How Food and Substances Affect Emotions and Brain Function
How Food and Substances Affect Emotions and Brain Function
1. The Gut-Brain Axis
The gut is often referred to as the “second brain” because it contains millions of neurons and produces neurotransmitters (like serotonin).
90–95% of serotonin (the mood-regulating neurotransmitter) is made in the gut.
The gut and brain communicate bi-directionally via the vagus nerve and chemical messengers.
Evidence:
A 2020 study in Nutritional Neuroscience found that gut microbiome imbalances are associated with anxiety, depression, and heightened neuroticism.
Probiotic and prebiotic interventions (e.g. fermented foods, fibre) have been shown to reduce emotional reactivity and improve mood.
2. Inflammatory Foods and Neuroinflammation
Diets high in ultra-processed foods, sugars, and trans fats have been linked to chronic low-grade inflammation, which affects brain health.
Neuroinflammation has been associated with increased symptoms of depression, anxiety, and cognitive decline.
Evidence:
A 2015 study in Brain, Behavior, and Immunity linked systemic inflammation markers (like CRP and IL-6) with higher levels of neuroticism and mood disorders.
3. Blood Sugar and Mood Instability
Highly refined carbohydrates and sugary foods can cause rapid blood sugar spikes and crashes, affecting mood regulation and emotional resilience.
These crashes can mimic or trigger symptoms of anxiety, irritability, and brain fog.
Evidence:
A 2019 study in Neuroscience & Biobehavioral Reviews showed that high glycaemic index diets were associated with increased depressive symptoms.
4. Caffeine, Alcohol, and Other Substances
Caffeine: Can heighten alertness but may increase anxiety and neuroticism in sensitive individuals or in high doses.
Alcohol: Acts as a depressant. While it may momentarily numb emotions, regular consumption is linked to worsened mood regulation and impulsivity.
Nicotine, cannabis, and other psychoactives affect neurotransmitter systems in nuanced ways, sometimes offering temporary relief but often worsening baseline emotional regulation over time.
Evidence:
A 2018 study in Frontiers in Psychology linked high caffeine sensitivity to increased anxiety in those with pre-existing high neuroticism traits.
Another 2020 study in Journal of Affective Disorders found that frequent alcohol use correlated with greater emotional instability and neurotic traits.
5. Nutritional Deficiencies and Emotional Dysregulation
Certain deficiencies are directly linked to poor emotional and cognitive function:
Nutrient
Impact if Deficient
Omega-3s
Mood instability, impulsivity, higher neuroticism
Vitamin D
Low mood, anxiety, depression
Magnesium
Anxiety, tension, poor stress resilience
B Vitamins (esp. B6, B9, B12)
Fatigue, irritability, poor cognitive regulation
Iron
Low energy, brain fog, mood issues, especially in menstruating individuals
🧬 Personality Traits and Diet: Is There a Link?
While emotions are state-based, neuroticism is a trait—a stable personality characteristic. But traits are not fixed. Over time, they can shift, especially when brain chemistry and lifestyle factors change.
A 2021 study in Personality and Individual Differences showed:
Individuals who improved their diet (more whole foods, less processed) showed reductions in neuroticism and increased emotional stability over time.
This supports the idea that diet affects not just moods, but personality expression over time.
Influence
Impact on Emotion/Neuroticism
Gut health
Directly linked to serotonin and mood regulation
Inflammation
Associated with increased neurotic traits and depression
Sugar and refined carbs
Trigger emotional instability and crashes
Caffeine/alcohol
Can heighten anxiety and emotional dysregulation
Micronutrient status
Deficiencies in omega-3s, magnesium, B-vitamins and more affect emotional stability
Long-term diet
Can influence stable personality traits like neuroticism
