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Whole grain and health: new evidence • NutrInsight
2.6 Gastrointestinal health
Increased whole grain intake has been associated with various benefits to gastrointestinal health. Apart from the lower incidence of cancer at different sites along the GI tract as mentioned above, whole grain intake is associated with reduced symptoms of irritable bowel syndrome (IBS) and improved laxation.
Whole grain foods deliver various components and their effect on gastrointestinal health may be due to any or all of them:
• Dietary fibre:
– Insoluble fibre (mainly from wheat, brown rice)/prebiotic,
– Soluble fibre (higher concentration in oats, rye, barley)/prebiotic,
• Resistant starch (affected by processing of grain),
• Bioactive compounds associated with bran, germ and aleurone (“antioxidants”, polyphenols, phytate).
Dietary fibre can cause benefits by improved water retention; altered stomach emptying and flow of digesta along the GI Tract; sequestration of nutrients affecting absorption rates; delivery of fermentable carbohydrates to large bowel; or by changing the SCFA (Short Chain Fatty Acids) profile in the colon.
Prebiotic effect
The prebiotic index is defined as the change in proportions of beneficial bacteria (bifidobacteria and lactobacilli) and those considered detrimental (clostridia and bacteroides) [Hughes et al., 2007].
A cross-over design study with 31 human subjects consuming 48 g whole grain or refined grain breakfast cereal for 2 weeks (with a two week washout between treatments) showed a significant increase in faecal bifidobacteria and lactobacilli and a significant increase in stool frequency during whole grain breakfast cereal consumption [Costabile et al., 2008].
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