Association of dietary vitamin K and risk of coronary heart disease in middle-age adults: the Hordaland Health Study Cohort

Objective The role of vitamin K in the regulation of vascular calcification is established. However, the association of dietary vitamins K1 and K2 with risk of coronary heart disease (CHD) is inconclusive. Design Prospective cohort study. Setting We followed participants in the community-based Hordaland Health Study from 1997 - 1999 through 2009 to evaluate associations between intake of vitamin K and incident (new onset) CHD. Baseline diet was assessed by a past-year food frequency questionnaire. Energy-adjusted residuals of vitamin K1 and vitamin K2 intakes were categorised into quartiles. Participants 2987 Norwegian men and women, age 46–49 years. Methods Information on incident CHD events was obtained from the nationwide Cardiovascular Disease in Norway (CVDNOR) Project. Multivariable Cox regression estimated HRs and 95% CIs with test for linear trends across quartiles. Analyses were adjusted for age, sex, total energy intake, physical activity, smoking and education. A third model further adjusted K1 intake for energy-adjusted fibre and folate, while K2 intake was adjusted for energy-adjusted saturated fatty acids and calcium. Results During a median follow-up time of 11 years, we documented 112 incident CHD cases. In the adjusted analyses, there was no association between intake of vitamin K1 and CHD (HR Q4vsQ1 = 0.92 (95% CI 0.54 to 1.57), p for trend 0.64), while there was a lower risk of CHD associated with higher intake of energy-adjusted vitamin K2 (HR Q4vsQ1 = 0.52 (0.29 to 0.94), p for trend 0.03). Further adjustment for potential dietary confounders did not materially change the association for K1, while the association for K2 was slightly attenuated (HR Q4vsQ1 = 0.58 (0.28 to 1.19)). Conclusions A higher intake of vitamin K2 was associated with lower risk of CHD, while there was no association between intake of vitamin K1 and CHD. Trial registration number NCT03013725