Vitamins D and K are naturally produced by our bodies in small amounts. They are very important for supporting bone health, immune function, and absorption of minerals from the gut. But do they work better if you take them together as D3+K2, and why? Keep reading this article to find out.
What is vitamin D3?
Vitamin D is a fat-soluble vitamin that is naturally found in foods such as fatty fish, dairy products, and eggs. However, vitamin D is mainly synthesized by the human skin when exposed to sunlight. This kind of vitamin D is called cholecalciferol or vitamin D3. It plays important roles in:
- calcium absorption from the gut,
- supporting bone health and density,
- enhancing immune function,
- regulating mood and energy levels.
Vitamin D is one of those vitamins that you can easily have a deficiency of. In the wintertime, or in some places that don't get much sunlight, your skin won't be able to synthesize vitamin D3. The same is true when you're getting older, especially if you go through menopause. Declining estrogen levels during that time can worsen calcium absorption, which you need to keep your bones dense and healthy. For adults aged 65 and older, a daily intake of 800 to 1,000 IU of vitamin D3 is recommended to prevent deficiency and reduce the risk of fractures and falls (1).
In those cases, you can still make sure that you get enough vitamin D3 through food and vitamins. This is where the D3+K2 vitamins come in.
What is vitamin K2?
Vitamin K is not as famous as vitamin D, but it is an equally important nutrient. Vitamin K is a fat-soluble vitamin that also exists in multiple forms, just like vitamin D. There are two main forms, vitamin K1 and K2.
Vitamin K1 or phylloquinone is primarily found in leafy green plants, and it makes up the most of all the vitamin K consumed by us. Vitamin K2 or menaquinone is primarily produced by bacteria in our gut, and it can also be found in fermented food, cheese, and meat sources like beef and chicken. There are different forms of K2, with MK-7 being the most effective and bioavailable (2).
Vitamins of the K group work by activating proteins that control blood clotting and where calcium goes in the body. Its key roles in your body include:
- directing calcium to bones and teeth,
- preventing calcium from building up in arteries and soft tissues,
- supporting heart health and reducing arterial stiffness.
Out of the two kinds of vitamin K, K2 is the better absorbed one, and it circulates in the blood much longer. While only about 10% of K1 gets absorbed and can stay in the blood for a few hours, K2 can stay in the blood for a couple of days. This is also the reason why it's a preferred option to take as a supplement (3).
If you want to know more about the science of supplement bioavailability, read our other articles:
- Bioavailability of Supplements – Meaning and Importance
- How does our diet influence the bioavailability of supplements?
- Is it more effective to get active ingredients through food or supplements?
Why is D3 often paired with K2?
Taking vitamin D3 without K2 may increase calcium absorption, but if there's no vitamin K2 to guide that calcium, it can end up in the wrong places, like arteries, kidneys, and joints. This is the most important reason why you should take them together. Find a more detailed explanation below.
