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:Calcium:
:Calcium is the most abundant
mineral in the human body. Of 2 or 3 pounds of calcium in the body,
99% forms bones and teeth. Calcium is essential for blood clotting,
transmission of nerve signals, and muscle contraction.
Calcium plays a minor role in lowering blood pressure. 1 The level
of calcium in the blood is regulated by parathyroid hormone (PTH),
and low intake of calcium causes elevations in PTH, which in turn
can cause hypertension. 2 High calcium intake reduces risk of cardiovascular
disease in postmenopausal women. 3
By reducing absorption of oxalate, 4 calcium may reduce risk of kidney
stones. 5 People with a history of kidney stones should talk with
their health practitioner before supplementing calcium as it may increase
risk of stones for a few people who absorb too much calcium.
Calcium partially binds some fats and cholesterol in the gastrointestinal
tract. Some research finds that calcium supplements may lower cholesterol.
6
Animal studies shows calcium helps develop female egg cells (oocytes).
7 8 Some researchers speculate that calcium could help polycystic
ovary syndrome (PCOS). 9
Calcium may have anticancer activity in the colon. Most studies show
high calcium diets reduce colon cancer risk. 10 Most 11 12 13 but
not all 14 studies find calcium supplements reduce risk of colon cancer
or precancer. One study reports that high dietary, but not supplemental,
calcium intake decreases risk of precancerous changes in the colon.
15 In double-blind studies, calcium supplementation protects against
precancerous changes in the colon in some 16 17 but not all studies.
18 19
Sources: Most dietary calcium comes from dairy products
. The myth that calcium from dairy products is not absorbed is not
supported by scientific research. 20 21 Other sources include sardines,
canned salmon, green leafy vegetables and tofu.
Choosing a form of calcium supplement can be confusing. While fewer
pills of the calcium carbonate form are needed, some people may not
absorb this form of calcium as well as some other forms. Most, 22
23 but not all, 24 studies suggest that calcium citrate is better
absorbed than calcium carbonate. Virtually all comparative studies
find that calcium citrate/malate (CCM) is absorbed better than calcium
carbonate. CCM is increasingly the form of calcium recommended by
doctors. Microcrystalline hydroxyapatite (MCHC),
a variation on the bone meal form of calcium, has been shown to improve
bone mass, 25 even though the absorption of MCHC is fairly
low 26 27 perhaps because MCHC doubles absorption of dietary calcium
by stimulating active uptake in the small intestine. Only preliminary
research exists on amino acid chelates of calcium.
Documented uses:
Science supported uses:
Traditional clinical uses:
-
Amenorrhea
(calcium for preventing bone loss)
-
Colon cancer
(reduces risk)
-
Depression
-
Dysmenorrhea
(painful menstruation)
-
Gingivitis
(periodontal disease)
-
Insulin resistance
syndrome (Syndrome X)
-
Kidney stones
-
Migraine headaches
-
Multiple sclerosis
-
Pregnancy and
postpartum support
Warning: Calcium
supplements should be avoided by prostate cancer patients.
Deficiency: Severe deficiency of either calcium or
vitamin D leads to a condition called rickets in children and osteomalacia
in adults. Since vitamin D is required for calcium absorption, people
with conditions causing vitamin D deficiency (e.g., pancreatic insufficiency)
may develop a deficiency of calcium as well. Vegans (pure vegetarians
), people with dark skin, those who live in northern climates, and
people who stay indoors almost all the time are more likely to be
vitamin D deficient, than are other people. Vegans often eat less
calcium and vitamin D than do other people. Most people eat well below
the recommended amount of calcium. This lack of dietary calcium is
thought to contribute to the risk of osteoporosis , particularly in
white and Asian women.
| Calcium or Vitamin D deficiency |
Calcium excess |
| Bone fractures |
Calcification of soft tissues |
| Rickets |
Muscle spasms |
| Osteomalacia |
|
Dosage: The National
Academy of Sciences has established guidelines for calcium that are
25–50% higher than previous recommendations. For ages 19 to
50, calcium intake is recommended to be 1,000 mg daily; for adults
over age 51, the recommendation is 1,200 mg daily. 28 The most common
supplemental amount for adults is 800–1,000 mg per day. 29 General
recommendations for higher daily intakes (1,200–1,500 mg) usually
include the calcium most people consume from their diets. Studies
indicate the average daily amount of calcium consumed by Americans
is about 500–1,000 mg.
Are there any side effects or interactions? Constipation , bloating,
and gas are sometimes reported with the use of calcium supplements.
30 A very high intake of calcium from dairy products plus supplemental
calcium carbonate was reported in the past to cause a condition called
“milk alkali syndrome.” This toxicity is rarely reported
today because most medical doctors no longer tell people with ulcers
to use this approach as treatment for their condition.
People with hyperparathyroidism, chronic kidney disease, or kidney
stones should not supplement with calcium without consulting a physician.
For other adults, the highest amount typically suggested by doctors
(1,200 mg per day) is considered quite safe.
