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Shaken Or Stirred? How Does Handling of Breastmilk Impact Composition? Guest Post by Sue Cox, IBCLC


Incorporating new evidence-based information about putting lactation into practice is a critical component of the role of the IBCLC.  As additional information becomes available, it is a challenge to place it in the context of what has already been established both in the field of lactation and in the broader fields of anatomy and physiology. 

Our guest blogger Sue Cox, an IBCLC since 1985 and the author/presenter of over 80 papers, addresses the research in hot topics in the IBCLC profession today, including questions about breastmilk composition when shaken, agitated, or left in the breast between long feedings. Watch for part two of this post next Wednesday where she will share her reflections on the research on other commonly asked questions about breastfeeding.

On Listening, Then Reviewing/Pondering What We Read and Hear

In this blog post, I will be commenting on some of the discussions I have read on the Internet and heard in professional conversation lately. I hope these quotes – on which I have based my professional life as an IBCLC – will help guide your thinking.

. . . Continued learning requires that we seek new knowledge and [accept] the challenge that takes place when our own interpretations on ways of doing things are questioned by others. That is the price we must pay if we are to hone our skills, increase our knowledge and strive to keep to the best of our abilities for those women who seek our assistance and depend upon us for guidance.

Kathleen Auerbach, (1987) J.Hum Lact 3(4).

Receptiveness to what we hear is vital, but what we hear needs always to be backed up by physiological/biochemical/ anatomical/endocrinological and/or psychological understandings.

Sue Cox 2014.

Note from the editor: Much recent research has addressed how best to handle expressed human milk, with the goal of maintaining the integrity of the milk components and more evenly distribute the components within the liquid. This has, in turn, generated conversation about ways to more evenly distribute nutrients, especially human milkfat, throughout milk during breastfeeding. Read on for the research that Sue provides to further discussion in each of these areas.

Will agitating a syringe of expressed breastmilk for infusion to premature infants homogenize the milk?

Ultrasound has previously been shown to homogenize cow milk (Ertugay & Sengul, 2004).

Ertugay, FM, Sengul, M (2004) Effect of Ultrasound Treatment on Milk Homogenisation and Particle Size Distribution of Fat. Turk J Vet Anim Sci 303-308.

In the recent study by Garcia-Lara and colleagues (2014) the researchers sought to extend knowledge of the most appropriate routine to decrease fat loss in infused expressed breastmilk for premature infants. The word homogenization occurred in the title: “Type of homogenization and fat loss during continuous infusion of human milk.” Three methods were used to mix the milk in the syringe: baseline agitation, hourly agitation and ultrasound. The first two methods simply reconstituted the milk but did not make every drop the same as in homogenization. 

Garcia-Lara et al., (2014) Type of homogenization and fat loss during continuous infusion of human milk. J Hum Lact  0890334414546044, first published on August 13, 2014 as doi:10.1177/0890334414546044.

Could shaking the breast homogenise milk?

Breastmilk in the alveoli is a suspension of fore- or skim- milk with small amounts of fat suspended in it, but most of the fat is bonded to the epithelial lining of the alveoli.

If breastmilk were to be homogenised it would require a “factory setting” in which it would be altered from a suspension to an emulsion where every drop would be the same.

Homogenisation is a process in which the fat droplets are emulsified and the cream does not separate

Even after centrifuging, all of the fat globules do not separate and fat is seen in the skim fraction of the milk (Czank et al, 2009)

Czank, C, Simmer K, and Peter E Hartmann, PE  (2009) A method for standardizing the fat content of human milk for use in the neonatal intensive care unit. Int Breastfeed J. 2009; 4: 3.

Could shaking the breast or breast massage increase the fat content earlier in the feed?

Whittlestone (1953) hypothesised that the fat globules adhered to the walls of the alveoli and ducts.

Whittlestone WG (1953) Variations in the fat content of milk throughout the milking process. J Dairy Res 20: 146–153

Foda (2004) found that when samples of expressed milk were taken within 30 minutes  before Okatani massage and then the breast was fully hand expressed after massage that there were increased fat levels in the post-massage breastmilk but this only occurred after lactation was well established which in that study was after three months. No reference was made to the effect that the massage may have had on milk ejections occurring which increase fat levels in milk, nor was there mention of degree of fullness or time since the previous feed.

Foda et al., (2004) Composition of milk obtained from unmassaged versus massaged breasts of lactating mothers. J Pediatr Gastroenterol Nutr.;38(5):484-7.

Morton et al (2012) found that when mothers who were expressing for their premature babies used hand expression and breast compression during pumping that their milk exceeded normal fat and energy levels after the first week postpartum.

Sue notes here that the breasts would have been well drained at each expressing and pumping session.

Morton J, et al., (2012) Combining hand techniques with electric pumping increases the caloric content of milk in mothers of preterm infants.  J Perinatol. 32(10):791-6

Would altering breastmilk so that the infant received creamier milk earlier in the feed be an advantage to the baby?

Karatas (2011) suggested that the weight patterns in healthy breastfed infants at their second and fifth months is based on the satiety from changes in breastmilk ghrelin, leptin, and fat levels between the foremilk and hindmilk.

Karatas Z et al., (2011) Breastmilk ghrelin, leptin, and fat levels changing foremilk to hindmilk: is that important for self-control of feeding? Eur J Pediatr. 2011 Oct;170(10):1273-80.

Various theories have been suggested about how/why the fat detaches including: the decrease in surface area as the alveoli are being drained of milk during a feeding (Atwood & Hartmann, 1992; Neville, Allen & Watters, 1983; Hytten, 1954); the effect of hormones oxytocin and prolactin and/or alteration in gene expression as the alveoli is drained (Hassiotou et al., 2012; Hall, 1979) .

Atwood CS, Hartmann PE (1992) Collection of fore and hind milk from the sow and the changes in milk composition during suckling. J Dairy Res 59: 287–298.

Neville MC, Allen JC, Watters C (1983) The mechanisms of milk secretion; Neville MC, Neifert MR, New York and London: Plenum Press. 49–102.

Hytten FE (1954) Clinical and chemical studies in human lactation. I. Collection of milk samples. Brit Med J 23: 175–182.

Hassiotou F, Geddes DT, Hartmann PE (2012) Cells in human milk: State of the science. J Hum Lact 29: 171–182.

Hall B (1979) Uniformity of human milk. American Journal of Clinical Nutrition 32: 304–312.

Does milk separate in the breast if there are long gaps between feeds?

The greater portion of the milk is stored in the alveoli until required (Geddes, 2009). High-resolution ultrasound images (Geddes, 2009) show the flow of milk as the ducts dilate in the breast following oxytocin-mediated milk ejection (shown by flecks in the milk in the duct as the milk is ejected as well as in the infant’s oral cavity). When milk removal ceases the residual milk returns to the alveoli.   

Geddes D (2009) The use of ultrasound to identify milk ejection in women – tips and pitfalls. Int Breastfeed J. 2009; 4: 5. doi:  10.1186/1746-4358-4-5

Hassioto et al., (2013) found that when milk was expressed before, after and then at 30- minute intervals for three hours after breastfeeds that the highest fat levels were found 30 minutes after the end of milk removal. This supports the utrasound findings of Geddes (2009) that showed how residual fat returns to the alveoli after milk removal.

Hassiotou F, et al., Breastmilk cell and fat contents respond similarly to removal of breastmilk by the infant. PLoS One. 2013; 8(11): e78232. Published online Nov 6, 2013. doi:  10.1371/journal.pone.0078232

In conclusion, the suggestion that homogenization can be achieved by simply shaking or agitating breastmilk in the breast or in another receptacle is an incorrect use of the word homogenize. The use of the word homogenize in the context of human lactation and breastfeeding requires scholarly review.

Watch for Sue’s next guest post, where she presents the research on other key areas of breastfeeding practice today.

15 Responses to Shaken Or Stirred? How Does Handling of Breastmilk Impact Composition? Guest Post by Sue Cox, IBCLC

  1. Deirdre Leslie 9 September 2014 at 04:27 #

    Thanks for a thought-provoking article. The first question “Will agitating a syringe of expressed breastmilk for infusion to premature infants homogenize the milk?” left me pondering whether fat globules adhere to the walls of a plastic syringe more readily than the rest of the EBM. If so, theoretically babies being tube/syringe fed might be deprived of some of the fat. Is there evidence that agitation of the syringe is helpful, or might it actually damage the EBM components? Does anyone have further information about this?

    • Sue Cox 11 September 2014 at 19:38 #

      Yes Deidre fat does adhere to the walls of plastic syringes. The first article: Garcia-Lara et al., (2014) Type of homogenization and fat loss during continuous infusion of human milk. J Hum Lact first published on August 13, 2014, as doi:10.1177/0890334414546044. was to study which of the three options made a difference to the fat adhering to the syringe. Agitation does need to be gentle otherwise other components in breastmilk can be damaged.

  2. Karen Foard 9 September 2014 at 06:40 #

    This is exactly the kind of email I love to open, and exactly the kind of ongoing bits of professional development that LC’s need. While the topic is an excellent choice for learning (and I love the Auerbach quote), the best part of this entry is that it is a combination of research summarizing and application surmising that gets my brain cells working. When done by a reputable practitioner like Sue, the presentation should be reliable and trustworthy in its ability to be applied – and indeed used for clarification in our practices. I have found more and more these days as a 26 year IBCLC that I continually raise questions about what I have ‘known’ for years and years, and this kind of practical information hones my knowledge base. ~Karen Foard, a happy IBCLC at 630 am

    • Sue Cox 11 September 2014 at 19:58 #

      Thank you Karen

  3. eurolacpuntnet 9 September 2014 at 09:31 #

    Nice overview that may serve lots of colleagues and their clients well. Still, I was rather disappointed when reading. The title suggested that the essay would discuss the ”stirring vs shaking of stored milk” dilemma.

    • Sue Cox 11 September 2014 at 19:44 #

      The original title was a little less catchy and the new one was to catch the readers attention. I was stirred to write the piece after hearing that mothers are being encouraged to ‘shake the breast’ or ‘provide a milk shake for the baby’. Jargon in a profession is not helpful and I think the ‘milk shake’ jargon certainly needs the professions attention.

  4. Elizabeth Yip 10 September 2014 at 05:43 #

    what to do with expressed milk which may or may not be able to be homogenized. ( us oldies remember that homogenization is a relatively new process). In the breast however mother nature intended baby to do what comes naturally without watches or the knowledge that the beginning of the feed is full of protein for growth and a little creamier at the end . When I talk to mothers they laugh at the thought of shaking breasts prior to or during a feed. they know their breasts don’t work like a milk shake maker.

    • Sue Cox 11 September 2014 at 19:44 #

      Love your post Elizabeth

    • joyheads 11 September 2014 at 20:41 #

      Yes, Elizabeth I agree with your comments about shaking the breast, An additional concern would be possible bruising of breast tissue if done too vigorously. As we all know many new mothers take suggestions to the nth degree,

  5. Christine Cheney 10 September 2014 at 08:29 #

    Thank you Sue for this information. I look forward to next week’s blog. Does anyone have information on the odor that some batches of frozen PDHM have, presumably due to the lipase content. Some of the special care nursery RNs have been concerned about this odor and I would like to address their concerns with a research article or other information.
    Thanks again Sue.

    • Julia Gragg 22 September 2014 at 08:59 #

      I am hearing from many mothers who only occasionally try to give their infant previously frozen human milk, the infant will not take it. The milk has a distinct odor. Is there anything in the literature regarding how this might be eliminated. I have found that mothers experience this problem whether the milk was stored in glass, plastic bottles or plastic bags. 100’s of oz of frozen breast milk is being thrown out!

  6. Sue Cox 11 September 2014 at 19:57 #

    Have you read this article Christine? :
    It may give some insight when considering the fat loss while human milk is frozen.

  7. Alice Farrow 14 September 2014 at 12:22 #

    Sue, could you provide further information on how agitation can damage the other components in breastmilk? It is a discussion that comes up frequently in parent forums.

    • Sue Cox 15 September 2014 at 21:01 #

      Thank you for your question Alice. I have spent some hours searching for the answer. I can certainly find a myriad of sites and texts where it says gently swirl/gently shake etc. but none of them are referenced. Early studies 30-35 years ago talk about the loss of lymphocytes and leucocytes but do not say that this loss could be decreased by any specific care of EBM. Both of the following abstracts talk about cellular loss:
      I am unable to access the full papers.
      I would love someone else to come up with the research.

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