IS THAT ALL OF THE TROUBLE?
Sorry, there's more. Remember lactose? This is the
principal carbohydrate of milk. It seems that nature provides new-borns
with the enzymatic equipment to metabolize lactose, but this ability often
extinguishes by age 4 or 5 years.
What is the problem with lactose or milk sugar? It seems
that it is a disaccharide which is too large to be absorbed into the blood
stream without first being broken down into monosaccharides, namely
galactose and glucose. This requires the presence of an enzyme, lactase
plus additional enzymes to break down the galactose into glucose.
Let's think about his for a moment. Nature gives us the
ability to metabolize lactose for a few years and then shuts off the
mechanism. Is Mother Nature trying to tell us something? Clearly all
infants must drink milk. The fact that so many adults cannot seems to be
related to the tendency for nature to abandon mechanisms that are not
needed. At least half of the adult humans on this earth are lactose
intolerant. It was not until the relatively recent introduction of dairy
herding and the ability to "borrow" milk from another group of mammals
that the survival advantage of preserving lactase (the enzyme that allows
us to digest lactose) became evident. But why would it be advantageous to
drink cows' milk? After all, most of the human beings in the history of
the world did. And further, why was it just the white or light skinned
humans who retained this knack while the pigmented people tended to lose
it?
Some students of evolution feel that white skin is a
fairly recent innovation, perhaps not more than 20,000 or 30,000 years
old. It clearly has to do with the Northward migration of early man to
cold and relatively sunless areas when skins and clothing became
available. Fair skin allows the production of Vitamin D from sunlight more
readily than does dark skin. However, when only the face was exposed to
sunlight that area of fair skin was insufficient to provide the vitamin D
from sunlight. If dietary and sunlight sources were poorly available, the
ability to use the abundant calcium in cows' milk would give a survival
advantage to humans who could digest that milk. This seems to be the only
logical explanation for fair skinned humans having a high degree of
lactose tolerance when compared to dark skinned people.
How does this break down? Certain racial groups, namely
blacks are up to 90% lactose intolerant as adults. Caucasians are 20 to
40% lactose intolerant. Orientals are midway between the above two groups.
Diarrhea, gas and abdominal cramps are the results of substantial milk
intake in such persons. Most American Indians cannot tolerate milk. The
milk industry admits that lactose intolerance plays intestinal havoc with
as many as 50 million Americans. A lactose-intolerance industry has sprung
up and had sales of $117 million in 1992 (Time May 17, 1993.)
What if you are lactose-intolerant and lust after dairy
products? Is all lost? Not at all. It seems that lactose is largely
digested by bacteria and you will be able to enjoy your cheese despite
lactose intolerance. Yogurt is similar in this respect. Finally, and I
could never have dreamed this up, geneticists want to splice genes to
alter the composition of milk (Am J Clin Nutr 1993 Suppl 302s).
One could quibble and say that milk is totally devoid of
fibre content and that its habitual use will predispose to constipation
and bowel disorders.
The association with anemia and occult intestinal
bleeding in infants is known to all physicians. This is chiefly from its
lack of iron and its irritating qualities for the intestinal mucosa. The
pediatric literature abounds with articles describing irritated intestinal
lining, bleeding, increased permeability as well as colic, diarrhea and
vomiting in cows' milk-sensitive babies. The anemia gets a double push by
loss of blood and iron as well as deficiency of iron in the cows' milk.
Milk is also the leading cause of childhood allergy.
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