Lactose Overload - How To Reduce Lactose In Breastmilk

Lactose Overload - How To Reduce Lactose In Breastmilk

Lactose Overload - How To Reduce Lactose In Breastmilk

Lactose overload is common but poorly recognized problem. Symptoms are typically misdiagnosed as colic, reflux, milk allergy or intolerance. If you have a gassy, irritable newborn, you won’t want to miss this article.

What is lactose? 

Lactose is the sugar (carbohydrate) found in milk and milk products. It is present in the milk of all mammals but is not found anywhere else in nature. Breast milk contains around 7% lactose.

Most cows’ and goats’ milk based infant formulas contain a similar percentage of lactose as breast milk. Soy based infant formulas and most ‘hypoallergenic’ infant formulas have no lactose.

Lactose is a disaccharide, which means it's a combination of 2 sugars joined together. As a disaccharide it is too large to be absorbed by the body, so it needs to be broken down into glucose and galactose, which are monosaccarides (single sugars), by the digestive enzyme 'lactase'. Glucose and galactose can then be absorbed into the blood stream and used by the body.

What is lactose overload? 

Lactose overload is a ‘dose-related’ digestive problem. Symptoms occur when a baby’s digestive tract becomes overloaded with lactose as a result of overfeeding in the case of bottle-fed babies and oversupply syndrome in the case of breastfed babies.  

The medical term for lactose overload is ‘functional lactase insufficiency’. This definition implies that some newborn babies do not produce sufficient quantities of the digestive enzyme, lactase, to breakdown all of the lactose consumed. Most healthy babies can tolerate the amount of lactose within normal volumes of milk, and thus they’re not technically lactose intolerant. However, the symptoms linked to lactose overload occur when a baby cannot adequately digest large amounts of lactose received as a result of excessive consumption of milk. So they display GI symptoms that make them appear like they’re suffering from a digestive disorder.  

Lactose overload is not a disorder. Symptoms occur in response to inappropriate feeding management. Symptoms can be significantly reduced or completely relieved in as little as 24 hours once appropriate feeding management strategies are applied.

Who is at risk of lactose overload? 

Lactose overload is a common but poorly recognized problem affecting countless numbers of breastfed and bottle-fed babies in the early months of life. It's estimated that as many as 2/3 of breastfed babies experience episodic symptoms associated with lactose overload in the first 3 months of life. A small percentage of breastfed babies may be affected up to 6 months of age. The number of bottle-fed babies affected is unknown.

Causes of lactose overload

The primary reasons for lactose overload symptoms are overfeeding in the case of bottle-feed babies, and oversupply syndrome in the case of breastfed babies. 


Overfeeding is a common problem for bottle-fed babies in the early months because newborn babies cannot control the flow of milk though an artificial nipple (which is often stiff); stop when they want to stop (because of their sucking reflex); or indicate when they have had enough (owing to immaturity in physical development). The risk of overfeeding is increased if the flow rate of the nipple is too fast and/or the parent misreads the baby’s behavioral cues and offers feeds too often. (See 'Hungry baby' for other reasons why babies overfeed).

Newborn babies are especially vulnerable to overfeeding because they have limited ability to self-regulate their intake owing to the presence of their sucking reflex. The sucking reflex, which disappears around 3-4 months of age, is triggered by pressure on a baby’s hard palate by the mother’s nipple, the nipple of a feeding bottle, a pacifier, baby’s fist or a parent’s finger.  Once the sucking reflex has been triggered, a baby will suck regardless of whether she's hungry or not. Because a reflex is an involuntary, automatic response, she cannot not suck. The presence of a baby's sucking reflex increases the risk of overfeeding if parents are not careful. 

Simplistic advice to 'feed on demand' increases the risk of overfeeding a newborn baby. Infant behavioral cues are not easy to read. Many babies under the age of 6 months have a strong desire to suck. They want to suck when hungry, tired, bored, overstimulated, when uncomfortable, to soothe when upset, and for pleasure. Their desire to suck means they will often fuss and give the appearance of hunger at times when they're not in fact hungry, but rather want to suck. While I support the opinion that babies need to be fed whenever they're hungry, all too often 'demand' feeding is misinterpreted by parents to mean 'feed baby every time she fusses, cries or wants to suck'. 

