[664] in Vegetarian_Support_Group
calcium and osteoporosis
daemon@ATHENA.MIT.EDU (elsiedee@MIT.EDU)
Mon Sep 18 14:06:24 1995
From: elsiedee@MIT.EDU
Date: Mon, 18 Sep 95 14:03:57 -0400
To: vsg@MIT.EDU
Here is a fact sheet from PCRM (Physicians' Committee for Responsible
Medicine) which summarizes some of the current thinking on the
calcium-protein-osteoporosis link. At the end you will find a useful
table which shows non-dairy sources of calcium.
Boning up on Calcium and Osteoporosis
*************************************
It is a common myth that people should increase their calcium intake.
Mostly, they are encouraged to take supplements and to drink more
milk. But milk may not "do a body good." The highest rates of
osteoporosis are in the industrialized Western nations--the biggest
consumers of milk. It turns out that keeping strong bones depends more
on preventing calcium loss than on increasing calcium intake.
Calcium in the Body
+++++++++++++++++++
Almost all of the calcium in the body is in the bones. There is a tiny
amount in the blood stream which is responsible for muscle
contraction, maintenance of the heartbeat, and transmission of nerve
impulses and other functions. Hormones control the amount of calcium
in the blood. Everyone constantly loses calcium through urine, sweat,
and feces, and it is renewed with calcium from the bones. In the
process, the body constantly breaks down and rebuilds bones.
Ultimately, the body's calcium is replaced by calcium from food.
Reducing Calcium Loss
+++++++++++++++++++++
Since the 1920's researchers have known that diets that are high in
protein, especially animal protein, cause calcium to be lost through
the urine.1 In nations with high rates of osteoporosis, protein intake
is generally high~usually more than twice the U.S. Recommended Daily
Allowance. Vegetarians have lower rates of osteoporosis than meat
eaters. This may be due to the lower protein intake of vegetarians.
Different types of protein also affect this loss. Meats are overly
high in protein and are high in a particular kind of protein building
block, called sulfur- containing amino acids. These cause increased
calcium loss.2
Caffeine and sodium also increase the rate at which calcium is lost
through urine. Alcohol inhibits calcium absorption and may also be
toxic to bone.3 Vitamin D, copper, zinc, manganese, fluorine, and
boron are all essential for good bone formation, and weight-bearing
exercise also increases bone mass and helps to prevent osteoporosis.4
Boron appears to help stop the loss of calcium. The best way to get
boron is through fruits, vegetables, and beans.
The Need for Calcium
++++++++++++++++++++
Throughout life, people's calcium needs change. Until about age 35,
people consume more calcium that their bodies lose. But around age 45,
the body begins to slip into "negative calcium balance"~slowly the
body loses more calcium than it takes in. As shown above, how rapidly
calcium is lost depends, in part, on how much protein is in the diet,
and the kind of protein it is. The loss of too much calcium can lead
to "soft bones," or osteoporosis.
Fighting Bone Loss
++++++++++++++++++
Most studies have shown that high doses of calcium do not slow bone
loss. In fact, many populations with high intakes of calcium also have
high rates of osteoporosis,5 probably because their high protein
intake causes significant calcium loss. Some African cultures consume
no dairy products and typically get only 175 to 475 milligrams of
calcium per day (800mg is the U.S. RDA), but they have low rates of
osteoporosis. Rates of hip fracture among different populations is one
way researchers measure the prevalence of osteoporosis. One such study
of ten nations revealed that as calcium intake increased, so did the
number of hip fractures. Such studies have also led researchers to
believe that exercise and other factors have more to do with
preventing osteoporosis than calcium intake does.
Absorbing Calcium
+++++++++++++++++
The body carefully regulates its calcium absorption. The average
person absorbs 30 to 70 percent of the calcium she or he eats, but the
more calcium taken in, the less the body will absorb. This is to
protect the body from overdosing on calcium. At the U.S. RDA of
800mg, the body may absorb as little as 15 percent of the total
amount. This may be one reason that high calcium intake does not
generally prevent bone loss.
While milk is a source of calcium, it certainly is not the ideal way
to get your daily dose. Dairy products, with the exception of skim
products, are loaded with saturated fat. Fat is directly related to
heart disease and cancer. Dairy products are also high in protein.
There are other reasons to worry about milk, too. Cows are routinely
fed antibiotics. These are then passed directly on to the milk
drinkers; antibiotics are detectable in one out of three cartons of
milk. Many people are also allergic to milk, and over three-fourths of
the world's population is lactose-intolerant, which means their bodies
lack the enzymes necessary to digest milk.
Great Sources of Calcium
++++++++++++++++++++++++
Dark green vegetables, such as broccoli and collard, mustard, and
turnip greens are much better sources of calcium than milk. A single
cup of broccoli contains almost a fourth of the U.S. RDA of calcium.
Another good source is calcium-fortified orange juice. Beans and
tortillas are also good sources of calcium.
Some people do need hormone treatments and/or calcium supplementation
for varying conditions. The risks and benefits should be discussed
with one's doctor.
Conclusion
++++++++++
Calcium is an essential nutrient and is needed for healthy bones
particularly during childhood and adolescence. While it is uncertain
how much calcium is actually needed, it is certain that diet affects
calcium balance. Calcium supplements are not the best way to control
osteoporosis for most people. A diet that is modest in protein,
complemented by exercise, is much more effective. Green leafy
vegetables and beans are good sources of calcium that are also
moderate in protein and very low in fat.
References:
+++++++++++
1. Hegsted M, Schuette SA, et al. Urinary calcium and calcium balance
in young men as affected by level of protein and phosphorus intake. J
Nutr 1981;111:553-562.
2. Marsh AG, Sanchez TV, et al. Cortical bone density of adult
lacto-ovo- vegetarian and omnivorous women. J Am Diet Asso
1980;76:148-150. 3. Rivlin, RS. Women's health: osteoporosis. Public
Health Reports 1986;131-135.
4. Schaafsman F, van Beresteyn ECH, et al. Nutritional aspects of
osteoporosis. Wld Rev Nutr Diet 1987;49:121-159.
5. Hegsted DM. Calcium and Osteoporosis. J Nutr 1986;116:2316-2319.
Calcium Sources
+++++++++++++++
Calcium is found in a variety of plant foods. The following are
low-fat, cholesterol-free sources of calcium.
Food Amount Milligrams of Calcium
Collard Greens 1 cup 355 mg
Bok Choy 1 cup 250 mg
Turnip Greens 1 cup 200 mg
Kale 1 cup 200 mg
Broccoli 1 cup 180 mg
Kelp (Seaweed) + cup 170 mg
Mustard Greens 1 cup 150 mg
Wakame (Seaweed) + cup 150 mg
Blackstrap Molasses 1 tablespoon 140 mg
Amaranth + cup 140 mg
Great Northern Beans 1 cup 140 mg
Dried Figs 5 figs 135 mg
Vegetarian Baked Beans 1 cup 130 mg
Navy Beans 1 cup 130 mg
Corn Tortilla 1 tortilla 120 mg
Fortified Orange Juice 6 ounces 120 mg
Kidney Beans 1 cup 115 mg
Black Beans 1 cup 105 mg
Okra 1 cup 90 mg
Acorn Squash 1 cup 90 mg
Pinto Beans 1 cup 85 mg
Tofu* + cup 130 mg
Soybeans* 1 cup 175 mg
* may be high in fat
For more information, contact:
++++++++++++++++++++++++++++++
Physicians Committee for Responsible Medicine
P.O. Box 6322
Washington, DC 20015
(202) 686-2210
