Should You Take Vitamin K2 and Vitamin D3 Together?

Vitamin K2 supplements are exploding in popularity, with claims of transforming bone and heart health—particularly when paired with Vitamin D3. So, what does the evidence show? Are these supplements worth our time and money?

The History of Vitamin D and K

The excitement for Vitamin K2 and D3 began when doctors were puzzled by a problem many children started having since the Industrial Revolution: rickets. This condition causes children's bones not to form properly. Scientists suspected it had something to do with diet. Rates of rickets were especially high in Scotland, so one researcher fed the common Scottish diet to dogs. They developed rickets, too.

He found he could cure the condition by giving the dogs cod liver oil. It was known at the time that this oil was high in vitamin A, so he concluded that too little vitamin A in the diet caused rickets. But he was wrong.

Another researcher wasn't so sure. He decided to try cod liver oil with the vitamin A removed. It still cured rickets, indicating something else was at work. Scientists gave this other factor the name "vitamin D."

Simultaneously, scientists elsewhere discovered that exposing children with rickets to sunlight could cure the condition. Eventually, it was understood that sunlight stimulates our skin to produce vitamin D. By the early 1930s, we knew that vitamin D could be obtained from our diet or sun exposure and that it cured rickets.

But why? What was the connection? Further discoveries revealed that vitamin D plays a crucial role in helping our bodies absorb calcium in our digestive tract and stimulates bone formation. Without vitamin D, we may be taking in enough calcium, but our bodies can't utilize it effectively.

1. How Does Vitamin K Fit In?

Vitamin K's main role relates to coagulation—the ability of our blood to form clots to stop bleeding.

However, vitamin K also plays a role in how our bodies use calcium. It helps keep calcium in our bones, promoting bone strength.

2. Bringing It All Together

Three ingredients work together in our bodies to promote healthy bones: calcium, vitamin D, and vitamin K. Our bones are about 40% calcium, an essential ingredient. But for our bodies to make proper use of calcium, we also need vitamins D and K. This is the basis for the idea that we should take vitamin D and K together, as well as the purported benefits for bone health.

But what about the benefits for cardiovascular health? Here's the intriguing possibility: If vitamin K keeps calcium in our bones, it might also help keep it out of our blood, potentially reducing the risk of cardiovascular disease. Calcium in the blood can contribute to harmful deposits that form in the heart and arteries.

The Science

That's the theory, anyway. What does the research actually show?

There's been some controversy around this topic. A meta-analysis published in 2006 claimed that vitamin K2 helps prevent fractures and strengthen bones [1]. However, many of the individual trials included in that analysis have been retracted due to methodological issues [2]. Later trials have also been retracted because of problems with study methods [3]. This makes it hard to connect the theory that vitamin K2 should help with bone strength to actual clinical evidence.

Luckily, there are some robust trials. For example, a 2009 randomized double-blind placebo-controlled trial found that vitamin K2 supplements didn't improve bone strength [4]. This study used the MK4 version of vitamin K2 at a high dose of 45 mg daily, with all participants also receiving daily calcium and vitamin D supplements.

Does this show the theory about vitamin K2 and bone strength is flawed? Not necessarily. The study only ran for 12 months, which is a short duration when considering bone strength. In contrast, a 2013 study lasting three years used MK7, a different type of vitamin K2, at a dose of 180 micrograms. The results were different, showing significant improvements in bone strength, especially in the lower back and hip bone [5]. Consequently, the European Food Safety Authority approved a health claim for vitamin K, noting that "a cause and effect relationship has been established between the dietary intake of vitamin K and the maintenance of normal bone" [6].

3. Cardiovascular Health Claims

Does this mean we can use vitamin K to promote heart health by preventing calcium buildup in other parts of our body? Researchers have looked into this in relation to heart valves and blood vessels.

Heart Valves

As we age, calcifications can develop around heart valves, hardening them and interfering with their function. In 2022, a randomized double-blind placebo-controlled trial published in the Journal of Circulation aimed to see whether vitamin K2 supplements reduce calcification around the aortic valve [7]. Conducted at four Danish hospitals, the study compared 720 micrograms of vitamin K2 (MK7) plus vitamin D to a placebo over 24 months. Surprisingly, there was no treatment effect—no difference between the placebo and treatment groups, even in smaller subgroups [7].

