A new article published in the Scientific American discusses the role that gut microbes may play in worsening symptoms of depression and anxiety in some people.
It’s been known that eating a lot of red meat is linked to having a higher risk for a heart attack, but now new evidence in animal studies and also in humans, shows that the missing link in our understanding as to why this is so, may possibly reside in an overabundance of certain bacteria found in the guts of regular meat-eaters. Gut-microbes seem to have become the darling of our times when it comes to trying to bridge the gap in our rudimentary understanding between the foods we eat and modern diseases, and the science here still remains a big unknown.
According to research just published today in the science journal Nature Medicine, understanding why regular meat-eaters have a higher risk of heart disease is a matter of simple alchemy. A lot of previous research has shown that excessive red meat consumption is correlated to a higher risk for heart disease and hardening of the arteries through increased cholesterol deposits. Now this new study conducted in mice shows that certain intestinal microbes convert a nutrient that is found in high amounts in red meat called L-carnitine into a chemical called trimethylamine-N-oxide (TMAO); and TMAO promotes cholesterol deposition in the arterial walls and reduces the effective removal of cholesterol by the body, resulting in a high risk for heart disease. Certain carnivorous or carnitine-craving bacteria seem to grow to large colonies in the guts of meat eaters that provide them with their favorite sustenance, where they convert the nutrient L-carnitine into the cholesterol-increasing compound that is so deleterious for the heart when it is overly abundant. L-carnitine is also found in smaller amounts in other foods, such as dairy products, but red meat is by far the highest source of this amino acid.
Another study looking at vegans and meat-eaters showed that when the former ate a sirloin steak the conversion of L-carnitine into the compound TMAO that can be measured in the blood was much lower compared to regular meat-eaters, where the conversion was found to be high. This seems to provide proof for the theory that there is an association between the abundance of certain gut bacteria that use L-carnitine as a substrate and the conversion into TMAO in regular meat-eaters. “It may be that a regular diet of meat encourages higher levels of L-carnitine-TMAO converting intestinal bacteria that feed on L-carnitine that in turn increase the risk of heart disease,” according to one of the study authors.
In the accompanying news article study author Stanley Hazen, head of cardiovascular medicine at the Cleveland Clinic in Ohio, stated that the findings of the study “should give pause not only to meat lovers, but also to people who take L-carnitine supplements which are heavily marketed to promote weight loss and improve athletic performance”. In a New York Times article published today, he was quoted as saying that although not a vegan and a lover of red meat, he personally would not eat a steak more than once every 2 weeks and no more than 4 to 6 ounces at a time. His previous red meat consumption was much higher.
Here’s an article in today’s NY Times on new research on the implications of changes in gut microbes leading to weight loss following gastric bypass surgery. It seems like a never-ending stream of research is emerging on this topic. Perhaps fecal transplants will be implicated as treatment in weight-loss protocols in the obese in the future?
New research published in the journal Science links emergence of sex-hormone driven autoimmune disorders to certain gut microbiota and may offer clues as to why some chronic illnesses with presumed autoimmune etiology, such as MS and rheumatoid arthritis, may be more common in women than men.
Since starting this blog journal with my first entry last year (see archives for blog entry in May and link to original article in German published in DIE WELT http://www.welt.de/print/die_welt/wissen/article106369682/Darmbakterien-machen-dick.html ) describing the association between obesity and the ecology of the human gut microbiome, a lot of solid research has emerged in this area, with mainstream media finally starting to pay increased attention to a topic that used to be subject to ridicule, and was long neglected by the scientific community and mainstream medical community at large: the vital importance of intestinal sanitation. Re-establishing a healthy intestinal flora has been more or less scorned by our modern culture, and relegated as quackery unworthy of serious scientific inquiry as portrayed in T. C. Boyle’s novel ‘Road to Wellville’ that describes the historical fictionalization of corn flakes inventor John Harvey Kellog, whose breakfast cereal business is inspired by a sojourn in a sanitorium in Michigan – an American take on Thomas Mann’s epic novel “The Zauberberg” where the tuberculosis-ridden intellectual elite whiles away in the Swiss Alps in an attempt to cure themselves with a regimen of fresh air at the beginning of the last century. Both fictional accounts satirize holistic naturopathic cures replete with the ‘taking of fresh air’ to aerate pathogen-riddled lungs, or, in the event of the former account, colonic enemas to irrigate the bowels—both rather primitive attempts at restoring health.
Somehow it feels as though the Zeitgeist has changed and we’ve entered a new cycle. It seems as though we’re collectively paying increased attention to our health again, with more of a focus on essentially natural healing methods, especially when modern medicine finds itself at wit’s end. One needs only look at the evolution of treatment-resistant microbes with antibiotics increasingly rendered useless, when they were once considered the magic bullet to curing infections. The history of medicine has seen such a renaissance going ‘back to nature’ before with Samuel Hahnemann’s homeopathic response to curing disease with low potency dilutions of substances based on what was found in the animal, mineral and vegetable kingdom and applied according to the Law’s of Nature and the principals of Similars. Dr. Hahnemann was not a friend of the contemporary medicine practiced during his times.
