Brewed green tea offers modest, dependable improvements in cholesterol, blood sugar, blood pressure, and body weight, with population data linking regular drinking to lower heart-disease and overall death rates. Brewed tea is safe long-term; concentrated extract capsules taken in large single doses on an empty stomach can cause liver injury. (Full Review)

Protocol

Standard intake (brewed tea)

3–5 cups daily

Delivering several hundred mg catechins, consumed across the day

Standard supplementation (extract)

250–400 mg EGCG/day

Standardized extract taken with food, ideally in divided doses

Timing & dosing

Earlier in day, split doses

Splitting the daily dose with meals maintains exposure and lowers peak EGCG linked to liver injury

Time to effect

Cardiometabolic markers

4–12 weeks

Lipids, blood sugar, blood pressure changes emerge with consistent intake

Alertness

Within an hour

Acute caffeine/L-theanine effects on alertness

Benefits

High: Improved blood lipids; modest cardiovascular risk reduction

Medium: Lower all-cause mortality; improved glycemic control; modest weight and body-fat reduction; lower blood pressure

Low: Enhanced attention and mood; cancer risk reduction

Speculative: Cognitive aging and dementia protection; longevity-pathway activation

Contraindications

Active liver disease or prior supplement-related liver injury (avoid concentrated extracts)

Pregnancy and breastfeeding (avoid high-dose extracts, limit caffeine)

Significant iron-deficiency anemia, poorly controlled arrhythmias, or anxiety disorders (limit caffeine-bearing forms)

Key Interactions

Anticoagulant and antiplatelet drugs (warfarin, aspirin, clopidogrel)

Stimulant medications and other caffeine sources (ephedrine, decongestants, ADHD medications)

Iron supplements

Hepatotoxic drugs and supplements (high-dose acetaminophen, certain statins, other herbal extracts)

Beta-blockers and certain blood-pressure drugs

Bortezomib and certain chemotherapies

Risk & Side Effects

High: Liver injury from concentrated extracts; caffeine-related effects

Medium: Reduced iron absorption; gastrointestinal upset

Low: Bleeding and drug-interaction risk

Speculative: Fluoride and heavy-metal accumulation

Monitoring

Marker	Target	Why
ALT	< 25 U/L (men), < 20 U/L (women)	Detects early liver injury from extracts
AST	< 25 U/L	Complements ALT for liver-injury detection
LDL cholesterol	< 100 mg/dL	Tracks the main lipid benefit
Fasting glucose	70–90 mg/dL	Tracks glycemic benefit
HbA1c	< 5.4%	Captures longer-term glucose effect
Blood pressure	< 120/80 mmHg	Tracks the blood-pressure benefit
Ferritin	50–150 ng/mL	Screens for iron depletion from catechins

Cadence: Liver enzymes at baseline, 8–12 weeks, then every 6–12 months; cardiometabolic markers reassessed at 12 weeks and periodically thereafter

Qualitative Assessment

Sleep quality and ease of falling asleep (sensitive to caffeine timing)
Daytime energy and alertness without jitteriness
Cognitive focus and subjective calmness ("calm alertness")
Digestive comfort (absence of nausea or reflux)
Absence of liver-warning symptoms (fatigue, dark urine, right-upper-abdominal discomfort)

Green Tea for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment