Af en toe een handje zand of modder binnenkrijgen zorgt voor gezonde kinderen.
Kinderen heel hygiënisch opvoeden doet hen meer kwaad dan goed.
Dit stelt kinderneuroloog Dr. Mata Shetreat-Klein, auteur van ‘The Dirt Cure’, het succesrecept voor een gezonde kroost: ‘Bacteriën zijn goed voor ons immuunsysteem’, vertelt zij aan Vakblad Vroeg. De meeste ouders doen hun best om hun kleine kinderen zo schoon en hygiënisch mogelijk op te voeden, maar dat doet hun kroost meer kwaad dan goed, vindt Shetreat. ‘We staan vaak negatief tegenover bacteriën, maar onderzoeken concluderen steeds vaker dat ze goed kunnen zijn voor ons immuunsysteem. Er zijn zelfs concrete studies die aanwijzen dat kinderen die in huishoudens opgroeien waar vaak bleekmiddel wordt gebruikt, vaker ziek zijn dan gezinnen die het niet gebruiken.’
Driemaal per week in bad
Ze adviseert kinderen ook hooguit drie keer te douchen, zodat de natuurlijke oliën op de huid behouden blijven, zodat de kinderhuid voldoende gehydrateerd blijft. Deze zijn ook belangrijk om de vitamine D van zonlicht goed te kunnen absorberen. Toen de dochter van Seatreat allergisch voor soja en zuivel bleek, besloot ze dieper in te gaan op de omgevingsfactoren op de gezondheid van kinderen. Wat resulteerde in haar boek ‘The dirt cure’.
(Waking Times | Karen Foster) Researchers have long suggested a link between the gut-brain axis and neuropsychiatric disorders such as autism, depression, and eating disorders. Using probiotics and prebiotics to alter the gut microbiota and influence the gut-brain axis may open up new ways of influencing neuropsychological conditions, says a new review.
The majority of the science for probiotics has focused on gut health, but as the understanding of the gut and the microbiome increases, probiotics are increasing linked to a range of beneficial effects, from weight management to immune support and allergy response, and from oral health to cholesterol reduction.
The gut contains microorganisms that share a structural similarity with the neuropeptides involved in regulating behavior, mood, and emotion – a phenomenon known as molecular mimicry.
At the “forefront of current research” is work on the gut-brain axis – the two direction communication between the gut microbiota and the brain. Data from rodent studies has indicated that modification of the gut microbiota can alter signaling mechanisms, emotional behavior, and instinctive reflexes.
Researchers have long postulated that gut bacteria influence brain function. A century ago, Russian embryologist Elie Metchnikoff surmised that a healthy colonic microbial community could help combat senility and that the friendly bacterial strains found in sour milk and yogurt would increase a person’s longevity.
According to a new review in Neuropsychiatric Disease and Treatment by Linghong Zhou and Jane Foster from McMaster University in Canada, communication channels between the gut and the brain include sympathetic and parasympathetic nerves and the enteric nervous system (ENS).
“The role of the sympathetic nervous system in the gut-brain axis includes regulating motility, blood flow, barrier function, and immune system activation”, they said. “Bidirectional communication via the vagus nerve, a component of the parasympathetic nervous system, is a well-established pathway for gut-brain signaling and, in recent years, has emerged as an important microbiota to brain communication pathway.“The ENS, sometimes referred to as “the second brain” comprises intrinsic primary afferent neurons, motor neurons, and glial cells contained within the myenteric plexus and the submucosal plexus that extends along the entire length of the gut. The ENS plays an essential role in normal intestinal function including motility and secretion.”
The body can’t tell the difference between the structure of these mimics and its own cells, so antibodies could end up attacking both, potentially altering the physiology of the gut-brain axis. The bacteria present in the gut affects the communication between belly and brain, they said, and the lack of healthy gut microbiota lead to dysfunction in the gut-brain axis, which in turn may lead to neuropsychological, metabolic, and gastrointestinal disorders.
Intervention trials with select strains of probiotics have revealed that supplementation may influence mood (Lactobacillus casei Shirota), and anxiety and depression (L. helveticus and B. longum). There is also some data to support an effect with prebiotics, with improvements in stress hormone levels and attention in health volunteers taking oligosaccharides.
The role of the gut microbiota in the development of neuropsychological disorders is also a focus for many researchers around the world, with data supporting an association between dysbiosis (microbial imbalance) in the gut and disorders including depression and autism spectrum disorder, metabolic disorders such as obesity, and gastrointestinal disorders including IBD and IBS.
