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Consider Destiny’s Child: powerhouse group with plenty of Grammy nominations to prove it. But people only really talk about Beyonce. You may have never considered vitamin K before because, well, it’s more of the Michelle Williams of the group (she was the third member of Destiny’s Child. Don’t worry; we’ll wait while you Google it).
Vitamin K, which is actually a group of fat-soluble compounds, plays a central role in several important functions of our body—we just attribute these health benefits to other vitamins and minerals.
Two forms of K are especially important for humans: vitamin K1 and K2. K1 is called phylloquinone when made naturally, phytonadione when made synthetically. And K2 is even a little more complicated. Called menaquinone when made naturally and menadione when made synthetically, K2 has many different forms.
Each is named based on the length of a side chain on its chemical structure. You may see menaquinones expressed as menaquinone-7 (MK‐7), which is commonly found in fermented vegetable products, and menaquinone-4 (MK-4), which is commonly found in animal products.
These two are the most important forms, but there are other MKs, such as MK-5 and MK-6. But despite the confusion, and the wide range of names, K1 and K2 work on similar structures and processes in your body, though K2 may offer heart-health benefits that K1 does not.
Benefits of vitamin K
We don’t want to carry this comparison too far, but we’re back to Michelle Williams for a second. The previously marginalized ex-member of the pop group proved on The Masked Singer in 2019 that she has an excellent set of pipes, and was an asset to the group all along. So it’s time you learn what vitamin K can do solo, too.
Promotes blood clotting
You probably think of blood cells or platelets when clotting is discussed, but vitamin K is actually essential to this process that keeps you from excessive bleeding at even the smallest of injuries.
K plays a key role in the creation of pro-blood clotting proteins known as factors II (prothrombin), VII, IX, and X, and anticoagulant (anti-blood clotting) proteins known as proteins C, S, and Z.
But even though this process is important, some people clot too easily. Some blood-thinning medications, such as warfarin (brand name Coumadin), work by antagonizing the action of vitamin K.
Because of this, it is extremely important that individuals on warfarin keep their vitamin K levels steady. That means watching their vitamin K intake throughout the time they’re taking warfarin and getting regular blood tests done.
Prevent osteoporosis and support strong bones
But wait, isn’t that calcium and vitamin D? That’s the Destiny’s Child scenario at play. There are actually vitamin K-dependent proteins required for proper bone health.
This fat-soluble vitamin has to be present for an enzyme called gamma-glutamyl carboxylase to make the protein osteocalcin work, through a process called carboxylation, which is required for bone growth (Beulens, 2013).
Despite its critical role in regulating bone metabolism, it’s unclear whether vitamin K can reduce the risk of bone fractures. Past research has suggested that getting enough vitamin K can help prevent bone loss and decrease hip fractures in older men and women (Hamidi, 2013).
And research done specifically on postmenopausal women with osteoporosis has shown potential benefits from K2 supplementation. But a meta-analysis found that vitamin K may help with bone mineral density in some physical locations, but not others (Fang, 2011; Iwamoto, 2014).
More work needs to be done to clarify the relationship and see if supplementing with the Ks could help prevent fractures, especially those at the hip.
May improve memory in older adults
Vitamin K-dependent proteins (VKDP) that require the intake of vitamin K to function properly don’t just affect your bone modeling, though.
The VKDPs not associated with bone growth or blood clotting are involved with the metabolism of sphingolipids, a class of lipids commonly found in brain cell membranes that are involved with cellular events.
Changes in sphingolipid metabolism have been linked with not only age-related cognitive decline but also neurodegenerative conditions like Alzheimer’s (Ferland, 2012).
Recent research suggests that vitamin K antagonists, which are used as anticoagulants, may have a negative effect on visual memory, verbal fluency, and brain volume. But it doesn’t appear to go in just one direction (Alisi, 2019).
Higher vitamin K levels, specifically phylloquinone (K1), are associated with improved verbal episodic memory, though no difference was observed with non-verbal episodic memory (Presse, 2013).
Keep blood pressure down
Getting an adequate intake of vitamin K may also be essential to your heart health because it may be able to help prevent hypertension (abnormally high blood pressure) and lower your risk of cardiovascular disease (more on that in a second).
Low vitamin D and K status have been linked to hypertension with increases in both systolic and diastolic blood pressure. Like D, vitamin K interacts closely with calcium in your body, in this case, helping to regulate the levels of this mineral in your blood (Ballegooijen, 2017).
Vascular calcification—a process in which minerals like calcium are deposited in blood vessels, blocking blood flow over time—is common as we age. But getting the proper amount of vitamin K may help prevent mineralization, staving off this process and keeping blood pressure lower.
Lower risk of heart disease
Your risk of a cardiovascular event is closely associated with the calcification of your blood vessels.
In fact, one meta-analysis that looked at 30 studies found a 300–400 percent increase in your risk of cardiovascular events with the presence of calcification on any arterial wall (Rennenberg, 2009).
But higher blood levels of the K1 form of vitamin K are associated with a lower risk of heart disease.
How to get enough vitamin K
Preventing low levels of the Ks doesn’t need to be difficult. Though some people may need dietary supplements, most people can get enough of these fat-soluble vitamins through dietary intake. In fact, if you’re already trying to eat a healthy, balanced diet low in processed foods, you’re likely already eating many food sources of vitamin K.
