Feeling low? It could be your antibiotics

Published Jun 7, 2016

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London - We must stop treating antibiotics “like sweet”’, a UK government-commissioned report warned.

The report, by economist Lord Jim O’Neill, said misuse of the drugs is “teaching” superbugs to resist even powerful antibiotics.

Such bugs as Clostridium difficile are estimated to account for 700 000 deaths worldwide each year. But this could grow to ten million lives a year by 2050 if we don’t stop prescribing antibiotics unnecessarily, warned Lord O’Neill.

But could antibiotics also be a major cause of Britain’s spiralling epidemics of depression and dementia, as well as other mental disorders such as delirium and anxiety?

Brain disease might seem wholly unrelated to taking bacteria-killing drugs. But the key to the problem lies in our stomachs. Research shows that the bacteria in our gut manufacture a variety of chemicals that affect the way our brains function.

When we have a healthy balance of bacteria in our gut, these chemicals foster beneficial processes in our brains, such as the growth of new cells in the hippocampus, the brain area responsible for forming memories.

It’s thought that friendly gut microbes release brain-enhancing chemicals into the gut wall. They are then absorbed into the bloodstream and conveyed to the brain.

When the bacterial balance is upset by taking antibiotics that destroy all gut bugs — friend and foe alike — the suggestion is that our brains may be starved of chemicals that foster communication between brain cells and prevent harmful inflammation.

The first piece in this new jigsaw of evidence emerged in November when a large study of British patients concluded that taking just one course of antibiotics can significantly raise the risk of depression and anxiety. Researchers at Tel Aviv University studied the health records of more than one million Britons from 1995 to 2013 and found that a single course of antibiotics boosts the risk of depression by around a quarter.

And taking between two and five courses raises the risk by nearly half, they reported in the Journal of Clinical Psychiatry.

Taking antibiotics was also linked with increased risks of anxiety — often a precursor to depression.

“This is the first population-based study that demonstrates an association between exposure to antibiotics and risk for depression and anxiety,” says lead researcher, psychiatrist Dr Ido Lurie.

He believes that disrupting the balance of bacteria in the gut can harm the way in which the brain cells communicate.

His theory was bolstered by German research published in May. Dr Susanne Wolf, a neuroscientist at the Max Delbruck Centre for Molecular Medicine in Berlin, gave mice strong doses of antibiotics to make them free of gut bacteria.

Compared with untreated mice, those that lost healthy gut bacteria performed worse in memory tests and showed a loss of brain cell growth in their hippocampus, according to journal Cell Reports. This loss of cell growth is common in patients with early Alzheimer’s.

Dr Wolf also discovered that the loss of gut bacteria was linked to a reduction in white blood cells called Ly6Chi. These cells can inhibit harmful inflammation, another sign of advancing Alzheimer’s and linked to major depression.

When the mice’s Ly6Chi levels were restored, their memory improved, as did the level of cell growth in the hippocampus.

The danger for our brains is not only that antibiotics can kill off friendly bacteria in our guts. New research by the University of California shows they help bad bacteria thrive.

The study on mice found that friendly bacteria absorb oxygen from inside the gut. When they are killed by a course of antibiotics, there is more oxygen available for antibiotic-resistant bad bacteria such as salmonella to breathe.

Thus the food-poisoning bacteria not only have fewer ‘good’ competitors in the gut, they also have better living conditions, warned the researcher, Andreas Baumler, a professor of medical immunology and microbiology, in the journal Cell Host & Microbe.

Professor Baumler says this can cause the ironic situation where some patients are serially taking antibiotics to cure recurrent bouts of diarrhoea — even though the antibiotics help the salmonella infections to thrive.

One emerging hope is that scientists can develop a generation of “smart” antibiotics that attack only bad bugs in the stomach.

One such medication is under development: the drug, called Debio 1452, was recently shown to cause fewer changes to the gut microbiome of mice than common broad spectrum antibiotics.

In the meantime, Professor Simon Carding, an immunologist who leads the Gut Health Programme at the UK Institute of Food Research, recommends avoiding antibiotics where possible.

“An incredible number are given to children, even before they go to school,” he says.

“That can have a severe impact on good microbes in the gut — and that can cause a lifetime of physical and psychological problems.”

Professor Carding says that feeding good gut bacteria with a healthy diet is a sound strategy for mind and body health.

“The probiotic drinks you buy in plastic cartons don’t seem so effective. But simply getting five-a-day helpings of fruit and veg is useful because the fibre in them is beneficial for gut bacteria,” he says.

Daily Mail

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