If you’ve heard the podcast we did with Dr Dan Owens, then you will already have a good idea about some of the basics of Vitamin D (you can also head over and check out our Vitamin D FAQ). But, one of the things we spoke to Dan about was do you need to take Vitamin K2 when .

You can hear what Dr Dan Owens had to say in the Nutrition, Health and Performance podcast, but we’ve broken down some of the research here.

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What is Vitamin K2?

Vitamin K is significantly at play in a wide range of biological activities including regulation of calcium metabolism in tissues, oxidative stress, and inflammatory reactions. Vitamin K naturally falls in two types: vitamin K1 and vitamin K2. Vitamin K deficiency is rare, but less than optimal intake may impair your health over time. Inadequate intake may cause bleeding, weaken your bones and potentially increase your risk of developing heart disease.

Vitamin K1, the most common form of vitamin K, is mainly found in plant-sourced foods, especially dark, leafy green vegetables. Vitamin K2, on the other hand, is only found in animal-sourced foods and fermented plant foods, such as natto

Natto is a traditional Japanese food consisting of fermented soybeans; Bacillus subtilis natto is the source of vitamin K2 in this food, which may contain up to 1100 µg of K2 per 100 grams of food. Other vitamin K2-producing bacteria are lactic acid bacteria and propionic acid bacteria . Both strains are used in the production of cheese and curd cheese, which form the richest sources of vitamin K2 in Europe and Northern America. Small amounts of MK-4 may also be obtained from animal products such as meat and egg yolk.

The current guidelines for vitamin k consumption are limited, with less information compared to most other vitamins and minerals.

The current Estimated Average Requirement (EAR) for vitamin K is 90-120 mcg. To put this in context, half a cup of cooked broccoli contains around 110 mcg and 100g of chicken contains 60mcg.

So most people will be able to obtain enough vitamin K through their diet. A 2012 study reported that in American adults aged 20 and older, the average daily vitamin K intake from foods is 122 mcg for women and 138 mcg for men.

Vitamin k sources

Done and Dusted?

While the information above may seem pretty clear cut, it is important to point out that there is possibly less research into vitamin K than other vitamins. In particular, the role of the different forms of vitamin K. Most green vegetables are high in vitamin K1 but low in vitamin K2, for example. It has also been shown that absorbance of vitamin K1 can be quite low, particularly if eaten as part of a low fat meal. More research is going to be needed then in order to create clearer guidelines.

Vitamin K2 and Vitamin D - Do You Need One With The Other?

Human studies suggest that optimal concentrations of both vitamin D and vitamin K are beneficial for bone and cardiovascular health as supported by genetic, molecular, cellular, and some human studies. While there some studies to suggest a synergistic effect of vitamin D and K2 supplementation (that is - they are more than the sum of their parts), these studies have mostly been in menopausal women, with many of the studies coming from Asia (1). The majority of studies have failed to find an additive effect of vitamin K2 with vitamin D supplementation. 

Further, it is not necessarily ‘dangerous’ to supplement vitamin D without vitamin K2.

The theory from this comes from the thought that excess vitamin D could lead to calcium reabsorption. Increasing vitamin D intake through dietary or supplemental source increases intestinal calcium absorption, particularly when combined with calcium supplementation, and promotes hypercalcemia.

In this context though, a human trial was performed in older women who received either 1200 mg calcium or 1200 mg calcium and 800 IU vitamin D per day over a 12-week period (2). At the end of the 12 weeks, neither group observed a change in calcium concentrations, meaning that calcium was either excreted or stored somewhere. Increased calcium intake by itself may not be problematic as long as there is a steady state between optimal vitamin D and vitamin K concentrations. It is most likely more important to consume excess vitamin D - something that has many potential negative consequences, as we discussed with Dan on the podcast.


1 - Van Ballegooijen, A. J., Pilz, S., Tomaschitz, A., Grübler, M. R., & Verheyen, N. (2017). The synergistic interplay between vitamins D and K for bone and cardiovascular health: a narrative review. International journal of endocrinology, 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613455/

2 - Bischoff H. A., Stahelin H. B., Dick W., et al. Effects of vitamin D and calcium supplementation on falls: a randomized controlled trial. Journal of Bone and Mineral Research. 2003;18:343–351. doi: 10.1359/jbmr.2003.18.2.343.


If you are taking any prescribed medication or have any medical conditions ALWAYS consult your doctor or pharmacist BEFORE taking vitamins or supplements. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle. If pregnant or lactating, ALWAYS consult your doctor before use. Or if you have any queries about any supplement ALWAYS consult a QUALIFIED medical professional.


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