Ask the Dr.

The microbiome-metabolism connection.
A healthy metabolism stays that way if you keep your gut bacteria happy, and feed them the stuff they thrive on—and they love variety.  Photo: Elijah Hail

By Dr. Frank Lipman

As my regular readers know, one of the hottest topics in medical research these days is the gut microbiome, the community of some 100 trillion bacteria that live mostly in the large intestine. I’ve written frequently about how to treat the gut microbiome, and how the microbiome affects our immune defenses as well as our brain function.

Now, the research is beginning to get a handle on how our gut bugs affect our metabolism. It only stands to reason: The gut is where the carbs and the fat we eat gets broken down into the fatty acids and glucose we burn for metabolic energy. How well it does that job—whether we’re running a lean, clean machine or whether high blood sugar and insulin levels are tipping us in the direction of prediabetes or diabetes—determines our overall health in a major way. And, no surprise, the microbiome plays a significant, and increasingly appreciated, role in helping to determine whether your gut is keeping you on the right metabolic track or not. Not sure what that means for your particular situation? Here’s the skinny on the microbiome-metabolism connection—and how to make it work for you:

Good “bugs,” good metabolism.

How do we know that the microbiome is bound up with metabolic health? One study found that the gut microbiomes of people who are significantly overweight look different than the microbiomes of those who are not. The lean group had more different types of bacteria inside them and, not surprisingly, a healthier metabolism, versus the heavier group, who showed insulin resistance—the precursor to worse metabolic problems down the road—as well as a propensity to continue gaining more weight. Another study looked at diabetics versus nondiabetics, and sure enough, in the diabetics, there were fewer of the “good” bacteria and more of the “bad.” We’re not positive about the cause and effect here—are the “bad” bugs promoting the extra pounds and the unhealthy metabolism, or does it work the other way as well? But researchers are teasing out a number of ways that the bacteria are directly acting on our metabolic health, depending on the lifestyle choices we make.

Insulin isn’t the only (hormone) game in town.

By now, most of you are familiar with the hormone insulin. Too much sugar in the blood requires too much insulin to clear it, which sends you down a bad metabolic path. But another hormone is just as important: glucagon-like peptide-1, or GLP-1, which cues the pancreas to release the insulin in the first place. People who struggle with diabetes and obesity also have problems getting their GLP-1 to work the way it’s supposed to. And researchers have discovered that we consume a diet that’s high in fiber—in other words, when we feed the “good bugs” in our gut the food they need to be fed—they produce organic compounds that stimulate the production of GLP-1, making the metabolic machinery run more smoothly.

Protect that gut!

Those same organic compounds (short-chain fatty acids, if you want to get technical) produced by the well-fed microbiome do double duty. Not only do they sharpen insulin response, but they also fortify the lining of the gut, closing any gaps and making it harder for microscopic food particles or nasty bacteria to escape into the bloodstream. If that happens, you’ve got a “leaky gut,” and the systemic inflammation that comes with it. And inflammation is one of the major drivers of insulin resistance. In fact, there are many folks who consider Type 2 diabetes an inflammatory disease. So, if you want to help keep your metabolism on track, taking steps now to heal your gut is an essential step.

Eating for your “bugs,” and your metabolism.

Topping the hit list are foods high in prebiotic fiber that the gut bacteria in the large intestine go to town on, fermenting it and producing the compounds that keep the metabolism, and the rest of us, in good working order. Non-starchy vegetables of any description are a good bet, like members of the brassica family (don’t forget to eat your broccoli stems) and veggies high in the compound inulin (garlic, leeks, onions, asparagus, artichokes, etc.), which the microbiome positively feasts on. One caveat here. Some of my patients and readers have sensitive guts—their microbiomes are pretty severely disordered or dysbiotic—and they will need to go slowly, or even avoid, some fast-fermenting foods, like the ones high in insulin, which can cause gut distress. Another good source of prebiotic fiber: foods high in polyphenol compounds like berries, green tea, flaxseed, and most herbs and spices.

Don’t bore your bugs.

A healthy metabolism stays that way if you keep your gut bacteria happy, and feed them the stuff they thrive on—and they love variety. The more varied foods they get to break down, the more microbial diversity your gut gains, and the better your metabolism behaves. In other words, everybody wins! Among the must-dos to keep your microbiome and metabolism on an even keel:

1. DO eat clean, organic produce and healthy animals—always avoiding conventionally grown in order to sidestep dangerous pesticides and antibiotics. Organic and/or farmers market products tend to be raised with more small-batch TLC (though they may use some natural pesticides)—and without the antibiotic pesticide Roundup.

2. DO eat more fermented foods—sauerkraut, kefir (fermented milk), kimchi (Korean fermented vegetables), or other fermented vegetables. Fermented foods help repopulate your gut with beneficial bacteria.

3. DO eat prebiotic foods—as in foods that contain the fiber on which friendly bacteria feed. Key prebiotics include tomatoes, garlic, onions, radishes, asparagus and Jerusalem artichokes. Always remember to eat the stalks and stems, as that’s where a lot of the fiber is.

4. DO go deep on fiber—with every meal, and, in particular, add more resistant starch like the kind you find in nuts, seeds and legumes that “resist” being broken down to glucose and feed the bacteria in your gut the stuff they thrive on.

To help keep your metabolic engine humming and well supported, I also recommend daily probiotics, whether in the form of fermented foods like sauerkraut or tempeh or a supplement—or better yet, both! When ingested in either form, be it pill or food, they enter your system with their own bacteria that interact with your resident gut population in health-enhancing ways, so make sure probiotics are part of your mix. The problem is everyone’s microbiome is very different. Therefore, when buying a probiotic supplement, look for probiotic capsules or powders with the two most common and effective beneficial bacteria, Lactobacillus and Bifidobacteria. The daily dose for both should be at least 20 billion CFUs for everyday use; rotate brands every couple of months to ensure you get many different and diverse strains.

How not to eat for your microbiome?

The more you eat the right foods, the better your gut microbiome can protect your metabolic health. Eat the wrong foods though (sugar, processed foods and any low-fiber, high-carb junk) and things start to move in the wrong direction pretty quickly. Not only are you dumping more sugar into your bloodstream, but after you’ve starved your good bacteria and spoon-fed the bad ones, your microbiome is progressively less able to deal with the metabolic fallout.

Don’t stress your metabolism, or your microbiome.

Being chronically stressed and/or underslept is bad news for your metabolism and your microbiome. Having regularly elevated levels of your primary stress hormone, cortisol, promotes insulin resistance directly and it can alter the environment inside your gut, making it less hospitable for your metabolic bacterial allies and cozier for the problematic ones, as well as for toxic levels of yeast and fungi. To further support your allies, focus on your sleep hygiene and find healthy ways to unwind, be it with meditation, time in nature or a pre-bedtime hot bath.

Avoid the micro-menaces.

Prescription drugs, and even over-the-counter drugs like antacids, can do a number on the gut microbiome. But the worst offenders are antibiotics, so I counsel my patients to use them only when absolutely necessary, and certainly not for every cold or sniffle. Antibiotics indiscriminately kill off the bacteria in your system and the bad bugs have a way of growing back faster. If you are taking, or have recently finished, a course of antibiotics, be sure to take the probiotic at a different time of day than when you take the antibiotic, and make sure you include the strain Saccharomyces boulardii.

Bottom line: A healthy microbiome is great for your metabolism, so treat it well!