What is calcium, and what does it do?
Most people know that calcium is needed for strong bones, but it's also needed to help blood vessels and muscles contract and expand, to send messages through the nervous system, and to secrete hormones and enzymes. This is the most abundant mineral in your body and makes up 1%-2% of adult human body weight. Over 99% of it is stored in bones and teeth with the rest stored in blood, muscle, and other tissues.
How much do you need to consume?
There is a great deal of concern over Americans not meeting the recommendations for calcium intake. The recommendations for calcium are listed as an Adequate Intake:
|Age||Adequate Intake for Calcium|
|0 to 6 months||*210 mg from breast milk 315 mg from formula|
|7 to 12 months||*270 mg from breast milk 335 mg from formula|
|1 to 3 years||500 mg|
|4 to 8 years||800 mg|
|9 to 13 years||1,300 mg|
|14 to 18 years||1,300 mg|
|19 to 50 years||1,000 mg|
|51+ years||1,200 mg|
*Breast milk has been shown to have a higher rate of calcium absorption than formula, so calcium requirements are higher for formula-based diets. Calcium needs during pregnancy and lactation do not change from ages 14 to 50.
What are sources of calcium?
Calcium is found in a variety of foods, but the amount that your body absorbs varies. Oxalic acid and phytic acid both interfere with the absorption of calcium. Foods rich in oxalic acid are spinach, rhubarb, sweet potatoes, and beans. Foods rich in phytic acid are unleavened bread, nuts, seeds, and raw beans. You will absorb some of the calcium in these foods, but not as much as you would from foods that do not contain oxalic acid or phytic acid. For example, calcium absorption from dried beans is about half of what you absorb from milk, and calcium absorption from spinach is about one-tenth of that absorbed from milk. There is no need to omit these foods from your diet. Instead, consume a variety of calcium-rich foods throughout the day.
According to the USDA Nutrient Database, the calcium content of some common foods is shown below:
|Cheese, cheddar||1 ½ oz shredded||306 mg|
|Collards, frozen, boiled||1 cup||357 mg|
|Cottage cheese, 1% milk fat||1 cup||138 mg|
|Milk, nonfat||1 cup||306 mg|
|Powdered milk, nonfat||1 tbsp||50 mg-100 mg|
|Salmon, canned with bones||3 oz||181 mg|
|Sardines, canned in oil, with bones||3 oz||324 mg|
|Soy milk||1 cup||93 mg|
|Tofu, soft, made w/calcium sulfate||½ cup||138 mg|
|Yogurt, plain, low-fat||1 cup||415 mg|
|Yogurt, fruit, low-fat||1 cup||245 mg-385 mg|
You can also increase your calcium intake by
- adding nonfat powdered milk to cereals (hot and cold), soups, gravy, baked goods, or casseroles,
- using nonfat milk in place of water in recipes (pancakes, pudding, hot cereals, and mashed potatoes), and
- having yogurt dips for vegetable and chips.
Do I need to take a calcium supplement?
A well-balanced diet can be enough to reach your recommended intake of calcium. When diet is not enough, a calcium supplement may be necessary. In the case of calcium supplements, more is definitely not better. Calcium absorption is most efficient when the dose is 500 mg or less. This means that taking 1,000 mg at one time is less effective than taking two separate doses of 500 mg.
Calcium exists in nature combined with other chemicals. These compounds are what you will find in supplements and include calcium carbonate, calcium phosphate, calcium lactate, and calcium citrate. Calcium carbonate is the most common one because it is inexpensive and convenient. People who have decreased stomach acid (for example, older adults and those who take antacids) are better off taking calcium citrate. According to the National Osteoporosis Foundation, "Calcium supplements prepared from unrefined oyster shell, bone meal, or dolomite may contain lead or other toxic metals," so you need to pay attention to the source of calcium in your supplement.
Calcium supplements may cause gas, bloating, and/or constipation. There may be options to help relieve this. You can try spreading out dosages of the supplement throughout the day, try taking it with food, try a different brand, or speak with your doctor or pharmacist for assistance.
What happens if I do not have enough calcium?
Bone is a living tissue that constantly breaks down and builds back up. Up until around the age of 30, consuming an adequate amount of calcium with enough physical activity ensures that your body builds more bone than it breaks down. The majority of adult bone mass is acquired by age 18 in girls and 20 in boys. After that, breakdown typically exceeds the amount of bone being built. For this reason, it's essential to maximize bone stores when it's still possible. The amount that you lose after age 30 will be impacted by genetics, ethnicity, physical activity level, sex hormone levels, diet, and gender. You can replace what you lose with the foods you eat and your activity level, but you can't increase how much you store. When bone mass drops and there is a deterioration of bone tissue, osteoporosis can occur. Osteoporosis causes bones to be susceptible to fractures. Depending on the severity of the damage, bones can break from a minor fall, or in severe cases, from sneezing.
Other factors can put you at risk for low calcium levels.
Amenorrhea: Research has shown that young women who do not get their period due to anorexia nervosa have reduced net calcium absorption, higher urinary calcium excretion, and a lower rate of bone formation in comparison to those who menstruate regularly. Reduced calcium retention and lower bone mass have also been seen in exercise-induced amenorrhea.
Lactose intolerance: Many people find that consuming dairy products causes bloating, gas, cramping, and/or diarrhea. This is often from your body's inability to break down the lactose found in dairy foods. Lactose is the sugar that naturally occurs in these foods. Avoiding dairy foods can put you at risk for calcium deficiency. Fortunately, there are things that you can do to help with these symptoms. The first thing is to try to consume smaller amounts of dairy foods. Studies have shown that lactose intolerance is dose-dependent and different people have the intolerance at different levels of severity. When this doesn't work, you can purchase dairy products that have the lactose broken down for you. Lactaid products have taken the lactose and broken it up so that your body does not have to.
Is there such a thing as too much calcium?
The Tolerable Upper Limit (UL) for calcium for children and adults ages 1 year and older is 2,500 mg/day. Excessively high intakes would have to come from supplements alone or supplements in combination with dietary sources. The dangers of excessive consumption are impaired kidney function, hypercalcemia, and decreased absorption of other minerals (iron, zinc, magnesium, and phosphorus). Calcium has been shown to interfere with iron absorption. It's best to take the recommended amounts of calcium separate from iron-containing foods or supplements.
Calcium also has the potential to interact with medications by decreasing the absorption of the medication. Some affected medications are digoxin, fluoroquinolones, levothyroxine, antibiotics in tetracycline family, and phenytoin. Your doctor and pharmacist can provide further information about this.