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Why Gut Health Is the Starting Point for Sleep, Mood and Immunity

Once seen as just a digestive organ, the gut is now understood to shape everything from hormone regulation to mental clarity. Here's how to eat in sync with your body's command center.

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Gut health has evolved from a niche wellness trend to a centerpiece of modern medicine. While we’ve long known that diet influences how we feel, mounting research shows just how deeply food choices affect everything from hormone balance to mental clarity. Along the gut-brain axis—a two-way communication pathway between the digestive tract and the brain—trillions of microbes regulate inflammation, shape immune response and influence brain production of mood-related chemicals like serotonin and dopamine. Nutrition, in turn, is a powerful lever to support health. Here are simple, evidence-based strategies to strengthen three core systems—sleep, mood and immunity—from the inside out.

Ingest to Rest 

Inside the belly’s microbial ecosystem, certain nutrients help make the calming brain chemicals that lull us into stillness. Tryptophan—the amino acid behind holiday turkey talk—is the starting point for the production of the sleep-regulating hormone melatonin. But it’s not about eating more turkey (which actually has less tryptophan than foods like seeds and soybeans)—or, any other one ingredient. 

Sleep nutrition is part of a deeper equation, requiring complex carbs to help the amino acid reach the brain and do its job; magnesium, which activates the calming neurotransmitter GABA; and a diverse, well-fed microbiome to support the whole process. Vitamins D, B6, folate, iron and magnesium also act as backstage crew to convert nutrients into their sleep-enhancing forms. Rich in all these compounds, the Mediterranean diet rises to the top as one of the most sleep-supportive ways of eating, thanks to its emphasis on fiber-rich plants, healthy fats like fish and nuts, and anti-inflammatory nutrients. 

Chrononutrition—the emerging science of eating in sync with your internal clock—shows that when you eat can affect sleep quality. Blood sugar regulation and digestion are most efficient earlier in the day, when the body is naturally primed to move. Experts recommend shifting your largest meal to earlier in the day and keeping food intake within an 8- to 10-hour daytime window to avoid taxing digestion when the body should be shifting into rest-and-repair mode. Time your last meal for two to three hours before bed to allow time for digestion and sleep-supportive compounds to do their job.

Evening habits have the biggest impact. When I help clients adjust their dinner routines, many notice a profound shift: fewer 3 a.m. wake-ups and more energized mornings. To facilitate sleep-mode, keep your final meal small and centered around fiber for fullness, healthy fats for hormone regulation, lean proteins rich in tryptophan and complex carbs to help it do its job. A go-to could be sweet potatoes with lentils, sautéed greens and pumpkin seeds. Avoid heavy, meat-laden or starchy pasta dinners, which can delay melatonin production and keep you awake. A simple switch from white to fibrous whole wheat pasta can help stabilize levels and set the tone for a more restful night. Skip dessert at night to reduce late-night blood sugar swings and wake-ups. If you’re still hungry closer to bedtime, a small fibrous snack, such as a banana with almond or cashew butter, can satiate while delivering a final wave of tryptophan and magnesium, which supports sleep onset, duration and quality.

On the other hand, some seemingly harmless habits can interfere with sleep. Caffeine’s effects can linger in the body for up to 10 hours. Dark chocolate, sodas and certain teas may contain just enough to delay melatonin release. Similarly, a glass of wine can feel like it’s helping you unwind, but even one drink can disrupt REM sleep and cause wake-ups as the liver kicks into gear to metabolize the alcohol. If you’re going to indulge, aim to have your final sip at least three hours before bed.

For those who struggle to stay asleep, tart cherries could help. Naturally rich in melatonin, the fruit has been shown in multiple placebo-controlled studies to increase total sleep time and efficiency, particularly in older adults and people with insomnia. 

Mood on the Menu 

The connection between food and mood isn’t just about comfort—it’s rooted in the gut, where trillions of microbes pull the strings on inflammation, hormone levels and the nutrients used to build happy neurotransmitters like serotonin and dopamine. Microbes also send signals to the brain, influencing how we feel, focus and respond to stress.

Diets low in fiber, high in sugar and full of processed foods have been linked to inflammation and reduced gut diversity, both of which disrupt brain function and raise the risk of anxiety and depression. Junk food and irregular eating patterns also destabilize blood sugar, which can trigger mood swings, irritability and trouble focusing—symptoms that can mimic or worsen underlying mental health conditions. In contrast, meals rich in whole foods, a rainbow of produce and fermented ingredients support the gut-brain axis, helping buffer stress and sharpen mental clarity. 