“Fortunately, studies have also indicated that gut microbiota may be modulated with the use of probiotics, antibiotics, and fecal microbiota transplants as a prospect for therapy in microbiota-associated diseases”, wrote Zhou and Foster. “This modulation of gut microbiota is currently a growing area of research as it just might hold the key to treatment.”
The power of probiotics
Probiotics offset other intestinal bacteria that produce putrefactive and carcinogenic toxins. If harmful bacteria dominate the intestines, essential vitamins and enzymes are not produced and the level of harmful substances rises leading to cancer, liver and kidney disease, hypertension, arteriosclerosis and abnormal immunity. Harmful bacteria can proliferate under many different circumstances including peristalsis disorders, surgical operations of the stomach or small intestine, liver or kidney diseases, pernicious anaemia, cancer, radiation or antibiotic therapies, chemotherapy, immune disorders, emotional stress, poor diets and aging
The best known of the probiotics are the Lactobacilli, a number of species of which (acidophilus, bulgaricus, casei and sporogenes) reside in the human intestine in a symbiotic relationship with each other and with other microorganisms (the friendly Streptococci, E. coli and Bifidobacteria). Lactobacilli are essential for maintaining gut microfloral health, but the overall balance of the various microorganisms in the gut is what is most important.
Another probiotic which has recently generated a great deal of interest is the friendly yeast known as Saccharomyces boulardii, an organism that belongs to the Brewer’s Yeast family, not the Candida albicans group. S. boulardii is not a permanent resident of the intestine but, taken orally, it produces lactic acid and some B vitamins, and has an overall immune enhancing effect. In fact, it has been used therapeutically to fight candida infections.
Six surprising facts about microbes in your gut 1. What’s in your gut may affect the size of your gut
Need to lose weight? Why not try a gut bacteria transplant?New research published in the journal Sciencesuggests that the microbes in your gut may play a role in obesity.
2. Probiotics may treat anxiety and depression
Scientists have been exploring the connection between gut bacteria and chemicals in the brain for years. New research adds more weight to the theory that researchers call “the microbiome–gut–brain axis.”Research published in Proceedings of the National Academy of Science shows that mice fed the bacterium Lactobacillus rhamnosus showed fewer symptoms of anxiety and depression. Researchers theorize that this is because L. rhamnosus acts on the central gamma-aminobutyric acid (GABA) system, which helps regulate emotional behavior. L. rhamnosus, which is available as a commercial probiotic supplement, has also been linked to the prevention of diarrhea, atopic dermatitis, and respiratory tract infections.
3. The more bacteria the better
While bacteria on the outside of your body can cause serious infections, the bacteria inside your body can protect against it. Studies have shown that animals without gut bacteria are more susceptible to serious infections.Bacteria found naturally inside your gut have a protective barrier effect against other living organisms that enter your body. They help the body prevent harmful bacteria from rapidly growing in your stomach, which could spell disaster for your bowels. To do this, they develop a give-and-take relationship with your body. “The host actively provides a nutrient that the bacterium needs, and the bacterium actively indicates how much it needs to the host,” according to research published in The Lancet.
4. Gut bacteria pass from mother to child in breast milk
It’s common knowledge that a mother’s milk can help beef up a baby’s immune system. New research indicates that the protective effects of gut bacteria can be transferred from mother to baby during breastfeeding. Work published in Environmental Microbiology shows that important gut bacteria travels from mother to child through breast milk to colonize a child’s own gut, helping his or her immune system to mature.
5. Lack of gut diversity is linked to allergies
Too few bacteria in the gut can throw the immune system off balance and make it go haywire with hay fever.
Researchers in Copenhagen reviewed the medical records and stool samples of 411 infants. They found that those who didn’t have diverse colonies of gut bacteria were more likely to develop allergies. But before you throw your gut bacteria a proliferation party, know that they aren’t always beneficial.
6. Gut bacteria can hurt your liver
Your liver gets 70 percent of its blood flow from your intestines, so it’s natural they would share more than just oxygenated blood. Italian researchers found that between 20 and 75 percent of patients with chronic fatty liver disease–the kind not associated with alcoholism–also had an overgrowth of gut bacteria. Some believe that the transfer of gut bacteria to the liver could be responsible for chronic liver disease.
Research is increasingly showing a mind-body connection. Did you know, for example, that depression could be a result of bacteria in your gut?
