Vitamin D and K: how to compare combination products

Why are vitamins D and K often found together?

Vitamin D helps the body to absorb and use calcium and phosphorus properly, and helps maintain healthy bones. Vitamin K contributes to normal blood clotting and helps maintain healthy bones. These are separate, established functions of each vitamin.

Including both vitamins in one product makes it possible to compare their amounts in the same formula. However, this does not in itself prove that combining them will produce a special additional effect for everyone. Calcium, other dietary ingredients and the overall diet also matter.

Before comparing labels, decide what you are looking for: vitamin D alone, a combination of D and K, or a broader formula with minerals. These are different questions and may lead to different conclusions about the composition.

K1 and K2: what do these names mean?

Vitamin K comes in different forms. On a label, you may see K1 or K2, also called menaquinone. A designation such as MK-7 identifies a specific form of vitamin K2. However, the name K2 alone does not tell you the amount in a serving or whether a particular formula is suitable for everyone.

A serving is a specified amount of a product, for example one tablet or several capsules, to which the values in the table refer. The amount stated per serving must therefore be read together with information about how many tablets or capsules that serving includes. Diet and medicines taken also matter.

If a product page states only “vitamin K”, you should not assume on your own that it means K1, K2 or a specific form such as MK-7. Check the current label for the variant you have chosen. This is especially useful when comparing information from different markets.

Three CaliVita® formulas: composition and amounts on the label

Calcium and magnesium are minerals, which are nutrients other than vitamins. In CaliVita® products, the stated amounts refer to different numbers of units: in Ca-Mg with D+K they refer to one tablet, while in Calcium Magnesium Plus they refer to two capsules. The table below shows why it is worth distinguishing amounts per serving from amounts in one unit.

In the table, “mg” means milligram and “µg” means microgram. A milligram is one thousandth of a gram, and a microgram is one thousandth of a milligram. In the first row, all amounts refer to one tablet. In the second row, they refer to two capsules together, not to one capsule.

Both products declare 5 µg of vitamin D and 90 µg of vitamin K in the stated servings. The mineral amounts differ, and the serving formats are different. For reference, you can calculate the amounts in two Calcium Magnesium Plus capsules per capsule: 500 mg of calcium ÷ 2 = 250 mg, and 250 mg of magnesium ÷ 2 = 125 mg. Similarly, 5 µg of D ÷ 2 = 2,5 µg, and 90 µg of K ÷ 2 = 45 µg per capsule. This calculation describes the contents of one unit, not a recommendation about how much to take.

The third formula, Pure Ca + Mg Plus, includes four plant-based capsules in the described serving. In addition to calcium, magnesium and vitamins D and K, it contains zinc, boron, acerola and horsetail extract, among other ingredients. Acerola is the name of a plant; its presence, like that of horsetail extract, means this is a broader combination to compare, not simply a combination of vitamins D and K with minerals.

What do studies show, and what should not be inferred from them?

Studies on vitamin K and bone health involve different groups of people, forms of the vitamin and amounts. A bone metabolism marker is a measure taken in a study that may provide information about processes related to bones. A change in such a marker does not automatically mean that a reduced risk of fractures has been demonstrated.

The established functions of vitamins can be described within the limits of permitted health claims. However, they are not a guarantee of treatment or protection against a specific disease. A study result on an individual ingredient also does not determine the effects of an entire product that contains more ingredients.

There is no basis for assuming that everyone taking vitamin D must also add any product containing vitamin K. When comparing formulas, it is more important to take account of diet, medicines and nutrient amounts than to follow a single approach based on a general slogan. CaliVita® products make it possible to compare a combination formula with different amounts of minerals and a broader formulation.

Important note about medicines

Vitamin K is important when taking vitamin K antagonists, which are medicines that affect the action of this vitamin. Warfarin is one example. Changes in vitamin K intake or supplementation must be discussed with the doctor responsible for your care. Do not change your medicines or start using a product containing vitamin K on your own while receiving this treatment, based on this article alone.

Before speaking to a doctor or pharmacist, it is worth preparing the names of the products you are considering, the amounts of D and K in the stated servings, the other ingredients, any other products you take and a list of your medicines. This will make it possible to discuss both the features of the formula and any issues requiring caution.