By Dena McDowell, MS, RD

Calcium is the most abundant mineral found in the human body. The majority (99%) is stored in the bones and teeth; the rest is stored in muscle tissue and blood. In addition to bone building and remodeling, calcium is also responsible for muscle contraction, central nervous function and hormone secretion.

The importance of calcium increases with age

Calcium deficiency is of major concern in the United States. An estimated 44-87% of Americans don’t get enough. An easy way to think of calcium and bone health is to imagine the bones as a savings account at a bank. You see, until the ages of 30-35 the body stores calcium in the bones. However, after this time calcium is no longer stored in bones. As a result, when the body tries to remodel bones its only source of calcium is ingested calcium. If you’re not eating enough calcium, the body has nothing to use. Thus, the body cannot remodel the bones, and bone density subsequently decreases. The calcium you consume early in life is deposited into your “bone” savings account. If little calcium is saved, then there will be little to spend when retirement comes (i.e. when the body tries to remodel your bones).

Calcium deficiency leads to osteoporosis

Without an adequate, constant supply of calcium the bones become weaker and develop tiny holes. These “porous bones” lead to osteoporosis. Currently 10 million Americans—80% of whom are women—have osteoporosis. Moreover, 34 million Americans are considered to have the premature form of osteoporosis called osteopenia. Having either disease increases the risk of fractures in the hip, spine, wrist, pelvis and ribs. Osteoporosis was once considered an older women’s issue. However, now it affects children as young as 12 years old. Below is a table outlining the Recommend Daily Allowance (RDA) for calcium.

RDA for Calcium

Age	Calcium (milligrams)
0-6 months	210
7-12 months	270
1-3 years	500
4-8 years	800
9-13 years	1300
14-18 years	1300
19-50 years	1000
51 plus	1200

Dietary sources of calcium

The majority of calcium comes from dairy sources. The new food guide pyramid recommends 2-3 servings of low fat or fat free dairy each day. One serving equals 8 ounces. If dairy products are not tolerated, calcium can also be obtained from other sources, including lactose-treated milk, fortified soy or rice beverages, fortified cereals and juice and green vegetables. Below is a list of common foods that are rich in calcium.

Common Food Sources of Calcium

Food	Serving Size	Calcium (milligrams)
Yogurt, plain	8oz.	415
Yogurt, fruited	8oz.	245-384
Sardines, bone included	3 oz.	324
Cheddar cheese, shredded	1.5 oz.	306
Milk, whole-fat free	8 oz.	294-302
Milk, lactose treated	8 oz.	285
Mozzarella	1.5 oz.	275
Orange juice, calcium fortified	8 oz.	200-260
Salmon, bones included	3 oz.	181
Cottage cheese	1 c.	138
Tofu, firm	½ c.	138
Spinach, cooked	½ c.	120
Turnip greens, cooked	½ c.	99
Kale, cooked	1 c.	94
Ice cream, vanilla	½ c.	85
Soy or rice milk, calcium added	1 c.	80-500
Sour cream, reduced fat	2 Tb.	32
White bread	1 slice	31
Broccoli, raw	½ c.	21

*Adapted from www.nal.usda.gov/fnic/cgi-bin/nut_search.pl

Calcium absorption decreases with age

It is estimated that nearly 60% of dietary calcium is absorbed during childhood and early adulthood. As an adult the absorption rate decreases to a mere 20%. To help the absorption process it is recommended that vitamin D be added to the calcium source. Vitamin D helps the calcium to become more easily absorbed in the blood stream and bones. Vegetables rich in phytates and oxalate hamper calcium’s absorption. Vegetarian’s who don’t consume dairy may be at increased risk of having a calcium deficiency. Research also shows that following high protein diets or eating foods high sodium may lessen body’s ability to absorb calcium.

Who’s at-risk from calcium deficiency?

Populations most at risk of a calcium deficiency are post-menopausal women due to poor estrogen stores, as well as amenorrheic girls—especially those suffering from the female athlete triad (see “What You Should Know About The Female Athlete Triad”). People who are strict vegetarians or lactose intolerant are also at risk for deficiency.

When to take a calcium supplement

If diet alone cannot meet calcium needs, supplementation is recommended. The most common calcium supplements are either in a carbonate or citrate form. Side effects of supplements include: gas, bloating and constipation. Magnesium is commonly added to prevent constipation. Vitamin D is also commonly added to aid in the absorption of the supplement. Timing and dosage of calcium supplements are important. The body can only metabolize about 500 milligrams of calcium at one time; therefore taking a calcium supplement with a dairy rich meal limits the absorption. It is best to take a supplement that is around 500 milligrams either between meal times or with a non-dairy rich meal.

By adding calcium to your diet you’ll help protect your bones and reduce your risk of bone fractures. Some tips for incorporating more calcium in your diet include: substituting milk for soda, using milk in recipes that call for water, adding cheese as a snack or having a fruit smoothie are easy ways to get more calcium into the diet. Remember to bank on calcium. Creating a large savings bank early on will prove lucrative bone benefits later on.

For information on the your calcium intake during cancer treatments see the following article from TheDietChannel: Calcium: Special Requirements During Cancer Treatment.