Relationship of Dietary Protein and Soy Isoflavones to Serum IGF-1 and IGF Binding Proteins in the Prostate Cancer Lifestyle Trial

• Published in: Nutrition and cancer Vol. 58; no. 1; pp. 35 - 42
• Main Authors: Dewell, A, Weidner, G, Sumner, M.D, Barnard, R.J, Marlin, R.O, Daubenmier, J.J, Chi, C, Carroll, P.R, Ornish, D
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 01.01.2007; Taylor& Francis
• Subjects: anticarcinogenic activity; apoptosis; Biological and medical sciences; Biomarkers - blood; cell proliferation; diet; dietary protein; Dietary Proteins - administration & dosage; Dietary Proteins - metabolism; disease prevention; Diseases of the digestive system; Epidemiology; essential amino acids; Humans; insulin-like growth factor binding proteins; Insulin-Like Growth Factor Binding Proteins - metabolism; insulin-like growth factor I; Insulin-Like Growth Factor I - metabolism; isoflavones; Isoflavones - administration & dosage; Isoflavones - metabolism; Life Style; lifestyle; low fat diet; Male; Medical sciences; men; nutrient intake; Other treatments; plant source protein; Prostate Cancer Lifestyle Trial; prostatic neoplasms; Prostatic Neoplasms - blood; Prostatic Neoplasms - epidemiology; Prostatic Neoplasms - metabolism; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Risk Factors; Soy Foods; soy protein; soybean products; Soybean Proteins - administration & dosage; Soybean Proteins - metabolism; Treatment. General aspects; Tumors; vegetarian diet; very low fat diet; Human; Isoflavone; Urinary system disease; Prostate disease; Nutrition; Malignant tumor; Insulin like growth factor 1; Serum protein; Feeding; Soy protein; Binding protein; Diet therapy; Clinical trial; Male genital diseases; Prostate cancer; Food; Life style
• DOI: 10.1080/01635580701308034
• ISSN: 0163-5581

High levels of insulin-like growth factor 1 (IGF-1) are associated with increased risk of prostate cancer, whereas increased levels of some of its binding proteins (IGFBPs) seem to be protective. High intakes of dietary protein, especially animal and soy protein, appear to increase IGF-1. However, soy isoflavones have demonstrated anti-proliferative and apoptotic effects both in vitro and in vivo. We evaluated dietary intakes of total protein and soy isoflavones in relation to the IGF axis in prostate cancer patients making comprehensive lifestyle changes including a very low-fat vegan diet supplemented with soy protein (58 g/day). After one year, intervention group patients reported significantly higher intakes of dietary protein and soy isoflavones compared to usual-care controls (P < 0.001). IGF-1 increased significantly in both groups, whereas IGFBP-1 rose in the experimental group only (P < 0.01). Increases in vegetable protein over one year were associated with increases in IGFBP-1 among intervention group patients (P < 0.05). These results suggest that dietary protein and soy isoflavones, in the context of comprehensive lifestyle changes, may not significantly alter IGF-1. However, given the recent literature indicating that high intake of protein rich in essential amino acids (animal or soy protein) may increase IGF-1, it may be prudent for men with early stage prostate cancer not to exceed dietary protein recommendations.