Fiber saves some antioxidants for later

U. QUEENSLAND (AUS) — Fiber helps protect the colon from cancer by transporting antioxidants to the large intestine, say researchers.

The study finds that fiber binds up to 80 percent of cancer-inhibiting antioxidant polyphenols in fruit and vegetables, which protects the antioxidants from early digestion in the stomach and small intestine.

Anneline Padayachee, who undertook the study through the University of Queensland and CSIRO, found that fiber acts as an antioxidant trafficker by safely transporting antioxidant nutrients to the colon where they can provide protection against cancers such as colon cancer.


“Cells in fruits and vegetables are ‘opened’ allowing nutrients to be released when they are juiced, pureed, or chewed,” says Padayachee.

“In an unexpected twist, I found that after being released from the cell 80 percent of available antioxidant polyphenols bind to plant fiber with minimal release during the stomach and small intestinal phases of digestion.

“Fiber is able to safely and effectively transport polyphenols to the colon where these compounds may have a protective effect on colon health as they are released during plant fiber fermentation by gut bacteria.”

This finding also has implications for fresh juice lovers who are throwing out antioxidants along with the fiber-rich pulp they discard.

“In juicing, the fibrous pulp is usually discarded, which means you miss out on the health benefits of these antioxidants as well as the fiber,” says Padayachee, whose findings appear in Food Chemistry.

“As long as you consume everything—the raw or cooked whole vegetable or fruit, drink mainly cloudy juices, and eat the fibrous pulp—you will not only have a clean gut, but also a healthy gut full of protective polyphenols.”

The original carrot

Padayachee used black carrots, which are rich in two antioxidant polyphenols—anthocyanins and phenolic acids—as a model system in her research to assess why plant-based diets generally result in better gut health.

Black carrots are the original carrot from which the now more common orange carrot was bred. Still cultivated in southern Europe and Asia, black carrots are having a bit of a comeback as a source of natural food coloring and also as a fresh vegetable in grocery stores, where they are often mislabeled as purple carrots.

Black carrots are one of the highest sources of anthocyanins—the antioxidant polyphenol that creates the purple-red pigment in blueberries and raspberries—and have been found to display potent antioxidant behavior.

Researchers at the Center for Nutrition and Food Sciences are conducting further researcher to assess the mechanisms involved with fiber binding polyphenol antioxidants.

Source: University of Queensland