Question: Is it true that some dark leafy greens, such as collard greens, have as much calcium as milk? I’ve heard that the calcium in dark leafy greens is not as “bioavailable.” I understand that to mean that your body cannot use it as easily or readily as the calcium in milk products. What’s the whole story?
Answer: Yes, calcium from some foods is more easily absorbed by the body, because other components of the food may increase or inhibit absorption. The calcium in both dairy products and some leafy greens is considered the most bioavailable, because the body is able to absorb and utilize most of this naturally-occurring nutrient. Here are some examples of calcium-rich foods and how well the body can use them:
| FOOD | CALCIUM CONTENT | BIOAVAILABLE? |
| 1 cup milk or yogurt | 300 mg | Yes |
| 1 oz cheese | 200 mg | Yes |
| 1 cup soy milk | 300 mg | Somewhat |
| 1 cup fortified orange juice | 300 mg | Somewhat |
| 1 cup cooked kale, mustard or collard greens | 180 mg | Yes |
| 1 cup broccoli | 50 mg | Yes |
| 4 oz canned salmon (with bones) | 240 mg | Yes |
| 4 oz cooked salmon filet | 20 mg | Yes |
| 1 cup lentils or beans | 50 mg | Not really, because fiber will limit calcium absorption |
| 1 cup cooked Spinach or Swiss Chard | 120 mg | No, because oxalic acid in these greens prevents calcium absorption |
Things that Increase Calcium Absorption
Vitamin D (15 minutes in the sun or a 400 IU daily supplement will help)
Lactose (why dairy is such a good source)
Protein (why fish with bones, some beans are good sources)
Things that Inhibit Calcium Absorption
Oxalic Acid, found in spinach, Swiss Chard, berries, nuts, tea, and cocoa (these foods will not only not provide calcium, they’ll also prevent the absorption of calcium from other foods if they’re present in the GI tract at the same time)
Fiber and Phytic Acid found in fiber and legumes
What About Fortified Foods?
Fortified soy milk, almond milk, orange juice, energy bars, etc can be good sources of calcium, but they’re not as well-used by the body as naturally-occurring sources like dairy.
Moral of the Story
Best to get most of your calcium from dairy products, broccoli, and leafy greens like kale, mustard greens, collards, turnip greens, and beet greens.
4 Comments
Bridget
December 26, 2011 at 6:16 amJust read this article again, needed some help with my calcium intake. I also need to learn more about beans. I want to make a black bean soup, any recommendations? Do you prefer soaking overnight or the fast method? Dried beans taste better and have a great texture. Besides less sodium, what are some of the other major nutritional benefits to using dried beans versus canned?
Amelia
December 26, 2011 at 9:55 amI would say that dried beans are better because they’re 1) much cheaper and less wasteful packaging-wise, 2) lower in sodium, 3) you can make a big batch and use them for many different things throughout a given week! I love using black beans in a “burrito bowl” like this and in veggie chili
aj
May 24, 2015 at 10:32 pmDried beans are better in terms of health. I’ve read internet articles saying using canned beans are less healthy because they’re more processed with additives, can be older giving less nutrients, picked earlier giving less nutrients, and the can itself (the plastic coating in the can/ aluminium leaks) can give it nasty additives. I value my health too much to use cans despite their convenience and yummy sugar.
Amelia Winslow
May 26, 2015 at 10:18 amYou can also look for canned beans that are organic, low-sodium, and just have “beans, water and salt” as the ingredients — if you buy organic these are usually the only ingredients.