Re: re: role of the insulin-like growth factors in cancer development and progression.

We write to correct several misrepresentations and serious factual errors in the correspondence by Samuel S. Epstein (1). Among these are the statements that “the nation’s milk supply has been contaminated with excess IGF [insulin-like growth factor] levels;” “IGF . . . is readily absorbed from the gastrointestinal tract, and has growth promoting effects;” and “confirmation of these concerns by an international expert committee prompted the January 2000 European ban on the marketing and sale of rBGH [recombinant bovine growth hormone] milk.” The IGF-I content of milk from cattle treated with bovine somatotropin (rBST or rBGH) has been reviewed extensively by the U.S. Food and Drug Administration (2), the European Union (3), and the World Health Organization (WHO) (4). Comparisons of marketed milk indicate that there are no differences in the IGF-I concentrations between milk certified as derived from cows not treated with rBST and milk derived from cows receiving rBST (4). There is thus no evidence that milk marketed from herds treated with rBST has “excess IGF levels” as stated in (1). In addition, studies investigating the biologic activity of orally delivered IGF-I have uniformly demonstrated no change in serum IGF-I concentrations, even at oral doses greatly exceeding physiologic levels of IGF-I present in the digestive tract (5,6). Furthermore, the Joint Expert Committee on Food Additives (JECFA) of the United Nations Food and Agricultural Organization (FAO) (4) concluded that “any increase in the concentration of IGF-I in milk from rBST-treated cows is orders of magnitude lower than the physiological amounts produced in the gastrointestinal tract and in other parts of the body.” Finally, the European Union’s decision not to approve rBST for sale in member countries was based not on human health concerns but rather on animal issues (7). Milk and milk products from cattle treated with rBST are recognized as safe and may be marketed in European Union member countries (3).