USF-COM Department of Family Medicine

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WHY DO YOU NEED A HIGH CALCIUM DIET?

Calcium has many roles in the body. Calcium is a key player in maintaining strong bones and teeth, and is valuable in helping the heart and muscles function. It is necessary for proper blood clotting. Of all of the calcium in the body, 99% is found in the skeletal system. Therefore, when our bodies do not get enough calcium, it can result in thin, weak, easily fractured bones.
As we grow from infants to adults, we require different amounts of calcium for keeping pace with the metabolism of our bones. This allows our bones to maximize enough bone mass while we grow, which helps maintain bone mass later in life.  As we get older, and we begin to lose more bone than we make, there is an increased risk for osteoporosis, thinning of the bones that increases the risk of fractures. The keys in preventing osteoporosis are to build bone while we are young and to reduce risk factors that lead to loss of bone and subsequent fractures later in life.
In addition to osteoporosis, calcium may play a role in prevention of other bone diseases, colon cancer, hypertension, and preeclampsia, a type of high blood pressure seen in pregnancy.

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HOW MUCH CALCIUM DO YOU NEED?

The amount of calcium you need depends on what stage of life you are in currently:
Table 1.
Birth- 6 months  400 mg/day
6 -12 months  600 mg/day 
1-5 years  800 mg/day
 6-10 years  800-1200 mg/day
11-24 years  1200-1500 mg/day
25-50 years (women)  1000 mg/day 
25-65 years (men)  1000 mg/day
Pregnant/lactating women 1200-1500 mg/day
 > 65 years (men and women)  1500 mg/day
Postmenopausal women: 
                  Taking estrogen 		 1000 mg/day
Postmenopausal women: 
                  Not taking estrogen 		 1500 mg/day 

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HOW DO YOU GET ENOUGH CALCIUM, AND CAN YOU GET TOO MUCH CALCIUM?

There are many sources of calcium in the foods we eat, including dairy products in addition to dairy foods. When unable to get adequate calcium from dietary sources, calcium supplements can be used. Although current studies indicate that calcium levels as high as 2000 mg/day are safe, it is not necessary to take more than the recommended amount for adequate calcium levels. As the amount of calcium intake is increased, the amount absorbed will be decreased. This is the body's way of making sure that it only takes in what it needs. This is also why it is recommended to take calcium supplements in doses no larger than 500 mg at a time. Too much calcium can possibly lead to kidney stones. Too much of certain kinds of calcium can decrease iron absorption, or may interfere with medication absorption. Side effects
such as constipation, stomach bloating and excessive gas can also occur with too much calcium ingestion.
Some people have an intolerance to lactose, a sugar found in dairy products. If this intolerance is not severe, many people can tolerate the low-lactose dairy products, such as yogurt, or milk made lactose deficient. There are many non-dairy high calcium foods to choose from, as well as supplements like Lactaid that aid in the digestion of lactose.

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WHICH FACTORS AFFECT CALCIUM ABSORPTION AND BONE MASS PRODUCTION?

In addition to a high intake of calcium, it is important to realize that there are factors that can increase or decrease the amount of calcium your body can absorb, as well as other factors that may help build or destroy bone.

Vitamin D helps the body absorb calcium in the intestines. Without enough vitamin D in the diet, we would absorb less than 10% of the calcium we consume.

Estrogen deficiency is associated with an increase in bone loss, which seems to be exacerbated by a low calcium diet. A diet high in calcium does not take the place of hormone replacement therapy (HRT); however, in addition to HRT, a diet sufficient in calcium has been shown to help reduce the risks of fractures.

Exercise, especially weight-bearing exercise, stimulates the bones to grow stronger and denser. Immobilization has been associated with increased rate of bone loss and increased risk of fractures.

Diets high in salt, animal protein, alcohol, caffeine, and excess aluminum (seen in antacid abuse)  have been shown to increase the urinary excretion of calcium. Foods high in oxalates (spinach) and phytates (oatmeal) have a small decrease in the availability of the calcium in those foods. Calcium absorption is also decreased by large amounts of wheat bran. There is question that calcium absorption may be affected by tannins in teas, and phosphorus found in colas may take the place of calcium in bones when consumed in excess amounts.

Drugs such as glucocorticoids can decrease calcium absorption.

Smoking is associated with increased rates of osteoporosis.

Eating disorders such as anorexia and bulimia, which are characterized by distorted body image and fear of weight gain leading to decreased food intake or binging and purging, can upset the natural balance of calcium in the blood and bones, and extreme exercise in women athletes can lead to changes in hormone levels that further lead to bone loss.

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WHAT ARE SOME GOOD SOURCES OF CALCIUM?

Table 2.
Food
Amount
Milligrams (mg)
Milk, evaporated skim  1 cup  580
Milk, 1% or skim 1 cup 246
Milk, whole 1 cup 238
Butter milk 1 cup 232
Soy milk, fortified 1 cup 280
Rice milk, fortified 1 cup 280
Yogurt 1 cup 452
Cheese, cheddar 1 cubic inch 129
Cheese, swiss 1 oz 164
Cream cheese 1 oz 202
Cottage cheese 1/2 cup 160
Ice cream, Ice milk 1 cup 272
Collard greens 1 cup 355
Broccolli 1 cup 178
Sweet potatoes 1 cup 50-100
Green beans 1 cup 50-100
Spinach, steamed 1 cup 245
Almonds 2 oz 132
Tofu 4 oz 260
Tortilla, corn 1 120
Kidney beans 1 cup 115
Black beans 1 cup 105
Lentils, cooked 1 cup 50-100
Chick peas, cooked 1 cup 50-100
Navy beans, cooked 1 cup 50-100
Pinto beans, cooked  1 cup 50-100
Sardines with bones 3 oz 372
Shrimp, Clams, Crab 1  cup 50-100
Orange 1 50-100
Orange juice, calcium fortified 1  cup 333

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CALCIUM SUPPLEMENTS

Although there are many calcium supplements, there are some differences to take into consideration when choosing the right supplement for you. It is important to know how much elemental calcium is contained in a tablet. This is the calcium that will actually be absorbed. The supplements come as calcium salts, such as carbonate or citrate, which usually make up at least half of the weight of the tablet. For example, a Tums 500 mg tab contains 200 mg calcium and 300 mg carbonate. Calcium carbonate, which is the most common preparation, has the greatest amount of calcium by weight (40%), while calcium citrate has 21% calcium by weight. Absorption is another factor, as citrate is slightly better absorbed than carbonate. Most forms of calcium are best absorbed when taken in small doses of no more than 500 mg elemental calcium at a time between meals. Carbonate preparations, however, are best absorbed with meals, because of the increase in gastric acid. Also of concern is the possible presence of lead and other contaminants in the preparations; however, most commercial preparations are tested for contamination by heavy metals. Cost of a one month supply of calcium supplements (1000 mg/day) can range from $1.20 to $60.00, without a clear benefit from the more expensive preparations.
Table 3. Calcium Supplements.
Calcium Salt 
Trade Name
Dosage (mg) 
Calcium/ tab (mg)
Cost/ 500mg Ca (cents)
Carbonate  Tums 500 200 7
 Tums-EX 750 300 7
Alka-Mints 850 340 5
Os-Cal 500 1250 500 11
Caltrate 600 1500 600 9
Generic  650 200 3-18
Citrate Citracal 950  200 17
Lactate Generic 350 42  18-27
Gluconate Generic 500 45 43-83
Generic 975  88  15-51
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