Antimicrobial factors in human milk

Acta Paediatr Scand. 1977 Mar;66(2):229-32. doi: 10.1111/j.1651-2227.1977.tb07838.x.


Levels of immunoglobulins, lactoferrin and lysozyme were determined in milk samples obtained from well-nourished and under-nourished Indian women at different stages of lactation. The concentration of immunoglobulins and lactoferrin was higher in colostrum than in mature milk while the lysozyme levels showed a progressive increase with the period of lactation. There were no significant differences in the levels between the two groups of women. Administration of iron did not alter either the total or percentage saturation of lactoferrin in milk. These results indicate that antibacterial factors in milk are not influenced by the nutritional status of the mother and that iron supplementation does not interfere with the bacteriostatic function of lactoferrin.

PIP: Lower incidences of infection among breastfed vs. bottlefed infants have been attributed, not only to bottle contamination, but to the presence of various antibacterial factors in breast milk. 3 of these factors, immunoglobulins, lysozyme, and lactoferrin, were quantitated from milk samples from well-nourished and under-nourished Indian women in various stages of lactation. An ancillary concern of this study was to determine whether iron supplementation in under-nourished lactating women might abolish the bacteriostatic mechanism of lactoferrin by altering its saturation in milk, thus interfering with its biological function. 250 women gave breast milk samples for study. In addition, 11 lactating women were given 200 mg of iron intramuscularly, and their milk samples were assayed. In the nonsupplemented women, the concentration of immunoglobulin A (IgA) was high in colostrum, with a mean level of 350 mg/100 ml, and fell rapidly during the first 4 weeks of lactation, to a mean level of 110 mg/100 ml. IgG concentration was slightly higher in colostrum than in mature milk. Lactoferrin concentration was very high in colostrum, with a mean level of 600 mg/100 ml, and fell progressively up to 5 months of lactation, stabilizing at a mean level of 180 mg/100 ml. Lysozyme content of colostrum was lower than that of mature milk and showed a progressive increase with duration of lactation; its highest level of 42 mg/100 ml was reached at 12 months. No significant differences in levels of immunoglobulins, lactoferrin, and lysozyme were found between well-nourished and under-nourished mothers. In women who received the iron supplements, at first the mean level of total lactoferrin was 240 mg/100 ml, 9% of which was saturated. No significant changes in concentrations of either total or saturated lactoferrin were found after administering the iron supplement.

MeSH terms

  • Colostrum / analysis
  • Colostrum / immunology
  • Female
  • Hemoglobins / analysis
  • Humans
  • Immunoglobulin A / analysis
  • Immunoglobulin G / analysis
  • Immunoglobulin M / analysis
  • Immunoglobulins* / analysis
  • Iron / pharmacology
  • Lactation
  • Lactoferrin* / analysis
  • Lactoglobulins* / analysis
  • Milk, Human / analysis
  • Milk, Human / immunology*
  • Muramidase* / analysis
  • Nutrition Disorders
  • Pregnancy
  • Serum Albumin / analysis
  • Time Factors


  • Hemoglobins
  • Immunoglobulin A
  • Immunoglobulin G
  • Immunoglobulin M
  • Immunoglobulins
  • Lactoglobulins
  • Serum Albumin
  • Iron
  • Muramidase
  • Lactoferrin