APPLIED NUTRITIONAL INVESTIGATION Effects of Oral Bovine Colostrum Supplementation on Serum Insulin-like Growth Factor-I Levels Harm Kuipers, MD, PhD, E. van Breda, PhD, G. Verlaan, MSc, and R. Smeets, PhD From Maastricht University, Maastricht, The Netherlands; and Numico Research, Wageningen, The Netherlands OBJECTIVES: We investigated whether supplementation with 60 g/d of bovine colostrum affects blood levels of insulin-like growth factor-I (IGF-I) and IGF binding protein-3 in relation to doping testing. Nine endurance-trained men ingested 60 g/d of bovine colostrum for 4 wk. METHODS: Blood and urine were sampled before starting supplementation. After 4 wk urine and blood samples were taken after an overnight fast and 2 h after ingestion of the last portion to study possible acute effects. RESULTS: Blood IGF-I levels before supplementation were (mean  standard deviation) 31  13 nM/L, and no acute effects were observed after 4 wk of supplementation (33  9 nM/L). Levels of IGF-binding protein-3 were 136  11 nM/L before supplementation and 135  16 nM/L after 4 wk of supplementation. Two hours after ingestion of the last portion, the level of IGF binding protein-3 was 131  19 nM/L, which was not different from baseline values. Drug testing in a laboratory accredited by the International Olympic Committee did not show any forbidden substance before or after 4 wk of supplementation. CONCLUSIONS: Daily supplementation with 60 g of bovine colostrum for 4 wk does not change blood IGF-I or IGF binding protein-3 levels and does not elicit positive results on drug tests. Nutrition 2002; 18:566 –567. ©Elsevier Science Inc. 2002 KEY WORDS: colostrum supplementation, growth factors, doping test INTRODUCTION Oral nutritional supplementation of colostrum, the first milk se- creted by cows after calving, has long been advocated as promot- ing health. In the late 1980s it became an important nutritional supplement for athletes. Although it has not been established unequivocally that colostrum enhances performance in humans, athletes take oral bovine colostrum in an attempt to use all possible legal means to enhance performance. The interest in this supple- ment recently has regained momentum. Colostrum is designed by nature as a substance that protects a newborn’s immune system and provides passive immunity against a host of microorganisms. It also assists the body with protein synthesis, muscle building, and tissue growth. Colostrum is a rich source of bioactive proteins, 1,2 which could account for its pre- scribed actions. Although colostrum might contain proteins with anabolic actions that have not yet been described, a possible mechanism of action could come from insulin-like growth factor-I (IGF-I). It is the most abundant and well-described growth factor in colostrum and has the same amino acid structure in bovines and humans. 3 Administration of IGF-I stimulated muscle protein syn- thesis in animals 1,4 and humans. 5 Colostrum supplementation may increase plasma IGF-I concentrations, which has a direct action on tissue growth, or IGF-I might increase intestinal maturation and, with that increase, nutrient uptake. However, Buckley et al. 6,7 found no increases in plasma IGF-I levels with the use of bovine colostrums (Intact™, GNC, Pittsburgh, PA, USA), whereas Mero et al. 8 found changes in IGF-I levels after training in subjects who had ingested bovine colostrums, although the magnitude of change was small and remained within the normal physiologic range. In addition to IGF-I, bovine colostrum contains growth hormone. Growth hormone also exerts a specific effect on metabolism. 9 In contrast to IGF-I, this form of bovine growth hormone does not bind to the human growth hormone receptor. 10 Because colostrum contains components forbidden by the In- ternational Olympic Committee (IOC; e.g., IGF and growth hor- mone), whether to add colostrum to the IOC’s list of banned substances is being debated. The purpose of this study was to investigate 1) whether colostrum supplementation (60 g/d) has any effect on plasma levels of IGF-I and its binding protein (insulin- like growth factor binding protein-3 [IGFBP3]) and 2) whether 4 wk of supplementation would have any effect on a regular urine drug test in an IOC-accredited laboratory. MATERIALS AND METHODS Subjects Nine, healthy, well-trained, competitive male athletes participated in the study. Mean age was 25 y (range, 19 –29), mean height was 1.83 m (range, 1.72–1.89 m), and mean body weight was 74.8 kg (range, 68.6 – 86.5 kg). Subjects were engaged in endurance train- ing for at least 5 h/wk before the study. During the 4 wk of supplementation, their training programs did not change. The following exclusion criteria were used: intolerance to cow’s milk protein, lactose intolerance, any medical condition requiring med- ication might affect the results of the study, or having taken ergogenic substances, nutritional supplements, or hormonal or chemical components within 6 wk before the start of the study. Design The study was in accordance with the Declaration of Helsinki and Dutch law and was approved by the local medical ethical com- mittee. According to the guidelines, full written informed consent was signed by each subject. Correspondence to: Harm Kuipers, MD, PhD, Department of Movement Sciences, PO Box 616, 6200 MD Maastricht, The Netherlands. E-mail: harm.kuipers@bw.unimaas.nl Nutrition 18:566 –567, 2002 0899-9007/02/$22.00 ©Elsevier Science Inc., 2002. Printed in the United States. 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