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Calcium Supplement Guidelines

Calcium is an essential mineral found in great abundance in the body. 99% of all the calcium in the body is found in the bones and teeth. The remaining 1% is in the blood.


How much calcium is too much? It is recommended that you do not take more than the UL (tolerable upper limit) of calcium per day. UL for adult males and females is 2,000-2,500 milligrams/day. High calcium intakes can lead to constipation, an increased chance for developing calcium kidney stones, and may inhibit the absorption of iron and zinc from food. Consider talking to a medical provider to determine how much calcium consumption is best for you.


How should I get my calcium? The best way to get your calcium is from the foods you eat. A good source of calcium contributes at least 100 milligrams of calcium in a standard serving. Some good food sources of calcium are: milk and yogurt (300-450 mg), and dark green leafy vegetables (100-200 mg).


For people who cannot consume enough calcium from food and beverages, and are unable to make changes in their eating habits, calcium supplementation may be necessary to obtain adequate calcium intakes.


What increases calcium absorption? The calcium you consume from your diet or as a supplement is absorbed by the body in the small intestine. Not all the calcium you eat will be absorbed, some will pass through your body and be excreted as waste. A few ideas to increase the chance of absorption include:

  • Acidic conditions in the intestine-Calcium carbonate requires an acidic environment in order to be dissolved in the intestine and absorbed into the blood. Stomach acid production increases in the presence of food, creating an acidic environment. Therefore, calcium carbonate supplements should be taken with a meal. Calcium citrate does not require the presence of extra stomach acid to dissolve and be absorbed, and can be taken on an empty or full stomach.
  • Vitamin D-Calcium absorption is dependent on an adequate level of the active form of vitamin D. Often vitamin D is supplemented, along with calcium. Vitamin D supplements are usually not necessary because vitamin D is available from vitamin D fortified milk, foods such as fish and egg yolks, and exposure to sunlight.
  • Estrogen-Estrogen is a hormone that plays an important role in helping increase calcium absorption. After menopause, estrogen levels drop and so may calcium absorption.
  • Low calcium intakes-Your body absorbs calcium less efficiently as your intake increases, therefore it is best to take your calcium in smaller doses throughout the day to aid absorption. You should not take more than 500 mg of calcium at one time and allow 4-6 hours between doses.
  • Type of supplements-One factor affecting calcium absorption from supplement tablets is how well the calcium tablet dissolves. To ensure you are taking a supplement that will dissolve in your intestine, take one that meets the U.S. Pharmacopeia’s (USP) standards for dissolution. The USP letters on the label indicate that the supplement meets the USP standards for the amount of elemental calcium in a tablet and how well the tablet dissolves. According to USP standards, a calcium tablet must contain 90-110% of the amount of elemental calcium listed on the supplement label and must dissolve in 30-40 minutes.


What type of calcium supplement is best? Try to consume calcium from foods or beverages. If you take calcium supplements, calcium citrate and calcium carbonate are the best choices because they are easy to find, contain relatively large amounts of elemental calcium, and dissolve well in the body.


Source: Arizona Cooperative Extension (2017)

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