Ever wonder how children develop preferences for certain foods? Why in the same family, different children may like different things? Why some people have trouble controlling what they eat and others think a little about food that they have trouble eating enough? These are some, but some of the questions that occupy The Leading Voices in Food guest Dr. Marion Hetherington.
About Marion Hetherington
Dr. Marion Hetherington is a professor of biopsychology at the University of Leeds in West Yorkshire, England. Marion studies human appetite across the lifespan from infancy on. She's particularly interested in what we can learn from the way that infants and young children express their hunger and satiety, how they develop food preferences and how mothers respond to children's appetite cues. She runs the Human Appetite Research Unit at the University of Leeds where her team takes a lifespan approach to studying the appetite and aging. Such research includes topics such as triggers for overeating and in young adults, how young people respond to environmental pressures to overconsume and managing malnutrition at the end of life.
A topic of considerable interest in the field now is responsive feeding, and you've done some seminal work on that topic. Can you explain the concept of responsive feeding?
Yes, responsive feeding is really just an example of responsive parenting where parents respond appropriately and quickly to the child's needs. So it might be that a child is indicating hunger and so responsive feeding would mean that that parent would respond by feeding, but responsive feeding also means picking up on those cues regarding satiety. And we found in our research that parents are very attuned to hunger because hunger calls as hunger cries are very distressing, but with satiety, they are more subtle and parents don't always listen to their child because they're worried about waste on the plate. And also some parents don't really believe that their child is capable of nutritional wisdom, and I think some parents think they know best. So responsive feeding is really a hot topic at the moment. It's something that we're very keen to understand more, but we're really just at the beginning of our studies.
So a parent that might believe that whatever is on a plate is what a child could should consume or whatever is in a bottle, if the child was bottle feeding? And rather than the child determining when the shutoff should occur, the parents are determining that. Is that what response feeding is hoping to overcome?
Yes indeed. So if you think about the typical breastfed baby, it's really very difficult to overfeed a breastfed baby because, generally speaking, moms are very attuned to their baby's feeding from the breast. And, they recognize that sometimes babies will come to the breast because they're thirsty. Sometimes it's because they're very hungry and sometimes it's just for comfort. So mothers are very aware that when they have the baby at the breast, it might be for one of these many reasons. Whereas with bottle feeding, as you've just said, there's a kind of visual cue to mom that there's a lot of milk within that bottle and the tendency is for moms to encourage their baby to complete that bottle. But this doesn't mean to say the all formula fed babies on not fed responsively, but rather that their mothers can be sensitive to portion size and may not trust their baby to tell them when they've had enough. But I think that when we think about low-income families, when we think about moms on a budget, it is tough to realize then that actually--maybe the baby was just a little bit thirsty or a little bit grumpy. And we need to put that bottle aside. So you then we need to, you know, get rid of that bottle because that can’t be used again.
And similarly with a plate of food. Moms or dads and might present a plate of food thinking that this is appropriate portion size. But babies' appetites might change and it is okay if maybe say that they've had enough. The way that they say they've had enough is actually quite subtle, and parents need to really tune into that and trust that their baby's know what they're doing.
So what are some of the subtle cues a parent might be coached to learn that the child might display?
Well, certainly in terms of offering a food with, say a spoon. Baby's will accept the spoon readily when they're hungry, and in fact, babies might lean forward in anticipation of getting that spoon full of food. But after a few spoonfuls of that food, if they start to gaze away from the food, if they start to be interested in something else that's on their tray, such as a toy or the tray itself, the baby's gaze is shifting away from what they're interested in. Which suggests to us that they're beginning to show signs of satiation. And then if mom persists in feeding with the spoon, baby maybe might start to use much more obvious behaviors like turning the head away when food is offered or pushing the spoon away. They may even become tearful because that's communication of distress if they feel that they've had enough of that food and they don't want anymore and they're not really being listened to. So I think the cry is kind of an endpoint that not many babies get to. But certainly, we've often seen parents using a kind of mini airplane to give their babies a spoonful of food. If the babies are turning away they're not interested, then trust that baby had enough.
This must be hard for some parents, I can imagine if they're worried about their children are getting enough food.
