Tag Archives: gut bacteria

What’s the link between autism and gut bacteria?

No matter how lonely you might feel, rest assured you’re never by yourself. Millions of microorganisms live in relative peace and harmony inside our guts, collectively comprising the “gut microbiota”. More and more research suggests that abnormalities in this microbiota can impact virtually all organs — and that includes the brain, too. And, according to a new study, treating the gut’s microflora could be key to easing autism symptoms.

Credit: Pixabay.

The connection between the gut microbiome and the brain is known as the microbiome–gut–brain axis. This connection is of important interest to researchers because individuals suffering from neurological and developmental conditions, such as Alzheimer’s disease and Autism Spectrum Disorders, also suffer from chronic gastrointestinal symptoms.  One 2014 study published in the journal Pediatrics, for instance, found that children with autism are about four times more likely to experience gastrointestinal (GI) distress than are their typically developing peers.

If abnormal gut bacteria may be amplifying autism symptoms, would a healthy microbiome improve symptoms? In a recent study, researchers at Arizona State University and Northern Arizona University attempted to answer this question.

For their study, they recruited 18 children with Autism Spectrum Disorder who also had chronic gastrointestinal problems. The participants followed a 10-week treatment consisting of antibiotics, a bowel cleanse, and then a high dose of microbiota fecal transfer (MTT).

According to the results, eight weeks after the treatment, 80% of the patients experienced reductions in gastrointestinal symptoms and slow, but significant improvements in their autism-related symptoms.

Two years later, the patients still experienced a 58% improvement in gastrointestinal symptoms as measured by the Gastrointestinal Symptom Rating Scale. Some of the symptoms that showed improvement include abdominal pain, indigestion, diarrhea, and constipation.

These results could be considered quite spectacular seeing how all of the patients claimed they hadn’t had normal gastrointestinal tract functioning since infancy. Meanwhile, the severity of autism symptoms dropped by 47%. At the beginning of the study, 83% of the children were classified as “severe” on the autism spectrum. However, two years post-treatment, only 17% of children fell under this classification. Most shocking of all, 44% of the participants had scores below the Autism Spectrum Disorder diagnostic cut-off point, the authors wrote in the journal Scientific Reports.

“Important changes in gut microbiota at the end of treatment remained at follow-up, including significant increases in bacterial diversity and relative abundances of Bifidobacteria and Prevotella. Our observations demonstrate the long-term safety and efficacy of MTT as a potential therapy to treat children with ASD who have GI problems, and warrant a double-blind, placebo-controlled trial in the future,” the authors wrote.

Another study published this month by a team led by Dr. Katerina Johnson of Oxford University’s Department of Experimental Psychology found that both gut microbiome composition and diversity were related to differences in personality, including sociability and neuroticism.

“This suggests that the gut microbiome may contribute not only to the extreme behavioural traits seen in autism but also to variation in social behaviour in the general population. However, since this is a cross-sectional study, future research may benefit from directly investigating the potential effect these bacteria may have on behaviour, which may help inform the development of new therapies for autism and depression,” Johnson said.

It’s not clear what could drive this association but having different populations of digestive tract bacteria and patterns of gene expression have been previously identified as potential factors.

There are still a lot of unanswered questions considering the field is still in its infancy, yet growing rapidly. Just the idea that microbes could influence the brain was unthinkable a few years ago and the pace of research has accelerated over the past few years. Just imagine the possibilities: in the future, it could be possible that ASD symptoms are remedied with bacterial metabolites; there might even be probiotics for autism.

More research is warranted in order to tease out the connection between gut bacteria and autism/behavioral changes. Studies so far on the subject have been mostly small and uncontrolled — and it’s not clear what they mean, given that researchers are still trying to establish the ingredients of a healthy microbiome. This, hopefully, will change in the future as more interest and funding is awarded to investigate this association that cannot be ignored any longer.

Gut bacteria resistance to antibiotics doubles in the last 20 years

Researchers have uncovered a worrisome trend in which harmful bacteria known to cause dangerous stomach diseases are becoming increasingly resistant to even some of the most powerful antibiotics at our disposal. According to a new study, resistance to commonly-used antibiotics has doubled in the past 20 years.