I suggest building meals around what I call ‘mood nutrients’: B vitamins (especially B-6, B-12 and folate) for neurotransmitter production; magnesium to ease the nervous system; omega-3s to reduce brain inflammation; fermented foods to introduce and support beneficial bacteria; and iron and zinc, which help synthesize mood chemicals. Phenylalanine—an amino acid found in eggs, soy, and yogurt—is also key for producing dopamine, which plays a central role in motivation and focus. Together with tryptophan, which supports serotonin, these protein-based precursors help regulate how we feel, think and respond to stress. My own meals are simple but intentional: eggs with greens and avocado for breakfast; quinoa and lightly roasted vegetables with olive oil for lunch; yogurt with berries, flax and prebiotic oats in the afternoon. Don’t overlook hydration—dehydration can sneakily mimic mood dips. And, go easy on caffeine, which can spike anxiety.

The body may crave a quick feel-good hit from sugar or refined carbs—but that spike often leaves us more jittery than grounded. Instead of letting cravings steer you off course, try these fast, grounding daytime snacks: a few squares of dark chocolate with almond butter, roasted chickpeas tossed with olive oil and sea salt for a chip-like crunch, or a slice of sourdough with tahini and honey. They satisfy, stabilize and deliver the mood nutrients your nervous system can actually use. 

Mood thrives on rhythm. Skipping breakfast, pushing lunch too late or grazing late at night can also trigger blood sugar crashes and stress responses, including cortisol spikes. Even minor timing shifts can throw your system off. To avoid the dreaded 3 p.m. slump, schedule meals around the same times each day. When your body knows what to expect, it can prepare, digesting more efficiently and delivering energy more evenly throughout the day.

If you’re running late, don’t skip the meal altogether or grab something sugary just to get through. Reach for something fast but substantial—like a slice of sourdough with avocado and a boiled egg or full-fat Greek yogurt with berries and walnuts—to restore focus and keep your day steady. Then, return to your usual rhythm at the next meal.

Fortifying Fare 

We tend to think of immune health in crisis terms—something to support only when we’re run-down or already sick. But the immune system is always working: identifying threats, regulating inflammation, repairing tissue. To thrive, your defenses need steady support over time—you can’t just ‘turn them on’ with an orange when you feel a cold coming on. You want to nourish the system consistently—and it’s fueled, in large part, by the gut. 

Diversity is key here. Most immune activity takes place in the gut, where defense cells need a wide variety of beneficial microbes to function properly. A diverse microbiome helps ‘train’ immune cells—teaching them how to recognize real threats and stay calm in the face of harmless triggers to reduce overreactions like allergies or autoimmune flare-ups. Variety also strengthens the gut lining, the body’s internal border patrol, so nutrients get absorbed and pathogens kept out. Beyond known gut-friendly fermented foods like sauerkraut or yogurt, whole plants are especially powerful. Many are rich in prebiotic fibers—the preferred fuel for good gut bugs—and even those that aren’t classified as prebiotic often support microbial diversity. Deeply pigmented fruits like berries or pomegranates, for instance, are loaded with polyphenols—compounds your good bacteria like. Aim for 30 different plant foods each week. Rotating base grains and greens—quinoa and spinach one day, farro and kale the next—is an easy way to get there. Garlic and shallots are smart additions, as they’re packed with prebiotic compounds.

Beyond a varied microbe diet, immune cells need consistent access to core nutrients to function well—and they’re easy to integrate, starting with your first meal of the day. I often reach for a bowl of citrus and berries (whatever’s in season), paired with a fat- or zinc-rich food like nut butter or pumpkin seeds. Zinc supports communication between immune cells, helping them coordinate and multiply. Vitamins A and D, and iron, are also critical, helping generate the right cells to recognize threats and respond effectively. Vitamin D, one of the most common deficiencies, is best absorbed with fat; if you supplement, it’s easy to take it with breakfast, where you can have eggs, avocado or buttered toast.

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gut health for overall health mushrooms

Photography by Anna Nguyen

gut health for overall health mushrooms

While citrus gets the glory, several other foods power immunity. Shiitakes help train defender cells and support faster recovery when you’re run down.

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gut health for overall health asparagus dish

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gut health for overall health asparagus dish

Asparagus feeds the gut’s good bacteria with inulin, a prebiotic fiber that sharpens immune response and fortifies the gut barrier.

Next-up: go-to player vitamin C, which defends the body’s outermost barriers (the skin, mucous membranes) by enhancing cellular repair and reducing inflammation. Hydration backs it up, keeping your airways and gut lining moisturized, so they can trap and flush out pathogens. I aim for about 100 ounces of water a day.

Omega-3s, from fish or flax, also go in most of my meals; they help immune cells communicate and calm inflammation. Selenium, found in Brazil nuts and seafood, also aids recovery, pumping the brakes on inflammation and helping the immune system return to baseline after an illness or injury. 

Eating with your microbiome in mind is not just about chasing better sleep, fewer sniffles or lower stress; it’s about creating a healthy environment from the inside out.