Lactose intolerance is the condition in which lactase, an enzyme needed for proper metabolization of lactose (a constituent of milk and other dairy products), is not produced in adulthood. A hydrogen breath test is required for a clinical diagnosis. With lactose intolerance, the result of consuming lactose or a lactose-containing food is excess gas production and often diarrhea. In western cultures milk products are nearly ubiquitous and are contained in at least a small amount in almost all recipes, restaurant dishes, and processed food. People with lactose intolerance need to read food ingredient labels carefully if they wish to avoid consuming lactose.
There is no "treatment" or "cure" to lactose intolerance. There have been some cases where the intolerance has somehow diminished with time; this has not been studied scientifically, however, and whether it is a case of desensitization remains to be seen. It should be remembered that lactose intolerance is not a binary (all-or-nothing) condition: the reduction in lactase production, and hence, amount of lactose that can be tolerated varies from person to person, and may change with age. The management of lactose intolerance involves avoiding lactose-containing products, use of alternative products or artificial lactase enzyme medication (such as pills that are taken when eating or drinking a product containing lactose).
Since each individual's tolerance to consumed lactose varies, according to the National Institute of Health, "Dietary control of lactose intolerance depends on people learning through trial and error how much lactose they can handle."
Many people are more tolerant of yogurt than milk because it contains lactase produced by the bacterial cultures used to make the yogurt. Also, hard cheeses (e.g. Swiss) produce far less reaction than the equivalent amount of milk because the cheese making and ageing processes greatly reduce the amount of lactose. A typical Swiss or Cheddar might contain 5% of the lactose found in whole milk, while long-aged cheeses contain almost no lactose at all.
It is important for lactose intolerant people to especially be careful in avoiding products that whilst not apparently dairy (or are dairy but normally contain low amounts of lactose) nonetheless contain lactose. Such products include commercial sausages (notably frankfurters), medications which may contain lactose as a filler, most meal replacement and protein bars, cottage cheese, and even yogurts containing carageenan or gelatin.
Reduced or entirely lactose-free products (using milk substitutes such as soy milk, almond milk, or rice milk) are available allowing lactose-intolerant people to maintain approximately the same diet as those who are tolerant, without having to purchase medication or significantly alter their eating habits.
The food industry has successfully managed to create low-lactose or entirely lactose-free products to replace the regular items, without loss in quality. Lactose-free milk can be produced by passing milk over lactase enzyme bound to an inert carrier: once the molecule is cleaved, there are no lactose ill-effects. Alternatively, a harmless bacterium such as L. acidophilus may be added, which affects the lactose in milk the same way it affects the lactose in yoghurt.
Lactase-enzyme medication products aim to replace the deficiency in lactase production and so allow consumption of normal lactose-containing dairy products. Their cost may offset their benefit compared to using lactose-free products in ones own home, but they give dietary freedom when eating out.
Most commonly these are packaged in tablet form allowing a person to tolerate milk products for about 30-45 minutes after taking a pill. In addition solutions of lactase enzyme can be obtained; a few drops being added to a bottle of normal milk to cleave the contained lactose.
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