The Gut-Friendly Foods Dr. Jason Rannfeldt Tells Every Client to Add This Week

When I talk about gut health with a new executive client, their eyes usually glaze over — until I tell them the gut is upstream of almost every complaint they walked in with. The afternoon energy crash. The brain fog at 3pm. The bloating after client dinners. The immune system that seems to catch everything. The mood that is shorter than it used to be. In my coaching practice, Dr. Jason Rannfeldt sees the same pattern on repeat: high performers who have optimized their calendars, their workouts, and their inboxes, while feeding a gut microbiome that is running on restaurant meals, protein bars, and stress.

The good news is that fixing the input side is simpler than the supplement industry wants you to believe. I covered the full system in Gut Health: The Overlooked Foundation of Energy, Focus, and Immunity, and the performance consequences in The Gut-Brain Connection. This article is the practical version: the specific foods I tell every client to add this week, why they work, and the weekly targets that make it stick without turning eating into a second job.

Why food diversity beats any probiotic

The single strongest predictor of a healthy gut microbiome is not a supplement, a cleanse, or a test kit. It is the diversity of plants in your diet. Research on the American Gut Project — the largest citizen-science microbiome study ever run — found that people eating thirty or more different plant foods per week had dramatically more diverse microbiomes than people eating ten or fewer, regardless of whether either group labeled itself healthy or unhealthy.

That finding reframes the whole conversation. Your microbiome is an ecosystem, and every plant food carries a different fiber, a different polyphenol, a different fuel source for different bacterial species. Eat the same five foods on repeat — the classic executive pattern of eggs, chicken, rice, a salad, and a protein bar — and you are feeding a monoculture. Add diversity, and you are feeding an ecosystem. The downstream effects reach far beyond digestion: systemic inflammation, blood sugar stability, immune resilience, and even mental clarity all track with microbial diversity.

Food one: fermented foods, daily

If I could only add one category to a client's diet, it would be fermented foods. A landmark Stanford study compared a high-fiber diet against a high-fermented-food diet head to head, and the fermented food group won on the metric that matters most: increased microbiome diversity and decreased markers of inflammation, in just ten weeks.

The practical list: plain Greek yogurt or kefir, sauerkraut, kimchi, and miso. The details matter — the sauerkraut must be the refrigerated kind that says "live cultures," not the shelf-stable jar that has been pasteurized into uselessness. The yogurt must be plain; the flavored versions carry enough added sugar to work against you. Start with one or two servings a day: Greek yogurt at breakfast, a forkful of kimchi or kraut alongside lunch or dinner. That is it. Clients who do nothing else report less bloating and more stable energy within two to three weeks.

Food two: beans and lentils

Ask me for the most underused performance food in the executive diet and I will say legumes without hesitation. Beans and lentils deliver fermentable fiber — the exact substrate your beneficial bacteria convert into short-chain fatty acids like butyrate, which fuels the gut lining itself, regulates inflammation, and communicates with the brain through the gut-brain axis I wrote about in this article.

They also solve a problem most executives have without knowing it: blood sugar volatility. The fiber and resistant starch in legumes flatten the glucose curve of the entire meal, which is the same mechanism behind the afternoon-crash fix in Blood Sugar and Executive Focus. The target is a half-cup to a cup most days — lentils in a soup, chickpeas on a salad, black beans alongside eggs. If you have avoided beans because of digestive complaints, that is usually a sign of a gut that has lost the capacity to ferment fiber, and the fix is to start small and build, not to avoid them forever.

Food three: thirty plants a week

This is the game I give every client, because it turns gut health from a restriction diet into a points system. Count every different plant food you eat in a week — vegetables, fruits, whole grains, legumes, nuts, seeds, herbs, and spices all count individually — and aim for thirty. Garlic counts. The rosemary on your steak counts. Coffee and dark chocolate count, since both are plant foods rich in polyphenols.

