GSTM1 — Glutathione S-transferase Mu 1

Category: Detoxification · Chromosome: 1p13.3 · Key variants: GSTM1 deletion (null) · Also known as: detox gene

This gene powers one of your body's natural cleanup crews — the enzymes that neutralize pollution, smoke, and everyday toxins. About half of people carry a blank copy with no cleanup enzyme at all, making them more sensitive to air quality, grilled meat, and oxidative stress.

Last reviewed: 2026-04-25

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What GSTM1 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.

Key variants

rsID	Alias	Risk allele	Effect	Frequency
`GSTM1*0`	GSTM1 null (full deletion)	—	Complete loss of enzyme function.	≈50% of Europeans, 30-40% of Africans, 50%+ in some Asian populations.

Common genotypes & what to do

Genotype	Prevalence	What it means	What to do
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.

Associated conditions

Condition	Relationship	Detail
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 guidance for GSTM1

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.

Foods to 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)

Foods to 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 — dose, form & timing

Supplement	Typical dose	Form	Notes
Sulforaphane (broccoli sprout extract)	10-30 mg/day	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	NAC, ideally with food	Glutathione precursor; well-studied safety profile.
Liposomal glutathione	250-500 mg/day	Liposomal or S-acetyl glutathione	Direct glutathione delivery; useful when cysteine alone is insufficient.
Milk thistle (silymarin)	200-400 mg/day	Standardized to 80% silymarin	Hepatoprotective; supports phase-II conjugation.
Alpha-lipoic acid	300-600 mg/day	R-lipoic acid	Recycles glutathione and other antioxidants.

Always introduce one supplement at a time and monitor response. Doses are general references, not prescriptions.

Contraindications & cautions

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.

Frequently asked questions about GSTM1

Is GSTM1 null dangerous?

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.

Should I take NAC if I am GSTM1 null?

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.

What is the best supplement for GSTM1 null?

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.

Do I need to avoid all toxins?

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.

Does GSTM1 null affect alcohol tolerance?

Alcohol depletes glutathione, so null carriers may experience more pronounced hangovers and oxidative load. Moderation matters more for null genotypes.

Citations & further reading

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.