Key Takeaways

• Support serotonin and stable blood sugar with nutrient-dense foods containing tryptophan, fiber-rich carbohydrates, B-vitamins, Vitamin C, and D.
• Combine balanced meals with practical strategies like morning light exposure, outdoor activity to maintain energy, and uplift mood this fall and into winter.
• Use tools like a CGM to track your response and seek professional counseling, if needed, for mental health support.

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Early fall brings about many changes: cooler temps, trees changing color and losing their leaves, and less daylight. By the end of September, most areas of the U.S. will lose about an hour of daylight, with the rate of daylight loss accelerating even more through October. 

Here’s the kicker: shorter days don’t just mean sweaters and pumpkin patches. They shift your internal wiring. Blood sugar gets shakier. Serotonin production dips. Cravings rise. Energy levels yo-yo. If you’ve felt mood swings or sluggishness creep in, you’re not imagining it; it’s biology.¹

This is your guide to protecting serotonin, stabilizing blood sugar, and keeping energy and well-being steady as the fall season sets in.

Why Early Fall Often Triggers Mood Swings and Energy Lows

When daylight shrinks, your nervous system takes the hit. It’s not just “less sunshine = less happy.” Your brain, hormones, blood sugar, and even cravings get rewired in subtle but powerful ways. Here’s how the dominoes fall:

• Seasonal affective disorder (SAD): More than just a bad mood, SAD is a clinically recognized mood disorder that peaks during the winter months. Symptoms include daytime sleepiness, carbohydrate cravings, fatigue, lower levels of physical activity, and mood swings that feel hard to shake.¹ Even if you don’t meet the full criteria for SAD, you might still notice energy slumps, overeating, or creeping weight gain tied to the shorter days.¹
• Neurotransmitter disruption: Sunlight regulates serotonin, the “feel-good” neurotransmitter, and melatonin, your sleep hormone. Less light exposure leads to reduced serotonin production and lower levels of mood stability. At the same time, melatonin timing shifts, making you feel groggy during the day and wired at night. That one-two punch sets the stage for symptoms of depression, cravings, and irritability.^1,2
• Blood sugar volatility: When energy tanks, your body craves quick fixes, usually processed foods loaded with sugar or refined carbs. The problem? Those foods spike glucose fast, then send it crashing. Every swing in blood sugar is mirrored by a swing in mood regulation, leaving you irritable, anxious, and prone to even more cravings.
• Circadian confusion: Light is the anchor for your internal clock. Without steady exposure to natural sunlight in the morning, your circadian rhythm drifts. Sleep gets choppier, melatonin secretion shifts, and endorphins (the body’s natural antidepressants) drop. Brain function slows, and the nervous system struggles to maintain balance across hormones, neurotransmitters, and energy levels.

Not everyone develops full SAD, but even subclinical “winter blues” can tank self-esteem, energy levels, and overall well-being if you don’t get ahead of it. Think of it as your body whispering early warning signs (mood swings, cravings, restless sleep) before it escalates. Catch those whispers, and you can intervene with food, movement, light, and metabolic strategies that keep you stable through the darkest months.

From Darkness to Chemistry: Why Serotonin and Blood Sugar Hold the Keys

If SAD and “winter blues” are the symptoms, serotonin and blood sugar are the levers underneath. These two systems are wired into your nervous system and brain function, and both are influenced by daylight, diet, and daily habits.

• Serotonin acts like your internal mood stabilizer, shaping appetite, sleep, and emotional well-being. When levels of serotonin drop, cravings spike, energy dips, and symptoms of depression get louder.
• Blood sugar is your brain’s fuel supply. Glucose volatility sends neurons into overdrive, then leaves them stranded, which is why you feel the emotional rollercoaster alongside the physical one.

Together, serotonin and blood sugar create the metabolic triangle of mood, energy, and cravings. Understand this relationship, and you’ll have a roadmap for how to stay balanced, even as the winter months bring shorter days and longer nights.

