Zinc

Zinc
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Chemical formula	Zn
Solubility	Zinc salts vary: zinc sulfate and zinc gluconate are water-soluble; zinc oxide is poorly soluble in water. Zinc bisglycinate (glycinate) has increased oral bioavailability (~43% higher than gluconate).
Bioavailability	Dependent on phytate intake as the overwhelming factor absorption. Animal protein (especially amino acid composition) enhances absorption; plant proteins inhibit it. A vegan needs twice as much zinc as an omnivore due to inhibitory phytate and lack of animal protein's beneficial effects. Egg yolk enhances zinc absorption.
Dietary sources	Oysters are by far the best source, followed by beef and cheese. Liver is relatively higher in copper than zinc, so pairing liver with oysters helps balance the zinc-to-copper ratio.
RDA (adults 19–50 y)	Men: 11 mg/day; Women: 8 mg/day. The RDA assumes vegetarians need ~50% more zinc due to phytate inhibition. Some computer modeling suggests very high phytate diets may require up to 100 mg to compensate.
Upper limit	40 mg/day (Institute of Medicine). Chronic high-dose zinc can induce copper deficiency by increasing metallothionein, which sequesters copper. Dietary zinc-to-copper ratio should be at least 2:1 but no more than 15:1.

Introduction

Zinc is one of the two most prevalent mineral deficiencies on Earth (alongside iron), and on a population level, deficiency is extremely correlated with the plant-to-animal ratio of the diet. Anywhere where there's endemic iron or zinc deficiency, it's in populations that mostly eat plants. Unlike many nutrients where status markers are controversial, zinc has been exceptionally well-studied through depletion-repletion trials, particularly Janet King's elegant experiments that remain the gold standard for understanding zinc deficiency progression.

Structure/Chemical properties

Zinc (Zn) is a transition metal, atomic number 30. It exists as a divalent cation (Zn²⁺) in biological systems.

Key chemical behaviors:

Forms coordination complexes with proteins - zinc is a structural component of over 300 enzymes

The positive charge of zinc can form coordination bonds with amino acid side chains (histidine, cysteine, aspartate, glutamate)

Different salt forms have different properties: sulfate and gluconate are water-soluble; oxide is poorly soluble

Function/Mechanism of Action

Carbonic anhydrase cofactor:

"Zinc is an essential component of carbonic anhydrase enzyme. And I think that in nerve endings and sensory organs, carbonic anhydrase is important for regulating sensitivity. And zinc deficiency has been associated closely with the loss of taste." - Ray Peat

This explains why loss of smell and taste (common in COVID and colds) relates to zinc: stress increases metallothionein protein, which binds essential metals like zinc. The loss of zinc then impairs carbonic anhydrase function in sensory organs.

Acid-base regulation:

Chris Masterjohn found that fixing a zinc deficiency allowed him to stop taking bicarbonate for exercise-induced acidosis, zinc is a cofactor for carbonic anhydrase, which regulates pH levels.

Testosterone and thyroid support:

• Zinc supplementation (50–70 mg/day for 4 weeks) prevented exercise-induced decline in both thyroid hormones (T3, T4) and testosterone in athletes
• Marginally zinc-deficient elderly men given zinc for 6 months doubled serum testosterone (8.3 → 16 nmol/L)
• Subjects with normal testosterone have significantly higher zinc levels compared to low-testosterone groups

Immune function:

Zinc deficiency causes immune dysfunction, but so does zinc excess—the mechanisms are different. Zinc is needed for immune function, but excess zinc induces copper deficiency, which also impairs immunity.

Vitamin A activation:

Low ATP means less zinc absorption → less zinc means impaired acetaldehyde dehydrogenase (zinc-dependent) → impaired vitamin A activation

Medical uses/Effects

Deficiency symptoms (from Janet King's depletion-repletion studies: only 5% whole body zinc loss needed):

• Sore throat
• Diarrhea
• Glucose intolerance
• Dry skin, severe acne
• Eczema, seborrheic dermatitis
• Growth impairment in children
• Hair stops growing (adults)
• Lean mass loss / difficulty building muscle
• Smell and taste dysfunction (30% whole body deficit)

Therapeutic applications:

• COVID protocol: Lozenges for upper respiratory tract; capsules for systemic supply
• Skin conditions: Eczema, dermatitis, acne
• Testosterone support in deficient individuals
• Exercise recovery: Prevents thyroid/testosterone decline from training

Side/Adverse effects

Excess zinc:

• Copper deficiency: the primary long-term risk; zinc induces metallothionein which sequesters copper
  • MT binds copper with high affinity (higher than zinc) and traps it inside the cell.
• Immune dysfunction: well-demonstrated consequence of excessive supplementation
• Insomnia: reported adverse effect; if occurring, reduce dose or change timing
• Nausea. common with high doses, especially on empty stomach

"Zinc isn't directly an oxidant, but when it's used as a chemical supplement it can cause problems that it wouldn't in the form of foods." - Ray Peat

Inflammation effect:

Inflammation decreases plasma zinc by increasing tissue uptake. SIBO and other inflammatory conditions can cause plasma zinc to keep dropping despite supplementation, this reflects increased demand, not toxicity.

Dosing

General supplementation:

• Start: 7–15 mg/day
• Deficiency protocol: 10 mg three to four times daily, away from phytate foods
• Athletes (thyroid/testosterone support): 50–70 mg/day for 4 weeks (study dose)

Children off growth curve:

Give 5 mg zinc, if they shoot back onto the growth curve, they had zinc deficiency. "That's clinical malpractice not to try this."

Timing:

• Ideal: 3 hours after eating, 1 hour before next meal
• Minimum: 40 minutes before/after meals
• Alternative: Take with a phytate-free (carnivore-style) meal
• Coffee inhibits zinc absorption - separate them

Lozenges vs. capsules:

• Lozenges: Flood nose/throat locally (acute illness)
• Capsules: Systemic supply

Form switching if not absorbing:

If plasma zinc stays low despite supplementation, try different forms—gluconate → acetate → citrate → glycinate → methionine. Different forms work for different people.