Vitamin K Deficiency: A Risk Factor for Heart Disease?
The role of vitamin K in heart health has been highlighted time and again over the years.
Although perhaps more well-known for its effect on bones, via its inhibition of arterial calcification, a growing body of research puts vitamin K alongside omega-3 fatty acids when it comes to maintaining optimum cardiovascular health.
In this blog we’ll attempt to summarise some major studies published in the last decade, leaving you in no doubt as to the efficacy of this most invaluable nutrient.
Vitamin K and Blood Clotting
Like calcium, vitamin K helps with proper blood clotting. It does so by activating coagulation factors, which is why people taking blood-thinning medications such as Warfarin are warned against supplemental vitamin K.
To put it simply, blood is unable to clot without adequate vitamin K and uncontrolled bleeding is the consequence.
In spite of its importance, vitamin K is not talked about anywhere near as much as other fat-soluble vitamins like D and A. In fact, many people will only really hear about it when they’re told to stay away from it because of potential pharmaceutical interactions.
This might, in effect, convince some that vitamin K is not so essential at all. This couldn’t be farther from the truth.
Abundant in leafy green vegetables such as Brussels sprouts and broccoli, vitamin K is very much a health-promoting nutrient needed for strong bones, proper wound healing and, according to an expanding body of research, peak cardiovascular health.
Blood clotting is but one small part of the equation.
Vitamin K and Heart Disease
Vitamin K’s effect on heart disease risk, and in vascular health generally, is rather simply explained with reference to its relationship to calcium.
Calcium is of course synonymous with the status of bones and teeth, but few people appreciate that vitamin K is the nutrient which, by activating the heart-protective MGP protein, directs calcium where it needs to go: to bones and teeth rather than arteries and blood vessels, where it can heighten the risk of cardiovascular problems such as atherosclerosis.
Healthy, flexible arteries will not remain as such if calcium deposits in the vessel walls and MGP is the most powerful natural inhibitor of calcification currently known.
This was born out by the oft-cited 2004 Rotterdam study, which sought to determine to what extent dietary intake of vitamin K was related to aortic calcification and coronary heart disease.
The dietary habits of 4,807 subjects were analysed, with adjustments made for age, gender, BMI, education and other relevant factors.
It was found that the relative risk of CHD mortality was statistically reduced among those consuming at least 32 mcg per day of vitamin K2; intake was also inversely related to all-cause mortality and severe aortic calcification.
The numbers were not insignificant either; a 50% reduced risk of arterial calcification, a 50% reduced cardiovascular risk and a 25% reduced all-cause mortality risk.
Vitamin K1 had no effect on these particular markers, which elides the key difference between the two; while K1 (phylloquinone) is as important as its cousin for blood clotting, K2 (menaquinone) is the essential nutrient for combating calcium deposits and bone health more generally.
Vitamin K2 exists in a number of forms, from the synthetic, commercially available menaquinone-4 (MK-4) to the natural menaquinone-7 (MK-7).
Both variants also available in different foods, with K1 found mostly in leafy green vegetables and olive oil and K2 found in small amounts in chicken, egg yolks, cheese, butter and fermented soya beans (better known as natto).
Another clinical study from 2015, also in the Netherlands, looked specifically at MK-7. 244 postmenopausal women were given either 180 mcg of MK-7 or a placebo, every day for three years.
Researchers noted that age-related arterial stiffness was significantly decreased in the MK-7 group. Vascular elasticity was also improved in the vitamin K2 group.
You may be wondering at this point how much vitamin K helps to protect against cardiovascular events. Though more work is definitely needed to confirm optimal levels, a population-based study of 16,000 healthy women aged 49-70 indicated that for every 10 mcg of vitamin K2 consumed, the risk of coronary heart disease dropped by 9%.
Given the large number of participants, and the fact that all were free of cardiovascular disease at baseline, this data could be instructive when it comes to setting an ideal allowance.
And there is one last study which it would be remiss of us to omit; that which was published earlier this month in the journal Nutrients.
