From: kja@cbnewsf.cb.att.com (krista.j.anderson)
Subject: What I Learned about Calcium and Milk (long)
Organization: AT&T
Date: Wed, 11 Nov 1992 17:44:10 GMT

CALCIUM occurs naturally in many foods either bound to organic
compounds or, probably more often, in the the form of inorganic
salts.  In milk, it occurs as an ion in dissolved salts with other
minerals.

There are only three reasons I know of why calcium in a food might
not be usable.  One is that it could be bound to oxalic acid or
oxalates.  Two is that it could be in solid form.  Three is that it
could be bound to fiber.  This last is not a major problem except
in undernourished people.  The second problem tells us that certain
supplements or foods, such as bone meal or dolomite, are less
effective than those that provide calcium in solution or in a form
that readily dissolves in the body.

OXALIC ACID renders the calcium unusable in spinach, rhubarb, beet
greens, sorrel and chard.  Amounts in other foods are negligible
and the amounts in the foods mentioned are not enough to bind
calcium from other foods.  Also note that contrary to what is
written in some books [1] tap water usually contains only small
amounts of calcium.

GOOD SOURCES of CALCIUM accounting for oxalic acid include:
Dairy products (but they vary, so check dietary charts)
Several fish and shellfish (ditto)
Bok choy
Broccoli
Collard greens
Mustard greens
Turnip greens
Dandelion greens
Kale
Okra
Saurkraut
Seaweeds, probably, but not all have been tested
Other - many fruits and vegetables contain moderate amounts of
        calcium, such as soybeans, white beans, almonds, Brazil
        nuts, filberts, oranges, molasses, figs, dates, and so on
        Refer to your favorite food composition charts
        Soymilk and some orange juices are fortified with calcium
        Check the labels

MILKS     Calcium          (%Protein   %Casein  %Whey)   %Fat    %Lactose
Cow       290 mg per cup      3.5        82       18      3.7     4.9
Goat      315
Human      81                 1.1        40       60      3.8     6.8
Buffalo   412
Reindeer  620

BREASTMILK is of course ideal for human infants.  The faster a baby
animal grows, the more calcium and protein it needs in its milk.
Since human babies grow more slowly than the other mammals listed,
they need more carbohydrate and less protein and minerals. 

Breastmilk is easier than cow's milk for infants to digest because
it contains more whey proteins and fewer curd proteins.  This means
that in the stomach acid, it forms soft, loose curds with more
protein remaining free in the liquid.  The higher content of
lactose also makes the calcium more easily absorbed and in general,
lactose aids calcium absorption.  An acidic environment also makes
calcium absorption more efficient.

Infants under one year old should not be given cow's milk because
of the possibility of developing an intolerance to the proteins.
Estimates of cow's milk intolerance range from 1 in 14 to 1 in 300
children.

Lactose (milk sugar) intolerance is about 10% for white Americans,
70% for African, Jewish or Native Americans, and about 80% for
Asian and Middle Eastern Americans.  Culturing milk products
destroys most lactose so that yogurt and some cheeses are
tolerable.  People who are lactose intolerant can drink about 1 
pint of milk throughout the day, but not all at once.

Milk and cheeses do contain significant amounts of sodium, so those
who watch sodium in their diets may prefer other sources of calcium.

RAW MILK has not been pasteurized and while it may be certified,
this is still no guarantee that it is free of disease-causing
microbes.  Although I had put Adelle Davis away on a dusty shelf a
long time ago because she has been proven wrong on so many counts,
I dragged out two of her books the other night and found that she,
apparently, is the instigator of the raw milk claims.  She had 
written decades ago that calcium is less available from "heated"
milk because it somehow comes out of solution.  This is a
ridiculous claim with no basis in reality.

Pasteurized milk does lose its trace amounts of thiamine and
vitamin C, but those aren't the nutrients you normally associate
with milk anyway.  It has just as much calcium available for use as
raw milk and is safer.  It is also more likely to have added
vitamins and to be homogenized and to be lower in saturated fats.

FATS in milk do indeed help in the absorption of vitamin D which in
turn helps calcium absorption.  However, whole milk with 4% fat is
more than necessary (I think).  Lowered fat milk or skim milk along
with unsaturated fats in other foods would still allow sufficient
absorption.  Some say that children need more fats, so that skim
milk is not recommended for them (although I would think that
vegetable oils or fish oils would be a better source than whole
milk).  I personally don't use skim milk because it seems to spoil
faster than 1% or 2%. 

USES FOR CALCIUM in the body are not limited to bone structure.
Calcium is used:
1. in bone and tooth structures
2. as a catalyst for blood clotting
3. to regulate movement of molecules across cell membranes
4. for nerve impulse transmission
5. to regulate muscle contraction and relaxation, including heart
6. to activate some digestive enzymes and B12

BONES are made of tough collagen webbings reinforced by crystalline
mineral deposits including calcium, phosphorus, magnesium and
others, but mostly in the form of calcium phosphate salt.  Collagen
is fibrous protein that also forms tendons and ligaments.  Teeth
are of similar composition to bone, but the mineral crystals are
larger and more tightly packed, making them a denser material.

Because of its crucial cellular functions, calcium is maintained in
the blood at a certain level.  If the level falls too low, the
parathyroid glands produce parathyroid hormone which increases the
blood levels of calicum ions in several ways.  It induces the
kidneys to convert vitamin D to its active form, dihydroxy-vitamin
D and this aids absorption of calcium in the intestines.  The
kidneys also reabsorb more calcium in response to parathyroid.