Its the combination of active sucking reflex and misinterpreting behavioral cues as hunger that places newborn babies at high risk or overfeeding. And it's overfeeding that causes symptoms of lactose overload.

Oversupply syndrome

The situation is even more complex for breastfed babies because the ratio of fat in breast milk is constantly changing - within a single feed and from feed to feed. The fat content of the milk received will influence the volume of milk a baby consumes. While exclusively breastfed babies don’t generally overfeed (though this can happen in certain situations) they can receive more lactose than their intestinal tract can handle owing to foremilk-hindmilk imbalance. This does not imply that there is anything wrong with a mother's milk. Foremilk-hindmilk imbalance occurs when a nursing mother has an oversupply of breast milk (more than her baby needs) and switches her baby between breasts too soon. Her baby may then receive disproportionate amounts of low-fat foremilk in relation to high-fat hindmilk. As a consequence of switching too soon, the baby needs to consume larger volumes of low-fat milk in order to receive sufficient calories to meet her growth and energy needs, and in doing so she may also receive more lactose than her intestinal tract is capable of digesting.

It's not the frequency of feedings that cause GI symptoms in the case of an exclusively breastfed baby, but rather the fact that the mother is switching sides too soon or too often. If a newborn breastfed baby is also bottle-fed, overfeeding could potentially compound the problem and worsen the symptoms of lactose overload. 

Sleeping problem

I find that more often than not, an underlying sleeping problem begins the chain of events that leads to lactose overload problems. Typically an infant sleeping problem - which is usually due to sleep associations - starts first. This then causes broken sleep. Broken sleep means naps are short which then results in more frequent feedings. Hunger is often blamed for baby's wakefulness. Broken sleep can also cause infant distress due to lack of sleep. Irritability due to over-tiredness is commonly blamed on hunger. Babies' desire to suck as a way to fall asleep is also blamed on hunger. So not only is the baby distressed due to lack of sleep, she now overfeeds and suffers gastro-intestinal (GI) discomfort associated with lactose overload. And if that's not bad enough, over-tiredness makes newborn babies vulnerable to distress associated with overstimulation. 

Signs and symptoms of lactose overload  

  • A breastfed baby’s bowel motions can be liquid, frothy or 'explosive' (shoot out with force) and have a slightly offensive odor.
  • A formula-fed baby’s bowel motions tend to be sloppy and foul smelling.
  • Bloating.
  • Cramps.
  • Excessive gas (farting) - foul smelling.
  • Irritability/screaming.
  • Sleeplessness or wakefulness.
  • Baby appears to be constantly hungry.
  • Baby gains large amounts of weight (which is not the case when a baby is lactose intolerant).
  • Baby is usually less than 3 months old, but in some cases this problem can continue up to the age of 5-6 months.
  • The baby might also spit up or regurgitate milk (not due to lactose overload but rather overfeeding which causes symptoms of lactose overload).
  • Fussing during the feed and bearing down.
  • Extreme grunting in early hours of the morning.

The intensity of GI symptoms can vary in degree (mild, moderate or severe) depending on the amount of lactose present in the large bowel at the time. The baby could suffer from intestinal discomfort at different times of the day and night and at other times appear unaffected. 

What triggers symptoms

Homeostatic mechanisms! Homeostasis occurs when the body acts in a way to maintain a normal balance. I believe that the GI symptoms linked to lactose overload are the result of a number of homeostatic mechanisms acting to prevent babies from accumulating too much body fat at a time they’re at greatest risk of overfeeding. An excessive accumulation of body fat is not healthy for anyone, including babies. If an overconsumption of lactose can’t be digested, it can’t be absorbed, and the excess calories cannot be converted and stored as body fat.

Homeostatic mechanisms in action

When all is running smoothly, lactose will be broken down into simple sugars - glucose and galactose in the small intestines by a digestive enzyme called 'lactase'. Galactose and glucose can then be absorbed into the blood stream through the wall of from the small intestines, where it can then be used by the body. Only small amounts of undigested lactose enter the large intestine (bowel).

