There are two main forms of natural vitamin K: phylloquinone (K1) and menaquinone (K2). Vitamin K1 is primarily found in green leafy vegetables and plays a role in blood coagulation, while vitamin K2 is mainly produced by gut microbiota and is essential for healthy arteries and bones. They are both absorbed in the small intestine.
Phylloquinone is essential to the circulatory system: without it, the liver is unable to produce the molecules that ensure coagulation of the blood (1). Serious K1 deficiency poses a risk of haemorrhage while in contrast, certain anticoagulant treatments are vitamin K antagonists – they work by reducing its blood-clotting action.
Vitamin K1 is found in green vegetables (spinach, cabbage, lettuce, broccoli …), and soya and rapeseed oils.
Like vitamin K1, vitamin K2 is a protein activator, and participates in blood coagulation (2). But it is more often recognised for its essential role in maintaining arterial flexibility (3). Menaquinone activates matrix Gla-protein (MGP), which contributes to the elimination of calcium in the arteries, thus helping to prevent calcification and associated risks such as hypertension.
Its role in calcium metabolism also means it is able to protect bone density (4), particularly in at-risk groups (menopausal women, infants): without vitamin K2, calcium would not be taken up by the protein osteocalcin for subsequent binding to, and strengthening of, the bone matrix.
Due to its chemical structure, it remains in the blood longer - a few days rather than a few hours in the case for vitamin K1 - and therefore has longer-lasting effects (5).
Vitamin K2 is produced in the body from bacteria present in the gut. It’s also found in highly-fermented foods such as sauerkraut, natto (a Japanese food based on fermented soya beans), cheese, liver, yogurt, and of course, dietary supplements. The Supersmart catalogue offers the only form of vitamin K2 able to produce an 8-fold increase in vitamin K blood levels: MK-7 90 mcg. It comes in the form of softgels for maximum absorption, and is combined with vitamin D for scientifically-supported synergistic effects!
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