In 2012, scientists at University College Cork discovered that brain levels of serotonin, or the ‘happy hormone,’ are regulated by the amount of bacteria in the gut during early life. In other words, normal adult brain function depends on the presence of gut microbes from when you were a child.
But even as an adult, gut bacteria, or microbiome, seems to affect mood. It helps to maintain brain function and influences the risk of psychiatric and neurological disorders like depression.
To better understand how this works, Dr. Willa Hsueh, from the Division of Endocrinology, Diabetes and Metabolism at Ohio State University’s Wexner Medical Center, explains that gut microbiome produce enzymes that make metabolites, or small molecules that result from metabolism, from the foods we eat. Many of these metabolites affect brain, neuroendocrine, and neurological function.
“The species of bacteria that people develop are impacted by many factors including type of food ingested, environment, presence of obesity and other diseases, infections and treatment with antibiotics,” says Dr. Hsueh.
Got serotonin? Dr. Patrick Fratellone, MD, FIM, RH (AHG), an integrative MD and herbalist, says 90 percent of serotonin, or the ‘happy hormone,’ is made in the small intestines.
Multiple insults to the gut can cause low serotonin. An important one can be caused by certain food allergies or sensitivities, Dr. Fratellone says, like non-celiac gluten sensitivity or celiac disease. People who have a gluten sensitivity or allergy may experience depression, anxiety, insomnia, and lack of focus/concentration. “Each of these is caused by changes in the neurotransmitters caused by the low serotonin level,” he says, “accompanied by low levels of vitamin D3.”
Other causes include overgrowth of candida, accumulation of metals in the body, and chronic infections, Dr. Fratellone says.
It’s possible to test for gut flora and the presence of an overgrowth of certain bacteria strains, which are known to influence symptoms of anxiety and depression, says Dr. James Greenblatt, M.D., Chief Medical Officer and Vice President of Medical Services at Walden Behavioral Care and assistant clinical professor of psychiatry at Tufts University School of Medicine.
Dr. Fratellone recommends doing a blood test for allergies as well as starting a rotation and elimination dietary lifestyle. If the blood test is positive for celiac, then eliminating all gluten will result in a positive change in mood.
In addition to finding and treating the underlying cause, there are many supplements, vitamins, and herbs that help with digestion. “This will lead to changes in the neurochemistry, thus making the individual feel better,” says Dr. Fratellone. Some of these supplements include the amino acid glutamine and a probiotic. Herbs that have been shown to help alleviate gastrointestinal distress are Meadowsweet, Marsh mallow, Slippery Elm, and deglycerrhized licorice.
The bottom line is that it’s safe for women with depression to take high dose probiotics to help alleviate symptoms by maintaining a healthy gut balance, says Dr. Greenblatt.
The University College Cork study showed that the serotonin-bacteria influence was sex dependent, with more effects in male compared with female animals.
Dr. Greenblatt cites a 2014 study published in Nature Communications. The study found that the microbes living in the guts of females and males react differently to diet, even if the diets are identical. “Genetics, lifestyle, diet and stress can affect the variety and abundance of certain strains of microbes in the gut, which can have a profound effect on mental health and well-being,” says Dr. Greenblatt. He says it’s unclear why women and men react differently to certain diets, but it could potentially be due to the different hormones produced by the different sexes, which affect the habitat of the gut microbiome. “Despite the differences, women are not necessarily more prone to this connection,” he says.
On the horizon
The good news is the more scientists learn about this phenomenon, the greater the benefit to our overall health. A Colorado professor is studying whether beneficial microbes can be used to treat or prevent stress-related psychiatric conditions, including depression. Ultimately, brain disorders may be treated through the gut, a much easier target for drug delivery than the brain.
Earlier this year, researchers gave 40 healthy young adults a powdered probiotic supplement every night for four weeks or a placebo, Dr. Greenblatt says. “The group that consumed the probiotic supplement began to see improvement in their moods and reported less reactivity to bouts of sadness, and had fewer depressive thoughts when compared to the non-probiotic group,” he adds. “Although preliminary, the results are promising in demonstrating the potential of probiotics as a safe and cost-effective therapy to help prevent and treat depression.”
Eventually, “the goal would be to measure bacteria and metabolites in a stool sample to determine whether there are microbiome and metabolite changes that predict or are causative of depression,” says Dr. Hsueh.
Experiencing the connection
Kim Rullo has irritable bowel syndrome (IBS) and depression/anxiety. She’s read about gut bacteria affecting overall health in terms of immunity issues, inflammation, and the like, so she says she wouldn’t be surprised if they were related somehow.
