While all vitamins are essential in maintaining a healthy lifestyle, vitamin D carries an especially important role in the body. Yielding a multitude of benefits, it promotes the intestinal absorption of calcium and phosphorus, aids in bone mineralization and impacts the immune system. Vitamin D acts like a transcription factor that influences central mechanisms of tumorigenesis: growth, cell differentiation, and apoptosis (programmed cell death). More often than not, you hear the term “vitamin”, when, in retrospect, vitamin D acts as more of a hormone.

It occurs in two major forms:

  1. Vitamin D2: ergocalciferol; stemmed from commercially ultraviolet irradiated plant sterol ergosterol. It can also be obtained via fortified foods and nutritional supplements.
  2. Vitamin D3: cholecalciferol; originating from a number of fatty animal foods and made internally when exposed to ultraviolet rays from the sun. More specifically, by the action of sunlight on the precursor 7-dehydrocholesterol in the skin (11).

Vitamin D2 and D3 are both precursors to the final, metabolically active format. The first step towards the final version in the body is hydroxylation in the liver which forms 25(OH)D, or calcidiol. The second step is hydroxylation within the kidneys and this constitutes the most biologically active hormone form, Vitamin D 1,25(OH)2D, or calcitriol.

Functions of Vitamin D

The major function for Vitamin D, once metabolized in the kidneys to calcitriol is to keep calcium and phosphorus (key minerals for bone health) concentrations adequate for essential cellular functions and bone mineralization. Over 99 percent of calcium is stored in the bulk of our bones and the relationship between phosphorus and Vitamin D helps in the effective absorption of calcium. Studies in older adults show an increase in yearly bone fractures due to Vitamin D deficiency along with metabolic bone disease. Not only does the deficiency also cause osteomalacia, but can also aggravate osteoporosis (4).

Other benefits:

  • Beneficial for muscle function and performance.
  • Studies have shown it plays a role in controlling blood pressure and preventing artery damage. (7)
  • Potential cancer-fighting benefits (3).
  • Regulation of the immune system.

Vitamin D deficiency has been linked to a number of different health concerns. While the exact reasons as to why that is, is being researched to this day, it has been discovered that individuals who are vitamin D deficient of more prone to infections, cardiovascular diseases and mental disorders like depression.

Vitamin K and its Specific Distinction to Vitamin K2

Vitamin K belongs to a group of fat soluble vitamins, like Vitamin D3. Also like Vitamin D, it is present in certain foods and is available as a dietary supplement. Formed from two compounds; Vitamin K1: Phylloquinone, which is primarily found in plants. When ingested, bacteria in the large intestine convert it into the compound Vitamin K2: Menaquinone. It is found in fermented foods and animal products. It has several subtypes called menaquinones (MKs) that are named by the length of their side chain and range from MK-4 to MK-13 (6).

Vitamin K is required as a factor in the process of the gamma-carboxylation of several Vitamin-K dependent proteins turning inactive uncarboxylated proteins into active carboxylated forms to confer functioning. The most well-known vitamin-K dependent proteins are prothrombin and factor X; hepatic coagulation factors. 

Especially important in cardiovascular health is the matrix GLA protein (MGP). It is a small extracellular matrix protein synthesized in smooth muscle that binds calcium ions in the vascular wall and protects against vascular calcification(10). Simply put, Vitamin K2 may prevent calcification and hardening of the cardiovascular system.

Vitamin K and Heart Health

Especially important in cardiovascular health is the matrix GLA protein (MGP). It is a small extracellular matrix protein synthesized in smooth muscle that binds calcium ions in the vascular wall and protects against vascular calcification(10). Specifically, vitamin K2 helps by preventing the calcium from depositing into the arteries.  Vascular calcification leads to arterial stiffening, elevated systolic pressure and an increase in the cardiac workload.

The Synergistic Relationship Between Vitamin K2 and D3

Given high doses of Vitamin D3, like many things taken into abundance can be harmful to the body. High doses of cholecalciferol, when given to rodents in recent studies would cause excessive calcium uptake, deposition and interference with regular cardiac and renal functions (10). With the correct use of the conjunction of D3 with K2, the issue of “metastatic calcium” is avoided. Through a chemical step called carboxylation, Vitamin K balances the coagulation system entirely. Carboxylation of osteocalcin also aids in proper bone mineralization and in keeping a strong bone matrix. While ready to clot when excessive bleeding occurs, it also allows the prevention of clotting if it is unnecessary.

