In 2015, I wrote a piece for Harvard Health titled “Nutritional Psychiatry: Your Brain on Food”that introduced many readers to a then-emerging field: the science connecting what we eat to how our brains function and how we feel. A decade later, that piece continues to circulate — cited in academic papers, republished across health platforms, referenced in clinical conversations. The research has only deepened since then. Where I have been paying close attention is how that science applies to leaders, executives, and anyone carrying sustained cognitive and emotional load — because in my clinical experience, what and how you eat affects how you perform and therefore, how you lead.
We spend a great deal of time talking about the psychological and behavioral dimensions of leadership: emotional intelligence, executive presence, stress management, resilience, communication, self-awareness, and the ability to remain adaptive under pressure—which allmatter. What also matters is whether the biology underneath all of it can support those efforts.
The brain does not operate independently from the rest of the body. It is in constant communication with the gut, immune system, hormones, and inflammatory pathways — and the quality of that communication is shaped, in no small part, by what and how a person eats. When that biological terrain is compromised, even the best psychological tools have less to work with.
The Gut-Brain Connection
Have you ever had a “gut feeling” something was off or, alternatively, felt deeply certain that something was right? That feeling is not metaphorical. The gut and brain are in direct, continuous communication through a network known as the gut-brain axis — a bidirectional highway of neural, hormonal, and immune signals moving constantly between them. The primary physical pathway is the vagus nerve, which connects the brainstem to the digestive tract and carries information in both directions. Research has shown that roughly 80 to 90 percent of that signaling travels from the gut up to the brain, not the other way around.
In other words, the gut is informing the brain constantly. The gut is one of the body’s primary sensing systems, continually signaling information related to safety, threat, nourishment, inflammation, and internal balance. As such, the food you eat, and the microbial community that processes it, shape the quality of those signals.
The gut houses what is often referred to as the body’s “second brain,” a nervous system network made up of approximately 500 million neurons lining the gastrointestinal tract. About 95 percent of the body’s serotonin — the neurotransmitter most associated with mood regulation, emotional stability, and a sense of wellbeing — is produced there, not in the brain. The health of those neurons, and their ability to produce and regulate serotonin, depends heavily on the trillions of microorganisms that make up the gut microbiome.
When the microbiome is diverse and well-nourished, it supports neurotransmitter production, keeps inflammation in check, and helps regulate the stress response. When it is depleted — by poor diet, chronic stress, antibiotics, or ultra-processed food — those functions degrade. Studies have found that people with less diverse gut microbiomes show higher rates of depression, anxiety, and cognitive difficulty. The relationship is not coincidental.
If the gut lining becomes compromised, a condition often referred to as “leaky gut” or increased intestinal permeability can occur, allowing bacterial byproducts to cross into the bloodstream and trigger an inflammatory response. Those inflammatory cytokines circulate throughout the body and brain. Elevated levels of inflammatory markers have been consistently associated with depression, cognitive slowing, reduced motivation, and emotional dysregulation.
What Inflammation Does to a Leader
For a leader, this may show up as difficulty accessing flexible, integrative thinking when complex problems arise. It can mean a shorter fuse, less capacity to tolerate ambiguity without anxiety, more irritability, less empathy, diminished creativity, and a greater likelihood of burnout.
The physiology of burnout overlaps substantially with what happens when the gut-brain axis is chronically stressed and the microbiome becomes depleted. Dysregulated cortisol, disrupted sleep, emotional exhaustion, reduced cognitive flexibility, and impaired recovery pathways all begin reinforcing one another. Research has found that chronic psychological stress alters the composition of the gut microbiome, and that an already-compromised microbiome can amplify the body’s stress response. The cycle reinforces itself.
This is particularly relevant in leadership culture because lifestyle and behaviors patterns thatmany high-performing professionals follow are often drivers of inflammation. Examples include eating on the run, relying on ultra-processed convenience foods, under-sleeping, over-caffeinating, remaining chronically activated, and functioning in prolonged states of physiological stress. Over time, that terrain affects cognition, emotional regulation, recovery capacity, and the ability to remain grounded under pressure.
What the Research Points Toward
When researchers look at dietary patterns associated with better mental health outcomes, the same themes tend to emerge repeatedly: more whole foods, more plant diversity, more fiber, more healthy fats, more fermented foods, and far fewer ultra-processed ingredients.
A landmark randomized controlled trial published in 2017 found that dietary intervention along Mediterranean lines produced significant reductions in depression symptoms, with about a third of participants achieving full remission. This is a diet rich in vegetables, legumes, whole grains, olive oil, fish, nuts, and fermented foods. A 2019 meta-analysis confirmed that higher adherence to Mediterranean eating patterns was associated with substantially lower risk of depression.
The research points more toward patterns than perfection. The gut microbiome responds relatively quickly to dietary change, and shifts in cognition, mood, energy, and emotional regulation can follow.
Where to Start
For leaders and anyone navigating high cognitive and emotional demand, a few shifts carry disproportionate weight.
Prioritize fiber diversity. The gut microbiome is fed primarily by plant fiber, and variety matters more than quantity — different plant foods feed different microbial species. Thirty different plant sources per week is a research-supported target. A large-scale study found that people eating more than 30 different plant foods weekly had significantly more diverse microbiomes than those eating fewer than 10.
Add fermented foods. Yogurt, kefir, kimchi, sauerkraut, miso — these introduce live microorganisms that support microbial diversity. A Stanford study published in 2021 found that a diet high in fermented foods increased microbiome diversity and reduced markers of inflammation over ten weeks.
Reduce ultra-processed food. This category — not junk food specifically, but industrially processed products with long ingredient lists — is consistently associated with poorer mental health outcomes. One prospective study found a dose-dependent relationship between ultra-processed food consumption and depression risk.
Attend to omega-3 intake. Fatty fish, walnuts, and flaxseed provide omega-3 fatty acids that support neuronal membrane function and have demonstrated anti-inflammatory and mood-stabilizing effects in multiple clinical trials.
Minimize high-glycemic eating under stress. Reaching for refined carbohydrates under pressure is understandable because they create a rapid glucose spike and temporary relief. The crash that follows tends to amplify cortisol fluctuations, emotional reactivity, and energy instability — the opposite of what sustained performance requires.
None of this replaces the organizational, relational, and psychological work that burnout and mental health in the workplace genuinely require. It does, however, add a biological layer that helps determine whether therapy, coaching, mindfulness practices, resilience work, and leadership development efforts have a stable foundation to build on.
The gut, it turns out, has a great deal to say about who shows up to lead.
