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The vitamin that sends calcium where it’s needed.
Calcium is an important mineral for bone health, muscle contraction, nerve signaling, and blood clotting.[1],[2] But more calcium isn’t necessarily better: If calcium deposits in the walls of arteries, it can cause the blood vessels to become stiff, thus increasing the risk of heart disease. [3],[4],[5]
One way to reap the benefits of calcium while minimizing the risks is to keep the daily dosage of calcium supplements under 1,000mg.[6],[7] Another strategy is to get adequate amounts of vitamin K2.[8]
What is vitamin K2?
Also known as menaquinone, vitamin K2 has been shown to block the formation of hard calcium deposits in the walls of arteries, thus preventing stiffness in the vessels.[9],[10] Smooth, flexible blood vessels preserve blood circulation, thus reducing the risks of blood clots and heart disease.[11],[12] These effects are mediated by K2’s activation of a protein known as matrix GLA protein (MGP).[13]
During states of vitamin K2 deficiency, however, MGP cannot be properly activated, in turn increasing the risk of arterial calcification and atherosclerosis (the thickening of the vessel walls), a risk factor for heart disease.[14],[15],[16],[17],[18]
What the studies say
A study of 4,807 healthy adults age 55 older revealed that high dietary intake of vitamin K2 – at least 32 mcg per day – was linked to a 25% reduction in all-cause mortality and a 50% reduction in deaths related to cardiovascular disease.[19]
These findings were echoed in another population-based study of 16,000 healthy women ages 49 to 70, who followed for a period of eight years. High intakes of natural vitamin K2 were found to confer protection against cardiovascular events like heart attacks and strokes. It was observed that for every 10 mcg of dietary vitamin K2 the women consumed, their risk of coronary heart disease was reduced by 9%.[20]
Another study – this one following 564 postmenopausal women – also found vitamin K2 was associated with decreased coronary calcification, whereas vitamin K1 intake was not.[21]
Fortunately, vitamin K2’s “anti-calcium” effects act on the blood vessels, and not the bones. In fact, vitamin K2 supplementation may enhance bone health.[22]
A randomized, double-blind, clinical trial found that a daily dose of 45mcg of a vitamin K2 supplement improved the bone mineral content (BMC), bone strength, and femoral neck width of 325 postmenopausal women followed over three years. [Interestingly, this study found that vitamin K2 at this dose range did not improve bone mineral density (BMD).[23]]
For these reasons, vitamin K2 pairs synergistically with vitamin D3, another nutrient that helps calcium get to where it’s needed.[24]
As an additional perk, vitamin K2 may also have anti-cancer properties.[25],[26],[27]
Food sources of vitamin K2
Although vitamin K is found in a variety of foods, we tend to consume vitamin K primarily in the form of vitamin K1 (phylloquinone), which is found in dark, leafy greens and other vegetables.
Vitamin K2 (menaquinone), on the other hand, is found in fermented foods, certain dairy products, and some animal products. Foods especially rich in K2 include:[28]
- Sauerkraut (fermented sauerkraut)
- Natto (a fermented soybean dish from Japan)
- Butter
- Cheese (Munster, camembert, edam, and gouda in particular)
- Beef liver
- Chicken
- Eel
- Egg yolks (ideally from chickens not fed corn or soy)
While it’s typically best to get nutrition from food than from supplements, the consumption of vitamin K2 in the diet has unfortunately decreased gradually since the 1950’s.[29] The modern food manufacturing process further compromises the K2 content of food, and today’s “junk food” contains virtually no vitamin K2. These facts all support the case for K2 supplementation.[30],[31]
In summary
Getting enough vitamin K2 – at least 32 mcg daily – can help keep the blood vessels flexible and strong. By activating matrix GLA protein, vitamin K2 stops calcium from depositing on the walls of the blood vessels. This in turn keeps the vascular system flexible and healthy, and allows calcium to be available for other roles in the body, like improving the health of the bones, nerves, and muscles.
In short, vitamin K2 helps ensure that calcium ends up where it can help us the most – and not where it can cause harm.
References:
Click here to see References[1] Cumming RG, et al. Calcium intake and fracture risk: results from the study of osteoporotic fractures. Am J Epidemiol. 1997;145(10):926-34.
[2] Edwards SL. Maintaining calcium balance: physiology and implications. Nurs Times. 2005 May 10-16; 101(19):58-61.
[3] Bolland MJ, et al. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women’s Health Initiative limited access dataset and meta-analysis. BMJ. 2011 Apr 19; 342():d2040.
[4] Bolland MJ, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ. 2010 Jul 29; 341():c3691.
[5] Xiao Q, et al. Dietary and supplemental calcium intake and cardiovascular disease mortality: the National Institutes of Health-AARP diet and health study. JAMA Intern Med. 2013 Apr 22; 173(8):639-46.
[6] Wang X, et al. Dietary calcium intake and mortality risk from cardiovascular disease and all causes: a meta-analysis of prospective cohort studies. BMC Med. 2014; 12(158). DOI: 10.1186/s12916-014-0158-6.