Though, as we mentioned, some people will need to watch their vitamin K intake, most people don’t need to worry about getting too much vitamin K and instead need to focus on avoiding vitamin K deficiency. Since there are no studied or reported side effects of a high K intake, there’s no established upper tolerable limit (UL) for this vitamin.
Dietary sources of vitamin K
Vitamin K1 is mostly found in green vegetables, although legumes and berries also boast this nutrient.
You can boost your vitamin K status by making sure green leafy vegetables such as kale, Brussels sprouts, or collard greens get plenty of rotation through your weekly meal plan. Leafy greens can be added to a wide variety of recipes to easily boost dietary intake and ensure you don’t get bored or feel like you’re living off of salads.
You can reach for mostly animal-based products such as eggs and liver (beef, chicken, or goose) to get vitamin K2. Your body can convert K1 to K2, but researchers believe this process is inefficient.
So though K2 is found in small quantities in food, it may be most efficient to get this vitamin from your dietary intake rather than relying on your body’s conversion processes. Natto, a fermented soy product, is actually the richest food source of K2, delivering 775 micrograms (mcg) of the MK-7 form of vitamin K2 in a 100-gram serving (Tsukamoto, 2000).
Vitamin K supplements
Although for the average person, there’s little harm in taking a high-quality vitamin K supplement, certain people should avoid them.
Those taking blood thinners need to talk to their healthcare provider about keeping their blood levels stable and the role food sources and supplements play in that. But some people may benefit more from vitamin K supplements, such as those who have conditions that make it hard to absorb this and other vitamins through dietary sources.
People with gastrointestinal conditions like Crohn’s disease or celiac disease or those with cystic fibrosis may have malabsorption issues that make supplements essential for avoiding deficiency.
- Alisi, L., Cao, R., Angelis, C. D., Cafolla, A., Caramia, F., Cartocci, G., … Fiorelli, M. (2019). The Relationships Between Vitamin K and Cognition: A Review of Current Evidence. Frontiers in Neurology, 10. doi: 10.3389/fneur.2019.00239, https://www.frontiersin.org/articles/10.3389/fneur.2019.00239/full
- Ballegooijen, A. J. V., Cepelis, A., Visser, M., Brouwer, I. A., Schoor, N. M. V., & Beulens, J. W. (2017). Joint Association of Low Vitamin D and Vitamin K Status With Blood Pressure and Hypertension. Hypertension, 69(6), 1165–1172. doi: 10.1161/hypertensionaha.116.08869, https://www.ncbi.nlm.nih.gov/pubmed/28396533
- Beulens, J. W. J., Booth, S. L., Ellen G. H. M. Van Den Heuvel, Stoecklin, E., Baka, A., & Vermeer, C. (2013). The role of menaquinones (vitamin K2) in human health. British Journal of Nutrition, 110(8), 1357–1368. doi: 10.1017/s0007114513001013, https://www.ncbi.nlm.nih.gov/pubmed/23590754
- Fang, Y., Hu, C., Tao, X., Wan, Y., & Tao, F. (2011). Effect of vitamin K on bone mineral density: a meta-analysis of randomized controlled trials. Journal of Bone and Mineral Metabolism, 30(1), 60–68. doi: 10.1007/s00774-011-0287-3, https://www.ncbi.nlm.nih.gov/pubmed/21674202
- Ferland, G. (2012). Vitamin K, an emerging nutrient in brain function. BioFactors, 38(2), 151–157. doi: 10.1002/biof.1004, https://www.ncbi.nlm.nih.gov/pubmed/22419547
- Hamidi, M. S., Gajic-Veljanoski, O., & Cheung, A. M. (2013). Vitamin K and bone health. Journal of Clinical Densitometry, 16(4), 409–413. doi: 10.1016/j.jocd.2013.08.017, https://www.ncbi.nlm.nih.gov/pubmed/24090644
- Iwamoto, J. (2014). Vitamin K2 Therapy for Postmenopausal Osteoporosis. Nutrients, 6(5), 1971–1980. doi: 10.3390/nu6051971, https://www.ncbi.nlm.nih.gov/pubmed/24841104
- Presse, N., Belleville, S., Gaudreau, P., Greenwood, C. E., Kergoat, M.-J., Morais, J. A., … Ferland, G. (2013). Vitamin K status and cognitive function in healthy older adults. Neurobiology of Aging, 34(12), 2777–2783. doi: 10.1016/j.neurobiolaging.2013.05.031, https://www.ncbi.nlm.nih.gov/pubmed/23850343
- Rennenberg, R., Kessels, Schurgers, Engelshoven, V., Leeuw, P. D., & Kroon. (2009). Vascular calcifications as a marker of increased cardiovascular risk: A meta-analysis. Vascular Health and Risk Management, 185. doi: 10.2147/vhrm.s4822, https://www.ncbi.nlm.nih.gov/pubmed/19436645
- Tsukamoto, Y., Ichise, H., & Yamaguchi, M. (2000). Prolonged Intake of Dietary Fermented Soybeans (Natto) with the Reinforced Vitamin K2 (Menaquinone-7) Enhances Circulating .GAMMA.-Carboxylated Osteocalcin Concentration in Normal Individuals. Journal Of Health Science, 46(4), 317–321. doi: 10.1248/jhs.46.317, https://www.ncbi.nlm.nih.gov/pubmed/10701161
Dr. Mike is a licensed physician and the Director, Medical Content & Education at Ro.