Does Green Tea Lower IGF-1? Examining the Scientific Evidence

December 31, 2025 •

4 min read

Increased circulating concentrations of IGF-1 are consistently associated with a higher risk of certain cancers, like prostate cancer. This has led many to question: does green tea lower IGF-1 effectively? The potent polyphenols in green tea, particularly EGCG, have been identified as a key area of interest in the investigation of growth factor modulation.

Quick Summary

Green tea compounds, especially EGCG, can inhibit the IGF-1 signaling pathway and have been shown to reduce IGF-1 levels in some animal and human studies, though results vary across trials.

Key Points

IGF-1 Modulation: Green tea polyphenols, especially EGCG, show promise in modulating IGF-1 and its binding protein, IGFBP-3.
Signaling Inhibition: Studies confirm that EGCG can directly inhibit the IGF-1 receptor signaling pathway.
Inconsistent Human Results: While some human trials show significant reductions in IGF-1, others show weaker or non-significant effects, possibly due to dose, duration, and bioavailability factors.
Strong Animal Study Evidence: A significant body of animal research, particularly in cancer models, demonstrates that green tea extracts can substantially lower IGF-1 levels.
Impact on Binding Proteins: Green tea has also been linked to increasing levels of IGFBP-3, which acts to suppress IGF-1's mitogenic effects.
Chemopreventive Potential: The ability to influence the IGF-1 axis makes green tea a subject of interest for cancer chemoprevention.
Dosage Matters: The high concentrations of EGCG used in some studies may not be achievable through regular green tea consumption alone.
Further Research Needed: More large-scale, long-term human trials are required to fully understand green tea's consistent effect on IGF-1 levels in diverse populations.

Understanding IGF-1 and its Role

Insulin-like growth factor-1 (IGF-1) is a hormone with a molecular structure similar to insulin. It plays a crucial role in cell growth, metabolism, and proliferation throughout the body. While essential for normal growth and development, abnormally high levels of IGF-1 have been linked to an increased risk of several cancers, including prostate, breast, and lung cancers. Therefore, substances that can help regulate or lower IGF-1 levels are of significant scientific interest.

The Bioactive Compounds in Green Tea

Green tea is rich in polyphenols, particularly catechins, with epigallocatechin-3-gallate (EGCG) being the most abundant and well-studied. These bioactive compounds are known for their strong antioxidant properties and their ability to influence numerous cellular pathways. A primary focus of research has been EGCG's interaction with the IGF/IGF-1R axis, a critical signaling pathway involved in cell growth and survival.

Mechanisms by Which Green Tea May Influence IGF-1

Research suggests that green tea polyphenols, especially EGCG, can interfere with the IGF-1 signaling cascade through several key mechanisms:

Inhibiting the IGF-1 Receptor (IGF-1R): EGCG has been shown to directly inhibit the activation of the IGF-1R, a tyrosine kinase receptor that receives growth signals. By blocking this receptor, EGCG can prevent the downstream signaling that promotes cell proliferation.
Modulating Insulin-Like Growth Factor-Binding Proteins (IGFBPs): These proteins regulate the bioavailability of IGF-1. Some studies suggest that green tea polyphenols can increase the level of IGFBP-3, which binds to IGF-1 and inhibits its pro-growth effects.
Influencing Parallel Signaling Pathways: EGCG may also affect parallel signaling pathways related to cell growth and atrophy, sometimes independently of the main PI3K/Akt axis typically associated with IGF-1 and insulin.
Antioxidant and Anti-inflammatory Effects: The general antioxidant and anti-inflammatory properties of green tea can also have a systemic effect that beneficially alters the body's hormonal and growth factor environment.

Comparing Human and Animal Study Findings

Scientific research on the effect of green tea on IGF-1 levels has been conducted in both laboratory animals and human clinical trials, with some variations in outcomes.


Feature	Animal Studies (e.g., TRAMP mice)	Human Trials (e.g., in men at risk for CaP)
Effect on IGF-1 Levels	Substantial and significant reduction in IGF-1 observed in several studies.	Mixed results; some show significant reductions in IGF-1, while others find non-significant effects.
Effect on IGFBP-3 Levels	Often shows an increase in IGFBP-3 levels.	Inconsistent; some suggest increases, while others report weak or no effect.
Dosage & Bioavailability	High doses of polyphenols often administered via infusion or concentrated fluid.	Lower, less concentrated doses from supplements or brewed tea, potentially affected by rapid metabolism and excretion.
Intervention Duration	Often involves longer, continuous treatment periods of several months.	Varies greatly, from a few weeks to several months.
Study Population	Controlled genetic models (e.g., TRAMP mice susceptible to prostate cancer).	Men at risk for cancer, with existing health conditions like PCOS, or healthy volunteers.

