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Woodstock Animal Rights Movement
A Store For Life
P. O. Box 746
Woodstock, NY 12498 USA |
Calcium in the Vegan Diet
by Reed Mangels, Ph.D., R.D.
From the Vegetarian Resource Group
Summary
Calcium, needed for strong
bones, is found in dark green leafy vegetables, tofu made with calcium
sulfate, calcium-fortified soy milk and orange juice, and many other
foods commonly eaten by vegans. Although lower animal protein intake may
reduce calcium losses, there is currently not enough evidence to suggest
that vegans have lower calcium needs. Vegans should eat foods that are
high in calcium and/or use a calcium supplement.
The
Need for Calcium
Calcium is a very important mineral for humans. 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. The body tightly controls calcium in the
blood, so measuring blood calcium levels cannot assess calcium status.
Tofu and Other Sources
of Calcium
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 that contain these foods need not be concerned about getting
adequate calcium.
Sources of well-absorbed calcium for vegans include
calcium-fortified soy milk and juice, calcium-set tofu, soybeans and
soynuts, bok choy, broccoli, collards, Chinese cabbage, kale, mustard
greens, and okra 1. Grains, beans (other than soybeans),
fruits, and vegetables (other than those listed) can contribute to
calcium intake but cannot replace these key foods.
Table 1 shows the amount of calcium in selected foods.
When you realize that there is as much or more calcium in 4 ounces of
firm tofu or 3/4 cup 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 recommended level of calcium for adults age 19 through 50 years is
1000 mg per day2. An intake of 1200 mg of calcium is
recommended for those age 51 years and older 2. Some studies
3-5, although not all 3-5, have shown that older adults with a high
calcium intake have stronger bones and a lower fracture risk. There are
a limited number of studies of vegans, most of which find low bone
density as well as low calcium intakes 7,8. One study 9 where
vegans had calcium intakes close to recommended levels found that
calcium was well absorbed from a vegan diet.
Our Vegan Food Guide (page
198 of Simply Vegan) indicates good sources of calcium from several
food groups. By choosing the suggested number of servings of
calcium-rich foods daily, vegans should meet calcium needs. Table 2
shows several menus that contain more than 1000 mg of calcium.
Tofu is commonly recommended as a good source of calcium. Actually,
the amount of calcium in tofu depends on the coagulating agent used to
precipitate the soy protein in the process of making tofu. Calcium
sulfate and nigari (magnesium chloride) are two commonly used agents.
The agent used will be listed on the label under ingredients. Tofu that
is prepared with calcium sulfate will contain more calcium than tofu
made with nigari.
The amount of calcium in tofu varies from brand to brand. To
calculate how much calcium is in the tofu you buy, look at the label.
Calcium content will be listed as percent of the Daily Value. Since the
current Daily Value for calcium is 1000 mg, multiply the percent Daily
Value by 10 to get the amount of calcium (in milligrams) in one serving.
For example, tofu with 10% Daily Value for calcium would have 100 mg of
calcium in one serving.
The Influence of
Excessive Protein
The area of protein's effect on bones remains uncertain. Some studies
show that diets that are high in protein, especially animal protein, do
cause increased losses of calcium in the urine 10 and may
even in-crease fracture risk 11,12. These effects of protein
may be especially important in those with low calcium intakes 13.
Other studies suggest that a higher protein intake is needed to promote
calcium absorption 14, reduce the risk of fracture 15, and
increase bone density 16,17. Until further evidence is
available, vegans should strive to meet calcium recommendations and to
have adequate, but not excessive, amounts of protein.
Other factors in bone health include sodium and physical activity.
Sodium increases calcium losses with 5 to 10 mg of calcium lost with
each gram of salt eaten 18. Reducing sodium intake can reduce
calcium losses. Regular weight-bearing exercise such as walking,
running, or aerobic dance is recommended to promote strong, healthy
bones. Besides helping strengthen bones, exercise can also improve
balance and flexibility, both important factors in preventing and
recuperating from falls.
