Why is breastfeeding beneficial for babies and mothers?
Shika Ramanan, Salk Institute for Biological Studies
It is commonly known that breastfeeding benefits the growth of a baby, because the mum’s milk is packed with nutrients, antibodies, and other factors that baby formula cannot replace. These differences, social studies suggest, translate into long term health and IQ benefits for breast-fed babies. But, as we look closer, even more extraordinary effects are emerging: babies mouths talk to breast tissue and can alter the composition of breast milk, whole active immune cells, and even infective organisms transfer between the two, and the breastfeeding mother also sees her health being impacted long term. Shika Ramanan studies breast feeding at the Salk Institute and recently brought all the data together in a big review on the topic. She told me what she’s written about…
Shika – We all know that breast milk is good for you, but we actually don’t really know why it’s good for you and how it’s good for you. And given that this is the first food that most babies receive, it’s important that we have more research on this.
Chris – What does the evidence say, Shikha, in terms of the beneficial effects of breastfeeding, both for the baby, but also the mum? What sorts of trends, when we look at this, do we see?
Shika – For babies, it has the obvious benefit of nutrition. Every mum custom makes breast milk for their babies based on their needs. And babies are able to communicate this with their saliva while they’re breastfeeding on the mum. The obvious benefit, of course, is nutrition and growth, but there are other benefits as well, which includes protection from infections. Mothers provide antibodies in their milk, which can protect babies from developing infections. And more recently, we’ve also been, as a field, looking at how there are immune cells that are in the milk that we think can offer protection to the babies beyond just antibodies. And in addition to that, there’s also several other molecules in milk that can help promote the growth of beneficial bacteria, also known as our microbiome, which are bacteria that live on and in us. And components of breast milk can impact the composition of these beneficial microbes that we have.
Chris – And for the mum?
Shika – Yeah, and for the mum, doctors have been telling mums for years that breastfeeding is beneficial. The WHO tells you that for every year a woman breastfeeds, their likelihood of developing breast cancer, uterine cancer, ovarian cancer decreases, their likelihood of developing chronic heart disease and type 2 diabetes decreases. But we still don’t know how and why mothers have this benefit. And so recent research has been highlighting how there are immune cell changes that are happening to the mum during pregnancy and while they’re breastfeeding. And these immune cells have a positive impact and provide protection and also tend to improve outcomes when mums receive therapy if they were to develop breast cancer or ovarian or uterine cancers.
Chris – So it’s not just the people who breastfeed, and have the time to breastfeed, and are more invested in it and therefore probably also leading a healthier life in other ways, and that’s why they get in these health benefits. It’s not that so much as there is something biochemical going on through the act of breastfeeding that seems to endow the mother with these benefits.
Shika – Yes, I will say that the diet will impact how these immune cells change. However, it does seem to be that these changes in immune cells could be promoting these beneficial effects for the mums.
Chris – The problem is that breastfeeding and modern society are not easy bedfellows. If you ask a woman, she’ll say, I wasn’t prepared for quite how long this was going to take. Some babies seem to take forever to eat their lunch and it’s very, very difficult and you can’t necessarily have a modern life as many people need to live it with a career and invest that much time. So people are resorting to things like express milk and so on. Is that as good? So when we give babies milk that we’ve expressed and kept it in the freezer, for example, which many, many mums will do that, won’t they? Are there any downsides to that or do you get all the same benefits?
Shika – A fed baby is the best baby, right? This is not meant to make women who cannot breastfeed feel guilty about how they can’t breastfeed. Eventually, hopefully all of this research will lead to findings that will benefit not just women that do breastfeed, but also women that cannot breastfeed. But when the baby feeds on the mum, they have signals that they transmit via their saliva. And so that’s how the mums custom make milk for each baby.
Chris – You said that earlier. How does that work? Just if you could, as an aside, because I was intrigued by that earlier, I was going to ask you, how can saliva affect what goes on in the mum’s body?
Shika – Yeah, we actually don’t really know how this happens. What we know is that this does happen, but the science behind how this happens and how the mum is able to custom make this milk is still something we don’t fully understand.
Chris – So you’re saying that contact with baby’s saliva to the nipple tissue is needed and that seems to affect the recipe of the milk.
Shika – Correct. What we do know is that when babies suckle, they form a vacuum with their mouth, which allows for their saliva and things that are in their saliva to enter not just the nipple tissue, but enter the mammary gland itself. And these cues are enough for the mammary gland to respond and custom make milk for the babies. In the case of an infection, say the baby has an infection, you could think about how pathogens are pretty small and so they can make it into the breast tissue and mum is able to respond by providing antibodies to this pathogen, especially if the mum has previously seen or had this infection, then they’re able to provide chock full of antibodies to their baby. However, something that’s always fascinated me is in terms of fat ratio and the composition of the milk, not just in terms of immune components, but nutritional components, how the mums are able to do that, we don’t really know how and what are the cues that the baby’s providing the mum for the mum to be able to do that. This is still an area of active research.
Chris – How easy is it to recapitulate some of these effects so that people who don’t breastfeed can nevertheless benefit their baby? It does sound like, and you’re one of the first people I’ve actually heard telling me this kind of thing, that there is still an ongoing relationship between the breastfed baby and the breast that’s feeding it, that you need that relationship in order to continue the benefits.
Shika – Correct. In terms of nutrition, which is our number one goal, right, for our babies, we want them to be well fed and for them to grow. Yes, formula will do the job and pumping milk will do that job. However, when it comes to immune components, such as antibodies and immune cells in the milk, that seems to require this relationship more. And I do wanna say that pumping milk, keeping milk in the fridge, that still has beneficial effects, right? The antibodies in the milk, they’re going to be fine because they’re resistant to a lot of things, including the stomach acids, right? So they’re able to make it through. However, the physical immune cells are not so hardy. So those might die when you freeze milk and thaw the milk out and so on. In formula, that is really hard to recapitulate because we cannot add some of these immune components, potentially, yes, we’re not adding that yet. But a lot of these immune components that I’m talking about were not at the point where we can add those to formula yet.