As a parent of a bottle-fed baby, you might worry that he’s not drinking enough or that he could be getting too much. This article explains how to estimate the amount of milk your baby needs and reasons why some babies require more milk and some less than others.
Is there cause for worry that baby is not drinking enough milk?
You might be worried that your baby is not getting enough because he appears to have an insatiable appetite or because he’s often crying or wakeful. Or you could be concerned about potential health consequences if he’s taking more or less milk than recommended.
In most cases, parents needlessly worry about the amount of milk their baby consumes. Baby is taking what he needs for healthy growth. Concern stems from parents’ lack of awareness of their baby’s changing nutritional needs, and hence they may have unrealistic expectations about the amount of milk their baby requires at his current stage of development. A health professional’s miscalculation or failure to take into account individual differences - many of which can cause a baby to require more or less milk than standard recommendations - can be the source of a parent’s unrealistic expectations.
But of course, in some cases there is genuine reason for concern. To determine whether this is the case or not, a good starting point is to know how much milk the ‘average’ baby requires at different stages of development. But even more important is an appreciation of the many reasons why an individual baby might require more or less milk compared to the ‘average’ baby.
Standard calculations of milk for babies
Health professionals in general will use the following standard calculations as a guide when estimating a baby's milk requirements. (Use ‘corrected age’ if baby was born preterm)
Note: The above approximations are based on normal strength breastmilk or infant formula, which provides around 20 calories per ounce, or 67 calories per 100ml.
The figures provided are estimations only. They are not “should have” amounts.
There are many reasons why a baby might take more or less than the approximated amount. Thus, the amount of milk required varies considerably between babies.
What influences milk requirements for babies?
Standard calculations offer a simplistic guide to estimate a baby’s milk requirements. They are based solely on a baby’s age and weight. Standard calculations don’t take into account the many variables that influence an individual baby’s milk requirements, such as:
- rate of growth;
- body fat;
- genetic endowment;
- body shape;
- metabolic rate;
- activity levels;
- state of health;
- milk concentration;
- amount of solid foods consumed; and
- feeding patterns.
1. Rate of growth
As a baby matures, his rate of growth gradually slows down. For example, the ‘average’ baby doubles his birth weight around 4 months of age and triples his birth weight by 12 months. From the table above, you will notice that standard calculations reduce the approximated amount at 3-month increments, as a way to keep pace with the natural reduction in growth rate as a baby matures. However, a baby’s milk requirements do not suddenly drop at each 3-month mark, as the table indicates. It’s a gradual process.
As a baby’s rate of growth slows, this means he requires less milk in relation to body weight. Because baby’s body weight increases at such a rapid rate during the early months, the total amount of milk consumed each day tends to increase even though his rate of growth is slowing down. The ‘average’ baby’s total milk intake typically peak at around 4-6 months of age and then gradually reduce over many months. An individual baby may reach their peak daily milk intake at an earlier or later age.
The table below, depicting the average range of daily milk intake for age, demonstrates a peak in milk consumed at 4-6 months of age before decreasing.
Note: If your baby is not taking the amount specified, this does not mean anything is wrong. But it does mean further investigation may be necessary to determine the reason. Read on and you might discover the reason.
2. Body fat
One way a baby’s body fat is estimated is by calculating his weight-to-length ratio. This helps a health professional to determine if baby’s weight is in a healthy range in relation to his length, or whether he’s underweight or overweight.
The amount of body fat a baby carries is more relevant than weight when estimating milk requirements. For example, three babies of the same age could weigh exactly the same amount and yet one baby could be overweight, another could underweight, and the third baby could be within a healthy weight range. The difference relates to each baby’s length. Therefore, despite being the same age and weight, each baby may require different amounts of milk.
Some babies are born underweight for gestational age. Others experience feeding problems that cause poor growth during the early months following birth. Once baby is born or once the feeding problem is corrected, he may then display ‘catch-up’ growth. During the period of ‘catch-up’ growth he may consume more than the approximated amount of milk for his age and weight.
At the other end of the spectrum, some babies are born with large amounts of body fat. Others lay down additional stores of body fat in the early months owing to overfeeding (overfeeding is a common problem in the early months owing to the presence of an active sucking reflex and misinterpreting baby’s behavioral cues and desire to suck for comfort as hunger). Once baby’s sucking reflex has disappeared at around the age of 3-4 month, he has greater ability to self-regulate his milk intake to meet his needs. He may then go through a period of catch-down growth, where his body starts to burn excess stores of body fat for energy, allowing his body weight and shape to realign to his genetically predetermined weight and shape. During a period of catch-down growth, he’s likely to take less than he did when he was overfeeding, and possibly less than the approximated amount of milk using standard calculations. Note: Catch-down growth is commonly mistaken as poor growth.
