Making ‘Superfoods’ Prove It

Microgreens started as fodder for upscale restaurants and have grown in popularity among gardeners looking to add a pop of color to windowsills or home cooks eager to include a nutrient-rich “superfood” to recipes. But despite their healthful reputation, most varieties of microgreens contain unknown amounts of beneficial compounds like phytonutrients.

Recent research shows that “super” might be an accurate description. In a study published in ACS Food Science & Technology, scientists from the University of Maryland and the Agricultural Research Service (ARS) at the U.S. Department of Agriculture in nearby Beltsville, Md., found that kale and broccoli microgreens grown both in windowsills and in commercial growing conditions are rich in phytonutrients—natural chemicals that protect plants and can benefit human health—though the levels of some compounds varied considerably between the two environments.

Beyond their fashionable status, microgreens' higher nutritional value compared to conventional vegetables of the same type can make "getting your vegetables" significantly less labor-intensive, said study co-author Liangli Yu, a professor in the Department of Nutrition and Food Science. 

"This can have a lot of importance if you're talking about feeding young kids ... it can be easier for young consumers to accept them than conventional vegetables," she said.

The microgreens industry is rapidly expanding, with the $1.4 billion annual global market in 2020 expected to reach $3.8 billion by 2028. The most popular varieties of microgreens are from the Brassica family, which includes broccoli, kale, cabbage and mustard. The mature, fully grown versions of these vegetables are rich in vitamins, minerals and phytochemicals; in an earlier study, the researchers observed that red cabbage microgreens beat out full-grown cabbage for levels of phytonutrients that have been reported to have antioxidant and anticancer properties. However, similar assessments hadn’t been done on other Brassica seedlings, including broccoli and kale.

To test different growing conditions, the researchers placed trays of newly planted broccoli and kale seeds either on a windowsill in natural sunlight or inside a temperature- and humidity-controlled refrigerator-like growth chamber with artificial sunlight for 12 hours a day. Ten days after seeding, the team harvested the plants and assessed the phytonutrient content with a liquid chromatography high-resolution mass spectrometry system.

The broccoli and kale microgreens were rich in dietary polyphenols and glucosinolates, no matter how they were grown. But three flavanol compounds that contribute to the plant’s dark color and bitter taste were higher in windowsill-grown microgreens. Research has found flavanols can have beneficial anti-inflammatory and cardiovascular effects.

Meanwhile, chamber-grown plants had higher levels of two glucosinolates, which are antioxidant- and anticancer-related compounds. Overall, the growth environment for kale and broccoli microgreens affects the abundance of individual phytonutrients, the researchers said, which could affect their flavor and potential health benefits.

"You can't simply say that growing it at home or growing it commercially is superior," said Yu, a fellow of the American Chemical Society (ACS) as well as  fellow and past chair of the ACS's Agricultural and Food Chemistry Division. "The nutrient level depends on many conditions"—so both growing environments can produce foods that qualify as "super."

This article is based on an American Chemical Society news release.