Buyer Beware: Breast May Be Best, But Not What You Get
There are many reasons why breast milk is the recommended for infants during the first months of life. The antibodies in breast milk help to reduce incidence of colds and gastrointestinal illness for the duration of breastfeeding (Duijts et al.). The unique and dynamic flavor profile of breast milk may encourage healthier dietary choices later in life (Mennella). Breast milk does not require dilution, and there is a virtually non-existent chance of contamination when infants nurse. But for women who are unable to produce enough breast milk, is it a good idea to purchase human milk?
The composition of breast milk is highly variable and depends on the time of day, nutritional status of the mother, time since the birth and many other factors. Arslanoglu and co-workers review evidence that show that levels of melatonin follow maternal day-night patterns. Innis, when looking only at nutrients important for infant neurological development, found that levels of vitamin A, several water-soluble vitamins including vitamin B-6, vitamin B-12, and folate, the minerals iodine and selenium, and fatty acids depend on maternal intake or status. De Azeredo and colleagues show that carotenoid and vitamin E levels correlate with maternal status. Fat contents of milk increase during the postpartum period (Szabó), and can even change abruptly with acute modifications in the macronutrient composition of the maternal diet (Mohammed).
Over the years, as we learn more about human nutrition, infant formula has been changing its composition to better mimic the composition of human milk, and offers an excellent alternative to mother’s own milk. Even so, some mothers who are unable to supply enough milk themselves for their infants prefer to give human milk from other mothers. Perhaps for the small immunological benefit, or the introduction of infants to food flavors, or otherwise a reluctance to feed infant formula. Human milk banks (for example, the Human Milk Banking Association of America) that screen and test milk donors, and pasteurize human milk to prevent the transmission of infectious agents, are designed to provide milk to at-risk infants such as those in the newborn intensive care unit (NICU) . These organizations generally do not provide milk for healthy infants.
The somewhat risky practice of milk sharing via Internet sites has enabled women with an abundant supply to sell or donate their excess milk to other mothers. On these sites, human milk is sold for around $2 per ounce*, although higher prices are quoted for mothers that only eat organic food, keep kosher or have especially creamy milk. This translates to $60-$70 per liter, which is a great deal more than infant formula or cow’s milk costs. There is a considerable cost motivation to sell more milk. Keim and associates looked at whether human milk purchased online was contaminated with cow’s milk. They bought around 100 samples of milk advertised as human milk via an online breast milk classifieds. Using a PCR assay, the researchers checked whether the milk contained bovine (cow) DNA, and attempted to quantify the amount of cow’s milk in the samples.
The authors found that all samples contained human DNA, however 11% of the samples contained bovine DNA. The majority of the samples contaminated with cow’s milk consistent with human milk mixed with cow’s milk at a 1:1 ratio, or containing at least 10% cow’s milk based formula. The authors discounted the mother’s diet as a source of bovine DNA as levels are likely to be much lower than the levels of contamination detected in this test.
This study shows that although 90% of women appear to be providing the real deal when they sell their breast milk, a small minority appear to be mixing their own milk with cow’s milk. Although the authors mention that this may be inadvertent, it is hard to image women accidentally adding cow’s milk to their breast milk supply and it is likely to be done deliberately. This is worrisome from a public health perspective as cow’s milk is not a suitable food for young infants: levels of protein and minerals are too high and can damage newborns’ kidneys, the protein in cow’s milk can damage the gastrointestinal tract and cause anemia, and increase risk of allergy. This is in addition to the risk of microbial contamination found in breast milk purchased on the Internet, found by the same group in 2013 (Keim).
Although breast is best, unscreened breast milk may not be the best choice for women unable to produce enough milk for their otherwise healthy infant. There is a small yet present chance that it may have been diluted with cow’s milk or formula. Infant formula provides a less expensive and safer option.
* Based on an informal survey of a breast milk classified site conducted April 8, 2015.
Sarah A. Keim, Manjusha M. Kulkarni, Kelly McNamara, Sheela R. Geraghty, Rachael M. Billock, Rachel Ronau, Joseph S. Hogan, and Jesse J. Kwiek. Cow’s Milk Contamination of Human Milk Purchased via the Internet. Pediatrics peds.2014-3554; published ahead of print April 6, 2015, doi:10.1542/peds.2014-3554
de Azeredo VB1, Trugo NM. Retinol, carotenoids, and tocopherols in the milk of lactating adolescents and relationships with plasma concentrations. Nutrition. 2008 Feb;24(2):133-9. Epub 2007 Dec 3. http://www.ncbi.nlm.nih.gov/pubmed/18053685
Arslanoglu S, Bertino E, Nicocia M, Moro GE. WAPM Working Group on Nutrition: potential chronobiotic role of human milk in sleep regulation. J Perinat Med. 2011 Jan;40(1):1-8. http://www.ncbi.nlm.nih.gov/pubmed/22848905
Duijts L, Ramadhani MK, Moll HA. Breastfeeding protects against infectious diseases during infancy in industrialized countries. A systematic review. Matern Child Nutr. 2009 Jul;5(3):199-210. doi: 10.1111/j.1740-8709.2008.00176.x.
Innis SM. Impact of maternal diet on human milk composition and neurological development of infants. Am J Clin Nutr. 2014 Mar;99(3):734S-41S. doi: 10.3945/ajcn.113.072595. Epub 2014 Feb 5.
Keim SA, Hogan JS, McNamara KA, Gudimetla V, Dillon CE, Kwiek JJ, Geraghty SR. Microbial contamination of human milk purchased via the Internet. Pediatrics. 2013 Nov;132(5):e1227-35. doi: 10.1542/peds.2013-1687. Epub 2013 Oct 21. http://www.ncbi.nlm.nih.gov/pubmed/24144714
Mennella JA. Ontogeny of taste preferences: basic biology and implications for health. Am J Clin Nutr. 2014 Mar;99(3):704S-11S. doi: 10.3945/ajcn.113.067694. Epub 2014 Jan 22.
Mohammad MA, Sunehag AL, Haymond MW. Effect of dietary macronutrient composition under moderate hypocaloric intake on maternal adaptation during lactation. Am J Clin Nutr. 2009 Jun;89(6):1821-7. doi: 10.3945/ajcn.2008.26877. Epub 2009 Apr 22.
Szabó E, Boehm G, Beermann C, Weyermann M, Brenner H, Rothenbacher D, Decsi T. Fatty acid profile comparisons in human milk sampled from the same mothers at the sixth week and the sixth month of lactation. J Pediatr Gastroenterol Nutr. 2010 Mar;50(3):316-20. doi: 10.1097/MPG.0b013e3181a9f944.