DrWells.net : Nutrition : Single Nutrients

Special Features
Single Nutrients
- from A to Zinc
Recipes
Drug/Nutrient
Interactions

Everyone Needs to Know
About the Food Pyramid
About whole foods
Do I need supplements?
Good and bad fats
Drinking enough water?
What about fiber?
Sugars and artificial sweeteners
How much alchohol
Sugar content of
popular foods

Nutritional Approaches
Overweight
Cardiovascular
Diabetes
Menopause
Hypothyroidism

Calcium

Back to Nutrient List

Proper name	Calcium
Category	Mineral
Functions	99% of calcium is bound in teeth and bone as hydroxyapatite, a calcium carbonate/calcium phosphate compound that provides structural support to bones. The remaining 1% exists as ionic calcium and serum calcium. Calcium ions are required for cross Đlinking threads of fibrin, allowing blood to clot. Calcium ions are necessary for transmitting impulses from one nerve cell to another. Calcium ions are required for muscle cells to contract and relax. This is critical to heart function. Calcium ions control the permeability of cell walls to fluids and solutes. Calcium supplementation has been shown to reduce high blood pressure slightly. Calcium deficiency is associated with increased rates of colorectal cancer. Calcium supplementation in high risk individuals reduced the rate of abnormal cell division in the colon.
RDA	Age 11-24, or during pregnancy and lactation, 1,200 mg per day. Children from age 1 to 10 and adults age 25 and up, 800 mg per day. Infants from 0 to 6 months, 600 mg per day. Infants from 6 months to 1 year of age, 800 mg per day.
Therapeutic dose	1,200 mg per day
Deficiency symptoms	Tetany (severe, intermittent muscular contractions and pain cause by deficient ionized serum calcium). Osteoporosis. Thinning of the bone occurs most rapidly in the first 5 years after menopause. During this time, calcium may be lost at a rate of 40 to 120 mg per day. After that, bone density commonly decreases by about 1% per year. Rickets and osteomalacia are disorders of bone formation that result from deficiency of calcium and vitamin D. Tooth decay, back and leg pains, muscle cramps, insomnia and nervous disorders may also be a result of calcium deficiency.
Toxicity	The body excretes large doses of calcium efficiently. The only adverse effects of excessive calcium intake are interference with magnesium, iron and zinc.
Best forms	Microcrystalline hydroxyapetite, Calcium citrate or citrate-malate (though citrate increases absorption of dietary aluminum)
Food sources	Dairy products are the most common dietary source of calcium. However, dairy products are the most common cause of food allergies. Persons of Asian or African descent are commonly allergic to lactose (milk sugar). Lactose intolerance often causes diarrhea and other forms of gastrointestinal distress. Allergy to dairy protein (casein) may result in more subtle, long-term illness. As an example, children with juvenile onset diabetes are seven times more likely to be allergic to casein, indicating a possible allergic trigger to the disease. Dairy products also contain an enzyme called xanthine oxidase, which is implicated in the formation of atherosclerosis. Of all the dairy products available, yogurt is the best tolerated as both the sugar and protein in the milk have been partially digested by bacterial fermentation. Other sources of calcium include collard greens, figs, almonds, white meat of chicken, baked potato and soy products. Many foods, including milk substitutes are fortified with calcium.
Lab tests	Serum calcium. Serum ionized calcium. Urinary calcium.
Drug interactions	The following drugs deplete calcium: Aluminum compounds such as aluminum hydroxide, Barbiturates, Bumetanide, Chlortetracycline, Choestyramine Resin, Cimetidine, Corticosteroids, Demeclocycline, Ethacrynic Acid, Ethosuximide, Famotidine, Fosphenytoin, Furosemide, Hydrochlorothiazide, Magnesium compounds, Methsuximide, Mineral Oil, Minocycline, Nizaidine, Oxytetracycline, Phenytoin, Primidone, Ranitidine Bismuth Citrate and Ranitidine hydrochloride, tetracycline, Torsemide, Triamterene.
Nutrient interactions	High protein diets increase calcium absorption but also increase excretion in the urine, leading to a net loss of calcium. Excess fat in the diet or poor function of the gallbladder may result in fat binding with calcium in the intestines to form insoluble soaps. Phytic acid (in wheat and other whole grains) or oxalic acid (in spinach and other leafy greens) may bind with calcium, decreasing absorption. Excessive calcium intake may depress levels of zinc, iron and magnesium. Treatment or prevention of osteoporosis is best accomplished with a combination of calcium, vitamin D and boron. Excessive phosphorus will leach calcium from the bones and teeth. Phosphorus is found in soft drinks and animal protein. Caffeine mobilizes calcium and increases excretion.
Metabolism	Only 10% to 30% of dietary calcium is absorbed. Gastric hydrochloric acid is needed to absorption, which occurs primarily in the first part of the small intestine, the duodenum. Persons with lowered levels of hydrochloric acid, such as the elderly, have reduced calcium absorption. The vitamin D hormone (calcitriol) increases calcium absorption by stimulating production of a calcium-binding protein carrier in the duodenum. This carrier protein transports calcium through the intestinal wall, into the blood stream. Calcium absorption increases in persons who are deficient in calcium. The average amount of calcium in a150 pound person is 3 pounds. Approximately 99% of all calcium in the body is used to form bones and teeth. The remaining 1% serves a number of important functions including; blood clotting, nerve transmission, muscle contraction and relaxation, cell membrane permeability and enzyme activation. Calcium balance is regulated by parathyroid hormone (parathormone), calcitriol and calcitonin. The parathyroid glands measure the level of circulating ionized calcium. When the level is low, parathormone is released. This hormone stimulates the intestinal mucosa to absorb more calcium, withdraws more calcium from the bones and stimulates the kidneys to excrete more phosphate (to restore calcium Đ phosphate balance). Calcitriol also promotes intestinal absorption of calcium and acts to deposit calcium in the bones. Calcitonin (produced by C cells in the thyroid) prevents abnormal elevation in serum calcium by controlling the release of calcium from the bone. It counterbalances the effects of parathormone.