In adults over 65, the prevalence of low bone mineral density (LBMD), including osteopenia and osteoporosis, rises steeply, with women disproportionately affected. About 60% of women and nearly 25% of men in this age group have LBMD, and hip fractures become increasingly common, often leading to loss of independence and higher mortality.

Calcium is essential for muscle contraction, nerve signaling, blood clotting, and hormone release prompting tight regulation of blood levels. When intake drops, bone and dental tissues are sacrificed to preserve serum calcium, making prevention of deficiency essential. Studies link inadequate calcium to greater risk of both osteoporosis-related fractures and tooth loss.

How Biology Maintains Sufficient Blood Calcium

To keep blood calcium stable, the body relies on parathyroid hormone (PTH), secreted when levels fall slightly. PTH mobilizes calcium from bone, increases kidney reabsorption, and activates vitamin D to enhance intestinal absorption. Because of this regulation, serum calcium values may appear normal despite chronic deficiency. This highlights the need to additionally assess intake, bone density, and related markers rather than relying on blood calcium alone.

Why Prevention Matters Across the Life Course and in Pregnancy

Once bone is lost, regaining density is difficult. Adequate intake during youth and midlife helps build peak bone mass, while sufficiency later in life slows decline. Pregnancy places additional demand on maternal calcium reserves. If intake is inadequate, calcium is drawn from the maternal skeleton to support fetal skeletal development, potentially accelerating postpartum bone loss.

The Food Supply and Calcium Intake

Although calcium-rich foods like dairy, leafy greens, fortified products, nuts, seeds, and bone-packed fish may be abundant, dietary shifts have favored ultra-processed foods, typically low in calcium. From 2021–2023, these items accounted for over 55% of daily calorie intake among U.S. adults which now represent about 73% of the food supply.

Supplementation

When diet alone cannot provide sufficient calcium, supplementation may be warranted. Adults generally require about 1,000 mg/day, with needs rising to 1,200 mg/day for women over 50 and men over 70. Excess intake above 2,000–2,500 mg/day increases the risk of hypercalcemia and kidney stones.

Calcium citrate is often preferred over calcium carbonate, particularly for individuals with low stomach acid or kidney stone risk. In the gut, calcium binds dietary oxalate, lowering its absorption and reducing urinary oxalate levels. Once absorbed, citrate further inhibits calcium oxalate crystallization in the kidneys, lowering stone risk.

Absorption, Interactions, and Food Factors

Calcium absorption is enhanced by vitamin D with dietary fat but hindered by oxalates, phytates, excess fiber, and competing minerals such as iron and magnesium. Because these nutrients share intestinal transport pathways, high-dose calcium supplements are best taken separately from iron or magnesium to improve bioavailability.

Summary and Conclusion

Calcium sufficiency is critical not only for strong bones and teeth but also for maintaining essential physiological functions. Older adults, pregnant women, and those with high intakes of ultra-processed foods are especially vulnerable to insufficiency. Because serum calcium is not a reliable marker of adequacy, prevention requires attention to dietary patterns, risk factors, and, when necessary, supplementation.

Registered dietitians are well positioned to help individuals balance dietary sources, avoid risks of over-supplementation, and tailor intake to personal health needs. Partnering with a dietitian can help tailor intake to personal health needs, slowing decline and lifelong preservation of bone and systemic health. Many insurance plans fully cover nutrition counseling for those at risk of LBMD.

About the Author

Patrick Traynor, PhD, MPH, RD, CSOWM, CPT, is a registered dietitian and founder of MNT Scientific, LLC (MNTScientific.com), an insurance-based nutrition practice serving South Lake Tahoe, CA; Minden, NV; and Ashland, OR. He holds the Interdisciplinary Specialist Certification in Obesity and Weight Management (CSOWM) from the Commission on Dietetic Registration. Virtual appointments are available via telehealth. For inquiries or appointments, visit MNTScientific.com, dial (530)429-7363, or email securecommunications@mntscientific.hush.com.