nutrient
Vitamin K2 (menaquinones)
A group name for menaquinone forms of vitamin K found in some animal and fermented foods.
Menaquinones include several molecules with different chain lengths and sources. K2 is not one single chemical substance.
What the form means
Menaquinones are part of the vitamin K family, but the available evidence and reference values are form-specific. Keep a product’s named menaquinone visible rather than treating “K2” as a complete description.
Forms
Vitamin K2 (menaquinones) is a form of Vitamin K.
Vitamin K2 (menaquinones) is a named chemical form within its parent vitamin family.
Worth knowing
K2 is a family label. Vitamin K2 refers to several menaquinones rather than one substance. MK-4, MK-7 and other members have different food sources and side-chain lengths, so a product label needs the named form when that detail matters.
A closer look
Menaquinones have different origins
MK-4 can be produced from phylloquinone by human tissues without bacterial action. Longer-chain menaquinones are largely bacterial in origin, including production in the gut, although the amount that contributes to vitamin K status remains uncertain.
References
Source-checked local draft.
Human editorial review pending.