“I am always looking for ways to alleviate depression symptoms, whether it be exercise or other,” says Rullo. “I did a regimen of Activia and exercise when I was having severe stomach issues, and that seemed to positively affect my overall health.” She says with more research, she would probably explore a simple regimen once again to help her general wellness.
Another woman who has depression (and asked for her name to be withheld) says she definitely agrees with the gut-mental connection. “It’s very real,” she says. She’s been using a magnesium supplement every day for a year, and it has totally helped her get over depression. She never realized the connection before. Sure enough, magnesium is necessary for serotonin production.
She only heard about the supplement because she started seeing an acupuncturist, as traditional therapy wasn’t helping. Even though she went to the acupuncturist for depression, she was asked about how often she goes to the bathroom. The supplement was one of the first things recommended.
Of course, she did her own research as well. She read a lot of reviews and talked to her doctor. “[The supplement] has become a necessity for me,” she says. “For me, what I eat, my weight, constipation, and depression are all connected. Taking constipation out of the mix has helped break a vicious cycle.”
Denkfouten zorgen ervoor dat de landbouw en veehouderij een moeizame toekomst tegemoet gaan. Het roer moet om, vindt Jan Feersma Hoekstra van Agriton. Het kortetermijndenken, met de nadruk op een zo hoog mogelijke productie, heeft geen toekomst.
De aandacht moet gaan naar een goede gezondheid van bodem en vee. Microbiologie lijkt hierbij het toverwoord.
The rich array of microbiota in our intestines can tell us more than you might think.
Eighteen vials were rocking back and forth on a squeaky mechanical device the shape of a butcher scale, and Mark Lyte was beside himself with excitement. ‘‘We actually got some fresh yesterday — freshly frozen,’’ Lyte said to a lab technician. Each vial contained a tiny nugget of monkey feces that were collected at the Harlow primate lab near Madison, Wis., the day before and shipped to Lyte’s lab on the Texas Tech University Health Sciences Center campus in Abilene, Tex.
Lyte’s interest was not in the feces per se but in the hidden form of life they harbor. The digestive tube of a monkey, like that of all vertebrates, contains vast quantities of what biologists call gut microbiota. The genetic material of these trillions of microbes, as well as others living elsewhere in and on the body, is collectively known as the microbiome. Taken together, these bacteria can weigh as much as six pounds, and they make up a sort of organ whose functions have only begun to reveal themselves to science. Lyte has spent his career trying to prove that gut microbes communicate with the nervous system using some of the same neurochemicals that relay messages in the brain.
Inside a closet-size room at his lab that afternoon, Lyte hunched over to inspect the vials, whose samples had been spun down in a centrifuge to a radiant, golden broth. Lyte, 60, spoke fast and emphatically. ‘‘You wouldn’t believe what we’re extracting out of poop,’’ he told me. ‘‘We found that the guys here in the gut make neurochemicals. We didn’t know that. Now, if they make this stuff here, does it have an influence there? Guess what? We make the same stuff. Maybe all this communication has an influence on our behavior.’’
Since 2007, when scientists announced plans for a Human Microbiome Project to catalog the micro-organisms living in our body, the profound appreciation for the influence of such organisms has grown rapidly with each passing year. Bacteria in the gut produce vitamins and break down our food; their presence or absence has been linked to obesity, inflammatory bowel disease and the toxic side effects of prescription drugs. Biologists now believe that much of what makes us human depends on microbial activity. The two million unique bacterial genes found in each human microbiome can make the 23,000 genes in our cells seem paltry, almost negligible, by comparison. ‘‘It has enormous implications for the sense of self,’’ Tom Insel, the director of the National Institute of Mental Health, told me. ‘‘We are, at least from the standpoint of DNA, more microbial than human. That’s a phenomenal insight and one that we have to take seriously when we think about human development.’’
Given the extent to which bacteria are now understood to influence human physiology, it is hardly surprising that scientists have turned their attention to how bacteria might affect the brain. Micro-organisms in our gut secrete a profound number of chemicals, and researchers like Lyte have found that among those chemicals are the same substances used by our neurons to communicate and regulate mood, like dopamine, serotonin and gamma-aminobutyric acid (GABA). These, in turn, appear to play a function in intestinal disorders, which coincide with high levels of major depression and anxiety. Last year, for example, a group in Norway examined feces from 55 people and found certain bacteria were more likely to be associated with depressive patients.
