digest
The first part of the conversation focuses on fiber and short chain fatty acids. The guest describes short chain fatty acids as possibly the most healing nutrient in nature and as one of the most anti-inflammatory molecules he has come across. The basic mechanism is that we eat fiber, the bacteria in our microbiome break that fiber down, and they produce short chain fatty acids. The story continues beyond that simple step: our immune cells and human cells have receptors that receive these short chain fatty acids and act on the information they carry. In that sense, short chain fatty acids work as a signaling molecule. The gut microbiome is effectively communicating with the body and training it, and it has the ability to switch genes on and off. It can also turn down the immune system. In the context of autoimmune conditions, the guest explains that more short chain fatty acids are needed to empower specific cells called T-regulatory cells, which turn down the immune system and protect the body.
He notes that autoimmune diseases are not exclusively the result of fiber deficiency, and that there is certainly a genetic component. However, that genetic component existed 200 or 300 years ago, when these conditions were not much of a problem. Many of these conditions did not have a name until the last 100 years, and many of them have increased by 500% in the last 50 years. Genetics clearly cannot be the full explanation, so the cause must be related to diet and lifestyle. Ultimately, diet and lifestyle come back to the microbiome, and one of the most important places to start is with fiber. The guest says that people need to start slow and low with fiber, because the microbes that respond to fiber must be built up in order to turn it into short chain fatty acids.
He compares the gut to a muscle. A muscle is capable of work but has limits, and the more it is trained, the more capable it becomes. Just as someone lifting weights progresses from 50 kilos to 55 kilos to 60 kilos over time, exposing the gut to a diverse mix of foods trains it to consume those foods more effectively. Eventually, a person may no longer need to restrict foods based on their capabilities, because those capabilities become limitless and they can eat whatever they want.
The guest explains that not all fiber is the same. Fiber is a generic word, similar to protein. No one would claim that the protein in fish is the same as the protein in beans, even though both contain protein. Fiber is unique to individual plants, and there are many different forms of it, to the point that we do not know how many exist. All plants contain fiber, and every plant has unique forms of fiber. Fiber is broadly split into two major types, soluble and insoluble. Soluble fiber dissolves in a drink and disappears, and it typically feeds the microbes; this is the prebiotic fiber. Insoluble fiber is the grit: it does not dissolve, and it remains even if the drink is boiled. Insoluble fiber is most of the time not prebiotic fiber, but it still serves a purpose. It helps with bowel transit and bowel movements, which affect gut microbes, and it also helps with cholesterol and blood fat control. Both types have advantages, and the key point is that every plant has a unique form of fiber and feeds unique families of microbes.
This leads to what the guest calls F goals, a framework he uses in his book for diets people should consider. He acknowledges that the word diet is stigmatized and can lead to disordered eating, but says he is describing the opposite of something unsustainable. He wants people to have abundance. He argues that the biggest misconception in the gut health space is that people are very quick to restrict and less quick to add back.
The F goals are a general framework for organizing his day around foods he seeks out. F stands for fruit. He believes fruit has been inappropriately villainized and is amazingly good for us; people who consume more fruit are less likely to have diabetes and also tend to lose weight. F also stands for fermented foods, which add diversity to the microbiome. G stands for greens, which have almost no calories yet provide a lot of nutrition. G also stands for grains, meaning unrefined grains such as whole grains, which are good for us, high in fiber, and contain resistant starches. O stands for omega-3 super seeds, including chia, flax, and hemp, as well as walnuts. These contain omega-3 fats, which are healthy fats that people need more of. A stands for aromatics, such as onions, garlic, and shallots, which are delicious, good for the heart, and protective against cancer. L stands for legumes, including beans, peas, and lentils. The guest describes legumes as the number one superfood, because they are gut health foods and longevity foods. Looking at the evidence for heart disease, cancer, stroke, and diabetes, he says legumes reduce the likelihood of these diseases across the board.
S stands for several things. It stands for shrooms, meaning mushrooms, which are technically fungi rather than plants but contain fiber and are incredibly good for us, so they count as honorary plants. S also stands for seaweed. Most cultures do not consume seaweed, but in Japan they do, and it is incredibly healthy. It is another source of unique plants with unique fiber. The final item is sprouts. In the book he had written sulforaphane, a cancer-fighting chemical found in broccoli sprouts, but he rephrases this to sprouts because he sees sprouts as superfoods. A sprout is what happens when you take a seed and add water, which unlocks the seed that is waiting to germinate and grow. The sprout is tremendously high in fiber and protein and also contains phytochemicals in disproportionate levels. Broccoli sprouts have 50 to 100 times more cancer-fighting chemical than adult broccoli, so a pinch of broccoli sprouts can provide as much benefit as eating a head of broccoli.
The conversation then turns to the microbiome across generations. If a parent passes on part of their microbiome to a child, the diet of earlier generations matters. The guest refers to a study by Justin Sonnenburg, a researcher at Stanford whom he admires and who wrote a blurb for his first book, Fiber Fueled. The concern is microbial loss that can occur over generations. Because humans take 30 or more years to create a new generation, the study used mice. Sonnenburg started with mice at a certain level of microbial diversity, which is a measure of microbiome health, and then observed what happened on a low-fiber diet. The mice lost diversity and transferred that loss to their offspring, who continued on a low-fiber diet and lost more diversity, passing it on in turn. When fiber was added back during the process, diversity could be partly restored, but not fully back to the starting point. Some loss had occurred as a result of choices made over generations.
The guest illustrates this with an example: if a grandmother has 1,200 species of microbes as a child but her mother has 900, and the mother then loses another 300, the child starts with only 600, half of what the grandmother had. At some point, the loss of species becomes problematic, because each species evolved for a purpose and the other microbes may not be able to step up and do the missing job. Keeping ourselves healthy is therefore also keeping our children healthy, and because we live with our children, we are creating an ecosystem of these microbes in our homes.
He also questions how generational risk is usually explained. Many studies say that if your parents had a condition, you are at risk for it too, and this has been assumed to be genetic. However, much genetic research, including work by Tim Spector, his partner at Zoe, has not proven that these patterns are genetic. He suggests that what gets transferred across generations is not only microbes but also lifestyle, and if that lifestyle is unhealthy, the problems that come with it are transferred too.