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Lactose Intolerance

What is lactose?

Milk and dairy products contain milk sugar which needs to be broken down to small bits so that the body can absorb them into the blood stream. This milk sugar called lactose is broken down by an enzyme called lactase in our intestines.

What is lactose intolerance?

Lactose intolerance is an inability to digest the milk sugar or lactose.

What causes it?

It is due to either a temporary or a permanent deficiency of the enzyme lactase. Lactase is present in the lining of the small intestine.

What are the types of lactose intolerance?

  1. Primary lactose intolerance (permanent)
    1. Congenital
      1. Rare
      2. Present at birth
    2. Delayed (adult form)
      1. Common among Asians
      2. Develop at around age 20 years
  2. Secondary lactose intolerance (temporary)
    • Damage/injury to the intestines due to Gastroenteritis
    • Bowel disease such as Coeliac Disease
    • Bowel surgery

How common is this condition?

  • Two thirds of all babies develop some degree of lactose intolerance
  • It is generally transient and do not cause harm
  • Normally, lactase start to decrease gradually after weaning
  • Some people continue to produce lactase all their lives; some (most Asians) will slowly stop producing lactase when they reach adulthood

What are the signs or symptoms of this condition?

Symptoms appear half an hour to 2 hours after a lactose meal

  • Fretful, crying baby
  • Stomach bloating, cramps
  • Passing liquid, frothy stools
  • Passing excessive gas
  • Excoriation over the skin folds of baby’s bottom


All the above symptoms do not only occur in lactose intolerance but may also occur in food allergy and other illnesses. Therefore, diagnosis should only be made after consultation with your doctor.

What problems can it cause?

Temporary lactose intolerance usually does not cause complications. However, severe untreated lactose intolerance can lead to :

  • Dehydration
  • Malnourishment
  • Poor weight gain or not thriving baby

What are the ways to treat this condition?

Diet is the only way to treat lactose intolerance. While avoiding food with lactose, take care to ensure that your child’s food is balanced and contain enough nutrients.

Always seek your doctor’s advice first.

Primary (permanent) lactose intolerance :

  • There is no cure
  • Avoid all food containing lactose
  • Infants on breast milk and standard milk formula – need to switch to lactose-free formula which may be a lactose free cow’s milk based formula or a soy based formula
  • Take care to ensure that food is balanced and contain enough nutrients

Secondary (temporary) lactose intolerance :

  • Reduce food containing lactose in diet
  • Alternate breastfeed with lactose free milk
  • May need to use lactose-free milk solely for short period
  • Resolves in about 2 to 4 weeks.You start your child back on normal diet after that.

What are the types of food that may contain lactose?

Many types of food can contain lactose, please read your food labels carefully.
Food containing lactose include :

  • Milk, dairy products (cheese, butter)
  • Chocolate and chocolate drinks
  • Ice-cream
  • Margarine
  • Bread, biscuits, cookies
  • Breakfast cereals
  • Candies, certain sweets
  • Condensed milk
  • Evaporated milk

Lactose is also present in food with the following ingredients :

  • Milk solids, non-fat milk solids
  • Whey, casein
  • Dry milk powder/solids
  • Curds

How can this condition be prevented?

To prevent symptoms, avoid all lactose containing food as mentioned above.

What are other important measures to be aware of?

  • Read all food labels for its content.
  • Be aware that lactose may be hidden in certain food products and may not be stated in the labels.
  • Consult a nutritionist if you are uncertain of the contents of specific foods
  • Do not keep changing milk formulas unnecessarily. Consult your doctor first.
Last reviewed : 28 August 2020
Writer : Dr. Lim Sern Chin
    Dato’ Dr. Lim Nyok Ling
Reviewer : Dr. Zainab bt. Kusiar