The synergistic benefits of vitamins D3 and K2

by Hannah de Gruchy February 02, 2023

The synergistic benefits of vitamins D3 and K2

Vitamins D and K are both fat-soluble vitamins that have individual roles within the body, as well as working together to regulate calcium levels – calcium is important for the health and strength of our bones. Therefore, it’s essential that we have a sufficient intake of both vitamins to protect our bone health.

However, it isn’t always possible to get enough of each vitamin, and this has led vitamin manufacturers to develop supplements that contain both vitamin D and vitamin K.

Vitamins D3 and K2: fast facts

  • There are two main types of vitamin D and vitamin K – vitamin D2/3 and vitamin K1/2.
  • Most vitamin D and K supplements contain vitamins D3 and K2 as they’re considered the most beneficial.
  • Both vitamins have individual roles but are both equally important in the health of our bones.
  • Vitamin D regulates the level of calcium in the blood and bones.
  • Vitamin K helps to store calcium in the bones where it’s beneficial and prevents it building up in the blood vessels where it can be dangerous.

What is vitamin D3 and why do we need it?

Vitamin D is different from most other vitamins in that most of our intake isn’t from our diet. Instead, our body manufactures most of our vitamin D when we expose our skin to UV light from the sun. This explains why it’s often referred to as the sunshine vitamin. There are some food sources of vitamin D, including liver, egg yolks, oily fish, and mushrooms.

Knees bones and hips

Along with vitamins A, E and K, vitamin D is a fat-soluble vitamin, meaning that the body requires fats and oils in the diet to absorb it. (Conversely, the B vitamins and vitamin C are water soluble vitamins since they require water to be absorbed.)

The primary role of vitamin D is to keep our bones strong. A vitamin D deficiency can lead to bone deformities in children (a condition called rickets) and bone pain or soft bones (osteomalacia) in adults. We also need vitamin D to maintain healthy teeth and muscles and to support good mental health.

There are two types of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol). They perform similar roles, with D2 being found primarily in mushrooms and D3 in animal-based foods such as liver, eggs, and fish.

Most vitamin D supplements contain vitamin D3, as its bioavailability (the amount that can absorbed into the bloodstream and utilised) is higher. Many D3 supplements are made using lanolin, the natural oil derived from sheep’s wool, and are therefore not suitable for vegetarians and vegans. However, there are now D3 supplements that have been made using vegetarian and vegan-friendly algae and lichen.

What is vitamin K2 and why do we need it?

High strength vitamin K2 - fermented foods
Like vitamin D, vitamin K is a fat-soluble vitamin, but it isn’t as well-known as most of the other vitamins. Technically, vitamin K is a group of vitamins, the most common being vitamins K1 and K2. Vitamin K1 (phylloquinone) is found primarily in green, leafy vegetables and K2 (menaquinone) is found mostly in animal-based foods as well as fermented foods, in particular a Japanese fermented soya bean dish called natto.

Vitamin K2 can be further divided into two subtypes called MK-4 (menaquinone-4) and MK-7 (menaquinone-7). Animal-based foods such as liver, cheese and egg yolks tend to contain MK-4, whilst fermented foods like natto, kimchi and sauerkraut contain MK-7. The bacteria in our gut also produce MK-7.

We need vitamin K for normal blood clotting and wound healing. Like vitamin D, it also plays a major role in bone health. There is ongoing research into the similarities and differences between vitamins K1 and K2. Some researchers believe that they should be classified as separate vitamins.

What is known, is that in studies where participants have been given vitamin K supplements, K2 consistently helps to improve bone health, while K1 appears to offer no significant benefit. For this reason, most vitamin K supplements contain vitamin K2.

How do vitamins D3 and K2 work together for bone health?

These two important vitamins work together to protect bone health by continually regulating the level of the mineral calcium that enters and leaves the bones.

Family wellbeing - mother and child

Calcium is essential for maintaining bone tissue and strength, and vitamin D helps to support the absorption of the calcium from our diet into our bloodstream to be used in our bones. If we have a plentiful intake of calcium, vitamin D will ensure it is stored in our bones.

However, calcium has many other roles in the body, such as dental health, muscle contraction, heart health, hormone production and nerve signalling. If we don’t consume enough calcium in our diet, the body has no choice but to take it from the largest calcium reserve – our bones. Vitamin D assists in this process, even though if we’re deficient in calcium long term, it could lead to brittle bones, fractures, and osteoporosis.

The role of vitamin D is to make sure we have enough calcium, but it doesn’t solely control where this calcium ends up. Vitamin K does most of this work by activating two proteins that manage calcium reserves – osteocalcin and matrix GLA protein.

Osteocalcin promotes the calcification of the bone, in other words, the accumulation of calcium in the bones. Matrix GLA protein prevents the accumulation of calcium in the blood vessels and tubes within the kidneys. This is important because if calcium is allowed to build-up in the blood vessels and kidneys, it can lead to heart and kidney disease.

Therefore, there’s a synergistic relationship between vitamin D and vitamin K involving the regulation of calcium, and where it’s stored, and not stored, in the body. This benefits the health of our bones and helps to protect the health of our blood vessels.

Should I take vitamins D3 and K2 at the same time?

Since vitamins D3 and K2 both play a role in bone health, they’re often found in supplements together and it makes sense to take them at the same time.

Doing so helps to ensure that the calcium in the blood is transported to the bones by vitamin D and isn’t allowed to dangerously build up in the blood vessels, a role played by vitamin K2.

There are no known serious side effects to taking these two vitamins together.

How to supplement with vitamins D3 and K2

Vitamin D3 and K2 - happy family
It’s recommended that adults take at least 10µg (microgram) of vitamin D per day during the winter months when we’re exposed to less sunlight. It’s entirely safe to take vitamin D all year round, and it’s recommended that we do so if we cover our skin for religious or cultural purposes, or we don’t spend much time outside due to illness, disability, or incarceration. Daily vitamin D supplements are also recommended for those who don’t consume animal products.

Adults require around 1µg of vitamin K per kilo of bodyweight. For example, if we weigh 60kg, we’d need 60µg of vitamin K.

If you’re in doubt about your intake of either vitamin, a supplement that contains enough of both for most adults is a good idea. Vitamin D3 and K2 capsules from G&G Vitamins contain 100µg of vitamin D3 and 200µg of vitamin K2 per capsule. If you prefer a liquid version, we also retail BioBloom's Vitamin D3 and K2 with hemp oil, which provides 20µg of vitamin D3 and 75µg of vitamin K2 in a 4-drop serving. They’re both suitable for vegetarians and contain no gluten, lactose, or soya.

As with all food supplements, you may need to take them daily for at least three months before you notice any benefits. Supplementing your diet with these vitamins as part of a healthy lifestyle can help to give you peace of mind that you’re doing all you can to support your health and wellbeing.

BioBloom Vitamin D3 & K2 with Hemp Oil

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Hannah de Gruchy
Hannah de Gruchy


Health and wellness author and biologist specialised in sustainability, nutrition and eco-living.

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