Most everyone knows the need for calcium to maintain strong bones and prevent osteoporosis, but calcium is a supplement that seems to generate a lot of questions.
Here are some answers to the most commonly asked questions we get at the pharmacy.
What Type of Calcium Supplement Is Best?
There are many forms of calcium including calcium carbonate, citrate, and gluconate. There are also many dosage forms including tablets, liquid calcium supplements, and chewable calcium citrate.
For years health care professionals have thought that an acidic environment in the stomach was needed to break down calcium tablets so they could be absorbed from the GI tract; and that liquid calcium or calcium citrate, being more acidic than other calcium salts, absorbs better. However, multiple clinical studies have shown that this is not true. The amount of stomach acid does not seem to affect calcium absorption.1 And even though calcium citrate is more acidic than calcium carbonate, they both seem to absorb equally well.2 In fact, a study funded by a grant from the U.S. Public Health Service concluded that calcium absorbs equally well from calcium acetate, calcium carbonate, calcium citrate, calcium gluconate, calcium lactate, and calcium from milk.3
Brands of Calcium Supplements
There is at least one significant difference between the different types of calcium salts, and that is how much elemental calcium they provide. Calcium carbonate is not pure calcium. It is made up of 40% calcium and 60% carbonate. Calcium citrate has even less calcium in it. It only has 21% calcium and therefore 79% citrate. Here are some common brand names of various types of calcium:
- Calcium carbonate: Caltrate, OsCal, and Tums.
- Calcium citrate: Citracal and Solgar.
- Calcium gluconate: Cal-G and Kalcinate.
- Calcium lactate: Ridactate.
- Calcium phosphate: Posture and Posture-D.
So how many tablets do you have to take to get 1,000 mg of calcium?
In order to get 1,000 mg of calcium from calcium carbonate, you have to take 2,500 mg of Tums®. In order to get 1,000 mg of calcium citrate, you will need to take 4,700 mg of Citracal®. Calciuim gluconate, lactate, and phosphate have very small amounts of calcium in them, so they do not make very good supplements. Oyster shell, coral calcium, and bone meal are natural sources of calcium carbonate, but they often contain high levels of lead and other heavy metals, so I never recommend them.
What increases calcium absorption?
Often you will see calcium supplements with added vitamin D. The reason for this is that vitamin D is needed to absorb calcium. However, you do not have to take vitamin D at the same time you take calcium, but it does not hurt.
What decreases calcium absorption?
Bran, beans, black tea, and fiber can all decrease the absorption of calcium.
Calcium and iron supplements should not be taken at the same time because they bind together and do not absorb very well.4
The more calcium you take all at once, the less you can absorb, so it is much more effective to take smaller doses frequently throughout the day than one large dose once a day.
Side Effects of Calcium Supplements
Calcium supplement adverse effects usually only occur at high doses. Too much calcium can cause constipation and an increased risk for calcium kidney stones.
How Much Calcium Should I Take?
We used to have the RDA (Recommended Dietary Intake) and that was replaced by the RDI (Reference Daily Intake) and now we have the DRI (Dietary Reference Intake). Yes, they can be confusing, but fortunately the levels recommended for most vitamins and minerals in each chart are rather similar.
The Dietary Reference Intakes for Calcium are as follows:
- Kids 9 to 18 years old: 1,300 mg a day
- Adults 19 to 50 years old: 1,000 mg a day
- Adult Females 51 to 70: 1,200 mg a day
- Adult Males 51 to 70: 1,000 mg a day
- All adults 70 or older: 1,200 mg a day
Best Dietary Sources of Calcium
Milk, yogurt, and other dairy products are the food sources of calcium that most people think of first. However, many brands of soymilk and juices are fortified with enough calcium to provide a similar amount as milk. Other sources of calcium include sardines, salmon, kale, cabbage, tortillas, bread, and broccoli.
Calcium Supplements for Women
Inspite of the DRI, the National Osteoporosis Foundation recommends a higher dose of calcium for women who are not taking an estrogen supplement and adults who are over the age of 65. For them they recommend 1,500 mg of calcium each day.
A more comprehensive look at the best vitamins and supplements for women can be read by clicking here. Or, feel free to stop by the Compounding Pharmacy and talk with the on-call pharmacist.
My Recommendation
References
- Bo-Linn G, Davis G, Buddrus D, Morawski S, Santa Ana C, Fordtran J. (1984). “An evaluation of the importance of gastric acid secretion in the absorption of dietary calcium”. J Clin Invest 73(3): 640-7.
- Heaney R, Dowell M, Barger-Lux M. (1998). “Absorption of Calcium as the Carbonate and Citrate Salts, with Some Observations on Method”. Osteoporosis International 9(1): 19-23.
- Sheikh M, Santa Ana C, Nicar M, Schiller L, Fordtran J. (1987). “Gastrointestinal Absorption of Calcium from Milk and Calcium Salts.” N Engl J Med 317: 532-6.
- Cook J, Dassenko S, Whittaker P. (1991). “Calcium supplementation: effect on iron absorption”. American Journal of Clinical Nutrition. 53: 106-11.
photo of kale: convivial.org