Contribution of Vitamin D2 and D3 and Their Respective 25-Hydroxy Metabolites to the Total Vitamin D Content of Beef and Lamb

Background Red meat and meat products can contribute meaningfully to the mean daily intake of vitamin D. Beef and lamb can contain vitamin D3 and 25-hydroxyvitamin D3 [25(OH)D3] but also potentially vitamin D2 and 25-hydroxyvitamin D2 [25(OH)D2], all of which contribute to meat's vitamin D activity. Objectives We aimed to measure the vitamin D3, vitamin D2, 25(OH)D3, and 25(OH)D2 content of Irish beef and lamb. Methods Full striploin steaks (longissimus dorsi) (n = 39) from beef cattle slaughtered in winter, spring, summer, and autumn as well as lamb steaks (hind leg) from sheep slaughtered in autumn (n = 8) were sourced and homogenized. The contents of all 4 vitamin D-related compounds were analyzed using an LC-tandem MS method in conjunction with the National Institute of Standards and Technology's standard reference material no. 1546a-Meat Homogenate. The total vitamin D activity of meat was defined as: {vitamin D3 + [25(OH)D3 × 5] + vitamin D2 + [25(OH)D2 × 5]}. Results The median (IQR) total vitamin D activity of striploin beef steak (n = 39, irrespective of season) was 0.56 (0.37-0.91) μg/100 g. The content of all 4 vitamin D compounds in beef steak varied significantly (P < 0.0001) with season (n = 8-11/season group). Median total vitamin D activity of beef steak increased in a stepwise manner (P < 0.0001) from winter to the following autumn (increasing from 0.31 to 1.07 μg/100 g). The mean total vitamin D activity of lamb samples (n = 8) from autumn was 0.47 μg/100 g. Conclusions About one-third of the total vitamin D activity of Irish beef was attributable to its combined vitamin D2 and 25(OH)D2 content, estimates of which are largely or completely missed in food composition tables. There was significant seasonal variation in all 4 vitamin D compounds as well as in total vitamin D activity, which has implications for vitamin D nutrient claims for beef.