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VITAMIN K  (K1 phylloquinone, K2 menaquinone, K3 menadione)

Vitamin K describes a group of lipophilic vitamins that exist naturally in two forms: vitamin K1 (phylloquinone, found in green plants) and vitamin K2 (a group of menaquinones synthesised by bacteria in the intestine). Vitamin K3 (menadione) is a synthetic form of vitamin K that is used in agricultural animal feeds.

Vitamin K is fat-soluble and known as the clotting vitamin, because without it blood would not clot. It serves as a coenzyme in the formation of various blood clotting factors. It is used in the body for synthesising the liver protein that controls blood clotting. It is involved in creating the important prothrombin, which is the precursor to thrombin, a very important factor in blood clotting. It is also involved in bone formation and repair. In the intestines it also assists in converting glucose to glycogen, which is then stored in the liver to be used as energy when required.

Vitamin K can also reduce the risk of bleeding in liver disease, jaundice, malabsorption or in association with long-term use of aspirin or antibiotics. Vitamin K-rich foods can help people with digestive disorders such as Crohn's disease to absorb nutrients better.

Vitamin K1 helps prevent excessive activation of osteoclasts, the cells that break down bone. Beneficial bacteria in the intestines convert vitamin K1 into vitamin K2, which activates osteocalcin, the major non-collagen protein in bone. Osteocalcin anchors calcium molecules inside of the bone. All of these vitamin K-related mechanisms point to the importance of vitamin K-rich foods for bone and heart health.

The benefit of vitamin D, where bone strength and cardiovascular health are concerned, is greatly enhanced when combined with vitamin K2. Vitamin D improves bone health by helping the body absorb calcium. However, it is vitamin K2 that directs calcium to the skeleton, to prevent it from being deposited in the wrong areas such as around the heart. Vitamin K2 (menaquinones) only occurs in foods of animal origin or foods altered by bacterial fermentation. See below.

Vitamin K2 is linked to cardiovascular health and is essential for regulating proteins in the body that direct calcium to the bones and keep it out of the arterial walls and organs where it can do harm. Low vitamin K in aging humans can lead to vascular calcification, chronic inflammation and a seriously higher risk of heart attack and strokes. Vitamin K blood tests assess levels of vitamin K to maintain healthy coagulation, but at this time are not used to identify optimal levels of K2 to reduce heart attack risk.

Deficiency of vitamin K

Vitamin K deficiency occurs when the body cannot properly absorb the vitamin from the intestinal tract like after long-term treatment with antibiotics or food allergies. People with vitamin K deficiency are usually more likely to have bruising and bleeding. Deficiency in newborn babies results in hemorrhagic disease, as well as postoperative bleeding and haematuria while muscle haematomas and inter-cranial haemorrhages have been reported. A shortage of this vitamin may cause nosebleeds and internal haemorrhaging. Supplemental vitamin K is often given to newborns who generally have lower levels.

Highest sources of vitamin K1 in micrograms per 100 grams

  • Basil 1714.5 µg

  • Kale 817 µg

  • Watercress 252 µg

  • Spring onions 207 µg

  • Broccoli 148 µg

  • Cloves 142 µg

  • Brussel sprouts 140.3 µg

  • Chilli peppers 105.7 µg)

  • Pickled cucumber 76.7 µg

  • Soya beans 70.6 µg

  • Spirulina and chlorella algae 70 µg

  • Olive oil 60.2 µg

  • Prunes 59.5 µg

  • Asparagus 50.6 µg

  • Sun dried tomatoes 43 μg

  • Cashew nuts 35 µg

  • Alfalfa sprouts 30.5 μg

  • Celery 29 µg

  • Black berries 20 µg

  • Blue berries 19 µg

NOTE: One µg is one microgram. The recommended daily allowance of vitaminK1 is 90 µg for adult women and 120 µg for men. It is important to limit foods that are rich in vitamin K if pregnant, breast feeding or taking blood thinning medication (such as anticoagulant or anti-platelet drugs)

Highest sources of vitamin K2

  • Brine pickles

  • Butter

  • Cheese (brie and gouda)

  • Chicken breast and livers

  • Egg yolk

  • Milk (full cream)

  • Natto (fermented soya)

  • Organ meats such as liver

  • Yoghurt (full fat)

See how to make your own brine pickles using salt and water


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Prebiotic  foods


Consuming prebiotic foods that feed the existing beneficial bacteria also helps to produce vitamin K2.

Prebiotic foods that feed the existing beneficial bacteria

  • Agave

  • Apples

  • Asparagus

  • Banana

  • Beans

  • Bran

  • Broccoli

  • Burdock root

  • Cabbage

  • Cauliflower

  • Celeriac

  • Chicory root

  • Cocoa (raw)

  • Coconut flesh

  • Dandelion root

  • Elecampane

  • Elephant foot yam

  • Garlic

  • Jerusalem artichoke

  • Jicama root

  • Kale

  • Leeks

  • Lentils

  • Mashua

  • Mugwort

  • Oats

  • Onions

  • Parsnips

  • Peas

  • Radish

  • Rampion

  • Salsify

  • Turnip

  • Swede

  • Sweet potato

  • Whole grains

  • Yacon root

  • Yams


Probiotic foods


Because vitamin K2 is produced by the intestinal bacteria, the addition of fermented foods such as natto which is a fermented soya product is useful as it helps to provide extra beneficial bacteria to the gut. Other sources are gouda and brie cheeses and other products from grass-fed cows.


Probiotic foods contain beneficial bacteria and come from the fermentation process that the food has been allowed to undergo. During and after any treatment with antibiotics, it is advisable to include more probiotic foods in the daily diet to replenish the friendly bacteria that are wiped out by antibiotics. It is advisable to consume probiotics at least an hour before other foods to enable enough beneficial bacteria to survive and pass through the strong stomach acids.

Probiotic foods that contain beneficial bacteria

  • Brine pickles (eggs, fruit, nuts, seeds and vegetables that have been fermented by lactic acid bacteria)

  • Kefir (fermented milk drink)

  • Kimchi (a fermented, spicy Korean side dish)

  • Kombucha (fermented black or green Asian tea)

  • Miso (a Japanese fermented seasoning made with soya beans, salt and a type of fungus called koji)

  • Sauerkraut (finely shredded cabbage that has been fermented by lactic acid bacteria)

  • Tempeh (fermented soya beans)

  • Yoghurt (plain with live cultures)

For more about probiotic 'good' and pathogenic 'bad' bacteria and the diseases they can cause see Bacteria.

Associated articles

References: (copy and paste into browser)

  • efsa.europa.eu/en/efsajournal/pub/3532 

"Nature cures not the physician..." Hippocrates 460 BC


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