Lactose is the sugar (carbohydrate) found in milk and milk products. It's present in the milk of all mammals, but is not found anywhere else in nature. Human breast milk contains around seven per cent lactose. Infant formula contains a similar amount of lactose.
Lactose is a disaccharide, (which means it's a combination of 2 sugars). In its original form as a disaccharide, it's 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.
Lactose is important in our diet. It aids the absorption of calcium and phosphorus and is thought to support the growth of friendly bacteria, needed to fight undesirable organisms and promote health in the human intestine.
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 for a baby milk containing lactose may be his/her only source of galactose during this important stage of brain development. The effect of long term use of a lactose-free formula (which does not provide galactose) on babies' brain development, is yet to be fully studied.
Glucose, the other simple sugar that bonds with galactose to make lactose in milk, provides a major source or energy (calories) in an infant's diet. Glucose is essential for growth, energy and for cell development. Without glucose in the diet a child will start to use body fat as a source of energy and will lose weight. If deprived of dietary glucose for a long period, the child will not survive. Glucose is found in most foods including lactose-free milk.
Lactose overload (also called 'functional lactase insufficiency') is a temporary problem related to immaturity of an infant's digestive system. An overload of lactose occurs when a baby's digestive system is unable to produce sufficient quantaties of the digestive enzyme lactase to break down all of the lactose received.
Around two thirds of healthy, thriving breastfed babies experience some degree of lactose overload in the early months of life due to foremilk-hindmilk imbalance. This generally occurs when a nursing mother has an oversupply of breast milk and switches sides too soon. As a result the baby receives large volumes of low fat foremilk that is disproportionate to the amount of hindmilk received.
Formula feed babies can also experience gastric symptoms due to lactose overload as a result of receiving excessive volumes of milk in the situation of overfeeding. The reasons for a baby to overfeed can be varied - see our article on hungry baby for examples.
- Frequent watery bowel motions (can often be green in color but not always)
- Bowel motions often have a slightly to very offensive odor
- Bowel motions could be frothy or 'explosive' (shoot out with force)
- Excessive gas
- 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 this problem can continue to the age of 5 months
Symptoms are often mistakenly diagnosed as colic, lactose intolerance or milk allergy or intolerance. Because lactose overload is associated with an oversupply of milk and/or overfeeding, spitting up is increased and a diagnosis of gastroesophageal reflux is common.
When all is running smoothly, lactose is broken down into simple sugars - glucose and galactose in the small intestines by the digestive enzyme 'lactase'. Glucose and galactose can then be absorbed from the small intestines into the blood supply, where it can be used by the body.
When a nursing mother has an oversupply of breast milk (which is common in the early weeks of breastfeeding) switching sides too soon, or frequent feeding patterns that involve alternating breasts at each feeding, can result in a baby receiving large volumes of foremilk. Low-fat foremilk will pass through the digestive system faster than hindmilk (which contain a higher fat content). Breastmilk with a disproptionate amount of foremilk compared to hindmilk may pass through a baby's small intestines too quickly to provide sufficient time for all the lactose to be broken down.
Overfeeding is a common problem for bottle fed babies because many young babies cannot control the flow of milk though an artificial nipple and/or cannot indicate when they have had enough. A baby's digestive system can become overloaded when it receives excessive amounts of milk from large volume feeds or frequent feeding patterns. The larger the volume of milk, the quicker it passes through the digestive tract. Large volumes of milk may pass through a baby's small intestine too quickly for all of the lactose to be digested.
Feeding stimulates the gastro-colic reflex. This reflex causes contractions of the intestines which move the contents along. (This reflex action is why babies often poop or pass gas during feeding). If a baby is fed again before all of the previous feed is fully digested, the gastro-colic reflex will push some of the milk from the small intestine through to the large intestine (bowel).
In the large bowel, the undigested lactose draws in extra water through a process called 'osmosis'. The lactose is then fermented by bacteria, normally present in the bowel, and this produces gas. The end result is excessive gas, cramps, bloating and frequent watery, acid stools (poop) which may scald a little bottom.
