Kale

Studies in people

• Benefit

  Understudied vegetable nutrition²

  Kale is rich in vitamins, minerals and fiber, but scientists have not studied its nutrition much.

• Benefit

  Skin aging⁴

  In people, taking curly kale extract daily for months raised skin carotenoids and improved the collagen aging index.

• Benefit

  Calcium absorption from food⁵

  In women, the body absorbed more calcium from kale than from milk in the same test.

• Benefit

  Blood clotting in metabolic syndrome⁷

  In people with metabolic syndrome, kale extract reduced a marker of platelet activation.

• Benefit

  Blood sugar control in diabetes⁹

  In people with type 2 diabetes, eating kale bars daily for 12 weeks improved blood sugar control and insulin resistance.

• Benefit

  Cholesterol and heart risk¹⁰

  Men with high cholesterol who drank kale juice daily saw better cholesterol numbers and antioxidant levels.

Animal and lab studies only

• Benefit

  Blood sugar control¹⁴

  In animal studies, an apple and kale extract improved blood sugar levels in mice fed a high-sugar, high-fat diet.

• Benefit

  Heart and blood vessel health¹⁵

  Kale and spinach both contain omega-3 fats, which may help lower the risk of heart and other chronic diseases.

• Benefit

  Health compounds in vegetables¹⁶

  Chopping kale released the fewest helpful compounds, and microwaving did not change the release of indole-3-carbinol from kale.

• No harm found

  Blood vessel health¹⁸

  Kale did not change the blood vessel health markers tested.

Study type not stated

• Benefit

  Heart and blood sugar health¹¹

  Kale contains compounds that studies link to lower risk of heart problems and type 2 diabetes.

Found in some samples or products

These come from where it was grown, how it was processed or cooked, or what it was made into. They are not about the ingredient itself, so the signal does not count them.

• Metal in a snack food⁸

  A family's high thallium levels were tied to kale chips, which contained thallium.

How it’s made and used

• Knowledge of leafy greens³

  In a Saudi survey, only 23% of people had eaten kale, and most knew little about it.

• Mineral absorption from food⁶

  People absorbed the molybdenum in kale as well as molybdenum added to the diet.

• Nutrients lost in cooking¹²

  Boiling, steaming, microwaving and pressure cooking all lowered kale's antioxidants and minerals, though steaming kept the most.

• Taste and keeping quality¹³

  Adding stevia to kale juice spheres made them taste less bitter and kept their quality during cold storage.

• Protein quality in cooked greens¹⁷

  Cooking, freezing and canning kale leaves lower their amino acids, but kale still supplies protein building blocks.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.