A healthy balanced diet is known to be vital for overall good health and wellbeing. The components of a balanced diet include vitamins, minerals, plant chemicals as well as macronutrients like protein and fibre. Although they are only needed in small quantities, vitamins play a powerful role in your health.
We always take an evidence-based approach and aim to provide you with actionable knowledge and tips to help you on your journey to optimal health.
In this article we focus on why vitamin K is essential.
Types of vitamin K
Vitamin K is classed as a fat soluble vitamin which can be split into a few different forms.
These are vitamin K1 – phylloquinone, and several types of K2 – menaquinone. Menaquinones are named according to the length of their structure and the most commonly studied forms of menaquinone include MK-4, MK-7 and MK-9.
Vitamin K3 refers to a synthetic form of vitamin K, called menadione.
Sources of vitamin K
Plant foods that are rich in vitamin K1 include kale, broccoli, Brussels sprouts, asparagus, kiwi fruit, okra and green beans. The actual content of vitamin K may vary and is more concentrated in the outer darker leaves.
Some plant oils like soybean and olive also contain vitamin K. This has shown to be more absorbable than vitamin K from vegetable leaves. Absorption of vitamin K from vegetable sources is enhanced by the addition of fat.
Vitamin K2 comes from bacterial fermentation and is present in fermented foods like natto, cheese and curds. Some animal livers also contribute to vitamin K intake.
Beneficial bacteria in the colon also synthesise vitamin K (1).
Recommended intake
The EFSA (European Safety Authority) set a daily recommended intake of vitamin K for adults at 70µg per day.
Children and adolescent intakes can be found in the table below.
|
Age (years) |
Daily vitamin K recommendation |
|
1-3 |
12µg |
|
4-6 |
20µg |
|
7-10 |
30µg |
|
11-14 |
45µg |
|
15-17 |
65µg |
Vitamin K functions
Vitamin K is known to be a co-enzyme for the synthesis and functioning of several proteins involved in many physiological processes. This means that vitamin K may affect several functions within the body.
- Blood clotting
Clotting factors that are dependent on vitamin K are synthesised in the liver including clotting factor II – prothrombin (2). Severe liver disease can lead to lower levels of clotting factors and an increased risk of bleeding (3).
- Bone metabolism
Several bone related proteins rely on the influence of vitamin K. Impaired activity of these proteins may contribute to bone mineralisation defects (4).
A higher intake of vitamin K is associated with better bone mineral density and a reduced risk of hip fracture (5) whereas a low vitamin K level is linked to reduced bone mineral density (6).
Osteoporosis is characterised by porous and fragile bones and nutrients such as calcium and vitamin D are vital to ensure healthy bones. The importance of a good vitamin K level for prevention of osteoporosis has also been studied and a particular form of vitamin K, MK-4, is known to benefit bone mineral density and reduce the risk of fractures (7).
Pharmacological doses of MK-4 are routinely given in Japan for the treatment of osteoporosis. The Japanese diet is rich in natto, a fermented soybean dish, a good source of the MK-7 form of vitamin K.
A dose of 180 µg per day of MK-7 was shown to improve bone strength in post-menopausal women (8).
- Blood vessel health and heart disease
Heart disease is associated with the build-up of calcium on the walls of arteries. This calcium build-up is implicated in the development of atherosclerosis which is known to cause a hardening and narrowing of arteries, leading to issues like stroke and heart attack.
A vitamin K dependent protein may play a role in the prevention of calcium build-up in blood vessels (9) and a good intake of vitamin K2 may reduce the risk of heart disease (10).
Deficiency
Vitamin K levels are not routinely tested, with the exception of those on anti-coagulant therapy. It is rapidly metabolised in the body and, unlike other fat soluble vitamins, is not readily stored, so low levels are seen in the blood and tissues (11).
A lack of vitamin K is known to increase the risk of bleeding. Symptoms that may be seen include increased bruising, nosebleeds, heavy menstrual bleeding and blood in the urine or stool.
Although vitamin K deficiency is not common, certain people may be more at risk than others, due to dietary content and gut bacterial synthesis. Those with fat malabsorption issues, as in inflammatory bowel disease and those with liver damage are more at risk of vitamin K deficiency.
Exclusively breast fed newborn infants are also more at risk of vitamin K deficiency for several reasons, including the fact that breast milk has a low vitamin K content.
Toxicity
Abnormal clotting is not related to excessive vitamin K intake and there is no known toxicity associated with vitamin K1 or vitamin K2 (12).
The synthetic form of vitamin K, menadione, has however been shown to cause issues. It is known to interfere with the production of the body’s major antioxidant called glutathione, leading to cellular damage.
Once used to treat vitamin K deficiency, menadione has induced liver damage, jaundice and anaemia and is now no longer used.
Drug and nutrient interactions
Anti-coagulant drugs like warfarin interfere with vitamin K recycling and therefore affect clotting.
This is a desired effect for people at risk of stroke or heart attack.
However, large quantities of vitamin K can override the mechanism behind some anti-coagulants like warfarin and vitamin K intake should be observed in those taking these types of medication.
It should also be noted that high doses of vitamin A and E may interfere with vitamin K absorption or activity.
Additionally, medications such as some anti-convulsant drugs, anti-tuberculosis drugs, cholesterol lowering drugs and the long term use of antibiotics may also interfere with vitamin K.
Takeaway
A good level of vitamin K is essential, and evidence is showing that both vitamin K1 from plant sources and vitamin K2 from fermented foods and bacterial synthesis are required for good health.
Ensuring gut functioning is optimal further supports vitamin K levels.
Advice from an experienced Personalised Health Practitioner can be beneficial to achieve optimal gut functioning and microbiome balance.
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