Home | Nutrition | Biotics | The Wide-Ranging Influence of Gut Microbes on Your Mental and Physical Health


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By Dr. Mercola

There are 100 trillion cells in your body, but 90% of the genetic material is not yours. It is from the bacteria, fungi, viruses and other microorganisms, i.e. your microflora. Gut microbes are big in the news lately, as researchers continue to discover the important roles these tiny organisms play in your overall health and well-being. We now know that your microflora influence your:

  • Genetic expression
  • Immune system
  • Weight, and

Most recently, research has shown that a certain set of these microbes may actually influence the activity of genes in your brain – and the parts they play are not small parts. They may work to manipulate your behavior, and your memory as well.

Microbes Manipulate Your Mind

According to a recent article in The Guardian1, certain species of gut bacteria have been found to influence gene activity in your brain. Some of this research was published in 2011.2 Mice lacking gut bacteria were found to engage in "high-risk behavior," and this altered behavior was accompanied by neurochemical changes in the mouse brain.

According to the authors, microbiota (your gut flora) may play a role in the communication between your gut and your brain, and:


But they also discovered other differences between the mice with normal gut flora and those lacking gut bacteria. When examining the animals' brains, they discovered a number of genetic alterations in the germ-free mice. According toThe Guardian:


All three genes have previously been implicated in emotion and anxiety-like behaviors.

BDNF is a growth factor that is essential for proper brain development, and a recent study showed that deleting the BDNF receptor TrkB alters the way in which newborn neurons integrate into hippocampal circuitry and increases anxiety-like behaviors in mice. Serotonin receptors, which are distributed widely throughout the brain, are well known to be involved in mood, and compounds that activate the 5HT1A subtype also produce anxiety-like behaviors.


Your Gut Bacteria Are Under Constant Assault

Your lifestyle can and does influence your gut flora on a daily basis. For example, your gut bacteria are extremely sensitive to:

  • Antibiotics
  • Chlorinated water
  • Antibacterial soap
  • Agricultural chemicals
  • Pollution

All of these common exposures can wreak havoc on the makeup of bacteria in your gut, but researchers are now increasingly looking at the cascading ill effects of antibiotics in particular.

Not only are antibiotics overused in medicine, the vast majority of these drugs enter you via livestock – you consume antibiotics every time you eat meat from an animal raised in a confined animal feeding operation (CAFO). In fact, about 80 percent of all the antibiotics produced are used in agriculture3 – not only to fight infection, but to promote unhealthy (though profitable) weight gain in the animals.

Early Use of Antibiotics Also Linked to Obesity

With that in mind, is it any wonder that researchers are now finding that antibiotics are associated with weight gain in humans as well?

"For many years now, farmers have known that antibiotics are great at producing heavier cows for market," Dr. Jan Blustein, MD, PhD, professor of population health and medicine told PreventDisease.com in a recent article.4 "While we need more research to confirm our findings, this carefully conducted study suggests that antibiotics influence weight gain in humans, and especially children..."

According to The Washington Post:5

"The use of antibiotics in young children might lead to a higher risk of obesity, and two new studies, one on mice and one on humans, conclude that changes of the intestinal bacteria caused by antibiotics could be responsible. Taken together, the New York University researchers conclude that it might be necessary to broaden our concept of the causes of obesity and urge more caution in using antibiotics."

The first study, published in the journal Nature6, found that young mice treated with low doses of common antibiotics gained 10-15 percent more fat than the untreated controls. After surveying the gut bacteria in the mice, they found that mice treated with antibiotics had a different composition of gut bacteria compared to the untreated mice. Specifically, certain species of bacteria previously shown to be associated with obesity were found in higher concentrations in the treated mice. Furthermore, after genetic analysis of the bacteria's metabolism, they discovered that genes responsible for fat synthesis had greater levels of activity in the treated mice.

According to lead author Martin Blaser:7


The co-author Dr Ilseung Cho added:8

"By using antibiotics, we found we can actually manipulate the population of bacteria and alter how they metabolize certain nutrients. Ultimately, we were able to affect body composition and development in young mice by changing their gut microbiome through this exposure."

The second study, published in the International Journal of Obesity9, aimed to corroborate these findings in human subjects. The study, which included more than 10,000 children, found that treating babies with antibiotics before the age of six months old appears to predispose them to being overweight in childhood. Children exposed to antibiotics between the ages of six to 14 months did not have significantly higher body mass than unexposed children.

While this study does not prove causation between antibiotic use in infancy and later obesity, it does show a correlation, and the mechanism appears to be related to the way antibiotics alter your child's gut flora. However, excess weight is not the only, or the worst problem that such imbalance can create. As previously explained by Dr. Natasha Campbell-McBride, children with imbalanced gut flora are more prone to develop neurological disorders, such as ADD/ADHD and various learning disorders. These children are also more prone to vaccine damage.


