Lactose is the main carbohydrate (sugar) found in milk and in varying quantities in dairy products made from milk including yogurt, ice cream, soft cheeses and butter. Lactose is present in the milk of all mammals (this includes humans), but it is not found anywhere else in nature. It is an important source of energy for babies during their first months of life.
Galactose, a simple sugar that comes from the break down of lactose, is vital to a healthy brain and nerve tissues. Galactose can be found is some foods; however, for a baby milk containing lactose may be his/her only source of galactose.
Our body produces an enzyme called 'lactase'. Lactase is necessary to break down lactose, in our small intestines, so that it can be absorbed into the blood stream. In lactose intolerance there is insufficient lactase enzyme produced and as a result lactose is poorly digested. (The amount of the lactase enzyme produced can be low but it's rarely absent).
Symptoms of lactose intolerance in an infant include...
- Watery bowel movements
- Excessive gas
- Failure to gain weight or loss of weight
- Red and inflamed diaper rash (can occur as a result of a change in acid balance of stools which can scald baby's bottom).
Lactose intolerance does not cause vomiting. (However a milk allergy or intolerance can, and may cause similar abdominal symptoms.)
Lactose is a disaccharide, (which means it's made from 2 different sugars which are bonded together). In its original form as a disaccharide, lactose too large to be absorbed into our blood supply. Therefore the digestive enzyme 'lactase' is needed to break the bond between the two sugars and separate them into 'glucose' and 'galactose', which are monosaccarides (single sugars). Glucose and galactose combined make 'lactose'.
Glucose and galactose, being smaller sugars, can then be absorbed from the small intestines into the blood supply and used by the body for growth and energy needs. When there is insufficient quantities of the lactase to break down lactose (into glucose and galactose) as occurs in lactose intolerance, lactose cannot be absorbed an so passes into the large bowel undigested.
The undigested lactose draws additional fluid into the bowel by a process called osmosis. This results in frequent watery stools. Bacteria, present in the bowel, ferment the undigested lactose, which then produces excessive amounts of abdominal gas. Because sufficient lactose has not broken down into glucose and galactose (which can then be absorbed into the blood stream), an infant is deprived of their major source of energy. When deprived of energy (calories) from the diet, our bodies will use body fat as an energy source and this will result in a loss of weight.
Primary lactose intolerance is an extremely rare condition where infants are born with an inability to digest lactose. If your baby was born with this condition, you will know in the first few days of life. Babies with this condition do not gain weight, are dehydrated and extremely unwell.
Secondary lactose intolerance can occur as a temporary condition following an episode of gastroenteritis (also known as a tummy upset, bowel infection, stomach flu or infectious diarrhea). After the inflammation in the small intestine has gone, the cells that produce 'lactase' return and so does tolerance to lactose. This type of lactose intolerance usually lasts only a couple of weeks. A secondary lactose intolerance can also occur as the result of inflammation of the lining of the intestinal wall due to milk protein allergy or intolerance.
An inherited form of lactose intolerance, known as acquired lactose intolerance is common. However, it will rarely affects a child before the age of 4 years (often not developing until late adolescence). This occurs in people who originate from countries were milk is not traditionally given after infancy e.g. Asian people, Native Americans, Indigenous Australians and people from the Middle East, Mexico, the Mediterranean and Africa. Most people of Anglo-Saxon origin (Caucasians) keep producing lactase and rarely develop this form of lactose intolerance. The incidence of lactose intolerance is overly exaggerated. Studies have shown that most people who believe they are lactose intolerant are not.
Often mistaken for lactose intolerance is lactose overload, also known as functional lactase insuficiency. Lactose overload presents with almost identical symptoms as lactose intolerance. However, unlike the child with lactose intolerance, who fails to gain weight and is very unwell, babies experiencing gastric symptoms related to lactose overload are healthy and gain good (even large) amounts of weight. The management of lactose overload is different to that of lactose intolerance.
Although tests can be undertaken, they do not offer definite proof of lactose intolerance in young babies and can often be misleading. Tests are often positive in normal babies under the age of three months and can be positive in up to 2/3 of healthy breastfed babies in the first 5 months, so is not always helpful to rely on these tests.
Lactose tolerance test
Diagnosis of intolerance is made if blood sugar is not raised after consuming a lactose rich drink.
Hydrogen breath test
Diagnosis is based on the presence of hydrogen in the breath due to incomplete digestion of lactose.
Stool acidity test
Diagnosis is based on increased acidity of the stools due to incomplete lactose digestion.
Small bowel biopsy
This procedure can be performed to diagnose malabsorption problems. It is an invasive procedure and is only indicated where the child in failing to thrive for unknown reasons.
For a breastfed baby
A breastfed baby may experience a secondary lactose intolerance following a bout of gastroenteritis. Because breast milk will aid the recovery of your baby's small intestines breast feeding should be continued.
Many breastfed babies experience symptoms similar to lactose intolerance (which provide positive test results). For a healthy, thriving infant symptoms are related to an oversupply of lactose or from large, frequent feeds and not due to lactose intolerance. Symptoms can nearly always be helped without stopping breast feeding. See our article of lactose overload for feeding tips.
For a formula fed baby
If lactose intolerance is suspected following a bout of gastroenteritis, then milk and milk products can be eliminated from the diet for a period of time. If symptoms go away, it's normally possible to return your baby to his normal diet within a few weeks. Reintroduce regular formula by substituting the lactose-fee formula in increasing proportions over 2 or 3 days.
If no improvements in bowel movements or abdominal symptoms are seen following a trial on lactose-free formula, or if other symptoms develop, have your baby seen by a doctor, so that he/she can be assessed other reasons for these symptoms.
Contrary to popular belief, lactose intolerance does NOT mean your child must AVOID every drop of milk or dairy food. People experience different degrees of sensitivity to lactose. Those with lactose intolerance CAN still digest some lactose without developing any symptoms.
Dairy foods are an important source of calcium and protein for babies and young children. The amount of lactose contained in different dairy foods varies. It's possible to select nutritious, calcium enriched foods that are low in lactose.
Full-cream milk products are often tolerated by those with lactose intolerance better than low-fat milks. This is partly because the fat in full-cream milk slows down the digestive process, so that lactose leaves the stomach and small intestine more gradually. Drinking milk with meals will also help to slow down the digestive process, meaning symptoms are less likely to occur.
Yogurt can often be tolerated by many children with lactose intolerance, because the bacteria that thicken the yogurt help to breakdown the lactose. However, some may find yogurt causes symptoms.
Cheese and butter are not a problem for lactose intolerant children. Neither contain more than tiny amounts of lactose, with the exception of ricotta cheese. However, even ricotta has relatively small amounts of lactose and is unlikely to cause problems.
Through a consultation at BabycareAdvice, we can assist you to discover the true cause of your baby's discomfort or irritability, and how you can encourage his contentment.
If your baby is breastfed, we can advise on feeding management to reduce any discomfort he may be experiencing, while supporting you to continue to successfully breastfeed. If your baby is currently formula fed, we can recommend ways to reduce his fussiness and/or manage difficult bottle feeding problems.
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Added Nov 2003. Reviewed Aug 2008; Sept 2013.