Food Sensitivities:

What They Are and How They Inflame the Body and Brain

Even when you eat what seems like a balanced diet, you might notice fluctuations in your mood, brain fog, irritability, or anxiety. One often-overlooked contributor to these symptoms is food sensitivities. Recent research highlights how immune reactions to certain foods can disrupt neurotransmitter function, trigger inflammation, and alter the brain-gut connection, influencing mood and cognition (Gibson et al., 2020). Understanding food sensitivities isn’t just about elimination diets. It’s about uncovering hidden triggers, supporting digestion, and creating a sustainable approach that nourishes both gut and brain.

How Food Sensitivities Affect the Brain

Food sensitivities differ from classic allergies. They often involve delayed immune responses mediated by IgG, IgA, or other pathways, rather than immediate IgE reactions. This means symptoms can appear hours—or even days—after eating a trigger food. The immune response still triggers inflammation which can have numerous downstream effects, but the acute effect is less pronounced or severe as an IgE mediated allergic reaction i.e. hives, eczema, difficulty breathing, dizziness or fainting etc. Allergies and sensitivities therefore are not the same.

When the immune system is activated by these foods, inflammatory cytokines like IL-6 and TNF-alpha are released, which can cross the blood-brain barrier and influence mood and cognition. These immune responses can interfere with the synthesis and release of key neurotransmitters such as serotonin, dopamine, and GABA. They also affect the gut-brain axis, worsening intestinal permeability and dysbiosis, which further alters brain function. This chronically inflamed state is associated with autoimmune conditions, skin flares, depression, and neurodegenerative disorders. Over time, chronic immune activation results in diminished neuroplasticity, neurogenesis, altered amino acid metabolism, and central nervous system apoptosis, or cell death, resulting in mood disturbances, memory impairment and diminished stress resilience. This will also result in diminished intestinal absorptive capacity resulting in malnourishment despite adequate intake.

Common Food Sensitivities

Some foods are more likely to trigger reactions than others. Dairy is a frequent culprit, as are gluten-containing grains, soy, eggs, and nightshades like tomatoes, peppers, and eggplant. Certain food additives and preservatives—think MSG, artificial colors, and emulsifiers—may also exacerbate symptoms in sensitive individuals. While dairy and gluten sensitivities are the most common, these sensitivities are highly individual. What triggers inflammation in one person may be perfectly tolerated by another, which is why testing and careful observation are so important. Furthermore, as the microbiome changes for better or worse food sensitivities can as well. You may not have been sensitive to one food at an earlier time but went through a period of stress and poor diet and notice changes as a result. Conversely, many sensitivities may be present during initial testing but after a period of removing the triggers and fortifying the gut, the majority disappear and those old food groups can be gently reintroduced. It is a fluid process–by strengthening the microbiome we can become more resilient or metabolically flexible over time.

How Food Sensitivities Influence Mood

The effects of food sensitivities on mental health are complex but well-documented. Immune activation from food triggers can create systemic inflammation that disrupts neurotransmitter balance, particularly serotonin, dopamine, and GABA. Chronic inflammation can also influence the HPA axis, altering cortisol rhythms and reducing resilience to stress. Meanwhile, disruptions to the gut microbiome and intestinal barrier can impair short-chain fatty acid (SCFA) production and vagal nerve signaling, which are critical for healthy mood regulation. Simultaneously, increasing levels of dysbiosis can result in more lipopolysaccharide production from gram negative bacteria resulting in a steady stream of inflammation.

In short, food sensitivities can act like a slow-burning irritant: quietly affecting mood, focus, motivation, and energy until they become hard to ignore.

Steps to Support Yourself

Addressing food sensitivities is not about restrictive dieting or guesswork. Start by paying attention to how different foods make you feel, keeping a simple food and symptom journal. Clear signs are of being stuffy, mucousy, having digestive upset, diarrhea, gas and bloating. Less obvious but directly connected symptoms as previously stated are changes in mood, memory, and clarity, as well as various aches and pains and skin conditions including eczema, rashes, itches, acne and the like.

Here’s what to do: prioritize whole, minimally processed foods and reduce common inflammatory triggers like gluten and dairy to start. Supporting digestion through chewing, hydration, and occasional digestive enzymes—can also help. Primarily focus on fortifying the gut microbiome with fiber, prebiotics, and fermented foods. Doing so helps strengthen the gut-brain connection, while managing stress through mindfulness, movement, or breathwork can reduce immune overactivation.

How We Can Support

If doing a careful elimination test and guessing which foods to include or exclude, what ratios macros should be, and what proportion sizes are best for you seems like a headache, we are happy to support.

At Seed to Fruit, we take a functional approach to food sensitivities and mental health. We focus on:

● Identifying foods that may contribute to inflammation and gut irritation through observation and testing i.e. no guessing.

● Implementing targeted elimination and guided reintroduction to reveal triggers without creating an overly restrictive diet.

● Supporting gut repair and microbial balance with nutrients, probiotics, and anti-inflammatory strategies.

● Integrating nutrition, lifestyle, sleep, stress management, and movement to create lasting mental and digestive health improvements.

By addressing food sensitivities and supporting gut health, it’s possible to improve mood, clarity, energy, and overall well-being. With a careful, personalized approach, you can restore balance and reclaim emotional and cognitive resilience.

