Dr David Topping

All fibre is not equal

Reference: 07/193

Diet-related diseases affecting the large bowel are major causes of premature death and disability in affluent westernised countries, according to research presented in the US today by senior CSIRO nutritionist Dr David Topping.

• 30 September 2007

In an address to the New Fiber Story conference in Philadelphia, Dr Topping said conditions such as constipation, colorectal cancer (CRC) and inflammatory bowel disease (IBD) are also emerging as serious issues in developing countries as their levels of prosperity rise.

“The key to lowering the risk of these diseases is fibre,” he said.  “The health benefits of dietary fibre are well established, including greater regularity, lowering cholesterol and helping to control blood glucose. It is no secret that we need much more fibre in our diet but it is the type of fibre that can make real improvements in our health.”

A senior scientist with CSIRO’s Food Futures and Preventative Health Flagships Dr Topping told the conference foods high in resistant starch (RS), a type of dietary fibre, are attracting the attention of leading researches and health professionals.

“RS is that fraction of ingested starch that is undigested in the small intestine and enters the large bowel where it ferments slowly to promote bowel health by fuelling the growth of normal, healthy cells in the colon,“ Dr Topping said. “As it is digested slowly, RS also helps maintain healthy blood glucose levels.”

RS promotes large bowel function not through bulking but through the short chain fatty acids (SCFA) produced during its metabolism by colonic bacteria. Of the major SCFA, one acid – butyrate – is considered to be the most important. Experimental data show it is the major metabolic fuel for normal colon cells and it inhibits the growth of cancerous cells in vitro.”

Dr Topping said interest in the health benefits of dietary fibre followed studies of native populations (eg in East Africa) that consume traditional diets high in unrefined grains thought to be high in fibre. “It is emerging that while the foods these people eat are not especially high in total fibre, their cooking practices favour the formation of RS.”

Studies have shown that large bowel SCFA, particularly butyrate, can be raised by consumption of high RS foods.  RS intakes in the US, Australia and other advanced countries are extremely low and CSIRO, through the National Research Flagships program, is working actively to develop new means of supplying SCFA to the large bowel. 

“These include Starplus – a novel starch-based SCFA delivery vehicle – and high RS grains (including barley and wheat) to meet the need for convenience foods to improve public health,” Dr Topping said.

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