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Other common
name(s): calcium carbonate, calcium gluconate, calcium
citrate
Scientific/medical
name(s): Ca, Ca++
Description
Calcium is a mineral that is vital for a number of bodily
functions, such as contraction of muscles (including the heart),
secretion of hormones, and sending messages through the nervous system.
Most of the body's calcium is in the bones and teeth, but some of it
circulates in the blood for these important tasks. Calcium is found
naturally in many dairy products, leafy green vegetables, and fish.
Because humans cannot make calcium, it must be obtained from foods or
supplements.
Overview
Many people, especially women, can benefit from keeping up
with their calcium intake to help prevent bone problems such as
osteoporosis. Calcium supplements will not slow the growth of most
cancers, although they appear to reduce the risk of precancerous polyps
of the colon. Calcium supplements may be important for some people with
cancer, depending on their specific cancer type and stage and the type
of treatments received.
How is it promoted for use?
Calcium is best known for its role in growing and maintaining
the bones and teeth. It also helps the heart and other muscles do their
work. There is strong evidence that low calcium intake can lead to
fragile bones, high blood pressure, and certain types of cancer. Recent
studies have shown that calcium may reduce the risk of colon cancer and
perhaps some other types of cancer. When combined with vitamin D,
calcium may have the potential to help prevent cancers of the breast
and pancreas. Calcium has also been found helpful in reducing certain
symptoms of premenstrual syndrome. There is some early evidence that
calcium may play a role in helping to prevent heart disease and
reducing insulin resistance in diabetic patients.
Because calcium plays a crucial role in building and
maintaining bone mass and strength, its greatest benefit to people with
cancer may be to reduce the risk of osteopenia (reduced bone mass) and
osteoporosis, a condition that results in fragile bones and a severe
loss of bone mass and strength. Both conditions are linked mainly with
aging, and osteoporosis is a common problem for women after menopause.
Osteopenia and osteoporosis can also result from poor nutrition,
prolonged drug therapy, disease, and poor mobility, all of which may
apply to people who have cancer.
What does it involve?
The body's use of calcium is complex. It is affected by many
hormones and factors other than how much calcium a person eats or takes
in. There are many ways to treat bone problems and calcium imbalance in
the body, depending on their cause.
The best source of calcium is a balanced diet, which helps to
avoid bone problems and decreases the risk of some types of cancer.
Foods and beverages high in calcium include milk and other dairy
products (low-fat products are healthier), leafy green vegetables such
as broccoli and greens, nuts, seeds, beans, tofu prepared with calcium,
cheese, dried figs, kelp, oysters, and canned fish that can be eaten
with the bones still in it, such as sardines and salmon. Certain brands
of cereals, orange juices, and soy milks are fortified with calcium and
are clearly marked as such on the label.
Although calcium intake from healthy foods is the best source,
calcium supplements are also available in drug stores, grocery stores,
and many health food stores. The Recommended Dietary Allowance (RDA)
for calcium is 1,000 milligrams per day for men and women between 19
and 50, and 1,200 milligrams per day for people over 50. Some
nutritionists and doctors recommend that calcium supplements be taken
with supplements of vitamin D and other important minerals, such as
magnesium and potassium.
What is the history behind it?
The importance of calcium for maintaining overall health and
promoting bone strength has been known for decades. Some scientists
believe that humans became accustomed to diets high in calcium as far
back as 35,000 years ago. Calcium's role in preventing or slowing the
growth of cancer has only become a notable subject of research within
the last 15 to 20 years.
What is the evidence?
A number of important studies to measure calcium's impact on
cancer have been published in peer-reviewed medical journals. Several
studies have suggested that foods high in calcium might help reduce the
risk for colorectal cancer. These studies also suggest that calcium
supplements may somewhat reduce the risk of adenomas, which are a type
of polyps in the colon and rectum that can progress to cancer. More
recent studies have noted that women with higher dietary calcium intake
seemed to have lower risk of breast cancer. This risk was not affected
by calcium supplements.