Serotonin, Blood Sugar, and Energy: How They Interact

Serotonin is often called the “feel-good” neurotransmitter, a mood booster linked to happiness, cravings, and overall health. But here’s the catch:

• Made in your gut, powered by food: About 95% of serotonin is produced in the gut from tryptophan, an amino acid found in protein foods like turkey, chicken, and eggs.³
• Carbs unlock the door: Carbohydrates (whole grains, oats, quinoa) trigger insulin, which helps tryptophan cross into the brain, where it gets turned into serotonin.^4,5
• Blood sugar balance matters: Stable glucose means steadier energy levels, better mood regulation, and fewer symptoms of depression. Big spikes and crashes? They hit dopamine and serotonin hard, leaving you more irritable and less resilient.^5,6

As the minutes of sunlight tick away throughout September, it’s vital to understand the interplay between sunlight, serotonin, and blood glucose, and how food choices, vitamins, and habits can further worsen the balance.

Micronutrients That Back Your Brain

When serotonin and glucose stability wobble, nutrients become your best allies:

• B vitamins (thiamin, riboflavin, niacin, folate): Critical for brain function, neurotransmitter production, and mood regulation.⁷
• Vitamin D and natural sunlight: Supports serotonin production, though vitamin D levels vary with light exposure.⁷
• Magnesium and antioxidants: Fight oxidative stress, calm the nervous system, and help with mood swings.
• Omega-3 fatty acids (fatty fish, walnuts): Improve brain function, balance neurotransmitters, and reduce symptoms of depression.
• Probiotics & gut health: Healthy gut = stronger serotonin production + better mood regulation.

Supplements can help, but lifestyle changes and a balanced diet build the strongest foundation. 

Fall Mood-Boosting Foods That Support Serotonin and Steady Energy

With a greater understanding of the interplay between nutrients, mood, and the changing seasons, target nutrient-dense foods that pull double or triple duty. 

Choose foods that fuel stable blood sugar, offer key nutrients like tryptophan, fiber-rich carbohydrates to help tryptophan get to the brain, B-vitamins, Vitamin C and D, and seasonal fall foods, like the following:

• Pumpkin: fiber + carbohydrates
• Butternut squash/acorn squash: fiber + carbohydrates, B-vitamins, vitamin C
• Brussels sprouts: fiber, vitamin C, folate
• Apples: fiber + carbohydrates, vitamin C
• Pears: fiber + carbohydrates, vitamin C
• Cranberries: fiber + carbohydrates, vitamin C
• Beef, chicken, pork, turkey, and fish: rich in B vitamins, protein, and tryptophan
• Eggs: rich in B vitamins, protein, tryptophan, and some vitamin D
• Pumpkin or sunflower seeds: tryptophan, B vitamins, protein, fiber, and healthy fats
• Legumes (lentils, chickpeas, black beans): B-vitamins, fiber + carbohydrates
• Oats and oatmeal: fiber + carbohydrates, B-vitamins
• Quinoa: protein + fiber + carbohydrates, B-vitamins
• Fatty fish (salmon, sardines): healthy omega-3 fatty acids, vitamin D, B-vitamins
• Mushrooms: vitamin D, B-vitamins, fiber

The Signos Approach to Mood and Energy Stability in Fall

When the days get shorter, your biology shifts. But you’re not powerless; you just need the right tools to decode what’s happening inside your body. That’s where Signos comes in. By pairing real-time glucose insights with seasonal nutrition strategies, you can build a playbook for better mood regulation, steadier energy levels, and improved overall well-being through the darker months.

