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From: brian6 at (Lightbulb joke collector extraordinaire and FAQ maintainer.)
Subject: Calcium (all you ever wanted to know about...)
Date: 4 May 1995 07:57:14 GMT
Organization: Middlesex University, London, England
Lines: 457

by Reed Mangels, Ph.D., R.D.
Summary: Calcium, needed for strong bones.
Green leafy vegetables such as kale are as good as or better than milk as calcium sources. Other good sources include: White/Wholemeal bread, Taco Shells, Oats, Soyabeans, Tofu, Almonds, Brazil Nuts, Pistachios, Sunflower Seeds, Sesame Seeds, Flax Seed, Carob, Carrots, Cabbage, Garlic, Parsley Spirulina, Chives, Seaweed, Cauliflower, Okra, Cassava, Figs, Papaya, Rhubarb, Molasses, tap water...

High protein diets appear to lead to increased calcium losses. Calcium requirements for those on lower protein, plant-based diets are believed to be below the usual recommendations.

The [American] National Research Council itself (which set the RDA values in the first place), acknowledges that people have been able to maintain calcium balance on intakes of as low as 200 - 400 gm/day. They recommended the 800 mg/day because of the excessively HIGH PROTEIN diet of most Americans (see NRC, RECOMMENDED DIETARY ALLOWANCES, 9TH ed., 1980, p. 120-29)
Calcium is a very important mineral in the human body. Our bones contain large amounts of calcium which helps to make them firm and rigid. Calcium is also needed for many other tasks including nerve and muscle function and blood clotting. These other tasks are so important for survival, that, when dietary calcium is too low, calcium will be lost from bone and used for other critical functions. Calcium in the blood is tightly controlled by the body, so calcium status cannot be assessed by measuring blood calcium levels.
Because of heavy promotion by the American dairy industry, the public often believes that cow's milk is the sole source of calcium. However, other excellent sources of calcium exist so that vegans eating varied diets need not be concerned about getting adequate calcium. Table 9 (see below) shows the amount of calcium in selected foods. When you realize that there is as much calcium in 5 ounces of firm tofu or 3/4 cups of collard greens as there is in one cup of cow's milk, it is easy to see why groups of people who do not drink cow's milk still have strong bones and teeth.
How much calcium do we need? The RDA for adults age 25 and older is 800 milligrams of calcium per day (1). An intake of 1200 milligrams of calcium per day is recommended for those age 11-24. In other countries, calcium recommendations are lower than in the US. For example, British adults are advised to have a calcium intake of 500 milligrams per day (2) and adults in Japan are told to have 600 milligrams of calcium daily (3). Does only science influence these recommendations or are political and economic factors also at work? (Read Nutrition Action Health Letter from Center for Science in the Public Interest, Vegetarian Journal, Guide to Healthy Eating from Physician's Committee for Responsible Medicine, Nutrition Week from the Community Nutrition Institute, Advertising Age, and National Dairy Council materials for insight into forces shaping recommendations.)
Calcium requirements may be influenced by high protein intakes (4). High protein diets seem to markedly increase the amount of calcium lost from the body every day (5,6). In fact, when young adults had a protein intake of 48 grams per day (slightly lower than the current RDA) they had no net loss of calcium, even though the amount of calcium in their diet was as low as 500 milligrams daily (7). In contrast, when young adults were on a diet high in protein (112 grams -- typical of many Americans), they lost substantial amounts of calcium in their urine, even when calcium intakes were as high as 1400 milligrams per day (7).
Although phosphorus, another mineral found in foods which are high in protein, does reduce the effects of protein on calcium somewhat, calcium status appears to be more affected by the amount of protein in the diet (5, 6). A protein intake above 70 grams per day is not recommended (6). Of course, this level of protein intake is likely to be exceeded on a meat-based diet or a diet high in dairy products. As Table 10 (see below) shows, by eating 2 servings of meat or fish, an egg, and 2 cups of milk every day, a person would come close to exceeding the 70 gram upper limit for protein without even considering other protein sources such as breads and vegetables.
Table 9: Calcium Content of Selected Vegan Foods
Food                         Amount      Calcium (mg)
Tofu, firm, processed
        with calcium         4 ounces    250-765
Tofu, regular, processed
        with calcium         4 ounces    120-392
Collard greens, cooked       1 cup       357
Rhubarb, cooked              1 cup       348
Spinach, cooked              1 cup       278
Blackstrap molasses          2 TB        274
Turnip greens, cooked        1 cup       249
Tofu, firm, processed
        with nigari*         4 ounces    80-230
Kale, cooked                 1 cup       179
Sesame seeds                 2 TB        176
Okra, cooked                 1 cup       176
Soybeans, cooked             1 cup       175
Beet greens, cooked          1 cup       165
Bok choy, cooked             1 cup       158
Tempeh                       1 cup       154
Mustard greens, cooked       1 cup       150
Figs, dried or fresh         5 medium    135
Tahini                       2 TB        128
Tofu, regular, processed
        with nigari*         4 ounces    80-146
Swiss chard, cooked          1 cup       102
Almonds                      1/4 cup     97
Broccoli, cooked             1 cup       94
Almond butter                2 TB        86
Soymilk, commercial, plain   8 ounces    84
* Read the label on your tofu container to see if it is processed with calcium sulfate or nigari.
The RDA for calcium for adults, 25 and older, is 800 milligrams per day; for those 11-24, the RDA is 1200 milligrams of calcium. United States recommendations are more than 50% higher than the British and Japanese.
Note: Oxalic acid, which is found in spinach, rhubarb, chard, and beet greens is often said to bind with calcium and reduce absorbtion. In laboratory experiments, calcium does combine with oxalates. However, at normal dietary intakes, oxalates have little practical effect on calcium absorbtion (1).
Sources: Composition of Foods. USDA Handbook 8. Manufacturer's information.