Table
1: Calcium Content of Selected Vegan Foods |
Food |
Amount |
Calcium (mg) |
Tofu, processed with
calcium sulfate* |
4 ounces |
420 |
Blackstrap molasses |
2 Tbsp |
400 |
Collard greens, cooked |
1 cup |
357 |
Calcium-fortified orange juice |
8 ounces |
300 |
Soy or ricemilk, commercial,
calcium-fortified, plain |
8 ounces |
200-300 |
Commercial soy yogurt, plain |
6 ounces |
80-250 |
Turnip greens, cooked |
1 cup |
249 |
Tofu, processed with nigari* |
4 ounces |
80-230 |
Tempeh |
1 cup |
215 |
Kale, cooked |
1 cup |
179 |
Soybeans, cooked |
1 cup |
175 |
Okra, cooked |
1 cup |
172 |
Bok choy, cooked |
1 cup |
158 |
Mustard greens, cooked |
1 cup |
152 |
Tahini |
2 Tbsp |
128 |
Broccoli, cooked |
1 cup |
94 |
Almonds |
1/4 cup |
89 |
Almond butter |
2 Tbsp |
86 |
Soy milk, commercial, plain |
8 ounces |
80 |
*Read the label on your tofu container to
see if it is processed with calcium sulfate or nigari.
Note: Oxalic acid, which is
found in spinach, rhubarb, chard, and beet greens binds with the
calcium in those foods and reduces its absorption. These foods
should not be considered good sources of calcium. Calcium in
other green vegetables, like kale, collard greens, Chinese
mustard greens, and Chinese cabbage flower leaves is well
absorbed1,19. Fiber appears to have little effect on calcium
absorption except for the fiber in wheat bran that does have a
small effect20.
Sources: Composition of
Foods. USDA Nutrient Data Base for Standard Reference, Release
18, 2005 and Manufacturer's information. |
Table 2: Sample Menus Providing More Than 1000 milligrams of
Calcium
|
Calcium (mg) |
Breakfast: |
|
1 serving Cindy's Light
and Fluffy Pancakes (p. 23) |
195 |
1 cup Calcium-Fortified Soy milk |
300 |
Lunch: |
|
1 serving Hummus on Pita Bread (p. 27) |
178 |
6 Dried Figs |
68 |
1/4 cup Almonds |
89 |
Dinner: |
|
1 serving Scrambled Tofu and
Bok Choy over Brown Rice (p. 96) |
190 |
1 serving Green Salad and
Tangerine Dressing (p. 39) |
30 |
1 serving Chocolate Pudding (p. 114) |
92 |
TOTAL |
1142 |
|
Breakfast: |
|
1 serving Tropical Fruit Smoothie (p. 16) |
102 |
1 Toasted Bagel with |
89 |
2 Tbsp Almond Butter |
86 |
Lunch: |
|
1 serving Mini Pizzas (p. 34) |
235 |
1 serving Creamed Spinach (p. 68) |
121 |
Dinner: |
|
1 serving Lemon Rice Soup (p. 46) |
82 |
1 serving Tofu Squash Burgers (p. 102) |
135 |
1 cup Steamed Broccoli |
94 |
1 serving Chocolate Pudding (p. 114) |
92 |
TOTAL |
1036 |
Page numbers refer to recipes in the book Simply Vegan: Quick
Vegetarian Meals.
Additional foods should be added to these menus to provide
adequate calories and to meet requirements for nutrients besides
calcium. |
There are factors that increase the risk of osteoporosis and that
cannot be changed. These include small frame size, female gender, aging,
heredity, Caucasian or Oriental race, early menopause, and prolonged
immobilization. Other factors like cigarette smoking, excessive alcohol,
physical inactivity, and inadequate calcium and vitamin D (see Simply
Vegan Chapter on Vitamin D) are under our control.
Vegans of all ages
can promote bone health by consuming enough calcium and protein, getting
adequate vitamin D, limiting use of sodium, and getting regular
exercise, especially weight-bearing exercise.