Credit: Wikimedia Commons.

For their study, the team led by Francis Megraud, Professor of Bacteriology at the University of Bordeaux in France and the founder of the European Helicobacter & Microbiota Study Group, studied the antibiotic response of 1,232 patients from 18 countries who were infected with Helicobacter pylori (H. pylori).

If left untreated, this bacterial infection may cause gastric ulcers, lymphoma, and even gastric cancer.

For years, doctors have been prescribing clarithromycin to ward off H. pylori, but since 1998, resistance to the antibiotic has surged from 9.9% to 21.6% as of last year. The researchers found similar jumps in resistance for levofloxacin and metronidazole.

H. pylori infection is already a complex condition to treat, requiring a combination of medications. With resistance rates to commonly used antibiotics such as clarithromycin increasing at an alarming rate of nearly 1% per year, treatment options for H. pylori will become progressively limited and ineffective if novel treatment strategies remain undeveloped. The reduced efficacy of current therapies could maintain the high incidence rates of gastric cancer and other conditions such as peptic ulcer disease, if drug resistance continues to increase at this pace,” Megraud said in a statement.

The study found that the highest rates of clarithromycin resistance in H. pylori were in Southern Italy (39.9%), Croatia (34.6) and Greece (30%). It’s no wonder that these countries are also known for overconsumption of antibiotics in inappropriate situations, including for conditions like cold and flu (for which antibiotics are useless since they’re caused by viral infections). These countries also have poor antibiotic resistance containment strategies.

Antibiotic resistance occurs when an antibiotic is no longer effective at controlling or killing bacterial growth. Bacteria that are ‘resistant’ can multiply in the presence of various therapeutic levels of an antibiotic. Sometimes, increasing the dose of an antibiotic can help tackle a more severe infection but in some instances — and these are becoming more and more frequent — no dose seems to control bacterial growth. Each year, 25,000 patients from the EU and 63,000 patients from the USA die because of hospital-acquired bacterial infections which are resistant to multidrug-action. 

According to a 2013 CDC report titled “Antibiotic Resistance Threats in the United States, antibiotic resistance is responsible for $20 billion in direct health-care costs in the United States. Without urgent action, the number of infections could rise dramatically.

H. pylori is believed to be present in about one half of the world’s population, but most never get sick. Some, however, aren’t so lucky and the bacteria can cause some uncomfortable complications like inflammation of the stomach lining (gastritis) and peptic ulcers.

For some time, H. pylori antibiotic resistance has been considered as a severe threat to public health, with the World Health Organization (WHO) calling clarithromycin-resistant H. pylori a high priority for antibiotic research and development. According to an OECD report, superbug infections could cost the lives of around 2.4 million people in Europe, North America and Australia over the next 30 years. The good news is three out of four deaths could be averted by spending just 2 USD per person a year on measures like handwashing and more prudent prescription of antibiotics.

“The findings of this study are certainly concerning, as H. pylori is the main cause of peptic disease and gastric cancer,” commented Mário Dinis-Ribeiro, President of the European Society of Gastrointestinal Endoscopy. “The increasing resistance of H. pylori to a number of commonly-used antibiotics may jeopardize prevention strategies.”

The findings appeared in the journal UEG Journal and were presented today at UEG Week Barcelona 2019.

Weight gain is mostly controlled by what you eat — not genetics

If you want to blame someone for those extra pounds, the best place to look is probably in the mirror.

As the world tries to deal with its ever-growing obesity crisis, the main causes of this problem are still under debate. However, more and more studies are indicating that the main culprit is, as expected, food.

Genes decide a lot of things about your body — your eye color, your hair, even how you look like. But, according to a new study, it doesn’t really decide how much you weigh (as an adult, at least). Scientists at King’s College London recently carried out a study on twins to assess how the gut processes and distributes fat.

Essentially, they analyzed poop samples from over 500 pairs of twins to build up a picture of how the gut microbiome distributes fat. They also analyzed how much of this process is genetic and how much is directed by environmental factors. Overall, they found that only 17.9% of all gut processes could be attributed to hereditary factors, while 67.7% of gut activity was influenced by environmental factors — mainly, the regular diet.

