A world-first study led by Queensland nutritionist Dr Anneline Padayachee, PhD, has highlighted the importance of eating fruits and vegetables in their entirety for maximum nutritional benefit, rather than processed through juicing or other methods which may remove the fibre. The study found that up to 80 per cent of antioxidant polyphenols which protect cells from cancer, are bound to the fibre component of in fruits and vegetables. Dr Padayachee presented the findings of her research on Oct. 15 at Fresh Science in Melbourne, Australia, a government sponsored national program to support young Australian scientists.
Fibre does double duty as both a mechanical cleaner for the bowel as well as a vehicle to safely transport antioxidants intact to the colon, both of which are likely to reduce the risk of bowel cancer. The fibre binds to the antioxidant polyphenols, not releasing the antioxidants for digestion until they reach the large intestine, preventing them from being digested in the stomach or small intestine.
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“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 per cent 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.”
Dr Padayachee completed both her undergraduate degree in Nutritional Science and her PhD at the University of Queensland in Australia. She is one of only 12 early-career Australian scientists chosen to present their research to the public for the first time as part of Fresh Science. She is also a certified personal trainer and group fitness instructor.
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Dr Padayachee has worked in a diverse range of occupations throughout the food supply chain from being a fruit and vegetable picker, to performing quality control at a processing plant. It was when she was working at a fruit juice processing plant that she had the idea to pursue this line of research. Watching all the fruit pulp being thrown away made her wonder how much of the nutritional benefit was being thrown away as well.
“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.”
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Dr Padayachee’s research focused on black carrots, which are actually purple and very rich in two groups of antioxidant polyphenols – anthocyanins and phenolic acids.
Black carrots are the predecessor to the orange carrots which are more common in the present day. Black carrots are still grown in Asia and Southern Europe and some health food shops or boutique grocers carry them. They are a popular choice for the health conscious as they are one of the highest sources of anthocyanins and have been found to be very potent antioxidants. It is the anthocyanins, a type of antioxidant polyphenol, that causes the purple-red pigment in fruits and vegetables such as these carrots, eggplant, cherries, blueberries and raspberries as well as giving pansies their beautiful, vibrant purple colored petals.
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Further research to assess the mechanisms involved with fibre binding polyphenol antioxidants is currently being conducted at the Centre for Nutrition and Food Sciences, which may lead to fibre being used to deliver medicines directly to the colon, preventing them from being released in the stomach or small intestine, much as enteric-coated tablets are used for currently.
Anneline hopes her work might also help uncover medicinal uses for plant fibre in targeted treatments of dietary conditions.
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The research project, which was jointly funded by the University of Queensland Centre for Nutrition and Food Science, the CSIRO and the Australian Research Council, finished in 2012, culminating a four-year effort by the research team.
A. Padayachee, G. Netzel, M. Netzel, L. Day, D. Zabaras, D.Mikkelsen and M.J. Gidley (2012) Binding of polyphenols to plant cell wall analogues – Part 1: Anthocyanins Food Chemistry, volume 134: 155-161.
A. Padayachee, G. Netzel, M. Netzel, L. Day, D. Zabaras, D.Mikkelsen and M.J. Gidley (2012) Binding of polyphenols to plant cell wall analogues – Part 2: Phenolic Acids. Food Chemistry, volume 135: 2287-2292.