Understanding What Drives Food Sensitivities &
Why the Nervous System Matters

Food sensitivities are one of the most confusing and frustrating digestive issues. Reactions can appear hours or even days after eating, and triggers often change over time.

Food sensitivities are not the same as true allergies. They are delayed, dose-dependent reactions that reflect how well the digestive system, immune system, microbiome and nervous system are functioning together.

Many people with food sensitivities find their list of “safe foods” gradually shrinking, even though they are eating carefully.

What Food Sensitivities Really Are

Food sensitivities usually develop when food is not fully broken down, the gut lining becomes more permeable, and immune tolerance is reduced.

Common contributors include:

  • low stomach acid or weak digestive enzyme output

  • dysbiosis, SIBO or Candida overgrowth

  • increased intestinal permeability (leaky gut)

  • chronic inflammation of the gut lining

  • repeated or long-term stress

  • nutrient deficiencies

  • restrictive dieting or frequent food avoidance

  • past gut infections or food poisoning

  • use of acid-suppressing or anti-inflammatory medication

This is why reactions often feel unpredictable and why removing more and more foods rarely solves the underlying problem.

The Gut–Brain Axis

The immune system and digestive system are both highly sensitive to nervous system signalling.

When the body is in fight, flight, freeze or shutdown, digestion becomes less efficient and immune tolerance decreases. This makes the gut more reactive to foods that were previously tolerated.

Many people notice sensitivities worsen during:

  • stressful periods

  • emotional strain

  • poor sleep

  • burnout

  • major life changes

For some, food reactions become another way the body signals that it does not feel safe.

Why Common Food Sensitivity Advice Falls Short

Elimination diets and food avoidance can reduce symptoms temporarily, but they often do not address:

  • why digestion is impaired

  • why the gut lining is inflamed or permeable

  • why the microbiome is imbalanced

  • or why the nervous system remains in a state of threat

Over time, this can lead to nutritional deficiencies, increased anxiety around food and further restriction.

What Actually Helps Long Term

Long-term improvement focuses on restoring tolerance rather than avoiding more foods.

This often involves:

Supporting digestion
Improving stomach acid and enzyme output.

Healing the gut lining
Reducing inflammation and supporting barrier function.

Balancing the microbiome
Addressing overgrowths and rebuilding beneficial bacteria.

Rebuilding immune tolerance
Through nutrition and gradual food reintroduction.

Regulating the nervous system
So the gut becomes less reactive and more resilient.

Restoring food confidence
So eating becomes calm and nourishing again.

When these layers are supported together, many people find they can tolerate a wider range of foods and feel less fearful around eating.

TLDR

What drives food sensitivities
Food sensitivities develop when digestion is incomplete, the gut lining becomes more permeable, the microbiome is imbalanced and immune tolerance is reduced.

The role of the nervous system
Stress states impair digestion and increase immune reactivity, making food responses more likely and more severe.

In short
Food sensitivities are rarely just about the food itself. They reflect a digestive–immune–microbiome–nervous system pattern. When these systems are supported together, tolerance can return.

This is the Mind–Body–Biome approach.