Lactose Intolerance

What causes lactose intolerance?  

Lactose intolerance is often a temporary condition that can occur after a bout of gastroenteritis (stomach bug) or alongside undiagnosed coeliac disease. It can also occur in the first few months of life until the levels of lactase have become fully established (developmental lactase deficiency).  

Who is affected by lactose intolerance?  

Certain populations, particularly Asian and African people, suffer from a genetic form of lactose intolerance where there is a gradual loss of ability to produce lactase over time (primary lactose intolerance). Primary lactose intolerance tends to be a condition seen in older children and adults – so you grow into lactose intolerance, not out of it.  

Diagnosis of lactose intolerance  

Diagnosis of lactose intolerance is usually made if the symptoms get better after excluding all sources of lactose from the diet for two weeks and this involves carefully reading food labels. Lactose rich foods are then re-introduced into the diet and if the symptoms come back, the diagnosis is confirmed. Lactose free, cow’s milk protein containing products, such as LactofreeTM yoghurts and cow’s milk, should be used where possible during the exclusion trial, to avoid confusing lactose intolerance with cow’s milk allergy. Cow’s milk allergy is much more likely in children under two years of age. It is important to visit your GP if you think you or your child may have lactose intolerance, as the symptoms can be similar to other conditions.  

Lactose intolerance for longer than six to eight weeks is extremely rare in infants and young children and a low lactose formula should not be used for longer than this. If the diagnosis is not clear, a hydrogen breath test can be arranged, so discuss this with your GP. Do not continue to avoid lactose and dairy products if symptoms have not been resolved. 

Low lactose diet 

This information is designed to help you get started on a lactose free diet. However, it is essential that once you have established that the strict exclusion of lactose from your diet has improved your symptoms you should then start to gradually re-introduce lactose containing foods, starting with those containing only small amounts of lactose. These would usually be the foods where you have checked the labels. Then try some hard cheese and yogurt. If there are still no symptoms, try having a small amount of normal cow’s milk on cereal or in drinks according to individual tolerance levels (the amount of lactose a person can tolerate without the development of symptoms). If you have any concerns about achieving an adequate intake of vitamins and minerals, you should ask your GP for a referral to a dietitian.  

Lactose intolerance is treated by following a low lactose diet. Most children and adults with lactose intolerance can tolerate small amounts of lactose in foods. Lactose may act as a prebiotic – feeding healthy gut bacteria and improving the absorption of minerals such as calcium, so try to include it if you can. 

Milk substitutes  

Breastfeeding and infant formula  

Breast milk and infant formula have very high lactose content which could be the cause of infantile colic in some breast and bottle fed babies. Reducing the lactose content of breast milk and formula by using lactase enzyme (ColiefTM) for the first few months of life may help if there are no other symptoms suggestive of cow’s milk allergy. ‘Comfort infant formulas’ also have a reduced lactose content and may help babies with colic. 

Lactose free formula  

If your baby gets gastroenteritis and the diarrhoea does not resolve after two weeks of illness, a six to eight week period on a lactose free formula may help. Then, your baby should be gradually re-introduced to normal formula. If the symptoms come back, it may be that your baby is now suffering from cow’s milk allergy and you should discuss this with your doctor. See our ‘Does my child have a Cow’s Milk Allergy Factsheet’ for more information. 

 Lactose free infant formulas still contain the cow’s milk proteins that are in normal infant formulas and so they are not suitable for babies with cow’s milk allergy. Lactose free formulas may help with symptoms of diarrhoea, bloating, colic, wind and nappy rash, as lactose can cause these symptoms if not digested. As cow’s milk protein is still in lactose free formulas however, your baby’s gut will still be inflamed. They may also suffer from other immune reactions affecting the skin and breathing e.g. rashes, blocked or runny nose. Once cow’s milk protein is excluded by using a hypoallergenic (low allergy) formula, the gut will heal and the baby should be able to tolerate some lactose again. See our factsheet ‘Cow’s milk free diet for babies and children’ for more information. 

Milk substitutes for older children and adults 

• LactofreeTM milk and products help to ensure that you still get all the nutrients that you would from a normal cow’s milk containing diet whilst avoiding lactose, so there should be no nutritional concerns if these are consumed as part of your daily diet. Cow’s milk and dairy foods are rich sources of energy, protein, calcium, iodine, vitamin A and riboflavin. These are essential for growth and development, bone and dental health. 

• Goat, sheep and other animal milks are not suitable for lactose intolerance, as lactose is the main sugar in all mammalian milks.  

• If plant based milks and products are used e.g. soya, oat, coconut, nut, hemp, choose those fortified with calcium, and find alternative sources for other key nutrients. You should seek referral to a dietitian if undertaking long term exclusion of cow’s milk for a child, or if you are concerned about the nutritional adequacy of your diet.  

• Rice milk should be restricted because of its naturally occurring inorganic arsenic content and it is not suitable as a main milk drink for children under four and a half years of age. 

Soya milk is lactose free but is not recommended for children under six months.  

How much milk substitute should I give?  

Under One year of age  

Most babies under one year of age need to take 600ml (20 floz/1 pint) of milk each day to meet their nutritional requirements, including a recommended calcium intake of 525mg daily. If breastfeeding, assume that one good breast feed is equivalent to a bottle of formula. If your baby consumes less than this, your baby may not be meeting their nutritional requirements and you should inform your GP or Health Visitor.  

One to three years of age  

Calcium requirements are lower in this age group (350mg calcium) and generally 300ml (10floz/ ½pint) of milk substitute is enough. However, your child may need more than this if they are not getting enough vitamins and minerals from the foods that they eat.  

Four years upwards  

Calcium requirements gradually increase back to around 500 mg daily, which requires an intake of the equivalent of 600ml (20floz/1 pint) fortified milk substitute a day. It is recommended that adults consume the equivalent of one pint of calcium fortified milk a day.  

Include dairy products  

Most children and adults with lactose intolerance can tolerate some low lactose foods (e.g. hard cheese, butter and yogurt), lactose in medications and even small amounts of cow’s milk without causing symptoms (Table 1). Up to 240ml cow’s milk (12 g lactose) is often well tolerated if spread throughout the day. Due to the benefits of lactose, try to include some if possible. LactofreeTM milk and products also help you get all the nutrients that you would from a normal cow’s milk based diet while avoiding lactose. 

Table 1: Sources of lactose and lower lactose alternatives Checking food labels 

Checking food labels 

 You will need to carefully check the ingredients list on food items and avoid foods which contain any of the following during the strict exclusion trial. However, afterwards you should be able to include some of these ingredients in your diet based on your level of tolerance: 

Example of a food label:  

Olive spread:  

INGREDIENTS: Water, Vegetable Oils (37%) [Rapeseed Oil, Palm Oil], Olive Oil (22%), Whey Powder (from Milk), Salt (1.1%), Emulsifier (Mono- and Diglycerides of Fatty Acids), Stabiliser (Sodium Alginate), Preservative (Potassium Sorbate), Colour (Carotenes), Flavouring, Vitamin A, Vitamin D.  

Allergy Advice! For allergens, see ingredients in bold 

Lactose containing check list  

Below are tables which give examples of lactose free foods and foods which may contain lactose. Please note that this is not an exhaustive list and you must always check labels as ingredients may change without any warning.