The diet’s content of vitamin K1 and vitamin K2 lowers the risk of atherosclerosis and cardiovascular disease by way of several mechanisms, yet there are relatively few studies that show the relation. In a Danish study that is published in Journal of the American Heart Association, scientists looked closer at how the content of the two forms vitamin K in the diet affect the risk of hospitalization linked to atherosclerosis and cardiovascular disease. So how does vitamin K counteract atherosclerosis and how much of the nutrient do we need?
Atherosclerosis is caused by deposits of calcium, oxidized LDL cholesterol, and fat on the inside of the arteries, causing a thickening of the vessel walls and coronary restriction. As time goes by, the blood supply is impaired and blood platelets are more likely to aggregate and form clots. These changes are typically seen in the coronary arteries of the heart and in the arteries of the brain, kidneys, and legs.
Atherosclerosis remains the leading cause of death in the world, despite updated guidelines for healthy living and the use of medication intended to lower the risk of cardiovascular disease. Heart disease caused by atherosclerosis is also known as atherosclerotic cardiovascular disease (ASCVD) and there are different causes as shown below:
1) Inflammation and oxidative stress
Chronic inflammation, the common thread in many chronic diseases, sets the stage for oxidative stress where free radicals attack our cholesterol, causing this otherwise essential compound to become rancid. Rancid (oxidized) cholesterol is not of an value to the body and is consumed by white blood cells and embedded in the arterial walls in the form of cholesterol-loaded foam cells.
2) Metabolic syndrome and type 2 diabetes
Metabolic syndrome causes the liver to produce too many lipids, especially from sources like carbohydrate and fructose. Metabolic syndrome is characterized by insulin resistance, hypertension, elevated cholesterol/dyslipidemia, and abdominal obesity (apple-shaped body). Metabolic syndrome is an early stage of type 2 diabetes.
3) Impaired homeostasis
In biology, homeostasis is the dynamic equilibrium that is designed to ensure that the internal environment is kept within tightly controlled boundaries. Impaired homeostasis can occur in several systems and organs.
This condition features deposits of calcium in the arteries as a result of incorrect calcium distribution. We have around 99 percent of our calcium in hard tissues like bones and teeth, while only one percent of our calcium is used to control metabolic functions in soft tissues.
Facts about vitamin K
Vitamin K is found in two different forms that have widely different functions.
Vitamin K1 (phylloquinone) is mainly found in leafy, dark greens such as parsley, spinach, cabbage, and beans. We only absorb around 10% of the vitamin K1 from our diet. A well-functioning intestinal flora is able to convert vitamin K1 into vitamin K2 but often only in limited quantities. Vitamin K1 is important for blood coagulation.
Vitamin K2 (menaquinone K4 - K10) is only fond in fermented foods like sauerkraut, kefir, and soft cheeses such as brie and Natto, a Japanese soy product. Here, the vitamin is made by bacteria as a natural part of the fermentation process.
Vitamin K2 activates matrix Gla protein (MGP), a protein found in or blood vessels. MGP binds calcium and removes it from the arteries. Furthermore, vitamin K2 activates osteocalcin, a protein that works by embedding calcium in our bones. It is through these two mechanisms that vitamin K2 can counteract atherosclerosis and osteoporosis.
Studies have shown that there is an inverse relation between biomarkers for vitamin K and the risk of developing atherosclerosis. The study also shows that vitamin K supplements are able to increase levels of circulation markers. It appears that vitamin K is able to prevent atherosclerosis, although studies of vitamin K1 and atherosclerosis are insufficient. A Dutch population study shows that high intake of dietary vitamin K2 lowers the risk of atherosclerosis, but similar results have not been seen with studies of other populations. Two recent meta-analyses have demonstrated that lack of vitamin K increases the risk of cardiovascular disease and mortality, but more studies are needed to confirm these observations and to understand the biochemical effect of vitamin K.
The new Danish study confirms vitamin K’s role in good cardiovascular health
In the new Danish population study, the scientists looked closer at participants who did not suffer from cardiovascular disease at baseline. They were recruited from a large Danish cohort study named “Kost, Kræft og Helbred” (Diet, Cancer, and Health). All participants were asked to fill in questionnaires with information about their diet. The scientists used these questionnaires to assess the participants’ intake of vitamin K1 and vitamin K2. In addition, the participants were monitored to see who were eventually hospitalized with atherosclerotic cardiovascular diseases such as ischemic heart disease, ischemic stroke, or peripheral artery disease (PAD).
The study included 53,372 Danes with an average age of 56 years. Over a follow-up period of 21 years, 8,726 of the participants were admitted to hospital with the mentioned cardiovascular diseases. It turned out that the participants with the highest intake of vitamin K1 were 21 percent less likely to be hospitalized with cardiovascular disease compared to the participants with the lowest intake of vitamin K1. Similarly, those with the highest intake of vitamin K2 had a 14 percent lower risk of being hospitalized with cardiovascular disorders compared with those who got the least vitamin K2. Based on their findings, the scientists concluded that a diet rich in vitamins K1 and K2 lowers the risk of atherosclerotic cardiovascular disease. What is more, a diet with adequate quantities of these two K vitamins also provides dietary fiber and other essential nutrients. The study is published in Journal of the American Heart Association
How much vitamin K do we need?
The reference intake (RI) level for vitamin K1 for adults is 75 micrograms, whereas no RI level has been established for vitamin K2. Although the optimal level for vitamin K2 has not yet been established, various other studies suggest that we can easily consume comparatively high doses in the range of 75-180 micrograms/day without any problems.
Vitamin K2 is found in different forms. The form called K2 MK-7 stays longer in the body and has a better effect on calcium distribution in the different tissues. This is why K2 is recommended for supplementation.
Patients who take blood-thinning medication such as Marevan (a vitamin K antagonist) need an evenly distributed intake of dietary vitamin K and should refrain from taking vitamin K in supplement form.
Modern diets and medicine result in vitamin K deficiencies
Although vitamin K deficiency is relatively rare, some research suggests otherwise. Besides being a result of poor dietary habits, vitamin K deficiency can also occur in the wake of poor intestinal flora and prolonged use of different types of medicine such as antibiotics, antacids, acetylsalicylic acid, cholesterol-lowering drugs, and preparations with warfarin and dicumarol that are vitamin K antagonists used to prevent blood clots.
Jaime W. Bellinge et al. Vitamin K Intake and Atherosclerotic Cardiovascular Disease in the Danish Diet Cancer and Health Study. Journal of the American Heart Association. 7 Aug. 2021
Stephen Daniells. New Study show importance of vitamin K for vascular function. Nutraingredients.com 2020
S. Thamratnopkoon et al. Correlation of Plasma Desphosporylated Uncarboxylated matrix Gla Protein with Vascular Calcification and Stiffness in Chronic Kidney Disease. Nephron. 2017 Published online.
M. Sardana et al. Inactive Matrix Gla-Protein and Arterial stiffness in Type 2 diabetes Mellitus. American Journal of Hypertension 2016
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