Kale nutrition and benefits: what the numbers really say

Instead of jumping to superlatives, start with the reference data. The U.S. Department of Agriculture’s FoodData Central lists raw kale at 35 kcal per 100 g, with 89.6 g of water, 2.92 g of protein, 4.42 g of carbohydrate, 1.49 g of fat and just 0.8 g of sugars. A kale leaf is mostly water and structure, which is why its micronutrients look so impressive relative to its energy.

Real leaves vary with variety, soil, season and storage, so treat every number as an order of magnitude. And keep the unit in mind: 100 g of raw curly kale is a large, airy bowlful, a little under half of a 250 g bag.

For a fuller tour of every value, see the per-100 g table on our nutrition page.

Vitamin K

Kale is one of the most concentrated vegetable sources of vitamin K. The body needs it for normal blood clotting, and it contributes to the maintenance of normal bones. It is also fat-soluble — one more reason kale and olive oil make such natural partners.

Vitamin C

100 g of raw kale covers roughly a full Daily Value of vitamin C. Vitamin C contributes to normal immune function and collagen formation, and helps the body absorb iron from plant foods. It is also heat-sensitive and water-soluble, so raw or briefly cooked kale keeps more of it than leaves boiled for a long time.

Vitamin A, by way of beta-carotene

Kale does not contain ready-made vitamin A; it contains beta-carotene (about 2,873 µg per 100 g), which the body converts into vitamin A. Expressed as retinol activity equivalents, that is 241 µg, or roughly a quarter of the Daily Value. Vitamin A contributes to the maintenance of normal vision and normal immune function.

• Calcium — 254 mg per 100 g. That is about 20% of the FDA Daily Value and about a quarter of the Codex reference value, enough to call kale a source of calcium. Kale is also low in oxalate, a compound that binds calcium in greens such as spinach, so its calcium is relatively well absorbed for a plant food.
• Fiber — 4.1 g per 100 g. About 15% of the Daily Value. Kale is a source of fiber, but not “high in fiber”: that label requires at least 6 g per 100 g under Codex guidelines. Fiber is part of a balanced diet and contributes to normal digestive function.
• Iron — 1.6 mg per 100 g. Kale contains iron, about 9% of the Daily Value. Plant iron is absorbed less readily than iron from meat, which is why the vitamin C in kale — and a squeeze of lemon — are helpful companions.
• Manganese, potassium, magnesium. About 0.92 mg of manganese (≈ 40% DV), 348 mg of potassium and 33 mg of magnesium, plus about 62 µg of folate.

Per 100 g, raw kale lists about 6,261 µg of lutein plus zeaxanthin, two carotenoids concentrated in the retina. The U.S. National Eye Institute’s AREDS2 trial tested them in a supplement formula for specific groups of people — supplement research that does not show eating kale protects your eyes.

Glucosinolates are the sulfur-containing compounds that define cruciferous vegetables, the family that includes kale, cabbage and broccoli. When leaves are chopped or chewed, glucosinolates break down into other compounds that researchers study closely. They are also part of why kale tastes slightly bitter — more on that in why kale tastes bitter.

1. 1

   Add fat

   Carotenoids such as beta-carotene and lutein are fat-soluble. Olive oil, tahini, nuts or cheese in the same dish help your body absorb them.

2. 2

   Add acid

   Lemon juice brightens the flavor and adds vitamin C, which helps plant-iron absorption — handy in dishes with lentils or chickpeas.

3. 3

   Mix raw and cooked

   Raw kale keeps the most vitamin C; quick cooking softens the leaves, so you may simply eat more. Both are good choices — see our cooking basics.

4. 4

   Eat the stems

   Finely chopped and cooked a little longer, stems add texture and fiber instead of going in the bin.

5. 5

   Think in variety

   The World Health Organization recommends plenty of different vegetables, fruits, legumes and whole grains. Kale is a welcome part of that, not a replacement for it.

Ideas to start with: kale tabbouleh, kale lentil soup or garlic-lemon sautéed kale.

Vitamin K plays a role in blood clotting, and some anticoagulant medicines, notably warfarin, work by counteracting it. That does not mean avoiding green vegetables. The usual advice is to keep vitamin K intake fairly steady from week to week, rather than suddenly eating much more or much less, and to talk to your healthcare professional before major dietary changes.

For the wider picture, read vitamin K in leafy greens. This article is general information, not medical advice — see our health disclaimer.