Breast Feeding and Health - A Biological Perspective

Prof Jose Saavedra: Professor Lucas, we’ve been talking today a lot about ways that we can improve infant nutrition especially in early life, and certainly one of the approaches that we’ve taken scientifically, and nutritionally, is using breast milk as a model. In what ways, do you think we should use breast milk, and how has it served as a model for defining what is the best approach for nutrition in early life?

Prof Alan Lucas: If we looked at what was in breast milk it would tell us what we need to feed babies in infancy – for instance the design of special feeds for babies and babies who are sick, and we get a feel for what is normal nutrition. By the 1960s, there have been about fifteen hundred publications on the composition of breast milk; however, despite all that work, it really didn’t give us an accurate view of the dietary intake of the breastfed baby. The reason for that is that one of the main components of breast milk, the fat, which determines how many calories there are in breast milk, is extremely variable during the course of a feed, and the baby will often leave high-fat hindmilk behind in the breast after a feed. It is very difficult to take samples of breast milk that would represent what the baby actually consumes; expressing breast milk might misestimate the amount of fat and energy quite substantially if the baby were to leave high-fat hindmilk in the breast at the end of the feed. Hence, we decided to look at this in some rather unusual ways. We attempted to measure milk flow and milk composition continuously during a breast feed and we found that previous estimates of the amount of fat in breast milk obtained by expressing milk had a 60% margin of error. Now, we’re getting a better feel of what is the dietary intake of a breastfed baby. Infant formulas in the past were modelled on what people thought was in breast milk, and therefore had too much energy and protein, driving faster growth and putting children at risk for having obesity in later life. Now, we have better data on what the dietary intake of a breastfed baby is and that’s a better model for all sorts of purposes, including making better infant formulas.

Prof Jose Saavedra: What are the clinical outcomes or benefits that we can or should expect from more and longer breastfeeding, and from any kind of substitute considering the functional effects of the composition of infant products?

Prof Alan Lucas: It is impossible to mimic breast milk in an artificial product because breast milk has so many components that are essentially un-mimicable, like for instance, live cells and very complex array of substances that would be very difficult to capture. Breastfeeding is always going to give us a better result from the point of view of health outcomes. Having said that, it is difficult to prove the many different health effects that breastfeeding is thought to have because data come from observational studies; we can’t assign babies to breastfeeding or bottle feeding randomly as one would in a clinical trial, and there are things that interfere with our interpretation of the results. For instance, it is generally known that brighter mothers tend to breastfeed; so if breastfed babies turned out to be brighter than formula-fed babies, you wouldn’t be able to tell whether that was due to the mother’s intelligence or whether it was due to something in breast milk.

We have had to think about ways in which we can test more rigorously what is and isn’t benefited by breastfeeding. One of the ways we’ve done was to conduct randomised trials in  premature babies and we found, for instance, that a large number of studies demonstrate that in the care of premature babies, human milk confers better protection against infective processes than formula. This makes the data in full-term infants more convincing, because although these were not based on randomised trials, we were getting exactly the same findings in premature babies.  From here, we could run through all the other different outcomes, like allergy, brain development and IQ and so forth, and there have been several experimental studies in premature babies that actually gave us answers. We now appreciate that a lot of things that are shown to be related to breastfeeding are almost certainly actually caused by breastfeeding and that’s very good for health promotion. This is going to be important for organisations like WHO and government departments and the global promotion of breastfeeding.

Prof Jose Saavedra: Does it mean that placing more emphasis on early life nutrition and the way that we manage nutrition, particularly in premature babies, can give us great return on the investment that we are making today?

Prof Alan Lucas: Absolutely. I think that this is a critical period. I’ve devoted much of my research career to looking at the impact of nutrition in early life on long term health. I’ve called this process ‘programming’ – the idea that you can be programmed by your early nutrition for the diseases you get in later life. This has been well known for at least 80 years in animals but we did some of the first randomised trials to show that this was also true for humans. The exciting thing is that relatively brief critical periods in early life can be used as an opportunity for us to intervene to totally change population health in the long term. So, it’s a very important time to focus on and it’s actually economically sensible to do so because it’s a period of time that doesn’t require very much resource, so it’s actually relevant to developing countries as well as developed ones.

Prof Jose Saavedra: A lot has been done, and still lots to learn. Thank you very much Dr. Lucas.

Prof Alan Lucas: Thank you.

* Currently, Dr Jose Saavedra is holding a position as Associate Professor of Pediatrics, Gastroenterology and Nutrition.  The Johns Hopkins University School of Medicine


View the video recording of this interview here.