Is Vitamin D Fortification of Dairy Products Effective for Improving Vitamin D Status? A Systematic Review and Meta-Analysis of Randomised Controlled Trials.

Background/objectives: Given the suboptimal vitamin D intake and status among the United Kingdom population, the Scientific Advisory Committee on Nutrition is seeking suitable food vehicles for vitamin D fortification. Thus, this study aimed to examine the efficacy of vitamin D-fortified dairy products in improving serum 25-hydroxyvitamin D [25(OH)D] concentration using data from randomised controlled trials (RCTs).

Methods

PubMed, Embase, and Web of Science were searched from inception until October 2024. Studies were included if they were RCTs with intervention groups administered vitamin D-fortified dairy products and control groups administered unfortified dairy products, as well as examining the effects on serum 25(OH)D concentration.

Results

There were 35 RCTs eligible for inclusion, involving 4965 participants (intervention: 2526; control: 2439). The results showed that serum 25(OH)D concentrations were significantly increased by vitamin D3-fortified milk/milk powder (n = 15, mean difference (MD): 18.31 nmol/L, 95% confidence interval (CI): 13.30-23.33 nmol/L, I2 = 95%), vitamin D3-fortified yoghurt/yoghurt drinks (n = 11, MD: 26.22 nmol/L, 95% CI: 18.67-33.77 nmol/L, I2 = 97%), vitamin D2-fortified milk/milk powder (n = 3, MD: 11.61 nmol/L, 95% CI: 9.31-13.91 nmol/L, I2 = 0%), vitamin D-fortified (type not specified) milk/milk powder (n = 8, MD: 13.59 nmol/L, 95% CI: 8.54-18.64, I2 = 98%), and vitamin D-fortified (type not specified) yoghurt/yoghurt drinks (n = 4, MD: 27.74 nmol/L, 95% CI: 16.83-38.64 nmol/L, I2 = 91%), but insignificantly increased by vitamin D3-fortified cheese (n = 5, MD: 16.78 nmol/L, 95% CI: -3.61-37.16, I2 = 99%). However, the results of vitamin D3-fortified cheese became significant when leave-one-out analysis was performed by omitting one RCT (MD: 24.13 nmol/L, 95% CI: 4.69-43.58, I2 = 90%).

Conclusions

These findings provide evidence that vitamin D-fortified dairy products have the potential to improve serum 25(OH)D concentrations in populations.