Absolutely. And in the cases where children are weight faltering, and they're not making appropriate weights--and of course parents are going to be very worried and they really need to seek clinical advice. But, when a baby is being a little fussy or when a baby normally has a good appetite but it is not eating that day, I think that moms and dads need to be sensitive to what the baby is saying. What we've found is that in our research, parents really hone in on hunger. They're very aware and very adept at listening to hunger signals even when it's just at the early stages such as when babies are rustling in their crib or their begin to get a little bit agitated. Parents will respond. And yet with satiation or satiety, we see parents persisting because they think it's the right thing that their baby should eat this amount or this type of food that they're very keen for them to try. But babies vary so much in relation to their eating traits. Some babies are more fussy than others. Some babies are more attuned to their own satiety cues than others. And, some babies will vary in eating enjoyment just as you said earlier. There are some children who are just not that interested in food. And yes, it's a challenge for parents. But, if there's a repertoire that they know that babies will consume, those are the foods they ought to be using, as long as it's a variety.
Is there enough research yet to know whether parents can be successfully coached to read these cues and then whether a change in their parenting practices will affect the diet and health of the children?
Well, there's a World Health Organization report, I think it's from 2006, where they define responsive parenting. And in that report, they say that there are interventions to encourage parents to be more sensitive, more responsive to their children. And this can actually promote cognitive development, psychosocial developments, and health. So in a broad sense, the answer is yes, parents can be coached, and parents can be given some guidance about how to read their children. However, the question you asked might be specific therefore to feeding, and as far as I'm aware, there are fewer studies looking at responsive feeding. But if we think about trials such as Insight Trial at Penn State University or the Nourish Trial as to the Queensland University of Technology in Australia, both of those trials have used weekly groups with parents to help them to understand their child's communication better. And in both of those examples, they do show that parents are very amenable to be coached in this way.
Turning our attention to vegetables and encouraging children that eat them in particular, I suspect nearly every parent can relate to the struggle of encouraging children to eat and love vegetables. Part of your work focuses on how to promote vegetables in early life feeding experiences and during the preschool years. What would you most like people to understand about feeding children vegetables?
I guess if there was one message that I'd want to convey from our research it's that vegetables are actually a very good first food. So when moms are ready to introduce their little one to solid foods for the first time at six months, vegetables are a really good food to use. That's because six months and just beyond at complementary feeding time, young babies are really amenable to these new tastes. But if you try to introduce vegetables a little bit later on, so for example, at school age, then it's more tricky. So any of the studies that we've looked at where we're looking at when to introduce vegetables, the best time is around a complementary feeding and then to encourage a variety of different vegetables. Parents need to model vegetable eating because in their household, if vegetables aren't typically eaten, then the little ones are not going to really be encouraged to eat the vegetables if they don't see it around them. So we would say early on in life and, in fact judging from the studies by Julie Menella at Monell Chemical Senses Center in Philadelphia, her studies show that really moms could be eating vegetables during pregnancy and that those flavors, some of those flavor components, are transmitted to the fetus. Therefore we would even say start complementary feeding with vegetables, but also eat a lot of vegetables in pregnancy because we know that some of those volatiles from the vegetables are being transmitted in utero.
Are there certain vegetables that make sense for parents to begin with? If they're introducing them early?
I think a lot of parents are very keen to use the sweeter vegetables like carrots and sweet potato. However, we would say that from our research, the more sulfurous vegetables and metallic vegetables like green beans are really good starting vegetables because these are the sorts of vegetables that need a little bit more exposure. So if you think about the sweet vegetables, babies are born with an innate liking for sweetness because breast milk is sweet. And therefore it doesn't take a lot of encouragement for a baby to like a vegetable that has a sweet note. Whereas those vegetables are a little bit more bitter, they're the difficult ones. But at six months and a little bit beyond that at complementary feeding babies are very amenable to try these because they have no expectations. They don't yet have any learned dislikes.
Bitterness is generally rejected in early life, but the bitter taste can be acquired through exposure. So we find in our research that between five and six exposures to vegetables such as green bean or broccoli will encourage the child to like that vegetable. Some children will need 10 exposures. But our message is always around encouraging parents to be persistent and to be patient and not to give up. One week, they don't like Broccoli, nevermind. Try again next week, but always try because we think that with repeated exposure comes a liking for the vegetable through familiarity.
It's interesting that this was both a biological and a social process isn't it. The mother's diet during pregnancy being influential, but of course what the parents eat themselves and what they introduced to the children kind of all fits together into this really amazing picture of how children could come to like fruits and vegetable. It's really very impressive.