This is an exciting study, not just because it confirms that what we eat governs how our weight is distributed, but because it allows researchers to understand which microbes are associated with which chemical metabolites in the gut. Ultimately, this could help scientists understand how the gut bacteria affects us, and how it can be modified for weight management.

The fecal metabolome largely reflects gut microbial composition, and it is strongly associated with visceral-fat mass, thereby illustrating potential mechanisms underlying the well-established microbial influence on abdominal obesity. Dr. Jonas Zierer, the lead author of the study, believes this could one day be instrumental in dealing with obesity.

‘This study has really accelerated our understanding of the interplay between what we eat, the way it is processed in the gut and the development of fat in the body, but also immunity and inflammation. By analysing the faecal metabolome, we have been able to get a snapshot of both the health of the body and the complex processes taking place in the gut.’

This is also good news because it means that most of the factors associated with extra pounds are modifiable. Zierer adds:

‘This new knowledge means we can alter the gut environment and confront the challenge of obesity from a new angle that is related to modifiable factors such as diet and the microbes in the gut. This is exciting, because unlike our genes and our innate risk to develop fat around the belly, the gut microbes can be modified with probiotics, with drugs or with high fibre diets.’

Head of the Department of Twin Research at King’s, Professor Tim Spector was also excited by the possibility. He emphasizes another advantage of this study — the fact that potential treatments or supplements might be implemented at a large scale through innovative approaches.

‘This exciting work in our twins shows the importance to our health and weight of the thousands of chemicals that gut microbes produce in response to food. Knowing that they are largely controlled by what we eat rather than our genes is great news, and opens up many ways to use food as medicine. In the future these chemicals could even be used in smart toilets or as smart toilet paper.’

Worldwide, over 2 billion people are overweight or obese, and over the past 20 years, obesity rates have more than doubled. The growing trend shows no sign of stopping or slowing down, as childhood obesity also grows at dramatic rates: 1000% in the past 40 years.

Journal Reference: Zierer et al. “The fecal metabolome as a functional readout of the gut microbiome.” Nature Genetics (2018). https://doi.org/10.1038/s41588-018-0135-7

New evidence suggests that probiotics are good for the liver

Following previous evidence that probiotics really do help the gut, a new study suggests that they might also help the liver.

Probiotics are basically bacterial populations that play a beneficial role in our gut. While most of the hype around probiotics is not supported by evidence, they do show some promise. Recent research has backed up some of the claims around probiotics, and the topic has gained significant attention in recent years, especially as we’ve learned that bacteria in our gut affect much more than just our intestines.

“Probiotics have been studied most intensely in the context of the gastrointestinal tract,” said Bejan Saeedi, a doctoral candidate at Emory University who conducted new research on the matter.

“This study provides evidence that the effects of probiotics extend beyond the gastrointestinal tract. What makes this study unique is that it suggests a discreet molecular mechanism by which these effects are elicited.”

He and his colleagues focused their research on the probiotic Lactobacillus rhamnosus GG (known as LGG), a common probiotic species found in many over-the-counter supplements. They gave mice food rich in these probiotics for two weeks, and then they recorded their response to a high dose of acetaminophen (the active ingredient in Tylenol), a drug known to send the liver into overcharge.

Taking too much acetaminophen is one of the leading causes of liver damage. Researchers found that mice who received a dose of probiotics were less likely to suffer from an acetaminophen overdose.

“Administration of the probiotic LGG to mice improves the antioxidant response of the liver, protecting it from oxidative damage produced by drugs such as acetaminophen,” explained Saeedi.

Since the liver is essentially a hub for toxin removal from the body and also plays a role in transforming food into energy, it makes sense that it is affected by the gut bacteria population — especially as it’s “downstream” from the gut.

The team traced this protective effect to a protein called Nrf2, which regulates the expression of genes involved in fighting free radicals. Taking too much acetaminophen creates oxidative stress and free radicals inside the liver (though there are other processes which can have a similar effect).

Previous mice studies have also shown that LGG can protect against alcoholic liver disease and non-alcoholic fatty liver disease. Of course, mice studies don’t always translate to humans, and Saeedi is now in the process of looking for human volunteers for trials.

