Global prevalence of diet low in calcium and the disease burden: results from the Global Burden of Disease Study 2019

Calcium is an essential mineral for physiological functions, particularly skeletal health, with about 99% of body calcium stored in bone. Inadequate calcium intake is linked to multiple diseases including osteoporosis, fractures, cardiovascular disease, body fat mass changes, and colorectal cancer. Dietary intake is the major calcium source, but inadequacy can arise from income status, dietary habits, and food diversity. Earlier global estimates suggested around 3.5 billion people were at risk of dietary calcium deficiency in 2011, but up-to-date, country-specific prevalence and temporal trends of diet low in calcium (DLC), and associated disease burden, remained unclear. Moreover, disease burden estimates attributable to DLC have been limited, especially given sparse intake data in many developing countries. This study aims to provide a comprehensive assessment of the global, regional, and national prevalence and health burden related to DLC from 1990 to 2019 by age, sex, and sociodemographic index (SDI), using GBD 2019 data, to inform policy and nutrition management.

Design and data source: Cross-sectional analysis using Global Burden of Disease Study 2019 (GBD 2019) estimates from the Institute for Health Metrics and Evaluation for 204 countries and territories, 21 GBD regions, and globally, spanning 1990–2019 and stratified by location, year, age, sex, and sociodemographic index (SDI). Definition of exposure: Diet low in calcium (DLC) is a GBD dietary risk factor defined as average daily calcium consumption below 1.06–1.10 g/day from all sources (e.g., milk, yogurt, cheese). Intake data sources included nationally and sub-nationally representative nutrition surveys, household budget surveys, Euromonitor national sales accounts, and FAO Supply and Utilization Accounts. Exposure metric: Summary exposure value (SEV), a relative risk–weighted prevalence metric (0–100%), was used to represent DLC prevalence; higher SEV indicates higher population exposure. Outcome and burden estimation: DLC is linked in GBD 2019 to colorectal cancer as the sole risk–outcome pair used for attributable burden estimation. Disease burden was quantified as disability-adjusted life years (DALYs), the sum of years of life lost and years lived with disability. Attributable burden reflects DLC-induced colorectal cancer only. Modeling: Estimates were generated using DisMod-MR 2.1, a Bayesian meta-regression tool that integrates diverse data sources. Outputs include age-standardized rates (ASR) with 95% uncertainty intervals (UI). Sociodemographic index: SDI is the geometric mean (0–1, scaled to 1–100) of education (15+ years), total fertility rate under 25, and lag-distributed income per capita, used to contextualize sociodemographic development. Statistical analysis: Age-standardized SEV and age-standardized DALY rates (ASDR) with 95% UI were reported. Temporal trends (1990–2019) were evaluated via estimated annual percentage change (EAPC) derived from linear regression of log10(ASR) on calendar year: y = a + bx + e; EAPC = 100 × (10^b − 1), with 95% confidence intervals (CI). Spearman rank-order correlation assessed associations of SEV and ASDR with SDI. Analyses and visualization were performed in R 4.4.3. Data pertain to individuals aged 30 years and older for SEV and DALY by age.

