Calcium metabolism and bones. The role of cooperating components
The phenomenon commonly called the calcium paradox[1] concerns a specific metabolic situation. In it, a low bone mineral density is observed. At the same time, calcium compounds accumulate in soft tissues[2]. Understanding the physiology of this process matters for anyone who wants to compose their diet consciously. Supplying calcium to the body is important, but it requires the presence of the right cofactors, thanks to which this component reaches the bone tissue.
The cooperation of magnesium, vitamin D3 and K2
Calcium is needed for the maintenance of normal bones. For the process of its absorption and use to proceed properly, the body uses several components:
- Calcium is the basic building material of bones and teeth.
- Magnesium contributes to normal muscle function and to the normal functioning of the nervous system. It is also important for the metabolism of vitamin D, because the enzymes that convert vitamin D into its active form are magnesium dependent.
- Vitamin D3 contributes to the normal absorption and utilisation of calcium and phosphorus from the digestive tract.
- Vitamin K2 (especially menaquinone-7, that is MK-7) contributes to the maintenance of normal bones. It takes part in the activation of vitamin K dependent proteins, which are involved in calcium metabolism.
Vitamin K dependent proteins perform important functions in the body. This vitamin takes part in the activation of osteocalcin, a protein that binds calcium in the bone matrix.
How vitamin K dependent proteins work
Vitamin K2 takes part in the carboxylation of specific proteins, which is important for their biological activity. Two important proteins in this process are:
- Osteocalcin. This is a protein produced by bone forming cells. Vitamin K takes part in its activation, and osteocalcin binds calcium in the bone matrix.
- MGP (Matrix Gla Protein). It occurs among other places in the walls of blood vessels. Scientific research indicates that the activity of this protein is dependent on an adequate supply of vitamin K.
The scientific literature, including the well known Rotterdam Study[3], describes a correlation between the dietary intake of natural vitamin K2 and the functioning of the circulatory system. This is an epidemiological observation, which the authors treat as a premise for further analysis, not as proof of a causal relationship.
Natto and fermented soy in the diet
When looking for sources of vitamin K, it is worth paying attention to the traditional Japanese diet. Natto, that is fermented soy, is among the richest dietary sources of vitamin K2 in the MK-7 form. This form is characterised by good bioavailability.
Natto also contains nattokinase. This is a proteolytic enzyme formed during fermentation with the bacterium Bacillus subtilis natto. In laboratory studies (in vitro) its activity towards fibrin has been described. Results obtained in a test tube do not automatically translate into effects in humans, and in the European Union nattokinase has no authorised health claim. Natto is a valued part of traditional, fermented food.
How to care for proper calcium metabolism
It is worth approaching bone care holistically:
- A balanced diet. It should include calcium, magnesium and vitamins D and K from various sources.
- Valuable sources. Include fermented products in the menu, such as dried natto. They provide nutrients in a natural form.
- Regular tests. Monitor the level of vitamin D and calcium in the blood, to match the diet and any supplementation to individual needs.
Important safety information
Products rich in vitamin K and nattokinase may affect clotting processes.
- Interactions with medicines. If you take anticoagulant medicines (both vitamin K antagonists and newer generation medicines) or antiplatelet medicines, consuming natto or supplementing with vitamin K2 requires consultation with your treating doctor.
- Planned procedures. Before planned operations it is worth informing the doctor about a diet rich in natto, because of the high vitamin K content, which affects the action of anticoagulant medicines.
Would you like to enrich your diet
Take a look at our range of natto and vitamin K2 MK-7 at natto.pl. A balanced diet and a healthy lifestyle are the basis for the normal functioning of the body. If in doubt, consult a doctor or dietitian.
The Natto.pl team
The content on the Natto.pl blog is created by enthusiasts of healthy eating in cooperation with food technologists. We base each article on scientific publications and food safety standards, in order to provide reliable knowledge about fermented soy.
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Sources: This article is based on 1 observational clinical study and 2 review papers
Last update: 29.12.2025
Purpose: The material is educational in nature and does not replace medical advice
Scientific bibliography and discussion of the studies
- Explanation of the “calcium paradox” mechanism:Maresz K., Proper Calcium Use: Vitamin K2 as a Promoter of Bone and Cardiovascular Health, Integrative Medicine: A Clinician’s Journal, 2015. The review paper discusses the role of vitamin K dependent proteins in calcium metabolism. The author describes that the activation of these proteins depends on an adequate supply of vitamin K2. Link to the study
- Confirmation of the biological link between bones and vessels:Demer L.L., Tintut Y., Vascular calcification: pathobiology of a multifaceted disease, Circulation, 2008. This study describes the so called bone vascular axis. The authors indicate that the loss of minerals from bones and their deposition in arteries are related biological processes. Link to the study
- Observational study (the Rotterdam Study):Geleijnse J.M. et al., Dietary Intake of Menaquinone Is Associated with a Reduced Risk of Coronary Heart Disease: The Rotterdam Study, The Journal of Nutrition, 2004. An observational study covering more than 4,800 people. It described a correlation between a high dietary intake of natural vitamin K2 and less aortic calcification in the studied population. This is a correlation, not proof of a causal relationship. Link to the study