Why They are so Good Together

As previously noted, while Vitamin D3 helps support your cardiovascular health by ensuring that you have the appropriate levels of calcium in your blood, vitamin K2 helps to direct that calcium to where it is supposed to go. Therefore, vitamin D3 will help with your absorption and vitamin K2 is the nutrient that helps your bones use that calcium effectively and helps prevent cardiovascular diseases (5). Through its activation of the protein osteocalcin, Vitamin K helps to bind newly absorbed calcium to the mineral matrix in bone. All in all, vitamin D3 and K2 not only share similar qualities, but also act synergistically within the body (9).

orthomolecular vitamin d3 k2

How Vitamin K2 with D3 Should be Ingested for Proper Absorption

The most widely studied form of vitamin K2 is MK-7. It is a “super nutrient” in a way that it provides bone health without the toxicity of other drugs used for the aiding of the bones. Also, recent clinical studies and research have been extremely encouraging in regards to how well this form works for the body. Our office offers Vitamin K2 with D3, an Orthomolecular Products company supplement. With 45 mcg of MenaQ7 PRO and 5,000 IU of vitamin D3 per capsule for optimal absorption and use (9).

Consuming products like the one stated above with a source of fat such as olive oil will aid in the absorption process. Remember, both vitamin K2 and D3 are fat-soluble.

Natural Food Sources of Vitamin D

Plant Sources (Vitamin D2)

1. Mushrooms

Asides from fortified sources such as fortified orange juice, almond milk or tofu, mushrooms are really the only realistic source of non-animal Vitamin D(2).

Animal Sources (Vitamin D3)

1. Wild Salmon

Already a superstar for its’ high Omega-3 fatty acids, wild salmon is also very high in Vitamin D. We recommend only wild caught salmon and suggest you avoid farmed salmon. Wild salmon is higher in both omegas and vitamin D with the a 100g serving boasting up to 1,300iu in some cases

2. Cod Liver Oil

Again, another heavy hitter in the Omega-3 fatty acid is also an excellent source of Vitamin D3. Caution should be made when consuming large quantities of Cod Liver Oil since it also contains Vitamin A which could accumulate to toxic levels. One teaspoon yield approximately 450iu or 75% of the RDA.

3. Oysters

Like a multi-vitamin, but tastier, Oysters are a micronutrient powerhouse containing B12, and trace-nutrients such as copper and zinc. Add a little lemon juice and get a dose of Vitamin C as well!  The typically 100g serving of oysters has less than 70 calories but 320iu of Vitamin D3

In Closing

There are many ways to get your doses of Vitamin D. Mushrooms, deep-water fish, supplements and good ‘ole sunshine. Remember that you can also superload on Vitamin D to boost your low levels and your body will keep it as a reserve for when it needs it. Do you know what your Vitamin D levels are?


  1. (2017, November). https://www.health.harvard.edu/staying-healthy/taking-too-much-vitamin-d-can-cloud-its-benefits-and-create-health-risks.
  2. 2.Anarson, A. (2018, March). https://www.healthline.com/nutrition/vitamin-d2-vs-d3#section5.
  3. CF, G. (2009, July). https://www.ncbi.nlm.nih.gov/pubmed/19523595?dopt=Citation.
  4. Department of Medicine, B. U. (1996, April). https://www.ncbi.nlm.nih.gov/pubmed/8642450.
  5. HumanN. (2018, April). Vitamin D3 and K2: The Perfect Pair for Strong Bones. Retrieved from https://www.humann.com/nutrition/powerful-combo-vitamins-d3-k2/
  6. Keith Pearson, P. R. (2017, September). Vitamin K1 vs K2: What’s the Difference? Retrieved from Healthline: https://www.healthline.com/nutrition/vitamin-k1-vs-k2#section6.
  7. LD, M. W. (2018, January ). https://www.medicalnewstoday.com/articles/219867.php.8.
  8. MF, H. (2008). Department of Medicine, Section of Endocrinology, Nutrition, and Diabetes, Vitamin D, Skin and Bone Research Laboratory, Boston University Medical Center. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/8642450.
  9. Products, O. (n.d.). Vitamin K2 with D3. Retrieved from https://www.orthomolecularproducts.com/file.aspx?DocumentId=244
  10. Ron Hunninghake, M. (2013). https://riordanclinic.org/2013/10/vitamins-d3-and-k2-the-dynamic-duo/.
  11. Services, U. D. (2018, September). https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/.
  12. Sizar, O., & Givler, A. (2019, March). https://www.ncbi.nlm.nih.gov/books/NBK532266/.