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The key to getting the most from a calcium supplement is to limit a single dose to 500 mg or less. Your body cannot absorb more than that at one time. For example, if you needed 1,000 mg a day, it would be best to take 500 mg twice a day for maximum calcium absorption.
Vitamin D is needed for calcium absorption. The vitamin doesn't have to be taken at the same time as the mineral, though some supplements combine both nutrients.
Some calcium supplements, such as calcium carbonate, are best taken with food because the stomach acid released during digestion helps absorption. Calcium citrate is different. It can be absorbed on an empty or full stomach. This type of calcium is often suggested for those over 50 who tend to have less stomach acid than younger people.
Mineral oil and some laxatives block calcium absorption. Tannins in tea and the fiber in wheat bran can also interfere with absorption. Be sure to talk to your doctor about all medicines and dietary supplements you take, as some supplements can reduce or increase the effects of prescription and nonprescription drugs.
While I recommend using food sources of calcium, calcium supplements are also effective in boosting the body’s source of calcium. In many studies, calcium citrate has been found to dissolve easier than carbonate or phosphate, and it is bioavailable, meaning your body can use more of what you ingest. If you take calcium supplements, be sure to follow these rules: avoid taking more than 500 milligrams at once. Take supplements with food for best absorption. Do not take supplements with high-fat or high-fiber foods, as these foods interfere with the absorption of calcium. Do not take calcium supplements with foods high in iron.
Here are a few things to keep in mind when choosing and taking a calcium supplement:
- Generally, calcium pills are better choices than multivitamins, which tend to have small amounts of elemental calcium.
- The National Osteoporosis Foundation recommends avoiding calcium products from unrefined oyster shell, bone meal, or dolomite that don't say "purified" or have the United States Pharmacopeia (USP) symbol on them, since these products have tended to contain higher levels of lead, a toxic metal.
- Because calcium, iron, and zinc supplements interfere with each other, take them several hours apart.
- Delay consuming calcium (either from food or supplements) for two to four hours after taking tetracycline antibiotics, as calcium can decrease their effectiveness. Also, ask your doctor or pharmacist whether a supplement will interact with any prescription medications you're taking.
- Don't exceed the daily dose recommended by the manufacturer, since doing so increases the risk for side effects.
- Vitamin D helps your body absorb calcium, but it's not necessary to take vitamin D and calcium at the same time. If you aren't getting enough vitamin D from sunlight, your diet, or your multivitamin, you may want to choose a calcium supplement that contains this ingredient.
This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.