The type of protein may also be important. At least one study shows that soy protein, even at high levels, does not increase calcium excretion the same way that protein from animal sources does (5).
The RDAs for calcium were made for people consuming typical American high protein diets. Many vegan diets are lower in protein than these typical American diets. For those whose protein intake is lower, but adequate, or whose protein is from non-animal sources, calcium intakes below the RDA are probably adequate.
We recommend that two or more servings of good sources of dietary calcium be eaten daily by adults, along with the use of a diet without excessive protein. Teenagers and young adults (age 20-25) should eat 3 or more servings of foods high in calcium. Regular weight-bearing exercise such as walking, running, or aerobic dance is also recommended to promote strong, healthy bones.
Vegetarian, and especially vegan, diets are often high in fiber due to frequent use of whole grains, beans, fruits, and vegetables. This may be one reason why vegetarians have a lower incidence of heart disease and some kinds of cancer than does the general public. However, one concern with diets high in fiber is that the fiber can bind with minerals, like calcium, in the intestine and thus keep the minerals from being absorbed. Vegan diets may contain 40 or more grams of fiber per day (8). Dietary fiber intakes of 35 grams or less are not believed to have a significant impact on mineral absorption (9). However, humans may be able to adapt to diets with more than 35 grams of dietary fiber, so that, in time, these diets have little effect on calcium absorption. This adaptation apparently occurs in vegans since bone density of vegans appears to be normal (10). If calcium absorption was impaired, bone density of vegans would be expected to be low.
What about osteoporosis? Don't vegans need extra calcium to prevent osteoporosis? In osteoporosis, bones become porous and fragile. The Dairy Council leads us to believe that milk is essential to prevent osteoporosis. In reality, many other foods besides milk (see Table 9, above) provide calcium, often without the high dose of protein seen in milk.
Other factors which increase the risk of osteoporosis include small frame size, female sex, aging, heredity, cigarette smoking, excessive alcohol, Caucasian or Oriental race, steroid use, early menopause, and prolonged immobilization.
The most promising way that nutrition can reduce the risk of osteoporosis is by promoting development of a favorable peak bone mass during the first 3 to 4 decades of life. Several studies have shown that vegetarians have the same (11, 12) or larger (13) bone masses than do omnivores.
1. Food and Nutrition Board, National Research Council: Recommended Dietary Allowances, 10th ed. Washington, DC: National Academy Press, 1989.
2. Department of Health and Social Security: Recommended Daily Amounts of Food Energy and Nutrients for Groups of People in the United Kingdom. London: HMSO, 1979.
3. Recommended Dietary Allowances for Japan. Tokyo, Japan: Ministry of Health and Welfare, 1984.
4. Food and Nutrition Board, National Research Council: Recommended Dietary Allowances, 9th ed. Washington, DC: National Academy Press, 1980.
5. Zemel MB: Calcium utilization: Effect of varying level and source of dietary protein. Am J Clin Nutr 48: 880-883, 1988.
6. Kerstetter JE and Allen LH: Dietary protein increases urinary calcium. J Nutr 120: 134-136, 1990.
7. Linkswiler HM, Zemel MB, Hegsted M, Schuette S: Protein-induced hypercalciuria. Fed Proc 40: 2429-2433, 1981.
8. Roe LS, Thorogood M, Mann JI: Diet and plasma lipids in a group of vegetarians and omnivores. Proc Nutr Soc 49: 59A, 1990.
9. Kelsay JL: Update on fiber and mineral availability. In Vahouny GW and Kritchevsky D (eds): Dietary Fiber. New York: Plenum Publishing Corporation, 1986; 361-372.
10. Ellis FR et al: Incidence of osteoporosis in vegetarians and omnivores. Am J Clin Nutr 25: 555-558, 1972.
11. Hunt IF, Murphy NJ, Henderson C et al: Bone mineral content in postmenopausal women: comparison of omnivores and vegetarians. Am J Clin Nutr 50: 517-523, 1989.
12. Marsh AG, Sanchez TV, Chaffee FL et al: Bone mineral mass in adult lacto-ovo-vegetarian and omnivorous males. Am J Clin Nutr 37: 453-456, 1983.
13. Marsh AG, Sanchez TV, Mickelsen O et al: Cortical bone density of adult lacto-ovo-vegetarian and omnivorous women. J Am
Diet Assoc 76: 148-151, 1980.
This article was originally published in _Simply Vegan_, published by:
The Vegetarian Resource Group / Vegetarian Journal
P.O. Box 1463
Baltimore, MD 21203
(410) 366-VEGE
For questions or comments on this article, please contact Brad Scott at brad at This article is copied with the permission of the authors. Copyright 1991 by Debra Wasserman and Reed Mangels, Ph.D., R.D.


