IGF-1: The Hidden Hormone That Fuels Cancer (And How to Lower It Naturally)
August 08, 2025 by Joel Fuhrman, MD
You may not have heard of insulin-like growth factor 1 (IGF-1)—but this powerful hormone could be quietly influencing your risk of cancer, aging, and chronic disease. IGF-1 plays a role in healthy childhood development as well as healthy aging, but too much of it may do more harm than good.
Here’s what the science shows—and how a Nutritarian diet may be your most powerful defense.
The Problem: When Growth Turns Dangerous
IGF-1 helps your cells grow and divide. That’s great when you’re a child—but in adults, it’s more complicated. Lower (but not excessively low) IGF-1 activity is linked to longevity, but excessively high IGF-1 can fuel abnormal cell growth, suppress apoptosis (the natural death of damaged cells), and drive the development of cancer. Also, at older ages (over 65 or 70), IGF-1 production slows and levels that are too low become a bigger concern, since IGF-1 is necessary to maintain bone and muscle mass as well as cognitive function.1-8
Higher IGF-1 levels have been linked to:
• Increased risk of breast, prostate, and colorectal cancers9-11
• Accelerated aging and premature death12
• Greater resistance to cancer therapies13
• A higher likelihood of developing a second cancer in cancer survivors14
IGF-1 isn’t inherently bad—but it must be balanced. Unfortunately, the standard American diet drives IGF-1 levels dangerously high, especially due to excess animal protein and refined carbohydrates.
The Evidence: What the Research Says is the Optimal IGF-1 Level
A meta-analysis of 19 studies including over 30,000 participants found that IGF-1 levels that are too high or too low are associated with a greater risk of early death. The sweet spot? Between 120 and 160 ng/ml.12
IGF-1 levels peak in our teens and twenties and decline with age. Apart from age, dietary protein intake is the major regulator of IGF-1 levels, especially animal protein. Since essential amino acids in particular trigger the production of IGF-1, animal protein, which is higher in essential amino acids than plant protein, increases IGF-1 more than plant protein.15-17 High-glycemic, refined carbohydrates also raise IGF-1 somewhat.18-20 Western diets rich in meat, dairy, and refined carbohydrate commonly push IGF-1 levels over 200 ng/ml (in young and middle-aged adults), raising the risk for cancers.4
To extend your lifespan and reduce cancer risk, aim for an IGF-1 level that's low, but not too low—especially after age 75, when IGF-1 is essential for maintaining bone, brain, and muscle health.
Here’s how to do it:
Ditch animal protein for plant protein. Replace meat, eggs, and dairy with beans, lentils, tofu, nuts, and seeds. The amino acid profile of animal protein triggers excessive IGF-1 production.
Adopt a Nutritarian diet. This eating style emphasizes plant food diversity and ensures you get adequate protein from greens, seeds, and legumes—without over-activating IGF-1.
Why a Nutritarian Diet Keeps IGF-1 Levels Favorable
Restricting animal protein during most of adult life to maintain a relatively low, but not excessively low IGF-1 is an important objective for those desirous of superior health and life extension. Unlike other plant-based diets that may fall short on protein in later life, the Nutritarian approach is designed to sustain optimal IGF-1 levels throughout life with plant protein-rich foods such as greens, beans (including soybeans), and seeds. By emphasizing phytochemical-rich foods and plant protein, it helps:
Prevent cancer by keeping IGF-1 in the safe range
Support longevity by protecting against frailty in older adults
Ensure micronutrient completeness and phytochemical variety to reduce inflammation, improve immunity, and reverse disease
Dr. Fuhrman’s medical practice and decades of research show that this is not just a theory—it’s a proven path to a longer, healthier life.
Take Action
Here’s your IGF-1 challenge:
This week, swap out meat or dairy in at least 3 meals. Use beans instead of beef. Blend your smoothie with flax seeds, hemp seeds, and kale instead of whey protein. Try a cashew cheese recipe in place of cheddar.
If you’ve never had your IGF-1 levels tested, ask your doctor to include it in your next routine blood panel or use an at-home test, especially if you're over age 70. And if you’re working on cancer prevention or recovery, keeping IGF-1 in check is one of the smartest moves you can make.
Want more support? Join Dr. Fuhrman’s Nutritarian Membership and gain access to:
🌱 Over 2,000+ recipes using plant-based, cancer-fighting ingredients
📅 Step-by-step meal plans that simplify your health journey
📚 Science-backed guidance from Dr. Fuhrman and his team
👩🍳 Tools to help you ditch animal products and transform your plate—without sacrificing flavor
👉 Join the membership today and start optimizing your IGF-1 the delicious way.