At the time of my visit to Lyte’s lab, he was nearly six months into an experiment that he hoped would better establish how certain gut microbes influenced the brain, functioning, in effect, as psychiatric drugs. He was currently compiling a list of the psychoactive compounds found in the feces of infant monkeys. Once that was established, he planned to transfer the microbes found in one newborn monkey’s feces into another’s intestine, so that the recipient would end up with a completely new set of microbes — and, if all went as predicted, change their neurodevelopment. The experiment reflected an intriguing hypothesis. Anxiety, depression and several pediatric disorders, including autism and hyperactivity, have been linked with gastrointestinal abnormalities. Microbial transplants were not invasive brain surgery, and that was the point: Changing a patient’s bacteria might be difficult but it still seemed more straightforward than altering his genes.
When Lyte began his work on the link between microbes and the brain three decades ago, it was dismissed as a curiosity. By contrast, last September, the National Institute of Mental Health awarded four grants worth up to $1 million each to spur new research on the gut microbiome’s role in mental disorders, affirming the legitimacy of a field that had long struggled to attract serious scientific credibility. Lyte and one of his longtime colleagues, Christopher Coe, at the Harlow primate lab, received one of the four. ‘‘What Mark proposed going back almost 25 years now has come to fruition,’’ Coe told me. ‘‘Now what we’re struggling to do is to figure out the logic of it.’’ It seems plausible, if not yet proved, that we might one day use microbes to diagnose neurodevelopmental disorders, treat mental illnesses and perhaps even fix them in the brain.
In 2011, a team of researchers at University College Cork, in Ireland, and McMaster University, in Ontario, published a study in Proceedings of the National Academy of Science that has become one of the best-known experiments linking bacteria in the gut to the brain. Laboratory mice were dropped into tall, cylindrical columns of water in what is known as a forced-swim test, which measures over six minutes how long the mice swim before they realize that they can neither touch the bottom nor climb out, and instead collapse into a forlorn float. Researchers use the amount of time a mouse floats as a way to measure what they call ‘‘behavioral despair.’’ (Antidepressant drugs, like Zoloft and Prozac, were initially tested using this forced-swim test.)
For several weeks, the team, led by John Cryan, the neuroscientist who designed the study, fed a small group of healthy rodents a broth infused with Lactobacillus rhamnosus, a common bacterium that is found in humans and also used to ferment milk into probiotic yogurt. Lactobacilli are one of the dominant organisms babies ingest as they pass through the birth canal. Recent studies have shown that mice stressed during pregnancy pass on lowered levels of the bacterium to their pups. This type of bacteria is known to release immense quantities of GABA; as an inhibitory neurotransmitter, GABA calms nervous activity, which explains why the most common anti-anxiety drugs, like Valium and Xanax, work by targeting GABA receptors.
Cryan found that the mice that had been fed the bacteria-laden broth kept swimming longer and spent less time in a state of immobilized woe. ‘‘They behaved as if they were on Prozac,’’ he said. ‘‘They were more chilled out and more relaxed.’’ The results suggested that the bacteria were somehow altering the neural chemistry of mice.
Until he joined his colleagues at Cork 10 years ago, Cryan thought about microbiology in terms of pathology: the neurological damage created by diseases like syphilis or H.I.V. ‘‘There are certain fields that just don’t seem to interact well,’’ he said. ‘‘Microbiology and neuroscience, as whole disciplines, don’t tend to have had much interaction, largely because the brain is somewhat protected.’’ He was referring to the fact that the brain is anatomically isolated, guarded by a blood-brain barrier that allows nutrients in but keeps out pathogens and inflammation, the immune system’s typical response to germs. Cryan’s study added to the growing evidence that signals from beneficial bacteria nonetheless find a way through the barrier. Somehow — though his 2011 paper could not pinpoint exactly how — micro-organisms in the gut tickle a sensory nerve ending in the fingerlike protrusion lining the intestine and carry that electrical impulse up the vagus nerve and into the deep-brain structures thought to be responsible for elemental emotions like anxiety. Soon after that, Cryan and a co-author, Ted Dinan, published a theory paper in Biological Psychiatry calling these potentially mind-altering microbes ‘‘psychobiotics.’’
