BACKGROUND: More than one-fifth of the United Kingdom population has poor vitamin D status (serum 25-hydroxyvitamin D [25(OH)D] concentration <25 nmol/L), particularly individuals with low sun exposure or poor dietary intake. OBJECTIVE: We identified the fortification vehicle and concentration most likely to safely increase population vitamin D intakes and vitamin D status. DESIGN: Wheat flour and milk were identified as primary fortification vehicles for their universal consumption in population groups most at risk of vitamin D deficiency including children aged 18-36 mo, females aged 15-49 y, and adults aged ≥65 y. With the use of data from the first 2 y (2008-2010) of the National Diet and Nutrition Survey Rolling Program, we simulated the effect of fortifying wheat flour and milk with vitamin D on United Kingdom food consumption. Empirically derived equations for the relation between vitamin D intake and the serum 25(OH)D concentration were used to estimate the population serum 25(OH)D concentration for each fortification scenario. RESULTS: At a simulated fortification of 10 μg vitamin D/100 g wheat flour, the proportion of at-risk groups estimated to have vitamin D intakes below United Kingdom Reference Nutrient Intakes was reduced from 93% to 50%, with no individual exceeding the United Kingdom Tolerable Upper Intake Level; the 2.5th percentile of the population winter serum 25(OH)D concentration rose from 20 to 27 nmol/L after fortification. The simulation of the fortification of wheat flour at this concentration was more effective than that of the fortification of milk (at concentrations between 0.25 and 7 mg vitamin D/100 L milk) or of the fortification of milk and flour combined. CONCLUSION: To our knowledge, this study provides new evidence that vitamin D fortification of wheat flour could be a viable option for safely improving vitamin D intakes and the status of United Kingdom population groups at risk of deficiency without increasing risk of exceeding current reference thresholds.