Neonatal Caloric Requirements: A response to the FIB-ers post about stomach volume

Neonatal Caloric Requirements

Selia asked me an interesting question about a recent post from the FIB folks about neonatal stomach volume.  It seems that J. Seagrave RN, IBCLC wrote a provocative piece about how our neonatal stomach volume models of the marble and the nut, and egg are not evidence based and therefore everything that we think we know about neonatal feeding is wrong.  As we usually find on the internet she is half-right, and biased, but she makes a very good point.  Our neonatal feeding estimates are probably wrong and our understanding of neonatal feeding in the first 48 hours is almost certainly wrong, but that doesn’t mean we have to change anything.  It also doesn’t mean that the babies are starving or suffering either.  To defend this, I’ll use basic nutritional theory and a little microbiome science for back up.  So, let’s dive in and I’ll tell you what I have discovered.

First, Seagrave is 100% correct, the estimate of neonatal stomach volume that suggests a size of 5-7 mL are not measures of actual stomach volume, they are a mathematical calculation where researchers took the average 24-hour intake and divided by number of feeds and came up with a number that is incorrect.  I won’t go so far as to say that they based their findings on one flawed study, but I will say that assumptions on neonatal stomach volume are flawed.  I agree with Bergman (cited by both Seagrave, and me).  The neonatal stomach volume, at which the stomach is “full” but not bloated is probably about 20 mL and rapidly expanding as amniotic fluid is replaced, first with colostrum, and eventually with breast milk.  In my practice I usually use a rough estimate of 15 mL/kg during the first month for what I can expect from a baby who is totally full.  I also understand that the average newborn between 7-21 days takes about 30 mL in a “good feed”.  Unfortunately, that last observation comes from my own practice where I have monitored about 250 adequately growing neonates.  That isn’t to say it is made up out of whole cloth, Kent and the good folks at the Hartmann lab have said the same thing in numerous studies (bibliography).  So where is the disconnect?  Neither stomach volume nor average intake tells the whole story.

I’d like to start with stomach volume.  I have no reason to disagree with Bergman or Seagrave, the average neonatal stomach volume is approximately 20 mL., but if you read the works they cite it is actually between 10-35 mL and that is an important distinction.  The stomach is an organ with a tremendous capacity to stretch, the difference between empty and full is tremendous.  In adults, the average stomach volume varies tremendously and is ultimately based on the volume of food habitually eaten (Lutz et al., 2015).  Actual measurements show that the empty adult stomach holds about 50 mL but can stretch to approximately 4 liters (Hoffman & Sullivan, 2017).  That is a stretch capacity of 8,000% (80-fold).  In his work on neonates Bergmann shows that the stretch capacity is about 350% (from 10-35 mL).  Can you imagine attempting to assess how much food you should eat based entirely on your stomach volume?  It would be impossible!  Would we limit your intake to 50 mL per feeding, or would we force you to eat 4,000 mL of food at every feeding?  Both are laughable in their simplicity. Also, it would be foolish to even suggest that you eat the same amount at every single feeding. Imagine, the same amount for all three meals and all three snacks.  Nonsense, as adults we understand that sometimes we want a snack and sometimes we want a feast.  It has nothing to do with how much is available, and everything to do with appetite.  Why then would we suggest that a neonate must eat the same thing at every feeding?  Why would we attempt to predict every single feed?  Newborns are not robots. No, they are like us they eat according to appetite, not some mathematic calculation discovered by research studies.  My answer to both the ABM and the FIB folks is that neonatal stomach volume is a useless predictor for required volume or calorie intake. 

 

So let’s talk about actual caloric requirements.  Unfortunately, I don’t have a good estimate of calorie requirements for a neonate in the first 48 hours.  I agree with FIB, what we think we know is based on myth and bad science (both ours and theirs).  But if we expand that to the first month, there is some pretty interesting stuff out there.   Seagrave reported the estimated neonatal caloric requirement of about 100 kcal/kg/day.  That is lower that the Food and Agriculture Organization (FAO- a division of WHO), which reports 113 kcal/kg/day for male neonates and 107 kcal/kg/day for female neonates, for simplicity we can average that to 110 kcal/kg/day for both male and female (FAO, 2004).  They also report that the TEE (Total Energy Expenditure) for Breast fed infants is lower than what is required for formula fed infants.  In other words, formula fed infants require more calories to survive and grow than breastfed infants.  The actual report is 12% more at 3 months, then gradually getting closer over the first year and becoming equal by 12 – 18 months (FAO, 2004).  That means that the average formula fed infant needs approximately 500 kcal/day where the average breastfed neonate needs only 430 kcal/day (FAO, 2004).  The two sets of numbers a little different, but they end up being close enough for our purposes.  If we can assume that both breastmilk and formula is 20 kcal/ounce (which is close enough), that means that the average (3.5 kg) breastfed neonate needs 385 kcal/day (3,500 g x 110 kcal = 385) or 19.25 ounces per day.  And the average formula fed needs up to 12% more (431 kcal/day or 21.5 ounces). 