References
Lamberts SW, van den Beld AW, van der Lely AJ. The endocrinology of aging.Science 1997, 278:419-424.
Witard OC, McGlory C, Hamilton DL, Phillips SM. Growing older with health and vitality: a nexus of physical activity, exercise and nutrition.Biogerontology 2016, 17:529-546.
Traylor DA, Gorissen SHM, Phillips SM. Perspective: Protein Requirements and Optimal Intakes in Aging: Are We Ready to Recommend More Than the Recommended Daily Allowance?Adv Nutr 2018, 9:171-182.
Levine ME, Suarez JA, Brandhorst S, et al. Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population.Cell Metab 2014, 19:407-417.
Doi T, Shimada H, Makizako H, et al. Association of insulin-like growth factor-1 with mild cognitive impairment and slow gait speed.Neurobiol Aging 2015, 36:942-947.
Werner H, LeRoith D. Hallmarks of cancer: The insulin-like growth factors perspective.Front Oncol 2022, 12:1055589.
Balasubramanian P, Longo VD. Growth factors, aging and age-related diseases.Growth Horm IGF Res 2016, 28:66-68.
Fanti M, Longo VD. Nutrition, GH/IGF-1 signaling, and cancer.Endocr Relat Cancer 2024, 31.
Watts EL, Perez-Cornago A, Fensom GK, et al. Circulating insulin-like growth factors and risks of overall, aggressive and early-onset prostate cancer: a collaborative analysis of 20 prospective studies and Mendelian randomization analysis.International Journal of Epidemiology 2022, 52:71-86.
Murphy N, Knuppel A, Papadimitriou N, et al. Insulin-like growth factor-1, insulin-like growth factor-binding protein-3, and breast cancer risk: observational and Mendelian randomization analyses with approximately 430 000 women.Ann Oncol 2020, 31:641-649.
Murphy N, Carreras-Torres R, Song M, et al. Circulating Levels of Insulin-like Growth Factor 1 and Insulin-like Growth Factor Binding Protein 3 Associate With Risk of Colorectal Cancer Based on Serologic and Mendelian Randomization Analyses.Gastroenterology 2020, 158:1300-1312.e1320.
Rahmani J, Montesanto A, Giovannucci E, et al. Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis.Aging Cell 2022, 21:e13540.
Basu R, Kopchick JJ. GH and IGF1 in cancer therapy resistance.Endocrine-Related Cancer 2023, 30:e220414.
Shanmugalingam T, Bosco C, Ridley AJ, Van Hemelrijck M. Is there a role for IGF-1 in the development of second primary cancers?Cancer Med 2016, 5:3353-3367.
Thissen JP, Ketelslegers JM, Underwood LE. Nutritional regulation of the insulin-like growth factors.Endocr Rev 1994, 15:80-101.
Clemmons DR, Seek MM, Underwood LE. Supplemental essential amino acids augment the somatomedin-C/insulin-like growth factor I response to refeeding after fasting.Metabolism 1985, 34:391-395.
Lee DH, Tabung FK, Giovannucci EL. Association of animal and plant protein intakes with biomarkers of insulin and insulin-like growth factor axis.Clin Nutr 2022, 41:1272-1280.
Runchey SS, Pollak MN, Valsta LM, et al. Glycemic load effect on fasting and post-prandial serum glucose, insulin, IGF-1 and IGFBP-3 in a randomized, controlled feeding study.Eur J Clin Nutr 2012, 66:1146-1152.
Brand-Miller JC, Liu V, Petocz P, Baxter RC. The glycemic index of foods influences postprandial insulin-like growth factor-binding protein responses in lean young subjects.American Journal of Clinical Nutrition 2005, 82:350-354.
Biddinger SB, Ludwig DS. The insulin-like growth factor axis: a potential link between glycemic index and cancer.Am J Clin Nutr 2005, 82:277-278.
Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.
IGF-1: The Hidden Hormone That Fuels Cancer (And How to Lower It Naturally)
August 08, 2025 by Joel Fuhrman, MD
You may not have heard of insulin-like growth factor 1 (IGF-1)—but this powerful hormone could be quietly influencing your risk of cancer, aging, and chronic disease. IGF-1 plays a role in healthy childhood development as well as healthy aging, but too much of it may do more harm than good.