And here's the Physicians Committee for Responsible Medicine (PCRM) position paper on calcium. Good sources of calcium are included in and at the end of the article.


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 racture 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.


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 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 Tbsp      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

Physicians Committee for Responsible Medicine, P.O. Box 6322, Washington, DC 20015, USA, Telephone: 202 686-2210

************end of article************
  Suzanne Havala, MS, RD
  Johanna Dwyer, DSc, RD
  Phyllis Acosta, RD
  Patricia Johnston, DrPH, RD
  Mary Clifford, RD; Vegetarian Nutrition dietetic practice group
  Winston Craig, PhD, RD
  Virginia Messina, MPH, RD; Pediatric Nutrition dietetic practice group
Reprinted from the Journal of the American Dietetic Association, November 1993, Volume 93, Number 11.
A considerable body of scientific data suggests positive relationships between vegetarian diets and risk reduction for several chronic degenerative diseases and conditions, including obesity, coronary artery disease, hypertension, diabetes mellitus, and some types of cancer.
It is the position of The American Dietetic Association that vegetarian diets are healthful and nutritionally adequate when appropriately planned.
Certain plant constituents appear to inhibit the absorption of dietary calcium, but within the context of the total diet, this effect does not appear to be significant. Calcium from low-oxalate vegetable greens, such as kale, has been shown to be absorbed as well or better than calcium from cow's milk (15). Calcium deficiency in vegetarians is rare, and there is little evidence to show that calcium intakes below the Recommended Dietary Allowance (13) cause major health problems in the vegetarian population. The relatively high US recommendations for calcium intake, compared with those for populations consuming a more plant based diet, are designed to compensate for the calciuric effect of high intakes of animal protein, which are customary in the United States. Studies have shown that vegetarians, on the other hand, absorb and retain more calcium from foods than do nonvegetarians (16,17).
13. Food and Nutrition Board. Recommended Dietary Allowances. 10th ed. Washington, DC: National Academy Press; 1989.

15. Heaney R, Weaver C. Calcium absorption from kale. Am J Clin Nutr. 1990;51:656.

16. Zemel M. Calcium utilization: effect of varying level and source of dietary protein. Am J Clin Nutr. 1988;48:880.

17. Marsh A, Sanchez T, Michelsen O, Chaffee F, Fagal S. Vegetarian lifestyle and bone mineral density. Am J Clin Nutr. 1988;48:837-841.
* ADA Position adopted by the House of Delegates on October 18, 1987, and reaffirmed on September 12, 1992. The update will be in effect until October 1997.