Vitamin D and K: A practical match for the maintenance of normal bones
From autumn to spring days are considerably shorter than in summer and unfortunately very often you don’t see the sun at all. When think of insufficient sun exposure vitamin D comes to your mind, the vitamin commonly known as the sunshine vitamin. But why is that even so? And did you know that you should actually take vitamin K together with vitamin D? We answer these and many other questions here.
What is vitamin D and what is vitamin K?
Both vitamin D and vitamin K are fat-soluble vitamins. That means they are metabolized together with fat to have an effect in the body.
Vitamin D is actually not a vitamin and was falsely classified as such. It is actually a hormone precursor and has hormone-like effects. The vitamin can be subdivided into various calciferols, of which cholecalciferol (vitamin D3) is the active form.
Vitamin K is also not a single vitamin, but a group of various compounds that are involved in the formation of different proteins. Only vitamin K1 (phylloquinone) and vitamin K2 (menaquinone) are important for humans and their metabolism. The name phylloquinone (vitamin K1) is derived from the term chlorophyll, due to the fact that phylloquinone occurs particularly in green plants.
How can we absorb vitamin D and K?
Although both vitamins are fat soluble, they are ingested by the body in very different ways.
Vitamin D is mainly absorbed - namely 80-90% - through endogenous synthesis via the skin. The UV rays of the sun convert cholesterol through various metabolic phases first into previtamin D3 and then into vitamin D3. The smaller part - around 10-20% - of the daily required vitamin D is covered by food. Since vitamin D is not found in so many foods, this is a very beneficial mechanism for the body. If you do want to have more vitamin D in your diet, the best sources are fish, eggs, mushrooms, and avocado. The food with the most content of vitamin D by far, however, is liver oil. Due to this “superfood” there is mainly no vitamin D deficiency in northern countries, even in spite of the low level of sunshine in winter.
Vitamin K2 is only produced by microorganisms and can therefore only be found in animal and fermented foods. It can also be produced in the human intestine by E. coli bacteria. Unfortunately, this production cannot supply the human organism with enough vitamin K2.
Vitamin K1, on the other hand, is only found in different green plants. In general, the greener the plant, the more vitamin K1 it contains. Broccoli, kale, parsley, but also vegetable oils and nuts are particularly good sources of vitamin K. However, you should ensure that foods are stored in the dark, since vitamin K is very sensitive to light.
I have heard of a vitamin D deficiency before, but is there also a vitamin K deficiency?
A vitamin K deficiency is indeed very rare and often only occurs as a side effect of various other gastrointestinal diseases such as Crohn's or celiac disease. Symptoms of a vitamin K deficiency can be tiredness, decreased performance, depressed mood, osteoporosis and broken bones.
A vitamin D deficiency, on the other hand, is more common. The vitamin D produced in summer when there is enough sunlight can be stored in the liver and then supply us during the winter. Different groups should nevertheless keep an eye on their vitamin D status: e.g. people with a darker skin due to the higher melatonin production, seniors with a lower vitamin D synthesis or people with a high body mass index (BMI).
If you think that you could have a deficiency of one of the two vitamins, you should make an appointment for a blood test with your doctor and discuss the exact supplementation with him/her.
What are the effects of the two vitamins in the body?
Both vitamins have different functions in the body and affect the metabolism both individually and together. Vitamin K contributes to normal blood coagulation and the maintenance of normal bone. Vitamin D has many and different functions in the human organism. This includes for example the contribution to the normal function of the immune system, the maintenance of normal muscle function and normal bones and teeth.
Vitamin K has a supporting effect on the positive effects of vitamin D3 by activating proteins such as osteocalcin and matrix-GLA so that they can be used. Osteocalcin is a very important protein in bone mineralization by incorporating calcium into the bones.
Unfortunately, there are not enough studies that confirm the positive synergistic effect of both vitamins and therefore support their joint supplementation. Smaller studies have shown a positive connection between the intake of a vitamin D and K complex, but there are no larger studies to confirm these health-related statements.
How Much Vitamin D and How Much Vitamin K Should I Consume Each Day?
As a healthy adult, one should consume 800 IU, i.e. 20 µg vitamin D3 per day and 60 to 80 µg vitamin K per day. The recommendation for vitamin K can be achieved through a balanced and varied diet, and the recommendation for vitamin D through a 15 to 30-minute sunbath in summer when face, hands and arms are not covered.
Since both vitamins are fat-soluble and cannot be excreted via the urine if consumed too much, overdosing can occur. However, this is only possible due to a high supplement intake and not through food or the sun.
For example, due to a high content of vitamin D3 in the blood by an overdose, vitamin K is only used to provide bone proteins. As a result, it can no longer work properly as a normal blood coagulant and a deficiency can occur despite a sufficient vitamin K level.
Depending on whether you are looking for a complex with both vitamins or an individual supplement with only vitamin D or vitamin K, you will definitely find what you need in our shop.