Antibiotics may make us fat
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London - At first glance it sounds likean ad for a dodgy herbal supplement. Two years agoChinese microbiologist Dr Zhao Liping revealed at a US conference how he’d lost 44lb (about 20kg) simply by eating Chinese yam and bitter melon.
He said the foods had a beneficial effect on the bacteria in his gut.
But what distinguishes Dr Liping’s claims from the quack remedies on the internet is that he is a respected scientist whose work on the link between the “good” bacteria that lives in our guts and obesity has just been published in the top science journal Nature.
He is just one of a number of scientists whose work is painting a dramatic new picture of the health impact of the billions of bacteria that call our bodies home. Keep these bacteria in the right balance and they can control weight, cut the risk of eczema in babies and keep old people stronger, it seems. It may even be possible to use beneficial bacteria to switch certain genes on or off.
If all this is true, it could be another very good reason for avoiding antibiotics.
For years doctors have been cautioned not to prescribe antibiotics like Smarties for every cough and cold, partly because they have no effect on the viruses that cause these illnesses, but more importantly because widespread use drives up resistance, leading to superbugs.
But now scientists believe excessive antibiotic prescribing could be damaging our health more directly. By wiping out our gut bacteria, they could be making us ill, fat and prone to auto-immune diseases such as eczema.
First to Dr Liping’s extraordinary discovery. Back in 2006, feeling ill and decidedly portly, he came across a report that fat rats had different bacteria in their guts compared with thinner rats.
“The key player was a microbe called F.Prausnitzii that was much lower in the fatties,” he told the Mail.
Being a microbiologist, Dr Liping was able to test a faecal sample to see how much F.Prausnitzii he had. There was almost none.
He decided to see if it was possible to repopulate his gut. But how to shift the balance?
“There’s a lot of evidence that various foods can encourage changes in gut flora,” he says. “So I searched for a traditional remedy.”
He came across Chinese yam and bitter melon, which were used to treat diabetes and obesity in Imperial times. As well as adding these to his diet, he also switched to whole grains.
Soon the weight started dropping off and the proportion of F.Prausnitzii in his gut went up from undetectable levels to a healthy 14.4 percent, while his blood pressure, heart rate and cholesterol all came down.
It seems something in the yam and melon triggered the beneficial bacteria to multiply - this is known as a prebiotic effect.
Since Dr Liping’s discovery, much larger clinical trials have been run by his lab at the Shanxi Academy of Agricultural Sciences in Taiyuan, China. The first involved more than 100 obese young men who lost an average of 15lb after just nine weekson the prebiotic diet. A trial involving1,000 obese patients is nowunder way.
No one really knows how it works yet. It could be that beneficial bacteria that respond to the yam and melon reduce the amount of food absorbed in the gut. But Dr Liping admits it’s not even clear whether the bacteria actually cause the weight loss or just show up when the gut is healthier.
For some years now researchers have shown that giving the beneficial bacteria themselves - known as probiotics - can prevent or treat diseases. A recent report found a probiotic combination halved the risk of eczema in babies. It also cut their chance of developing allergies to irritants such as pollen, house dust, milk and eggs.
Researchers at Swansea University gave either a placebo, or a commercial brand of probiotics to 450 mothers for the last three months of pregnancy and for the babies’ first six months.
After two years the risk of developing eczema was down by 60 percent and the chances of developing an allergy had dropped by half.
“Allergies are on the rise, affecting three times as many youngsters as 20 years ago,” says Professor Stephen Allen, who led the study (which has just been submitted for publication in the Journal of Allergy and Clinical Immunology). “We showed that there is something to be done to cut the risk at a youngage.”
It also raises the possibility that giving regular courses of antibiotics to young children may do more harm than good.
One of the first researchers to pick this up was Martin Blaser, professor of internal medicine and microbiology at New York University and an expert on the ulcer-causing bug H.pylori.
Anyone infected with this usually gets an intensive antibiotic course to kill it off. But that may not be wise, says Professor Blaser. It could be contributing to the obesity epidemic.
“We’ve found that H.pylori is often one of the good guys,” he says. “Among other things it controls the hunger hormone ghrelin that’s made in the guts. When levels of ghrelin rise, you feel hungry. Getting rid of H.pylori pushes up ghrelin production, although we don’t know why yet.
“Children get lots of antibiotics, and I’m afraid that may be contributing to childhood obesity.”
H.pylori can also be a problem: it does cause ulcers and has been linked with gastric cancer, But other experts are beginning to question whether knocking it out is always a good idea.
“There is some evidence that H.pylori can protect against acid reflux [when stomach acid leaks into the gullet causing heartburn],” says Dr Ruchit Sood, specialist registrar in gastroenterology at York TeachingHospital. “It’s been increasing as H.pylori infection has been declining.”
Heavy-handed use of antibiotics could also be making children with the lung disease cystic fibrosis and elderly patients more likely to develop infections, according to new research.
This isn’t because of growing resistance, but because carpet bombing with antibiotics - as one researcher puts it - upsets the balance of bugs in our guts.
“We’ve been looking at the friendly microbe population in kids with cystic fibrosis, and the number of species is right down. Just a few dominate,” says lead researcher Professor John LiPuma, paediatrician at the University of Michigan.
“There’s evidence a more varied bug community is better at keeping the bad bacteria in check.”
Another study published in Nature found something similar with elderly people. Those living in the community had greater variety in their gut’s bug population and had fewer infections than those in care homes. They were also less likely to be fragile. However, it hasn’t yet been shown that boosting bacteria variety would reduce fragility.
Research such as this is already pointing in a revolutionary new direction. If friendly bacteria can influence our weight, resistance to infection and strength in old age, maybe targeting and tweaking their genes could bring major benefits.
This is the big idea of Professor Jeremy Nicholson, a biomolecular researcher at Imperial College London. “Gut bacteria release chemicals that can turn human genes on and off in beneficial ways,” he says. “Finding ways to boost that effect could result in new treatments.”
A good place to look, he suggests in a new paper, is among the substances used in Chinese medicine.
Did the foods Dr Zhao Liping use in his weight loss programme also have a beneficial effect on genes linked to weight loss? No one knows yet, but it’s an exciting thought. - Daily Mail