From allergies to introducing solids, the first few years of a child's life have a surprising amount of decisions for parents to make.

In the latest entry of "Now What? A Series on Parenting," reporter Chris Schulz spoke with Isabela Negrin, assistant professor of pediatrics at West Virginia University Medicine, about the ins and outs of early childhood nutrition.

This interview was edited for length and clarity.

Schulz: Before a child is even born, how much of a role in the child's health does the mother or the parents' nutrition play in their development?

Negrin: I think while mom is pregnant with a baby, she can take a lot of steps to make some good choices nutritionally, that can kind of help baby down the road. Making sure that she's getting a good variety of nutrients in her diet. And then generally trying to set the stage for the family to have good healthy choices overall and setting the stage for when baby is born, and starts to kind of get into the food eating realm.

Schulz: Feeding an infant historically has been portrayed as formula versus breastfed. You hear the phrase these days a lot, 'Fed is best.' Where does the science actually land on that?

Negrin: Ultimately, like you said, fed is best. We want babies to get the nutrients they need to grow and thrive. That can be obtained via breast milk, via formula, by a combination of both. Ultimately, whatever gets baby the nutrients that they need. The AAP, the American Academy of Pediatrics, does recommend, if possible, breastfeeding at least to the first six months of life. That gives a variety of antibodies and good nutrients to the baby that can help in multiple different areas. But that said, breastfeeding isn't always an option for every parent or a mother. So in that case, formula is a perfectly equivalent option to breastfeeding as well.

Schulz: Obviously we want the child to be healthy, but that can't really happen without a healthy parent. I do wonder about the stress of the pressure to breastfeed on parents. Can you speak to that a little bit?

Negrin: I think there's a lot of stress just from either society, possibly medical professionals, a lot of stress put on parents encouraging them to breastfeed. But I think it's important to find that balance and try to find somebody who supports the parent and what their preferences are and what helps with their personal goals. Whether that's a matter of finding a lactation consultant to work with the parent to give them some tips and help with supporting breastfeeding or just being there for the parents or the family to say, 'It's OK to not breastfeed if this is very stressful for you,' or if milk production is a concern. Like I said, formula is a perfectly equivalent feeding method for babies. So we definitely don't want to put undue harm or stress on the parents and encouraging them to breastfeed when that's not really in line with what their goals are.

Schulz: So before we move on to solid foods, our pediatrician prescribed or suggested supplements, specifically Vitamin D, which is kind of surprising, because as you said the narrative and the thinking is that breastfeeding provides the most nutrients, the most antibodies, just that extra boost. So why is it that in this day and age, we are suggesting that we supplement a baby's nutrition, even when they are being breastfed?

Negrin: Vitamin D is one of the vitamins that's very poorly transferred through breast milk. Even if mom is taking vitamin D supplements, she has to be taking a higher amount of vitamin D supplements for any of that to transfer into the breast milk. That's one of the things that we do recommend breastfed babies do get supplemented. It is in formula. It's actually not in high enough amounts in formula for newborn infants, they're not getting enough vitamin D until they're taking about a liter a day. So we do actually recommend vitamin D supplementation for all babies, not just breastfed babies, but it's kind of more important for breastfed babies because we're not quite getting that transfer through the breast milk.

Vitamin D does get produced through exposure to sunlight and things like that. So there is some talk in some research about babies living in areas with higher concentrations of sunlight. So like Arizona, New Mexico, do they need as much vitamin D supplementation? There's, I think, some research going on about that. But in general, it's not harmful to add that extra 400 units of vitamin D daily.

The other thing, too, that breast milk doesn't transfer well is iron. So usually babies, like term born babies, have enough iron stores until they're about four months old. So they have enough iron until that and then after that, if they're still breastfed, we do recommend supplementing with an iron supplement just because that doesn't transfer well in breast milk either. Until babies are starting to take more solid foods and can take some iron containing foods.

Schulz: You mentioned iron. I've heard that iron rich foods should be the first foods that infants eat when they do start to transition over to purees and solids. Do you have any recommendations on that weaning process and some of those first foods that that children should be trying?

Negrin: It's a good idea, first of all, to talk with your child's doctor because every child is a little bit different. If they're born prematurely, that might affect when you introduce foods. Generally speaking, we recommend starting to introduce foods around six months, sometimes a little bit earlier, depending on the development of the child. In terms of the first foods offered, there's not really like one true best food to offer first. And in terms of purees versus solids, or more solid food, there's a lot of discourse about that as well in terms of like baby led weaning versus starting with solely purees. In terms of starting with meats and things like that, there's nothing totally off limits about starting with meat. I think texture is going to be kind of a big thing, especially for younger infants. You want to make sure that it's something that they can developmentally manage and swallow, but in terms of totally off limits foods when starting it's really just no honey and no cow's milk. Other things like eggs are totally OK to start in that six months early food introduction as long as it's small and easy to manage or pureed.

