FACT: Lactose intolerance can occur in individuals who have low levels of the enzyme lactase, which is needed to digest the naturally occurring milk sugar (lactose). Tolerance levels vary, with some individuals having no symptoms or only having digestive discomfort following the consumption of large amounts of lactose-containing foods.
In most cases, milk-based foods do not need to be completely avoided, but need to be limited to the person’s individual tolerance. Depending on the level of tolerance, most people can consume some lactose and this can promote tolerance. Typically, up to 12g at a time can be consumed with no, or minor, symptoms. Some dairy foods have negligible amounts of lactose (see graphic below).
Worldwide, it is estimated that about 65% of people do not express the lactase enzyme but it varies largely across populations, ranging from 4% to over 80% across different parts of the world. Due to genetic evolution, Ireland has a lower prevalence, with 4-5% affected.