Should I take a Vitamin K2 supplement?

Should I take a Vitamin K2 supplement? I have been surprised how many women have asked me this question since launching Vital7® 8 weeks ago. It's a fair question and one worth answering properly, because there's a lot of information (and misinformation) online.

If you've shopped for a Vitamin D supplement lately, you've probably noticed many now include Vitamin K2. It's marketed as the "missing piece" for healthy bones, heart health, and helping calcium go to the "right places" in the body.

As an Accredited Practising Dietitian (APD), I care about what the evidence actually says. So let’s look at what Vitamin K2 does and unpack what the research shows.

In summary

• Most women eating a varied, plant-rich diet already get enough Vitamin K from food.
• Vitamin K2 is heavily marketed alongside Vitamin D, but there's no evidence it improves Vitamin D absorption.
• The highest-quality evidence available today does not consistently show that Vitamin K2 supplements improve bone density, reduce fractures, or lower cardiovascular disease risk in healthy adults.

What is Vitamin K and what does it do?

Vitamin K isn't one nutrient, but rather it's a family of compounds.

The form we get from food is Vitamin K1 (phylloquinone), found predominantly in green leafy vegetables. It's the primary dietary source of Vitamin K, and it's the form Australia's official Nutrient Reference Values are based on.

Vitamin K is best known for its role in normal blood clotting. It also activates proteins involved in bone metabolism and calcium regulation which is why researchers have been investigating whether Vitamin K2 supplements offer additional benefits for bone and cardiovascular health.

Can you get enough Vitamin K from a plant-based diet?

Yes.

In Australia and New Zealand, the Adequate Intake (AI) for Vitamin K for women is 60 micrograms per day (NHMRC & Ministry of Health NZ, 2006). Vitamin K1 is abundant in leafy greens, and a single serve can meet, or even exceed the AI.

Food	Typical serve	Approx. Vitamin K1*
Kale, cooked	½ cup	250–300 µg
Spinach, raw	1 cup	120–150 µg
Broccoli, cooked	½ cup	80–120 µg
Bok choy, raw	1 cup	40–60 µg
Mixed salad leaves	1 cup	40–70 µg

*values are based on the Australian Food Composition Database (FSANZ).

A single cup of raw spinach or half a cup of cooked kale provides more than the daily AI for Vitamin K for women.

So what about Vitamin K2?

This is where most of the confusion starts.

Vitamin K2 is often marketed as offering unique benefits beyond those provided by the Vitamin K naturally found in plant foods. However, there is currently no evidence that consuming Vitamin K2 specifically is necessary if overall Vitamin K intake is adequate. This is because our gut bacteria can convert Vitamin K1 from plant foods into Vitamin K2 (Nakagawa et al., 2010) in the same way other mammals do, which is why Vitamin K2 is found in animal products. That’s also why some fermented foods like natto have Vitamin K2 - the bacteria make it.

The Australian and New Zealand Nutrient Reference Values provide recommendations for total Vitamin K intake, rather than separate recommendations for Vitamin K1 and Vitamin K2. This reflects the current understanding that overall Vitamin K intake, rather than individual forms, are the basis for nutritional recommendations (NHMRC & Ministry of Health NZ, 2006).

Does Vitamin K2 improve Vitamin D absorption?

No.

Despite how often they're sold together, there's currently no evidence that Vitamin K2 improves the absorption of Vitamin D.

The theory behind pairing them is understandable as Vitamin D helps your body absorb calcium, while Vitamin K activates proteins involved in directing that calcium within bone and other tissues. Because the two nutrients work in related biological pathways, supplement companies often bundle them together.

However, nutrients working together in the body is not the same as one improving the absorption of the other and those two concepts are often confused in supplement marketing.

So why do so many supplement brands include Vitamin K2?

This is where things become more nuanced.

Some formulators take the view that, because Vitamin K2 has a plausible biological role and has shown promise in some studies, it's reasonable to include it while waiting for stronger clinical evidence. Others prefer to include only nutrients where supplementation has consistently demonstrated meaningful benefits in high-quality human trials.

What does the research actually show?

Vitamin K2 has been extensively studied over the past two decades, particularly for bone and cardiovascular health.