While there seems to be growing evidence that probiotics are good for the body, it’s important not to fall into the trap of exaggerating potential benefits. Much is being said and advertised about probiotics, and not everything can pass the scrutiny of science.

The study will be presented at the Experimental Biology conference. Results have not yet been peer-reviewed.

Scientists write molecular cookbook for our gut bacteria

Scientists have written an unusual cookbook — one that’s not for humans, but rather for our microbiome.

Cookbooks for humans are aplenty, but this is the first one aimed at gut bacteria.

When scientists publish something, it’s usually complex papers about previously unknown mechanisms or processes, but today, in Nature Microbiology, scientists are putting a new spin on that: they’re publishing recipes to successfully grow and study gut bacteria in the lab. Their work will help researchers across the world to advance our understanding of gut bacteria.

Recent research has increasingly shown that gut bacteria is important for our health, with studies finding that the meager bacteria in our guts play a part in protecting against diseases, recovering from injuries, even regulating our genes. However, we know surprisingly little about how all this happens. We don’t know how it grows, how it metabolizes nutrients, and we don’t even know what kind of food it likes.

Nassos Typas and his colleagues from the European Molecular Biology Group have addressed that in their latest study. Along with Peer Bork and Kiran Patil, he selected the most common bacteria to be found in the human gut, plus important species connected to gut diseases such as colorectal cancer and inflammatory bowel disease, ending up with 96 strains from 72 bacterial species, in 19 different growth environments.

They characterized the nutritional preference of these bacteria, as well as their ability to digest and produce specific molecules. As it so often happens with studies on gut bacteria, results were quite surprising.

“We were surprised to find new bacteria with the capability to utilize mucin, the protein that makes up mucus,” says Kiran Patil. “These bacteria can contribute to inflammation and infection by weakening the protective mucus barrier lining the gut. Another surprise came from bacteria that proved to be inhibited by amino acids and short-chain fatty acids, common ingredients in most growth media. It turns out that rich media with many nutrients can be toxic for these species, whereas we used to think: the more food, the better.”

Also surprisingly, researchers found that even bacteria that are closely related to each other can have very different nutritional preferences, showing that a bacterium’s genes alone can’t predict what it likes to ‘eat.’

With this scientific ‘cookbook’ filled with molecular recipes on how to grow gut bacteria, researchers want to provide the scientific community with tools to study the structure and function of the human gut microbe. It’s clear that we need much more work before we can thoroughly understand the role and impact of gut bacteria, and this could be a major stepping stone for such future studies.

“Our resource provides scientists with tools to experimentally investigate the gut microbiome ecology, going beyond correlations and identifying causes and effects,” says Nassos Typas.

Journal Reference: Tramontano, M., Andrejev, S. et al. Nutritional preferences of human gut bacteria reveal their metabolic idiosyncrasies. Nature Microbiology, published online 19 March 2018.


We still don’t know which gut bacteria is beneficial, but scientists have some good hints

There are ten times more bacteria in your body than your own cells. This might seem scary, but really you wouldn’t be able to function without most of them like the probiotics that help digest your food and fight invading microbes. There’s good bacteria and bad bacteria, but the gut seems to be so diverse in its bacterial offering from person to person that scientists have always found it difficult to say “hey, this is what a healthy microbiome should look like.” Analyzing thousands of bacteria species in your guy is challenging and we’re still not there, but a recent effort involving 4,000 participants has some good hints as to what makes a healthy gut.


Image: Pixabay

Researchers collected and analyzed feces from 4,000 individuals living in the U.S., the United Kingdom, Belgium and the Netherlands. They identified 664 different genera, although we’re pretty convinced there are plenty more bacterial species which weren’t tagged. Later, the stool samples were expanded to include some coming from Papua New Guinea, Peru and Tanzania. In this expanded version, the researchers found 14 genera of microbes that were common in  95% of the humans sampled.

“We compared all the microbiota we could get our hands on,” says Jeroen Raes at the University of Leuven (KUL) in Belgium, who led the study.

