The Public Herbarium

close up of whole Black pepper (Piper nigrum)

Immune Resilience, Respiratory Protection, and Warming Strategies at the Molecular Level

This comprehensive guide explores winter immunology, respiratory physiology in cold conditions, and the pharmacological mechanisms of warming and immune-supporting herbs for New Zealand’s winter season.

Table of Contents

  1. Winter Physiology and Immune Challenge
  2. Vitamin D Deficiency: The Winter Deficit
  3. Cold-Weather Respiratory Stress
  4. Garlic: Allicin and Antimicrobial Power
  5. Astragalus: Deep Immune Modulation
  6. Reishi Mushroom: Adaptogenic Immune Support
  7. Warming Herbs: Circulation and Thermogenesis
  8. Formulation Strategies for Winter
  9. References

Winter Physiology and Immune Challenge

Seasonal Immune Variations

The human immune system doesn’t function identically year-round. Research demonstrates measurable seasonal fluctuations:

UK Biobank Study (Dopico et al., 2021):
Analysis of 329,261 participants revealed:

Pro-inflammatory Cytokines (Killestein et al., 2002):
Study of healthy individuals showed:

Why this matters: Winter presents a paradox—we need stronger immunity against pathogens, yet some immune parameters are elevated (neutrophils) while others are reduced (lymphocytes). This creates immune imbalance requiring support.

Photoperiod and Melatonin

The Light-Darkness Cycle:

Summer vs Winter (Wellington, NZ ~41°S):

Neurohormonal Pathway:

  1. Light enters eyes, signals suprachiasmatic nucleus (SCN) in hypothalamus
  2. SCN = body’s master clock, synchronises circadian rhythms
  3. Darkness: SCN signals pineal gland → melatonin secretion
  4. Light: Melatonin secretion suppressed

Winter = longer nights = prolonged melatonin secretion

Melatonin’s Immune Effects:

Immuno-enhancing (appropriate levels):

Potential problems in winter:

Herbal implications: While we can’t change photoperiod, understanding this helps explain winter fatigue and the importance of:

Temperature Fluctuations and HPA Axis

Cold Exposure Stress:

When exposed to cold, the body activates the hypothalamic-pituitary-adrenal (HPA) axis:

  1. Hypothalamus releases CRH (corticotropin-releasing hormone)
  2. Pituitary releases ACTH (adrenocorticotropic hormone)
  3. Adrenal glands release cortisol

Cortisol’s Immune Effects:

Acute (short-term, beneficial):

Chronic (long-term, problematic):

Winter reality: Repeated cold exposures (going outside, poorly heated homes, temperature fluctuations) create chronic low-level HPA activation.

Herbal support: Adaptogens (astragalus, reishi) help regulate HPA axis, preventing excessive or prolonged cortisol elevation.

Vitamin D Deficiency: The Winter Deficit

The Biochemistry of Deficiency

Vitamin D Synthesis:

Summer:

  1. UVB radiation (290-315 nm) hits skin
  2. Converts 7-dehydrocholesterol → previtamin D₃
  3. Body heat isomerises previtamin D₃ → vitamin D₃ (cholecalciferol)
  4. Liver converts D₃ → 25-hydroxyvitamin D [25(OH)D] (storage form)
  5. Kidneys convert 25(OH)D → 1,25-dihydroxyvitamin D [1,25(OH)₂D] (active form, calcitriol)

Winter problem: UVB intensity insufficient for synthesis at latitudes >37° from November-February (Southern Hemisphere).

New Zealand specifics:

Result: 40% of New Zealand adults have insufficient vitamin D (<50 nmol/L) in winter.

Vitamin D and Immune Function

Mechanisms:

1. Antimicrobial Peptide Production:

Vitamin D enhances production of cathelicidins and defensins:

2. Macrophage and Neutrophil Enhancement:

3. Modulation of Adaptive Immunity:

Clinical Evidence:

Martineau et al. (2017) meta-analysis:

Optimal levels:

Herbal context: Herbs cannot replace vitamin D. Ensure adequate intake (600-1000 IU daily supplementation in winter, or more if deficient). Herbs work synergistically with adequate vitamin D status.

Cold-Weather Respiratory Stress

Airway Physiology Under Cold Stress

Nasal Passage Effects:

Warm weather (20-25°C inhaled air):

Cold weather (0-5°C inhaled air):

Result: Impaired mucociliary clearance = pathogens stay in contact with epithelium longer = increased infection risk.