Some early studies suggested promising benefits. However, more recent systematic reviews and meta-analyses have found the overall evidence to be inconsistent. In addition, several influential osteoporosis studies that contributed to the early enthusiasm have since been questioned or retracted due to concerns about research integrity, reducing confidence in some of the original findings (Grey et al., 2018; Avenell et al., 2020).

Put it all together and the highest-quality evidence available today does not consistently show that routine Vitamin K2 supplementation improves bone mineral density, reduces fracture risk, or lowers cardiovascular disease risk in healthy adults (Mott et al., 2019; Palermo et al., 2017; Vlasschaert et al., 2020).

None of this means Vitamin K isn't important because it clearly is. It simply means that current evidence does not support routine Vitamin K2 supplementation for healthy adults who are already meeting their Vitamin K needs through diet.

So, should you take a Vitamin K2 supplement?

Based on the evidence available today, most women eating a varied, plant-rich diet are unlikely to see an additional benefit from routinely supplementing with Vitamin K2.

The strongest, most consistent evidence still points to eating plenty of leafy green vegetables, which provide Vitamin K1 alongside fibre, folate, carotenoids, and a wide range of other nutrients that work together.

When we developed the Vital7® Foundation Formula, we had to make evidence-based decisions about every ingredient. We chose to include nutrients where the evidence for supplementation was consistently strong, and to leave out ingredients where the benefits for women remain uncertain. Based on the current research, Vitamin K2 fell into the second category.

It's also worth remembering that more ingredients don't necessarily make a supplement better. Every ingredient should have a clear, evidence-based reason for being included.

Instead, we prioritised nutrients with stronger supporting evidence for women following predominantly and fully plant-based diets. You can read more about the evidence behind each ingredient on the Vital7® Foundation Formula product page.

Frequently Asked Questions

Can I take Vitamin D without Vitamin K2?

Yes. Vitamin D supplements can be taken without Vitamin K2. While the two nutrients are involved in related biological pathways, there is currently no evidence that Vitamin K2 improves Vitamin D absorption or is required for Vitamin D to work effectively.

Can vegans get enough Vitamin K?

Yes. Vitamin K1 is abundant in plant foods, particularly leafy green vegetables. Most people eating a varied plant-based diet can comfortably meet the recommended intake through food alone.

Who should speak to a healthcare professional before taking Vitamin K supplements?

Anyone taking warfarin or other Vitamin K antagonist medications should seek medical advice before changing their Vitamin K intake, whether through food or supplements. People with osteoporosis, certain medical conditions, or concerns about their nutritional status should also seek personalised advice from their GP or an Accredited Practising Dietitian.

This article is intended for general education purposes and does not replace personalised medical or nutrition advice. If you have concerns about your about your health or nutrition status speak with your GP or an Accredited Practising Dietitian.

References

Australian Government Department of Health and Ageing, National Health and Medical Research Council (NHMRC), & Ministry of Health (NZ). Nutrient Reference Values for Australia and New Zealand: Including Recommended Dietary Intakes. Canberra: NHMRC; 2006.

Food Standards Australia New Zealand (FSANZ). Australian Food Composition Database.

Nakagawa K, Hirota Y, Sawada N, et al. Identification of UBIAD1 as a novel human menaquinone-4 biosynthetic enzyme. Nature. 2010.

Karl JP, Fu X, Wang X, et al. Fecal menaquinone profiles of overweight adults are associated with gut microbiota composition. American Journal of Clinical Nutrition. 2015.

Mott A, Bradley T, Wright K, et al. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis. Osteoporosis International. 2019.

Palermo A, Tuccinardi D, D'Onofrio L, et al. Vitamin K and osteoporosis: Myth or reality? Metabolism. 2017.

Vlasschaert C, Goss CJ, Pilkey NG, et al. Vitamin K Supplementation for the Prevention of Cardiovascular Disease: Where Is the Evidence? Nutrients. 2020.

Grey A, Avenell A, Bolland M. Revised Meta-analysis of Vitamin K and Fractures. JAMA Internal Medicine. 2018.

Avenell A, Grey A, Gamble GD, Bolland MJ. Concerns About the Integrity of the Yamaguchi Osteoporosis Prevention Study Report. American Journal of Medicine. 2020.