Teenagers who consumed low intakes of vitamin K1, found in leafy green vegetables (such as kale and spinach), showed more than three times higher risk of left ventricular hypertrophy (LVH), found researchers from Augusta University.
LVH is a condition where the major pumping chamber of the heart becomes enlarged, wall thickness increases and the amount of blood pumped out (ejection fraction) is decreased.
“The prevalence of LV hypertrophy progressively decreased across tertiles of phylloquinone intake,” observed corresponding author Dr. Norman Pollock. "Those who consumed less had more risk."
The study, published in The Journal of Nutrition, is the first to investigate possible links between vitamin K1 intake and heart structure and function within an adolescent population.
LVH is more widely known to occur in adults whose heart muscles have become less effective due to a long history of high blood pressure.
The findings suggest that LV structure changes can start in adolescence and may enable interventions to prevent cardiovascular (CV) events in later life. Although further research is needed, ensuring adequate vitamin K intake in early life may be important in lowering long-term CV risk.
“This could eventually lead to phylloquinone interventions in childhood aimed to improve cardiovascular development and to reduce the subsequent risk of CV disease,” concluded the team.
Study details
The study assessed phylloquinone intake of 766 teenagers aged 14-18 years through dietary recall. The scientists measured aspects of LV structure and function using echocardiography. They calculated associations between the LV structure and function variables and the odds risk of LV hypertrophy across tertiles of phylloquinone intake.
After adjusting for multiple confounding variables, the researchers found that teenagers who consumed less than 42 micrograms/ day (ug/d) of phylloquinone had a 3.3 greater risk of LVH than those consuming more than 90 ug/d.
They also found significantly lower LV mass index and wall thickness in the highest tertile of vitamin K1 intake. Additionally, two measures of LV function were significantly poorer in the lower tertile intake group.
Only 25% of the study participants met the Adequate Intake level of 75 ug/d (recommended by the U.S. Food and Nutrition Board of the Institute of Medicine).
"They had higher levels relative to the other kids," commented Mary Ellen Fain, co-first author. "But even at that age, it seemed to make a difference in their hearts."
Study limitations
As the study design was cross-sectional, the team could not conclude a causative effect.
“We cannot be certain that phylloquinone intake has a direct effect on cardiac structure and function,” they acknowledged.
Additionally, the lack of reliable biomarkers for circulating vitamin K1 prevented the researchers from assessing whether better vitamin K1 status (reflective of higher phylloquinone intake) would have a beneficial effect on LV structure and function.
Source: The Journal of Nutrition
Published inline ahead of print. DOI: 10.3945/jn.117.253666
“Phylloquinone Intake Is Associated with Cardiac Structure and Function in Adolescents"
Authors: Mary K Douthit, Mary Ellen Fain, Norman K Pollock et al