Here's the Goldman reference Dr. Jack mentioned:
Page 126 of the "old" BAB cites a 1983 study by Goldman which found that
the same concentrations of immunological ingredients were present in human
milk throughout the second year as were present during the first. A 1986
study by Gulick confirmed this. (Goldman, A. Immunologic components in
human milk during the second year of lactation. Acta Paediatr Scand, 1983;
72:461-62.) (Also, Gulick, E. The effects of breastfeeding on toddler
health. Pediatric Nurs 1986; 12:51-54.)
Nancy Kramer
Sitka, Alaska