Babies have limited ability to produce the enzyme lactase within any particular time period. Normal healthy babies are capable of digesting lactose sufficient for healthy growth, but they may not be able to digest excessive amounts of lactose. 

A baby's digestive system can become overloaded by lactose from large volume feeds, low-fat feeds, and/or frequent feeding patterns. The larger the volume of milk in a baby’s intestinal tract, the quicker it travels through. Large volumes of milk can pass through a baby's small intestines too quickly for all of the lactose to be digested.

The nutritional content of milk also influences the speed at which it travels. Fat slows down the rate at which milk will pass through the stomach and intestinal tract. Because foremilk is lower in fat compared to hindmilk, this means it will travel through the small intestines faster. Plus, a breastfed baby who receives mostly low-fat foremilk will want to feed more often (in order to receive sufficient calories for her growth and energy needs) compared to if she consumed more high-fat hindmilk. So she consumes large volumes of low-fat milk that travels through her small intestines at a rate that is too fast for all of the lactose to be digested.

It’s the amount of milk present in the intestinal tract at the time, rather than the amount consumed in a single feed, that matters. So its possible for a baby to consume more milk and thus lactose than she can handle as a result of small, frequent feeds. Frequent feeding patterns also affect the rate of flow through the intestinal tract. As milk begins to empty from the stomach into the small intestines this stimulates the gastro-colic reflex. This reflex causes contractions of the intestinal wall, which then pushes the contents along. It’s the body’s way of making room for the new feed. (The gastro-colic reflex action is why newborn babies often poop or pass gas during feeding and grunts at times). If a baby is fed again before the lactose in the previous feed is fully digested, the gastro-colic reflex may push some of the undigested lactose from the previous feed from the small intestines through to the large intestine.

All is good so far. It’s the next stage where problems occur for the baby.

Then what happens?

If the milk travels through a baby’s small intestines too quickly for all of the lactose to be digested, large amounts of undigested lactose can be pushed into the large intestine. The the undigested lactose (which is a sugar) draws in extra water through the intestinal wall through a process called 'osmosis'. Intestinal bacteria (both good and bad) normally present in the bowel ferment the undigested lactose. The fermentation process produces intestinal gas. The end result for baby is bloating, intestinal cramps, frequent watery/sloppy, foul smelling bowel motions, and lots of flatus (farts). Stools are acidic and can scald baby’s little bottom if left in contact with the skin too long.

The bloating, intestinal cramps, acid poop causes discomfort/pain for the baby. She acts like she's hungry because she has learned that feeding provides comfort, which it does - but only temporarily. An additional feed provides more milk and more lactose, which results in more lactose and potentially more gas, cramps, watery stools and more abdominal discomfort for baby... and so the cycle continues.


Reflux is not a cause or symptom of lactose overload. But it often goes hand in hand with lactose overload in the case of an overfed baby. Reflux (milk regurgitation) is another homeostatic mechanism that protects a baby from the effects of overfeeding. Regurgitation of stomach contents will occur when the stomach is overly stretched due to large volume feeds. Babies who throw up large volumes of milk may be less inclined to suffer GI symptoms due to lactose overload, because by throwing up they may reduce the lactose load within their intestinal tract. But throwing up won’t necessarily prevent episodes of GI discomfort due to lactose overload.

NOTE: Reflux also occurs for reasons other than overfeeding. Because a baby regurgitates milk does not mean they are overfeeding.


What babies suffering from lactose overload need is for their parents or caregivers to receive education on interpreting infant behavioral cues and effective feeding management advice. What most babies get, is a medical diagnosis, medications and/or dietary change.

The symptoms of lactose overload are often mistakenly attributed to problems such as colic, reflux, lactose intolerance or milk protein allergy or intolerance. A mistaken diagnosis can trigger an unfortunate chain of events that has the potential for unintended and potentially harmful consequences for the baby further down the track. 

At first, baby's symptoms may be dismissed as "normal". If parents are insistent that it's not, baby might then be diagnosed with colic or reflux, or both, and given medications. 

