Vitamin D3 & K2: Science and Effects

  • Der Schriftzug 'Vitamin D3' aus weißen Kapseln auf gelbem Hintergrund

    The science behind vitamin D3 and vitamin K2

    Vitamin D3 (cholecalciferol) and vitamin K2 (menaquinone) are both fat-soluble vitamins whose interplay has increasingly become a focus of nutritional science in recent years. While the body can produce vitamin D3 in the skin itself given sufficient UVB sunlight, endogenous production is insufficient for a large part of the population in northern latitudes, particularly during the autumn and winter months. Similar to other essential nutrients, vitamin K2 must be supplied regularly through the diet, as endogenous production by the intestinal flora alone is usually not enough.

  • Tafel mit der Aufschrift 'Vitamin K' umgeben von Kürbiskernen, Kiwi, Karotten, Erbsen, weißen Bohnen und grünem Gemüse

    Vitamin D3 and Vitamin K2 at a glance

    Vitamin D3 (cholecalciferol): the form of vitamin D that is produced in skin exposed to sunlight or absorbed through fatty fish, egg yolks, and fortified foods. It is converted in the liver and kidneys into its biologically active form.

    Vitamin K2 (menaquinone): occurs in various sub-forms, including short-chain MK-4 and long-chain MK-7, which is derived from fermented foods like natto or produced synthetically and is characterized by a significantly longer residence time in the blood.

    Calcium: not a vitamin, but the central mineral whose absorption and storage is regulated by the interaction of D3 and K2.
  • Röntgenbild-Darstellung eines Kniegelenks mit rot markiertem Bereich, zwei Hände umfassen das Knie

    Bone metabolism and calcium homeostasis

    The relationship between vitamin D, vitamin K, and bone metabolism is one of the best-documented areas of activity for both vitamins. The European Food Safety Authority (EFSA) has confirmed that vitamin D contributes to the normal absorption and utilization of calcium and phosphorus, to the maintenance of normal blood calcium levels, and to the maintenance of normal bones and teeth. Vitamin K, in turn, contributes to the maintenance of normal bones, according to the EFSA.

    At the cellular level, both vitamins complement each other: vitamin D increases the absorption of calcium from the intestine into the blood, while vitamin K2 acts as a cofactor for the carboxylation of osteocalcin—a protein that actively incorporates free calcium into the bone matrix.

  • Rückenansicht einer Frau mit erhobenem, muskulös definiertem Arm vor braunem Hintergrund

    Muscle, immune, and cell function

    In addition to bone metabolism, vitamin D is involved in other physiological processes. The EFSA has confirmed that vitamin D contributes to the maintenance of normal muscle function, the normal function of the immune system, and the normal process of cell division. Furthermore, in older people with impaired stability and muscle weakness, a contribution of vitamin D to the reduction of the risk of falling has been scientifically recognized.
  • Tic-Tac-Toe-Muster aus weißen Kapseln und Orangenspalten auf hellblauem Hintergrund

    Why Vitamin D3 and Vitamin K2 are considered together

    In recent years, the synergistic interaction between vitamin D and vitamin K2 in calcium metabolism has increasingly come into focus. The basic concept: a high-dose vitamin D intake increases calcium absorption from the intestine – however, whether this additional calcium is incorporated into the bones or deposited in soft tissues and vessel walls depends significantly on sufficiently activated osteocalcin and thus on vitamin K2 supply. This connection is discussed in professional literature and is the subject of ongoing research; it is currently not a health claim approved by the EFSA, but rather a plausible, mechanistically grounded explanatory approach as to why both vitamins are frequently taken together.

  • Eine Kapsel in der Hand Bioverfügbarkeit von Vitamin D3 und Vitamin K2

    Bioavailability: what matters with MK-7

    With vitamin K2 in the form of MK-7, it is primarily the isomeric form that determines biological efficacy – regardless of whether the MK-7 was produced via fermentation (e.g., from natto) or synthetically. A randomized controlled trial compared synthetic MK-7 with fermentation-derived MK-7 regarding both blood absorption and functional effect on osteocalcin, and established bioequivalence to fermentation-derived MK-7 for the predominantly all-trans-configured synthetic form examined. Therefore, what is decisive for the quality of a preparation is less its origin than the proportion of the biologically active all-trans form.

  • Study results

    - EFSA NDA Panel. Scientific Opinion on health claims related to vitamin D and bone/teeth, calcium and phosphorus absorption, blood calcium, cell division. EFSA Journal, 2009 → Link: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2009.1227
    - EFSA NDA Panel. Scientific Opinion on health claims related to vitamin D and immune system, muscle function. EFSA Journal, 2010 → Link: https://efsa.onlinelibrary.wiley.com/doi/pdf/10.2903/j.efsa.2010.1468
    - EFSA NDA Panel. Scientific Opinion on vitamin D and risk of falling. EFSA Journal, 2011→ Link: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2011.2382

    - EFSA NDA Panel. Scientific Opinion on health claims related to vitamin K and bone, blood coagulation. EFSA Journal, 2009 → Link: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2009.1228

    - Møller, M. et al. Bioavailability and chemical/functional aspects of synthetic MK-7 vs fermentation-derived MK-7 in randomised controlled trials. International Journal for Vitamin and Nutrition Research, 2016 → Link: https://pubmed.ncbi.nlm.nih.gov/27374276/



    This article is for general information purposes only and does not replace individual medical advice.