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What Causes What
MECHANISM0 NULL

Green tea / EGCG → Insulin resistance (HOMA-IR)

A rise in Green tea / EGCG does not identify a change in Insulin resistance (HOMA-IR).

Brown 2009 found that 400 mg of EGCG twice a day for eight weeks did not change insulin sensitivity, insulin secretion, or glucose tolerance versus lactose in 88 overweight or obese men. Hsu 2011 and Fukino 2006 also found no between-group HOMA difference after a green-tea extract or powder.

Randomized trial · Moderate · N=88

Supported by an experiment or a tightly identified design. Read the caveats.

Mechanism

Authors treat EGCG as a catechin that might make insulin work better. Three assigned contrasts do not find that on a between-group test. Brown, Lane, Coverly and colleagues (2009) assigned overweight or obese men aged 40 to 65 to 400 mg of EGCG or lactose twice a day for eight weeks (46 versus 42). Oral glucose tolerance, insulin sensitivity, and insulin secretion did not move. Diastolic blood pressure fell 2.68 versus 0.06 mm Hg (P=0.014). That is not this page's outcome. Hsu, Liao, Lin and colleagues (2011) assigned 80 obese adults with type 2 diabetes to 1,500 mg a day of decaffeinated green-tea extract (856 mg EGCG) or placebo for sixteen weeks. 68 finished. No measured variable differed between groups, including HOMA-IR. Within the extract arm, HOMA and insulin fell. That is not the assigned contrast. Fukino, Shimbo, Aoki, Okubo and Iso (2006) asked 66 people with borderline or frank diabetes to add 544 mg of green-tea polyphenols a day as powder, or to do nothing, for two months. HOMA, glucose, HbA1c, and insulin did not differ between groups at two months.

Caveats

Researchers assigned people to a catechin or a powder, so this is a trial stamp. The between-group insulin tests missed. Extra papers do not settle the claim. Fukino has no matching placebo. Hsu's within-group HOMA drop is not the contrast. Brown's blood-pressure and mood notes are not HOMA-IR. This page is not a cup of coffee. This is a journal entry, not medical advice.

Effect

qualitative. Brown 2009 EGCG 400 mg BID, 8 wk, N=88 men: insulin sensitivity NS. Hsu 2011 GTE 1500 mg/d, 16 wk, N=68/80 T2D: HOMA between-group NS. Fukino 2006 powder vs no treatment, N=66: HOMA between-group NS.

Nodes

Lifestyle & environmentGreen tea / EGCGBiology & endocrinologyInsulin resistance (HOMA-IR)

Named confounders

Cite this page

What Causes What. “Green tea / EGCG → Insulin resistance (HOMA-IR).” https://whatcauseswhat.org/edges/e-green-tea-insulin (atlas updated 2026-09-02).

https://whatcauseswhat.org/edges/e-green-tea-insulin

Papers