One researcher reviewed several dozen studies of the effects
of calcium on various diseases and concluded that long-term
deficiencies in calcium and vitamin D may lead not only to fragile
bones, but also to colorectal cancer and high blood pressure in some
people. Adequate calcium intake may help to prevent these conditions in
some. A randomized clinical trial reported in 2007 found lower risk for
all cancers combined in women given calcium supplements than in women
taking the placebo. Cancer risk was even lower among women taking both
calcium and vitamin D.
While further research is needed to clarify the role of
calcium in preventing or reversing cancer growth, there is little doubt
that adequate calcium intake is required for preventing bone shrinkage
and weakening. For people who have cancer, calcium and vitamin D intake
may help keep bones strong.
Some chemotherapy medications can reduce appetite, create
swallowing difficulties, cause nausea and vomiting, and result in
osteopenia. The chemotherapy drugs methotrexate and doxorubicin may
directly damage bones. Some hormonal therapies used in the treatment of
breast or prostate cancer can also weaken bones. Radiation therapy can
cause osteopenia within the area being treated, and the combination of
radiation therapy and chemotherapy can cause even greater damage to
bone structure. Some cancers also can harm bones. Although adequate
calcium intake is important for bone health in the general public and
in cancer survivors, and especially those with osteoporosis, calcium
intake is not the only factor that determines bone health. Physical
activity is also important in keeping bones strong. In addition, there
are several kinds of medications available for treatment of
osteoporosis.
Are there any possible problems or
complications?
This product is sold as a
dietary supplement in the United States. Unlike companies that produce
drugs (which must provide the FDA with results of detailed testing
showing their product is safe and effective before the drug is approved
for sale), the companies that make supplements do not have to show
evidence of safety or health benefits to the FDA before selling their
products. Supplement products without any reliable scientific evidence
of health benefits may still be sold as long as the companies selling
them do not claim the supplements can prevent, treat, or cure any
specific disease. Some such products may not contain the amount of the
herb or substance that is written on the label, and some may include
other substances (contaminants). Though the FDA has written new rules
to improve the quality of manufacturing processes for dietary
supplements and the accurate listing of supplement ingredients, these
rules do not take full effect until 2010. And, the new rules do not
address the safety of supplement ingredients or their effects on health
when proper manufacturing techniques are used.
Most such
supplements have not been tested to find out if they interact with
medicines, foods, or other herbs and supplements. Even though some
reports of interactions and harmful effects may be published, full
studies of interactions and effects are not often available. Because of
these limitations, any information on ill effects and interactions
below should be considered incomplete.
The greatest risk with calcium comes from not getting enough
of it. In rare cases, taking in very high levels of calcium (usually
more than 2,400 milligrams a day) can lead to high levels of calcium in
the blood, a condition called hypercalcemia. Hypercalcemia can cause
kidney stones, muscle pain, and mental confusion and is considered a
serious medical condition. It is also possible to get high calcium
levels from taking in too much vitamin D, such as from supplement
overuse. However, most cases of high calcium levels are caused by the
cancer itself, especially in its later stages.
Calcium can keep other minerals such as iron, zinc, magnesium,
and phosphorus from being absorbed. Calcium can also interfere with the
absorption of several types of medicine, so it is helpful to talk with
your doctor or pharmacist about all medicines and supplements that you
are taking.
There is some evidence that a high calcium intake, mainly
through supplements, is linked with increased risk for prostate cancer,
especially for prostate cancers that are more aggressive. Both men and
women should try to take in recommended levels of calcium, mainly
through food sources. Dairy products are excellent sources of calcium,
as are some leafy vegetables and greens. People who get much of their
calcium from dairy products may want to select low-fat or fat-free
choices to reduce their intake of saturated fat.
Some conditions can interfere with the absorption of calcium
from the stomach. Poor vitamin D intake and inactivity decrease calcium
absorption. Low stomach acid can cause calcium carbonate to be poorly
absorbed, although it doesn't affect other forms of calcium the same
way. For those who either have low stomach acid or who take medicine to
block stomach acid, calcium citrate is better absorbed.
Those who have kidney stones, kidney failure, or high
parathyroid levels should talk with their doctors before taking calcium
supplements. People who are having treatment for cancer should talk to
their doctors or cancer team before taking vitamins, minerals, or other
supplements that might interact with the cancer drugs prescribed.
