# Body Chemistry and Mental Health

- Link: https://psychologyforeveryone.com/chapter/21-body-chemistry-and-mental-health/
- Published: 2026-10-24T07:45:03+00:00
- Author: myadvisorfriend@gmail.com

## 21.1 Overview

Mental health is deeply connected to physical biochemistry. Hormones,
 neurotransmitters,
vitamins, minerals, and metabolic processes all influence brain function and emotional
wellbeing.

## 21.2 Thyroid function

Thyroid hormones (T3, T4) regulate metabolism, energy, temperature,
 and growth.
They are produced by the thyroid gland in the neck and controlled by TSH from the
pituitary.

#### Hypothyroidism (low thyroid)

Symptoms: fatigue, depression, weight gain, cold intolerance, brain
 fog, dry skin,
constipation. Mental-health impact: can mimic or worsen depression and cognitive
slowing. Testing: TSH, Free T3, Free T4. Treatment: thyroid hormone replacement 
under a doctor.

#### Hyperthyroidism (high⏎  thyroid)

Symptoms: anxiety, irritability, weight loss, heat intolerance, rapid
 heartbeat,
tremors. Mental-health impact: can mimic anxiety disorders, panic attacks, mania.
Treatment: anti-thyroid medicines, radioactive iodine, or surgery as a physician
decides.

Important: thyroid testing should be part of mental-health
 assessment.

## 21.3 Blood sugar

Insulin allows cells to use glucose. Glucose is the primary fuel for
 brain cells.
Stability is critical for mental function.

Hypoglycaemia: irritability, anxiety, confusion, shakiness, mood
 swings, brain 
fog. Can trigger anxiety, panic, irritability, depression. Prevention: regular meals,
balanced nutrition, protein with carbohydrates.

Hyperglycaemia / diabetes: fatigue, increased thirst, frequent
 urination, blurred
vision. Increased risk of depression, cognitive decline, anxiety. Management: diet,
exercise, medication, monitoring.

Sugar crashes can cause irritability and anxiety. Stable blood sugar
 supports stable
mood. Complex carbohydrates provide sustained energy. Protein and healthy fats slow
glucose absorption.

## 21.4 Vitamins

#### Vitamin D

Hormone-like vitamin supporting brain and immune function. Deficiency
 linked to
depression, SAD, and cognitive decline. Sources: sunlight, fatty fish, fortified
foods, supplements. Testing: 25-hydroxy vitamin D. An often-cited range around 30–
50 ng/mL (some experts 40–60). Confirm with a clinician for your country and lab.

#### B vitamins

 * > B12: nerve function, DNA, red cells. Deficiency: depression, anxiety,
   >  memory
   > problems, fatigue, neuropathy. Sources: animal products, fortified foods. At
   > risk: vegans, elderly, people with digestive issues.
 * > B9 (folate): DNA and neurotransmitter production. Deficiency:
   >  depression, 
   > cognitive impairment, anaemia. Sources: leafy greens, legumes, fortified grains.
   > Important in pregnancy.
 * > B6: synthesis of serotonin, dopamine, GABA. Deficiency: depression,
   >  confusion,
   > weakened immunity. Sources: fish, poultry, potatoes, bananas.
 * > B1, B2, B3, B5: energy metabolism and brain function. Deficiencies
   >  can cause
   > fatigue, depression, cognitive problems.

#### Vitamins C and E

Vitamin C: antioxidant, neurotransmitter synthesis, immune support.
 Deficiency:
fatigue, depression, weakened immunity (scurvy when severe). Sources: citrus, berries,
peppers, broccoli.

Vitamin E: antioxidant, protects membranes. Deficiency: neurological
 problems, 
muscle weakness. Sources: nuts, seeds, vegetable oils.

## 21.5 Minerals

 * > Magnesium: 300+ reactions, nerve function, muscle relaxation.
   >  Deficiency linked
   > to anxiety, depression, insomnia, migraines, cramps. Sources: greens, nuts,
   > seeds, whole grains, dark chocolate. Forms: glycinate (calming), citrate, oxide(
   > less absorbable).
 * > Zinc: immune and neurotransmitter function. Deficiency linked to
   >  depression,
   > immunity, hair loss, taste changes. Sources: meat, shellfish, legumes, seeds,
   > nuts.
 * > Iron: oxygen transport, energy, neurotransmitter synthesis. Anaemia:
   >  fatigue,
   > depression, brain fog, pale skin, shortness of breath. Excess can be toxic.
   > Get tested before supplementing.
 * > Selenium: antioxidant and thyroid function. Deficiency linked to
   >  depression,
   > anxiety, thyroid problems. Sources: Brazil nuts, seafood, meat.
 * > Calcium: bone, nerve, muscle. Imbalance can affect mood, anxiety,
   >  muscle function.
   > Sources: dairy, leafy greens, fortified foods.

## 21.6 Amino acids and omega-3

 * Tryptophan → serotonin. Sources: turkey, chicken, eggs, cheese, nuts,
    seeds.
   Supports mood, sleep, appetite.
 * Tyrosine → dopamine and noradrenaline. Sources: meat, fish, eggs,
    dairy, soy,
   nuts. Supports motivation, focus, alertness, mood.
 * Glutamine → GABA. Sources: meat, fish, eggs, dairy, legumes. Supports
    calm, 
   relaxation, sleep.

