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A randomized, controlled trial evaluating the efficacy of an online intervention targeting vitamin D intake, knowledge and status among young adults

Goodman, Samantha, Morrongiello, Barbara, Meckling, Kelly
The international journal of behavioral nutrition and physical activity 2016 v.13 no.1 pp. 116
analysis of variance, blood, bone density, cholecalciferol, education, food frequency questionnaires, food intake, gender, men, surveys, vitamin status, women, young adults, Ontario
BACKGROUND: Vitamin D plays a key role in bone health. Consuming adequate vitamin D during young adulthood is important due to the development of peak bone mass; however, many Canadian young adults do not meet vitamin D recommendations. This study aimed to improve knowledge, perceptions, dietary intake and blood concentrations of vitamin D among a sample of young adults. METHODS: Using a pre-post design, 90 Ontario adults (38 men, 52 women; 18–25 years), were randomly assigned to intervention or control groups. Participants completed a socio-demographic survey, pre-post food frequency questionnaire, and a vitamin D knowledge questionnaire (3 time-points). The intervention group watched a video, received online information and tracked intake of vitamin D using a mobile application for 12 weeks. A sub-sample of participants completed pre-post blood 25(OH)D₃ tests. Univariate ANOVA tested pre-post between-group differences in vitamin D intake and status. Repeated-measures ANOVA tested between-group differences in vitamin D knowledge and perceptions across 3 time-points. RESULTS: Mean vitamin D intake in the sample increased significantly from pre-test (M = 407, SD = 460 IU) to post-test (M = 619, SD = 655 IU), t(88) = 5.37, p < 0.001. Mean intake increased significantly more in the intervention than control group after controlling for gender and education, F(1, 85) = 4.09, p = 0.046. Mean blood vitamin D₃ was significantly higher among non-Caucasian than Caucasian participants at baseline, t(56.7) = 3.49, p = 0.001. Mean blood vitamin D₃ increased significantly from pre-test (M = 28, SD = 16 nmol/L) to post-test (M = 43, SD = 29 nmol/L), t(53) = 11.36, p < 0.001, but did not differ significantly between groups. The increase in vitamin D knowledge from time 1–3 was significantly higher in the intervention than control group (t(88) = 2.26, p = 0.03). The intervention group (M = 3.52, SE = 0.13) had higher overall perceived importance of vitamin D supplementation than the control (M = 3.16, SE = 0.12), F(1, 88) = 4.38, p = 0.04, ηₚ² = 0.05. CONCLUSIONS: Although recommendations suggest blood 25(OH)D₃ concentrations of ≥50-75 nmol/L, vitamin D status was below national recommendations. While participating in an intervention did not improve vitamin D status, it led to increased vitamin D intake, knowledge and perceived importance of supplementation. TRIAL REGISTRATION: registration #: NCT02118129 .