That is, of course, assuming the calories taken in and the calories used are the same thing, which microbiome theory would suggest, is not actually correct.  When we look at neonatal feeding, we know that the average newborn takes only 37 mL in the first 24 hours (25 kcal), 100 mL in the second 24-hours (60-70 kcal), gradually increasing to 450 mL/day by 14 days (300 kcal) and 750-1250 mL/day from 30-180 days of life (500-833 kcal).  For references I highly recommend that you look up the collected works of the Hartmann lab from 1976-2016, but if you are lazy, they can all be found in the latest LEAARC Core Curriculum (2019).  That means that newborns are seriously lacking in calories for the first 1-2 days and even for as much as the first month of life, and yet… they thrive.  How do they do that?  It seems a mystery, but it really isn’t.  The simple answer is “because”, for a more complete answer, we will have to turn to theory.   

[I want to spend a second explaining the two different concepts, TEE vs. Total caloric requirement.  There is a world of difference between the 100-113 kcal/kg/day that is required for growth and the TEE.  The TEE is what the body expends to promote survival, not growth.  It is remarkably lower than you normally hear when talking about calorie needs.  The TEE of the average neonate is only 108-110 kcal per day (not per kilogram/day).  The TEE is calculated by a pretty high-tech method (Doubly Labeled Water or DLW, which I don’t have space to go into here, but just know that they use mass spectrometry to measure actual energy use over a period of time, rather than attempting to measure calorie intake).  Just understand that there is a difference, and that difference will be important later.]

I hope you have been keeping up so far because from here on out, we are forced to rely more on theory than actual research, because there is no reliable research out there.  First, we will talk about the normalcy of mammalian physiology.  That means that all things considered equal, the mammalian neonate is designed to survive, and that normal physiology can support that survival.  That means that even if we don’t understand it at a scientific level (and FIB certainly doesn’t not understand it), what happens naturally, is probably what is supposed to happen.  When we see that the average newborn takes in 37 mL of 18.7 kcal/ounce colostrum in the first 24 hours, we have to assume that there is a reason for that.  After all, mammalian physiology rules the known world, it must be doing something right.  My theory (and it is just that, a theory of MINE, take it or leave it).  My theory is that babies are not eating in the first 24-72 hours, they are transferring the mother’s immune system in the form of colostrum.  We all should know by now that colostrum contains almost no lactose (which is to say calories), that it is made up almost entirely of proteins, immune proteins like sIgA, and restorative proteins like human Breast Milk Stem cells (Bode, 2014).  All the calories that a healthy, term, newborn needs are delivered by their body fat through gluconeogenesis, not through breastmilk (ABM, 2016, AAP, 2012).  Like hibernating animals, they get nice and fat, then they fast for a while and live off that fat.  It is normal to lose weight in the immediate newborn period.  That isn’t a failure of the American health care system, it is normal mammalian physiology. 

Second, we need to look at basic nutrition theory.  We have all met that person who can eat whatever they want and not gain weight, and we all know those poor unfortunate souls who look at a piece of cheesecake and end up looking like the Sea Witch from Disney’s “Little Mermaid”.  I’m no Dietician, but I understand nutrition well enough to know that our daily caloric requirements and our TEE do not tell the whole story.  That manipulating daily caloric needs is a game of estimation and trial and error.  We increase or decrease our estimates by 10% until we reach the desired outcome.  For most western adults that is weight loss, for most infants that is weight gain.  That is a long-winded way of saying that we know that infants are eating “enough” when they gain weight.  The actual volume of intake is irrelevant if it doesn’t achieve the ultimate goal which is growth over time.    