[7] Pentti K, et al. Use of calcium supplements and the risk of coronary heart disease in 52-62-year-old women: The Kuopio Osteoporosis Risk Factor and Prevention Study. Maturitas. 2009 May 20; 63(1):73-8.
[8] O’Keefe JH. Nutritional strategies for skeletal and cardiovascular health: hard bones, soft arteries, rather than vice versa. Open Heart. 2016 Mar 22;3(1):e000325. DOI: 10.1136/openhrt-2015-000325
[9] Braam LA, et al. Beneficial effects of vitamins D and K on the elastic properties of the vessel wall in postmenopausal women: a follow-up study. Thromb Haemost. 2004;91(2):373-80.
[10] Schurgers LJ, et al. Regression of warfarin-induced medial elastocalcinosis by high intake of vitamin K in rats. Blood. 2007 Apr 1; 109(7):2823-31.
[11] Beulens JW, et al. High dietary menaquinone intake is associated with reduced coronary calcification. Atherosclerosis. 2009 Apr; 203(2):489-93.
[12] Geleijnse JM, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. J Nutr. 2004 Nov; 134(11):3100-5.
[13] Hariri E, et al. Vitamin K 2-a neglected player in cardiovascular health: a narrative review. Open Heart. 2021 Nov;8(2):e001715. DOI: 10.1136/openhrt-2021-001715
[14] Cranenburg EC, et al. The circulating inactive form of matrix Gla Protein (ucMGP) as a biomarker for cardiovascular calcification. J Vasc Res. 2008;45:427–36.
[15] Cranenburg EC, et al. Vitamin K intake and status are low in hemodialysis patients. Kidney Int. 2012;82(5):605–10.
[16] Pilkey RM, et al. Subclinical vitamin K deficiency in hemodialysis patients. Am J Kidney Dis. 2007;49(3):432–9.
[17] Schurgers LJ, et al. The circulating inactive form of matrix gla protein is a surrogate marker for vascular calcification in chronic kidney disease: a preliminary report. Clin J Am Soc Nephrol. 2010;5(4):568–75.
[18] Schlieper G, et al. Circulating nonphosphorylated carboxylated matrix gla protein predicts survival in ESRD. J Am Soc Nephrol. 2011;22(2):387-95.
[19] Geleijnse JM, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. J Nutr. 2004;134(11):3100-5.
[20] Gast GC, et al. A high menaquinone intake reduces the incidence of coronary heart disease. Nutr Metab Cardiovasc Dis. 2009;19(7):504–10.
[21] Beulens JW, et al. High dietary menaquinone intake is associated with reduced coronary calcification. Atherosclerosis. 2009;203(2):489–93.
[22] Akbari S, Rasouli-Ghahroudi AA. Vitamin K and bone metabolism: a review of the latest evidence in preclinical studies. Biomed Res Int. 2018; 2018: 4629383. DOI: 10.1155/2018/4629383
[23] Knapen MH, et al. Vitamin K2 supplementation improves hip bone geometry and bone strength indices in postmenopausal women. Osteoporos Int. 2007;18(7):963-72. DOI: 10.1007/s00198-007-0337-9
[24] van Ballegooijen AJ, et al. The synergistic interplay between vitamins D and K for bone and cardiovascular Health: a narrative review. Int J Endocrinol. 2017; 2017: 7454376. DOI: 10.1155/2017/7454376.
[25] Duan F, et al. Vitamin K2 promotes PI3K/AKT/HIF-1α-mediated glycolysis that leads to AMPK-dependent autophagic cell death in bladder cancer cells. Sci Rep. 2020; 10: 7714. DOI: 10.1038/s41598-020-64880-x.
[26] Duan F. Vitamin K2 Induces mitochondria-related apoptosis in human bladder cancer cells via ROS and JNK/p38 MAPK signal pathways. PLoS One. 2016; 11(8): e0161886. DOI: 10.1371/journal.pone.0161886.
[27] Dragh MA, et al. Vitamin K2 prevents lymphoma in Drosophila. Sci Rep. 2017;7:17047. DOI: 10.1038/s41598-017-17270-9.
[28] Brennan D. Top Foods High in Vitamin K2. Nourish by WebMD [Internet]. October 22, 2020. Accessed January 13, 2022. Available at: https://www.webmd.com/diet/foods-high-in-vitamin-k2#1
[29] Prynne CJ, et al. Intake and sources of phylloquinone (vitamin K(1)) in 4-year-old British children: comparison between 1950 and the 1990s. Public Health Nutr. 2005 Apr; 8(2):171-80.
[30] Maresz K. Proper calcium use: vitamin K2 as a promoter of bone and cardiovascular health. Integr Med (Encinitas). 2015 Feb; 14(1): 34–9. PMID: 26770129.
[31] Theuwissen E. Vitamin K status in healthy volunteers. Food Funct. 2014 Feb; 5(2):229-34.
The information provided is for educational purposes only. Consult your physician or healthcare provider if you have specific questions before instituting any changes in your daily lifestyle including changes in diet, exercise, and supplement use.
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Dr. Erica Zelfand
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