Animal protein, IGF-1 and colon cancer
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 not yet widely recognized that foods such as these, since they are so high in animal protein, can also contribute to increased cancer risk.
When we consume 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, colon cancer included.5-8 Several observational studies have suggested that high circulating IGF-1 may translate into promotion of tumor growth in the colon. For example, one study in men and one another in women found that those with higher levels of IGF-1 had double the risk of colorectal cancers compared to those with lower levels.9,10
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. 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.11,12
It is the amino acid distribution of animal protein that sparks IGF-1 production. 13 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.
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.
Dr. Fuhrman is the #1 New York Times bestselling author of Eat to Live and a board certified family physician specializing in lifestyle and nutritional medicine. His newest book The End of Diabetes explains how to prevent and reverse type II diabetes, avoid its serious complications, and lose weight in the process.Visit his informative website at DrFuhrman.com and blog at DiseaseProof.com. You can also follow Dr. Fuhrman at Facebook.com/DrFuhrman and on Twitter @DrFuhrman.
- 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 in mammalian 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 Res2008;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.
- 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.
- 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.
- 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.