RESORPTION of calcium from the bones is increased in order to
raise the blood level.  This is a normal process since the bones
are the storage area for calcium and other minerals.  It is normal
for 600-700 mg of calcium to be resorbed from and deposited into
the bones daily.  In growing children, more is deposited; in
younger adults there is no net gain or loss; and in adults over 35
there tends to be a loss of bone calcium.  Normally, 320 mg of
calcium are excreted each day, but is expected to be replaced by
calcium in the diet.  If the loss is abnormally fast or abnormally
large, it is called osteoporosis and leads to porous bones subject
to breaking.  The jaw is one of the first bones to show signs of
loss, along with the ribs and spine.

OSTEOPOROSIS can be prevented, sometimes even halted with a change
in diet and lifestyle.  Adequate calcium and vitamin D are needed
in the diet, but equally important is sufficient weight-bearing
exercise.

I don't fully understand how the body's muscles and bones respond
to reasonable demands on them, but somehow they do.  Hence, when we
walk, jog or cycle, the stress on the bones causes absorption of
the mineral to increase for increased deposition, making a denser
bone that can more easily tolerate the bone loss of normal aging.
EXERCISE also improves blood flow and nutrients to the bones, and
favors hormones that help prevent bone loss.

HEREDITARY factors also influence who is at risk for osteoporosis.
Smaller, thinner people have less calcium to lose and therefore a
greater risk.  Women are more at risk than men, who have 25-30%
more bone mass.  People of northern European heritage as well as
Chinese and Japanese, are at greater risk than those from the
Mediterranean regions of Europe, and African Americans have the
lowest risk with bones that are 10% denser than those of white
Americans. 

PREGNANCY can cause bone loss if there is insufficient calcium in
the diet.  However, the body's absorption of calcium increases in
times of need, and pregnant women may absorb 75% of the calcium
they ingest as opposed to 10-30% absorption in others.

The high levels of estrogen and progesterone during pregnancy and
lactation increase absorption.  Conversely, when those hormones
suddenly decrease during menopause, there may be significant bone loss.
After menopause, the amount of bone loss levels off, but absorption
of calcium may decrease to only 7%.  Taking estrogen during and
after menopause can decrease the risk of osteoporosis, as can
taking oral contraceptives beforehand.  Women who have gone through
the weight-bearing exercise of two or more pregnancies have a
reduced risk of osteoporosis. 

PHOSPHOROUS and calcium should be about equally balanced in the
blood and bones, but in children the calcium level should be
higher.  Most books I read felt that excessive phosphorous in the
diet could decrease absorption of calcium, but one of them [1] felt
that it was not a significant factor because even though it
decreases calcium absorption in the intestines, it also decreases
calcium loss in urine.

ALCOHOL, caffeine and smoking were vices generally associated with
bone loss, with alcoholism in particular being unhealthy.  Duh.
Both caffeine and excessive protein tended to cause calcium to be
excreted in urine instead of being reabsorbed by the kidneys.  In
the case of PROTEIN, this is due to the sulfate by-products of
protein catabolism which draw calcium and magnesium from the bones
to neutralize the sulfate ions in order to maintain the body's pH.
Excess protein intake also increases the need for water due to its
metabolic by-products.

STRESS is thought to decrease absorption of calcium.  Also phytates
in the brans of grains can bind with Ca as well as other minerals,
but is probably not a major factor.  Phytic acid in wheat bran is
destroyed by yeast metabolism in baked breads.  Excessive sodium
also tends to decrease absorption of calcium.  Fluoridated water
can help the bones to retain calcium.

Current recommended daily allowances were thought to be too low in
most of the books I read.  Rather than 800 mg for adults, they
recommended 1000-1500 mg.  However, one book warned the reader not
to exceed 1500 mg; early symptoms of milk alkali syndrome are
nausea, headache and weakness.  Also note that excessive vitamin D
or vitamin A can contribute to calcium loss in addition to being
toxic.

CONCLUSIONS for me are that I still think dairy products are good
sources of calcium for people who can and wish to eat/drink them,
although I will add the caveat that cheeses vary in calcium
content, with some being relatively poor sources compared to their
protein content; all may be checked on nutrition charts.  I still
think raw milk is a potentially dangerous idea.  I still think it's
best not to take in excessive protein, sodium or phosphorous as
well as alcohol and caffeine.

More and more, I find myself thinking that in general, an exercise
plan may be more important than scrutinizing one's diet in detail.

For myself, since I've been growing more suspicious that I may have
a mild intolerance to milk, I will probably try to add more greens
to my diet and may also take supplements, although I suppose taking
supplements should be preceded by a talk with my doctor.

REFERENCES
1. Healey, Robert P. and Barger-Lux, M. Janet, _Calcium and Common
   Sense_, NY:Doubleday, 1988.
2. Granger, Laura, _Calcium and Nutrition_, Conn:Grolier Education
   Corp., 1988. 
3. Pritikin, Nathanial, _The New Pritikin Program_.
4. Winick, Myron, _The Columbia Encyclopedia of Nutrition_,
   NY:G.P.Putnam's Sons, 1988.
5. McGee, Harold, _On Food and Cooking_, NY:Collier Books, 1984.
6. Brody, Jane, _Jane Brody's Nutrition Book_, NY: W.W. Norton,
   1981.
7. Crowley, Leonard V. and Abrams, Charol, _Physiology_,
   PA: Springhouse Corp, 1993.  <-  that's what it says
8. Hausman, Patricia, _The Calcium Bible_, NY:Rawson Assoc., 1985.
9. Joneja, Janice Vickerstaff and Bierlory, Leonard, _Understanding
   Allergy, Sensitivity & Immunity_, NU: rutgers, 1990.

Not Recommended:
Davis, Adelle, _Let's Have Healthy Children_, 1951.
Davis, Adelle, _Let's Eat Right to Keep Fit_, 1954.
-- 
Krista Anderson
krista@ihlpf.att.com  or  ihlpf!krista@att.att.com  or  att!ihlpf!krista
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