Hold the Oyster, Keep the Shell: Calcium Supplements

Calcium is the most abundant mineral in the body. It is found naturally in some foods, added to others and available as a dietary supplement.

Calcium makes up much of the structure of bones and teeth and helps with body movements by keeping tissues, such as skin, strong and flexible. A small pool of calcium circulates in the blood and helps and assists with muscle function and blood clotting. Because almost all body calcium is stored in the skeleton, a dual X-ray absorptiometry (DEXA) scan of bone mineral density is used to assess a person’s cumulative lifetime. DEXA scans are a form of X-ray and usually take less than fifteen minutes to perform.

 Dairy products made with milk, yogurt and cheese can contain high amounts of calcium. Nondairy foods also can contain calcium. These can include green vegetables, such as kale, broccoli, turnip, mustard or collard greens, and okra, almonds, beans and canned sardines and salmon with bones. Some nondairy foods, such as fruit juices, plant-based milk, tofu, nutritional yeast (not baking yeast) and hot and cold cereals are fortified with calcium. The absorption of calcium varies depending on the type of food; absorption from dairy products and fortified foods is about 30%, while absorption from certain plants may be much lower.

Calcium is available in many dietary supplements, including multivitamin/mineral products and supplements containing calcium only or calcium plus vitamin D. The two most common forms of calcium in supplements are calcium carbonate and calcium citrate. People with low levels of stomach acid, such as those regularly taking antacids, may not absorb calcium carbonate very well, unless taken with food (which increases stomach acid levels).

Calcium citrate is less dependent on stomach acid for absorption than calcium carbonate, so it can be taken without food. Calcium supplements may use calcium obtained from limestone (calcium carbonate), oyster or other shells, marine algae, egg shells or be synthesized in a food lab.

The percentage of calcium absorbed from supplements, the same as with foods, depends on the calcium source, and also the total amount of calcium consumed at one time. According to the National Institutes of Health, as the amount of calcium intake increases, the percentage absorbed decreases. Absorption from supplements is highest with doses of 500 mg or less. For example; the body absorbs about 36% of a 300 mg calcium dose and 28% of a 1,000 mg dose.

Calcium supplements may cause gastrointestinal side effects, including gas, bloating or constipation. Calcium carbonate appears to cause more of these side effects than calcium citrate, especially in older adults who have lower levels of stomach acid. Symptoms can be alleviated by switching to a supplement containing a different form of calcium, taking smaller calcium doses more often during the day, or taking the supplement with meals.

Because of its ability to neutralize stomach acid, calcium carbonate is found in some over-the-counter antacid products, such as Tums and Rolaids. Depending on its strength, each pill could provide about 270 to 400 mg of calcium. Calcium supplements and antacids may interact with medications. Some medications may affect calcium levels, such as levothyroxine, lithium, and quinolone antibiotics. Be certain to coordinate your calcium intake with your health care provider.

It is possible to take too much calcium in supplement form. Excessive calcium intake can lead to elevated levels of calcium in the blood, called “hypercalcemia.” This can cause problems like kidney damage and life-threatening abnormal heart rhythms. Higher doses of calcium supplements, taken over a long time, may lead to kidney stone formation.

 It is very important to make an individualized supplement plan with a healthcare provider; to ensure the needed supplement in the needed amount, as well as needed monitoring is being done.

Iron can interfere with calcium absorption, as both are absorbed in the same area of the small intestine. To minimize this, iron-containing foods or iron supplements could be taken at least two hours apart from calcium supplements.

Think about adding calcium-containing foods throughout the day. For example, add dairy milk or fortified plant milk to coffee or tea ( rather than creamers), hot or cold cereal, or add some cheese, cream cheese or cottage cheese to scrambled eggs or to top toast. Snack on almonds, humus (garbanzos are a good calcium source), nut butters or mashed bean dips. Mix yogurt into any “creamy” dish or salad dressing. Think about including chia seeds, nuts or soybeans into salads, rice or pasta. Get familiar with cooking mustard and beet greens and kale. Make kale chips by baking individual kales leaves in the oven until crispy. Choose ingredients, such as juices, tofu, nut butters, crackers or cold cereals that are calcium fortified.

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