Does kale have more calcium than milk?
The claim: Kale has more calcium than milk.
Last checked 16 October 2026
Gram for gram, yes: kale, raw or cooked, holds more calcium than milk, and your body absorbs kale's calcium at least as well as milk's. Cup for cup, no: a cup of raw kale weighs a fraction of a cup of milk, so it takes several cups of raw kale, or a little more than a cup of cooked kale, to match the calcium absorbed from a cup of milk.
Spinach is the exception: very little of its calcium gets absorbed. The table below shows calcium per 100 g, per cup, and what the studies found you absorb.
How well kale's calcium is absorbed
Researchers gave women kale and milk, each labelled so the calcium could be traced, and measured how much they absorbed:
Absorption of calcium from intrinsically labeled kale was measured in 11 normal women and compared in these same subjects with absorption of calcium from labeled milk.
Fractional calcium absorption from kale averaged 0.409 +/- 0.101 (means +/- SD) and from milk, 0.321 +/- 0.089 (P less than 0.025).
The fraction is the share absorbed: about two-fifths for kale, about a third for milk. The authors contrasted kale with spinach:
In contrast with the poor absorption previously reported for spinach calcium, kale, a low-oxalate vegetable, exhibits excellent absorbability for its calcium.
Why spinach is different
The same team had earlier tested spinach against milk:
Measurement of both Ca and oxalate in our test spinach revealed a very slight stoichiometric excess of oxalate; hence it is likely that all of the spinach Ca was effectively bound.
Absorption was higher from milk in every case, with the mean absorption from milk averaging 27.6% and from spinach, 5.1%.
Ca is calcium. Oxalate binds calcium into a form the gut barely takes up; our spinach page covers oxalate in more detail.
At a smaller dose
The share absorbed changes with the size of the dose. A later study by the same team used a much smaller test dose, closer to the calcium in a cup of raw kale:
The test load of calcium was about 83 mg for each source.
Fractional calcium absorption from broccoli averaged 0.478 ± 0.089, from bok choy stems, 0.519 ± 0.089, from bok choy leaves, 0.520 ± 0.074, and from kale 0.527 ± 0.091.
Mean absorbability of milk calcium ingested at the same load has been previously shown to be 0.463 ±0.095.
That milk figure comes from earlier work at the same dose, not from the same women, so we keep it out of the table. It suggests the table's raw kale row, worked out from the larger dose, is on the cautious side.
Gram for gram, cup for cup
Each vegetable is compared only with the milk measured in the same study, in the same people. Each study tested one dose of calcium, shown in its heading, and applying its share to a whole cup is an approximation. Calcium figures are USDA's.
| Food and portion | Calcium per 100 g | Calcium in the portion | Share absorbed in the study | Calcium absorbed | Portions to match a cup of milk |
|---|---|---|---|---|---|
| Kale and milk, same women, same test load (Heaney and Weaver, 1990; average test load 300 mg calcium) | |||||
| Milk, whole, 1 cup (244 g) | 113 mg | 276 mg | 32.1% | 88.5 mg | — |
| Kale, raw, 1 cup (21 g) | 254 mg | 53.3 mg | 40.9% | 21.8 mg | 4.06 |
| Kale, boiled, 1 cup (118 g)1 | 150 mg | 177 mg | 40.9% | 72.4 mg | 1.22 |
| Spinach and milk, same people, same test load (Heaney, Weaver and Recker, 1988; 200 mg calcium in each test meal) | |||||
| Milk, whole, 1 cup (244 g) | 113 mg | 276 mg | 27.6% | 76.1 mg | — |
| Spinach, raw, 1 cup (30 g) | 99 mg | 29.7 mg | 5.1% | 1.51 mg | 50.2 |
| Spinach, boiled, 1 cup (180 g)2 | 136 mg | 245 mg | 5.1% | 12.5 mg | 6.1 |
- The abstract doesn't say whether the test kale was raw or cooked; the same fraction is applied to both.
