Lactose intolerance is a an inability to produce enough lactase, which is required to fully digest the lactose in milk. Lactose intolerance is experienced by a large proportion of the World’s population. Only the mainly white populations of the North America, Western Europe and Australasia maintain the ability to digest milk following childhood. As a result, ready to eat breakfast cereal with milk is only popular as a breakfast choice in these areas. Lactose is complex there are different severities of the disorder. Predicting the symptoms of a particular individual is therefore not an exact science. A more descriptive term may be lactose deficiency, whereby the symptoms of the individuals are more accurately described on a sliding scale of severity depending on the degree of deficiency. In this regard absolute lactose intolerance should be limited as a description of those who show no ability to produce lactase and who do not show a rise in blood sugar following consumption of milk, irrespective of symptoms.
Researchers have investigated the capacity of lactose intolerance individuals to withstand varying amounts of milk and lactose. For example in one study, researchers1 administered varying amounts of lactose in water or lactose as milk to a group of subjects over a 10 week period. Symptoms of lactose intolerance such as bloating, cramps, flatulence, diarrhea and gas were then recorded, and the blood glucose rises monitored. Of the 35 subjects observed, only 16 were lactose intolerant. Being non-white was significantly associated with lactose intolerance. Lactose tolerant subjects experience a mean blood sugar rise of 32 mg per 100 mL, whereas the mean blood sugar rise for lactose intolerant subjects was 6.7 mg per 100 mL. All the lactose intolerant subjects reported symptoms of lactose intolerance except for one individual. However, the degree and number of symptoms experienced was not related to the rise in blood sugar observed by the researchers.
The lactose intolerant subjects were able to consume 15 grams of lactose in water with little or no symptoms being evident. Many of the subjects could consume higher quantities of lacrosse than this. When milk was ingested by the lactose intolerant subjects quantities of lactose of 15 or 30 grams did not cause severe symptoms in many of the subjects, and milk is low amounts seemed to be tolerated. The lactose tolerant subjects could generally consume much high concentrations of lactose than the lactose intolerant subjects as expected. However, higher doses of lactose did cause discomfort in some lactose tolerant subjects. As expected, food diaries showed that the lactose intolerant subjects drank significantly less milk compared to lactose tolerant subjects. These results support a large body of evidence that suggest that the symptoms experienced from drinking lactose are hard to predict and that lactose intolerant individuals can tolerate small quantities of milk, often with no obvious detrimental symptoms.
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