Schulz: We do hear that term a lot these days, baby led weaning. Can you define that for us? What exactly is baby led weaning?

Negrin: I think there's probably different definitions based on who you ask. But in general, it's allowing babies to kind of self-feed rather than the traditional scooping some puree out of a jar and spoon feeding it to baby. It's kind of putting these foods out on the highchair on the table for the baby to self-feed. The thought is that they will tend to eat things that they're developmentally ready for, and then kind of progress as they go. When this first started getting traction, I think there was a lot of questioning of 'Are they going to be getting enough nutrients from it,' or the choking risk. So the choking risk has kind of been a little bit debunked with the few studies that have been out. And they found that babies who do that do get about equivalent amount of calories, there's still definitely a role for purees. And baby led weaning is just a matter of feeding baby what the family is eating, just maybe in smaller chunks or broken up more mashed up more and allowing baby to feed themselves rather than being spoon fed everything. So it kind of helps with their development as well.

Schulz: Let's talk about allergens for a second. I have heard that the advice specifically around peanuts has changed and we want regular exposure now, which was not what it was even 10 years ago. What are the recommendations these days on introduction of allergens? Where should that be done? And how often should it be done?

Negrin: You're right, there's been a lot of recent research and changes about especially just peanuts. In the early 2000s, there was an observation study that found that infants in Israel had a lower prevalence of having peanut allergy. That's because one of the popular snack foods for infants in Israel is bomba, which is like a corn puff that's made with peanuts. So they found that the early introduction of peanuts, and then that kind of spurred multiple studies after that, but the earlier introduction of peanuts did show a correlation with less peanut allergy overall. So in general, the recommendation is, if baby has no concern for eczema or any other kind of allergy, it doesn't really matter when you introduce the allergen food, so peanuts, eggs, things like that. It's totally OK to introduce it early, as long as it's something that is not a choking hazard. So creamy peanut butter instead of, obviously, offering peanuts.

And then, if a baby has some mild eczema that's pretty well controlled, or there's a family history of eczema or food allergy, then we do recommend introducing allergens early rather than later. Introducing around that six-to-seven-month period, with a small amount, you can do baby cereal with a tiny little bit of peanut butter and just kind of offer that to baby, kind of see if they have any kind of rash or anything like that. The only exception is babies who have very, very severe eczema, I do recommend talking to your doctor about that. because there may be a recommendation to either get them tested before trying the food, or possibly trying it in a doctor's office, in a setting where if there were to be anything that happened that action can be taken.

But in general I think it's a good idea to start introducing those foods earlier. And then in terms of frequency of introducing, I usually recommend waiting when you're introducing a new food, wait three to five days before introducing a new food. That way, if there were an allergic reaction or a rash that happens from that food you know exactly what caused it rather than kind of trying to play a guessing game of oh, we offered two or three foods, and we don't know what caused it.

Schulz: You've mentioned choking hazards, you mentioned texture for young children. Watching the development of that gag reflex is so scary. I think that can kind of be unexpected to people when children are entering the phase where they start to eat solids that you kind of have to let the child gag a little bit. What are your recommendations to parents to make that transition a little bit easier on them?

Negrin: Right, so that can be very scary, the gagging and kind of figuring things out with the textures. You have to understand that babies spent their entire life up at that point just drinking liquids. So having a solid in their mouth is a different texture. It's a different feeling. I will say babies in general, unless they have any developmental concerns, they do a very good job about protecting their airway. So before you get to any concern about choking or things like that, they will kind of do their best to kind of either spit it out, gag, kind of make those coughing noises, but it can be very scary for parents. So in general, I recommend when introducing foods to always be supervising the baby, always be right there next to the baby, make sure that they're supported, like in a highchair, where they're not risking kind of falling over, or things like that. And then I do recommend parents to get a CPR class or CPR training just in case something were to happen, that they have the training to help if needed.

I think there has been a big rise in the last decade or two about baby led weaning happening more frequently and the recommendations of that there's not, just like with breastfed, breast milk versus formula, I don't think there's one correct way to introduce foods, whether you want to start with purees, whether you want to start with more like, quote unquote, regular food, or do a mix of both. It's really just kind of making sure the baby is supervised, and in a safe environment to eat. And then, just because it is relatively new, and because research and pediatrics is also relatively slow, there's not a whole lot of research out comparing baby led weaning versus pureed foods. But the research that is out shows that there's really not a significant difference within choking between both methods.