Does Reduced Milk Intake Cause Brain Damage?

When I explain to parents of feeding-averse babies that a significant reduction in their baby’s milk intake is expected in the early stages of resolving his or her feeding aversion, I am often asked “Will this affect my baby’s brain development?”

Some parents claim to have been told by their baby’s doctor or another health professional, that their baby’s brain will not grow and develop normally if he doesn’t drink a minimum daily volume of milk (as specified by the doctor or health professional). Others report that their baby experienced a hypoglycemic episode shortly after birth. As a result, they have doubts about their baby’s ability to maintain his blood glucose (blood sugar) levels within a normal range if his milk intake was to drop. 

I find that misinformation about reduced milk intake affecting a baby’s brain development creates needless anxiety, which in turn prevents some parents from following my feeding recommendations (described in my book, Your Baby’s Bottle-feeding Aversion). Owing to fear of harming their baby, some parents believe they have no choice other than continue to pressure or force their feeding-averse baby to eat; or feed their baby during sleep, or tube-feed their baby to ensure he receives the daily volume recommended by their healthcare professional. By doing so, they directly or indirectly reinforce their baby’s feeding aversion. And the family remains trapped in a stressful situation that is clearly not working for the baby or parents. 

As a parent, you’re not expected to be knowledgeable about human physiology, and so I understand why you might have concerns about the potential effect that a temporary reduction in milk volumes could have on your baby’s brain development. However, I find it disappointing when I learn that a health professional has frightened parents by making claims that reduced milk intake can impair a baby’s brain development, because they should know better. I will explain why such claims are false, and fears of harm unfounded.  

Glucose and brain development

Your baby’s brain requires glucose (which is a type of sugar) to fuel cell functioning. Because neurons (brain cells) cannot store glucose, they depend on the bloodstream to deliver a constant supply of glucose. 

The amount of glucose in your baby’s blood needs to remain within specific parameters considered to be a ‘normal range’. Hypoglycemia (a deficiency of glucose in the bloodstream) can be harmful to brain functioning. Profound, prolonged hypoglycemia can cause brain death. 

Hypoglycemia in the days following birth can occur for various reasons as a newborn undergoes HUGE physiological changes while adapting to life outside the womb. However, a history of a hypoglycemic episode after birth does not mean a baby is incapable of maintaining his blood glucose levels once he has adjusted to extrauterine life. Your baby’s body, like your own, is designed to maintain optimal blood glucose levels. 

Your baby’s brain monitors and directly or indirectly controls all of his bodily functions, including the maintenance of blood glucose within a normal range, though multiple complex processes called homeostatic mechanisms, also known as defense mechanisms. I won’t bore you with medical terms or an explanation of the intricate processes involved in maintaining blood glucose levels. Instead, I wish to provide a simple explanation of how your baby’s body (and your own) maintains his blood glucose levels within normal parameters, to allay your fears concerning a temporary reduction in milk intake causing him harm. (See endnote references for more comprehensive explanations of glucose homeostasis)

There are three ways babies, children and adults receive sufficient glucose to prevent hypoglycemia. 

  1. Food
  2. Glycogen stores
  3. Body fat 


The first line of defense against hypoglycemia is food. The consumption of food – which may be solely breastmilk or infant formula in the case of a baby – provides nutrients and energy (calories/kilojoules). Acids and digestive enzymes in your baby’s stomach and intestinal tract break down the nutrients into tiny pieces, some of which become glucose. Glucose is absorbed through the wall of his small intestine and into his bloodstream, where it becomes ‘blood glucose’. 

Glucose mostly comes from carbohydrates and simple sugars, like lactose or other carbohydrates found in breastmilk, infant formula, and solids. Protein and fats can also be converted into glucose. 

Glucose is carried via the blood to the cells of the body and brain, where it is used as energy to maintain cell function or stored for later use. As your baby’s blood glucose level drops, this triggers the release of a hormone that causes the sensation of hunger, which in turn motivates a non-feeding-averse baby to eat. And the process continues. 

There are many reasons why a baby’s milk intake might not provide for his daily glucose needs. For example: 

  1. Baby has a poor appetite or is too weak to feed effectively as a result of an acute illness, for example, cold or flu or gastrointestinal infection. 
  2. Baby loses fluids and nutrients due to vomiting or diarrhea. 
  3. A breastfed baby’s milk intake is restricted owing to low maternal breastmilk supply or latch problems.
  4. Baby may need to fast before a surgical procedure.
  5. Baby might have self-imposed periods of fasting or limit his milk intake because he has become averse to feeding.

A temporary drop in a baby’s milk intake for any of the above reasons could result in a deficit of glucose from baby’s diet but does not cause a healthy baby to become hypoglycemic. 

If a baby’s diet does not provide sufficient glucose, other homeostatic mechanisms take action to provide a constant supply of blood glucose to support cell functioning and brain development. 

Glycogen stores

After your baby’s body has used the energy it needs, leftover glucose is stored in little bundles called glycogen in his liver and muscles. His body can store enough glycogen to fuel his body in the absence of food for many hours and up to a day.

The second line of defense.  If your baby is not eating enough to provide for his glucose needs, his liver then breaks down stored glycogen and turns it back into glucose to maintain his blood glucose level within a normal range.

Body fat

Adipose tissue (body fat) is our body’s insurance policy against hypoglycemia. Adipose tissue is used for insulation, cushioning, and energy storage.Our bodies store energy (calories/kilojoules) in fat cells as a reserve that can be drawn upon during times of famine and illness.Fat cells expand and shrink as they take on and release energy. 

The third line of defense. As glycogen stores become depleted, fat cells gradually take over the process of maintaining blood glucose levels.Fat cells release fatty acids and glycerol into the bloodstream. This is converted into glucose and glycogen by his liver and release into his bloodstream to maintain blood glucose levels and replenish glycogen stores in his liver and muscles.

If your baby is not eating enough to provide for his daily needs, he will lose a little weight due to the shrinkage of fat cells. The longer the deficit, the more energy that is released from fat cells, and the greater his weight loss. Once your baby’s oral intake improves, fat cells start to store energy once again, they increase in size, and he regains lost weight. 

In summary

A baby’s weight will fluctuate depending on his dietary intake. However, his blood glucose levels will remain within normal parameters, supporting his brain functioning, skeletal growth, and brain development.

temporary reduction in a physically well baby’s milk intake as a result of following my feeding recommendations will not cause hypoglycemia and will not harm his brain development. It will also have no detrimental effect on a baby’s long-term growth potential. 

Written by Rowena Bennett

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