As the gas and fluid build up in your baby's bowel this causes her discomfort. She then begins to act like she's hungry because she knows that feeding will provide comfort for her, which it does - but only temporarily. Unfortunately this may provide another large feed, or another feed with a disproportionate amount of foremilk to hindmilk, which results in more gas, more watery stools and more discomfort and the cycle continues.
Lactose overload is frequently misdiagnosed as lactose intolerance. Both conditions display identical gastric symptoms. However, unlike lactose intolerance, where the child fails to gain weight (or loses weight) and is very unwell, an infant with lactose overload is healthy and thriving.
Lactose intolerance arises when a person does not produce enough of the digestive enzyme 'lactase' to break-down lactose into glucose and galactose, which can then be absorbed into the blood supply. For an infant, this means they are then deprived of their major source of energy (calories) provided by glucose. Along with the gastric symptoms, the lactose intolerant child will fail to gain weight or lose weight and become very unwell.
In lactose overload, the infant produces sufficient quantities of lactase to break down enough lactose to provide glucose and galactose essential for healthy growth, but does not produce enough lactase in time to digest all the lactose contained in feedings that contain a disproportionate amount of foremilk to hindmilk. Or in the situation of an overfed formula fed baby, does not produce enough lactase to adequate digest all of the lactase contained in large volumes of milk. As the excess undigested lactose passes into the large bowel cause gastro-intenstinal symptoms. However, unlike the child with lactose intolerance, these infants are healthy and thriving
A baby experiencing gastro-intestinal symptoms due to lactose overload will show positive results to present day tests for lactose intolerance. As a result they are commonly misdiagnosed as lactose intolerant. Sadly, many nursing mothers are mistakenly advised to wean her baby from the breast onto a lactose-free formula. Lactose-free formula will relieve the symptoms but is totally unnecessary (in most situations) as minor changes to feeding management will also relieve the symptoms - without having to wean to formula.
Lactose-free formula will relieve gastro-intestinal symptoms related to lactose overload in a formula fed baby. However, lactose-free formula is rarely necessary when the problem leading to overfeeding have been addressed.
Unfortunately, many healthy, thriving baby's are incorrectly labeled as 'lactose intolerant'. This may result in a lifetime of unnecessary dietary restrictions, deprived of their only or most valuable source of galactose.
For 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. This can include before alternating sides where you are already one-sided breastfeeding.
- See our article on hungry baby to read about common reasons for babies to appear hungry.
- 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 cues to know when it is time to switch, not the clock.)
- Where breastmilk supply is abundant offer only one breast at each feeding.
- Continue to offer the same breast, each time your baby wants to go to the breast, until one breast is soft before offering the other breast. In extreme cases of oversupply, this may involve multiple feedings from the same breast. This will mean your baby gets lower volumes of milk but the proportion of fat in the milk will be increased. Both the lower volume and higher fat content will help to slow down the rate at which it flows through her digestive tract. This will allow more time for the lactose in the milk to be digested. The higher fat content will also help your baby to feel more satisfied.
You will know when you have this problem under control when your baby stools decrease in frequency, thicken in consistency and gasiness lessens. Green stools will gradually become yellow/mustard color.
IMPORTANT: Caution should be used with same side feeding as it can decrease supply. When making changes to feeding managment it is important to closely monitor the number of wet diapers you baby has each day. There should be 6 or more each day. Weekly weight check may also be helpful to reassure you that your baby is getting enough.
Facts about lactose and breast feeding
- 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.
- Foremilk does not contain more lactose than hind milk, but hind milk contains more fat.
- Because a mother may be lactose intolerant, this does not mean her infant is also lactose intolerant. The inherited form of lactose intolerance rarely develops before the age of 4 years.
For 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 establish a flexible feeding and sleeping routine.
- Try to encourage your baby to go 3 or 4 hourly between feedings during the day. Time this from the beginning of one feeding to the beginning of the next.
- Low-lactose or lactose-free infant formula may help to settle gastro-intestinal symptoms. These formulas are often only necessary as a short-term measure. If the problem of overfeeding is corrected, your baby should then be able to return to regular formula.
Added No 2003. Reviewed 2008; Sept 2013.
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