is less effective (five to 53 percent reduction), and dry- heat cooking appears to have little impact on oxalate content. Other factors that can either reduce calcium absorption or increase calcium excretion are phytates, sodium, caffeine, alcohol.
3. Get familiar with the enhancers of calcium absorption
Vitamin D has long been recognized for its role in boosting calcium absorption. Protein also enhances calcium absorption, although high intakes increase calcium excretion.
While getting sufficient protein is important, very high intakes can be problematic, especially in the face of low calcium intake (e.g. as often seen with “paleo”diets). Fruits and vegetables reduce calcium excretion so are protective.
The efficiency of absorption is decreased as calcium intake increases. In addition, calcium absorption is high in infants and young children, and it decreases as we age. It can be challenging to meet the calcium RDA for some individuals. The following tips can help us reach our calcium intake goals when following plant-based diets:
1. Add one to two cups of fortified non-dairy milk (or other fortified foods) each day. The calcium content of fortified non-dairy milk is generally similar to that of cow’s milk (read the label).
2. Use calcium-set tofu. The range of calcium in tofu is significant. Compare labels and select a product with more calcium.
3. Make low-oxalate greens a part of the daily diet, and preferably include them at least twice a day. Add them to salads, rolls, smoothies, stir fries, soups, stews, side dishes, sandwiches, and veggie and dip trays.
4. Include calcium-rich choices within each food group.
a. Vegetables - low-oxalate greens, broccoli, okra, yams
b. Legumes - black turtle beans, edamame, great Northern beans, navy beans, soybeans, white beans
c. Nuts and seeds - almonds and almond butter, chia seeds, tahini
d. Fruits - oranges, figs
e. Grains - amaranth, tortillas (with added calcium)
5. Use blackstrap molasses in place of other sweeteners, when possible.
This article was written by Brenda Davis, RD. It is adapted from the soon-to-be-released book, Nourish: TheDefinitive Plant-based Nutrition Guide for Families, by Reshma Shah, MD and Brenda Davis, RD.