In the past, calcium supplements in the forms of bone meal (including
MCHC), dolomite, and oyster shell have sometimes had higher lead levels
than permitted by stringent California regulations, though generally
less than the levels set by the federal government. 31 “Refined”
forms (which would include CCM, calcium citrate, and most calcium
carbonate) have low levels. 32 More recently, a survey of over-the-counter
calcium supplements found low or undetectable levels of lead in most
products, 33 representing a sharp decline in lead content of calcium
supplements since 1993. People who decide to take bone meal, dolomite,
or oyster shell calcium for long periods of time can contact the supplying
supplement company to request independent laboratory analysis showing
minimal lead levels.
Calcium competes for absorption with a number of other minerals. Therefore,
people taking calcium for more than a few weeks should also take a
multimineral supplement.
Vitamin D’s most important role is maintaining blood levels
of calcium. Therefore, many doctors recommend that those supplementing
with calcium also supplement with 400 IU of vitamin D per day.
Animal studies have shown that essential fatty acids (EFAs) increase
calcium absorption from the gut, in part by enhancing the effects
of vitamin D and reducing loss of calcium in the urine. 34
Lysine supplementation increases the absorption of calcium and may
reduce its excretion. 35 As a result, some researchers believe that
lysine may eventually be shown to have a role in the prevention and
treatment of osteoporosis. 36
Medication interactions:
Albuterol (Depletion or interference)
Alendronate: Calcium supplements may interfere with absorption, but
one researcher suggests that large doses of calcium in bone metastases
(with evidence of osteomalacia) related to prostate cancer may improve
clinical outcome. Calcium and alendronate are commonly used simultaneously
for osteoporosis. Take alendronate two hours before or after calcium.
Aluminum Hydroxide (Depletion or interference)
Anticonvulsants (Depletion or interference)
Bile Acid Sequestrants (Depletion or interference)
Caffeine (Depletion or interference)
Calcitonin (Supportive interaction)
Calcium Acetate (Adverse interaction)
Ciprofloxacin (Reduced drug absorption/bioavailability)
Cisplatin (Depletion or interference)
Colestipol (Depletion or interference)
Inhaled Corticosteroids (Depletion or interference)
Oral Corticosteroids (Depletion or interference)
Cycloserine (Depletion or interference)
Diclofenac (Depletion or interference)
Doxycycline (Reduced drug absorption/bioavailability)
Erythromycin may interfere with absorption and/or activity of calcium.
If taking erythromycin longer than two weeks, supplement with a multivitamin-mineral.
Estrogens (Combined) (Supportive interaction)
Felodipine (Depletion or interference)
Flurbiprofen (Depletion or interference)
Gabapentin (Depletion or interference)
Gentamicin (Depletion or interference)
Hydroxychloroquine (Depletion or interference)
Indapamide (Depletion or interference)
Indomethacin (Depletion or interference)
Isoniazid (Depletion or interference)
Lactase: Lactase-deficient people may not consume dairy products as
a source of calcium. Lactase allows lactase-deficient people to digest
milk sugar. The calcium requirement is reduced by about half where
dairy is not eaten.
Metformin (Side effect reduction/prevention)
Mineral Oil (Depletion or interference)
Minocycline (Depletion or interference)
Nadolol (Reduced drug absorption/bioavailability)
Neomycin (Depletion or interference)
Ofloxacin (Reduced drug absorption/bioavailability)
Oral Contraceptives may increase absorption of calcium
Phenobarbital (Depletion or interference)
Risedronate (Depletion or interference)
Rofecoxib (Reduced drug absorption/bioavailability)
Sodium Fluoride: calcium from leg bones may transfer to the spine
causing stress fractures when fluoride is taken. Supplementing with
1,500 mg of calcium each day together with slow-release forms of fluoride
increases the bone density of the lumbar spine without causing fractures.
People taking sodium fluoride to treat osteoporosis should supplement
with calcium. Taking fluoride and calcium at the same time reduces
absorption of fluoride, so they should be taken at least an hour apart.
Sotalol (Reduced drug absorption/bioavailability)
Sucralfate (Depletion or interference)
Sulfamethoxazole (Depletion or interference)
Tetracycline (Reduced drug absorption/bioavailability)
Tetracyclines (Reduced drug absorption/bioavailability)
Thiazide Diuretics decrease calcium loss in the urine.
Thyroid Hormones (Depletion or interference)
Tobramycin (Depletion or interference)
Triamterene (Depletion or interference)
Trimethoprim (Depletion or interference)
Valproic Acid (Depletion or interference)
Verapamil (Adverse interaction)
References:
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RB, Dudek J, et al. Evidence for the relationship of calcium to
blood pressure. Nutr Rev 1996;54:365–81.
2. Jorde R, Sundsfjord J, Haug E, Bønaa KH. Relation between
low calcium intake, parathyroid hormone, and blood pressure. Hypertension
2000;35:1154–9.
3. Bostick RM, Kushi LH, Wu Y, et al. Relation of calcium, vitamin
D, and dairy food intake to ischemic heart disease mortality among
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following oral oxalate loads in patients with ileal disease and
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