Calcium is most abundant mineral in the body. It is found in a variety of natural and fortified foods, in dietary supplements, and also available in certain medicines (such as antacids). Calcium is an important mineral that is required for vascular contraction and vasodilation, muscle function, nerve transmission, intracellular signaling and hormonal secretion, though less than 1% of total body calcium is needed to support these critical metabolic functions. Serum calcium is very tightly regulated and does not easily fluctuate with changes in dietary intakes; the body uses bone tissue as a reservoir for, and a source of calcium, to maintain constant concentrations in blood, muscle, and intercellular fluids. The remaining 99% of the body’s calcium supply is stored in the bones and teeth where it supports their structure and function. Bone itself undergoes continuous remodeling, with constant resorption and deposition of calcium into new bone. The balance between bone resorption and deposition changes with age. Bone formation exceeds resorption in periods of growth in children and adolescents, whereas in early and middle adulthood both processes are relatively equal. In aging adults, particularly among postmenopausal women (however men can be at risk too), bone breakdown exceeds formation, resulting in bone loss that increases the risk of osteoporosis over time.
Inadequate intakes of dietary calcium from food and supplements generally produce no short-term noticeable symptoms because circulating blood levels of calcium are tightly regulated. However hypocalcemia can result primarily from certain medical problems or medical treatments, and the use of certain medications. Although an outright calcium deficiency is uncommon, dietary intakes of calcium below recommended levels could have negative health consequences in the long term. Certain groups can have a higher risk of a deficiency and may need to supplement with calcium including postmenopausal women, amenorrheic women and certain women athletes. Also individuals who are lactose intolerant or have an allergy to cow’s milk, and people who are vegetarian and vegan.
Over the long term, inadequate calcium intake can lead to osteopenia which if untreated can lead to osteoporosis. The risk of bone fractures also increases, especially in older individuals. Calcium deficiency can also cause rickets, though it is more commonly associated with vitamin D deficiency.
Food sources include: dairy products (milk, yogurt, and cheese) sardines and canned pink salmon (that include the bones). Nondairy sources include vegetables, such as Chinese cabbage, kale, and broccoli. Many foods area also fortified with calcium.
- Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
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- National Institutes of Health. Optimal calcium intake. NIH Consensus Statement: 1994;12:1-31.
- U.S. Department of Agriculture, Agricultural Research Service. USDA National Nutrient Database for Standard Reference.
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