When I discuss bone health in clinical practice, calcium is what comes to mind first for most people, followed by the crucial question: should I supplement it?
Apart from the complex interplay between calcium and cancer (my field of specialisation) warranting caution with calcium supplementation, the reality is that, in our society, calcium intake is generally good enough in most people’s diets.
On the other hand, what can be missing in sufficient amounts are important cofactors for the regulation of calcium absorption and utilisation. In particular vitamin D3, which supports the absorption of dietary calcium from the gut into the bloodstream, and vitamin K2, which ensures that calcium is efficiently incorporated into the bone mineral matrix, thus strengthening the skeleton.
Strong Bones and a Healthy Heart
Numerous studies have reported that people with hip fractures have a lower level of vitamin K2 than the general population. Interestingly, in Japan the rate of fractures is particularly low, even among the increasingly elderly population, and researchers have speculated this may be linked to the regular consumption of fermented soy dishes, such as natto, rich in vitamin K2. Moreover, a three-year clinical study of vitamin K2’s impact on bone health in postmenopausal women (n=244) showed a statistically significant protection of the vertebrae and hip against bone loss.
Not only vitamin K2 ensures that calcium is utilised to build bone tissue, but quite remarkably it has the opposite effect on calcium deposits in the walls of arteries, where it prevents arterial calcifications that can lead to heart attacks, strokes and poor blood supply in the legs (known as peripheral vascular disease). Ensuring good levels of vitamin K2 is therefore even more relevant to people who take calcium and vitamin D supplements, to prevent soft tissue calcifications, while promoting calcium integration in the bone. In the presence of vitamin K2 deficiency, long-term supplementation with calcium and vitamin D was associated with cardiovascular disease.
Some of the signs and symptoms of a potential vitamin K2 deficiency include: osteopenia, osteoporosis, arterial calcification, elevated blood pressure, tooth decay, easy bruising, general weakness and fatigue.
How Much and Where From
For adults, the recommended daily intake sufficient to meet the nutrient requirements for vitamin K2 is 100-150mcg for women and 120-180mcg for men. It is important to highlight that modern ultra processed foods have very little vitamin K, whereas whole foods and minimally processed foods is where we can obtain it from.
Common dietary sources of vitamin K2 include:
Leafy dark green vegetables (for example, 100gr of spinach have 480mcg of vitamin K, including K1 and K2)
Fermented foods (natto, sauerkraut, kimchi, kombucha)
Certain cheeses (fermented hard cheese, Stilton, Gouda, Edam, Cheddar)
Eggs
Natural live yoghurts
Meat and butter from grass-fed animals
IMPORTANT NOTES:
Vitamin K2 supplements are available (and potentially needed for people who supplement vitamin D3 and calcium on a regular basis), but as always, it is important to ensure this is appropriate for individual needs and health circumstances.
Vitamin K2 belongs to a family of nutrients (collectively known as vitamin K, this include vitamin K1 and K2) that have an important role in the regulation of blood flow and blood clotting. Foods high in vitamin K are safe for people taking blood thinning medications (e.g. warfarin), but supplements, including K2 supplements, are best avoided. If in doubt, it is best to consult with a nutrition professional.
References
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