Milk: More Than Just Food Milk is not just an ordinary food but a specialized nutritional component containing sugars, fats, proteins, minerals essential for babies’ nutrition. It is a characteristic trait of mammals to use milk to feed their young ones, revealing a complexity beyond a simple childhood treat like cookies and milk. Transcript: Speaker 2 I’m very happy to see you. I don’t think it’s exactly relevant, but I can’t resist saying that we’re almost next door neighbors. There’s one house in between us. Liz is my very good friend as well as a esteemed colleague. Yeah, no, I think that’s a good point to me. All right, so not that disclosure is out of the way. Let me just confess, I don’t know the first thing about milk as a scientific subject. I was shocked as I was doing a little research for this show about just how many puzzles there are still remaining as a little kid when I would come home after school. I’d have milk and cookies. Maybe I’d have peanut butter and jelly. So from that way of thinking about it, milk is just another kind of food. Let’s talk about it first as food. What are the fundamental nutritional components of milk? Speaker 1 The context that you’re talking about was the same way that I used to think about milk. Not that it was food for babies, but that it was just food, something that tasted pretty good. As you get older and you realize how specialized milks can be, especially when you may have an infant that needs milk and you start thinking about human milk, that’s when you realize There’s more to milk than I really thought about when I was having those cookies and milk as a kid. What it really is, it’s composed of things that are needed for the nutrition of babies for a short period of time. And it’s a very characteristic trait of all mammals which use milk to feed their babies. And so when you think about what’s really in it, there are sugars, so carbohydrates, there are fats, there are proteins, there are minerals, and in human milk and many other milks, there (Time 0:02:20)
Understanding the Variation in Breast Milk Composition Breast milk contains information such as small molecules and chemical signals crucial for infant growth and development. The composition of breast milk can vary among individuals, including differences in fat content, antibodies, and the presence of colostrum. Research aims to determine the necessity of these components for infant health and how to optimize baby feeding with this information. Transcript: Speaker 1 There can be saliva information and baby saliva. You can imagine if there was a virus or other particles that are there that might be interacting with the mammary or at the breast. And then also whatever gets put into milk through the milk ducts, so lactation is the production of milk and then the ejection of milk. So whatever is ejected in there is something that potentially the infant is going to consume and then the cells and the organs of the infant can then process that. And some of that we can call information. They may be small molecules or other chemical signals that are really important for growth and development during that period of time. We’re still trying to understand what those are because we want to understand are they necessary for health? What happens when you don’t see some of these signals? And how do we think about feeding babies in the most optimal way with this type of information? Speaker 2 Let’s start exploring some of that. For example, let’s just talk about like variation from person to person. It stands to reason that the ingredients wouldn’t be exactly the same from one person to another. Maybe the fat content would change or the antibodies that get transferred are different. But does milk vary even more than that from person to person? Say over the course of time, over the course of breastfeeding? Speaker 1 Oh, most definitely. The most famous example of this is colostrum. This is a first milk, which is a very high protein dense milk. It looks kind of gold. (Time 0:05:19)
Diverse Factors Affecting Breast Milk Composition Breast milk composition varies between individuals on a daily basis and can be influenced by factors such as diet, regional specificities, and time of feed. Studies have shown that the content of milk can differ based on individual and temporal variations throughout the day, emphasizing the complexity of breast milk composition. Transcript: Speaker 1 And so there’s this biological process that happens that is characteristic of lactation. But to your point, I don’t think we even have our grasp on how much milk can vary between individuals on a day to day. And that’s something that my lab is trying to do. Like if you just look at milk, every single day of lactation, is it very similar or is it changing to many of the life events that may happen during the first six months of life? There have been some really amazing studies that show that diet has an influence. So the particular things that get into milk can be dependent on that. And you can imagine that there are some regional specificities to that that would allow for milks of certain populations to look more similar than other populations. You’ll still see variation, not just across individuals, but there is individual temporal variation throughout the day. There is also time of the feed. So there’s a four milk and there’s a hind milk. Speaker 2 I don’t know those terms, four milk and hind milk. Speaker 1 Yeah, when a baby latches on that feed (Time 0:07:17)