- As for kale, the abstract doesn't say how the test spinach was prepared.
The abstracts don't say whether the test vegetables were raw or cooked, so the absorbed figures are a guide, not a measurement of your cup. A cup of raw kale is mostly air; cooked, the same cup holds far more leaf.
What you'll hear at the table
Here is each calcium claim, checked against its source.
You'll hear: Kale has more calcium than milk.
Partly holds up
Per 100 g, yes, raw or cooked. Per cup, no: a cup of raw kale is light, and a cup of cooked kale still holds less calcium than a cup of milk (see the table).
Fractional calcium absorption from kale averaged 0.409 +/- 0.101 (means +/- SD) and from milk, 0.321 +/- 0.089 (P less than 0.025).
You'll hear: Your body absorbs calcium from plants badly.
Partly holds up
It depends on the plant. Spinach's calcium is barely absorbed; kale's is absorbed at least as well as milk's.
Absorption was higher from milk in every case, with the mean absorption from milk averaging 27.6% and from spinach, 5.1%.
In contrast with the poor absorption previously reported for spinach calcium, kale, a low-oxalate vegetable, exhibits excellent absorbability for its calcium.
You'll hear: Spinach is a great source of calcium.
Doesn't hold up
It carries plenty on paper, but its oxalate binds nearly all of it.
These results conclusively establish that spinach Ca is much less readily available than milk Ca.
You'll hear: You can't get enough calcium from plants alone.
Partly holds up
You can in principle, but a review by the same research group found it takes so many vegetables that most people would need fortified foods or supplements.
Some plants provide absorbable calcium, but the quantity of vegetables required to reach sufficient calcium intake make an exclusively plant-based diet impractical for most individuals unless fortified foods or supplements are included.
The referee's verdict
- Right, for the kale eater: gram for gram, kale has more calcium than milk, and in the studies that compared them, the body absorbed kale's calcium at least as well as milk's.
- Right, for the milk drinker: cup for cup, milk holds more calcium than kale and delivers more absorbed calcium than raw kale, with cooked kale coming close; and spinach's calcium is mostly locked away by oxalate.
- Not settled: whether the test vegetables were raw or cooked; the abstracts don't say, and we couldn't read the full papers.
Try it with your own plate
See what a cup of kale gives you, and what comes with it.
Sources
- Heaney RP, Weaver CM (1990). Calcium absorption from kale. Am J Clin Nutr 51(4):656–7. doi:10.1093/ajcn/51.4.656. (opens in a new tab)Evidence: Human trial. Eleven women, kale and milk each traced with a calcium label.Read: PubMed abstract, in Chrome
- Heaney RP, Weaver CM, Recker RR (1988). Calcium absorbability from spinach. Am J Clin Nutr 47(4):707–9. doi:10.1093/ajcn/47.4.707. (opens in a new tab)Evidence: Human trial. Thirteen adults, a randomised cross-over test of spinach and milk.Read: PubMed abstract, in Chrome
- Weaver and colleagues (1999). Choices for achieving adequate dietary calcium with a vegetarian diet. Am J Clin Nutr 70(3 Suppl):543S–548S. (opens in a new tab)Evidence: Not applicable. A review by the same research group.Read: PubMed abstract, in Chrome
- USDA FoodData Central, SR Legacy: milk, whole 171265 (linked); kale raw 168421 and boiled 169238; spinach raw 168462 and boiled 168463 (each on its own food page). (opens in a new tab)Evidence: Measured in foodRead: SR Legacy CSV in the repo
- Heaney RP, Weaver CM, Hinders SM, Martin B, Packard PT (1993). Absorbability of calcium from Brassica vegetables: broccoli, bok choy, and kale. Journal of Food Science 58(6):1378–1380. doi:10.1111/j.1365-2621.1993.tb06187.x. (opens in a new tab)Evidence: Human trial. Fifteen women; milk from earlier work at the same dose.Read: Creighton University repository abstract, in Chrome