The thick, yellowish fluid secreted by the mammary glands prior to and during the first few days after birth, before actual milk is produced by the breast. Colostrum is a highly nutritive substance, loaded with proteins, immune-building substances, and growth factors. Colostrum’s primary purpose is to supply antibodies and growth factors to help newborns fight viruses and bacteria and to jump-start the growth of muscle, bone, and tissue. There is some research showing it has benefits when applied topically for wound healing, but there is also research showing that it was not helpful. The source of colostrum in supplements and skin-care products is bovine (Sources: Journal of Reproductive Immunology, July 1998, pages 155–167; Indian Journal of Pediatrics, July 2005, pages 579–581; Cells Tissues Organs, January 2000, pages 92–100; Australasian Biotechnology, July–August 1997, pages 223–228; and Journal of Dermatologic Surgery Oncology, June 1985, pages 617–622).