Associations between vitamin K status and skeletal and cardio-metabolic health indices in 18–64-year-old Irish adults

Abstract

A high proportion of Irish men and women have mean daily vitamin K intakes which are likely inadequate. For example, we had previously shown that 52 % of a nationally representative sample of the adult Irish population from 1997-1999(1) had vitamin K1 intakes below the UK recommended 1 mu g/kg body weight(2), and 17 % and 27 % of men and women, respectively, met the current US adequate intakes for vitamin K.(3) This may have consequences for vitamin K status and associated skeletal and non-skeletal health effects. This analysis explored associations between biochemical measures of vitamin K status and a biomarker of bone turnover and with a metabolic syndrome (MetS) risk score, and its component risk factors as defined by the International Diabetes Federation(4). Data [dietary, lifestyle and risk factor] and serum were accessed from the most recent nationally representative sample of Irish adults (National Adult Nutrition Survey 2008-2010) (www.iuna.net). Vitamin K status measures (undercarboxylated osteo-calcin [GLU], carboxylated osteocalcin [GLA], and % osteocalcin undercarboxylated [%ucOC]) and carboxy-terminal collagen crosslinks (CTx; bone resorption marker) were measured in 692 adults by immunoassay. Serum %ucOC was a significant (P < 0.0001) positive determinant of serum CTx, adjusting for confounders (model explained 48 % variability in serum CTx). Associations with MetS risk factors were driven by age. Surprisingly, in younger adults (<50y), serum %ucOC was significantly (P < 0.05) lower [Median (IQR)38.8 (27.5, 52.5) %] in those with central obesity and an additional MetS risk compared to those with no MetS risk[42.5 (30.4, 59.6) %], accounting for sex, smoking and vitamin K intake. The pathogenesis for MetS and each of its components is complex and poorly understood. In addition to its role in skeletal health, vitamin K status may influence specific cardio-metabolic risk factors, however, further investigation is warranted to establish a causal relationship.