Microgreens and mature veggies differ in nutrients, but both might limit weight gain

The researchers presented their results at the fall meeting of the American Chemical Society (ACS). ACS Fall 2023 is a hybrid meeting being held virtually and in-person and features about 12,000 presentations on a wide range of science topics.

"The scientific literature suggests that cruciferous vegetables, like kale and broccoli, are good for you," notes Thomas T. Y. Wang, Ph.D., the project's principal investigator. The microgreen versions of these foods are particularly touted for their health benefits. Older than sprouts but younger than baby greens, microgreens are typically harvested within a couple of weeks after they start growing. And they can easily be grown in a container on a windowsill.

"When we started this research, not a lot was known about the nutrient content or biological effects of microgreens, so we thought we should take a look at them," says Wang, a scientist at the Agricultural Research Service of the U.S. Department of Agriculture (USDA). He is working with collaborators there and at the University of Maryland, College Park.

The team began their studies with another cruciferous plant -- red cabbage. The researchers found that both young and fully grown cabbage limited weight gain in mice fed a high-fat diet. Yet the cabbage's nutrient profile changed over time, and the microgreen was significantly richer in substances such as glucosinolates -- nitrogen- and sulfur-containing compounds that may offer protection from cancer, Wang says.

Next, the scientists turned their attention to kale. "We wondered whether the bioactive components in microgreen kale were different from those in mature kale," says Wang. "And we found that the nutritional composition is very different." For example, the immature plant has about five times more glucosinolates. Similarly, further studies by Wang's team and others have shown that nutrient levels in several other types of cruciferous vegetables are higher in the immature plants.

In their latest work, Wang and his colleagues are comparing the biological effects of microgreen and fully-grown kale. They have discovered that both the young plant and mature kale are effective in limiting weight gain in mice fed a high-fat diet. Additional experiments will be needed to see if humans would experience these same benefits.

Wang believes the weight effects in mice may in part be related to the vegetable's impact on the animals' "microbiome," or the community of bacteria in the gut. Consumption of kale, regardless of its maturity, increases the variety of gut bacteria, the researchers have discovered. However, that enhancement is more pronounced with microgreens. That's important because greater bacterial diversity is generally associated with better health, Wang notes.

In future work, the team will continue to study the impact of other cruciferous plants on health. Those findings could help guide diners who dislike some of these foods but are seeking alternatives that taste better to them. "For instance, for people who don't like broccoli," Wang says, "can we find some other vegetable they like better that has similar health effects?"

It's also possible that the flavor profiles of these vegetables could be altered to make them more palatable. Some of the health-promoting constituents responsible for their characteristic flavor -- such as glucosinolates -- are bitter, but Wang speculates that these compounds might be present at higher levels than are necessary to reap health benefits. If that's the case, he says, these crops could potentially be bred to reduce those levels and the associated bitterness.

The researchers acknowledge support and funding from USDA and the National Cancer Institute.