Calcium Supplements 101

As with all vitamins and minerals, it's best to get calcium from food sources.  However, as we learned in the last post, it can be difficult for many people to get the 1000 - 1200 mg needed from food alone.  Many physicians and dietitians will then recommend taking added supplements.  If you are unsure, consult your doctor.


Choosing a supplement takes a little detective work.  
  • Select a supplement that has no more than 500-600 mg and contains vitamin D.  Vitamin D is necessary for the absorption of calcium.
  • Look for "USP" (United States Pharmacopeia) or "CL" (Consumers Lab) on the label.  These are voluntary industry standards, but do assure quality, purity and its ability to be dissolved.
  • Choose calcium carbonate or calcium citrate sources.  This is listed on the nutritional facts label.  
    • Calcium carbonate is the least expensive and is a good choice for most people. This is a more concentrated form, so one pill is usually one serving. Calcium carbonate should be taken with food.
    • For people with sensitive stomachs or with less acid production, calcium citrate is a better choice.  It's easier to absorb and can be taken without food. One serving size is usually 2 pills, so be sure to check the label. Anyone on acid blockers should choose calcium citrate.
  • Avoid dolomite, oyster shell and bone meal sources.  These have potential lead and other toxic metal content.
  • Take only 500 - 600 mg at a time.  No more than 500 mg can be absorbed at once, the rest would be excreted through urine, creating what one of my professors called "expensive urine."
  • If problems with gas or bloating occur, spread supplements throughout the day and be sure to take them with food. Liquid and chewable calcium supplements are already partly broken down and are often easier on your stomach. If you still have problems, switch to calcium citrate or try a different brand.
  • Constipation can be a problem with calcium supplements.  Be sure to drink 8 - 10 glasses of fluids each day, and increase your fiber intake by eating more whole grains, beans, fruits and vegetables. 
It is possible to get too much calcium, though highly unlikely if you are only getting it from food.  If you are consuming supplements of any type more is not better! The upper tolerable limit for calcium is 3000 for children ages 9 - 18, 2500 mg for adults age 19 - 50, and 2000 mg for those 51 and older.

Taking calcium supplements with some medications can reduce the absorption of that medication.  The thyroid medication levothyroxine, bone density medications such as biophosphates and certain antibiotics in the tetracycline class, need to be consumed at least 2 hours apart.

Some things can interfere with the absorption of calcium. 
  • Medications. Antacids with aluminum or magnesium, some diuretics, laxatives and glucocorticoids such as prednisone, will increase the amount of calcium being secreted by urine.  Physicians will want to monitor long term use of such medications, and possibly ask you to increase the amount of calcium you consume during that time. 
  • Oxalic acid found in some veggies such as spinach and beet greens actually binds with the calcium, preventing less of it to be absorbed by your body.  You will still get some calcium from the food, but not as much. 
  • Very high intakes of caffeine, alcohol, sodium, potassium, and phosphorus.  Consume these in moderation.
Calcium is so important to the health of our skeletal structure, muscles and nervous system.  It's best to get calcium from the foods you eat, but taking a supplement is recommended if you are not getting enough.  The key is to be mindful choosing your supplement and how you take it.