Blood Vessel Health

However, the story is different for blood vessel health. Observational studies, such as one that followed nearly 5,000 people for seven years, found that higher intakes of vitamin K2 were associated with lower rates of all-cause mortality and heart disease, particularly coronary heart disease [8]. Though observational, these findings prompted randomized controlled trials. In 2015, a double-blind, placebo-controlled trial showed that MK7 supplementation improved arterial stiffness in healthy postmenopausal women [9].

A newly published study by the same group that conducted the aortic valve study measured calcium buildup in blood vessels using the Coronary Artery Calcium (CAC) score. Participants were split into placebo and vitamin K2 plus D groups. After two years, there was no significant difference in CAC progression between the groups [10]. However, among participants with a baseline CAC score of ≥400 AU, there was a significant reduction in calcium progression in the vitamin K2 group [10].

4. Safety Considerations

Calcium buildup in blood vessels is a late-stage finding of atherosclerosis, which involves blockages developing in blood vessels. If vitamin K2 stops calcium from building up, there's a concern that blockages might become weak and prone to causing heart attacks.

The study addressed this by examining non-calcified plaque buildup. In the placebo group, plaque grew, while in the vitamin K2 group, it slightly decreased [10]. Additionally, safety events related to blood vessel blockages were reduced in the vitamin K2 group compared to placebo [10].

5. Summary of Findings

For individuals with significant calcium buildup in their blood vessels, vitamin K2 supplementation appears to reduce calcium progression.

Furthermore, vitamin K2 may stabilize vulnerable plaques in blood vessels, potentially lowering the risk of heart attacks. However, these findings are novel and hypothesis-generating, requiring further research.

6. How Much Vitamin K Do We Need?

There are two forms of vitamin K: K1 and K2. While K1 stays in the liver, K2 circulates throughout the body and is involved in the studies discussed here. The recommended daily intake for vitamin K1 is 120 micrograms, but no official recommendations exist for vitamin K2 due to limited research [6].

Personally, I prefer to use a lower dose of 90 micrograms while we await further research. Additionally, while vitamin K1 is found in leafy green vegetables, vitamin K2 is primarily found in fermented products like fermented soy and cheese, making it challenging to obtain enough from diet alone. Therefore, I choose to supplement with vitamin K2.

7. Choosing the Right Vitamin K2 Supplement

There are several forms of vitamin K2, but I prefer the MK7 version because it is absorbed most efficiently and has the greatest bioavailability [11].

It also has the longest half-life, meaning it stays in the body longer. I take 90 micrograms of vitamin K2 as part of a multivitamin and mineral supplement called MicroVitamin.

8. Safety of Vitamin K2 Supplements

According to the NIH supplement database, no adverse effects have been associated with vitamin K consumption from food or supplements [6].

However, there are important interactions with blood thinners like warfarin. Therefore, it's crucial to consult with your doctor before taking any supplements.

9. What About Vitamin D?

As discussed, vitamin D and vitamin K work together, and maintaining adequate levels of both is essential for health. But do we need to supplement with vitamin D, and if so, how much?

The newest Endocrine Society Guidelines offer updated recommendations to maximize the benefits of this crucial vitamin. Check out this video to learn more about the latest recommendations for vitamin D supplementation. (link: https://youtu.be/PxvXKF0zLzo )

Conclusion

In conclusion, vitamin K2 supplements, particularly when taken with vitamin D3, show promise in promoting bone health and potentially improving cardiovascular health by reducing calcium buildup in blood vessels.

While there is excellent evidence supporting the role of vitamin K2 in bone health, the evidence for cardiovascular benefits is still emerging and requires further research. If you're considering supplementing with vitamin K2 and D3, it's essential to consult with your healthcare provider, especially if you're taking blood thinners.

References

1. https://pubmed.ncbi.nlm.nih.gov/16801507/
2. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2674866
3. https://pubmed.ncbi.nlm.nih.gov/23346882/
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC2683650/
5. https://pubmed.ncbi.nlm.nih.gov/23525894/
6. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional
7. https://www.ahajournals.org/doi/full/10.1161/CIRCULATIONAHA.121.057008?af=R
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5494092/
9. https://pubmed.ncbi.nlm.nih.gov/25694037/
10. https://www.jacc.org/doi/10.1016/j.jacadv.2023.100643
11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6413124/