Which Vitamin K Is Best for Bones? 14 Types of Vitamin K

By Dr. Baker, ND

Not all vitamin K is created equal and different types of vitamin K have different functions in the body. For example, a 2022 study found a 58% reduction in fractures with a vitamin K subtype, MK4, whereas research has found no fracture reduction with MK7.

Two Main Categories of Vitamin K

The two broad categories of vitamin K include phylloquinone (vitamin K1) and the menaquinones (vitamin K2), which include 10 subtypes.

Which Vitamin K Do Supplements Use?

Multivitamins often contain vitamin K1. While vitamin D + K combination supplements often contain vitamin K2 subtype menaquinone-7. Interestingly, menaquinone-4, another K2 subtype, is not often used – despite having been shown to reduce fractures and improve bone strength.

Benefits of Menaquinone-4 (MK-4)

Aside from reducing fractures in half, a 2019 study also found improved lumbar spine bone density with MK-4 use by 50mg per cubic centimeter of bone. While that may seem small, if we extrapolate that throughout the entire skeleton, that works out to about 92 grams of bone tissue. To put this in context, a 2023 study found vitamin D increased bone density by just 6.8mg/cm^2 (12.5g if we extrapolate to the entire skeleton). A 2010 study found bisphosphonates improved lumbar BMD by 30mg, or 55.2 grams of total bone if we extrapolate again.

Total Bone Gained:

• MK-4: 92 grams

• Bisphosphonates: 55.2 grams

• Vitamin D: 12.5 grams

While bone mineral density changes may seem modest, a small amount can make a large difference for bone strength. Furthermore, some research suggests that MK-4 may also improve the overall bone quality and architecture, thereby increasing bone strength and significantly lowering fractures despite modest changes of bone mineral density.

What Dose of MK-4 Is Needed?

The studies showing fracture reductions use a dose much higher than what is found in supplements and foods available in Canada. Even taking an entire bottle of vitamin K or a whole pound of kale per day would still be lower than what was needed to show a fracture reduction in the research above. Note, we are not suggesting taking an entire bottle or eating a pound of kale! This high of a dose needs to be done under the care of a health professional with proper monitoring. Please reach out to one of our naturopathic doctors who can prescribe a dose that is considered both safe and beneficial.

How Long Does it Take For Vitamin K2 MK-4 to Work?

In the 2019 study above most trials analyzed were around 1.5 years, so benefits likely begin with the first couple years. The greatest benefit is the impact on fracture risk, which may be difficult to quantify for people as it is hard to ask oneself, “how many fractures did I not have because of vitamin K?”.

Do Other Forms Lower Fractures?

While research is still limited, a review study found that only the MK-4 form of vitamin K was associated with lower risk of fractures. Furthermore, a 2020 study found that patients using MK-7 did not see an improvement in bone mineral density.

Side Effects of MK-4

Side effects that have been documented are exceptionally rare and mild, such as stomach upset and skin rash. Animal studies show no observable side effects even at extremely high doses.

What Does Vitamin K Do?

Vitamin K improves bone strength by stimulating growth of the cells (osteoblasts) that make bone tissue and inhibits the cells that break down bone tissue (osteoclasts). Studies also show that vitamin K may lower inflammation which is important because inflammatory compounds are thought to progress bone loss. Vitamin K also plays a role in blood clotting, cardiovascular health, and brain health.

Where Can You Find MK-4?

The exact type used  in the research above and dose required is available through a naturopathic doctor.

Who Needs to Avoid Vitamin K?

Caution needs to be exercised with vitamin K for anyone on blood thinners such as warfarin.

Types of Vitamin K

Vitamin K1 (Phylloquinone; “K1”)

Found in: leafy greens (kale, spinach, collards, Swiss chard), broccoli/Brussels sprouts, herbs (parsley), and some plant oils (soybean/canola)

Vitamin K2 (Menaquinones; “K2”) — MK subtypes

• Menaquinone-4 - Found in: animal foods (liver, egg yolk, butter, some meats); also made in human tissues from K1

• Menaquinone-5 - Found in: mainly bacterial (rare in typical diets); possible trace amounts in some fermented foods

• Menaquinone-6 - Found in: mainly bacterial; occasional trace in fermented foods

• Menaquinone-7 - Found in: natto (fermented soybeans; richest common source), also some fermented foods and certain cheeses (usually lower than natto)

• Menaquinone-8 - Found in: fermented foods, especially some aged cheeses; also produced by bacteria

• Menaquinone-9 - Found in: aged/fermented cheeses (commonly reported in cheeses), and other fermented foods; also produced by gut/food bacteria

• Menaquinone-10 - Found in: mostly bacterial; can appear in trace amounts in some long-fermented/aged foods (data limited)

• Menaquinone-11 - Found in: mostly bacterial; occasional trace in some fermented foods (data limited)

• Menaquinone-12 - Found in: mostly bacterial; occasional trace in fermented foods (data limited)

• Menaquinone-13 - Found in: mostly bacterial; occasional trace in fermented foods (data limited)

The other forms that exist are synthetic and include Vitamin K3 (Menadione; “K3”), Vitamin K4 (Menadiol diacetate), and Vitamin K5.

Next Steps

Vitamin K is not a single nutrient, and the form you choose matters—especially when bone strength and fracture risk are the goal. Based on the current research, menaquinone-4 (MK-4) stands apart from other forms, for its consistent association with reduced fractures and meaningful improvements in bone strength and quality.

If you are considering vitamin K for bone health, the next steps are:

• Do not assume all vitamin K supplements are interchangeable. Most over-the-counter products contain vitamin K1 or MK-7, which have not shown the same fracture-reducing benefits as MK-4 in clinical trials.

• Work with a qualified healthcare professional. The doses of MK-4 used in fracture-reduction studies are much higher than those found in standard supplements or foods and require professional guidance and monitoring to ensure safety and appropriateness.

• Assess bone health in context. Bone mineral density, fracture history, age, medications, vitamin D status, calcium intake, and inflammation all influence fracture risk. Vitamin K is one piece of a broader bone-health strategy.

• Individualize the plan. A personalized approach helps balance potential benefits with safety, especially for those on medications or with underlying health conditions.

If you are interested in understanding whether MK-4 may be appropriate for you, our naturopathic doctors can help assess your bone health, review the evidence in the context of your history, and guide you toward a comprehensive plan. Dr. Baker (ND) has his prescribing license and can prescribe at the doses shown in research to improve bone strength.

Disclaimer: This post is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider or a qualified medical professional before starting any new treatment or if you have questions about your medical condition. While we aim to provide accurate, research-based information, individual needs and responses to treatments can vary. Our clinic offers personalized consultations to discuss health concerns and develop tailored care plans. Never disregard professional medical advice or delay seeking it because of information you have read on this site.

Vitamin K2, MK-4