Do Vitamin D3 And K2 Provide Any Genuine Health Benefits?

  • Lenee CastelynPostgraduate diploma, Public Health, University of Pretoria, South Africa
  • Humna Maryam IkramBS, Pharmacology, University of Dundee, Scotland, UK


Vitamin D3 and K2 are essential micronutrients that perform crucial functions in a surprising range of physiological processes. In particular, their role in bone health has been studied for many years and their importance for bone mass density is well understood. The impact that these vitamins may have on the immune system, and the cardiovascular system and the influence they may have on a patient's mood is less clearly understood.

The supplement industry makes extensive, although general claims that D3 and K2 have noticeable beneficial health effects in these areas. Many patients also report enthusiastically about their own positive experiences with these vitamins. But is this just the result of the placebo effect? Or is there convincing scientific evidence that supports these claims? And what are the positions of the professional bodies? This article aims to provide some answers.1

Understanding vitamin D3 and K2

Vitamins and micro-nutrients are needed by the human body in small quantities. Most vitamins need to be supplemented through our diet as we cannot produce them ourselves. These are known as essential vitamins. We can only produce vitamins D and K which are the only non-essential vitamins. Vitamins can be further divided into water and fat-soluble groups. Although only needed in small amounts, vitamins perform vital functions in fighting infections, wound healing, strengthening of bones and hormone regulation.2

Vitamin D3

Chemically Vitamin D3 is a cholecalciferol, a fat-soluble vitamin that is synthesised in the presence of light in the lower layers of the epidermis of the skin. Fatty fish, egg yolks, and fortified foods also contain Vitamin D3. It performs essential functions in calcium balance and metabolism and is used to treat patients with osteomalacia and rickets.3

Vitamin K2

Chemically vitamin K2 is a fat-soluble menaquinone which is involved in the production of osteocalcin that strengthens bones by creating a protein scaffold. It can be found in fermented foods such as sauerkraut, soybeans, and liver as well as certain cheeses.3

Evaluating the evidence

Bone health

 A considerable number of scientific publications have provided convincing evidence of the benefits of vitamin D3 and K2. Some articles emphasise the synergistic role of both vitamins for bone health and others combine D3 or K2 with calcium. 

Both vitamins are mainly given to older persons and very little is known about potential preventative effects if given to younger individuals. 

Menopausal women and elderly men taking Vitamin D3 with calcium have significantly lower risk of bone fractures. Increased calcium levels were detectable which can cause increased calcification of blood vessels with significantly increased health risks. However, this study did not detect an increased risk of death.4

A large literature review including 95286 patients concluded that Vitamin D3 alone could reduce death in elderly women. One life could be saved for every 150 individuals treated with Vitamin D3 over 5 years. The beneficial effects could clearly be demonstrated at the bone level.5 

Vitamin D3 combined with K2 significantly increases bone mass density and decreases undercarboxylated osteocalcin. Similar results were reported from postmenopausal women in Korea and Japan. Beneficial effects on bone mass density and decreases undercarboxylated osteocalcin were also observed when a combination of vitamin K with calcium was given.6

Cardiovascular health

Vitamin D3 and K2 are mainly given for their well-documented benefits on bone health. Little is known about potential benefits in other areas. At present a clinical study in Denmark examines the expected protective role of taking vitamin D3 and K2 to reduce coronary artery calcification (CAC). CAC is used as a predictor for acute myocardial infarction or heart attack. The theory is that D3 and K2 will slow down the calcification process.7 However, giving patients with advanced heart failure a daily dose of vitamin D of 4000 iu did not reduce mortality but had the negative effect of an increased need for a support mechanical implant.

When K2 was given over 4 years to women aged between 49-70 years a reduced rate of coronary heart diseases was observed. The beneficial impact of K2 on reduced coronary artery calcification was also reported in more recent studies.8

Immune function

There is an increased scientific interest in treatment with vitamin D3 and K2 particularly in areas where deficiencies affect patients' health. Vitamin D can modulate the innate and adaptive immune response. Deficiency in vitamin D is associated with increased autoimmunity and therefore supplementing vitamin D may be beneficialAlthough cells of the immune system have vitamin D receptors, administering additional vitamin D has not led to solid clinical effects in individuals with vitamin D deficiency.9


There is very little evidence that vitamin D2 or K2 has a beneficial influence on the mood of individuals. However, during a 6-month study, vitamin D treatment improved anxiety but not depressive symptoms in depressive patients with low vitamin D.10

The view of the professional bodies

The Royal Society for Osteoporosis recommends taking vitamin D supplements from the end of September to the beginning of April because the winter sun may not be sufficient for vitamin D production. It also warns that taking a higher-than-recommended dose can be dangerous. 

The National Institute for Health and Care Excellence provides detailed medical guidance for the treatment of deficiencies in vitamin D and K.

The Scientific Advisory Committee on Nutrition has published a very comprehensive report on vitamin D and health.

The NHS has published detailed guidance for vitamins and minerals and includes specific recommendations for at-risk groups. It lists foods particularly rich in vitamin D and K and points out that diet or supplements should be the source of vitamin D in the months with limited sunshine.


Does additional vitamin D improve the immune system?

Cells of the immune system have vitamin D receptors. Deficiencies in vitamin D can weaken the immune system and in these cases, additional vitamin D can be beneficial. 

