Microgreens and mature veggies differ in nutrient content

Young vegetables known as microgreens are reputed to be particularly good for health — now, researchers are trying to find out how microgreens compare to mature veggies. Their results to date were presented at ACS Fall 2023, the August meeting of the American Chemical Society (ACS).

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. The microgreen versions of cruciferous vegetables, like kale and broccoli, are particularly touted for their health benefits.

“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,” said principal investigator Dr Thomas TY Wang, a scientist at the Agricultural Research Service of the US Department of Agriculture (USDA).

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 said.

Next, the scientists turned their attention to kale. Wang said the nutritional composition of microgreen and mature kale was found to be “very different”, with the immature plant containing about five times more glucosinolates. Further studies 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 said.

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.

It’s also possible that the flavour profiles of these vegetables could be altered to make them more palatable. Some of the health-promoting constituents responsible for their characteristic flavour — 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 said, these crops could potentially be bred to reduce those levels and the associated bitterness.

Image caption: Kale microgreens (left) and leaves from the mature plant (right) have different nutritional profiles but both can limit weight gain in mice. Image credit: Thomas Wang/USDA.