A pain in the gut
Tummy trouble ... scientists find concentrated milk fats may be a factor.
Around 60,000 Australians live with a chronic inflammation in their bowel causing symptoms like nausea, severe cramps and even bloody diarrhoea – not to mention a higher risk of bowel cancer. These are people with ulcerative colitis and Crohn's Disease – collectively known as Inflammatory Bowel Disease or IBD – two gut problems that are rising in industrialised countries, and which have scientists scratching their heads for a cause and a cure.
Unlike many chronic diseases that kick in at middle age, ulcerative colitis can start early. Last month Melbourne researchers reported that the incidence of the disease in Victorian children had jumped 11-fold in the last 60 years, especially since the 1990s. It's a trend reflected in similar studies overseas. What's fuelling this increase in painful gut disease isn't clear but suspect number one is an interaction between genes and something in our lifestyle - possibly diet – that triggers an immune reaction that inflames the inner lining of the bowel.
Saturated fat from milk is the latest food to come under scrutiny. New research from the University of Chicago published in the journal Nature suggests a high intake of these fats may contribute to ulcerative colitis by disrupting bacteria in the gut – at least in mice that have been made genetically prone to the disease.
The researchers found that concentrated milk fats, used in some processed foods such as chocolate, biscuits and pastries, alter the mix of bacteria in the intestines, increasing the numbers of potentially harmful bacteria called Bilophila wadsworthia. These microbes - which thrive on the type of bile the body produces to digest these fats - cause two problems. Besides acting on the immune system, they can make the gut lining more easily damaged.
This isn't the first study to link dietary fat or dairy food with IBD, says Dr Michael Conlon, Senior Research Scientist with CSIRO Food and Nutritional Sciences.
"Last year an article in the Journal of the American Dietetics Association looked at the perception of people with Crohn's Disease that dairy products exacerbated their disease. Dairy products with a high fat content were frequently reported to worsen perceived Crohn's Disease symptoms in that study," he says.
Other research has found an association with IBD and omega-6 poly unsaturated fats – fats found in sunflower, safflower and maize oil, for instance– as well as high protein diets, he adds. Omega 3 fats – the type of fat found in oily fish, however, may help protect the gut against damaging inflammation according to some studies.
The finding that saturated milk fats boost the numbers of Bilophila wadsworthia also chimes with earlier CSIRO research that found that the same bacteria cause a common infection in pigs.
"The study found that the prevalence of the infection decreases after weaning, supporting the notion of milk fats contributing to their growth," Michael Conlon says.
But while it's tempting to single out specific foods as contributing to IBD, it's just not that simple, he cautions.
"The prevalence of IBD is increasing in a pattern similar to obesity, diabetes, cancer and cardiovascular disease, all of which are associated with poor lifestyle choices. Some people may be more genetically susceptible to these diseases than others, but a bad diet and lifestyle could eventually uncover health problems that might otherwise stay dormant," he says. "Other lifestyle factors such as smoking, lack of exercise and high intakes of alcohol often contribute to 'western' diseases and could also increase the risk of IBD."
While the new study helps to understand more about how ulcerative colitis develops, the way the researchers made the mice genetically susceptible to the disease might not replicate how this happens in humans, he adds.
The mice were also fed large amounts of saturated fat that don't reflect the amounts most people would eat, according to a Dairy Australia spokesperson – around 65 per cent of the mouse diet was saturated fat compared to 13-16 per cent in a typical western diet, only a third of which comes from dairy fat.
But if some foods might contribute to IBD, can anything we eat improve it? With both bowel cancer and IBD something goes awry in the lining of the gut, and fibre may be protective.
"Consuming dietary fibres is probably one of the best strategies for helping protect against gastrointestinal problems generally," Conlon says."However, there are no proven dietary strategies to prevent or alleviate IBD."
As for probiotics, friendly microbes in probiotic supplements and some yoghurts, there's no clear evidence that they help, he says.
"But as there are many studies showing that people with IBD have altered populations of bacteria in their colon, probiotics or prebiotics (fibres that provide food for helpful bacteria) could be beneficial."
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