Lower Airway Effects:

Herbal support targets:

  1. Demulcents: Soothe irritated, dry airways (marshmallow, licorice)
  2. Expectorants: Help clear thickened mucus (thyme, elecampane)
  3. Antimicrobials: Reduce pathogen load (garlic, thyme)
  4. Warming circulatory stimulants: Increase blood flow to tissues (ginger, cinnamon)

Indoor Air Quality

Low Humidity:

Heating systems dry air:

Stagnant Air and Viral Transmission:

Herbal strategy: Internal demulcents + external humidification + regular ventilation.

Garlic: Allicin and Antimicrobial Power

Garlic (Allium sativum) head and cloves
Garlic (Allium sativum)

Phytochemistry

Intact Garlic Clove:

Enzymatic Reaction:

Alliin + Alliinase → Allylsulfenic acid (2 molecules) → Spontaneous condensation (H₂O) → ALLICIN (diallyl thiosulfinate)

Allicin formation:

Degradation products still bioactive:

Antimicrobial Mechanisms

1. Thiol Modification (Primary Mechanism):

Allicin is a reactive sulfur species (RSS)—it reacts rapidly with free thiols (-SH groups):

Thiol-disulfide exchange:
Protein-SH + Allicin → Protein-S-S-allyl + Allyl-SH

Target proteins in bacteria:

Result: Multiple essential enzymes inactivated simultaneously = broad-spectrum antimicrobial activity.

2. DNA Gyrase Inhibition:

Recent research (Reiter et al., 2020) identified a novel mechanism:

Why this matters: DNA gyrase is a clinically important antibiotic target. Allicin’s action suggests potential for:

3. Membrane Disruption:

While less studied than thiol modification, allicin can:

Antimicrobial Spectrum

Confirmed activity against:

Gram-positive bacteria:

Gram-negative bacteria:

Minimum Inhibitory Concentrations (MICs):

Comparison: These MICs are higher than many antibiotics, BUT:

Viruses:

Fungi:

Volatile Antimicrobial Action

Unique property: Allicin is volatile—can work as vapour.

Reiter et al. (2017) study:

Clinical implications:

Clinical Evidence

Josling (2001) RCT:

Mechanism (proposed):

Pharmacokinetics and Bioavailability

Absorption:

Distribution:

Metabolism:

Excretion:

Half-life:

Practical Applications

Fresh Garlic (Most Potent):

Optimal preparation:

  1. Peel and crush/chop cloves
  2. Wait 10-15 minutes (allows allicin formation)
  3. Consume raw OR add to food at end of cooking (minimal heat exposure)

Dosing:

Palatability strategies:

Aged Garlic Extract:

Garlic Supplements:

Astragalus: Deep Immune Modulation

astragalus (Astragalus membranaceus) slices
Astragalus (Astragalus membranaceus)

Phytochemistry

Astragalus membranaceus root contains multiple bioactive constituents:

1. Polysaccharides (Astragalus Polysaccharides, APS):

2. Saponins (Astragalosides):

3. Flavonoids:

4. Others:

Note: Polysaccharides are considered the primary immune-active fraction.

Immunomodulatory Mechanisms

Key concept: Astragalus is an immune modulator, not just a stimulant. It enhances appropriate immune responses without causing hyper-activation.

1. Macrophage Activation:

TLR4-Mediated Pathway:

Research (Shao et al., 2004; Liu et al., 2017) shows:

  1. MyD88 adapter protein recruited 2. TRAF6 (TNF receptor-associated factor 6) activated 3. NF-κB (nuclear factor kappa B) and MAPK pathways activated 4. Gene transcription for cytokines, NO production

Functional outcomes:

M1/M2 Polarisation:

Macrophages exist in different phenotypes:

APS promotes M1 polarisation (Bamodu et al., 2019):

2. T Cell Modulation:

CD4+ T Helper Cells:

APS affects differentiation and function:

CD8+ Cytotoxic T Cells:

Regulatory T Cells (Tregs):

3. Natural Killer (NK) Cell Enhancement:

4. Dendritic Cell Maturation:

5. B Cell and Antibody Production:

B Cell Activation:

Antibody Production:

Clinical and Experimental Evidence

Immune Cell Studies:

Goel et al. (2005):

Reduced Respiratory Infections:

Multiple studies show:

Vaccine Response Enhancement:

Mechanism Summary:

APS works through multiple pathways:

Why this matters for winter:

Dosing and Preparation

Decoction (Traditional, Preferred):

Method:

  1. Simmer 3-5 root slices (about 10-15g) in 3-4 cups water
  2. Simmer 20-30 minutes (longer = stronger extraction)
  3. Strain, drink 1-2 cups daily
  4. Can re-simmer same roots once more (weaker but still active)

Soup Ingredient:

Tincture:

Powder/Capsules:

Timing:

Reishi Mushroom: Adaptogenic Immune Support

Reishi Mushroom (Ganoderma lucidum) fruiting body
Reishi Mushroom (Ganoderma lucidum)

Phytochemistry

Ganoderma lucidum (Reishi, Lingzhi) fruiting body contains:

1. Polysaccharides (Beta-Glucans):

Structure:

Concentration: 10-50% depending on preparation

2. Triterpenes (Ganoderic Acids):

Main triterpenes:

3. Proteins and Peptides:

Note: Polysaccharides and triterpenes have different, complementary actions—best extraction includes both (hot water + alcohol).

