When It Comes to Red Cabbage, More Is Better

Plant pigments called anthocyanins provide fruits and vegetables with beneficial blue, purple and red coloring. Now Agricultural Research Service (ARS) scientists are learning more about these compounds and their absorption into the human blood stream.

Anthocyanins are a group of healthful compounds that fall within the flavonoid class of plant nutrients. ARS scientists have identified 36 anthocyanins in red cabbage, including eight that had never before been detected in the cabbage.

The study was conducted at the ARS Beltsville Human Nutrition Research Center (BHNRC) in Beltsville, Md., where scientists have pioneered methods for identifying and measuring various phytonutrients in fruits and vegetables. Physiologist Janet Novotny, nutritionist Beverly Clevidence, plant physiologist Steven Britz and research associate Craig Charron, all with the BHNRC's Food Components and Health Laboratory, published the findings in the Journal of Agricultural and Food Chemistry.

Emerging evidence suggests that anthocyanins may provide cancer protection, improve brain function and promote heart health. An earlier ARS study showed that some anthocyanins yield twice the antioxidant power of the same amount of vitamin C in test tubes, though the amount absorbed by the human body was not explored.

Twelve volunteers consumed three different amounts of cooked red cabbage along with a full diet of carefully controlled foods. Each volunteer completed three two-day meal regimens, which included 2/3 cup, 1-1/3 cups, or 2 cups of red cabbage. The volunteers were capable of absorbing the most anthocyanins when given the largest serving of cooked cabbage.

Interestingly, the anthocyanins that the researchers identified were not equally absorbed, as measured by the portion of the ingested compound that reached the blood stream. Nearly 80 percent of cabbage anthocyanins tested were "acylated," meaning attached to acyl groups, which made them more stable and less absorbable. The non-acylated anthocyanins present were at least four times more bioavailable, or absorbed, than the acylated anthocyanins.

The findings could aid plant breeders in developing varieties with key anthocyanin structures and amounts.

ARS is the U.S. Department of Agriculture's chief scientific research agency.