References

● Gibson, P. R., et al. (2020). Food sensitivities and the gut-brain axis: Clinical evidence and mechanisms. Nutrients, 12(12), 3674. https://doi.org/10.3390/nu12123674

● Lattimer, J. M., & Haub, M. D. (2010). Effects of dietary fiber and its components on metabolic health. Nutrients, 2(12), 1266–1289. https://doi.org/10.3390/nu2121266

● Halmos, E. P., et al. (2014). Diet and functional gastrointestinal disorders. Gastroenterology, 146(6), 1515–1523. https://doi.org/10.1053/j.gastro.2014.02.011

You might be eating what seems like a “healthy” diet, yet still notice mood swings, brain fog, irritability, or anxiety. Often overlooked, food sensitivities may be silently influencing your mental health. Emerging research highlights how immune reactions to certain foods can disrupt neurotransmitters, trigger inflammation, and alter brain function (Gibson et al., 2020).

Understanding food sensitivities isn’t just about elimination diets—it’s about uncovering hidden triggers, supporting digestion, and creating a sustainable approach that nourishes both gut and brain.

The Science Behind Food Sensitivities and the Brain

Food sensitivities differ from classic food allergies. They typically involve delayed immune responses mediated by IgG, IgA, or other immune pathways, rather than immediate IgE reactions. This means symptoms may appear hours or even days after consuming the food.

How they impact mental health:

● Inflammation: Immune activation from sensitive foods can elevate cytokines (IL-6, TNF-alpha), which cross the blood-brain barrier and influence mood and cognition.

● Neurotransmitter disruption: Inflammatory signals and gut irritation can interfere with the synthesis and release of serotonin, dopamine, and GABA.

● Gut-brain axis: Food sensitivities can worsen intestinal permeability (“leaky gut”), dysbiosis, and microbial imbalance, which in turn impact brain function.

● Energy and cognition: Chronic immune activation can sap energy, impair focus, and contribute to brain fog or low motivation.

Most Common Food Sensitivities

● Dairy: Especially A1 beta-casein proteins; linked to inflammation and digestive distress.

● Gluten: Can provoke systemic inflammation and influence mood in sensitive individuals, even without celiac disease.

● Soy: May impact thyroid function and hormone balance in susceptible people.

● Eggs: Proteins in egg whites can trigger IgG-mediated responses.

● Nightshades (tomatoes, peppers, eggplant): Sometimes provoke gut inflammation or worsen autoimmune symptoms.

● Additives and preservatives: Food colorings, emulsifiers, and MSG may exacerbate cognitive or behavioral symptoms in sensitive individuals.

How Food Sensitivities Contribute to Mood Challenges

The immune activation triggered by food sensitivities can cascade into multiple pathways affecting mental health:

1. Inflammation: Cytokines signal the brain, affecting neurocircuitry involved in mood and motivation.

2. Neurotransmitter imbalance: Amino acid precursors like tryptophan and tyrosine may be diverted toward immune responses instead of serotonin or dopamine production.

3. Gut-brain communication: Food-triggered dysbiosis or permeability alters short-chain fatty acid (SCFA) production and vagal signaling, influencing cognition and emotional regulation.

4. Stress amplification: Ongoing immune activation and discomfort can exacerbate HPA axis dysregulation, increasing cortisol and reducing resilience.

What You Can Do at Home

● Track and observe: Keep a food and symptom journal to identify patterns in mood or cognition after meals.

● Prioritize whole foods: Minimize processed foods, additives, and common inflammatory triggers.

● Rotate potentially reactive foods: Avoid repetitive exposure until gut health is optimized.

● Support digestion: Chew thoroughly, stay hydrated, and include digestive enzymes or betaine HCl if indicated.

● Balance gut flora: Fiber, prebiotics, and fermented foods can support microbial diversity.

● Manage stress: Chronic stress can worsen immune reactivity to food, so integrate mindfulness, movement, or breathwork.

How We Can Support

At Seed to Fruit, we focus on functional strategies for identifying and mitigating food sensitivities while supporting gut and mental health:

● Careful evaluation: Not all gut or mental symptoms indicate the same sensitivity; testing combined with observation allows for personalized interventions.

● Targeted elimination and reintroduction: Guided protocols help identify triggers without overly restrictive diets.

● Gut repair and resilience: Support with nutrients, probiotics, and anti-inflammatory strategies to reduce permeability and improve microbial balance.

● Holistic integration: Nutrition, lifestyle, sleep, stress management, and movement are combined for sustainable mental and digestive health.

Addressing food sensitivities can dramatically improve mood, cognition, energy, and overall well-being. With a careful, functional approach, it’s possible to restore balance and reclaim clarity, focus, and emotional stability.

References

● Gibson, P. R., et al. (2020). Food sensitivities and the gut-brain axis: Clinical evidence and mechanisms. Nutrients, 12(12), 3674. https://doi.org/10.3390/nu12123674

● Lattimer, J. M., & Haub, M. D. (2010). Effects of dietary fiber and its components on metabolic health. Nutrients, 2(12), 1266–1289. https://doi.org/10.3390/nu2121266

● Halmos, E. P., et al. (2014). Diet and functional gastrointestinal disorders. Gastroenterology, 146(6), 1515–1523. https://doi.org/10.1053/j.gastro.2014.02.011