Immunomodulatory Mechanisms

1. Beta-Glucan Receptor Activation:

Beta-glucans from Reishi interact with multiple immune cell receptors:

Dectin-1:

Complement Receptor 3 (CR3):

Toll-like Receptors (TLR2, TLR4):

2. Natural Killer Cell Enhancement:

Multiple studies show Reishi increases:

Mechanism:

3. T Cell and B Cell Modulation:

T cells:

B cells:

4. Macrophage Activation:

Similar to astragalus:

Triterpene Actions (Distinct from Polysaccharides)

Anti-inflammatory:

Ganoderic acids:

Hepatoprotective:

Adaptogenic/Stress-Modulating:

Sleep and Nervous System Effects

Traditional use: Reishi called “Mushroom of Immortality,” also “Spiritual Potency”—used for calming mind, improving sleep.

Modern research:

Winter relevance:

Clinical Evidence

Immune Enhancement in Athletes:

Quality of Life in Various Conditions:

Note: Most studies use standardised extracts (polysaccharide and triterpene content specified). Whole mushroom preparations less studied but traditionally used.

Dosing and Preparation

Decoction (Traditional):

Problem: Reishi is woody, requires long extraction

Method:

  1. Simmer dried slices (10-15g) in 3-4 cups water
  2. Simmer 1-2 hours (not minutes—very woody)
  3. Strain (bitter taste)
  4. Add honey to improve palatability
  5. Drink 1-2 cups daily

Dual Extraction (Optimal):

Water extraction:

Alcohol extraction:

Combine water and alcohol extracts = full-spectrum preparation

Powder:

Extracts/Tinctures:

Timing:

Synergy:

Warming Herbs: Circulation and Thermogenesis

Ginger, Cinnamon, Rosemary: Shared and Distinct Actions

Shared Mechanisms:

1. Circulatory Stimulation:

All three increase peripheral blood flow through:

2. Anti-inflammatory:

All contain compounds that reduce inflammation:

3. Antimicrobial:

All have compounds active against bacteria, viruses:

Ginger (Zingiber officinale)

Ginger (Zingiber officinale) root
Ginger (Zingiber officinale)

Active Compounds:

Mechanisms:

1. TRPV1 Receptor Activation:

2. COX-2 and 5-LOX Dual Inhibition:

Unlike NSAIDs (which typically inhibit COX only):

3. NF-κB Suppression:

4. Antiplatelet Activity:

Clinical Evidence:

Cinnamon (Cinnamomum verum/cassia)

Cinnamon (Cinnamomum spp.) dried bark and powdered dried bark
Cinnamon (Cinnamomum spp.)

Active Compounds:

Mechanisms:

1. Thermogenic Effect:

2. Insulin Sensitivity:

3. Antimicrobial:

4. Anti-inflammatory:

Clinical Evidence:

Rosemary (Rosmarinus officinalis)

Rosemary (Rosmarinus officinalis) in flower
Rosemary (Rosmarinus officinalis)

Active Compounds:

Mechanisms:

1. Cholinergic Effects:

2. Circulatory Stimulation:

3. 1,8-Cineole (Eucalyptol):

4. Antioxidant:

Clinical Evidence:

Synergistic Combinations

Ginger + Cinnamon:

Rosemary + Thyme:

All three combined:

Formulation Strategies for Winter

Principles of Winter Formulation

1. Synergy Over Single Herbs:

Winter challenges are multifaceted:

Single herb rarely addresses all. Formulas provide:

2. Include Multiple Immune Mechanisms:

3. Balance Stimulation and Modulation:

Avoid: Pure stimulation (echinacea continuously)

Prefer: Modulators (astragalus, reishi) as base

4. Address Individual Needs:

Winter Formula Examples

Formula 1: Long-Term Immune Tonic (Prevention)

Purpose: Daily use throughout winter to build immune resilience

Composition:

Rationale:

Preparation:

Decoction method:

  1. Combine 2 tablespoons mixed herb blend in 4 cups cold water
  2. Bring to boil, reduce heat
  3. Simmer roots/bark (astragalus, reishi, ginger, cinnamon, liquorice) 20-30 minutes
  4. Strain, drink 1-2 cups daily

