What Women Need to Know About the Gut Microbiome

Digestion is just the beginning of what this “virtual organ” does for your health, performance, and well being.

What you eat is essential for health and performance. But what you put in your mouth is only part of the equation. What is happening in your gut, is just as, if not sometimes more important. In fact, the more we learn about the gut microbiome, the more clear it becomes that the gut microbiome is one of the most important—and overlooked—organs in athletic performance.

And yep, I just called it an organ, as did the British Medical Journal (BMJ) in a 2018 article that described the gut microbiome as “a virtual organ of the body.” That’s because the gut microbiome, which includes approximately 100 trillion micro-organisms living in the human gastrointestinal tract, encodes over three million genes and influences your fitness, phenotype, and health.

In fact, the specific bacteria that live in your gut influence pretty much everything in your body, including your moods (there are connections between gut health and anxiety and depression), cravings, metabolism, immunity, fat storage, and so much more that we probably don’t even know about yet. (That last part is important: new studies are coming out by the day. I’m just presenting a snapshot of our best understanding at this moment in time.)

Digestion and Beyond

Beginning with the basics, your gut takes the food you eat and breaks it down so it can be absorbed into your bloodstream and sent out to your organs and muscles. A rich array of active bacteria and healthy flora is needed to fully break it all down so you can get the most nutrition out of every morsel you eat.

The byproducts of some digestive processes, especially the fermentation of indigestible fibers, also creates the production of short chain fatty acids (SCFAs) that help protect against inflammation, help retain your skeletal muscle mass, and perform other vital metabolic functions like reducing insulin resistance.

But digestion is just the beginning. A healthy, diverse gut microbiome is also essential for immunity, as healthy intestinal microorganisms can help keep inflammation in check and keep the immune system in balance. It also helps us synthesize various vitamins, like the B vitamins and vitamin K, as well as some amino acids.  

Your gut microbiota also play a key role in regulating your hormones like estrogen, thyroid stimulating hormone (TSH), serotonin, and stress hormones. It’s so instrumental in managing sex hormones that recent research has suggested the concept of a “microgenderome” to indicate the interplay between the gut microbiome and sex hormones.

Take estrogen as an example. Once it’s produced, it enters the bloodstream and makes its way to the liver (all blood circulates through the liver), where it is metabolized into inactive forms that are then sent off via bile into the intestine for elimination, where your gut bacteria come in. There is a collection of gut microbes called the estrobolome that can modulate the metabolism of estrogen (as well as other sex hormones) in your intestine through an enzyme they create called beta-glucuronidase, which can convert the inactive estrogen back into active forms. So, some of the estrogen that was shipped to your bowels for removal can be reactivated and sent back into circulation.

That’s important because an imbalance of the estrobolome can lead to either an excess or deficit of beta-glucuronidase, which in turn can disrupt your hormone balance. Conditions like PCOS (polycystic ovary syndrome) and endometriosis are linked to dysbiosis of the estrobolome in premenopausal women. There is also a huge shift in gut microbiome diversity in our late perimenopausal and early postmenopausal years that are associated with body composition changes and increased risk for metabolic disease. The reduction of our sex hormones decreases the diversity in our microbiome. But if we focus on maintaining that diversity, it can help with maintaining a healthier balance in our sex hormone circulation.

Creating a Healthy Gut Microbiome Balance

These gut bacteria serve us, but importantly, they also serve themselves. Diversity is good for us, but unless we foster it, they’ll battle each other and can create imbalances that are to our detriment.

For example, on a very basic level, your gut microbiota consists mostly of two dominant bacterial divisions: Firmicutes and Bacteroidetes. These bacteria affect our weight because they regulate how much energy we absorb. Firmicutes absorb more (you’re getting more calories from food); Bacteroidetes absorb less.

Firmicutes dominant gut biomes are associated with increases in inflammation, which can lead to weight gain and chronic diseases. Having a balanced, healthy gut microbiome is key for inflammation and metabolism management.

