Kale, parsley, broccoli, and spinach: according to new research, these leafy green vegetables may hold even more health benefits than previously thought, as vitamin K - found in abundance in all four - may contribute to a healthy heart.

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Leafy greens, such as broccoli and kale, are great sources of vitamin K-1, and they may help to keep the heart healthy.

A new study published in The Journal of Nutrition examines the link between vitamin K levels and heart structure and functioning in young people.

Vitamin K plays a key role in blood coagulation and bone health. Deficient levels of the vitamin raise the risk of hemorrhage, osteoporosis, and bone fractures.

In its dietary form, vitamin K is known as phylloquinone, or vitamin K-1. This is abundantly found in leafy green vegetables such as kale, parsley, broccoli, spinach, iceberg lettuce, and cabbage.

The new research suggests that insufficient levels of the vitamin may affect the structure of the heart, leading to a condition called left ventricular hypertrophy (LVH).

The left ventricle is the heart's major pumping chamber, and in LVH, this chamber is enlarged to an unhealthy degree. As the authors of the new study explain, a larger heart can malfunction with time, becoming less effective at pumping blood.

LVH tends to affect adults, but the researchers decided to study this heart structure in young people because cardiac abnormalities that begin in childhood tend to predict the risk of cardiovascular disease in adulthood.

To the best of the authors' knowledge, this is the first time that a study has examined links between vitamin K levels and heart structure in teenagers.

Mary K. Douthit and Mary Ellen Fain, both of the Georgia Prevention Institute at Augusta University, are the study's co-first authors. Dr. Norman Pollock, a bone biologist at the same institute, is the study's corresponding author.

Low vitamin K-1 intake correlates with LVH

Douthit and colleagues examined 766 healthy adolescents aged between 14 and 18. Half of the participants were male and half were female. Half of the participants were also black Americans.

The researchers assessed the diet and physical activity habits of these teenagers over a period of 7 days, using the participants' self-reporting and accelerometry devices. Left ventricular structure and functioning were assessed using echocardiography.

Overall, the study found that the teenagers who consumed the least amount of vitamin K-1 had considerably greater left ventricles compared with those who consumed sufficient amounts of the vitamin.

The researchers divided the results into tertiles, or thirds, of vitamin K-1 intake. They found, "The prevalence of [LVH] progressively decreased across tertiles of phylloquinone intake."

In other words, the more vitamin K-1 the teenagers consumed, the less likely they were to develop LVH.

Dr. Pollock spoke to Medical News Today about the findings. He said, "[Teens] consuming 42 micrograms per day or less of vitamin K were more than three times [more] likely to have left ventricular hypertrophy than those consuming 90 micrograms per day or more."

"Strikingly," Dr. Pollock added, "this relationship persisted even after taking into account potentially confounding factors such as age, sex, race, pubertal stage, blood pressure, body composition, physical activity, and other factors of dietary intake."

Around 10 percent of the teenagers had LVH to some degree, as determined by measurements of the overall size of the ventricle and the thickness of its walls.

Clinical implications of the findings

The findings, the authors write, help them to "clarify the importance of phylloquinone intake to cardiovascular development."

Speaking to MNT about the clinical implications of the study, Dr. Pollock said that "cardiovascular disease risk factors have been shown to track during childhood and later life and may be affected by dietary intake, [so] it is of clinical relevance to study dietary determinants of cardiovascular development."

"Our observational data suggest that greater vitamin K consumption may favorably influence subclinical markers of cardiac structure and function in a population of U.S. adolescents." 

Dr. Norman Pollock

The study authors write that although further research is now needed, the new findings could ultimately "lead to phylloquinone interventions in childhood aimed to improve cardiovascular development and to reduce the subsequent risk of [cardiovascular disease]."

In fact, Dr. Pollock is currently the lead investigator in four vitamin K trials aiming "to determine the effect of vitamin K supplementation on risk markers of cardiovascular disease and diabetes."