A cabbage-family compound whose most reliable effects are a shift in how estrogen is broken down and strong activation of a liver enzyme system that clears a defined set of medications. Benefit evidence in precancerous lesions is thin and unconfirmed; longevity claims rest on cell and mouse work. The drug-clearance effect is the best-documented human finding, and a liability. (Full Review)

Protocol

Standard dose

200–400 mg/day

Taken orally. Minimum effective dose 300 mg/day; no further gain above 400 mg/day.

Timing

With food

Stomach acid drives the condensation that produces the absorbable metabolite; an empty stomach or acid suppression reduces yield.

Split versus single dose

Once or twice daily

Twice-daily dosing suits the short metabolite exposure; single daily dosing achieved the full metabolic shift.

Time to effect

Cervical lesions

12 weeks

Assessment point for histologic regression in the cervical lesion trials.

Airway and vulvar lesions

3–6 months

Assessment point in the airway and vulvar protocols.

Estrogen metabolite shift

Within 1 month

Measurable within one month and plateaus there.

Benefits

Medium: Regression of Precancerous Cervical Lesions

Low: Symptom and Lesion Improvement in Vulvar Intraepithelial Neoplasia; Remission of Recurrent Respiratory Papillomatosis; Reduction in Lupus Disease Activity; Improvement in Benign Prostatic Hyperplasia Symptoms

Speculative: Shift of Estrogen Metabolism Toward the 2-Hydroxy Pathway; Induction of Phase II Detoxification Enzymes; Clearance of Senescent Cells; Reactivation of the PTEN Tumor Suppressor; Extension of Lifespan in an Autoimmune Mouse Model

Contraindications

Pregnant or breastfeeding women

Anyone taking tamoxifen

Hormone-receptor-positive cancer under active endocrine treatment

Clozapine, olanzapine, theophylline or tizanidine without therapeutic drug monitoring

Untreated hypothyroidism or thyroid-stimulating hormone above 4.0 mIU/L

Active liver disease or transaminases above twice the upper limit of normal

Diagnosed bleeding disorder, or within 10 days of planned surgery

Children and adolescents outside a supervised trial protocol

Key Interactions

Warfarin and direct oral anticoagulants (apixaban, rivaroxaban)

Estrogen therapy and combined oral contraceptives (estradiol, ethinylestradiol)

Acid-suppressing medication (omeprazole, famotidine)

Sulforaphane and broccoli sprout extracts (caution, additive)

Green tea catechins (caution, additive)

Fish oil, vitamin E, garlic and other antiplatelet supplements (caution)

Melatonin (minor)

Caffeine (minor)

Risk & Side Effects

High: Induction of CYP1A2 and Faster Clearance of Co-administered Drugs

Medium: Reduced Plasma Levels of Tamoxifen's Active Metabolites; Treatment-Emergent Adverse Events; Increased Sex Hormone-Binding Globulin; Ineffectiveness Leading to Delayed Definitive Treatment

Low: Thyroid Function Disturbance; Reduced FMO3 Activity and Body Odor; Effects on Clotting; Balance Disturbance and Tremor at High Doses

Speculative: Tumor Development Without a Prior Carcinogen; Tumor Promotion When Given After Carcinogen Exposure; Hepatocellular Hypertrophy and Broad P450 Induction

Monitoring

Marker	Target	Why
ALT	10–26 U/L (men), 9–22 U/L (women)	Detects liver stress from enzyme induction
AST	10–26 U/L	Confirms an ALT rise is hepatic rather than muscular
TSH	0.5–2.0 mIU/L	Screens for the suspected thyroid-suppressing effect
Free T4	1.0–1.5 ng/dL	Distinguishes true thyroid suppression from a TSH shift alone
Sex hormone-binding globulin	20–60 nmol/L (men), 30–90 nmol/L (women)	The documented hormonal change from the metabolite
Free testosterone	15–25 pg/mL (men)	Captures the net androgen effect that binding-protein changes cause
Urinary 2-hydroxyestrone : 16α-hydroxyestrone ratio	No established target; track change from the individual's own baseline, with a doubling indicating a full response	Confirms the compound is being converted and absorbed at all
Plasma level of any CYP1A2-substrate medication	No supplement-specific target; keep within that drug's own established therapeutic range	The only interaction with documented human consequences

Cadence: Liver and thyroid panels at baseline and 12 weeks, then at 6 and 12 months where use continues; hormone measures at 12 weeks; plasma level of any CYP1A2-substrate medication 2 weeks after starting and 2 weeks after stopping.

Qualitative Assessment

Cyclical breast tenderness and menstrual symptom severity
Libido and morning erections in men
Body odor, specifically a fishy character
Gastrointestinal comfort in the first four weeks
Energy and cognitive clarity
Where a visible lesion motivated use, the symptom score that motivated it, reassessed against a fixed decision point

Indole-3-Carbinol for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment