How many US-based breastfeeding mothers are expressing their milk? The Infant Feeding Practices Study (IFPS) reported that among breastfeeding mothers of young infants (aged 1.5 to 4.5 months) about 85% expressed milk regularly — and often for an extended period of time. Furthermore, 5.6% of US breastfeeding mothers never feed their infants at the breast. Understand, I’m not criticizing mothers who are feeding pumped milk to their babies, I’m just giving the numbers.
We all know that mother’s milk beats formula! However, we don’t know about the possible consequences when feeding pumped milk. I recently interviewed Kathleen Rasmussen, co-author of a study led by Felice. Their paper summarizes some factors suggesting cause for concern, which I will expand and expound upon.
Impact on continuation of breastfeeding
According to Forster and colleagues, women who nurse their newborns at the breast during the hospital stay are more likely to continue breastfeeding until 6 months. (If you understand the physiology and the psychology of breastfeeding, this makes sense.)
Emptying the bottle when feeding pumped milk
Li and colleagues show that when young infants are fed human milk in a bottle, they are likely to empty the bottle. I’ve bottle-fed hundreds of babies, and watched other professionals and parents feed babies. Adults tend to coax the baby to finish the bottle. In essence, the invitation to join the “clean plate club” can start in early life if parents are feeding pumped milk.
Rapid infant weight gain
Not surprisingly, in a later study Li and colleagues saw that infants fed human milk in a bottle had a more rapid weight gain compared to those fed at the breast.
Intake, volume and calories
Infants fed at the breast basically regulate their intake to match their needs. And, in a seminal quantitative study, Wright and colleagues suggest that infants, and not the mother, control the timing and length of feedings at the breast. Even the size of the meal varied, and furthermore, breastfed infants showed a diurnal rhythm which bottle-fed infants did not.
In another seminal study, Heinig and colleagues showed that during the first 12 months, infants took a greater volume and more calories when fed formula in a bottle.
Impact of techniques and temperatures
It’s often difficult to draw clear conclusions about “goodness” or “purity” of stored milk. Collection techniques and storage techniques used, storage times, and temperatures can affect the “goodness” or “purity” in ways that may have consequences. Let me give you a glimpse.
- Are mothers scrupulous in their hand-washing technique when collecting the milk? Big question for mothers plan to feed pumped milk!
- Boo and colleagues showed a high bacterial count in the milk, especially when it was expressed at home (compared to the hospital.) Keim and colleagues also found a high overall bacterial growth and frequent contamination in pumped milk.
- How many times milk is poured from one container to another? Felice and colleagues showed that pumped human milk comes in contact with 2-6 containers. This also affects the temperature of the milk. Might that explain the pathogenic contamination? Quite possibly.
García-Lara et al. analyzed milk samples on the day collected, and again at 7, 15, 30, 60, and 90 days later. They found a significant decline in the concentration of fat and energy content of milk after frozen for 90 days. Similarly, Wojcik and colleagues also found that the macronutrient content differed from that of fresh milk. And, Cooper and colleagues found that storage could reduce the milk’s caloric value by as much as 88 kcal/day. That means that long-term freezing of pumped milk may lower its fat content and energy.
Many who feed pumped milk are unaware that studies also show diminished amounts of Vitamin C, antioxidants, secretory IgA, and much more after long-term freezing. We can’t ignore this. Further, the components of the mother’s milk change over time to match the infant’s nutritional needs.
In short, collection, storage, and handling of milk can affect its nutritional, immunological, and pathogenic properties.
Further, these issues of collection and storage don’t begin to address other issues, such as the effect of the infant’s saliva on the milk, the favorable, friendly oral microbiota or the boost in immunity that occurs with the friendly bacteria on the oral cavity. That’ a post for another day!
Women pump for many reasons. Some women must pump for preterm infants. Some mothers choose to pump for reasons such as travel or job-related issues. So, I repeat: I’m not questioning the validity of the mother’s reason for pumping. I’m questioning if the alteration in nutritional, pathogenic, and immunologic properties are potential — and perhaps modifiable or avoidable — factors to be considered. (Especially for exclusive pumping, or long-term freezing.) I’m questioning the overall impact of feeding pumped milk, including the possibility of kids becoming obese because they guzzled milk from a bottle.
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