Well, I think biology is very important because obviously babies are born with the capacity to like sweetness. The beautiful studies by Yacob Steiner in the 1970's showed us that newborn babies, even before they'd had their first exposure to colostrum or breast milk, when they were given these pure tastes, such as sweetness or sourness through citric acid or bitterness through quinine sulfate or saltiness through sodium chloride, babies already have a positive liking for sucralose in solutions. They already like sweetness, so there's no learning needed to acquire preferences for sweet vegetables or fruits. But something that's slightly bitter will take a little bit longer. And we have done studies where we've actually tried to add sweetness to some vegetables, so we had the artichoke as an example, and we've added a little bit of sweetness to artichoke or a little bit of oil to artichoke to increase its energy density. And in both of these cases, there is no additional benefit of adding any sweetness or adding any oil because children acquire liking for artichoke as for any other vegetable through mere exposure. And there's no need to add that biological imperative of a sweet taste. It's not needed.
You worked on as the genetic risk for obesity in children, and you've done work especially with FTO risk allele and child eating behavior. Could you describe that work?
So this is a research going back more than 10 years now. Basically we had a large cohort of children in the northeast of Scotland and we were able to genotype the children looking at the FTO allele. What we found was that the children who carried the risk allele were heavier than the children who did not show that allele. And then when we studied them in a little bit more detail, we find out that those children who carried the FTO risk allele were less likely than the other children to compensate appropriately for a preload. So it's hard for those children to compensate for a large preloads given in midmorning. And we also found that they tended to eat more overall even when you adjust for their energy expenditure. So this research is basically saying that some children have a predisposition towards perhaps eating a little bit more than their counterparts, their peers, and that can be managed. Because in Swedish studies where they have these very large populations, they can look at the FTO risk allele in the population and those who carry that allele, but who exercise and who have a diet that has lots of low energy density foods. Those individuals are protected against overweight and obesity. So we're looking at the genetics of obesity. We're looking at predisposition, but we're not looking at destiny. So just because those risk alleles are carried, doesn't mean to say that the children will have overweight or obesity as they get older. Basically looking for those appetite traits where the child is hungry or really very interested in food is a kind of signal to us to be cautious around how we treat the child. We need to make sure that they're eating lots of low energy density foods which are very filling, high in fiber, rather than the high energy density foods which are very palatable, but they deliver a lot more energy per gram.
That's not easy to do in this environment where those sorts of foods are engineered to be so palatable. They're so highly marketed, aren't they?
That's true. It's very difficult and it doesn't really help. In the UK, we use high energy density foods as treats. So we just had Halloween. It's been really interesting. At my door I had 30-40 kids and I offered a tangerine as well as Halloween candy. I did my own little mini-experiment-- and of course the children--they'll choose both, but they really go for the candy. First of all, because it's so palatable and there's a biological component to that. We know that they're very sweet, very energy dense, and therefore very attractive. So you're right, it's very hard for kids to resist these foods and the culture that we live in promotes this idea of these foods as treats. But in a sense if the kids are eating them every day, they've lost that identity as a treat.
So I think this is a really complicated social issue, and I can't really speak to the major drivers in relation to confectionary or these other highly palatable foods, but what I can say is that some children are more interested in those stimuli than others. And we can see that really early on because we know that certain eating treats are highly heritable, such as low satiety, responsiveness, high enjoyment of food. And I guess what we have to think about is both tackling an obesogenic environment but also preparing our children by offering them a healthy balanced diet from the very beginning. And particularly I would say ensuring that they really like the variety of vegetables.
If you could peer into the future, what would be your guess about what some of the most exciting work will be around these issues?
I think in terms of future trends, the use of phone apps is very exciting to me. Because of the comfort of your handset, your smartphone, you have the opportunity to introduce vegetables into the diet and have a way of kind of monitoring food intake and personalizing nutrition using smart apps. And I think that of course this is already with us, it's not really peering into the future. But I think that in the future we will become more reliant on technology such as this to help guide us in terms of encouraging us to be more physically active, to encourage us to eat a better diet. But you know, that's always down to motivation, isn't it? So I'm a psychologist, and ultimately I will say that it's always going to be partly to do with the individual and partly to do with how they interact with what's available to them. But I'm very excited about apps for moms both for pregnancy so that we can look at dietary interventions really early on in the life of the fetus and then making that start for good healthy eating really as early as possible around the time of conception in fact.
Produced by Deborah Hill at the Duke World Food Policy Center
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