Secular trends of vitamin D and calcium intake and their circulating levels in US adults from 2007 to 2018

Yongliang Du ^1,2 Chao Ma ² Zhaoyue Shang ² Xiaohua Zhang ² Yanlin Duan ² Liu Tong ² Yang Yu ² Shuman Yang ^1,2*

• ¹ Department of Endocrinology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, Liaoning, China
• ² Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, Changchun, Jilin, China

Background: Few studies have examined the secular trends of total calcium and vitamin D intake and their circulating levels together among adults in the United States (US). Understanding the trends of these nutrients may be useful for refining existing nutrition policy and guidelines. Calcium and vitamin D intake including their supplements were the average of two 24-hour recalls. Serum calcium and serum 25-hydroxyvitamin D [25(OH)D] were measured using established methods. Weighted regression was used to test trends in calcium and vitamin D intake, and serum total calcium and 25(OH)D levels.Results: This research included 16,751 participants, including 9,046 males and 7705 females. Serum total calcium significantly decreased with survey years from 2007 to 2018 (9.42 to 9.31 mg/dL) (P trend <0.001). Calcium intake declined from 2009 to 2018 (1070 to 1010 mg/day; P trend <0.001). In contrast, vitamin D intake and serum 25(OH)D increased with survey years (5.8 to 11.0 mcg/day and 65.6 to 68.5 nmol/L, respectively; all P trend <0.001). The trends in calcium intake vs. serum total calcium (P trend interaction =0.267), and vitamin D intake vs. serum 25(OH)D with survey years were comparable (P trend interaction =0.190). Inadequate vitamin D intake decreased with survey years (86.0% to 80.2%; P trend=0.002). Moderate vitamin D deficiency (22.3% to 21.5%; P trend= 0.043), but not severe vitamin D deficiency (3.3% to 2.9%; P trend= 0.119), also declined with calendar years.From 2007 to 2018, US adults showed a decrease in serum total calcium, and an increase in serum 25(OH)D levels. Both trends were partly due to declined calcium and increased vitamin D intake.This research investigated the secular trends (2007-2018) of total vitamin D and calcium intake and their circulating levels among US adults. There was a decrease in circulating total calcium and an increase in circulating vitamin D levels. Both trends were partly due to declined calcium and increased vitamin D intake. Understanding the trends of these nutrients may be useful for refining existing nutrition policy and guidelines.