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| Introduction |
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| Part of youthfulness is straight posture
and resilience in the limbs and spine. If, on the other hand,
bone tissue wastes away, hips and wrists become fragile, and
the spine bows into a stooped appearance. This bone loss is
called osteoporosis, and is particularly common in women after
menopause. |
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| Osteoporosis
and Calcium Intake |
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Some populations have less osteoporosis than
others. Changes in diet and life-style may prevent it, although
the foods that are effective may not be the ones you would expect.
The dairy industry has used osteoporosis as a marketing tool,
but milk does not seem to be the answer. In countries where
dairy products are commonly consumed, there are actually more
hip fractures than in other countries. When put to the test,
most studies show that dairy products have little effect on
osteoporosis.52 As surprising as that may be, when
researchers have measured bone loss in postmenopausal women,
most have found that calcium intake has little effect on the
bone density of the spine. There is also little or no effect
on bone at the hip, where serious breaks can occur. Some studies
have found a small effect from calcium intake on bone density
in the forearm.53 The overall message seems to be
that, as long as you are not grossly deficient in calcium, supplements
and dairy products do not have much effect. Science magazine
(August 1, 1996) noted "the large body of evidence indicating
no relationship between calcium intake and bone density."54
Why not? For one thing, the amount of calcium in the bones is
very carefully regulated by hormones. Increasing your calcium
intake does not fool these hormones into building more bone,
any more than delivering an extra load of bricks will make a
construction crew build a larger building.
If milk, or calcium intake in general1 is not a good hedge against
bone loss after menopause, how about before menopause? That
too seems to follow the pattern. Researchers in Madison, Wisconsin,
USA, compared the diets of 300 premenopausal women aged twenty
to thirty-nine and measured their bone density. Calcium had
no measurable effect on bone density. Very low calcium intake
would probably lead to deficient bone formation, but calcium
intake spanning the normal dietary range made no difference:
high-calcium diets led to no stronger bones than the lower calcium
diets.55
Milk does contain calcium. But milk neither assures strong bones
in childhood nor does it protect bones in adulthood. For the
vast majority of people, the answer is not boosting calcium
intake but, rather, limiting calcium loss. As surprising as
it sounds, one major culprit in osteoporosis may be protein.
Diets that are high in protein, especially animal protein, cause
more calcium to be excreted.
When volunteers eat high-protein meals, they lose calcium in
their urine. If they consume more modest amounts of protein,
they lose much less calcium in their urine. What is apparently
happening is this; Amino acids, which are the building blocks
of proteins cause the blood to become slightly more acidic.
To neutralise this acidic effect, bone material is dissolved,
which is believed to lead to the loss of calcium in the urine.
The problem is not just the quantity of protein consumed but
also the type of protein. Meats are high in a type of protein
building block called sulfur-containing amino acids. These are
particularly likely to aggravate calcium loss. Meats also contain
large quantities of phosphorus, which can impair calcium balance.56 |
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| Role of Phosporous |
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Although the role of phosphorous in osteoporosis
is far from clear, scientists believe that diets in which phosphorus
and calcium intake are roughly equal help keep calcium in the
body, while diets in which the two are unbalanced are thought
to harm calcium balance. Beef has a high phosphorus-to-calcium
ratio, about 15:1. Chicken breast is similar, about 14:1, a
peach is about 2:1. Boiled broccoli has a phosphorus-to-calcium
ratio of about 0.4:1Green leafy vegetables provide generous
amounts of calcium without the animal protein of meaty diets.
In fact, green vegetables such as broccoli, kale, etc. are loaded
with calcium.
A recent report in the American Journal of Clinical Nutrition
found that calcium absorbability was actually higher for kale
than for milk and concluded, "greens such as kale can be
considered to be at least as good as milk in terms of their
calcium absorbability."57
One cup (8 fluid ounces/227.2ml) of milk contains 291mg of calcium.