When the New England Journal of Medicine published findings this past week (http://www.nejm.org/doi/full/10.1056/NEJMoa1205037) of the efficacy of a fecal transplant to cure antibiotic-resistant strains of Clostridium difficile, even the New York Times picked up on it and ran a front-page story in its Global edition – the IHT. (http://www.nytimes.com/2013/01/17/health/disgusting-maybe-but-treatment-works-study-finds.html?ref=science)
When we take antibiotics we unselectively destroy and wipe out gut microbes required for a healthy gut ecology, which may result in the emergence of resistant strains to the detriment of good bacteria. This understanding is by no means new, and yet too many doctors still prescribe antibiotics without thinking twice. And so we live in an era where fecal transplants suddenly become all the rage! Another person’s healthy gut microbes become a sick person’s boon. And it works as a cure when antibiotics fail to do the trick.
Gut microbes are suddenly in. And the link to many diseases originating through an imbalance – or dysbiosis – of the billions of different strains of bacteria our human intestines harbor, is undisputable. (In fact we harbor more bacteria in our human guts than cells in our bodies, to put that into a tangible dimension). The latest research performed in mice that are often used as an animal model to study type 1 diabetes (just published in the journal Science)suggests that there is an association between the emergence of autoimmune disorders and the ecology of gut microbes that are dependent on the presence or absence of testosterone in the host. This hints at a possible sex-hormone dependent vulnerability to emergence of disease in which specific gut microbes are the pre-requisite. According to this study in mice, testosterone may confer a protection, while female animals develop disease when they harbor certain types of bacteria in their intestines.
Multiple sclerosis and rheumatoid arthritis are just two diseases for which modern medicine still has no explanation as to its precise etiology that are presumed to have some sort of a sex-linked and gut microbial origin with an inflammatory and autoimmune component like type 1 diabetes.
Another recently published study (http://www.sciencedaily.com/releases/2013/01/130118064731.htm) demonstrated how good bacteria in the gut may play an important role in preventing diabetes. When the balance is distorted, inflammation occurs and the disease develops. And even eczema in children can be traced back to these children having a more diverse set of bacteria in their guts normally associated with adults (showing clusters of so-called Clostridium clusters) according to recent findings released in the open access journal BMC Microbiology (http://www.biomedcentral.com/1471-2180/13/12/abstract).
With research into the human and also microbial genome advancing at a rapid pace, I believe the medicine of the future will be a combination of a healthy diet of whole, unprocessed foods along with lifestyle changes that are adapted to personal genetic predispositions that the field of metabolomics will help shed more light just a few years down the road. We all have a different enzymatic make up, but with a common sense approach, most chronic diseases should be almost entirely preventable. It will be more important than ever to be wise about our lifestyle choice, especially with the increase in environmental toxins – just think of the toxic metals such a mercury already poisoning our food chains – and to choose our nutrition and lifestyles wisely, where at all possible.
Stay tuned to ‘the mdjournal’ blog for more science emerging in this field of intestinal health and gut microbial genomics.
Earlier in May this year I posted the English translation of a German article I had written in the newspaper “DIe WELT” about the link between gut microbes and obesity and the enormous public health implications this knowledge has, if we improve our understanding on the association between the composition of the trillions of bacteria residing in our guts and the development of disease states such as inflammation and obesity.
Here is the link to the older post on the blog for context:
And here is a new study from China published in the science journal Nature that suggests that overgrowth of endotoxin-producing enterobacteria may lead to obesity via increased inflammation and insulin resistance. Read the open access study here: http://www.nature.com/ismej/journal/vaop/ncurrent/pdf/ismej2012153a.pdf
The complexity of the association between our gut microbial ecology and specific diseases is not to be underestimated. Most research in this area is coming up with very conflicting results when analyzing the precise gut composition and determining the ratios of different microbes residing in the gut by using metagenomic testing of stool samples. A lot more research will be coming out in this area soon, as drug companies and food industry have a very vested interest in promoting pre-biotics and pro-biotics to enhance growth of one bacteria over another. This study in China looked at a diet of whole grains and traditional chinese medicine and the impact on bacterial growth. More qualitative information on whole foods and outcome on bacterial gut ecology and the link to disease is warranted before single substitutions with both pre- and pro-biotics are to be widely recommended to public at large, in my opinion.
In the United States the public in California voted no to a proposition that genetically modified foods should be labeled as such. In Europe GMO crops are still not permitted.
Here’s my take on the issue:
Proposition 37 failed to win majority of votes in California yesterday for the Nov. 6th election. This was perhaps on the grounds of the proposition itself being poorly put together. The American Academy of the Advancement of Science endorsed the “No to Proposition 37” campaign on the grounds of lacking scientific evidence that GMO crops causes harm. However, that isn’t the point. Consumers should have a right to know what is in their food. Too bad about the weak study and lacking scientific evidence that caused much media hype coming out of France last month. It entirely back-fired and served Monsanto well and put the entire debate on weaker ground. But there seems to…
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