Global Calcium Bioavailability Study Reveals Regional Absorption Gaps

A study published in The Journal of Nutrition estimates that an average of just 30.7% of the calcium available in the global food supply is absorbable by the body, once dietary inhibitors are accounted for.¹ The analysis, led by researchers from the International Life Sciences Institute (ILSI) U.S. and Canada with support from Balchem Corporation, is the first application of a previously published calcium bioavailability algorithm to worldwide food supply data, and it points to substantial regional gaps between how much calcium a population's food supply contains and how much of that calcium the body can use.

“It’s great to see our algorithm being applied in a global context for the first time,” stated Stephane Vidry, PhD, executive director, ILSI U.S. and Canada and ILSI Global.² “The findings shine a spotlight on the challenge anti-nutrients pose for mineral absorption, compromising the accuracy of intake measurements and limiting the impact of diet and supplementation.”

What Problem Is the Study Addressing?

Calcium adequacy has been assessed by measuring total calcium content in a population's diet, without accounting for how much of it the body can absorb, the researchers explain. Absorption is reduced by phytates and oxalates, compounds common in plant-based foods, which bind to calcium and form complexes that pass through digestion largely unabsorbed.

How Was the Research Conducted?

The researchers applied a calcium bioavailability algorithm—developed in earlier work by Weaver and colleagues—that weighs calcium load most heavily, with oxalate exerting a greater suppressive effect on absorption than phytate. They mapped calcium, phytate, and oxalate data onto Food and Agriculture Organization (FAO) Food Balance Sheets and generated country- and region-level estimates.

Which Foods Contribute the Most Bioavailable Calcium?

Bioavailable calcium was lower than total calcium across every food category examined. Milk products supplied the highest average bioavailable calcium per serving (78 mg from 229 mg total), reflecting both high calcium content and the absence of absorption inhibitors. The researchers found that milk remained the predominant source of bioavailable calcium because of this reason.

“Although several plant-based food groups, including fruits, vegetables, and cereals, had relatively high estimated fractional calcium bioavailability, their contribution to total calcium in the food supply was low because of low calcium concentration,” the researchers also noted. Pulses averaged 34 mg bioavailable calcium from 99 mg total.

Which Regions Are Most Affected?

Africa, Southeast Asia, the Middle East, and parts of South America showed the lowest bioavailable calcium supply, with some countries in Southeast Asia appearing to meet total calcium recommendations falling short once bioavailability was factored in.

What Are the Limitations and Impacts?

The authors did note limitations to the study. First, Food Balance Sheets reflect national food availability, not individual intake, and don't capture life-stage needs. The analysis assumed worst-case co-ingestion of calcium with phytates and oxalates, and USDA-based composition data may not reflect regional variation in crops. Additionally, the algorithm was validated only in healthy adults.

Vidry commented on the impact of the findings. “This ultimately highlights the need for future research to incorporate bioavailability data into intake data to better reflect regional dietary patterns and nutrient interactions,” he explained. “Strengthening this evidence will enhance our ability to design strategies that improve access to bioavailable calcium through more tailored food recommendations, fortification, supplementation, and other policy approaches.”

“These findings underscore the need to raise awareness of the impact that these anti-nutrients can have on mineral nutrition,” added Eric Ciappio, PhD, RD, senior manager, nutrition science, Balchem HNH. “Ultimately, if calcium cannot be properly absorbed due to the presence of anti-nutrients, many people are missing out on crucial health benefits.”

How Do These Findings Compare to Earlier Reporting on the Algorithm?

A 2024 Nutritional Outlook article by Ciappio introduced the underlying bioavailability algorithm shortly after its original publication, focusing on its mechanics rather than global-scale application.³ That piece cited findings that oxalate could reduce calcium absorption by up to 10% at relatively low concentrations, and that ignoring phytate content could overestimate absorption by up to 26%. It framed these findings around supplement formulation, noting that chelated calcium showed 1.5 to 2 times greater absorption than calcium citrate or calcium carbonate in cited data.

References

1. Karosas T, Reyes E, Forester S, Israel E, Weaver CM. Global calcium bioavailability. J Nutr. Published online July 27, 2026. doi:10.1016/j.tjnut.2026.101759
2. Balchem Corporation. New research shows only 30% of calcium in global food supply is bioavailable. August 18, 2026. Accessed August 19, 2026.
3. Ciappio E. Cracking the code: advancements in calcium absorption and nutritional understanding. Nutritional Outlook. July 23, 2024. Accessed August 19, 2026. https://www.nutritionaloutlook.com/view/cracking-the-code-advancements-in-calcium-absorption-and-nutritional-understanding