Omega-3: EPA (Eicosapentaenoic Acid) (anti-inflammatory, mood),

DHA (Docosahexaenoic Acid) (brain structure, cognition),

ALA (Alpha-Linolenic Acid) (plant; converts poorly).

Benefits named: less brain inflammation, membrane fluidity, possible
 help in depression,
anxiety, Attention-Deficit/Hyperactivity Disorder (ADHD).

Best food sources of EPA/DHA: salmon, mackerel, sardines,
 herring.

Plant ALA: flax, chia, walnuts. Algae oil is a vegan EPA/DHA option.
 Doses in the
text are often-cited ranges — confirm with a clinician.

## 21.7 Gut–brain axis and⏎  inflammation

The gut contains 100+ million nerve cells (enteric nervous system),
 produces much
of the body’s serotonin, and connects to the brain via the vagus nerve. Gut bacteria
influence mood, cognition, and behaviour.

Probiotics may improve anxiety and depression in some people.
 Prebiotics (fibre)
support gut health. Dysbiosis is linked to depression, anxiety, and autism in research.
Intestinal permeability may contribute to inflammation and mental-health issues.

Support: fermented foods (yogurt, kefir, sauerkraut, kimchi);
 high-fibre diet; 
limit processed foods and sugar; consider probiotics after advice.

Chronic low-grade inflammation is linked to depression. Markers (CRP,
 IL-6, TNF-
alpha) are often elevated. Inflammation can affect neurotransmitter function and
brain plasticity. Anti-inflammatory approaches: omega-3, antioxidant-rich diet, 
exercise, stress reduction, sleep, limiting processed food and sugar.

![Figure 21.1 The gut–brain axis. (Illustration created with AI tools.)](/wp-content/
uploads/pfe-book/image50.webp)

**Figure 21.1** _The gut–brain axis._

## 21.8 Practical recommendations

Get comprehensive blood work: thyroid panel (TSH, Free T3, Free T4);
 vitamin D,
B12, folate; iron studies (ferritin, iron, TIBC); magnesium (RBC magnesium more 
accurate); blood sugar (fasting glucose, HbA1c); inflammatory markers if indicated.

Eat a balanced diet: whole foods, vegetables, fruits; quality protein
 at each meal;
healthy fats; complex carbohydrates; limit processed foods and sugar.

Consider supplements only after testing and consultation: vitamin D3
 if deficient;
B-complex especially B12 and folate; magnesium glycinate; omega-3; probiotics.

Support gut health; manage stress; regular exercise; adequate sleep;
 limit alcohol
and caffeine.

## 21.9⏎  Physical conditions that can look like mental illness

A good doctor always considers whether a body problem may be
 involved. Some examples:

 * Thyroid disease, anaemia, or low vitamin B12 or D can cause tiredness
    and low
   mood.
 * Infections, especially in older adults, can cause sudden
    confusion.
 * Brain tumors, head injuries, and strokes can change personality or
    mood.
 * Some medicines, including certain steroids and blood pressure drugs,
    can affect
   mood.
 * Alcohol, cannabis, stimulants, and other drugs can cause or worsen
    anxiety, 
   depression, and psychosis.
 * Sleep apnea can cause tiredness, poor concentration, and
    depression.

Never try to diagnose yourself from a list. Instead, bring physical
 and mental 
symptoms together when you see a doctor.

## 21.10 One companion verse

SHLOKA / VERSE

**Sanskrit Text:**

आयुःसत्त्वबलारोग्यसुखप्रीतिविवर्धनाः ।

रस्याः स्निग्धाः स्थिरा हृद्या आहाराः सात्त्विकप्रियाः ॥

**Pronunciation:**

_ayuh-sattva-balarogya-sukha-priti-vivardhanah |_

_rasyah snigdhah sthira hrdyah aharah sattvika-priyah ||_

**Translation:**

Foods that increase life, clarity, strength, health, happiness, and
 love—which 
are juicy, naturally oily, stable, and agreeable—are dear to the sattvic mind.

**Practical Meaning for Daily Health:**

This classical verse perfectly describes the modern nutritional
 psychology we just
explored. Notice that it specifically praises foods that are _Snigdha_ (naturally
oily or rich in healthy fats, like the Omega-3s) because good fats are part of a
diet that supports the brain. A calm, steady (_sattvic_) mind requires stable, nourishing
physical food.

However, there is a hard medical boundary. A healthy plate of food is
 the foundation
that can support your nervous system through a difficult week. But food is not a
magical cure for a broken biological engine. A good diet cannot replace thyroxine
if your thyroid is failing, it cannot replace insulin if you have diabetes, and 
it absolutely cannot replace an antidepressant when a licensed doctor indicates 
your brain needs one.

_Reference — Bhagavad Gita 17.8_

### Reflection activity

 1. Have you had recent blood work? What were your levels?
 2. How is your diet supporting your brain chemistry?
 3. Are you getting enough sunlight for vitamin D?
 4. How is your gut health? Any digestive issues?
 5. What one change could you make this week to support your body
     chemistry?