Most people are aware of the connections between red and processed meats and cancer—that there is convincing evidence that these dangerous foods are a cause of colon cancer.1 In addition, cooking any meat at high temperatures (for example, grilled or fried chicken) forms carcinogenic compounds such as heterocyclic amines, which contribute to cancer risk.2,3 However, animal foods such as non-fat dairy products, egg whites, and fish are considered healthful by most people. It is not yet widely recognized that foods such as these, since they are so high in animal protein, may also contribute to increased cancer risk.
Animal protein increases production of IGF-1 (insulin-like growth factor)
When we consume too much animal protein, the body increases its production of a hormone called IGF-1, (insulin-like growth factor 1). IGF-1 is one of the body’s important growth promoters during fetal and childhood growth, but later in life IGF-1 promotes the aging process. Reduced IGF-1 signaling in adulthood is associated with reduced oxidative stress, decreased inflammation, enhanced insulin sensitivity and longer lifespan.4 In contrast, IGF-1 has been shown to promote the growth, proliferation and spread of cancer cells, and elevated IGF-1 levels are linked to increased risk of several cancers. Several observational studies have suggested that high circulating IGF-1 may translate into promotion of tumor growth in colon, prostate and breast tissue.5-13
Which foods raise IGF-1?
Since the primary dietary factor that determines IGF-1 levels is animal protein, the excessive meat, fowl, seafood, and dairy intake common in our society elevates circulating IGF-1. It is the amino acid distribution of animal protein that sparks IGF-1 production.16 For this reason, isolated soy protein, found in protein powders and meat substitutes, may also be problematic because the protein is unnaturally concentrated and its amino acid profile is very similar to that of animal protein.
Refined carbohydrates, like white flour, white rice, and sugars can also raise IGF-1 levels, because they cause rapid increases in insulin levels, leading to increases in IGF-1 signaling. In fact, IGF-1 signaling is thought to be a major factor in the connection between diabetes and cancer.14,15
How can we keep IGF-1 in a safe range?
Reducing IGF-1 levels by dietary methods is now considered by many scientists to be an effective cancer prevention measure. Minimizing or avoiding animal protein, isolated soy protein and refined carbohydrates can help to keep our IGF-1 levels in a safe range. Green vegetables, beans and other legumes, and seeds are rich in plant protein and they have cancer-preventive, not cancer-promoting properties. For optimal cancer protection, vegetables, beans, fruits, nuts and seeds should comprise the vast majority of our calories.
Continuous Update Project Interim Report Summary. Food, Nutrition, Physical Activity, and the Prevention of Colorectal Cancer. World Cancer Research Fund / American Institute for Cancer Research.; 2011.
Thomson B: Heterocyclic amine levels in cooked meat and the implication for New Zealanders.Eur J Cancer Prev 1999; 8:201-206.
Zheng W, Lee S-A: Well-Done Meat Intake, Heterocyclic Amine Exposure, and Cancer Risk.Nutr Cancer 2009; 61:437-446.
Bartke A: Minireview: role of the growth hormone/insulin-like growth factor system inmammalian aging.Endocrinology 2005; 146:3718-3723.
Chitnis MM, Yuen JS, Protheroe AS, et al: The type 1 insulin-like growth factor receptor pathway.Clin Cancer Res 2008; 14:6364-6370.
Werner H, Bruchim I: The insulin-like growth factor-I receptor as an oncogene.Arch Physiol Biochem 2009; 115:58-71.
Davies M, Gupta S, Goldspink G, et al: The insulin-like growth factor system and colorectal cancer: clinical and experimental evidence.Int J Colorectal Dis 2006; 21:201-208.
Sandhu MS, Dunger DB, Giovannucci EL: Insulin, insulin-like growth factor-I (IGF-I), IGF binding proteins, their biologic interactions, and colorectal cancer.J Natl Cancer Inst 2002; 94:972-980.
Giovannucci E, Pollak MN, Platz EA, et al: A prospective study of plasma insulin-like growth factor-1 and binding protein-3 and risk of colorectal neoplasia in women.Cancer Epidemiol Biomarkers Prev 2000; 9:345-349.
Ma J, Pollak MN, Giovannucci E, et al: Prospective study of colorectal cancer risk in men and plasma levels of insulin-like growth factor (IGF)-I and IGF-binding protein-3.J Natl Cancer Inst 1999; 91:620-625.
Renehan AG, Zwahlen M, Minder C, et al: Insulin-like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis.Lancet 2004; 363:1346-1353.
Shi R, Yu H, McLarty J, et al: IGF-I and breast cancer: a meta-analysis.Int J Cancer 2004; 111:418-423.
Rowlands MA, Gunnell D, Harris R, et al: Circulating insulin-like growth factor peptides and prostate cancer risk: a systematic review and meta-analysis.Int J Cancer 2009; 124:2416-2429.
Cannata D, Fierz Y, Vijayakumar A, et al: Type 2 diabetes and cancer: what is the connection?Mt Sinai J Med 2010; 77:197-213.
Venkateswaran V, Haddad AQ, Fleshner NE, et al: Association of diet-induced hyperinsulinemia with accelerated growth of prostate cancer (LNCaP) xenografts.J Natl Cancer Inst 2007; 99:1793-1800.
Thissen JP, Ketelslegers JM, Underwood LE: Nutritional regulation of the insulin-like growth factors.Endocr Rev 1994; 15:80-101.
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.
*There is no guarantee of specific results.Results can vary. All material provided on the DrFuhrman.com website is provided for informational or educational purposes only.
Consult a physician regarding the applicability of any opinions or recommendations with respect to your symptoms or medical condition.