References
- Weaver CM, Plawecki KL. Dietary calcium: adequacy of
a vegetarian diet. Am J Clin Nutr 1994;59 (suppl):1238S-1241S.
- Standing Committee on the Scientific Evaluation of
Dietary Reference Intakes, Food and Nutrition Board, Institute
of Medicine: Dietary Reference Intakes for Calcium,
Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington,
DC: National Academy Press, 1997.
- Chevalley T, Rizzoli R, Nydegger V, et al. Effects
of calcium supplements on femoral bone mineral density and
vertebral fracture rate in vitamin-D-replete elderly patients.
Osteoporos Int 1994;4:245-52.
- Dawson-Hughes B, Harris SS, Krall EA, Dallal GE.
Effect of calcium and vitamin D supplementation on bone density
in men and women 65 years of age or older. N Engl J Med
1997;337:670-6.
- Recker R, Hinders S, Davies KM, et al. Correcting
calcium nutritional deficiency prevents spine fractures in
elderly women. J Bone Miner Res 1996;11:1961-6.
- Feskanich D, Willett WC, Colditz GA. Calcium,
vitamin D, milk consumption, and hip fractures: a prospective
study among postmenopausal women. Am J Clin Nutr
2003;77:504-11
- Marsh AG, Sanchez TV, Michelsen O. Vegetarian
lifestyle and bone mineral density. Am J Clin Nutr
1988;48(suppl):837-41.
- Chiu JF, Lan SJ, Yang CY, et al. Long-term
vegetarian diet and bone mineral density in post-menopausal
Taiwanese women. Calcif Tissue Int 1997;60:245-9.
- Kohlenberg-Mueller K, Raschka L. Calcium balance in
young adults on a vegan and lactovegetarian diet. J Bone
Miner Metab 2003;21:28-33.
- Kerstetter JE, O'Brien KO, Insogna KL. Low protein
intake: the impact on calcium and bone homeostasis in humans.
J Nutr 2003;133:855S-61S.
- Frassetto LA, Todd KM, Morris RC, Jr., et al.
Worldwide incidence of hip fracture in elderly women: relation
to consumption of animal and vegetable foods. J Gerontol A
Biol Sci Med Sci 2000;55:M585-92.
- Sellmeyer DE, Stone KL, Sebastian A, et al. A high
ratio of dietary animal to vegetable protein increases the rate
of bone loss and the risk of fracture in postmenopausal women. Am
J Clin Nutr 2001;73:118-22.
- Meyer HE, Pedersen JI, Loken EB, et al. Dietary
factors and the incidence of hip fracture in middle-aged
Norwegians. A prospective study. Am J Epidemiol
1997;145:117-23.
- Kerstetter JE, O'Brien KO, Caseria DM, et al. The
impact of dietary protein on calcium absorption and kinetic
measures of bone turnover in women. J Clin Endocrinol Metab
2005;90:26-31.
- Munger RG, Cerhan JR, Chiu BC. Prospective study of
dietary protein intake and risk of hip fracture in
postmenopausal women. Am J Clin Nutr 1999;69:147-52.
- Kerstetter JE, Looker AC, Insogna KL. Low dietary
protein and low bone density. Calcif Tissue Int
2000;66:313.
- Promislow JH, Goodman-Gruen D, Slymen DJ, et al.
Protein consumption and bone mineral density in the elderly: the
Rancho Bernardo Study. Am J Epidemiol 2002;155:636-44.
- Heaney RP. Calcium: How your diet affects
requirements. Veg Nutr and Health Letter Feb
1998;1(3):1-2.
- Weaver CM, Heaney RP, Nickel KP, et al. Calcium
bioavailability from high oxalate vegetables: Chinese
vegetables, sweet potatoes, and rhubarb. J Food Sci
1997;62:524-525.
- Weaver CM, Heaney RP, Martin BR, et al. Human
calcium absorption from whole-wheat products. J Nutr
1991;121:1769-1775.
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