Why You Need to Combine Vitamin D3 with Vitamin K2 to Support Bone Health With Age

Commonly dubbed the “sunshine vitamin,” vitamin D3 is produced in our skin after exposure to UVB rays from the sun. But getting enough isn’t always as easy as it sounds, with factors like sunscreen usage, increasing amounts of time spent indoors, the latitude where you live, and skin color all playing a role in how much vitamin D we can make from sunshine.  

Although the benefits of vitamin D are wide-reaching—ranging from better mood to respiratory function to gut health—it’s best known for its role in strengthening bones. However, vitamin D doesn’t work alone—it needs vitamin K2 to complete the job. While you can certainly take these two supplements separately, a combination—like that found in ProHealth Longevity’s D3 + K2 capsules—can cover all of your bone-building bases. 

Vitamin D3

The most easily accessible source of vitamin D is sunshine, as just a handful of foods naturally contain the vitamin, including fatty fish (like salmon, mackerel, and tuna), cod liver oil, some mushrooms, egg yolks, and some dairy products. 

However, vitamin D supplements are often a smart choice to achieve optimal levels because food sources are not very high in vitamin D—for example, one egg contains just 44 IU (International Units) of vitamin D, while supplements commonly contain 4,000-6,000 IU.

Benefits of Vitamin D

• Bone Health: Vitamin D regulates the activity of phosphorus and calcium—two nutrients necessary for proper bone mineralization. With age, insufficient vitamin D can cause bone softening, loss of bone mineral density, and fractures. Research shows that each 10 ng/mL decrease in serum vitamin D levels is associated with a 33% increased risk of hip fracture in postmenopausal women.
• Immune System Support: Vitamin D plays a role in the innate immune response, which provides the first line of defense against invading pathogens. It helps to enhance the production of antimicrobial compounds and other defensive immune cells, as well as strengthen cells’ physical barrier function to keep pathogens out. In one meta-analysis, people who took vitamin D supplements had a 19% reduced risk of developing infections in the respiratory tract. 
• Mood Support: The therapeutic use of sunshine or light therapy for mood disorders has been used for centuries. Although the sun has benefits above and beyond vitamin D, studies show that vitamin D supplements significantly improve mood and mental health conditions.
• Heart Health Support: Vitamin D supports heart health by ensuring calcium doesn’t build up (or calcify) in vascular tissue—which it needs vitamin K2 to do. It may also support healthy blood pressure and glucose metabolism. 

Vitamin K2

Vitamin K2 is a collection of compounds known as menaquinones, with the most vital forms being MK-4 and MK-7. MK-4 is found only in certain animal foods, while MK-7 is more abundant in fermented foods because bacteria synthesize it. Of the menaquinones, MK-7 is best able to reach the bones and liver, while MK-4 works most efficiently on other tissues, like the heart. 

Although vitamin K1 is found widely in leafy green vegetables, vitamin K2 is a little harder to find, with the top vitamin K2-rich foods being liver and natto (fermented soybeans). Other lesser-containing vitamin K2 foods include egg yolks, grass-fed butter, dark meat chicken, and some hard cheeses like Jarlsberg, Swiss, and Münster. 

Benefits of Vitamin K2

One of the most important roles of vitamin K2 is inhibiting calcium from settling in areas it shouldn’t, like blood vessels and kidneys, where calcification is not a good thing. Instead, vitamin K2 helps shuttle calcium to where it needs to be: the bones and teeth.

• Strengthens Bones: The bone-strengthening role of vitamin K2 was uncovered alongside the discovery of osteocalcin—a protein that requires vitamins D3 and K2 to direct calcium out of the bloodstream and into the bones, where it can increase bone mineral density. 

• Supports Dental Health: The vitamin K2-dependent osteocalcin also increases dentin production, which is the tissue under the tooth’s enamel that prevents cavity formation. Due to its ability to take calcium from the bloodstream and deposit it into teeth, vitamin K2 can slow down the tooth loss that is common with age.

• Supports Heart Health: Another protein reliant on vitamin K2 is matrix GLA protein, which inhibits calcium deposition on arterial walls. As calcified arteries lead to narrowing blood vessels and heart conditions, inhibiting this process is beneficial to cardiovascular health. 

These benefits can be enhanced even further when combined with vitamin D, as these two vitamins work synergistically. As an important side note, people taking blood thinners and certain other medications need to avoid vitamin K supplements, as the vitamin significantly alters the effects of these drugs. 

Why You Need to Combine D3 and K2

While both vitamin D3 and K2 are beneficial on their own, they are a dynamic duo when it comes to bone and heart health. 

Vitamin D3 has the first job, directing dietary or supplemental calcium from your intestines into the bloodstream. Then, vitamin K2 is vital for finishing the job, as it takes that calcium away from the blood and into your bones and teeth. Without enough K2, calcium can stay in the bloodstream or travel to places we don’t want it—like calcifying in arteries and vascular tissue and causing heart issues.

Therefore, it’s important to supplement with both vitamin D3 and K2—especially if you take supplemental calcium. 

The ProHealth Advantage

ProHealth Longevity’s D3 + K2 capsules contain the ideal amount of both vitamins to support bone and cardiovascular health. In this supplement, you’ll find:

• 5,000 IU (125 mcg) of Vitamin D3
• 100 mcg of Vitamin K2 (MK-7)
• 2.5 mg of Bioperine, which helps to facilitate absorption 

Plus, ProHealth adheres to Good Manufacturing Practices (GMPs)—ensuring consistency in purity and potency in each batch—and undergoes third-party testing by organizations like NSF International or USP (United States Pharmacopeia).

With ProHealth’s D3 + K2 supplement, you can trust that you’re getting the right amount of both vitamins to support strong bones at any age.

Reviewed by: Heather L. Makar

References: 

Bolland MJ, Grey A, Avenell A, Gamble GD, Reid IR. 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;342:d2040. Published 2011 Apr 19. doi:10.1136/bmj.d2040

Cauley JA, Lacroix AZ, Wu L, et al. Serum 25-hydroxyvitamin D concentrations and risk for hip fractures. Ann Intern Med. 2008;149(4):242‐250. doi:10.7326/0003-4819-149-4-200808190-00005

Halder M, Petsophonsakul P, Akbulut AC, et al. Vitamin K: Double Bonds beyond Coagulation Insights into Differences between Vitamin K1 and K2 in Health and Disease. Int J Mol Sci. 2019;20(4):896. doi:10.3390/ijms20040896

Marino R, Misra M. Extra-Skeletal Effects of Vitamin D. Nutrients. 2019;11(7):1460. doi:10.3390/nu11071460

Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583. doi:10.1136/bmj.i6583

Nair R, Maseeh A. Vitamin D: The "sunshine" vitamin. J Pharmacol Pharmacother. 2012;3(2):118‐126. doi:10.4103/0976-500X.95506

Spedding S. Vitamin D and [mood]: a systematic review and meta-analysis comparing studies with and without biological flaws. Nutrients. 2014;6(4):1501-1518. Published 2014 Apr 11. doi:10.3390/nu6041501