About Drs. Justin Sonnenburg and Erica Sonnenburg
Drs. Justin Sonnenburg and Erica Sonnenburg are two top microbial scientists at Stanford University and authors of The Good Gut. In this episode, these pioneers share diet tips from their work at Stanford to help you increase the diversity of the trillions of bacterial organisms in your gut.
2:29 The Power of Microbes: Over the past decade there has been an awakening about the gut, microbiome and genetics. Microbes connect in major ways to human biology with digestion, metabolism, systemic immune function and central nervous system. There is no part of our body that is not touched, directly or indirectly, by these microbes in some way.
4:32 Microbial Digestion: Gut microbes rely upon complex carbohydrates (dietary fiber) to complete their functions in the gut. They digest our resistant complex polysaccharides that come from plant material; fruits, vegetables, legumes, and whole grains. At the same time, they release compounds into our gut that are soaked into our bloodstream that do things like help maintain our immune system balance and help us decide whether we are storing calories or burning them.
5:56 Feed Your Microbes: High fiber foods feed your microbes. The Sonnenburgs make sure that their family consumes high fiber foods at every meal.
7:30 Microbial Diversity – The Jelly Bean Analogy: Think of each species of gut bacteria as a color of jelly bean. The Western diet will be a simple mix of a few colors. Modern day hunter gatherers or those who live similarly to those at the beginning of agriculture, have many more colors of jelly beans. They have species of gut bacteria that are not seen in the Western world. In the environment, if an ecosystem loses its diversity, it’s a bad thing. Potentially, that is the case with our microbial ecosystem?
9:25 A Skewed Perspective of Microbes: Research has primarily focused on Westerners, but now research is looking into populations around the globe. The NIH Human Microbiome Project spent years working to determine what a healthy microbiota is and working to determine how the microbiome changes in different disease states.
10:20 Microbiota, a Key Player in Disease: Just because someone is healthy, doesn’t mean they have a healthy microbiota. Evidence is building that shows that most Americans have unhealthy gut microbiota, which predisposes us to many Western diseases. Metabolic syndrome, heart disaease, autoimmune diseases, cancers, and the like, are all become more prevalent. It is possible that there are individual causes for these diseases, but more likely, that there are only a few causes and that gut microbiota is central of them.
11:54 Traditional Societies: Humans have spent 95% of our time on the earth as hunter gatherers. By looking at hunter gatherer societies today, we can get a better understanding of what our gut microbiota is supposed to be.
13:39 The High MAC Diet: Microbiota Accessible Carbohydrates are dietary fiber that we consume to feed our microbiota. Tubers eaten by hunter gatherers have not been modified by agriculture, making it texturally and nutritionally different from what we eat. Since we cannot recreate the diet of hunter gatherers, we can eat lots of different foods, including tubers, along with berries and leafy greens and increase fiber to diversify and sustain our microbiota.
15:56 Polyphenols: When researching the impact of plant fiber, it is challenging for researchers to parse out the other benefits of the consumption of plants. In general, Westerners should eat more plants that contain complex dietary fibers, not only to feed their microbiota, but to garner the other benefits.
18:01 Fiber Consumption Comparison: Hunter gatherers consume about 150 – 200 grams per day of dietary fiber. In the U.S., we struggle to eat 15 grams per day. If you starve the microbes in the gut, they begin to consume the mucus lining of your digestive tract.
19:32 Short Chain Fatty Acids Created By Our Microbiota: Acetate, propionate, and butyrate are the major ones. In mice, propionate has been shown to be a regulator of metabolism. Butyrate and propionate have shown in mice to be a regulator of inflammation. They may also play a role in satiety. One day we will have enough information to match our foods to specific microbes in our gut. Most of us are deficient in short chain fatty acids. Increase dietary fiber, to increase short chain fatty acids.
24:13 Protein: We know very little about how protein impacts the gut microbiota. Excessive protein consumption can impact the gut microbiota, for example, by creating aromatic amino acids that run throughout the body via the blood. What impact this is, is unknown. Research has shown that the compound in protein called carnitine is metabolized by gut microbiota into trimethylamine, which is taken into the bloodstream and oxidized by the liver, creating the metabolite called TMAO. TMAO has been linked to increased risk for cardiovascular events.
17:02 Individualized Microbiota: Vegans do not have a lot of carnitine and when they do eat meat, there is little increase in TMAO, unlike the greater rise in TMAO in those who eat a lot of meat. It appears that the microbiota has a learning curve.
27:52 What do the Sonnenbergs eat? They eat a seasonal plant based diet with legumes and fermented foods, like yogurt and kefir. They do eat meat as part of their diverse diet, though it is not the focus.
19:02 Seasonal Eating: In our modern world there is little difference in what humans eat throughout the year, so there is little change in the microbiota. However, in primates, and in humans who do eat seasonally, there is a large change in gut microbiota throughout the year.
30:50 Shifts in Microbiota: Research has shown that within about 24 hours after consumption, a dietary shift is reflected in a microbiota shift. Changes in diversity (more jelly beans) take longer, unless you have a fecal matter transplant. Theoretically, it could take months to years to build and sustain broader diversity. Soil based microbes were consumed by our ancestors, but how it would impact us today is not clear. Bacteria from microbes from fermented foods has been shown to be beneficial, so it could be that soil is as well.
34:21 Fat: We are in the early stages of understanding the relationship between fat and the gut microbiota. A study showed that saturated fats enrich groups of bacteria in the gut that appear to be pro-inflammatory, called pathobionts. Fats can increase gut permeability. There is a complex interplay between fats and bile acids. Bile acids, which are regulated by the gut microbiota, help to digest fats. The Sonnenburgs eat cultured butter as a means to consume more microbial products. Moderation is important. If your grandmother didn’t have access to it as a kid, stay away from it.
37:16 Diet Fads: There are many ways to interpret scientific studies. Taking one study and running with it to create a new diet is dangerous. Diets should include diverse food choices, in moderation, and the knowledge that the microbiota has a great range of needs.
38:57 Promoting Diversity: Babies born by C-Section have a microbiome that is much like their mother’s skin. Babies born vaginally have a microbiota that resembles that of their mother’s vaginal canal. Breastfeeding nurtures the microbiota, providing prebiotics. Be prudent in antibiotic use in children and adults.
43:44 Handwashing: If you are at home in your yard or with your pets, handwashing does not have to be immediate. One of the benefits of pets is increased exposure to microbes to which you normally would not. Studies have shown that a child having a pet from an early age can help reduce some risk of asthma.
47:14 It’s Complicated: The gut microbiota and the human body are immensely complex. It will take decades to unravel the connections. Just because the system is complex doesn’t mean that the answer to having a healthy microbiota has to be complex.