Performance wise, research shows that a healthy gut biome can boost your metabolism, energy availability during exercise, and recovery after a workout. In fact, a study published in Advances in Nutrition calls for more research on manipulating diet, exercise, and gut microbiome so coaches and sports dietitians can provide recommendations for athletes on how to “fuel their microbes.”

While more research is needed in this burgeoning field, there are steps you can take right now to build a healthy, robust gut microbiome. Here’s what to consider:

Balance Your Macronutrients: Athletes need up to twice as much protein as their sedentary peers. But that doesn’t mean you should be eating a “high protein” diet at the expense of carbohydrates, which can be detrimental to your gut microbiome long term. Your gut needs a mix of macronutrients, including varied protein sources, nutrient and fiber dense carbohydrates, and healthy fats, especially omega three fatty acids, which research suggests have a positive impact on the gut microbiome.

Strive for at least 25: Fiber is queen for gut health. It’s what feeds those essential microbes. Aim for at least 25, preferably closer to 30 grams a day, from a wide variety of foods, especially if you’re in and beyond the menopause transition. Research suggests that athletes should definitely be aiming for that higher number. A 2021 study titled Fueling Gut Microbes recommends that athletes strive for 14 grams of fiber per every 1,000 calories they eat, which would mean at least 28 grams for active women on most days. Obviously, you want to time that fiber intake appropriately. Since it slows digestion, you’ll want to avoid high-fiber carbs before exercise, especially running.

Pile on the plants: A diet grounded in plants is good for your gut. A landmark international study published in the January 2021 edition of Nature Medicine reported that diets rich in plant-based foods promoted a gut microbiome that was linked to a lower risk of common chronic illnesses like diabetes and heart disease. 

Consume probiotic and prebiotic foods: Probiotic foods are those that naturally contain healthy bacteria to help populate your gut microbiome. Prebiotic foods are those that have a fiber that feeds the beneficial bacteria. It’s important to eat both.

One of the best sources of probiotics is fermented foods. Plain (i.e. not loaded with sugar) yogurt that contains live cultures is a great source. Other excellent probiotic foods for gut health are kefir, miso, kimchi and sauerkraut. (Though kombucha is popular, it doesn’t make the cut here. Though it’s a fermented beverage, the microbes in kombucha haven’t been confirmed to be probiotic.)

Common prebiotic-rich foods include barely ripe bananas, asparagus, apples, onions, garlic, leeks, oatmeal, legumes, dandelion greens, apples, chicory root, and Jerusalem artichokes. (It’s a bizarre assortment, but something for everyone.)

Go easy on ultra-processed foods: You already know this, but it bears repeating. Refined sugary foods promote Firmicutes in the gut. When those take over, inflammation and weight gain seem to follow. Processed foods that contain artificial sweeteners and sugar substitutes are not necessarily better! A study in the BMJ reports that sucralose, aspartame, and saccharin have been shown to disrupt the balance and diversity of gut microbiota.

Skip the NSAIDs: Nonsteroidal anti-inflammatory drugs (NSAIDs) can directly impact the composition and function of the gut microbiota, and can lead to dysbiosis, or an imbalance of microorganisms in our microbiome. They also can lead to erosion of the protective mucosal barrier of the gut, which in turn leads to a condition called “leaky gut,” where the gut wall becomes too permeable, allowing toxins to spill from your gut into your bloodstream, which is as unhealthy as it sounds. Use them only as necessary.

Use antibiotics judiciously. It’s right there in the name—antibiotic. There’s no doubt that these drugs are an essential part of our modern medical arsenal and have improved and extended lives worldwide. They are also being horribly abused and overused. The Centers for Disease Control and Prevention (CDC) estimates that about half of all antibiotics prescribed are unnecessary, since many illnesses are actually viral and therefore will not respond to antibiotics. If you have a cold, sore throat, or other upper respiratory infection, chicken soup (with plenty of garlic) and rest is the way to go. Spare your gut flora the decimation caused by antibiotics.