Recent evidence suggests a role of vitamin K beyond its traditional role in blood coagulation⁽Reference Booth¹⁾. An improved vitamin K status has been associated with an increase in childhood bone mineral content over time⁽Reference Van Summeren, Van Coeverden and Schurgers²⁾. The European Food Safety Authority (EFSA) has found insufficient evidence to set an Estimated Average Requirement (EAR) for vitamin K but has set an Adequate Intake (AI) of 1·0μg/kg bodyweight per day for all age and gender populations for vitamin K₁ only based on observed intakes in healthy populations⁽³⁾. The objective of this analysis was to estimate the intake and sources of vitamin K₁ in Irish teenagers aged 13–17 years using data collected from the National Teens’ Food Survey (NTFS) (www.iuna.net). A 7-day semi-weighed food record was used to estimate dietary intakes for 441 teenagers. The vitamin K₁ content of foods was primarily determined using data from the UK food composition tables (COFID)⁽⁴⁾. For certain foods where vitamin K₁ values were not available in COFID⁽⁴⁾, data from the US food composition tables⁽⁵⁾ and published papers were used to assign suitable values. The vitamin K₁ contents of composite dishes and retail products were calculated based on their ingredients. Body weight (kg) was measured in the participants’ homes by trained researchers. Usual intakes of vitamin K₁ were calculated via the NCI-method⁽Reference Tooze, Kipnis and Buckman⁶⁾ using SAS Enterprise Guide. Differences in vitamin K₁ intakes were assessed using a Kruskal-Wallis test (non-normal data) and a Wilcoxon two sample test for post-hoc analysis.

The mean daily intake (MDI) of vitamin K₁ was 55 μg/d in the total population (boys; 60 μg/d, girls; 50 μg/d). Adjusted for bodyweight, the MDI was 1 ·0 μg/kg/d for boys aged 13–14 years and 0·9 μg/kg/d for boys aged 15–17 years and girls (all ages). Boys aged 13–14 years had significantly higher intakes (μg/kg/d) (p < 0·001) than all other age and gender groups. ‘Vegetable and vegetable dishes’ was the highest contributor to vitamin K₁ intakes in the total population at 32%, of which 15% came from ‘green vegetables’. ‘Potatoes & potato products’, ‘meat and meat products’ and ‘butter, spreading fats & oils’ contributed 17, 13 and 8% of the MDI of vitamin K₁ in the total population, respectively. Vitamin K₁ intakes in Irish teenagers may be considered less than optimal as intakes are below observed AIs for each age/gender group examined with the exception of younger teenage boys. Further research is required to investigate the implications of lower vitamin K intakes in overall health.

This research was funded by the Department of Agriculture, Food and the Marine under the project ‘Development of biofortification approaches for enhanced vitamin K content of foods (15/F/670)’