It has long been known that much of our supply of neurochemicals — an estimated 50 percent of the dopamine, for example, and a vast majority of the serotonin — originate in the intestine, where these chemical signals regulate appetite, feelings of fullness and digestion. But only in recent years has mainstream psychiatric research given serious consideration to the role microbes might play in creating those chemicals. Lyte’s own interest in the question dates back to his time as a postdoctoral fellow at the University of Pittsburgh in 1985, when he found himself immersed in an emerging field with an unwieldy name: psychoneuroimmunology, or PNI, for short. The central theory, quite controversial at the time, suggested that stress worsened disease by suppressing our immune system.
By 1990, at a lab in Mankato, Minn., Lyte distilled the theory into three words, which he wrote on a chalkboard in his office: Stress->Immune->Disease. In the course of several experiments, he homed in on a paradox. When he dropped an intruder mouse in the cage of an animal that lived alone, the intruder ramped up its immune system — a boost, he suspected, intended to fight off germ-ridden bites or scratches. Surprisingly, though, this did not stop infections. It instead had the opposite effect: Stressed animals got sick. Lyte walked up to the board and scratched a line through the word ‘‘Immune.’’ Stress, he suspected, directly affected the bacterial bugs that caused infections.
To test how micro-organisms reacted to stress, he filled petri plates with a bovine-serum-based medium and laced the dishes with a strain of bacterium. In some, he dropped norepinephrine, a neurochemical that mammals produce when stressed. The next day, he snapped a Polaroid. The results were visible and obvious: The control plates were nearly barren, but those with the norepinephrine bloomed with bacteria that filigreed in frostlike patterns. Bacteria clearly responded to stress.
Then, to see if bacteria could induce stress, Lyte fed white mice a liquid solution of Campylobacter jejuni, a bacterium that can cause food poisoning in humans but generally doesn’t prompt an immune response in mice. To the trained eye, his treated mice were as healthy as the controls. But when he ran them through a plexiglass maze raised several feet above the lab floor, the bacteria-fed mice were less likely to venture out on the high, unprotected ledges of the maze. In human terms, they seemed anxious. Without the bacteria, they walked the narrow, elevated planks.
Credit Illustration by Andrew Rae
Each of these results was fascinating, but Lyte had a difficult time finding microbiology journals that would publish either. ‘‘It was so anathema to them,’’ he told me. When the mouse study finally appeared in the journal Physiology & Behavior in 1998, it garnered little attention. And yet as Stephen Collins, a gastroenterologist at McMaster University, told me, those first papers contained the seeds of an entire new field of research. ‘‘Mark showed, quite clearly, in elegant studies that are not often cited, that introducing a pathological bacterium into the gut will cause a change in behavior.’’
Lyte went on to show how stressful conditions for newborn cattle worsened deadly E. coli infections. In another experiment, he fed mice lean ground hamburger that appeared to improve memory and learning — a conceptual proof that by changing diet, he could change gut microbes and change behavior. After accumulating nearly a decade’s worth of evidence, in July 2008, he flew to Washington to present his research. He was a finalist for the National Institutes of Health’s Pioneer Award, a $2.5 million grant for so-called blue-sky biomedical research. Finally, it seemed, his time had come. When he got up to speak, Lyte described a dialogue between the bacterial organ and our central nervous system. At the two-minute mark, a prominent scientist in the audience did a spit take.
‘‘Dr. Lyte,’’ he later asked at a question-and-answer session, ‘‘if what you’re saying is right, then why is it when we give antibiotics to patients to kill bacteria, they are not running around crazy on the wards?’’
Lyte knew it was a dismissive question. And when he lost out on the grant, it confirmed to him that the scientific community was still unwilling to imagine that any part of our neural circuitry could be influenced by single-celled organisms. Lyte published his theory in Medical Hypotheses, a low-ranking journal that served as a forum for unconventional ideas. The response, predictably, was underwhelming. ‘‘I had people call me crazy,’’ he said.
But by 2011 — when he published a second theory paper in Bioessays, proposing that probiotic bacteria could be tailored to treat specific psychological diseases — the scientific community had become much more receptive to the idea. A Canadian team, led by Stephen Collins, had demonstrated that antibiotics could be linked to less cautious behavior in mice, and only a few months before Lyte, Sven Pettersson, a microbiologist at the Karolinska Institute in Stockholm, published a landmark paper in Proceedings of the National Academy of Science that showed that mice raised without microbes spent far more time running around outside than healthy mice in a control group; without the microbes, the mice showed less apparent anxiety and were more daring. In Ireland, Cryan published his forced-swim-test study on psychobiotics. There was now a groundswell of new research. In short order, an implausible idea had become a hypothesis in need of serious validation.
