If you pay even passing attention to science and health news, chances are you’ve seen press about the newest study on why meat is killing us. In this trial, researchers fed a group of people different diets sequentially and then sequenced their gut bacteria. First, volunteers ate a version of the Atkins diet: eggs and bacon, ribs, steak, salami, and pork rinds. Then the group was fed a standard “healthy” diet: whole grains, fruits, vegetables, and pretty much devoid of any animal products. Researchers found the different diets produced major shifts in the microbiome of the people in the study after just a couple of days. It’s proof of of the concept that our own flora are significantly influenced by our food intake.
The relationship between the food that we eat, our gut bacteria, and human health and disease is one of the most exciting areas of research going on today. And the mainstream science press is on the case. You may remember articles from earlier this year on red meat altering gut flora to increase inflammation or the hypothetically increased cardiovascular disease risk from TMAO synthesized by gut bacteria after egg ingestion. It’s fascinating to me that the headline after these studies come out always seems to be some variation on the theme that animal products are terrible for us and we need to avoid them to reduce our chances of becoming sick.
In my previous post on probiotics,* I took a look at the myriad inflammatory conditions and infections that seem to be markedly impacted by the trillions of bacteria that live within our colons. There’s a lot of compelling evidence that probiotics, either from fermented foods (like kombucha, yogurt, and sauerkraut) or supplements, have a positive impact on our health via directly altering our personal bacterial populations. But the corollary to this is that it’s not enough just to have a good balance of bacteria, they need to be fed appropriately in order to flourish.
Prebiotics are substances found in roots, tubers, and vegetables (like chickpeas) that are undigestable to humans but stimulate the growth of beneficial bacteria in the gut. The major ones in our diets are inulin and oligofructose, but there are plenty of others such as fructooligosaccharides and galactooligosaccharides. Some scientists like to make a distinction between short chain and long chain as different lengths feed bacteria in different areas of the colon (short chain feed bacteria early in the colon and long chain a bit further down). By feeding our gut bacteria prebiotics, we alter them in beneficial ways. There’s evidence that prebiotics can modify immune function and may even protect patients with inflammatory bowel disease. And some researchers suspect that one of the reasons breast milk is the perfect food for newborns is that the oligosaccharides present in it provide an excellent prebiotic source for the infant’s developing microbiome.
So if prebiotics from plant sources appear to improve our health via microbiome modulation and animal products like meat and eggs cause our gut bacteria to change and start pumping out substances that increase heart disease risk, shouldn’t we all be vegans? Maybe, but I’m not convinced on the basis of these studies. These are great first steps in the investigation of the role food plays in our microbiome and subsequently our health. They don’t tell us anything about long term disease risk, only about short term biomarkers. All I can take away at this point is that eating nothing but meat and eggs for a short period of time may chance my gut bacteria in ways that may not be good for me. I haven’t learned anything about the long term effects, and I certainly haven’t learned anything about my actual disease risk. Those studies take huge groups of participants followed over years to tell us anything definitive. But they do provide us with food for thought.
As with all diet studies, our ability to draw conclusions is confounded by multiple variables being simultaneously manipulated. How much of the changes observed in these studies is due to the presence of meat and how much of it is due to the absence of plant matter? Maybe concurrently eating prebiotics from tubers protects our microbiome from the destruction wrought by meat. Or maybe adding a probiotic would do the trick. Of course, it’s still always possible that meat actually is unhealthy and that it wreaks its damage to our body via 10 trillion helpers. As with most nutritional research, the definitive answer remains far from clear.
My takeaway is simple: your mom was probably right when she told you to eat your vegetables! I suspect that veggies, tubers, and roots are probably good for you. Don’t fall prey to the latest study** trying to convince you that what you’ve been eating is killing you. If you’re going to eat meat or eggs, it’s not a bad idea to have a side of asparagus or top if with some onions and garlic. So eat a variety of plants and feed your bacteria because they are hungry!
*Quick refresher: probiotics are live bacteria found in fermented foods like sauerkraut, kimchi, and yogurt. You can also get them in supplement form
**Or even worse, news article about the study!
-Dr. Greg Katz, 2Armadillos Snack Co.