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Milk fat may lead to bowel diseases by altering gut bacteria: Study

3 comments14-Jun-2012

Saturated milk fats commonly found in Western processed foods could be leading to changes in the gut ecosystem that result in higher risks of inflammatory bowel diseases, warn researchers.

The findings may help explain why immune-related conditions such as colitis have become more prevalent in Western societies in the last half century. Writing in Nature, the team of US-based researchers reveal that consumption of a diet high in saturated milk fats causes a "boom in bad bacteria" in the gut – which in turn leads to increased inflammation and a higher risk of developing bowel conditions for certain people.

"Here we show how the trend in consumption of Western-type diets by many societies can potentially tip the mutualistic balance between host and microbe to a state that favors the onset of disease," said Professor Eugene Chang of the University of Chicago, USA – who led the study.

The research team revealed that concentrated milk fats, that are abundant in processed and confectionery foods, alter the composition of bacteria in the intestines by encouraging the growth of harmful gut microbes. Such changes then disrupt the delicate balance between the microbiota and the immune system, leading to unregulated immune responses that can damage tissues and be difficult to switch off, they said.

"This is the first plausible mechanism showing step-by-step how Western-style diets contribute to the rapid and ongoing increase in the incidence of inflammatory bowel disease," said Chang.

"We know how certain genetic differences can increase the risk for these diseases, but moving from elevated risk to the development of disease seems to require a second event which may be encountered because of our changing lifestyle."

Increased risk

The researchers worked with a mouse model that has many of the characteristics of human IBD.

Chang and his team explained that genetically deleting the immune system modulator molecule interleukin 10 – which acts as a brake on the immune system's response to intestinal bacteria – caused about 20% of mice to develop colitis when fed a low-fat diet or a diet high in polyunsaturated fats.

However when exposed to a diet high in saturated milk fats, the rate of disease development within six months tripled – increasing to more than 60%.

In addition, the onset, severity and extent of colitis were much greater than that observed in mice fed low-fat diets, they said.

Inflammatory mechanism

The team then set out to find why milk fat triggered inflammation when polyunsaturated fat did not – tracing the answer to the gut microbiome.

Chang revealed that uncommon gut microbe, called Bilophila wadsworthia, was preferentially selected in the presence of milk fat. Previous studies have shown high levels of B. wadsworthia in patients with appendicitis and other intestinal inflammatory disorders, including inflammatory bowel disease.

"That piqued our interest," said Chang. "These pathobionts, which are usually non-abundant, seem to be quite prominent in these diseases."

Indeed, while B. wadsworthia levels were almost undetectable in mice on a low-fat or unsaturated-fat diet, the ‘bad’ bacteria made up about 6% of all gut bacteria in mice fed a high milk-fat diet.

"Unfortunately, these can be harmful bacteria," Chang explained. "Presented with a rich source of sulfur, they bloom, and when they do, they are capable of activating the immune system of genetically prone individuals."

Re-shaping the ecosystem

The lead researchers noted that whilst there is very little that can be done to ‘correct’ genes that predispose individuals to increased risk of developing such inflammatory diseases, one thing that can be done is to try and shift the balance of gut bacteria back to a ‘healthy state’

"In essence, the gut microbiome can be 're-shaped' in sustainable and predictable ways that restore a healthy relationship between host and microbes, without significantly affecting the lifestyles of individuals who are genetically prone to these diseases,” said Chang. “We are testing that right now."

Source: Nature
Published online ahead of print, doi: 10.1038/nature11225
“Dietary-fat-induced taurocholic acid promotes pathobiont expansion and colitisin Il10−/− mice”
Authors: S. Devkota, Y. Wang, M.W. Musch, V. Leone, H. Fehlner-Peach, A. Nadimpalli, D.A. Antonopoulos, B. Jabri, E.B. Chang

3 comments (Comments are now closed)

Tip of the iceberg

As a clinical dietitian in an acute care setting, I can tell you that this has been suspected for a long time. This is not the first time that milk has been associated with the increased risk of disease, and I suspect there will be more to come. Just look at the Harvard SPH 'Healthy Plate' to see that they recommend water and not milk, and suggest keeping milk consumption to a minimum. The main reason we do not hear more about this kind of research findings is the because of the unbreakable influence the dairy industry has in Washington DC.

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Posted by Not Milk
23 July 2012 | 05h32

Misleading headline

The headline of this story is quite misleading. It suggests that human beings were involved. However the study was about bowel diseases in mice. There are several aspects why the results of the study cannot be transferred to human beings. For example the simple fact that the mice were genetically manipulated wereby they miss a molecule which helps to control inflammation. Compared to normal mice the percentage of bowel disease is 25 % to 30% higher. Sothis not a situation comparable with the human world.

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Posted by René van Buitenen, Dutch Dairy Association
27 June 2012 | 13h39

What about drinking milk?

A whole lot of milk fats are ingested from drinking milk on its own, in tea[especially in the UK], on cereal and in yogurt etc. Also from eating butter spreads and cheeses. The popular semi-skimmed milk still has around 50% the fat of whole milk. From all I've read, it does not seem likely to me that milk is inherently bad for you, with its high calcium and favorable probiotic lacto-bacilli. In supermarkets there is a plethora of low fat processed foods available which are more likely to do harm in my opinion.

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Posted by chris aylmer
25 June 2012 | 20h14

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