Calcium Supplement Absorption

Dear Jack,

I read a post from a woman being treated for osteoporosis. She said a good test for a calcium supplement is to put it in a glass of white vinegar (same pH as a stomach) for 20 min to see if it dissolves. Is this really a good test for a calcium supplement?

I tried it and hardly any of my calcium tablet dissolved in that time. If this does matter can you recommend a vegan calcium supplement that will break down either tablet, powder or liquid?


For some background, according to Advanced Nutrition & Human Metabolism (1999), the pH of the stomach is about 2.0. According to Krause’s Food, Nutrition, & Diet Therapy (2000), it ranges from 1 to 4. Vinegar tends to be about 2.0 to 3.0.

The New York State Department of Health has a web page Commonly Asked Questions About Calcium Supplements:

“Calcium must dissolve in your stomach before it can be absorbed in your intestines and then used by your body. A USP symbol on the label of a calcium supplement means that is it will dissolve in your stomach. If your supplement does not have a USP symbol, you can easily test it to find out if it will dissolve. Simply put the supplement into a glass of clear vinegar. This creates an acidic environment much like that of your stomach. Stir the solution occasionally. If the calcium supplement disintegrates within 30 minutes, it should dissolve in your stomach, too. If the supplement does not completely dissolve, choose an alternative calcium supplement.

“If you are taking acid blockers for indigestion, reflux or other gastrointestinal conditions, your body may use calcium citrate better than other calcium compounds. Acid blockers reduce the acid in your gastrointestinal tract that is usually required for calcium absorption. However, unlike other calcium compounds, calcium citrate does not require an acid environment for calcium absorption.”

I did a test with my Trader Joe’s Calcium Magnesium & Zinc supplement, which uses calcium carbonate – I broke one tablet in half and put it in 1/5 cup of apple cider vinegar. After 8 minutes it was completely dissolved.

The Office of Dietary Supplements at the National Institutes of Health has the following to say on their Dietary Supplement Fact Sheet: Calcium:

“The two main forms of calcium in supplements are carbonate and citrate. Calcium carbonate is more commonly available and is both inexpensive and convenient. Both the carbonate and citrate forms are similarly well absorbed, but individuals with reduced levels of stomach acid can absorb calcium citrate more easily. Other calcium forms in supplements or fortified foods include gluconate, lactate, and phosphate. Calcium citrate malate is a well-absorbed form of calcium found in some fortified juices [8]. The body absorbs calcium carbonate most efficiently when the supplement is consumed with food, whereas the body can absorb calcium citrate equally effectively when the supplement is taken with or without food [9].”

3 Responses to “Calcium Supplement Absorption”

  1. beforewisdom Says:

    Thanks Jack!

    FWIW, I discovered that it doesn’t take much googling around to find calcium citrate powder for sale. I also discovered that the coffee grinder I have for flax seeds will also reduce the calcium supplements I have to powder if I move the tablets around once or twice. Lastly, for about $7 you can get a plastic pill crusher from Amazon or a local drug store.

    Thanks much again for the information!

  2. Vinegar & Osteoporsis « Before Wisdom Says:

    […] I got this response from Jack Norris, vegan RD: AKPC_IDS += […]

  3. R. Alicia Says:


    Personally I have been using CalciAIM. It’s citrus powder that you mix with water to get free ionic calcium and bioavailable nutrients essential to its absorption. Their site is

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