Do vitamin D3 and K2 have benefits for bone health?

Both vitamin D3 and K2 have synergistic benefits for bone mass density and decreases undercarboxylated osteocalcin. Postmenopausal women particularly benefit from taking extra D3 and K2.

Do vitamin D3 and K2 improve the cardiovascular system?

Taking K2 for several years may reduce coronary artery calcification and reduce the incidents of coronary heart diseases in older women.

What are natural sources of vitamin D3?

Fatty fish, red meat, egg yolks, and fortified foods contain Vitamin D3.

What are natural sources of vitamin K2?

Vitamin K2 is synthesised by bacteria and occurs in fermented foods such as sauerkraut and kefir but is also contained in chicken breasts, liver, egg yolks and some cheeses.


Vitamin D3 and K2 provide genuine benefits and are already used to improve bone health in particular for older persons. Both vitamins indicate additional benefits for patients with cardiovascular issues and other deficient areas that may affect the immune system. Thus many of the general claims made by the supplement industry for vitamin D3 and K2 can be verified by scientific publications in particular in the area of bone health. 

Further scientific evidence may provide a more detailed understanding of the underlying mechanisms and optimal dosages. In the future D3 and K2 may provide additional treatment options. Health professionals and organisations have provided guidance and advice based on the available scientific evidence emphasising the importance of vitamin D2 and K3. 

Detailed treatment regimes are available for deficiency conditions. General guidance for food sources of vitamin D3 and K2 and the use of vitamin supplements can be followed. Undoubtedly both vitamins are essential for our well-being and in the future, further treatment options may be added to achieve optimal use of these valuable vitamins.


  1. Avenell A, Mak JC, O'Connell D. Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men. Cochrane Database Syst Rev. [Internet] 2014 [cited 2024 March 1];2014(4):CD000227.Available at: 
  2. Bjelakovic G, Gluud LL, Nikolova D, Whitfield K, Wetterslev J, Simonetti RG, Bjelakovic M, Gluud C. Vitamin D supplementation for prevention of mortality in adults. Cochrane Database Syst Rev. [Internet] 2014 [cited 2024 March 1];(1):CD007470. Available at
  3. Kuang X, Liu C, Guo X, Li K, Deng Q, Li D. The combination effect of vitamin K and vitamin D on human bone quality: a meta-analysis of randomized controlled trials. Food Funct. [Internet] 2020 [cited 2024 Feb 29];11(4):3280-3297. Available at:  
  4. Je SH, Joo NS, Choi BH, Kim KM, Kim BT, Park SB, Cho DY, Kim KN, Lee DJ. Vitamin K supplement along with vitamin D and calcium reduced serum concentration of undercarboxylated osteocalcin while increasing bone mineral density in Korean postmenopausal women over sixty-years-old. J Korean Med Sci. [Internet] 2011 [cited 2024 Feb 28];26(8):1093-8. Available at:  
  5. Iwamoto J, Takeda T, Ichimura S. Treatment with vitamin D3 and/or vitamin K2 for postmenopausal osteoporosis. Keio J Med. [Internet] 2003 [cited 2024 March 1];52(3):147-50. Available at: 
  6. Hu L, Ji J, Li D, Meng J, Yu B. The combined effect of vitamin K and calcium on bonemineral density in humans: a meta-analysis of randomized controlled trials. J Orthop Surg Res. [Internet] 2021 [cited 2024 Feb 26];16(1):592. Available at:
  7. Hasific S, Øvrehus KA, Hosbond S, Lambrechtsen J, Kumarathurai P, Mejldal A, Ravn EJ, Rasmussen LM, Gerke O, Mickley H, Diederichsen A. Effects of vitamins K2 and D3 supplementation in patients with severe coronary artery calcification: a study protocol for a randomised controlled trial. BMJ Open. [Internet] 2023 [cited 2024 Feb 29] ;13(7):e073233. Available at:
  8. Gast GC, de Roos NM, Sluijs I, Bots ML, Beulens JW, Geleijnse JM, Witteman JC, Grobbee DE, Peeters PH, van der Schouw YT. A high menaquinone intake reduces the incidence of coronary heart disease. Nutr Metab Cardiovasc Dis. [Internet] 2009 [cited 2024 March 1];19(7):504-10. Available at:
  9. Vossen LM, Schurgers LJ, Van Varik BJ, Kietselaer BLJH, Vermeer C, Meeder JG, Rahel BM, Van Cauteren YJM, Hoffland GA, Rennenberg RJMW, et al. Menaquinone-7 Supplementation to Reduce Vascular Calcification in Patients with Coronary Artery Disease: Rationale and Study Protocol (VitaK-CAC Trial). Nutrients. [Internet] 2015 [cited 2024 Feb 27]; 7(11):8905-8915. Available at:    
  10. Aranow C. Vitamin D and the immune system. J Investig Med. [Internet] 2011 cited 2024 Feb 28];59(6):881-6. Available at:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Helge Peter Vogt

PhD in Biology, University of Essen

MSc in Analytical Genomics, Birmingham University

Helge is a marine biologist who monitored coral reefs in the Indo-Pacific and provided scientific support for the establishment of marine reserves. He also developed an interest in analytical genomics of rare autosomal recessive diseases caused by consanguinity. For many years he has been teaching biology courses to a range of classes.

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