Avid gardeners will tell you that calcium carbonate is added to soil to increase pH – make soil more alkaline – and also increase calcium levels. Pharmaceutically purified calcium carbonate is an easily available and affordable calcium supplement. Chewable calcium carbonate tablets – Rolaids, Tums and other brands – are sometimes taken as inexpensive calcium supplements, though they are designed as antacids, to relieve acid indigestion. Belching is an expected antacid side effect.
Calcium carbonate deactivates digestive acids in the human stomach the same way that it works to de-acidify soil – by neutralizing acids. Your stomach regularly secretes hydrochloric acid, with its abundance of free hydrogen atoms, to help break down protein. Too much stomach acid can cause great physical distress, which leads people to reach for antacids. All antacids reduce acidity by counteracting or neutralizing acid. In the case of calcium carbonate this neutralization occurs when its oxygen atoms "capture" free hydrogen. Burping or belching is the side effect of this chemical reaction.
The two main types of calcium used in dietary supplements are calcium citrate and calcium carbonate. A better choice for people with lower levels of stomach acid, calcium citrate is more expensive and doesn't need to be taken with food. Inexpensive over-the-counter antacid tablets, or chews containing calcium carbonate, typically provide 200 to 400 mg of calcium each and should be taken with food – preferably after the meal -- for best absorption. Be sure to consume only purified calcium carbonate, or products marked with the United States Pharmacopeia (USP) symbol. Supplements made from unrefined oyster shell, bone meal or dolomite without these reassurances may contain high levels of lead or other toxic metals.
Taking Calcium Carbonate
It's best to get all or most of your calcium for milk or other food sources such as dark green leafy vegetables, soft-boned fish, dairy products and calcium-fortified beverages and foods. But supplementary sources can help if your doctor thinks you need more calcium. Slowly increase your calcium dose, starting with an extra 500 mg per day – spreading that dose out throughout the day to increase absorption and also reduce possible side effects. Increase the amount of daily calcium you're taking by a small amount each week, until you're taking the recommended amount.
Side Effects & Safety
Often the most noticeable or quickest side effect from taking calcium carbonate supplements is burping or belching; some people also pass gas. Taking calcium carbonate supplements such as Alka-2, Rolaids, Titralac and Tums may also cause constipation. Some side effects can be prevented or resolved by eating high-fiber food and drinking more fluids. It's important to take calcium supplements only as directed. According to the Mayo Clinic there may be a link between calcium-only supplements and heart disease, if excess calcium attaches to fatty plaques in arteries–causing hardening of the arteries and increasing heart attack risk. Too much calcium also increases the risks of kidney stones, impaired absorption of iron and zinc and prostrate cancer.
- National Digestive Diseases Information Clearinghouse: Indigestion
- NIH Medline Plus Medical Encyclopedia: Calcium Supplements
- Mayo Clinic: Calcium and calcium supplements -- Achieving the Right Balance; December 2010
- Arizona Cooperative Extension; Calcium Supplement Guidelines; Linda Houtkooper, et al.; January 2011