Could Meat Lower Heart Disease Risk?

By Dr. Sean M. Wells, DPT, PT, OCS, ATC/L, CSCS, NSCA-CPT, CNPT, Cert-DN

If you were reading the news last week then you might have seen an article that sounds something like: "Good News, Meat May Protect You from Heart Disease." While this sounds exciting and promising, many of the published media articles just don't dive into the science enough to give citizens and clinicians an educated viewpoints. Let's examine the new evidence, its science, and what impact it should have on physical therapy practice.

The Article

The main research paper the media is slinging around can be found in mSystems, an open access journal. The authors, Kivenson and Giovanni, published the paper title An Expanded Genetic Code Enables Trimethylamine Metabolism in Human Gut Bacteria, which full-text can be found here. Both Kivenson and Giovanni are researchers at Oregon State University and their primary focus is in microbiology.

mSystems is a relatively new journal. Overall it has an impact factor of 6.28 on Resurchify, which compares bleakly to JAMA's 14 and New England Journal's 37. Typically a score above 10 shows the journal has a major impact on Resurchify. Using Scimago Journal and Country Rank (SJR) website, they rank mSystems well below even our Physical Therapy and Journal of Orthopedic and Sport PT Journals. I guess this shouldn't come as a surprise given it is a young, online, open-access journal.

Setting aside the journal, the article itself is a quasi-review of published data sets. The authors take a "survey" approach to reviewing selected data sets to round out their research inquiry. Let's explore the science behind the article now.

The Science

The primary inquiry of the researchers focuses on animal meat and trimethylamine (TMA), a precursor of the proatherogenic compound trimethylamine-N-oxide (TMAO). PTs that have taken our courses know that TMAO is a known byproduct of animal consumption. Choline and carnitine, both amino acids found in high concentrations in animal products like meat and eggs, are converted in the liver to TMA. Gut bacteria often covert this TMA to TMAO, which is taken through the bloodstream and promotes cardiovascular disease. This is what the process looks like:

TMAO is just one of many reasons (including excessive heme iron, saturated fat, advanced glycation end products) most of our physical therapy patients should be eating a plant-based diet.

On the contrary, these researchers sought out to find a strain of bacteria in the gut that could process the TMA to not produce TMAO. They knew that eating meat increased certain bacteria, one of which is known as Bilophila wadsworthia. Bilophila was first found in a appendix many years ago, is a known pathological bacteria, and has genes necessary for encoding pyrrolysine, which has been suggested to demethylate. Bilophila is associated with inflammatory bowel disease, hydrogen gas production, amongst other "bad" things.

The researchers then scoured the literature to find at least one human and one mouse data sets to begin their analysis. After surveying these data sets, the authors found that Bilophila appeared to be able to convert TMA to a safer compound known as DMA through demethylation and other processes. It looks something like this:

Got all that? Yikes! Continuing on, the authors cited "the fraction of TMA consumed via this bacterial metabolic process in the human gut microbiome remains uncertain, but expression data support the conclusion that this metabolic process is active." In short, the authors' diagrams and summaries all point to the fact that this bacteria could be utilized in some capacity to reduce TMAO, and heart disease, through the use of probiotics or other gut biome manipulations.

Physical Therapy Implications and Discussion

First, I think we should take this article for a grain of salt. It is an open-access journal that is new and with minimal impact. Secondly, the article design is survey-based with no actual manipulation of genes, proteins, etc by the authors. Thirdly, have the data sets used were from mice: human gut biomes varying dramatically from those of rodents.

Furthermore, I think we ought to take a logical step backwards. The researchers in their introductory paragraph cite that meat consumption often causes a spike in Bilophila. If this is the case, then meat consumption itself ought to promote more conversion of TMAO to TMA. A great drop in TMAO ought to translate into lower cardiovascular heart disease risk, right? This is what some of the media, Carnivore pundits, and want-to-be scientists were hoping to hear: eat more meat to boost this bacteria and cut your heart disease risk.

Unfortunately it does not pan out with such logic. A high meat diet is associated with higher rates of mortality, cancer, heart disease, diabetes and obesity. This we know based on large epidemiology studies from various human data sets around the world. Hence why physios should be encouraging their patients to stick a predominantly plant-based diet.

Putting aside these limitations, these researchers have opened the door to showing certain gut bacteria may be helpful in reducing heart disease. It should be stressed that the authors show a reduction in TMAO, not an elimination. How we manipulate the gut biome to yield higher Bilophila remains to be seen. In the future, the use of probiotics, possibly with certain antibiotics, may help a patient shift their gut bacteria to reduce their heart disease risk. This seems like more of a reality versus just eat more meat to get the higher Bilophila bacteria count.

It's important to see that certain bacteria, viruses, and fungi interact with each other. Some supporting each other, while others attacking and dominate other strains. Understanding the complex interactions of the gut biome will be a monumental scientific feat similar to coding the human genome (if not more complex).

Physical therapy implications tied to the gut biome are many. From autoimmune diseases like rheumatoid arthritis and multiple sclerosis, inflammatory conditions like heart disease, to obesity and infections, the gut biome have certain implications in health and PT practice. Again, reducing TMAO through bacteria changes is one method, but we can nearly eliminate TMAO by making certain dietary changes...So, how can we help as clinicians? It's simple:

Encourage clients to eat real, whole, plant-foods. Studies show that the human gut recognizes this food and it helps to build a stronger gut flora.
Educate your patients to eat a variety of plant foods. More variety in foods equals a greater variety in bacteria, fungi, and viruses, all which can be helpful.
Enjoy probiotic rich foods like kimchi, fermented drinks and plant-based yogurts, and miso. Probiotics themselves may be helpful, although we don't know exactly what strains are best for each client (yet).

In the end, PTs should look beyond the hype of the media, especially when it comes to hard science like microbiology and the gut biome. Simple dietary changes can make a big difference and is likely easier to implement at this time compared to complex probiotic changes and treatments. Enjoy your food!

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