We've all heard that a high-fiber diet is good for health because it keeps the digestive system moving. As it turns out, fiber also plays a more important role than we suspected. To understand why, we need to take a look at the gut microbiome — the community of microorganisms that live in the digestive tract.
Trillions of bacteria live in the human gut — they account for ten times more cells than in the human body — and they play vital roles in our metabolism and health. It's a mutually beneficial relationship; the bacteria happily feed on dietary fiber while they perform a variety of duties, including helping to make vitamins B and K, repressing growth of harmful microorganisms, and breaking down and fermenting dietary fiber. This breakdown of fiber results in a release of beneficial, anti-inflammatory short chain fatty acids that are a vital energy source for our bodies.
In recent research, the firmicutes and bacteroidetes classes of gut bacteria have received a lot of attention. Multiple studies show that obese people have a higher concentration of firmicutes than bacteroidetes, while in lean people the bacteroidetes predominate (to help keep it straight, think of fermicutes as "fat" and bacteroidetes as "bony"). Moreover, when the diet is high in fat, the obesity-friendly firmicutes increase (the exception being a ketogenic diet), yet a high-fiber diet helps bacteroidetes increase. In addition, researchers observed that overgrowth of firmicutes led to chronic systemic inflammation, which is known to contribute to common health problems such as metabolic syndrome, diabetes and heart disease. The message: Though they both have jobs to do, you want your bacteroidetes to be stronger than your firmicutes.
Feeding The Magnificent Microbes
One might wish to rid the body of the firmicutes microbes, yet this can actually open the pathway to overgrowth of candida albicans, or a yeast infection, which leads to problems of its own. Instead, supporting a healthy population of bacteroidetes is the key, and this is done by supplying ample prebiotics in the diet. Prebiotics are non-digestible carbohydrates — in the form of dietary fiber — that serve as food for the bacteria in your gut.
To keep a healthy balance of bacteria in the gut, an ample supply of fiber-rich plant foods is necessary. These foods should be part of a diet that includes plenty of good fats, vitamins and micronutrients, and avoids bad fats, excess refined sugars, processed/junk foods, and excess alcohol. Good forms of dietary fiber include: All vegetables but especially artichokes, peas, broccoli, and Brussels sprouts; fruits; and beans. Your mother was right, even if she didn't know the whole truth: Veggies are good for you!
In addition to a diet strong in prebiotic fiber, you can help support a healthy gut environment by using supplemental probiotics: Live, “friendly" bacteria that bolster your gut’s population of healthy microbes. For probiotics to work, there must be a sufficient number of live bacteria present in the product (read your labels!) to survive the acidic environment of the stomach, and reach the large intestine. Your dietary fiber (prebiotics) acts as food to nourish these friendly probiotic bacteria, and ensures their growth and colonization. This combination of pre- and probiotic support can be vital for insuring a healthy gut.
Fermented foods such as sauerkraut, kimchee, kombucha, and yogurt contain live microbes, and can also help boost the probiotic content of your digestive tract. One caution; not all fermented foods have live cultures, and it's the live ones you want. Again, read your labels!
Medications, hygiene, age, health status, and stress can also influence your gut microbe balance. Eating a fiber-strong, gut-friendly diet and supplementing with probiotics and fermented foods is one of your best strategies for supporting gut health.