Calcium Absorption

Updated: November 9, 2022

Lara Pizzorno is the author of “Your Bones: How You Can Prevent Osteoporosis and Have Strong Bones for Life – Naturally” and a member of the American Medical Writers Association with 29 years of experience specializing in bone health.

Recently we asked Lara if she would help us provide a series of short, ongoing videos to help you (our customers and readers) stay up to date on the latest facts and science related to bone health and overcoming osteoporosis naturally.

In this latest video, Lara talks about what you need to know in order to absorb the calcium that you consume from your diet or supplements. Watch the video below (or read the transcript provided) and let us know what you think in the comments

Hi, I’m Lara Pizzorno and I’m here to share some information with you that I hope will help you to have healthier bones.

Our topic today is calcium and specifically, what do you need to know in order to absorb the calcium that you consume from either supplements or your diet. There are other considerations that impact your ability to absorb calcium. One of the most important, in addition to producing stomach acid so you can absorb calcium from calcium carbonate so that you should have calcium carbonate with a meal. Another consideration is your vitamin D status. Calcium is both actively and passively absorbed in the small intestines. And vitamin D is required, you must have it to active absorb calcium from your small intestines. No matter what form of calcium we’re talking about here whether it’s calcium in your food, calcium carbonate, calcium citrate or any other form of supplemental calcium.

In individuals who are vitamin D deficient, only 10-15% of the calcium that they ingest is absorbed; and the better your vitamin D status – remember optimal blood levels of 25OHD which is the circulating form of vitamin D in the blood stream, the form that is used to monitor vitamin D status.

Optimal blood levels of 25OHD are 60 -80 nano grams per mL. So when you’re in that range, you’ll be able to absorb the best amount of calcium from what you ingest.

In one study that was done, calcium absorption rates were 65% greater in individuals whose 25OHD levels in their blood were at least 34.6 nano grams per mL. And those who had levels of vitamin D circulating in their blood less than 20 nano grams per mL were only able to absorb less than half that amount of calcium. In another study of 23 vitamin D sufficient, postmenopausal women, they looked at how well the women were able to absorb calcium carbonate and calcium citrate in supplements. and what they found is that if they had adequate vitamin D, the women were both able to absorb calcium carbonate and calcium citrate in the same amount. But if they didn’t have enough vitamin D they were not able to absorb as much calcium and their parathyroid level hormones went up and they excreted more calcium in their urine when they did not have adequate vitamin D. But they found in the people that did have adequate vitamin D, the bioavailability of calcium carbonate and calcium citrate was identical. The cost of calcium carbonate was much less and people had to take much fewer pills of calcium carbonate. So the researchers recommended calcium carbonate for people with adequate vitamin D stores.

There are some other considerations that will help you make the most of the calcium you consume in the form of food or supplements and we’ll talk about those more in the next video. Thanks for tuning in!


Straub DA. Calcium supplementation in clinical practice: a review of forms, doses, and indications. Nutr Clin Pract. 2007 Jun;22(3):286-96. PMID: 17507729

Heaney RP, Dowell MS, Bierman J, et al. Absorbability and cost effectiveness in calcium supplementation. J Am Coll Nutr. 2001;20:239–246. PMID: 11444420

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This article features advice from our industry experts to give you the best possible info through cutting-edge research.

Lara Pizzorno
MDiv, MA, LMT - Best-selling author of Healthy Bones Healthy You! and Your Bones; Editor of Longevity Medicine Review, and Senior Medical Editor for Integrative Medicine Advisors.,
Dr. Liz Lipski
PhD, CNS, FACN, IFMP, BCHN, LDN - Professor and Director of Academic Development, Nutrition programs in Clinical Nutrition at Maryland University of Integrative Health.,
Dr. Loren Fishman
MD, B.Phil.,(oxon.) - Medical Director of Manhattan Physical Medicine & Rehabilitation and Founder of the Yoga Injury Prevention Website.,
Prof. Didier Hans
PHD, MBA - Head of Research & Development Center of Bone Diseases, Lausanne University Hospital CHUV, Switzerland,