Calcium is the most abundant mineral in the human body, and for good reason: All cells need calcium to work. In fact, calcium performs so many diverse functions that virtually no major organ system can function properly without it.
Your body is constantly breaking down old bone cells and growing new ones, the same way it sheds and replaces skin cells. To help keep them strong, the body stores more than 99 percent of its calcium in the bones and teeth. The rest is released in the body as needed to help muscles and blood vessels contract and expand, to secrete hormones and enzymes, and to send messages through the nervous system.
The body’s calcium concentration and bone strength peaks around age 30. As we age, those concentrations decline, particularly in women with reduced estrogen levels, because it is eliminated from the body through urine, feces and sweat.
But you can reduce these losses by consuming the recommended amounts of calcium throughout adulthood and by living a healthy, active lifestyle.
Calcium helps prevent and treat bone conditions caused by low calcium, such as rickets, a condition in children involving softening of the bones; osteomalacia, a softening of bones involving pain; and osteoporosis, a gradual weakening and hollowing out of bone tissue that affects more than 10 million adults in the U.S. over age 50.
Among women, calcium helps alleviate premenstrual syndrome, prevent strokes, reduce leg cramps during pregnancy and prevent preeclampsia, high blood pressure during pregnancy. Calcium also helps to reduce fluoride levels among children, reduce high blood pressure and reduce the risk of colon and rectal cancers. Calcium carbonate is used as an antacid for heartburn.
As an added benefit, adults and children with high calcium intakes are less likely to gain weight or become overweight or obese than those who consume little calcium. Research shows that calcium consumption from such dairy products as yogurt increases weight loss, body fat loss and lean body mass. (Studies can be found here, here and here.)
Am I Getting Enough?
The body doesn’t absorb all of the calcium that it consumes. In fact, it absorbs only about 30 percent of the calcium it receives from foods, depending on the type of food consumed.
For example, caffeine, sodium and alcohol increase the amount of calcium that is eliminated through the urine. And alcohol prevents enzymes in the liver from processing vitamin D, a major helper in the absorption of calcium. Phytic acid (found in whole-grain products and wheat bran) and oxalic acid (found in spinach, collard greens and sweet potatoes) also can inhibit calcium absorption.
The exact amount of calcium you need, however, depends on a number of factors, including age and gender.
Growing children and teenagers need more calcium than young adults. Postmenopausal women and people older than 70 years, who experience greater bone loss and do not absorb calcium as well, need extra amounts to prevent osteoporosis. That’s because while young children absorb as much as 60 percent of their calcium intake, absorption decreases to 15 to 20 percent in adulthood and continues to decrease with age.
The National Institutes of Health recommends the following age-based daily calcium intake:
- Birth to 6 months: 200 mg
- Infants 7 to 12 months: 260 mg
- Children 1 to 3 years: 700 mg
- Children 4 to 8 years: 1,000 mg
- Children 9 to 13 years: 1,300 mg
- Teens 14 to 18 years: 1,300 mg
- Adults 19-50 years: 1,000 mg
- Adult men 51 to 70 years: 1,000 mg
- Adult women 51 to 70 years: 1,200 mg
- Adults 71 years and older: 1,200 mg
- Pregnant and breastfeeding teens: 1,300 mg
- Pregnant and breastfeeding adults: 1,000 mg
If you’re not getting enough calcium, you probably won’t notice any short-term symptoms because the body maintains calcium levels in the blood by taking it from your bones. In the long term, however, low calcium intake can have serious consequences, resulting in such conditions as osteopenia (low bone mass), osteoporosis and bone fractures.
Symptoms of serious calcium deficiency include numbness and tingling in the fingers, convulsions and abnormal heart rhythms.
Sources of Calcium
To fuel bone growth, keep bone density strong and prevent osteoporosis, you need a good supply of calcium from dairy products and other foods. Calcium-rich foods include:
- Dairy products, such as milk, yogurt and cheese;
- Green leafy vegetables, such as kale, broccoli, spinach, collard greens and Chinese cabbage;
- Black-eyed peas, green peas, white beans and soy beans;
- Some fish, such as canned sardines and salmon;
- Calcium-enriched breakfast cereals, fruit juices, soy and rice beverages, and tofu.
People who do not eat enough calcium-rich foods — including those who are lactose intolerant, who cannot digest the natural sugar found in such dairy products; vegans, who eat no animal products; and ovo-vegetarians, who eat eggs but no dairy products — should take a calcium supplement.
But you also need an ample supply of vitamin D, a vital nutrient the body obtains from some foods and produces when the skin is exposed to sunlight. Vitamin D is key in absorbing calcium from the food you eat — calcium that would otherwise get sent out of the body as waste. Good sources of vitamin D include:
- Salmon, tuna, halibut, mackerel, sardines and herring;
- Cod liver oil;
- Fortified milk, soy milk, yogurt, butter, margarine, cheese, orange juice, cereal;
- Sunlight, but be sure to protect your skin from sun damage with a broadband sunscreen of SPF 15 or higher.
Ask your health care provider how calcium can help you.