Let’s go back and look at that last bit a little more deeply.  Why do some people get fat when others don’t, even when they eat the same amount of food?  Microbiome scientists have discovered that the bacterial content of our gut is ultimately responsible for the efficiency of our caloric absorption.  To put it simply, fat people have bacteria that is very good at getting calories out of food and skinny people have bacteria that is not very good at extracting calories from food. (for a very good explanation of this, I recommend Robert Knight’s TED talk on the subject, found at: https://youtu.be/i-icXZ2tMRM ) To dig a little deeper, a team of researches in Israel discovered that they could use stool samples to predict the speed and efficiency of carbohydrate uptake.  In pregnant women there is an overgrowth of a wonderful little bacteria called methanobrevibacter smithii.  This bacteria is actually why pregnant women are more gassy than non-pregnant women.  You see, it is more efficient at fermenting and digesting carbohydrates in the maternal-child gut.  So where you may get 80 kcal from your average slice of bread, the mother and baby may get 90 kcal.  Simply put, they don’t need to eat as many calories because they get more calories out of the food they eat.  This certainly helps explain why so many pregnant women gain excessive amounts of weight even when they stick to a prescribed diet.  In infants there is a phosphotransferase transporter system (a group of bacteria) that enhances carbohydrate breakdown and transport (Backhead, 2014).  It helps to explain why breastfed infants thrive with fewer calories than they should need, and why formula fed infants need more calories than breast fed infants.  Imagine what changes we may see in the future?  While we agree that pregnant women NEED an extra 300-500 kcal/day to support the increased metabolic needs of the developing pregnancy, perhaps they don’t need to EAT an extra 300-500 kcal, because they might actually get it through their enhanced digestion from good old m smithii.  It is too early to say, but there is evidence that breastfed neonates benefit from the same bacteria, and perhaps formula fed neonates do not (Backhead, 2014).  You might recall that the FAO reported that formal fed infants need extra calories (FAO, 2004).

I know, this is hopelessly long, but how can I explain sucha complicated problem in only 2,500 words?  Let me try to sum it up for you here.  1) Neonatal stomach volume estimates are probably wrong, and almost certainly useless measures that have nothing to do with caloric requirements, so both sides of the argument are wrong.  2) Newborns are not supposed to take large volumes of milk early on, they pack a lunch and take it with them.  3) Colostrum is not calories, so it is a little pointless to try to use it as such.  4)  Infants are not robots; their intake is guided by appetite and ability and those change from feeding to feeding.  The assumption that every feeding must be a specified volume is simplistic and will lead to errors.  5) The breastfed infant has a very efficient carbohydrate digestion system which may enable them to take more than 20 kcal from every ounce of 20 kcal breastmilk, so estimates of daily caloric requirements may not be accurate.  6) (AND THIS IS THE BIG ONE) Infants need “enough” calories to support growth over time and estimates of required volume are just that… estimates.  The proof is in the pudding, as they say, a baby who isn’t growing well on X amount of breast milk needs more breast milk, and vice versa.   I hope that answers your question.  For me, it only creates more questions.  But that is the joy of science, is it not?

References: 

Backhed, Roswall…Dahlgren, & Wang (2015) Dynamics and stabilization of the human gut microbiome during the first year of life. Cell Host & Microbe 17, 690-703.

Bergman, NJ (2013) Neonatal stomach volume and physiology suggest feeding at 1-h intervals.  Acta Paediatrica, 102, p 773-777.

Bergmann, RL., Bergmann, KE., vonWeizsacker, K., Berns, M., Henrich, W., Dudenhausen, JW. (2014). Breastfeeding is natural but not always easy: intervention for common medical problems of breastfeeding mothers – a review of the scientific evidence. Journal of Perinatal Medicine; 42:1 9-18.

Bode L. (2012) Human milk oligosaccharides: Every baby needs a sugar mama.  Glycobiology, 22(9), 114-1162.

Food and Agricultural Organization of the WHO. (2004). Human Energy Requirements. Chapter 3: Energy requirements of infants from birth to 12 months. Retrieved from http://www.fao.org/docrep/007/y5686e/y5686e05.htm#bm05.3 Retrieved on 01 April 2017.

Hartmann, P. (2007) The lactating breast: An overview from down under. Breastfeeding Medicine, 2(1) 3-9.

