We've all heard a lot about "gut health" and the importance of maintaining a healthy microbiome (aka the bacteria and environment in your intestines), but what does that even mean, why is it important, and what on earth can you do about changing or feeding the tiny bacteria that live inside your body? It turns out that it means a lot, and you can do everything to shift your gut health to support your efforts to lose weight, boost immunity, fight bloat and even raise your mood, just by choosing the foods you eat, studies say.

There are two main functions that go on in your gut, which are your large and small intestines and colon: Metabolizing food for energy and releasing nutrients into the body–or clearing toxins out of it. So it stands to reason that the more healthy whole, natural plant-based foods you eat, the more you are feeding your gut bacteria–the trillions of little micro-organisms in your gut–healthy food that keeps the "good" bacteria fed, and your body able to absorb healthy nutrients.  But when you eat sugary or fat-filled chemical-containing junk food, red meat, or fatty dairy then your so-called unhealthy bacteria grow and have to work harder to clear the toxins out, which leads to bloating, weight gain, coronary heart disease, and a general lack of focus or mental health that comes with sluggish digestion.

To have a healthy gut–and in turn, a healthy body, able to shed pounds and have energy, focus, a healthy immune system, and a positive mood–you need to feed the healthy bacteria with prebiotics which are essentially fiber foods that help your positive bacteria grow, explains Dr. Anthony Thomas, a Ph.D. in Nutritional Biology, Director of Scientific Affairs at Jarrow Formulas in Los Angeles and an expert in the world of pro and prebiotics.

Studies have shown that probiotics, the microorganisms that mimick the healthy bacteria in the gut, are only able to grow and multiply if you feed them prebiotics, which are high fiber foods and those that contain flavonoids, found in fruits and vegetables. It's not easy to get enough of either without supplementing, but you can try if you are willing to change the way you eat. Studies have shown that gut health is directly related to disease and inflammation, weight gain, and mood. To allow your body to do its job and fight inflammation and metabolize nutrients and lose weight, you need to alter your gut microbiome, and that means eating more plant-based foods.

"Plant-based eating is one of the key determinates in good gut health," he says, and feeding these microbes is essential to your overall health. We have 10 times more microbes in our body -- and most of them in our gut --  than we have human cells. There are about 100 trillion microbes living in your gut, and as you move down the intestinal tract you have an increasing amount of microbiota, which when considered together, is practically a different organ. Their collective genetic material is referred to as the microbiome and there are about 100 times as much DNA in them as in our own bodies ... So they provide us with lots of different benefits. They digest food, alter our genetic function and they are a barrier to the body. The gastrointestinal tract is not an organ, as most people think, but a barrier to the internal body. There are plenty of microbes in there that we don't want in the body."

Dr. Thomas explains that the gut helps drive your immune system as the microbes can interact with immune cells that are present in our gastrointestinal tract. They have receptors that react with microbes and produce compounds that can signal to the human body to ramp up an immune response when necessary. The same is true of mood, since serotonin and other brain chemicals react directly to your gut health, and inflammation, bloating, weight control, and heart health are all triggered by what you eat and how your microbiome responds.

Prebiotics Are as Important as Probiotics in Maintaining Gut Health and General Health

The reason people talk about both prebiotics and probiotics is that the prebiotics essentially feeds the microbiome. Probiotics introduce the good bacteria to the gut, but unless you feed these organisms fiber, they don't get to do their jobs, Dr. Thomas explains. "Most Americans are eating less than one serving of vegetables a day, or maybe one piece of fruit a day, and they are not getting vitamins A, B, C, E, and K which all help your body function properly. By not getting enough fiber from fruits and vegetables, legumes, and nuts, you lose the benefit of taking probiotics."

While not all fiber is prebiotic, all prebiotic is fiber, since that is the fuel your healthy gut bacteria feed off of.  "The biggest thing I see is that people are not getting enough vegetable-based foods into their diet. And of course, vegans and vegetarians do better but even they may not be getting the right foods."

Here Are the Top Foods to Eat for Gut Health and Overall Health Benefits

1. Eat and drink Fermented Foods or Liquid.

Fermentation allows foods you eat and drink to deliver microorganisms or probiotics that can help your gut lining improve and fight the weakened lining that comes from too much fat and sugar in your diet. While scientists disagree with how much is needed to be effective, the fermentation process has been shown in studies to help the metabolism of sugars and to lower inflammation.  Fermented foods such as kombucha or pickles deliver probiotics (good organisms) to help build up the gut's beneficial bacteria that help your gut be healthier, Dr. Thomas says. They can reproduce in our intestinal tract and help us be healthier overall.

2. Cover 3/4 of Your Plate with Plant-Based Foods and Minimize Animal Products.

Avoiding red meat and changing the ratio of the plant-based foods on our plate is probably the number one thing that data shows will improve gut health, Dr. Thomas says. "I don't think that it's easy to eat enough plant-based foods if you're also eating animal products, to counteract that. But if you incorporate more plant-based foods you can try. If I look at a plate, 3/4 of that plate should be covered with plant-based foods, to get enough prebiotics for gut health. But when going to restaurants that is not what you see. It's also important to get a diversity of plants as we are eating. This will also dictate the microbes in the gut. When you shift your diet you shift your gut microbiome."

3. Choose a Diversity of Plant-Based Foods, to Avoid Disease and Depression.

When you hear the words bio-diversity and think about the species of the rainforest you're on track since, in most tropical or equatorial regions, the diversity of fruits and vegetables offers up a healthy array of choices. By contrast, just 14 percent of American adults consume two or more servings of fruit and vegetables daily and they tend to eat the same half-dozen vegetables over and over again.

"Americans suffer from inflammation, diabetes, depression, even mental disorders, all because their microbiome is unhealthy. Underrepresentation of fruits and vegetables is associated with these health issues. Inflammation is an important component of every chronic disease we see," Dr. Thomas says. "When they talk about the diversity of microbes in lean and healthy populations it certainly appears there is more diversity in the foods they eat. Certainly, there is scientific evidence that if we improve the diversity of foods, we can improve the situation." He argues that Americans should try to eat more and varied fruits and vegetables daily and consider taking supplements if they fall short of 5 to 9 servings daily.

4. Eat High Fiber Fruits, Vegetables, Grains, Nuts, and Seeds Throughout the Day.

"Most people are not adhering to those recommendations [to eat at least 5 and optimally 9 servings of fruits and vegetables a day]. You can pound them over the head by telling them to eat more broccoli but they won't do it," Dr. Thomas says. Data shows that a diet high in fiber and flavonoids (a phytochemical found in most fruits and vegetables) will provide protective benefits for gut health.

The goal is to try to eat as much fiber as you can and get at least 30 grams a day, from vegetables, whole foods, grains and nuts, and seeds.  To incorporate more dietary fiber with whole foods, add these to your daily lineup of meals, snacks, and smoothies:

The Top 20 Foods with Fiber and Flavanoids to Eat for Gut Health Are:

  • Bananas
  • Spinach, Kale, and Leafy Greens
  • Raspberries
  • Artichokes
  • Green Peas
  • Broccoli
  • Chickpeas
  • Lentils
  • Beans (kidney, pinto, and white)
  • Whole grains
  • Chia Seeds
  • Flax Seeds
  • Garlic and Onions
  • Apples
  • Black or Green Tea
  • Purple and Red Grapes
  • Blueberries
  • Strawberries
  • Oranges
  • Cocoa and Dark Chocolate

And if it's not clear yet, the worst foods for your gut health and overall wellbeing are refined foods with added sugar, specially packaged or junk food, sodas, and chemical preservatives.