Here’s what the science shows—and how a Nutritarian diet may be your most powerful defense.
The Problem: When Growth Turns Dangerous
IGF-1 helps your cells grow and divide. That’s great when you’re a child—but in adults, it’s more complicated. Lower (but not excessively low) IGF-1 activity is linked to longevity, but excessively high IGF-1 can fuel abnormal cell growth, suppress apoptosis (the natural death of damaged cells), and drive the development of cancer. Also, at older ages (over 65 or 70), IGF-1 production slows and levels that are too low become a bigger concern, since IGF-1 is necessary to maintain bone and muscle mass as well as cognitive function.1-8
Higher IGF-1 levels have been linked to:
• Increased risk of breast, prostate, and colorectal cancers9-11
• Accelerated aging and premature death12
• Greater resistance to cancer therapies13
• A higher likelihood of developing a second cancer in cancer survivors14
IGF-1 isn’t inherently bad—but it must be balanced. Unfortunately, the standard American diet drives IGF-1 levels dangerously high, especially due to excess animal protein and refined carbohydrates.
Sources:
Protein Requirements and Optimal Intakes in Aging: Are We Ready to Recommend More Than the Recommended Daily Allowance?
Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population
Nutrition, GH/IGF-1 signaling, and cancer
GH and IGF1 in cancer therapy resistance
Is there a role for IGF-1 in the development of second primary cancers?
The Evidence: What the Research Says is the Optimal IGF-1 Level
A meta-analysis of 19 studies including over 30,000 participants found that IGF-1 levels that are too high or too low are associated with a greater risk of early death. The sweet spot? Between 120 and 160 ng/ml.12
Source:
Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis
The Solution: Eat for a healthy IGF-1 Level
IGF-1 levels peak in our teens and twenties and decline with age. Apart from age, dietary protein intake is the major regulator of IGF-1 levels, especially animal protein. Since essential amino acids in particular trigger the production of IGF-1, animal protein, which is higher in essential amino acids than plant protein, increases IGF-1 more than plant protein.15-17 High-glycemic, refined carbohydrates also raise IGF-1 somewhat.18-20 Western diets rich in meat, dairy, and refined carbohydrate commonly push IGF-1 levels over 200 ng/ml (in young and middle-aged adults), raising the risk for cancers.4
To extend your lifespan and reduce cancer risk, aim for an IGF-1 level that's low, but not too low—especially after age 75, when IGF-1 is essential for maintaining bone, brain, and muscle health.
Here’s how to do it:
Related: How Plant Protein Wins Over Animal Protein
Sources:
Nutritional regulation of the insulin-like growth factors
Association of animal and plant protein intakes with biomarkers of insulin and insulin-like growth factor axis
The insulin-like growth factor axis: a potential link between glycemic index and cancer
Why a Nutritarian Diet Keeps IGF-1 Levels Favorable
Restricting animal protein during most of adult life to maintain a relatively low, but not excessively low IGF-1 is an important objective for those desirous of superior health and life extension. Unlike other plant-based diets that may fall short on protein in later life, the Nutritarian approach is designed to sustain optimal IGF-1 levels throughout life with plant protein-rich foods such as greens, beans (including soybeans), and seeds. By emphasizing phytochemical-rich foods and plant protein, it helps:
Dr. Fuhrman’s medical practice and decades of research show that this is not just a theory—it’s a proven path to a longer, healthier life.
Take Action
Here’s your IGF-1 challenge:
This week, swap out meat or dairy in at least 3 meals. Use beans instead of beef. Blend your smoothie with flax seeds, hemp seeds, and kale instead of whey protein. Try a cashew cheese recipe in place of cheddar.
If you’ve never had your IGF-1 levels tested, ask your doctor to include it in your next routine blood panel or use an at-home test, especially if you're over age 70. And if you’re working on cancer prevention or recovery, keeping IGF-1 in check is one of the smartest moves you can make.
Related: What blood tests do I need?
Follow Dr. Fuhrman’s Proven Plan
Want more support? Join Dr. Fuhrman’s Nutritarian Membership and gain access to:
🌱 Over 2,000+ recipes using plant-based, cancer-fighting ingredients
📅 Step-by-step meal plans that simplify your health journey
📚 Science-backed guidance from Dr. Fuhrman and his team
👩🍳 Tools to help you ditch animal products and transform your plate—without sacrificing flavor
👉 Join the membership today and start optimizing your IGF-1 the delicious way.
Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 30 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.