Q: What’s your opinion on consuming eggshell powder as a form of calcium supplement?
A: Eggshells are a rich source of calcium carbonate (a form of calcium commonly found in dietary supplements); they also have a little strontium and some other bone-protective nutrients. But there is little evidence that getting calcium carbonate from eggshells offers any significant advantage over other sources.
We found just a couple of human studies. For instance, a study in the British Journal of Nutrition in 2002 compared eggshell powder, pure calcium carbonate, and a low-calcium “control” powder in 85 healthy postmenopausal Dutch women, with both treatment groups also receiving magnesium and other nutrients. After 12 months, those in the eggshell group had increased bone density in the hip, but not in the spine, compared to the control group. No increases were seen in the calcium carbonate group, while the control group lost a little bone density. The study had a number of problems, however, including that the women already had adequate calcium intake.
According to a 2003 review paper in the International Journal of Clinical Pharmacology Research, “Clinical and experimental studies show that eggshell powder has positive effects on bone and cartilage and that it is a suitable source of calcium in the prevention and treatment of osteoporosis.”
A few small companies sell eggshell powder (mostly marketed for pets), but it’s hard to know what you’re getting and whether the products are safe from bacteria or other contaminants. And unless the powders are standardized, you don’t know exactly how much calcium they contain. That’s also true if you make the powder yourself, as several websites suggest. Some people have reported digestive irritation from consuming eggshell powder.
If you want to do something with your eggshells, here are other suggestions: After grinding them, you can add the powder to natural cleaning products (for its abrasiveness) or to plant soil (as a fertilizer). You can also compost the shells.
Bottom line: Eggshells are potentially a good (and eco-friendly) source of bioavailable calcium—and a few supplement companies use them in their calcium formulas. But for better assurance of purity and proper dosage, we advise sticking with calcium supplements that have the USP Verified seal, indicating that they meet the requirements of the U.S. Pharmacopeial Convention. Even better is to get calcium from conventional dietary sources.