This bacteria diversity data was then correlated with the health and behaviour of the participants. The most important takeaway is having  bacterial diversity in the gut offers health benefits, and the more the better. Those people who had less microbiome diversity were those with a higher body-mass index, which corresponds to being overweight or obese. Those who had the most gut bacteria diversity ate a lot of fruits and vegetables. Dairy-rich diets were also associated with a more diverse biome. Subjects who drank coffee and tea also saw an improvement, while soda reduced the diversity for unclear reasons.

To increase your gut bacteria diversity, the findings suggests, consume fruits, vegetables, dairy and probiotics-rich products like yoghurt.

The older the people involved in the study, the more diverse their biomes. More than anything, however, the use of medicine influenced the greatest variation among the people involved in this study. These include drugs like antibiotics, osmotic laxatives, medications for inflammatory bowel disease, benzodiazepines, antidepressants, antihistamines or hormones used for birth control or to alleviate symptoms of menopause.

Considering so few genera were shared by people across the world, the relationship between a certain bacterial biome and health benefits is debatable. We know for sure, however, that there are bacteria that cause a plethora of health problems like irritable bowel syndrome, and even as many as 23,000 deaths in the United States alone. Through careful analysis and more genetic sequencing of the bacteria that line our guts, many lives might be saved.

Why processed foods make you fat: two common food additives linked to obesity and gut inflammation

A new study suggests that two very common emulsifiers – chemicals that stabilize foods and stop products like mayo from separating – could increase the risk of obesity and irritable bowel syndrome.

Mayo and mustard are among the products which almost always contain emulsifiers. Image via Wiki Commons.

The emulsifiers in question are carboxymethycellulose and polysorbate-80; especially in Europe and North America, they are commonly used in processed foods (mayo, ketchup, numerous sauces, ice cream, gluten-free products, fat-free products and many others) and other common products (toothpaste, detergents etc). The study conducted on mice showed that even in low concentrations, these substances drastically affect the gut bacteria which seems to lead to obesity as well as a number of gut-related problems.

In recent times, numerous studies have shown that gut bacteria is crucial to our well-being; it’s important to our weight, immune system and digestive health… it may even control our mind (seriously). Anything disrupting the activity of the “good bacteria” in the gut has the potential to do massive damage. With this in mind, the scientists who conducted this new study might have found why processed food make us so fat, and why gut conditions like irritable bowel syndrome have increased since the mid-twentieth century, especially in association with processed foods.

Andrew Gewirtz at Georgia State University and his team added the two emulsifiers in varying levels to the drinking water of lab mice. They found that most healthy mice who were given the emulsifiers soon developed metabolic problems and/or became obese. When they fed mice even more emulsifiers, they started to develop inflammatory gut diseases, with the severity of the affection being directly linked to the quantity of ingested emulsifiers. These effects were seen even in mice that consumed the equivalent of just one-tenth of the concentration of the emulsifiers that the FDA permits in food products.

The researchers then wanted to see why this happens, so they tested the gut bacteria of these animals and found that the emulsifiers destroy much of the microbial fauna in the gut (again, this microbial fauna is actually beneficial to the body).

Scientists advise eating less processed foods. Image via Wiki Commons.

This is extremely worrying because it’s not easy to find emulsifier-free foods – products labeled as ‘organic’ are just as likely to contain these substances, as emulsifiers are not generally considered processed (I’m really not sure why though). Gewirtz says that many more human and animal studies need to be completed before regulatory agencies would consider changing how additives are approved – but it seems clear that we need to change the way we approve and the way we eat, especially when it comes to processed foods.

The next step would be to move on to human tests and see how our bodies are reacting to these substances. Over the past 50 years, no study has conclusively found that food additives are toxic in mammals, but then again, no large studies have ever focused on the gut bacteria.

Overall, this paper adds a lot to the idea that processed foods have long-lasting and hard to understand effects on our bodies – effects which aren’t at all positive.

Immunologist Andrew Gewirtz at Georgia State University in Atlanta who was also involved in the study concluded:

“When it comes to people making their own decisions, between our studies and others out there, it’s better to eat less processed food,” he says.

You can read the full scientific paper for free, at Nature.