- Global prevalence of DLC: In 2019, global age-standardized SEV was 46% (95% UI, 35.9–60.3) with a decreasing trend from 1990–2019 (EAPC, -0.47; 95% CI, -0.5 to -0.43). - Regional prevalence: Highest SEV in 2019 in Central Sub-Saharan Africa 88.1 (95% UI, 82.3–94.6), Southeast Asia 83.4 (75.3–92.7), and Oceania 79.9 (71–90.6). SEV was consistently higher in males than females across regions. Oceania showed increasing SEV trends for both sexes (both sexes EAPC 0.16; 95% CI, 0.12–0.19). - Country-level prevalence: Highest SEV in Zambia (96; 95% UI, 95–97), followed by Liberia, Zimbabwe, and the Democratic Republic of the Congo. While most countries had decreasing SEV, 26 countries increased, led by United Arab Emirates (EAPC 2.03; 95% CI, 1.86–2.21), New Zealand, Japan, and France. - Global burden: In 2019, DLC-attributable DALYs (via colorectal cancer) were 3.1446 million (95% UI, 2.248–4.2597 million). Global ASDR was 38.2 per 100,000 (95% UI, 27.2–51.8) and accounted for 12.91% (95% UI, 9.31–17.46) of total colorectal cancer DALY burden for both sexes; higher in males (13.55%; 95% UI, 9.83–18.23) than females (12.05%; 95% UI, 8.68–16.38). - Temporal trend of burden: Global ASDR remained overall unchanged (EAPC, -0.03; 95% CI, -0.12 to 0.07), but increased in multiple regions, including Sub-Saharan Africa, Latin America, South and Southeast Asia, and Oceania. At least 80 of 204 countries showed increasing ASDR; largest increases in Lesotho (EAPC 2.62; 95% CI, 2.38–2.87), Viet Nam, Mozambique, and Bulgaria. - Countries with highest ASDR: Viet Nam and Palestine exceeded 100 per 100,000; other high-ASDR countries included Philippines, Seychelles, Malaysia, Indonesia, Cambodia, Zambia, and Laos (primarily in Southeast Asia and Southern Africa). - Sex differences: Males had higher SEV and ASDR than females in all regions and years. Global male ASDR increased (EAPC 0.27; 95% CI, 0.15–0.40), while female ASDR decreased over 1990–2019. - SDI associations: Strong inverse correlation between SDI and SEV (rho = -0.823; P < 0.001) and moderate inverse correlation between SDI and ASDR (rho = -0.433; P < 0.001). Low- and low-middle-SDI regions showed increasing ASDR trends; for low SDI, EAPC for ASDR was 0.49 (95% CI, 0.42–0.56) overall (male 0.82; female 0.14). High- and middle-SDI regions generally showed declining ASDR. - Age patterns: SEV decreased with age to about 70 years, slightly rose to ~85, then decreased; ASDR increased steadily with age, peaking around 90 years for both sexes. - Geographic patterns: High prevalence and increasing burden concentrated in parts of Africa, Southeast Asia, and some countries in South America; some high-income countries (e.g., France, Japan, New Zealand) showed increasing SEV despite lower levels than low-SDI regions.

The study reveals a global decline in DLC prevalence since 1990, but an overall stable global burden due to DLC-attributable colorectal cancer, with notable increases in many low- and middle-SDI countries. Differences between high- and low-income settings likely reflect disparities in access to calcium-rich foods, dietary habits, food diversity, and fortification practices. Low dairy availability and low micronutrient density complementary foods in parts of Africa and Southeast Asia contribute to higher exposure, whereas food fortification and diverse diets in high-income countries mitigate risk. Nonetheless, subgroups in high-income countries (e.g., adolescents, postmenopausal or athletic women, vegans) may still be at risk, explaining rising SEV in some developed countries. The consistently higher male SEV and ASDR may relate to dietary patterns and supplement use differences, though evidence is mixed across countries. The divergence between decreasing SEV and increasing ASDR with age reflects that burden estimates in GBD 2019 include only colorectal cancer as the outcome for DLC; colorectal cancer risk and burden rise with age, inflating ASDR among older adults even when exposure prevalence declines. The strong inverse associations of SDI with both exposure and burden highlight the need for targeted interventions in low-SDI settings. Overall, the findings emphasize the importance of improving calcium intake through diet diversification, fortification, supplementation where appropriate, and targeted public health strategies, particularly in regions with increasing burden and among higher-risk demographic groups.

The prevalence of diet low in calcium has decreased worldwide and in most countries, yet the DLC-attributable colorectal cancer burden has increased in over 80 countries. Low-SDI countries and males are more prone to DLC exposure and higher disease burden, and older adults experience higher disability rates. Effective measures—including public education, improved access to calcium-rich and fortified foods, and appropriate supplementation—are needed to mitigate DLC-related health challenges.

- Attributable burden was estimated only for colorectal cancer due to GBD 2019 risk–outcome pair definitions, likely underestimating total DLC-related burden (e.g., osteoporosis, cardiovascular disease not included). - Data pertain to individuals aged 30 years and older; prevalence and burden in younger populations, particularly adolescents, remain unclear. - Inherent GBD limitations include variability in raw data availability and quality across countries, wide uncertainty intervals in some estimates, and reliance on Bayesian modeling for data-sparse settings, potentially introducing bias from actual values.