Fibre not only works as a 'bowel scourer', but may also help to protect the colon from cancer by transporting antioxidants to the large bowel, new Queensland research has found.
The world-first study discovered that fibre binds up to 80% of cancer-inhibiting antioxidant polyphenols in fruit and vegetables, thereby protecting the antioxidants from early digestion in the stomach and small intestine.
Dr Anneline Padayachee, who undertook the study through The University of Queensland (UQ) and CSIRO, found that fibre 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," Dr Padayachee said.
"In an unexpected twist, I found that after being released from the cell 80% of available antioxidant polyphenols bind to plant fibre with minimal release during the stomach and small intestinal phases of digestion.
"Fibre 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 fibre fermentation by gut bacteria."
This finding also has implications for fresh juice lovers who are throwing out antioxidants along with the fibre-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 fibre," Dr Padayachee said.
"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."
Dr 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 resurgence as a source of natural food colouring and also as a fresh vegetable in grocery stores, where they are often mislabelled 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 behaviour.
Dr Padayachee completed her PhD through UQ's School of Agriculture and Foods Sciences and undertook her research at the ARC Centre of Excellence in Plant Cell Walls and the Centre for Nutrition and Food Sciences at UQ's Queensland Alliance for Agriculture and Food Science and CSIRO Food and Nutritional Sciences.
Further research to assess the mechanisms involved with fibre binding polyphenol antioxidants is currently being conducted at the Centre for Nutrition and Food Sciences.
Dr Padayachee is one of 12 early-career scientists from across Australia chosen to present their research to the public for the first time as part of Fresh Science, a national program sponsored by the Australian Government. See here for more details on this program.