A Western diet rich in sugar and fat causes damage to Paneth cells – immune cells in the gut that help keep inflammation in check, a study shows.
When Paneth cells aren’t functioning properly, the gut immune system is prone to inflammation, putting people at risk of inflammatory bowel disease, say the authors, who performed studies of both humans and lab mice.
American and British diets in particular are high in sources of fat and sugar, from foods including butter, pastries, chocolate, confectionery, pizza, burgers and white bread.
Eating a Western diet impairs the immune system in the gut in ways that could increase risk of infection and inflammatory bowel disease, according to a study from researchers at Washington University School of Medicine in St. Louis and Cleveland Clinic
THE WESTERN DIET
The Western diet is typically full of red meat, processed, fried, or high fat foods, refined grains and sugar.
It includes butter, pastries, chocolate, confectionery, pizza, burgers and white bread.
It’s seen as the antithesis of the Mediterranean diet, which has been promoted by health experts.
The Mediterranean-style diet is made up of vegetables, fruits, legumes, nuts, beans, cereals, grains, and unsaturated fats such as olive oil.
The new study has been conducted by researchers at Washington University School of Medicine in St. Louis and Cleveland Clinic, who warn of the spread of the Western diet.
‘Inflammatory bowel disease has historically been a problem primarily in Western countries such as the US, but it’s becoming more common globally as more and more people adopt Western lifestyles,’ said lead author Ta-Chiang Liu at Washington University.
‘Our research showed that long-term consumption of a Western-style diet high in fat and sugar impairs the function of immune cells in the gut in ways that could promote inflammatory bowel disease or increase the risk of intestinal infections.’
It’s already been known that Paneth cell impairment is a key feature of inflammatory bowel disease.
Paneth cells are a type of anti-inflammatory immune cell found in the intestines that helps to protect against microbial imbalances and infectious pathogens.
Dysfunction of these cells is driven by a combination of genetic mutations and environmental factors.
As an example, people with Crohn’s disease – a kind of inflammatory bowel disease characterised by abdominal pain, diarrhoea, anaemia and fatigue – often have Paneth cells that have stopped working.
A tiny, 3D model of the intestines formed from anti-inflammatory cells known as Paneth cells (green and red) and other intestinal cells (blue) is seen in the image above
WHAT IS BODY MASS INDEX (BMI)?
Body mass index (BMI) is a measure of body fat based on your weight in relation to your height.
- BMI = (weight in pounds / (height in inches x height in inches)) x 703
- BMI = (weight in kilograms / (height in meters x height in meters))
- Under 18.5: Underweight
- 18.5 – 24.9: Healthy
- 25 – 29.9: Overweight
- 30 or greater: Obese
To find the cause of Paneth cell dysfunction in humans, researchers analysed a database containing demographic and clinical data on 930 individuals, including an assessment of each person’s Paneth cells.
They found that high body mass index (BMI) was associated with Paneth cells that looked abnormal and unhealthy under a microscope.
BMI – a measurement based on weight in relation to height – defines whether a person is underweight, of a normal weight, overweight or obese.
For both people with and without Crohn’s disease, the higher their BMI, the worse their Paneth cells looked.
So, in other words, being overweight and obese was linked with abnormal Paneth cells.
To better understand this connection, the researchers then compared the effects of a western diet versus a standard diet – but in lab mice genetically predisposed to obesity.
Such mice chronically overeat because they carry mutations that prevent them from feeling full (much like some humans).
The scientists fed normal mice a diet in which 40 per cent of the calories came from fat or sugar, similar to the typical Western diet, and compared them to mice fed a normal diet.
After eight weeks, the mice that ate the western diet had more abnormal Paneth cells than the group that ate a standard diet.
In the western diet group, other changes become apparent two months after the Paneth cell defects, including increased gut permeability, where bacteria and toxins can enter the gut, which is well-linked with chronic inflammation.
Notably, however, Paneth cells returned to normal when the mice were put back on a healthy mouse diet for four weeks.
This suggested that high fat diets, not obesity, caused abnormal Paneth cells – an important distinction.
‘Obesity wasn’t the problem per se,’ Liu said. ‘Eating too much of a healthy diet didn’t affect the Paneth cells. It was the high-fat, high-sugar diet that was the problem.’
Whether people who habitually eat a Western diet can improve their gut immunity by changing their diet remains to be seen, according to Liu.
‘This was a short-term experiment, just eight weeks,’ Liu said. ‘In people, obesity doesn’t occur overnight or even in eight weeks.
‘People have a suboptimal lifestyle for 20, 30 years before they become obese.
‘It’s possible that if you have Western diet for so long, you cross a point of no return and your Paneth cells don’t recover even if you change your diet.
In people, obesity is frequently the result of eating a diet rich in fat and sugar. Pictured, an obese woman
‘We’d need to do more research before we can say whether this process is reversible in people.’
Further experiments showed that a molecule known as deoxycholic acid, a secondary bile acid formed as a byproduct of the metabolism of gut bacteria, forms the link between a Western diet and Paneth cell dysfunction.
The bile acid increases the activity of two immune molecules – farnesoid X receptor and type 1 interferon – that inhibit Paneth cell function.
Liu and colleagues now are investigating whether fat or sugar plays the primary role in impairing Paneth cells.
They also have begun studying ways to restore normal Paneth cell function and improve gut immunity by targeting the bile acid or the two immune molecules.
The findings have been published in the journal Cell Host & Microbe.
OBESITY: ADULTS WITH A BMI OVER 30 ARE SEEN AS OBESE
Obesity is defined as an adult having a BMI of 30 or over.
A healthy person’s BMI – calculated by dividing weight in kg by height in metres, and the answer by the height again – is between 18.5 and 24.9.
Among children, obesity is defined as being in the 95th percentile.
Percentiles compare youngsters to others their same age.
For example, if a three-month-old is in the 40th percentile for weight, that means that 40 per cent of three-month-olds weigh the same or less than that baby.
Around 58 per cent of women and 68 per cent of men in the UK are overweight or obese.
The condition costs the NHS around £6.1billion, out of its approximate £124.7 billion budget, every year.
This is due to obesity increasing a person’s risk of a number of life-threatening conditions.
Such conditions include type 2 diabetes, which can cause kidney disease, blindness and even limb amputations.
Research suggests that at least one in six hospital beds in the UK are taken up by a diabetes patient.
Obesity also raises the risk of heart disease, which kills 315,000 people every year in the UK – making it the number one cause of death.
Carrying dangerous amounts of weight has also been linked to 12 different cancers.
This includes breast, which affects one in eight women at some point in their lives.
Among children, research suggests that 70 per cent of obese youngsters have high blood pressure or raised cholesterol, which puts them at risk of heart disease.
Obese children are also significantly more likely to become obese adults.
And if children are overweight, their obesity in adulthood is often more severe.
As many as one in five children start school in the UK being overweight or obese, which rises to one in three by the time they turn 10.