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  • Q&A with Australian Health Practitioners

    What is the difference between primary and secondary lactose intolerance?

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    I am Accredited Practising Dietitian with a passion for helping people who suffer from food intolerance. I have 25 years of experience in this area … View Profile

    Primary lactose intolerance is a result of reduced ability to produce the enzyme lactase.  Secondary lactose intolerance is a result of disturbance in the bowel such as gastroenteritis and tolerance to lactose often returns after recovery.

  • 2


    Joy Anderson

    Dietitian, Nutritionist

    Joy is an Accredited Practising Dietitian and Accredited Nutritionist, as well as an International Board Certified Lactation Consultant (IBCLC). She has a special interest in … View Profile

    There are really two types of ‘primary’ lactose intolerance. One is extremely rare and occurs in infants with a genetic abnormality, such that the individual cannot make the enzyme, lactase. The other type is very common and is actually the normal human condition. It occurs in about 70% of the world's people, especially non-Caucasians. Like for other animals, the ability to make lactase is ‘switched off’ at about natural weaning age (about 5 years for humans). Milk is ‘baby food’.
    Secondary lactose intolerance occurs when the intestinal lining is damaged, even subtley. This damage can occur during gastroenteritis or when there is a food allergy or food intolerance in some cases, especially in infants. Once the damage heals, the lactase reappears.

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