Most executives score between eight and twelve in their first week. Thirty sounds impossible until you realize a single salad with mixed greens, tomatoes, peppers, onions, seeds, and olive oil is already six or seven. The scoring trick works because it changes behavior at the grocery store instead of relying on willpower at the table — you start buying variety because you are collecting points. And variety is the entire mechanism. This is the same systems-over-willpower principle behind why most health programs fail high achievers: build an environment that scores points by default.

Food four: the polyphenol powerhouses

Polyphenols are plant compounds that your gut bacteria metabolize into signaling molecules with real effects on inflammation, vascular function, and cognition. The densest sources are the colorful and bitter ones: berries, dark leafy greens, extra-virgin olive oil, green tea, dark chocolate at 85 percent or higher, and deeply colored vegetables like red cabbage and beets.

The executive translation: berries on your yogurt every morning, olive oil as your default fat, a square or two of real dark chocolate after dinner, and greens at both lunch and dinner. None of this requires a recipe. It requires a shopping list. I think of polyphenols as one of the quiet levers behind the longevity strategies that compound over decades — unglamorous, cheap, and relentlessly effective.

Food five: protein sources that feed the gut, not just the muscle

Protein gets covered exhaustively in the fitness world, and I have my own framework for targets in Protein and Muscle Longevity. What gets missed is that your protein choices also shape your microbiome. Fatty fish like salmon and sardines bring omega-3s that reduce gut inflammation. Fermented dairy brings live cultures alongside its protein. Even your red meat choice matters — paired with abundant fiber, an occasional steak is fine; paired with nothing but fries, it feeds bacterial pathways linked to inflammatory metabolites.

The rule I give clients: never eat protein alone. Every protein anchor gets a fiber partner — the salmon with lentils, the eggs with black beans and salsa, the chicken over a pile of vegetables. This one habit quietly solves half the problems people try to fix with supplements, and it costs nothing extra.

What to pull back on while you add

Adding the right foods does most of the work, but two subtractions accelerate it. First, ultra-processed foods — the packaged, shelf-stable, ingredient-list-longer-than-a-paragraph category that dominates airport and office eating. Emulsifiers and additives common in these foods are directly disruptive to the gut lining and microbiome. Second, artificial sweeteners in daily heavy doses, which several studies suggest alter gut bacteria in ways that worsen glucose tolerance — the opposite of the intended effect.

Alcohol deserves its own mention, because it is the executive gut stressor nobody wants to discuss. Even moderate intake increases intestinal permeability and shifts the microbiome in the wrong direction. The honest math — including the sleep and recovery cost — is in Alcohol and Executive Performance. You do not have to be perfect; you do have to be honest about the dose.

The seven-day starter plan

Here is exactly how I onboard a client into this, because sequencing beats intensity:

Days one and two: Add plain Greek yogurt with berries at breakfast. Buy refrigerated sauerkraut or kimchi and add a forkful to one meal. Nothing else changes.

Days three and four: Add one serving of beans or lentils daily — a side, a soup, or thrown into a salad. Start counting your weekly plants on a note in your phone.

Days five through seven: Shop for diversity. Fifteen new plants in the cart, olive oil as the default fat, dark chocolate for the evening. Hit twenty plants by the end of week one and thirty by week three.

That is the entire protocol. No elimination phase, no testing, no powders. Clients are consistently surprised that the bloating they attributed to getting older, the 3pm fog they blamed on workload, and the catch-everything immune system all start improving within a month — the same compounding effect I describe in Rebuilding Health After Burnout. And because these changes feed the gut-brain axis, the mood and focus benefits often arrive before the digestive ones, which I explore from the leadership-performance angle over at jasonleerannfeldt.me.

The bottom line

Gut health is not a cleanse and it is not a supplement stack. It is a weekly pattern: fermented foods daily, beans and lentils most days, thirty different plants a week, polyphenol-rich foods at every meal, and protein that never travels without fiber. Five additions, none expensive, none complicated, all compounding. Do it for four weeks and let your own energy, digestion, and recovery metrics make the case.

If you want this built into a complete system around your labs, schedule, and goals, that is the work inside Crush 90 and Thrive 90. Start with a short conversation on the contact page, or read more about the approach on the about page.