That is a substantial amount. But only about 30 percent of it
is absorbed, and that glass of milk also contains 8 grams of
animal protein to encourage the loss of calcium. Green vegetables,
beans, and enriched flour are rich in calcium, and fortified
orange juice supplies substantial amounts of calcium.58
Table 1 (below) shows the calcium content of many common foods. |
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Table 1: CALCIUM RICH FOODS
(Calcium (mg-per 1 cup, boiled.) Unless otherwise
stated |
| calcium
(mg) |
calcium (mg) |
| Vegetables |
Grains |
| Brocolli |
178 |
Brown Rice |
23 |
| Cauliflower |
34 |
English Muffin1 medium |
92 |
| Celery |
54 |
Pita Bread 1 piece |
31 |
| Kale |
94 |
Wheat Bread 1 slice |
30 |
| Onions |
58 |
Wheat Flour |
22 |
| Kumera |
70 |
Wheat Flour |
49 |
| Potato 1 medium |
20 |
|
|
| Carrots 2 medium |
38 |
|
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| Legumes |
Fruits |
| Chickpeas |
78 |
Apple 1 medium |
10 |
| Green Beans |
58 |
Banana 1 medium |
7 |
| Kidney Beans |
50 |
Figs,dried 10 medium |
269 |
| Lentils |
37 |
Navel Orange 1 medium
(Calcium
fortified) |
300* |
| Lima Beans |
52 |
Pear 1 medium |
19 |
| Navy Beans |
128 |
Raisins 3 4 cup |
53 |
| Peas |
44 |
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| Soybeans |
175 |
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| Tofu 1/2 Cup |
258 |
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| Fruits and veges also provide boron, an element
which appears to be important in preventing the loss of calcium,
according to Dr. Forrest H. Neilsen, a research nutritionist
with U.S. Dept. of Agriculture. The best way to get boron, according
to Dr. Neilsen, is through a balanced diet containing an abundance
of fruits, veges, nuts and legumes. Wines also contain appreciable
amounts of the element. Animal products, including milk, have
little or no boron. No one yet knows how much boron the body
needs, but Table 2 (below) shows what foods are rich sources
of boron. |
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| Table 2. The Boron All-Stars |
| mg per 100ml or 100mg dry weight |
| Apple Sauce |
.279 |
Grape Juice |
.0202 |
| Broccoli Stalks |
.089 |
GreenBeans |
.046 |
| Broccoli Tops |
.185 |
Orange Juice |
.041 |
| Carrots |
.075 |
Peaches |
.187 |
| Cherries |
.147 |
Pears |
.122 |
Source: J. McBride
It, "Banishing Brittle Bones With Boron."
Agriculture Research (Nov-Dec), 1987,35(10),p13
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| Hormones play a major role in bone structure.
After menopause, bone loss is often aggressive, and as a result,
doctors often prescribe hormone replacements. Such treatments
are effective in delaying osteoporosis, although their overall
health risk remains controversial. Exercise is also important.55,
59 If bones are not being used, they have little reason
to preserve their strength. In addition, alcohol and tobacco
aggravate bone loss.53, 55Although the calcium craze
has been founded largely on myth, this does not mean that the
body does not need calcium. If you really are consuming very
little calcium - say, below 500 mg per day - you may run into
trouble.55 However, it is very easy to get a day's
supply of calcium.If you choose to supplement, calcium-fortified
orange juice has an advantage over milk in that it contains
no animal protein and is a form of calcium that is more easily
absorbed than that in calcium carbonate-supplements.58
When replacement hormones are used, calcium supplements have
been shown to be a helpful adjunct in slowing bone loss. |
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| References |
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Dr Barnard is president of (PCRM) Physicians Committee for
Responsible Medicine. http://www.pcrm.org/
PO Box 6322, Washington, DC 20015. USA.
52. Dietary calcium intake and rate of bone loss in women. Journal
Clinical Investigation 1987;80:979-82
53. Dawson-Hughes B. Calcium supplementation and bone loss:
a review of clinical trials. American Journal of clinical Nutrition
1991;54:274S-80S
54. Kolata, G. How important is dietary calcium in preventing
osteoporosis? Science, 1986,233:519-20
55. Mazess RB, Barden HS. Bone density in premenopausal women:
effects of age, dietary intake, physical activity, smoking,
and birth control pills. American Journal of Clinical Nutrition
1991;53:132 42
56. Cortical bone density of adult lacto-ovo vegetarian and
omnivorous women. Journal of the American Dietic Association
1980;76:148-51
57. Henry, Weaver. Calcium absorption from kale American Journal
of Clinical Nutrition 1990;51:656-57
58. Nicar MJ, Pak CYC. Calcium bio-availability from calcium
carbonate and calcium citrate. Journal of Endocrinol Metah 1985;61:391-93
59. A 1-y walking program and increased dietary aid increased
dietary calcium in postmenopausal women: effect on bone. American
Journal of Clinical Nutrition 1991:53:1304 - 11
60. Dietary calcium intake and bone loss from the spine in healthy
postmenopausal women. American Journal of Clinical Nutrition
1987;46:685-87
From the Know About Nutrition Series |
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