THE BLOG
06/18/2015 02:25 pm ET Updated Dec 06, 2017

Friends With Benefits -- Getting to Know Your Gut Microbiome

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by guest blogger Pam Peeke, MD, MPH, FACP, best-selling author and expert on health, fitness, and nutrition

When we're hungry, we often hear familiar growling sounds emanating from deep inside our abdomen, reminding us it's time to feed our body. Experiencing these rumblings, you may stare at your tummy and wonder what's really going on in there. If you think it's just about filling an empty stomach, you're wrong. The new news is that there's so much more to your belly than just a cavity crammed with 25 feet of intestine. Further, it's what's living within the coils of your bowels and its impact on everything from your health to your weight that is positively mind-blowing.

Recently, scientists have become aware of a new and pivotal player that teams with the brain for the control of total mind-body health. It's the 100 trillion bacteria--more than 10,000 unique species--living in our intestines, referred to as the commensal microbiome. That's 10 times more microbial cells than there are human cells and 150 times the number of our 24,000 human genes.

Here's another way to look at it: Our brains weigh about three pounds. The gut microbiome weighs from three to six pounds, or up to twice the weight of our brains. Say hello to a whole host of new best friends!

Why is the gastrointestinal microbiome so special? First, it's actually now viewed as an organ system with bacterial inhabitants that have been our friends since the origin of humankind. They have co-evolved right along with us, facilitating everything from our brain development and immune function to our behavior, mood, appetite, and metabolism. These marvelous microbes can accomplish these wonders by communicating via the vagus nerve between the gut lining and the brain stem. By doing so, the gut bacteria can influence mood (80 to 90 percent of serotonin is secreted by the gut). Also, our gut bacteria control our insulin sensitivity and our satiety (through enteroendocrine cells).

To reap the benefits of our gut bacteria, our goal should be to feed them healthy foods to maintain an optimal environment in which they can thrive. Unfortunately, too many people are consuming a diet heavy in refined and processed foods, laden with manufactured sugar, fat, and salt and containing very little fiber, that our gut bacterial population is suffering. When this happens, science has shown that the resulting bacterial imbalance leaves us more vulnerable to heart disease, diabetes, cancer, and excess fat accumulation.

In addition to making certain that your bacterial pals are well fed, it's very important to avoid any kind of inflammation in the intestinal wall lining that will interfere with their ability to function. To achieve this, it's imperative you clean up your diet. Scientists found that within just 24 hours of consuming a typical low-quality diet of processed sugars and saturated fat, the gut bacterial flora shifted to a kind that favored inflammation. Obesity itself is associated with gut inflammation, which results in a "leaky" gut, leading to the release of more pro-inflammatory substances promoting high levels of inflammation throughout the body. Stick with whole foods and eliminate this problem.

How does your gut microbiota affect your weight? Scientists have found that obese people have a greater population of Firmicutes, a bacterial species that is exceptionally adept at extracting calories from food and actually can turn on genes that increase the risk for obesity and metabolic syndrome. For that matter, when gut bacterial floras from obese people are transplanted into lean mice, they become obese. Here's the good news: Weight reduction reverses this process and restores the normal bacterial balance favoring optimal and sustainable weight management.

Hopefully, with this enlightenment about your new best friends residing in your gastrointestinal ecosystem, you'll be more mindful about how to take care of them.

First, you need to feed them what they love so that they continue to grow, stay active, and keep you healthy. Nutrition experts call this bacterial fuel "prebiotics," and they typically have three characteristics:
  • They're non-digestible, which means they pass through the stomach without being broken down by enzymes or acid;
  • They must be metabolized or fermented by the gut's bacterial population;
  • Eating them results in health benefits for the human body.
For every 100 grams of high-quality carbohydrates consumed, about 30 grams of bacteria are produced. A favorite of our microbiota are fiber-rich foods, including:

1. Apples and bananas

2. Beans

3. Bran

4. Cabbage

5. Psyllium

6. Raw artichokes, garlic, onion, leeks, and asparagus

7. Root vegetables: Sweet potatoes, squash, wild yams, jicama, beets, carrots, turnips, parsnips

8. Whole grain corn and wheat

Whereas prebiotics keep your bacteria well fed, probiotics actually help to restore colonies of bacteria that may have been decreased by antibiotics or conditions that result in inflammation, such as diarrhea, constipation, colitis, or eating a typical Western diet.

These probiotics include fermented foods that contain live bacteria that, for example, can help manage our metabolisms and weight optimally. Examples include:

1. Fermented meat, fish and eggs

2. Kefir and yogurt

3. Kimchi

4. Pickled fruits and vegetables

5. Sauerkraut

6. Tempeh

Some people elect to use probiotic supplements if they have had issues with conditions that have significantly altered their bacterial flora balance. Others take a probiotic preventatively to make certain core probiotic species are well maintained. Trusted probiotic supplement varieties include Lactobacillus (plantarum, acidophilus, and brevis) and Bifidobacterium (lactis and longum).

It's always best to consult your healthcare provider regarding the use of probiotics. Clearly, a diet filled with whole foods and prebiotic foods should generally suffice to maintain a healthy and thriving bacterial population.

So, the next time you sit down to eat a meal or snack, look down at your abdomen and give it a loving pat, saying, "Time to feed my new best friends."

Pamela Peeke, MD, MPH, FACP, is a Pew Scholar in nutrition and metabolism, an assistant professor of medicine at the University of Maryland, and a fellow of the American College of Physicians. A triathlete and mountaineer, she is known as "the doc who walks the talk," living what she's learned as an expert in health, fitness, and nutrition. Her current research at the University of Maryland centers on the connection between meditation and overeating. She is the author of many best-selling books, including Fight Fat after Forty. Her newest book is the New York Times bestseller The Hunger Fix.

For more from Maria Rodale, visit www.mariasfarmcountrykitchen.com