Relying on this type of treatment alone and avoiding or delaying
conventional medical care for cancer may have serious health
consequences.
Additional Resources
More information from your American Cancer
Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
Baron JA, Beach M, Mandel JS, van Stolk RU, Haile RW, Sandler
RS, Rothstein R, Summers RW, Snover DC, Beck GJ, Bond JH, Greenberg ER.
Calcium supplements for the prevention of colorectal adenomas. N Engl J Med.
1999;340:101-107.
Calcium. Memorial Sloan-Kettering Cancer Center Web site.
http://www.mskcc.org/mskcc/html/69157.cfm. Accessed June 4, 2008.
Cassileth B. The
Alternative Medicine Handbook: The Complete Reference Guide to
Alternative and Complementary Therapies. New York, NY:
W.W. Norton; 1998.
Cats A, Kleibeuker JH, van der Meer R, Kuipers F, Sluiter WJ,
Hardonk MJ, Oremus ET, Mulder NH, de Vries EG. Randomized,
double-blinded, placebo-controlled intervention study with supplemental
calcium in families with hereditary nonpolyposis colorectal cancer. J Natl Cancer Inst.
1995;87:598-603.
Giovannucci E, Rimm EB, Wolk A, Ascherio A, Stampfer MJ,
Colditz GA, Willett WC. Calcium and fructose intake in relation to risk
of prostate cancer. Cancer
Res. 1998;58:442-447.
Guise TA. Bone loss and fracture risk associated with cancer
therapy. Oncologist.
2006;11:1121-1131.
Holt PR. Dairy foods and prevention of colon cancer: human
studies. J Am Coll Nutr.
1999;18:379S-391S.
Hyman J, Baron JA, Dain BJ, Sandler RS, Haile RW, Mandel JS,
Mott LA, Greenberg ER. Dietary and supplemental calcium and the
recurrence of colorectal adenomas. Cancer
Epidemiol Biomarkers Prev. 1998;7:291-295.
Kushi LH, Byers T, Doyle C, Bandera EV, McCullough M,
McTiernan A, Gansler T, Andrews KS, Thun MJ; American Cancer Society
2006 Nutrition and Physical Activity Guidelines Advisory Committee.
American Cancer Society guidelines on Nutrition and Physical Activity
for cancer prevention: reducing the risk of cancer with healthy food
choices and physical activity. CA
Cancer J Clin. 2006;56:254-281.
Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney
RP. Vitamin D and calcium supplementation reduces cancer risk: results
of a randomized trial. Am
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Lipkin M, Newmark HL. Vitamin D, calcium and prevention of
breast cancer: a review.
J Am Coll Nutr. 1999;18:392S-397S.
Martinez ME, Jacobs ET. Calcium supplementation and prevention
of colorectal neoplasia: lessons from clinical trials. J Natl Cancer Inst.
2007;99:99-100.
McCullough ML, Rodriguez C, Diver WR, Feigelson HS, Stevens
VL, Thun MJ, Calle EE. Dairy, calcium, and vitamin D intake and
postmenopausal breast cancer risk in the Cancer Prevention Study II
Nutrition Cohort. Cancer
Epidemiol Biomarkers Prev. 2005;14:2898-2904.
Dietary supplement fact sheet: calcium. Office of Dietary
Supplements Web site.
http://dietary-supplements.info.nih.gov/factsheets/calcium.asp.
Accessed June 4, 2008.
Neugut AI, Horvath K, Whelan RL, Terry MB, Garbowski GC,
Bertram A, Forde KA, Treat MR, Waye J. The effect of calcium and
vitamin supplements on the incidence and recurrence of colorectal
adenomatous polyps. Cancer.
1996;78:723-728.
Thys-Jacobs S, Starkey P, Bernstein D, Tian J. Calcium
carbonate and the premenstrual syndrome: effects on premenstrual and
menstrual symptoms. Premenstrual Syndrome Study Group. Am J Obstet Gynecol.
1998;179:444-452.
Note:
This
information may not cover all possible claims, uses, actions,
precautions, side effects or interactions. It is not intended as
medical advice, and should not be relied upon as a substitute for
consultation with your doctor, who is familiar with your medical
situation.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
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