Kale has a reputation for being one of the most nutritious vegetables you can eat. But a new study from the University of Missouri suggests you may not be getting the full benefit if you eat it on its own.
The research, published in Food Nutrition, looked at how well nutrients called carotenoids become available during digestion when kale is prepared in different ways. These plant compounds support eye health and immune function, but they’re fat-soluble, which means the body absorbs them more easily when a source of fat is present.
“Kale is a nutrient-rich vegetable that contains carotenoids, including lutein, α-carotene and β-carotene, which have beneficial effects on overall health,” said Ruojie (Vanessa) Zhang, assistant professor in the Division of Food, Nutrition and Exercise Sciences. “The problem is our bodies have a hard time absorbing these nutrients because they are fat-soluble rather than water-soluble.”
To test practical ways to improve absorption, researchers used a laboratory model that simulates digestion. They compared raw kale, cooked kale and kale paired with oil-based dressings or sauces.
The biggest improvement came from adding fat. Whether the kale was raw or cooked, pairing it with an oil-based dressing or sauce led to much higher levels of carotenoids being released during digestion. Cooking the kale on its own did not improve absorption.
The study also tested a specialized sauce designed in the lab, but everyday options like olive oil, mayonnaise or an oil-based dressing were effective in the model.
The findings reinforce a simple idea: adding a little fat can help your body make better use of the beneficial nutrients in leafy greens. While the study used a simulated digestion system rather than human participants, the results align with what scientists already know about fat-soluble nutrients.
Zhang hopes the research will help guide both home cooks and future food products.
“Our team is committed to advancing food science with the goal of improving human health through the development of innovative foods and technologies,” she said.
This study was supported by the University of Missouri and collaborating institutions. One author, Zipei Zhang, serves on the editorial board of Food Nutrition but was not involved in the review or publication decision for this article.