Late last year, Sarkis Mazmanian, a microbiologist at the California Institute of Technology, gave a presentation at the Society for Neuroscience, ‘‘Gut Microbes and the Brain: Paradigm Shift in Neuroscience.’’ Someone had inadvertently dropped a question mark from the end, so the speculation appeared to be a definitive statement of fact. But if anyone has a chance of delivering on that promise, it’s Mazmanian, whose research has moved beyond the basic neurochemicals to focus on a broader class of molecules called metabolites: small, equally druglike chemicals that are produced by micro-organisms. Using high-powered computational tools, he also hopes to move beyond the suggestive correlations that have typified psychobiotic research to date, and instead make decisive discoveries about the mechanisms by which microbes affect brain function.
Two years ago, Mazmanian published a study in the journal Cell with Elaine Hsiao, then a graduate student and now a neuroscientist at Caltech, and others, that made a provocative link between a single molecule and behavior. Their research found that mice exhibiting abnormal communication and repetitive behaviors, like obsessively burying marbles, were mollified when they were given one of two strains of the bacterium Bacteroides fragilis.
The study added to a working hypothesis in the field that microbes don’t just affect the permeability of the barrier around the brain but also influence the intestinal lining, which normally prevents certain bacteria from leaking out and others from getting in. When the intestinal barrier was compromised in his model, normally ‘‘beneficial’’ bacteria and the toxins they produce seeped into the bloodstream and raised the possibility they could slip past the blood-brain barrier. As one of his colleagues, Michael Fischbach, a microbiologist at the University of California, San Francisco, said: ‘‘The scientific community has a way of remaining skeptical until every last arrow has been drawn, until the entire picture is colored in. Other scientists drew the pencil outlines, and Sarkis is filling in a lot of the color.’’
Mazmanian knew the results offered only a provisional explanation for why restrictive diets and antibacterial treatments seemed to help some children with autism: Altering the microbial composition might be changing the permeability of the intestine. ‘‘The larger concept is, and this is pure speculation: Is a disease like autism really a disease of the brain or maybe a disease of the gut or some other aspect of physiology?’’ Mazmanian said. For any disease in which such a link could be proved, he saw a future in drugs derived from these small molecules found inside microbes. (A company he co-founded, Symbiotix Biotherapies, is developing a complex sugar called PSA, which is associated with Bacteroides fragilis, into treatments for intestinal disease and multiple sclerosis.) In his view, the prescriptive solutions probably involve more than increasing our exposure to environmental microbes in soil, dogs or even fermented foods; he believed there were wholesale failures in the way we shared our microbes and inoculated children with these bacteria. So far, though, the only conclusion he could draw was that disorders once thought to be conditions of the brain might be symptoms of microbial disruptions, and it was the careful defining of these disruptions that promised to be helpful in the coming decades.
The list of potential treatments incubating in labs around the world is startling. Several international groups have found that psychobiotics had subtle yet perceptible effects in healthy volunteers in a battery of brain-scanning and psychological tests. Another team in Arizona recently finished an open trial on fecal transplants in children with autism. (Simultaneously, at least two offshore clinics, in Australia and England, began offering fecal microbiota treatments to treat neurological disorders, like multiple sclerosis.) Mazmanian, however, cautions that this research is still in its infancy. ‘‘We’ve reached the stage where there’s a lot of, you know, ‘The microbiome is the cure for everything,’ ’’ he said. ‘‘I have a vested interest if it does. But I’d be shocked if it did.’’
Lyte issues the same caveat. ‘‘People are obviously desperate for solutions,’’ Lyte said when I visited him in Abilene. (He has since moved to Iowa State’s College of Veterinary Medicine.) ‘‘My main fear is the hype is running ahead of the science.’’ He knew that parents emailing him for answers meant they had exhausted every option offered by modern medicine. ‘‘It’s the Wild West out there,’’ he said. ‘‘You can go online and buy any amount of probiotics for any number of conditions now, and my paper is one of those cited. I never said go out and take probiotics.’’ He added, ‘‘We really need a lot more research done before we actually have people trying therapies out.’’
If the idea of psychobiotics had now, in some ways, eclipsed him, it was nevertheless a curious kind of affirmation, even redemption: an old-school microbiologist thrust into the midst of one of the most promising aspects of neuroscience. At the moment, he had a rough map in his head and a freezer full of monkey fecals that might translate, somehow, into telling differences between gregarious or shy monkeys later in life. I asked him if what amounted to a personality transplant still sounded a bit far-fetched. He seemed no closer to unlocking exactly what brain functions could be traced to the same organ that produced feces. ‘‘If you transfer the microbiota from one animal to another, you can transfer the behavior,’’ Lyte said. ‘‘What we’re trying to understand are the mechanisms by which the microbiota can influence the brain and development. If you believe that, are you now out on the precipice? The answer is yes. Do I think it’s the future? I think it’s a long way away.’’
