Cardiovascular disease (CVD) continues to be the number one cause of death worldwide, with its impact escalating in aging populations. Although medical interventions have significantly advanced to lower risk, an expanding amount of research emphasizes the role of dietary components in influencing cardiovascular outcomes. Of these, vitamin K₁ (phylloquinone), which is present abundantly in leafy green vegetables, has appeared as a salient, yet overlooked nutrient for cardiovascular well-being.A recent longitudinal study that appeared in The American Journal of Clinical Nutrition (2025) shed new light on this relationship, the sweet-sour relationship between leafy greens and our taste buds. The researchers observed 1,435 community-living women aged more than 70 for over 14 years to assess the effect of sustained vitamin K₁ consumption on vascular morphology and cardiovascular death. The results are both interesting and of clinical significance.
Vitamin K₁ and vascular health
Vitamin K₁ has an important function in the activation of matrix GLA protein (MGP), an important inhibitor of vascular calcification. In the absence of the very essential nutrient vitamin K₁, MGP is inactive, and calcium deposits in arterial walls lead to stiffness and atherosclerotic plaque formation. This action has been understood to be at the center of both coronary artery disease and cerebrovascular diseases, such as stroke.
Vitamin K₁ is also involved in:
- Modulating inflammatory reactions that enhance vascular injury
- Facilitating coagulation homeostasis
- Interacting with bone metabolism, which is more and more regarded as connected to cardiovascular risk through the regulation of calcium
The study: Lower Arterial thickening and mortality
In the above-mentioned study, volunteers were divided into quartiles based on their dietary vitamin K₁ consumption. Subjects in the upper intake quartile (~120 μg/day) had:
- A 5.6% smaller carotid intima-media thickness (IMT), a well-established marker of subclinical atherosclerosis, than those in the lowest quartile
- A 43% reduced risk of cardiovascular disease death, adjusted for variables such as age, BMI, physical activity, medication use, and smoking status
These results are consistent with and an extension of previous epidemiological evidence, e.g., the Danish Diet, Cancer, and Health Study, which reported reductions in cardiovascular events and hospitalization similar to those in this population with high dietary intake of vitamin K₁.
Public health implications
The existing Recommended Daily Intake (RDI) of vitamin K₁ for adult women is 90 μg/day. Nonetheless, this recommendation is mainly focused on bodily needs for proper blood clotting and does not include protection for the vascular system. The new evidence indicates that intakes around 120 μg/day, something that can be easily obtained through 1 to 1.5 cups of leafy greens on a daily basis, might be associated with more extensive systemic benefits.
The leading food sources for vitamin K₁ are:
- Kale (~531 μg per cooked cup)
- Spinach (~889 μg per cooked cup)
- Broccoli (~110 μg per cooked cup)
- Swiss chard, romaine lettuce, and Brussels sprouts can also be incorporated into our daily leafy green intake.
Interestingly, vitamin K₁ is fat-soluble, and therefore, taking it with a food source of dietary fat (e.g., olive oil, avocado) increases absorption.
Cautions before incorporating K1 in the diet
Increasing vitamin K₁ intake is generally favorable to most, but persons taking vitamin K antagonists (e.g., warfarin) should discuss any drastic changes with their healthcare provider, as variation in vitamin K₁ affects the efficacy of drugs.In addition to its many benefits, despite being observational in design, the consistency and reliability of these observations across groups are compelling enough to merit serious consideration. To truly understand, randomized controlled trials (RCTs) must be undertaken to establish causality and investigate potential synergistic interactions with other micronutrients.