Supplements and heart health
Vitamin K2 and your arteries What the New Trial Found, and What to Test
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed August 20267 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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A 2026 trial gave 360 micrograms of vitamin K2 (MK-7) daily for two years to people who already had coronary artery disease. Their artery calcium score rose more slowly than the placebo group’s. It is one modest result. No blood test measures artery calcium, so check the risk markers you can measure.
A vitamin K2 study is doing the rounds. It has landed on supplement forums, in trade press, and in the podcast breakdowns people watch before they buy a bottle. The headline is that a cheap vitamin slowed calcium building up in arteries.
The headline is roughly true. The detail is more interesting, and it points somewhere else entirely. So this guide does two jobs. It reads the trial as the researchers wrote it up. Then it names the heart numbers you can actually put a figure on, which for most people is the gap worth closing first.
By the Helvy Medical Team · Reviewed by a qualified clinician · 7 min read
As of August 2026. Reflects the VitaK-CAC randomised trial, published in JAMA Cardiology in June 2026 and covered across cardiology press through the summer.
1. What the new K2 trial actually found
The trial is called VitaK-CAC. It randomised 167 people with symptomatic coronary artery disease to either 360 micrograms of MK-7 a day or a placebo, and ran for two years. Results were published in JAMA Cardiology in June 2026.
Everyone had a CT scan at the start, at one year and at two years. The scan produces a coronary artery calcium score, measured in Agatston units. It counts how much calcified plaque sits in the heart’s arteries. The score normally climbs with age.
Here is what the two groups did over the two years:
- MK-7 group: 135 units at the start, 150 at one year, 184 at two years
- Placebo group: 145 units at the start, 173 at one year, 214 at two years
- The difference:the yearly rise was about 19 units smaller on MK-7 (p = 0.02)
So the calcium score still went up in both groups. It simply went up more slowly in the group taking the vitamin. That is the whole finding, and it was the outcome the trial set out to measure.
2. What the trial does not prove
Three things, and they matter more than the headline.
Nobody in it was healthy. Every participant had symptomatic coronary artery disease. Entry required a calcium score between 50 and 400 units, so they all had visible calcified plaque already. Around 78% were on a statin. This was a group who knew they had a problem and were being treated for it. You cannot read the result across to a well 40-year-old.
A calcium score is not a heart attack. The trial measured a picture on a scan. It did not measure whether anyone lived longer, or had fewer heart attacks or strokes. Those are the outcomes that decide whether a treatment is worth taking, and this trial was never built to answer them.
It has not been repeated. One trial in 167 people is a start, not a settled answer. Michael Blaha, a cardiologist at Johns Hopkins, put the reaction plainly when the results were covered:
“It’s just a neat experiment... an interesting hypothesis-generating study.”
— Michael Blaha, Johns Hopkins, speaking to TCTMD about VitaK-CAC
He added that it needs replicating before it carries any clinical weight. The trial investigators were similarly careful. They argued the finding is worth following up, not acting on.
3. The heart risk you can measure today
Here is the awkward part of the K2 story. Everyone in that trial knew their calcium score, because they had been scanned. Almost nobody reading this does. And no blood test can measure calcium in an artery.
What blood can describe is the risk that drives plaque forming in the first place. Four markers carry most of that signal, and most UK adults have never seen three of them:
- ApoB — counts the harmful particles, rather than the fat inside them
- Lp(a) — inherited, rarely tested on the NHS, and usually measured once
- hs-CRP — the standard marker of low-grade inflammation
- Full lipids and HbA1c— the context that makes the other three readable
A standard cholesterol blood test gives you a total and an HDL. That is a start, and it misses the particle count and the inherited marker entirely.
Our Advanced Heart Health panel (£159) measures all of them from a home finger-prick sample, analysed by UKAS-accredited UK laboratories. Blood markers describe risk. They cannot see plaque inside an artery, so a good result is a reassuring picture rather than an all-clear.
The order of operations is the point. Check the risk you can put a number on, before optimising the one you cannot. There is more on the full marker set in our heart health hub.
4. Why K2 was expected to do anything
The idea rests on one protein. Matrix Gla protein is made in blood vessel walls, and part of its job is to stop calcium settling where it should not. To switch on, it needs vitamin K.
Without enough vitamin K, more of that protein circulates in its inactive form. Higher levels of the inactive form have been linked with more vascular calcification in observational research. That was the stated rationale when VitaK-CAC was designed, back in 2015.
MK-7 was chosen because it is the long-acting form. It stays in the blood far longer than the K1 in leafy greens, which is why supplement labels favour it. A plausible mechanism is a reason to run a trial. It is not, on its own, a reason to take something.
5. If you are going to take it
Start with the NHS position, which is about diet rather than capsules:
“You should be able to get all the vitamin K you need by eating a varied and balanced diet.”
— NHS, Vitamins and minerals: Vitamin K
The NHS also advises that taking 1mg or less a day is unlikely to cause harm, while warning against taking too much. The trial dose, 360 micrograms, sits well inside that. Most UK MK-7 capsules are between 100 and 200 micrograms.
IF YOU TAKE WARFARIN, STOP AND ASK
Warfarin works by blocking vitamin K. Adding a K2 supplement works directly against it and can shift your INR. This is a conversation with your GP, pharmacist or anticoagulation clinic before you buy anything, not after.
IT IS NOT A REPLACEMENT FOR ANYTHING
Most people in the trial were on a statin as well. Nobody swapped their medication for a vitamin, and the result says nothing about what happens if you do.
FOOD SOURCES EXIST
Natto is by far the richest source of MK-7. Hard and soft cheeses, egg yolk and some fermented foods contribute smaller amounts. K1, the form in leafy greens, is a different molecule with a much shorter stay in the blood.
One question this guide deliberately skips is whether K2 belongs alongside your vitamin D. That is a separate argument about absorption and dosing, and we cover it in our guide to taking D3 and K2 together.
Frequently asked questions
Does vitamin K2 clear calcium out of your arteries?
No. In the VitaK-CAC trial the calcium score rose in both groups over two years. It rose more slowly in the MK-7 group, by about 19 Agatston units a year. Slowing a rise is not the same as reversing one, and no trial has shown K2 removing existing calcified plaque.
Should I start taking MK-7 because of this study?
That is a decision for you and your GP, and the trial does not settle it. Everyone in it already had diagnosed coronary artery disease and most were on a statin. The researchers themselves called for the result to be repeated before it changes what anyone does.
Is there a blood test for artery calcification?
Not directly. Calcium in the coronary arteries is measured with a CT scan, not from blood. What blood can measure is the risk picture behind it: ApoB, Lp(a), hs-CRP, HbA1c and your full lipid breakdown.
What dose did the trial use?
360 micrograms of MK-7 a day, taken for two years. That is higher than a typical UK capsule, which tends to hold 100 to 200 micrograms. The NHS advises that 1mg a day or less of vitamin K supplements is unlikely to cause harm.
Can I take vitamin K2 with warfarin?
Ask your GP, pharmacist or anticoagulation clinic first. Warfarin works by blocking vitamin K, so a K2 supplement pulls against the medication and can change your INR. Do not start one on your own while taking warfarin.
Know your numbers first
Our Advanced Heart Health panel (£159) measures ApoB, Lp(a) and hs-CRP alongside HbA1c and the full lipid breakdown. Home finger-prick kit, results usually within 5 working days of the lab receiving your sample, from UKAS-accredited UK laboratories.
Medical disclaimer:This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. The studies cited measure population-level effects and may not predict an individual response. Do not start, stop or change any supplement or medication based solely on this article — consult your GP or a qualified healthcare professional. All Helvy blood tests are processed by UKAS-accredited UK laboratories to ISO 15189.
Last updated: August 2026 · By Helvy · Medically analysed at UKAS-accredited UK laboratories
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