Here’s how the Signos approach works in action:

• Glucose-Informed Eating: Your CGM shows exactly how different foods hit your blood sugar. Use that data to fine-tune your fall meals and smooth out the energy swings that drag mood and focus down.
• Balance Your Plate: Complex carbs paired with lean protein and healthy fats do more than stabilize blood sugar levels; they also help increase serotonin availability and sustain steady brain function.
• Add Light to Your Day: Your circadian rhythm craves anchors. Outdoor sunlight or a morning light therapy session can reset melatonin timing, boost serotonin production, and help regulate endorphins.
• Focus on Mood-Boosting Nutrients: Build meals with serotonin-supportive nutrients like tryptophan, omega-3 fatty acids, B vitamins, and magnesium. Each one is a mood booster in its own right, and together they help regulate neurotransmitters and nervous system balance.

Instead of guessing which habits actually move the needle, Signos lets you see it. Track your unique response to foods, light, and lifestyle changes; then double down on what works for your mood, metabolism, and mental health this fall and winter.

Habits That Work with Early Fall Rhythms to Uplift Mood

Mood-boosting foods are just one piece: layering habits that support circadian and metabolic balance makes early fall more energizing.

• Light therapy: 30 minutes daily in the morning to reset circadian rhythms and boost serotonin. Research shows improvement after 2-3 weeks of 30-minute daily sessions (preferably in the morning).¹
• Physical activity: Exercise is a natural antidepressant (endorphins and dopamine).
• Outdoor time: Natural sunlight boosts vitamin D and melatonin balance.Sit outside while eating your breakfast before work, take your lunch break outside or near a window, especially if your workday limits daylight exposure.
• Sleep consistency: Anchors mood regulation and blood sugar levels.
• Social connection: Combat loneliness, boost self-esteem, and protect overall health.
• Professional support: If symptoms of depression linger, psychiatry and antidepressants may be part of your care plan.¹

Metabolic Playbook: Fall Edition

Want to outsmart the winter blues and keep your energy steady? Here’s your metabolic cheat sheet:

• Anchor carbs with protein and healthy fats
• Load up on leafy greens & whole grains: Folate, B vitamins, and fiber are non-negotiable mood boosters.
• Prioritize gut health: Add probiotics (yogurt, kefir, kimchi) for stronger serotonin production via gut-brain signaling.
• Watch cravings: Processed foods may give short highs but tank glucose and serotonin. Swap refined carbs for fiber-rich carbs.
• Supplement smartly: If vitamin D levels, magnesium, or B vitamins are low, healthcare providers may recommend supplements to fill gaps.
• Move daily: Physical activity is as effective as light therapy in boosting dopamine and serotonin.

Sample Fall Meals, Signos-Style

• Autumn Soup made with pumpkin, butternut squash, carrots, apples, onions, chicken bone broth, garlic, cumin, cinnamon, nutmeg, topped with pumpkin seeds, and paired with whole grain bread.
• Beef and Mushroom Quinoa, featuring sautéed beef and mushrooms, served over quinoa with garlic.
• Apple, Pear Oatmeal, topped with sunflower seeds, and paired with a hard-boiled egg.

Each plate balances carbs, amino acids, and healthy fats to boost serotonin and keep blood sugar smooth.

The Bottom Line

As the fall season trims your daylight, don’t let serotonin and blood sugar slip. Seasonal affective disorder and winter blues are real, but they’re not inevitable.

A balanced diet rich in tryptophan, whole grains, leafy greens, fatty fish, and healthy fats, paired with light therapy, physical activity, and Signos glucose insights, gives you a playbook to increase serotonin, stabilize mood swings, and protect your overall health.

Mood regulation isn’t just psychiatry or supplements; it’s lifestyle changes that keep your neurons firing, your self-esteem intact, and your energy steady. With the right moves, the winter months can still feel like your season.

Learn More With Signos’ Expert Advice

A CGM not only lets you see how your glucose responds to different types of food and physical activity, but also daylight exposure and seasonal changes. Prioritizing nutrition in early fall can help your mood, glucose levels, and improve your overall health.

Learn more about glucose levels and tracking on the Signos blog, written by health and nutrition experts.