The Multifaceted Role of Molecules in Nutrition and Health Molecules play a diverse role in nutrition and health by serving as building blocks for structural components, communicating information within the body, and acting as chemical signals between cells and microbes. Understanding how nutrients interact with the microbiome is crucial for identifying important microbes affected by diet and determining the resulting health consequences. In the context of infant nutrition, a significant portion of milk molecules are dedicated to interacting with the infant’s microbiome, underlining the importance of these interactions in shaping health outcomes. Transcript: Speaker 1 It seems to have such a multifaceted or versatile role. Speaker 3 You said you can use it as building blocks like structural components. It can be used to communicate information, it can be used for building. You mentioned cell membranes. Cell membranes, really important part of the cell, and I think that you can also say that certain structures of Svingolipids can be used as chemical signals between cells and between Speaker 1 Even microbes and cells in the body. That’s what we’ve really been trying to think about in the case of how do we know where something in the diet goes. My lab has really been trying to think about how do we know which nutrients interact with the microbiome so that we know what are the important microbes that are affected by diet, and Then what are the consequences of those interactions. We have these microbes that may be taking up and transforming these nutrients. What are they making and how does that affect our health? I think that is really important in the infant context because a large portion of milk are molecules that interact with the infants that microbiome. You have estimates that almost 10% of the dry mass of human milk is for communicating with the microbiome and we’re trying to (Time 0:14:42)
Nutritional Recommendations and Long-Term Health Consequences Nutritional recommendations suggest exclusive human milk feeding for six months, followed by the introduction of complementary foods while keeping milk as the main calorie source for some time. Cow’s milk can be introduced at one year, and human milk feeding can continue as long as it works. The long-term health consequences of human milk versus infant formula exposure raise questions about potential impacts like allergic asthma and developmental processes. The importance of creating the right environment for a child’s future success is emphasized, acknowledging that babies are resilient and we often worry unnecessarily. Transcript: Speaker 1 That’s a good question because I think it’s good to orient it. So the recommendations by the World Health Organization and the CDC would be exclusive human milk feeding for six months. And then the introduction of complimentary foods. Different people have different ways that they do it, but still having milk as the main source of calories for the infant for a while. And then the introduction of cow’s milk, potentially at one years old. And then also the encouragement of any human milk feeding if that works for you. So there’s not really a time that you have to cease that necessarily. But I think you’re about to ask me the trillion dollar question, what are the long term health consequences of exposure to human milk versus exposure to infant formula by feeding baby Milk today? Am I starving off allergic asthma in five years? Or are there developmental processes that are really time dependent that are very important? And are those things that can lead to lifelong health? And could we actually determine what those are so that they’re in every single form of infant nutrition? I think about this a lot, about what’s important, even as parents, you think, geez, if I dropped them on their head yesterday, was that important? Or was it not? Or no, they looked that off the ground. Was that important? What are the things that I really need to worry about in terms of creating the right environment for setting them up for success in the future? And the answer is probably like babies are very robust. So we worry maybe more than we should. (Time 0:25:25)
Building a Healthy Foundation for the Future Developmental processes in infancy play a crucial role in shaping lifelong health outcomes, including the potential impact on allergic asthma. While concerns about the impact of small decisions on a child’s future are legitimate, babies are inherently resilient. Although studies linking feeding methods and microbiome composition to health outcomes exist, it remains challenging to draw conclusive long-term effects due to the complexity of feeding studies on infants. Transcript: Speaker 1 Am I starving off allergic asthma in five years? Or are there developmental processes that are really time dependent that are very important? And are those things that can lead to lifelong health? And could we actually determine what those are so that they’re in every single form of infant nutrition? I think about this a lot, about what’s important, even as parents, you think, geez, if I dropped them on their head yesterday, was that important? Or was it not? Or no, they looked that off the ground. Was that important? What are the things that I really need to worry about in terms of creating the right environment for setting them up for success in the future? And the answer is probably like babies are very robust. So we worry maybe more than we should. Speaker 2 And is it too early to answer any of these questions about the long term effects? Is the subject too young or do we have some clues already? Speaker 1 I think there’s some clues. I mean, there are epidemiological studies that have correlations between feeding mode and outcomes or even microbiome composition based off of feeding mode and outcomes. And I think it’s too early because those studies are extremely hard to do. What’s really challenging about some of the studies is that feeding babies is very difficult. (Time 0:26:16)