Timing: Start 4-6 weeks before peak winter, continue through cold season

Cost (NZ): Approximately $1-2 per day using bulk herbs

Formula 2: Acute Respiratory Support (Active Illness)

Purpose: Use when cold, flu, or respiratory infection present

Composition:

Rationale:

Preparation:

Hot infusion (thyme, liquorice):

  1. Simmer ginger 10 minutes in 3 cups water
  2. Remove from heat
  3. Add thyme, licorice
  4. Steep covered 10-15 minutes
  5. Strain

Fresh garlic:

Elderberry syrup:

Dosing: 3-4 cups tea daily plus garlic and elderberry while symptomatic

Formula 3: Warming Digestive/Immune Broth

Purpose: Nourishing food-as-medicine, gentle immune support

Composition:

Method:

  1. Combine all ingredients in large pot
  2. Simmer 2-4 hours (low heat)
  3. Strain, discard solids
  4. Season with miso/salt

Use:

Benefits:

References

Seasonal Immunology & Vitamin D

Dopico, X. C., et al. (2021). Widespread seasonal gene expression reveals annual differences in human immunity and physiology. Nature Communications, 12(1), 997.

Killestein, J., et al. (2002). Circannual rhythm of serum levels of the soluble IL-2 receptor, IL-6 and TNF-alpha in multiple sclerosis. Acta Neurologica Scandinavica, 106(5), 268-272.

Martineau, A. R., et al. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: Systematic review and meta-analysis of individual participant data. BMJ, 356, i6583.

Cantorna, M. T. (2010). Mechanisms underlying the effect of vitamin D on the immune system. Proceedings of the Nutrition Society, 69(3), 286-289.

Garlic & Allicin

Ankri, S., & Mirelman, D. (1999). Antimicrobial properties of allicin from garlic. Microbes and Infection, 1(2), 125-129.

Reiter, J., et al. (2017). Diallylthiosulfinate (Allicin), a volatile antimicrobial from garlic (Allium sativum), kills human lung pathogenic bacteria, including MDR strains, as a vapour. Molecules, 22(10), 1711.

Reiter, J., et al. (2020). Allicin, a natural antimicrobial defence substance from garlic, inhibits DNA gyrase activity in bacteria. International Journal of Medical Microbiology, 310(1), 151359.

Josling, P. (2001). Preventing the common cold with a garlic supplement: A double-blind, placebo-controlled survey. Advances in Therapy, 18(4), 189-193.

Astragalus

Shao, B. M., et al. (2004). A study on the immune receptors for polysaccharides from the roots of Astragalus membranaceus, a Chinese medicinal herb. Biochemical and Biophysical Research Communications, 320(4), 1103-1111.

Liu, Q. Y., et al. (2017). Astragalus polysaccharides exerts immunomodulatory effects via TLR4-mediated MyD88-dependent signaling pathway in vitro and in vivo. Scientific Reports, 7, 44822.

Bamodu, O. A., et al. (2019). Astragalus polysaccharides (PG2) enhances the M1 polarization of macrophages, functional maturation of dendritic cells, and T cell-mediated anticancer immune responses in patients with lung cancer. Nutrients, 11(10), 2264.

Reishi

Wachtel-Galor, S., et al. (2011). Ganoderma lucidum (Lingzhi or Reishi): A medicinal mushroom. In I. F. F. Benzie & S. Wachtel-Galor (Eds.), Herbal Medicine: Biomolecular and Clinical Aspects (2nd ed.). CRC Press.

General References

Bone, K., & Mills, S. (2013). Principles and practice of phytotherapy: Modern herbal medicine (2nd ed.). Churchill Livingstone.

Rongoā Māori Disclaimer: This guide does not represent rongoā Māori preparation methods or traditional Māori medicine-making. Rongoā Māori is a complete healing system with its own protocols, karakia (prayers), and cultural practices that cannot be separated from te ao Māori (the Māori worldview). For rongoā Māori knowledge and treatment, please consult qualified rongoā practitioners through Te Paepae Motuhake or other appropriate Māori health services.

Medical Disclaimer: This guide is for educational purposes only and is not medical advice. Always consult qualified healthcare practitioners before using herbal remedies, especially if pregnant, nursing, taking medications, or having medical conditions. The mechanisms described represent current scientific understanding and may be updated as research progresses. Individual responses to herbs vary. Seek immediate medical attention for serious symptoms, high fevers, or concerning health changes.

Note on Pricing: All prices mentioned in this guide are approximate and based on New Zealand suppliers as of December 2025. Prices vary by supplier, season, and market conditions. We recommend checking current prices with your local suppliers.

The Public Herbarium is built on a foundation of scientific integrity, transparency, and care. Research sources are referenced throughout the site wherever possible. Content creation is assisted by AI tools and carefully reviewed for accuracy.