# GSTM1 — Glutathione S-transferase Mu 1
URL: https://genohealth.app/genes/gstm1
Category: Detoxification
Chromosome: 1p13.3
Key variants: GSTM1 deletion (null)
Last reviewed: 2026-04-25

## Summary
GSTM1 helps clear environmental toxins, oxidized fats and certain drugs via glutathione conjugation. About half of people carry a full deletion (null genotype) and produce zero enzyme from this gene — increasing oxidative-stress sensitivity.

## What it does
GSTM1 is one of several glutathione S-transferase enzymes that attach glutathione to electrophilic toxins (PAHs from smoke and grilled meat, heavy metals, oxidized lipids, certain chemotherapies) so they can be safely excreted. The null genotype means complete absence of GSTM1 enzyme — though related GSTs (GSTT1, GSTP1) provide partial backup.

## Why it matters
Null carriers may be more sensitive to air pollution, mold, smoking exposure, certain chemotherapies and pesticides, with measurably higher oxidative stress markers. GSTM1 null is also overrepresented in studies of bladder cancer, asthma severity in polluted cities, and chemotherapy toxicity.

## Variants
- GSTM1*0 (GSTM1 null (full deletion)) — risk allele n/a; Complete loss of enzyme function. (frequency: ≈50% of Europeans, 30-40% of Africans, 50%+ in some Asian populations.)

## Genotypes
- **Present (functional)** (~50%): Functional GSTM1 enzyme. → Standard healthy-living guidance; backup pathways are intact.
- **Null (deletion)** (~50%): No GSTM1 enzyme. Reliant on GSTT1, GSTP1 and other phase-II pathways. → Daily sulfur-rich foods, avoid smoking and minimize pollution exposure, consider sulforaphane and NAC under clinical guidance.

## Conditions
- **Asthma** — Increased severity in polluted environments: Null + high traffic-related air pollution → worse asthma control.
- **Bladder cancer** — Increased risk: Null carriers have ~20% higher bladder cancer risk, especially smokers.
- **Chemotherapy toxicity** — Modifies response: Null carriers may experience more side effects from certain platinum-based chemotherapies.
- **Mold sensitivity / chronic inflammatory response** — Possibly increased: Mechanistically plausible; clinical evidence emerging.

## Diet
Rationale: Sulfur-rich foods provide cysteine for glutathione synthesis. Cruciferous vegetables contain sulforaphane, which induces NRF2 and upregulates phase-II detox enzymes — partially compensating for missing GSTM1.
Prioritize: Cruciferous vegetables daily (broccoli, brussels sprouts, kale, cabbage); Garlic, onions, shallots; Eggs (sulfur-containing amino acids); Whey protein (rich in cysteine, glutathione precursor); Berries (antioxidant support); Green tea (EGCG induces phase-II)
Limit: Char-grilled and blackened meat (PAH burden); Smoking and second-hand smoke; Excessive alcohol (depletes glutathione)

## Lifestyle
- Use a HEPA air purifier in bedroom and primary living space.
- Avoid running/cycling on heavy-traffic roads at peak hours.
- Sauna 2-4x/week — supports heat-shock proteins and chemical excretion via sweat.
- Sleep 7-9 hours — glutathione synthesis is highest during sleep.
- Stay hydrated (urinary excretion of conjugated toxins).

## Supplements
- **Sulforaphane (broccoli sprout extract)** — 10-30 mg/day, form: Standardized for sulforaphane content (not just glucoraphanin). Most evidence-based phase-II inducer; especially valuable for GSTM1 null.
- **N-acetylcysteine (NAC)** — 600-1200 mg/day, form: NAC, ideally with food. Glutathione precursor; well-studied safety profile.
- **Liposomal glutathione** — 250-500 mg/day, form: Liposomal or S-acetyl glutathione. Direct glutathione delivery; useful when cysteine alone is insufficient.
- **Milk thistle (silymarin)** — 200-400 mg/day, form: Standardized to 80% silymarin. Hepatoprotective; supports phase-II conjugation.
- **Alpha-lipoic acid** — 300-600 mg/day, form: R-lipoic acid. Recycles glutathione and other antioxidants.

## Contraindications
- NAC can interact with nitroglycerin and some chemotherapies — check with oncologist if relevant.
- Sulforaphane / cruciferous vegetables in extremely high amounts may interfere with thyroid function in iodine-deficient individuals — ensure adequate iodine.

## FAQ
**Q: Is GSTM1 null dangerous?**
A: It is common (40-50% of people) and not dangerous on its own. It raises sensitivity to specific environmental exposures — pollution, smoking, certain drugs. Most null carriers live normal healthy lives, especially with a sulfur-rich diet.

**Q: Should I take NAC if I am GSTM1 null?**
A: NAC is well-studied and reasonable if you have high environmental exposure (city living, smoking history, post-COVID recovery). 600-1200 mg/day with food. Discuss with clinician if you take nitroglycerin.

**Q: What is the best supplement for GSTM1 null?**
A: Sulforaphane (broccoli sprout extract) has the strongest mechanistic evidence — it induces NRF2, which upregulates the entire phase-II detox system, partially compensating for missing GSTM1.

**Q: Do I need to avoid all toxins?**
A: Toxin-avoidance is impossible and obsessive avoidance is counterproductive. Focus on the high-impact items: don't smoke, minimize air pollution exposure, eat sulfur-rich vegetables daily, sleep well.

**Q: Does GSTM1 null affect alcohol tolerance?**
A: Alcohol depletes glutathione, so null carriers may experience more pronounced hangovers and oxidative load. Moderation matters more for null genotypes.

## Citations
- Bell et al., Carcinogenesis 1993 (PMID 8403199): Original characterization of GSTM1 null and bladder cancer risk.
- Romieu et al., Am J Respir Crit Care Med 2004 (PMID 14962820): GSTM1 null children showed worse asthma in polluted areas; antioxidant diet was protective.
- Egner et al., Cancer Prev Res 2014 (PMID 24913818): Sulforaphane-rich broccoli sprout drink accelerated airborne pollutant excretion in humans.

Disclaimer: Informational only — not medical advice.