  • Colic medications: Many colic medications -  that actually make a difference - work by reducing contractions of intestinal tract. By doing so, provide more time for more lactose to be digested and reduce symptoms related to lactose overload.
  • Antacid and acid suppressing medications delay gastric emptying time, and therefore may provide more time for lactose to be digested which in turn may reduce discomfort due to lactose overload. Or they can make the situation worse, as these meds can inhibit the growth of good bacteria in the intestinal tract that help to digest lactose (as can antibiotics).

So there could be some relief as a result of medications, but usually not enough, especially when baby has an underlying sleeping problem. Next baby might be diagnosed with a digestive disorder like lactose intolerance or milk protein allergy or intolerance. 

Lactose-reduced and lactose-free formula

So-called ‘colic’ and ‘reflux’ formulas are lactose-reduced. Soy infant formula and hypoallergenic formulas are lactose-free. All of these formulas have the potential to mask the symptoms associated with lactose overload. They do nothing to fix the problem that is causing the symptoms, i.e. overfeeding or oversupply syndrome, but they can reduce or relieve abdominal discomfort associated with lactose overload, and in doing so provide some relief to distressed babies and exhausted parents. (They won't resolve distress due to an underlying sleeping problem).

Basically, medications and lactose-reduced or lactose-free formula relieve symptoms by inhibiting the actions of a baby’s natural homeostatic mechanisms. Sure, a baby may be more content as a result, but by inhibiting his homeostatic mechanisms, he’s now at increased risk of accumulating excessive amounts of body fat if overfeeding issues are not addressed (i.e. if parents continue to misinterpret behavioral cues as hunger while baby’s sucking reflex remains active).  

Consequences of misdiagnosis 

  • Babies are exposed to the risk of side effects and secondary adverse effects associated with medications. (See Colic medications and antacids).
  • Breastfed babies are needlessly weaned to formula and deprived of the benefits of breastfeeding
  • Botte-fed babies might be given bitter tasting hypoallergic formula, which costs 3 times as much as regular formula. Incorrectly labelling a healthy, thriving, yet irritable baby as 'lactose intolerant' may result in a lifetime of unnecessary dietary restrictions.   

Misdiagnosis occurs more often than you might think. Many health professionals have not heard of lactose overload and how this relates to feeding management. Nor are they aware of the intricacies involved in breastfeeding or bottle-feeding healthy babies, and therefore may be ill-equipped to advise parents on how to resolve this problem through feeding management strategies. As a result of receiving feedback from parents that their baby is more settled as a result of medications or due to switching to lactose-free formula (such as soy or hypoallergenic formula) gives the health professional the false impression that their diagnosis was correct and they are then more likely to advise other parents to do the same; unaware that there are far more effective ways to manage this problem and promote a baby’s contentment.

Lactose overload vs lactose intolerance

The GI symptoms associated with lactose overload and lactose intolerance are due to the fermentation of undigested lactose in the large bowel. Hence, the GI symptoms for both problems are the same. A baby troubled by lactose overload will have false positive results when tested for lactose intolerance. These tests check the baby’s stools (poop) for indications of acid, which is present when lactose is fermented in the large bowel (which will occur with both problems).

In the case of lactose overload, it’s the excess lactose, beyond what is normal, that the baby has trouble digesting. Although irritable due to GI discomfort, the baby is physically well and gaining weight well. (Rarely, a breastfed baby might display poor growth as a result of this problem).

In the case of lactose intolerance, the baby is unable to digest normal amounts of lactose. This means the baby, whose main or only source of nutrition is milk, will be deprived of the calories that lactose provides (while she is fed milk containing lactose). She will quickly become unwell and lose weight. (See our article of lactose intolerance for more).

Why is lactose important? 

Lactose is important to a baby’s health. It aids in the absorption of calcium and phosphorus and supports the growth of good bacteria in the intestinal tract. Good bacteria are major players in the prevention of disease. They inhibit the growth of harmful microorganisms – bacteria, viruses, and parasites - that live in the intestinal tract and those entering the body in food and fluids. Good bacteria help to keep the walls of the intestines healthy, preventing harmful microorganisms from entering into the blood stream. Good bacteria also aid in the digestion of lactose.

Galactose, a simple sugar that comes from the breakdown of lactose, is vital to a healthy brain and nerve tissues. Galactose can be found is some foods, but milk containing lactose will be a baby’s only source of galactose during the early months - an important time of rapid brain growth and development. 

