Dose-Response Effect of Consuming Commercially Available Eggs on Wintertime Serum 25-Hydroxyvitamin D Concentrations in Young Australian Adults: a 12-Week Randomized Controlled Trial

Background Vitamin D deficiency is a common health concern during winter. Eggs are one of the few rich dietary sources of vitamin D, containing cholecalciferol (vitamin D-3) and 25-hydroxyvitamin D-3 [25(OH)D-3], with the latter reported to be 5 times more potent at increasing serum 25(OH)D concentrations, the major circulating form of vitamin D. However, whether there is an optimal dose of eggs to increase or maintain 25(OH)D concentrations during wintertime is not known. Objectives To evaluate the dose-response effect of consuming 2, 7, or 12 commercially available eggs per week on serum 25(OH)D concentrations during the autumn-winter months in young adults. Secondary aims were to investigate changes in serum lipids, and the feasibility (adherence) and acceptability to consuming the eggs. Methods In a 12-wk randomized controlled trial, 51 adults aged 25-40 y were randomly assigned to consume 2 eggs/wk (control, n = 17), 7 eggs/wk (n = 17), or 12 eggs/wk (n = 17). Change in serum 25(OH)D was the primary outcome as assessed by LC/MS/MS. Serum lipids were assessed using standard techniques, and acceptability to consuming the eggs was assessed via a questionnaire. Results Forty-two (82%) participants completed the study. Mean adherence to the eggs was 83% for controls, 86% for 7 eggs/wk, and 83% for 12 eggs/wk. Mean serum 25(OH)D concentrations did not change significantly in either the 7-eggs/wk (-8.3 nmol/L; 95% CI: -17.0, 0.4 nmol/L) or 12-eggs/wk (-7.2 nmol/L; 95% CI: -18.6, 4.3 nmol/L) groups, but decreased by 28.6 nmol/L (95% CI: -38.1, -18.9 nmol/L) in controls, which led to a significant (P = 0.003) between-group difference for the change after 12 wk. Serum lipids did not differ between the groups, and acceptability profiles to consuming the eggs were positive and similar for all 3 groups. Conclusions Consuming 7 commercially available eggs per week for 12 wk was effective for attenuating the wintertime decline in circulating vitamin D concentrations in young Australian adults, with 12 eggs/wk not providing any additional benefits.