Lactose intolerance refers to the gastrointestinal symptoms that occur when you aren't able to properly digest lactose, a type of sugar found in milk and other dairy products. It is caused by a shortage of the enzyme lactase in your body. Although it's not a dangerous condition it can cause discomfort with symptoms such as bloating, stomach pain, diarrhoea and gas.




Lactose is the carbohydrate (or sugar) naturally found in all kinds of milk, including human milk. It can also be used as an ingredient in some foods. To digest lactose your body contains the enzyme lactase, which is produced by our bodies in the small intestine. Lactase splits the lactose into two smaller simple sugars, glucose and galactose, so it can be absorbed from the intestine into your bloodstream to provide energy.


When a person doesn’t have enough of the lactase enzyme to break down all of the lactose, they are said to have lactose maldigestion. The undigested lactose passes through the small intestine to the colon. In the colon, natural bacteria ferment the lactose and produce acids and gas. This combination of events can cause the symptoms of lactose intolerance, which refers to the gastrointestinal symptoms associated with incomplete digestion of lactose. Symptoms of lactose intolerance usually start about 20 minutes to an hour after consumption of dairy, and may include bloating, abdominal pain and swelling, diarrhoea, gas and nausea.

Lactose maldigestion does not necessarily result in symptoms of lactose intolerance. Most people with lactose maldigestion can eat some lactose-containing foods, such as dairy, without feeling unwell.



There are three types of lactose intolerance:


1. Primary lactose intolerance: The decreases of lactase production as you reach adulthood.

2. Secondary lactose intolerance: injury or illness, such as IBS or gastroenteritis, leads to damage of the lining of the small intestine. It's usually temporary but can be permanent if caused by an underlying disorder such as Crohn's disease.

3. Congenital lactose intolerance: a rare form of lactose intolerance when a baby is born with the condition. A baby with the condition will have had to inherit it from both parents carrying the defective form of the gene. Lactose-free formulas are required.



Most people are born with the ability to produce the lactase enzyme because breast milk, like cow’s milk, contains lactose. Adults are likely to have lactase deficiency since lactase levels start to decrease past childhood. Your chance of developing lactose intolerance later in life is also influenced by a range of factors, including:


1. Genetic predisposition: The ability to digest lactose varies between different races. The tendency to produce less lactase enzyme with age is more common in people of Asian, African, South American, Southern European, and Australian Aboriginal heritage than in people of Northern European descent.

2. Medical conditions: Temporary lactose intolerance may also occur in response to malnutrition or gastrointestinal infections, particularly in infants. These causes of lactose intolerance are usually only temporary, and milk and other dairy products can be slowly reintroduced into the diet.




Tests to diagnose lactose intolerance include:

* Lactose tolerance test: after drinking a lactose-containing liquid, a blood test is taken to check if glucose levels have risen. No rise indicates that the body isn't properly absorbing the drink.  

* Hydrogen breath test: measures the hydrogen in your breath. High levels of exhaled hydrogen show that you lactose isn't fully digested and absorbed.  

* Elimination diet: foods with lactose are removed from the diet to monitor if this has helps reduce symptoms.


Do not self-diagnose lactose intolerance, as there could be other medical issues causing similar symptoms. If you are concerned, ask your doctor to test you for lactose intolerance.



As one of the five food groups, dairy foods such as milk, cheese and yogurt are important for good nutrition throughout childhood and adulthood. Milk, cheese and yogurt provide over ten essential nutrients, including:  

* Protein  

* Carbohydrate (lactose)  

* Vitamins (A, B12 and riboflavin)  

* Minerals (calcium, phosphorus, magnesium, potassium and zinc)


People with lactose maldigestion DO NOT need to eliminate dairy foods from their diet. Many dairy foods do not contain large amounts of lactose. For example, most cheeses contain virtually no lactose and are usually well tolerated. Yogurt is also generally well digested as it contains bacteria that ferment (or consume) the lactose.


Research has shown that the majority of people with low lactase enzyme levels can consume at least one cup of milk (about 12 grams of lactose) a day. Research has also shown that if people with lactose maldigestion drink milk with different meals over the day, up to 2 cups of milk a day can be drunk without experiencing symptoms of lactose intolerance. Dairy foods such as milk, cheese and yogurt play an important role in a balanced diet. Three serves a day will provide enough calcium for most people. One serve is equal to 1 glass (250mL) of milk, a tub (200g) of yogurt or 2 slices (40g) of cheese.

People who remove dairy foods from their diet to treat lactose intolerance, have an increased risk of low bone mineral content and perhaps of developing osteoporosis (brittle bone disease) later in life. That’s because dairy foods are rich in calcium and other bone building nutrients which play an essential role in building and maintaining strong healthy bones.

While dairy foods do not need to be eliminated from your diet if you are lactose intolerant, the amount of lactose that can be tolerated will vary from person to person. Some tips to help you include your 3 serves of dairy every day:


* Choose smaller serves of dairy e.g. distribute milk intake into small serves spread out over the day.  

* Build up your tolerance. Start small and gradually increase your milk consumption  

* Regular fat milk may be better tolerated than low fat or skim milk. Fat slows the passage of lactose through your digestive system giving the lactase enzymes more time to break down the sugar.  

* Eat dairy with other foods: This slows the digestion so may reduce lactose intolerance symptoms.  

* Yogurt is often better tolerated than milk; and  

* Cheese is low in lactose and is well tolerated.  

* Have soy foods; they are lactose free, a good source of calcium and a good substitute for milk or milk products.  

* Watch for hidden lactose: check pre-packaged products such as cereals and muesli bars. Read food labels and watch for whey, milk by-products, milk solids, milk sugar and non-fat dry milk powder.

* Dairy-free probiotics (e.g. GastroHealth Dairy Free) can help maintain a healthy digestive system and help with symptoms of lactose intolerance.

If you still have problems, try low lactose milk or a lactose digesting preparation (available from chemists).