Glucose, the other simple sugar that bonds with galactose to form lactose in milk. Glucose is essential for energy, growth and cell development. Without glucose in the diet a baby will use body fat as a source of energy, and lose weight. A baby will not survive if deprived of glucose for a long period. Most foods, including lactose-free milk, will be broken down or converted into glucose in the body.  

While all infant formula provide glucose, lactose-free formula, soy infant formula and most hypoallegenic formulas do not. Babies fed these formulas miss out on the benefits of galactose in the early months. Insufficient studies have been conducted to determine whether this has any detrimental long term effects on a baby's brain development or not. 

What you can do to solve lactose overload

Breast fed babies

The key to correcting the problem of foremilk-hindmilk imbalance, which leads to lactose overload, is to ensure your breasts are adequately emptied before switching sides.

If you are currently offering both breasts at each feeding, try to extend feeding time on each breast to ensure your baby has adequately emptied the first breast before switching sides. (Observe your baby's feeding behavior to decide when it’s time to switch rather than watching the clock. While your baby is contentedly feeding, there is no need to switch sides. She will let you know when she needs to be switched).  If this does not relieve her GI symptoms, try one-sided breastfeeding.

How often you would need to feed from the same breast before switching to the other side would depend on the degree of oversupply (mild, moderate or extreme) and how often you feed your baby. If you have an overly abundant supply of breast milk it may be necessary to offer your baby the same breast multiple times (2, 3 or 4 times) before your breast is adequately drained (not that breasts every fully empty). This will mean your baby gets lower volumes of milk but the proportion of fat in the milk will be increased with each feeding. The higher fat content will help to slow down the rate at which the milk flows through her intestinal tract. This will allow more time for the lactose to be digested in her small intestines and minimise GI symptoms related to lactose overload. The higher fat content will also mean your baby will feel more satisfied and she may then not want to feed as often.

Also see our 'Hungry baby' article for reasons why babies often appear to be hungry when they're not.

IMPORTANT: Caution should be used with same side feeding as it can decrease supply (which is what you want when you have an oversupply but not to the point where it becomes an undersupply). When making changes to feeding management it is important to closely monitor the number of wet diapers your baby has each day. There should be 5 or more wet disposable diapers or 6 or more wet cloth diapers each day. A weekly weight check may also be helpful to reassure you that your baby is getting enough nourishment. Also be guided by your baby’s feeding behavior. If she’s fussing at the breast and it feels soft, offer the other side.

Facts about breast milk and lactose

Lactose is produced in breast milk independent of what the mother eat or drinks. Whether she drinks milk or eats dairy food or not, the amount of lactose in her milk will be the same. 

Formula-fed babies

  • See Estimate how much formula your baby needs to discover if your baby is overfeeding.
  • See 'Hungry baby' to discover common reasons for overfeeding.
  • Try to encourage your baby to go 3 - 4 hours between feedings during the day (timed from the beginning of one feeding to the beginning of the next).
  • If your baby is feeding quickly (under 10 minutes), slow down the feed by using a slower nipple or give your baby brief breaks during the feed.
  • Respond to your baby's feeding cues and stop the feed when she indicates she wants to stop. Don't try to make her empty the bottle. 
  • Discourage a bottle-feeding-sleep association by keeping your baby awake during the feed or or waking her if she becomes sleepy while feeding. 
  • If your baby is currently on low-lactose or lactose-free formula once you have addressed reasons for overfeeding (above) you may find you can return her to regular formula.

How to tell when things are under control

You will know when you have this problem under control when your baby’s stools decrease in frequency, thicken in consistency, and she become less gassy and more settled. Green stools will gradually become yellow/mustard color.

Making appropriate adjustments to infant feeding practices can be very effective in relieving a baby’s GI discomfort associated with lactose overload; however, feeding strategies alone won’t necessarily guarantee her contentment. Baby care problems are not rationed to one per baby. A lactose overload problem often develops as a result of a underlying infant sleeping problem. It can also develop when parents misinterpret their baby’s desire to suck at times of tiredness, when bored, when over-stimulated, when uncomfortable and for pleasure, as hunger. 

Written by Rowena Bennett.

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