The Role of EGCG in IGF-1 Modulation

EGCG, the most potent catechin in green tea, plays a central role in the observed IGF-1 modulation. In cellular and animal models, EGCG has consistently demonstrated its ability to inhibit the IGF-1 signaling pathway. For example, in human hepatocellular carcinoma cells, EGCG was shown to inhibit the activation of the IGF-1 receptor and reduce IGF-1 protein levels. This suggests that EGCG directly interferes with the pathway, making it a promising candidate for further investigation. However, the concentration of EGCG delivered to cells in vitro often far exceeds what is achieved through normal green tea consumption, which may explain some of the conflicting results seen in human trials. Furthermore, the bioavailability of EGCG in humans can be relatively low, as it is rapidly metabolized and excreted.

Dosage and Formulation Considerations

The research on green tea and IGF-1 highlights the importance of dosage and the form of consumption. Studies have used everything from brewed green tea to concentrated extracts (like Polyphenon E) and isolated EGCG supplements. In a pilot trial involving men, green tea supplementation had some effect on IGF-1 and IGFBP-3, but the study was small and results were imprecisely estimated. Other clinical trials and meta-analyses, particularly in women with PCOS, have noted beneficial effects on metabolic parameters but with inconsistent effects on reproductive hormones, including some related to the IGF axis. The optimal dose and duration for affecting IGF-1 levels in humans remain unclear and likely depend on individual factors and the specific health outcome being studied.

Conclusion: Interpreting the Evidence

Scientific evidence from laboratory studies and animal models strongly suggests that green tea polyphenols, particularly EGCG, can significantly lower IGF-1 levels and inhibit its signaling pathways. However, translating these findings to a reliable effect in humans is more complex. While some human trials support a reduction in IGF-1 with green tea supplementation, particularly in men at high risk of prostate cancer, other human studies show weaker or non-significant effects. This variability likely stems from differences in study design, dosage, duration, and the lower bioavailability of catechins from consumed tea compared to concentrated research doses. Therefore, while green tea holds potential as a dietary factor to help modulate IGF-1, it is not a guaranteed or uniform method for all individuals. Future large-scale human trials are needed to provide more definitive guidance. For now, enjoying green tea as part of a healthy lifestyle remains a practice backed by a wide range of general health benefits beyond just IGF-1 modulation.

Oral consumption of green tea polyphenols inhibits insulin-like growth factor-I-induced signaling in an autochthonous mouse model of prostate cancer.

Frequently Asked Questions

IGF-1, or Insulin-like Growth Factor-1, is a hormone critical for cell growth and metabolism. While necessary for normal function, excessively high levels are associated with increased risk for certain diseases, including some cancers.

The most active compound is epigallocatechin-3-gallate (EGCG). This catechin has been extensively studied for its ability to interfere with the IGF-1 signaling pathway.

Human studies have yielded inconsistent results. Some trials, particularly with concentrated extracts in men at high cancer risk, have shown significant IGF-1 reduction, while other, smaller studies show no clear effect.

Green tea polyphenols, especially EGCG, can inhibit the IGF-1 receptor's activation, increase the concentration of IGF-binding proteins (IGFBP-3) that neutralize IGF-1, and affect other parallel signaling pathways related to cell proliferation.

Studies often use highly concentrated extracts to achieve significant effects, suggesting extracts may be more potent. However, the bioavailability and optimal dose in humans are not well established, and long-term consumption of brewed tea may also offer benefits.

The evidence is not yet conclusive enough for definitive clinical recommendations. While promising, especially in animal models and some human chemoprevention trials, larger-scale studies are needed to confirm efficacy and establish optimal dosages for IGF-1 modulation.

Yes, green tea has been studied for its effects on various hormones. Research in women with PCOS, for example, has shown potential effects on fasting insulin and androgens, though results can be inconsistent.

Research suggests that EGCG can promote the nuclear export of the atrophy-related transcription factor Foxo1, similar to IGF-1. This indicates a potential anti-atrophy benefit in skeletal muscle, rather than inhibiting healthy muscle growth.