3. Genetic endowment
A baby who is genetically inclined to be long (usually because parents and family members are tall) may take larger volumes of milk compared to a baby who is genetically programmed to be small (because parents and family members are of small stature). A baby born to large parents will gain larger amounts of weight compared to the baby who is born to small parents. Hence each baby may require more or less milk than ‘average’.
Your baby might have been born ‘average’ size, ‘large-for-dates’ or ‘small-for-dates’ owing to various factors that influence a baby’s growth in the womb. But that doesn’t mean he’s going to stay that way. After birth his body shape and size may change as he displays catch-up or catch-down growth until such time as his body realigns according to his genetic endowment.
4. Body shape
Just like the rest of the human race, babies vary in body shape. A baby’s genetic endowment, which includes ethnicity, influences his body shape as well as his length. There are three main body shape types: ectomorph, mesomorph and endomorph. Ectomorphs have lean body mass. Endomorphs have a large body mass in relation to length. Mesomorph falls somewhere in between.
Your baby’s genetically programmed body shape will influence his appetite and hence the amount of milk he’s willing to take. If you’re worried that your baby is not getting enough milk because he’s lean, consider whether he may be genetically programmed to be lean.
5. Metabolic rate
Metabolic rate refers to how quickly we burn calories. Some babies burn calories at a faster or slower rate compared to others, in the same way that some adults and children do. Hence, a baby with a faster or slower metabolic rate may require more or less calories compared to another baby of the same age and weight.
6. Activity levels
The more active a baby is, the more calories he burns. Some babies are very inquisitive and always on the go. They may require more calories than average to fuel their activities. Alternatively, baby might be genetically programmed to be lean. Other babies are very relaxed, sleep a lot and are happy to sit and watch. They might require fewer calories… or not. It also depends on baby’s size, body shape and metabolic rate.
7. State of health
Acute and chronic illnesses can affect a baby’s appetite and thus desire to eat. Some medical conditions will affect the amount of calories a baby requires to maintain healthy growth; for example lung and cardiac conditions can increase the baby’s energy requirements. Some physical problems and genetic conditions are associated with poor growth and thus have a negative affect on baby’s appetite or may hinder his ability to feed effectively.
8. Milk concentration
Standard calculations for estimating milk requirements are based on regular strength breastmilk or infant formula, which provides approximately 20 calories per ounce or 68 calories per 100ml. However, a baby might be given high-energy milk that provides 22, 24, 27 or more calories per ounce or 75, 82, 90 or 100 calories per 100ml.
High-energy milk feeds are designed for babies who have high-energy requirements, such as preterm babies (usually only until their expected delivery date or a little beyond); babies with lung and cardiac conditions, and babies who are too weak to feed effectively. In some cases, high-energy feeds are given to healthy, thriving babies who may have once required them but continue to receive them even though they could now drink normal strength milk (and benefit from the extra fluid that normal strength milk provides). High-energy feeds are also a medical option recommended to improve the growth of physically well babies whose milk intake is poor owing to an unresolved feeding aversion.
High-energy milk basically means baby receives more calories in less volume compared to normal strength milk. So if your baby receives high-energy milk this needs to be taken into consideration when estimating his milk requirements.
9. Solid foods
Your baby requires a certain number of calories per day to meet his growth and energy needs (which varies from day to day). The more calories he receives from solid foods, the less he will take from milk (breastmilk or infant formula) feeds.
The order and timing of milk feeds in relation to solid foods will affect the amount of calories your baby takes from each source. If he’s not drinking enough milk because he’s eating large amounts of solid foods, you might try offering milk feeds first, followed by solids 20 minutes later. Alternatively, if he loves his milk but then refuses solids, you might try offering solids first.
10. Feeding patterns
The number of feeds your baby has each day and will influence the amount he takes at each feed. In general, baby who feeds 8 times a day will take less at each feeding compared to if he ate 6 times a day. But over the course of the day take a similar amount either way. Of course, the number of feedings needs to match your baby’s biological needs.
When you consider all possible reasons for a healthy baby to take more or less than the approximated figures calculated according to age and weight only, its easy to see why it’s not possible for a health professional, other parents, infant formula manufacturers or Internet websites to tell you how much milk your baby “should have”. They might estimate the amount but ultimately it's only a guess - one that could be close or way off the mark.
Only your baby can determine how much his body needs.
Written by Rowena Bennett
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