Hoffman & Sullivan (2017).  Davis Advantage for Medical-Surgical Nursing: Making connections to practice.  FA Davis Publishing.  ISBN-13: 978-0-8036-4417-5

Kent, J.C., Hepworth, A.R., Langton, D.B., Hartmann, P.E. (2015). Impact of measuring milk production by test weighing on breastfeeding confidence in mothers of term infants. Breastfeeding Medicine, 10(6), 318-325.

Kent, J.C., Prime, D.K., Garbin, C.P. (2012). Principles for maintaining or increasing breast milk production. JOGNN, 41: 114-121.

Knight R (2016).  How our microbes make us who we are. TED talks. Retrieved from: https://youtu.be/i-icXZ2tMRM

Lutz, Mazur, & Litch (2015) Nutrition and Diet Therapy, 6^th ed. FA Davis Publishing. ISBN-13: 978-0-8036-3718-4  

Seagrave, J (2018). Newborn Stomach size myth: its not 5-7 mL. retrieved from:  https://fedisbest.org/2017/06/newborn-stomach-size-myth-not-5-7-ml/

Inadequate growth in the newborn

It's been a while since I've written on this blog.  No excuse, I just write when I can.

Today I got a message from a mom who was told by her pediatrician that she was making “skim milk” and that she needed to add more fat to her diet.

“Today the pediatrician told us our two-week-old baby is underweight. He was born at 8lbs 2oz and Now weighs 7lbs 4oz.

I feel like he’s eating well. He eats every 3 hours, sometimes he’ll go 4 at night. It used to be for around 45 minutes but the last 3 days or so he’s done between 20-30 minutes. He definitely empties my breasts when he feeds. I can feel the difference. I’m also pumping once or twice a day and get between 20-35mls per session if 10-15 minutes. He doesn’t seem hungry. He sleeps well after feedings but he’s not gaining his weight back.

He was jaundice and in NICU for 5 days getting supplemental feeds with donor breast milk in addition to my 20-minute feedings every 3 hours. He lost some weight in NICU but lost more the week he’s been home.”

Here was my response:

I want to let you know that your experience is VERY common.  It is nearly impossible for a mom to judge how well their baby is eating.  In fact, it seems that it is impossible for pediatricians too.  As a lactation consultant, I find it very difficult as well.  The only way to know how much your baby is eating while breastfeeding, is to weight him before and after each feeding.  IF you do that for 24 hours in a row, you can know how much he eats.  Of course, I don't recommend doing that, it would drive you crazy.  As such, you must use other ways, to get hints as to what is going on. The only way we know that a baby is transferring enough milk is to follow his weight over time. I strongly recommend close follow up for the first 2-4 weeks after birth.  If I were there, I would see you every 48-72 hours for a couple of days to check on intake and growth.  Since I am not there, and you don't have access to an IBCLC, we will have to work on other ways to check this.  You mention a few helpful signs that suggest Baby is eating well, the emptying of the breast, the frequency and duration of his feeds.  But you also suggest that he has a feeding problem that needs attention. 

First, he has not regained birth weight at two weeks old, which is a red flag.  It isn't dangerous right now, but it is a marker for problems in the future.  You also say that he was eating for 45 minutes at a time.  Both of these suggest that he is/was having trouble emptying the breast.  The average baby can empty the breast in 12-20 minutes. Since you say that he has started feeding for shorter duration, he may have figured it out and turned the corner, but we will have to watch for that. 

Another issue that I see is that he eats every 3-4 hours (that is 6-8 feeds per day), which is not common in newborn.  We expect him to eat every 2 hours for most of the day with an occasional 3-hour stint when he is really sleepy (that is 8-12 feeds per day).  I know how exhausting it is to be a new mom, but it really isn't helpful when a newborn sleeps “well”.  There is a rare group of moms and babies who manage to sleep for long periods of time and still grow, but they are few and far between.  Again, I recommend that you offer him the breast every two hours for most of the day, and every 3 hours if he is really sleepy.  You will notice that I don't say "Day and Night".  Babies don't understand the clock or your sleep cycle.  Most of them are most alert from 9 pm to 3 am, so that is closer to "day" for them.  They sleep most from 9 am to 3 pm, so that is where you will get the best sleep.  Don't fight it, you can't.  Just roll with the punches. 

