Labs around the world are working on the microbiome’s link to specific diseases of interest, such as Alzheimer’s disease, autism, irritable bowel disease, heart disease and so forth. “The overarching theme that I think all of the data is going to point to is, in general, our drop in diversity in microbes. Just like in any ecosystem that loses diversity, the less diverse our microbiome, the more susceptible to disease we may be. But these are early days,” Leach says.

Five to 10 years from now, Leach predicts public health experts are going to be advising us to improve the diversity of microbes in our body by improving the quantity and diversity of fiber we consume, as well as to get outside and expose ourselves to the microbial world around us.

Leach also predicts we’ll see more specialized probiotics, perhaps made with hundreds of strains of bacteria.

In the future, analysis of a person’s microbiome also could help predict which medications a person may need to avoid, Morris says. Bacterial action on certain drugs, such as antidepressants, could cause them to be reabsorbed rather than excreted, potentially causing serious side effects.

What you can do now

For years we’ve been told to consume probiotics, such as in yogurt, kefir, sauerkraut and other fermented foods, which can directly supply beneficial bacteria. However, there also are many plant-based foods you can eat to encourage the growth of a healthy microbiome. Such foods may be called prebiotics. “When you modify your diet, changes in your microbiome happen very quickly—within a few days,” Kellman says.

Leach advises us to keep track of all the different kinds of plant foods we eat in a week, and aim for 25 to 35 species. “That’s probably going to do more for you than a gym membership,” Leach says.

A large number of different plant foods are as close as your local grocery store. “There are anywhere from 50 to 300 different species of plants in the produce section of stores,” Leach says.  “Unfortunately, the average American eats less than five species of plants a week.” 

If you can, shop at a farmer’s market or grow some of your own produce (ideally, organic), too. The soil that clings to garden-fresh food is teeming with beneficial microbes, unlike the sterile canned and packaged food sold in stores. Rinse, rather than rigorously scrub, produce to retain some of these beneficial soil-based organisms.

Exercising on a regular basis, sleeping at least seven hours a night and spending time outdoors in nature also promote a more diverse microbiome, Leach says.

Ultimately, in order to take care of your microbiome, you have to take care of the planet. “We need to take care of the ocean, the lakes, the soil and the atmosphere because they’re all interconnected,” Morris says. “Soil needs to be healthy in order for your food to be healthy. That circle goes on and on.”

Feeding your microbiome

The following are top foods Kellman and others recommend to nourish your microbiome through their rich supply of fiber and resistant starch. But don’t limit yourself to this list. It appears to be best to eat a wide range of different plant foods. Branch out beyond your familiar favorites.

  • Asparagus
  • Bananas (slightly green)*
  • Bell peppers
  • Berries
  • Broccoli
  • Brown rice (cooked, then chilled)*
  • Brussels sprouts
  • Cauliflower
  • Chickpeas
  • Garlic
  • Jerusalem artichoke
  • Jicama
  • Kiwi
  • Leeks
  • Lentils
  • Onions
  • Pears
  • Potatoes (cooked, then chilled)*
  • Radishes
  • Spinach
  • Tomatoes
  • Turmeric

*To increase resistant starch content.

The pH test for poo

As bacteria ferment dietary fiber and produce short chain fatty acids, your colon (large intestine) becomes more acidic and less hospitable to pathogens—so the more acidic your stool, the better, Leach says.

To measure your stool acidity, buy pH test strips at your local pharmacy and stick a test strip in your poo on toilet tissue. If your stool is consistently an 8 or 9 on the pH scale, for example, you’re likely not eating enough plant foods, but if it’s in the range of 2 to 5 (the lower the number, the more acidic), you’re likely doing a better job of getting a greater amount and variety of plants in your diet.

Using this method, you can track the effects of different dietary changes and watch your pH change over a few days’ time as you modify what you eat.