Total Video Length: 1:13:21
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Prebiotics Research Highlighted at American Chemical Society Meeting

Increasingly, researchers are finding that proper nutrition is not just about getting the right kind and amount of nutrients needed for biological processes. You also need to nourish these non-human cells in your body, i.e. your gut microflora. This issue was recently raised at the 244th National Meeting & Exposition of the American Chemical Society. According to a recent article in NewHope360:10

"'Just as people need food to thrive, so do the billions of healthful bacteria that live in our guts, our gastrointestinal tract,' [Robert] Rastall [Phd] explained. 'There's a large and expanding body of scientific evidence that bacteria in the gut play a role in health and disease. Prebiotics are foods that contain nutrients that support the growth and activity of these friendly bacteria.'

Rastall contrasted prebiotics to the more familiar probiotics, already being promoted on the labels of food like yogurt and some dietary supplements.

Probiotic foods actually contain friendly bacteria like Lactobacillus acidophilus believed to release healthful substances as they grow in the GI tract. Prebiotics are indigestible food ingredients that provide no nutrition to people. Their purpose is to nourish the friendly bacteria among the estimated 100 trillion microbes living inside the human GI tract."

While raised awareness about the importance of prebiotics and probiotics is good news, it comes with the territory that researchers are also working on ways to produce prebiotics that can easily be added to processed foods. Pre- and probiotics are very sensitive to heat, and excessive heat-treatment is a hallmark of most processed foods. It therefore stands to reason that any prebiotic inventions they come up with for the processed foods market will inevitably be of inferior quality, and I strongly recommend avoiding any and all processed foods that proclaim to contain prebiotics or probiotics, and stick with the real thing, i.e. traditionally fermented foods for healthful probiotics, and unprocessed whole foods for prebiotics, such as onions and garlic.

Study Finds "Clear Link" Between Inflammation, Bacterial Communities and Cancer

Demonstrating just how far-reaching the health impact of the bacterial balance in your gut can be, another recent study claims the key factor behind cancer appears to be ecological rather than genetic.11

Published in the journal Science12, the study suggests cancer may be due to a chain reaction that starts with inflammation that disrupts your gut ecosystems, allowing pathogens, such as E.coli, to invade your gut and cause cellular damage. The presence of E.coli was increased by a factor of 100 by inflammation, and 80 percent of germ-free mice infected with E.coli developed colorectal cancer, while germ-free mice inoculated with another common gut bacterium remained cancer-free, although these mice, like the others, did develop severe colitis (gut inflammation).

According to a press release by the University of North Carolina:13




...'As is usual in human studies, we didn't have cause and effect,' Fodor noted. 'We don't know if microbes are somehow causing conditions to shift in the gut that would cause cancer or if there are conditions that are associated with cancer that would increase the openness of the gut to particular microbes. A shift in the microbial community is associated with inflammation... It is interesting that the microbial community is actually changing with the disease state, which indicates that it is either responding to or contributing to the disease state.'"

Like Bacteria, Cancer Cells Rely on Communication and Cooperation

In related news, an article published in Trends in Microbiology14 examines the shared traits of cancer cells and bacteria. Bacteria and cancer cells both use sophisticated communication to gain supremacy within the host. As reported by Medical News Today:15

"Inspired by the social and survival tactics of bacteria, the team presents a new picture of cancer as a meta-community of smart communicating cells possessing special traits for cooperative behavior. Using intricate communication, cancer cells can distribute tasks, share resources, differentiate, and make decisions. Before sending cells to colonize organs and tissues throughout the body (metastasis), 'spying cells' explore the body and return the cancer's origin. Only then do metastatic cells leave the primary tumor and navigate to new posts.

Also like bacteria, cancer cells change their own environment. They induce genetic changes and enslave surrounding normal cells, forcing them to do the disease's bidding - providing physical support, protecting them from the immune system, and more."

Three years ago, I posted a TED video featuring Bonnie Bassler, in which she discusses how bacteria "talk" to each otherusing a chemical language that lets them coordinate defense and mount attacks. Cancer cells, as it turns out, employ similar forms of communication, and as discussed by Bassler, these discoveries pave the way for the development of drugs aimed at shutting down or altering cell-to-cell communication.


According to Medical News Today:

"The team also suggests further research into cancer 'cannibalism,' when cancer cells may consume their peers when they run out of resources. The idea is to send signals which trigger cancer cells to kill each other, which can be done with bacteria. Other researchers have demonstrated that injected bacteria can 'outsmart cancer.' Bacteria can be used to induce gap junctions between the cancer cells and immune cells, 'teaching' the immune system to recognize and kill the tumor cells."

The Phenomenal Health Benefits of Fermented Vegetables


The culturing process produces beneficial microbes that are extremely important for your health as they help balance your intestinal flora. If you do not regularly consume the traditionally fermented foods below, a high-quality probiotic supplement will provide similar benefits:

  • Fermented vegetables
  • Natto (fermented soy)




Learn to Make Your Own Fermented Vegetables



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AVOID This to Optimize Your Gut Flora!





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