Now let’s talk about other ways that you can judge how well he is eating.  While he is eating, try to listen for his swallowing at the breast.  A baby who is two weeks old, is usually swallowing loud enough for mom to hear.  You might have to get close to his neck to hear it, but it should be audible.  The harder it is to hear, the less likely it is that he is swallowing.  Another subjective way to know that he is eating, is by tracking his stools.  Most babies will poop 3-4 times a day.  They should be good sized poops, not "sharts", I generally ask if the poop is more than a teaspoon worth.  You see, all humans have a “gastrocolic reflex”, which means that when we eat, our bowels move and dump stool into our rectum.  Adults ignore it, until it is a good time to go, but not babies, they just let it go.  As a general rule, a baby who is eating well, will poop well.  It isn't an exact science, but it is a good rule of thumb. 

 So, what do I recommend:

 

First, get in to see a lactation consultant.  If you go to google and type "find a lactation consultant" you will find the nearest IBCLC.  You can also find help through La Leche League International (www.llli.org)  They have helpful volunteers in almost every corner of the western world and beyond.  An IBCLC is a breastfeeding specialist with certification in assessing and counseling the breastfeeding family.  They can assess his mouth for structure and ability, they can measure food intake with special scales, they can tell more in one visit than the average pediatrician can tell in a month. I do not recommend pediatricians or nurses as a source for breastfeeding information unless they have specific training in lactation (and the vast majority do not).  Contrary to popular belief neither medical school, nor nursing school teaches breastfeeding.  The only people I trust are IBCLC and La Leche Leaders.  It’s sad, but true. 

Second, offer the breast more often.  Every two hours is NORMAL feeding behavior for a newborn.  It will stretch out over time, as his belly and your breasts finish developing, but the average mom and baby transfer very little milk in the first 2-4 weeks and as such they have to feed VERY FREQUENTLY. 

Third, listen for swallowing and track his stool.  They aren't perfect, but they are the most reliable sign that a new mother has, to reassure her that the baby is eating well at the breast.  Believe it or not, babies often go to the breast and suckle for long periods of time and do not transfer breast milk.  Sometimes it is because they aren't hungry, and they suckle because instinct tells them to.  Other times, it is because they can't transfer breast milk due to an oral problem.  I worked with a baby two days ago that sucked for 21 minutes and didn't take any breast milk, then an hour later, he suckled for 11 minutes and took 50 mL.  The difference between the two feedings were his audible swallowing. I use a scale to tell me how much the baby eats, but mom could tell by his behavior at the breast that he wasn't trying to eat the first time. 

Fourth, I would recommend supplementing him with your expressed breast milk (EBM).  You baby was born at 3,628 grams and now he is 3,288 grams.  That is a loss of 340 grams (9.3%).  That is a significant loss, particularly in a two-week-old infant.  He needs more than he is capable of eating right now.  I can't tell you why he is struggling to eat over the internet, I would need to assess him and his feeding behavior.  But it is pretty clear by the weights you gave me, that he isn't getting enough calories to sustain growth.  If he doesn't start getting more, he will not be significantly higher next week when you see the pediatrician.  You mention getting 20-35 mL at each pumping session, that is FANTASTIC for a new mother.  I would suggest that you pump 3-6 times a day and give that to him right after you pump it.  For a baby who is inefficient at breast, it doesn't really matter to me if you give it to him in a bottle, or a cup,. or a syringe.  The problem isn't how you offer the food, it is that he can't use your breasts very well just yet.  But that is a secondary problem right now.  Rule number one is "feed the baby" everything else can come later.    

Fifth... get in to see an IBCLC ASAP.  I know that I've already said it, but I can't stress the importance of seeing a competent health care provider. Ann mentioned to me that the pediatrician said you were making "skim milk" because you didn't have enough fat in your diet.  If that is the case, your pediatrician does not understand the synthesis of breast milk.  You can't make skim milk, you just can't.  Ignore that response.  Your diet will not allow you to make skim milk.  Look at the dairy industry.  Skim milk doesn't come from skinny cows.  They have to remove the fat from the cow.  If they could alter milk components by diet, they would. I don't want to say that your pediatrician is a fool, he is simply a victim of an educational system that did not teach him what he needs to know. 

let me know if that helps.  Feel free to write to me any time you like.  I love to help new moms with breastfeeding issues.