Researchers assessed the prevalence of functional vitamin K insufficiency to determine to what extent blood levels of MGP were associated with all-cause and cardiovascular mortality.
4,275 subjects were included in the population-based Prevention of Renal and Vascular End-Stage Disease (PREVEND) study, and worryingly, 31% of them were deemed deficient in vitamin K.
Unsurprisingly, vitamin K deficiency was higher (50%) among the elderly and those with conditions such as type-2 diabetes, cardiovascular disease and hypertension.
Researchers from Groningen University found an association between low vitamin K status (as revealed by blood levels of desphospho-uncarboxylated MGP, or dp-ucMGP) and cardiovascular mortality, with risks starting to rise substantially at 414 picomoles/litre and 557 pmol/l.
The pertinent question to ask, of course, is whether vitamin K deficiency is a cause of such morbidities or an effect. Based on the information at hand, it is not easy to make a firm conclusion.
That said, the authors of a randomised study from 2015, looking at blood MGP levels among the Finnish population, felt confident enough to “suggest causality” between blood MGP levels and coronary events and non-cancer mortality.
Remember, vitamin K is the nutrient which activates heart-protective MGP levels.
Is the Recommended Daily Allowance Enough?
According to the NHS, adults require around 1 mcg per day of vitamin K per kilogram of bodyweight. As with many nutrients, however, the health service fails to acknowledge that the Western diet is sorely lacking when it comes to vitamin K, pointing out merely that “you should be able to get all you need by eating a varied and balanced diet.”
In truth, supplementing with K2 is a very viable alternative recommended by many health experts, including the authors of the PREVEND study. Not least due to the nutrient’s small circulating blood levels and low tissue stores.
Another problem with the current guidelines is that no distinction is made between the two forms of vitamin K, let alone subtypes of K2.
Since many people are already unaware of the benefits of vitamin K at all, this oversight is cause for gross concern.
One could hit their RDA of vitamin K from K1 but have sub-optimal levels of K2 needed to prevent arterial calcification and promote overall bone/cardiovascular health.
One supplement you might want to look at is Frunutta’ Sublingual Vitamin K2. Not only does it contain 500 mcg of vitamin K2, more than enough to meet your RDA, but the micro tablets bypass the digestive system entirely: just place beneath your tongue and allow it to dissolve.
This soy-free, highly pure K2 (over 95%) is in the form of MK-4, a relatively short-chain menaquinone. MK-4 makes up the greatest percentage of vitamin K2 in our body.
It is wise to combine vitamin K2 with vitamin D3. Multiple studies have shown that the vitamins work synergistically to reduce the progression of atherosclerosis and reduce oxidative stress.
This is probably because both interact with calcium in beneficial ways, K by directing it where it needs to go and D by helping the body better absorb it.
Vitamin D supplements are widely recommended, particularly during autumn and winter, but an increasing number of integrative doctors believe it should be combined with supplemental vitamin K in order not only to maximise benefits but to avoid excessively high levels of calcium in the blood.
If you wish to benefit from vitamin K2 and D3 – and also heart-healthy omega-3 fish oils – WHC’s QuattroCardio is the perfect supplement. It provides the same dosages of the former, plus 1,200 mg of vital omega-3.
There’s also 100 mg of CoenzymeQ10, an essential physiological cofactor for energy production and a powerful antioxidant.
QuattroCardio is, in our view, one of the very best natural supplements on the market today, particularly as far as cardiovascular health is concerned.
If you’ve no use for the omegas – perhaps you eat plenty of salmon, or you follow a vegan diet and get your EFAs from chia – Frunutta’s sublingual Vitamin D3 is a safe bet. Two strengths are available, 1,000 IU and 5,000 IU.
In summary, the existing evidence suggests that vitamin K forms an important part of a heart-healthy diet. Given the prevalence of deficiency, and the sub-optimal bioavailability of vitamin K from food, it’s worth considering a supplement to meet your daily requirement.
If the subject of heart health is one that interests you, we have a few more articles you might be interested in reading:
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One study showed that the relative risk of CHD mortality was statistically reduced among those consuming at least 32 mcg per day of vitamin K2.