Someone wrote:
My understanding is that congenital lactose intolerance is very
rare. But these days I always seem to be coming across people who claim to
have this condition.

Congential lactose tolerance is extremely rare.  Congenital means "born with
it" -- it is indeed the extremely rare baby who is not able to digest
lactose when born.  However, with the exception of European populations and
a few African and Asian populations who have a long history of dairying
(whether from cows, horses, asses, goats, sheep, camels, etc.) -- such as
the Fulani of West Africa, the cattle-herding people of East Africa, and a
couple of groups in India, the vast majority of the people in the world are
not able to digest lactose after mid-late childhood (6-10 years of age).
When you live in a society that is composed mostly of European descendants,
as the US mostly is, it can be difficult to understand that most people in
the world are lactose intolerant after childhood.  Most Asians, most
Africans and African-Americans, most Native Americans are lactose intolerant
after childhood.

The range of symptoms from the lack of lactase, therefore the inability to
digest lactose, can range from completely asymptomatic to extremely serious
gastrointestinal distress (bloating, gas, cramps, vomiting, and diarrhea).
Some people have mild symptoms, others have serious symptoms.  For some
people it takes a LOT of lactose to trigger symptoms, such as a big glass of
milk and a bowl of ice cream.  For other people, even the cheese on a pizza
can be enough to land them in the bathroom for 3 days.  Some people find
that their symptoms wax and wane over the months and years, with some people
getting more tolerant or lactose with age, and others get less tolerant, and
still others going back and forth.

How much lactose is in a particular milk product depends on how it was
processed.  Some cheese-making processes (but not all) involve bacteria that
digest the lactose, so the cheese has little lactose.  Likewise for some
yogurt or fermented milk products.  In societies where fermented milk
products are common, most people are still lactose intolerant as adults.

>people have been drinking the milk of other mammals and making various
> >other foods and beverages from them for a very long time - goats, >sheep,
>horses, cows, etc.

About 6,000 to 8,000 years is the best current guess.  But remember, again,
that while SOME populations have been including non-human mammal milks in
their diet for many thousands of years, MOST populations have not.  This
includes most of Asia, most of Africa, all of the Americas (North, Central,
South) before the arrival of Europeans, Australia and the Pacific Islands.
Milk-drinking really has been limited to Europe, north Africa, a few
societies in West and East Africa, and a few societies in India.

Also, while those who have it certainly know the difference between an
allergy to cows' milk protein (usual reactions include vomiting, hives,
anaphylactic shock), the "man and woman on the street" often use the term
"milk allergy" to refer to lactose intolerance.

I am intrigued by the idea that people would co-opt lactose intolerance to
get out of drinking milk when they just didn't like milk.  Of course, if
often turns out that people who "don't like milk" are, in reality, lactose
intolerant.

Kathy Dettwyler

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