Vitamin K: What is it & Where is it Found?

Vitamin K: What is it & Where is it Found?

Vitamin K: What is it & Where is it Found?

What is Vitamin K?

Vitamin K belongs to the fat soluble vitamin family of Vitamin A, D and E. Together with vitamin D, it helps regulate metabolism and can combat the hardening of soft tissues such as blood vessels and help slow bone demineralization. (nutri-facts)

The body stores only relatively small amounts of vitamin K so its reserves are quickly exhausted if there is no regular intake from the diet (Shearer M. J. et al. 2012)


Vitamin K is not a single compound but a group of fat soluble compounds (Hechtman, 2014)

Where can I find Vitamin K?

Vitamin K1 (phylloquinone) is produced directly by plants and is found in green leafy vegetables as well as olive oil and soyabean oil. (DiNicolantonio et al, 2015)

Vitamin K2 (menaquinone) is produced by gut bacteria but Vitamin K1 is mainly found in green leafy vegetables as well as olive oil and soyabean oil, whereas vitamin K2 (menaquinone) is found in small amounts in chicken, butter, egg yolks, cheese and fermented soyabeans (better known as natto) (DiNicolantonio et al, 2015).

Dangers of Vitamin K

The forms and amounts of vitamin K in these foods vary depending on the bacterial strains used to make the foods and their fermentation conditions.

Vitamin K3 (menadione) is a synthetic derivative, water soluble form of the vitamin. According to the US National Institute of Health (NIH) it was shown to damage hepatic cells in laboratory studies conducted during the 1980s and 1990s, so it is no longer used in dietary supplements or fortified foods.

Benefits of Vitamin K

Vitamin K1 plays a very important role in bone health as it converts the bone protein osteocalcin from its inactive form to its active form. Combined Vitamin K is necessary to allow the osteocalcin molecule to join with calcium and hold it in place within the bone.

Signs of Vitamin K deficiency

A deficiency of vitamin K1 leads to impaired mineralization of the bone due to inadequate active osteocalcin levels.

According to a nutri-facts article, the main risk group for bleeding on the brain due to vitamin K deficiency is newborns and breastfed infants, who generally only receive small amounts of vitamin K1 via breast milk, whilst their gut flora is not sufficiently developed to produce vitamin K2.

Newborns and breastfed infants are at particular risk of developing vitamin K deficiency. For this reason they are given vitamin K immediately after birth and in the first days of life.

Vitamin K: What is it & Where is it Found?

Since the vitamin-K dependent coagulation factors are synthesized in the liver, severe liver disease may be associated with very low blood levels of vitamin-K dependent coagulation factors and an increased risk of uncontrollable bleeding (haemorrhage).

Research has shown that vitamin K is an anti-calcification, anti-cancer, bone-forming and insulin-sensitising molecule.  (DiNicolantonio,et al, 2015)

The dangers of Osteoporosis

NIH report that Osteoporosis is a leading contributor of fractures worldwide, causing more than 8.9 million fractures annually. Moreover, Osteoporosis affects an estimated 200 million women worldwide (approximately 1/10th of women aged 60, 1/5th of women aged 70, 2/5ths of women aged 80, and 2/3rds of women aged 90).

One in 3 women and 1 in 5 men over 50 will experience an osteoporotic fracture. Additionally, 61% of all osteoporotic fractures occur in women. It has been predicted that the incidence of hip fracture is expected to increase by 310% in men and 240% in women by 2050; thus, the economic toll of osteoporosis is expected to significantly increase.

In a 3-year randomised, double-blind, controlled trial of 355 patients, vitamin K significantly improved insulin sensitivity in men with diabetes.

Interaction with medications

According to the NIH, Vitamin K can have a serious and potentially dangerous interaction with anticoagulants such as warfarin as well as phenprocoumon, acenocoumarol and tioclomarol so please always consult your GP before taking any supplements if on these medications.

Connect With Expert Sinead Loughnane


Martin J. Shearer, Xueyan Fu, and Sarah L. Booth, 2012,  Vitamin K nutrition, metabolism, and requirements: current concepts and future research. Adv Nutr March 2012 Adv Nutr vol. 3: 182-195, 2012

Advanced Nutrition

DiNicolantonio Jame J, Bhutani Jaikrit,and  O’Keefe James H, 2015, The health benefits of vitamin K Open Heart. 2015; 2(1): e000300.

Published online 2015 Oct 6. doi:  10.1136/openhrt-2015-000300


Hechtman, Leah, 2014, Clinical naturopathic medicine, 1st Edition, Churchill Livingstone

Vitamin K – Fact Sheet for Health Professionals – National Institutes of Health