Heart disease is the latest health problem that's been discovered to start in the gut: instead of taking statins, heart patients could instead be treated with probiotics that repopulate the gut with healthy bacteria, say researchers. It joins a growing list of other inflammatory problems, including rheumatoid arthritis, psoriasis, inflammatory bowel disease (IBD) and multiple sclerosis, that also have their origins in the gut.
Researchers from King's College London have found that people with low diversity in their gut bacteria—known as the microbiome—are more likely to suffer from a hardening of the arteries, the first stage of atherosclerosis or cardiovascular disease.
Repopulating the gut with healthy bacteria could reverse the world's most lethal disease, the researchers say, and probiotics that contain the live micro-organisms Bifidobacterium and Lactobacillus are especially effective at countering atherosclerosis. As probiotics have been proven to reduce blood pressure, the researchers believe that the supplements could have a similar positive impact on arterial health.1
It's a breakthrough discovery that could radically change the way we see, and treat, heart disease. As with cancer, there are very few positive signs that medicine is winning the war—and that could be a symptom of the enormous gulf that separates the discoveries being made in research centers and the way the disease is still being treated.
Medicine persists with the theory that saturated fats from butter, cream and cheese and fatty meats raise our levels of cholesterol, which in turn starts clogging our arteries and eventually causes heart failure.
As such, a change of diet coupled with a prescription for statin drugs is the standard remedy. The food industry has made billions from its low-fat products, and the pharmaceutical industry has made similar amounts from their cholesterol-lowering statins—and it's all been based on a theory that has been discredited numerous times.
Probiotics and high-fiber
According to the emerging gut-heart theory, fatty foods could be playing a part in heart disease—but not in the way the current view believes. A high-fat diet can contribute to gut dysbiosis—where the healthy bacterial balance is disturbed—and this can trigger atherosclerosis and hypertension (high blood pressure), say researchers from McMaster University
But instead of expensive drugs, the King's College researchers say that a course of probiotics—and changing the diet to a high-fiber one—could be all it takes to reverse heart disease. Fiber is a plant-based carbohydrate found in cereals, fruit, vegetables and nuts—interestingly, the staples of the heralded Mediterranean diet that has been promoted as a way to protect heart health.
They monitored 617 middle-aged women, all of them twins, and assessed the health of their arteries and gut biodiversity. Although inflammation and insulin resistance are both characteristics of stiffening of the arteries, these could both be downstream causes that share the common source of low gut diversity. The researchers had suspected the gut could be playing a part in arterial disease since it's already been established that it's an important regulator of inflammation, glucose (blood sugar) tolerance and insulin sensitivity, all hallmarks of type 2 diabetes, which is itself a precursor of heart disease.
In their study, the King's College researchers discovered there was an inverse relationship between varieties of gut bacteria and arterial stiffness. In other words, the women with the lowest microbiome diversity had the stiffest arteries. They saw a similar pattern in all the women, irrespective of their weight or if they were obese.
Their discovery builds on research published last year that found a direct link between a loss of bacteria in the gut and heart failure. These drops can be caused by diseases such as type 2 diabetes or by pharmaceuticals, researchers from University Hospital Schleswig-Holstein said. 3 They examined stool samples of healthy people and heart failure patients, and although both groups had similar diets, the heart patients had "significantly lower" levels of bacterial strains known to control inflammation.
Earlier research had suggested that TMAO (trimethylamine N-oxide), a metabolic product of gut bacteria, was a risk factor for heart disease, and heart failure in particular, but it seems to be the bacteria themselves that trigger heart disease.
The heart-gut connection
It's an idea that's gaining traction. It was being discussed 10 years ago, when researchers started to theorize that changing the gut microbiome through diet and probiotics, found in foods like yogurt and kefir, could be the answer to the epidemic of heart disease. As one research team put it: "The way to a healthy heart may be through a healthy gut microbiota"—although evidence was thin on the ground. 4
One problem was that researchers didn't have the technology to test for hardening of the arteries. That's changed in the last few years with the introduction of pulse wave velocity (PWV), which has quickly established itself as the gold-standard measure of arterial health and a predictor of future heart disease.
Even without PWV, researchers were starting to see a connection. A research team from BGI-Shenzhen in China compared stool samples from 218 heart patients and 187 healthy people, and found that the gut microbiome of heart patients was unhealthy. The heart patients' samples contained two bacteria—Enterobacteriaceae and Streptococcus species—that were interfering with normal metabolism that supports cardiovascular health. 5
The science that recognizes the vital role of the gut and its ability to regulate many physiological functions, including inflammation, now has a name: immunometabolism. Explaining the new science, Dr Natalia Shulzhenko at Oregon State University said: "We're discovering that in biology there are multiple connections and communications, what we call 'cross-talk,' that are very important in ways we're just beginning to understand."
Shulzhenko and her team have been exploring the role of gut dysbiosis and type 2 diabetes and metabolic syndrome, which includes diabetes, obesity and heart disease. Essentially, these diseases appear when the cross-talk between the immune system, gut bacteria and glucose metabolism breaks down, she says. Probiotics are one way to reverse diabetes and metabolic syndrome. 6
But what causes gut dysbiosis in the first place? There could be many causes, but four that have been identified include a high-fat diet, a lack of dietary fiber, such as from vegetables, nuts and fruit, and chronic stress—and the fourth is antibiotics, she discovered.
A cocktail of antibiotics depleted the gut microbiome, which affected its ability to regulate normal immunological responses, she and her colleagues found in a series of tests on mice. 7
If doctors are still unsure about the underlying causes of heart disease, the vital role played by gut health hasn't been lost on researchers, alternative health practitioners and a growing number of patients.
In other words, probiotics will do the job better than statins.
Think microbiome and you'll think of the gut. But that may not be the whole story: researchers have discovered that the breasts have their own mini-microbiome, and that could be true for other areas of the body, too.
In fact, breast cancer could be caused by a bacterial imbalance in the mini-microbiome, say researchers at the Cleveland Clinic.1
Healthy breast tissue has more of the 'good' bacteria, Methylobacterium, the researchers discovered after they had analyzed tissue samples from 78 women who had either had a mastectomy due to breast cancer or cosmetic breast surgery with no underlying health problems. Urine samples they also examined showed raised levels of other types of bacteria, including Staphylococcus and Actinomyces, in breast cancer patients.
As with heart disease (see main article), the discovery suggests that breast cancer could also be treated with pre- and probiotics.
It's not just the cardiovascular system the gut regulates, it's also health problems that are identified as being 'in the head.' Depression, anxiety, autism, Alzheimer's disease and even Parkinson's could all have their origins in the gut.
The common link with all these problems—and many others besides—is inflammation, the body's healing and protective mechanism against injury or infection. Although inflammation is seen as a function of our immune system, that, in turn, is regulated by complex interactions with our gut.
Dr Alejando Aballay at Duke University Medical Center says the relationship is more complex still and includes a third element: our nervous system. The messenger between all three, he believes, is dopamine, a neurotransmitter that regulates the brain's feelings of reward and pleasure.
In 2009, he tested the theory on a simple life form—the nematode worm C. elegans, which has just 302 neurons compared to a human's 100 billion, and a basic immune system. In a series of studies, Abally discovered that inflammation in the worms' gut could be manipulated by changing levels of dopamine in their bodies.1
This demonstrated a connection between the immune and nervous systems, moderated by gut bacteria—a relationship that is supposed not to exist, according to current biological models.