Correction: June 25, 2015
An earlier version of this article described incorrectly the affiliation of Elaine Hsiao, an author of a study published in the journal Cell that linked bacteria to behavioral changes. At the time, she was a graduate student in the lab of Paul Patterson, another author of the study, not in the lab of Sarkis Mazmanian.
Mensen met hooikoorts of seizoensgebonden allergie zijn mogelijk gebaat bij probiotica. Dit blijkt uit een verzameling van verschillende studies naar dit onderwerp.
Onderzoekers van het Vanderbilt Medical Center in Nashville bestudeerden 23 eerder uitgevoerde studies met in totaal 1.919 proefpersonen.
Er wordt gedacht dat de toename in allergieën deels toe te schrijven valt aan een gebrek aan bacteriën in de darmen als gevolg van de schonere leefomstandigheden.
Als je in een heel schone omgeving woont, kom je niet voldoende in contact met micro-organismen waardoor je immuunsysteem overuren gaat draaien als het in contact komt met onschadelijke allergenen. Probiotica zouden dit mogelijk kunnen verbeteren door de hoeveelheid goede bacteriën in het spijsverteringskanaal te vergroten.
De kwaliteit van de onderzoeken varieerden. Mede daarom geven de wetenschappers aan dat meer onderzoek nodig is voor dat probiotica als behandeling kan worden geadviseerd bij hooikoorts.
Van de studies die de onderzoekers bestudeerden, toonden zeventien een verbetering van de klachten of kwaliteit van leven door het gebruik van probiotica in vergelijking tot mensen die een placebo nuttigden.
Binnen de overige zes onderzoeken werd echter geen verbetering gevonden. De resultaten van de review zijn veelbelovend, maar aangezien in de studies verschillende probiotica werden gebruikt binnen verschillende onderzoeksgroepen vinden de onderzoekers het te vroeg om probiotica daadwerkelijk aan te bevelen.
Het gebruik van probiotica zorgt er voor dat mensen minder piekeren. Daarmee zou het middel in de toekomst een aanvullende of preventieve therapie kunnen zijn tegen depressies. Dat blijkt uit onderzoek van de universiteiten van Amsterdam en Leiden, gepubliceerd in Brain, Behavior, and Immunity.
Daarnaast is ook aangetoond dat probiotica mogelijk werken tegen migraine, zo wijst een nieuwe pilotstudie van de Universiteit van Wageningen uit.
Dit is de eerste keer dat onderzocht is of het toedienen van probiotica werkt tegen piekeren. “Piekeren is het hebben van terugkerende gedachten over mogelijke oorzaken en gevolgen van iemands ellende en bedroefdheid”, legt onderzoeker Saskia van Hemert uit.
“Bewezen is dat piekeren een indicator is van depressies; het is een van de meeste voorspellende kwetsbaarheidsfactoren van een depressie. Probiotica zou in de toekomst mogelijk een middel tegen depressies kunnen worden, aangezien uit het onderzoek blijkt dat probiotica piekeren kan voorkomen”, aldus van Hemert.
Probiotica zijn levende bacteriën die, wanneer toegediend in adequate hoeveelheden, functioneel zijn in onder andere het verbeteren van de spijsvertering en het immuunsysteem. De onderzoeksgroep in het onderzoek piekerde na deze vier weken significant minder dan de controlegroep.
Probiotica is niet alleen werkzaam tegen piekeren, ook migraines worden mogelijk verholpen door de micro-organismen.
De onderzoeksgroep van de Universiteit van Wageningen zag het aantal migrainedagen met 25 procent afnemen. De hypothese is dat probiotica een positief effect hebben op de darmbarrière en daardoor migraine voorkomt.
Verstoring van de darmbarrière zou namelijk migraineaanvallen kunnen uitlokken en het is bekend dat probiotica de darmbarrière kunnen versterken.
Momenteel loopt er een nieuwe studie aan de Universiteit van Wageningen, waarin het positieve effect van probiotica op migraine nader onderzocht wordt. De resultaten van deze studie worden aan het eind van het jaar verwacht.
Microferm (EM-Actief) wordt gebruikt als probiotica.