This article is from the Children Allergies and Asthma FAQ, by Eileen Kupstas Soo email@example.com with numerous contributions by others.
Lactose intolerance is the inability to digest lactose, found in animal
milk (including human milk, which, in fact, has about twice has much
lactose as cow's milk). An enzyme called lactase is required to digest
lactose. When this enzyme is missing, the following symptoms may
occur: abdominal cramps, diarrhea, gas, a feeling of bloatedness.
Symptoms may occur within an hour, or up to several days later. The
intensity of symptoms varies widely.
Lactose intolerance can be self-diagnosed by eliminating milk and dairy
products from your diet for two weeks, then reintroducing milk (a glass
or two), and seeing what happens. Your doctor can administer a couple
of tests to confirm lactose intolerance (basically involves drinking a
sweet drink containing a lot of lactose on an empty stomach and
monitoring blood levels of glucose -- no rise in glucose means the
lactose is not being absorbed; the other involves checking breath
levels of hydrogen).
If you are diagnosed with lactose intolerance, you have a variety of
options. Lactase is available by prescription (Lactaid), and can be
added to milk (drops) or taken with food containing dairy products
(tablets). Some people may have adverse reactions to this medication,
however (in tablet form -- the reaction is believed to be allergic.
Drops seem to be ok.). Lactose reduced milk and cheeses are available
in some areas. Aged cheeses, yogurt and sour cream may be tolerable
(most of the lactose has already been converted). You can find your
level of lactose tolerance by either cutting out dairy products
entirely and slowing working them back into your diet, or you can
slowly eliminate them until you stop having difficulties. Tables
indicating lactose content for milk and milk products are available
(see Zukin below).
Some believe that lactose intolerance is, in fact, the human (and
mammalian) norm, rather than an aberration, citing in support
statistics that indicate most of the world's population is lactose
intolerant (Europeans and those of European descent being the
exceptions), and the tendency to lactose intolerance with increased