What is Vitamin K?
The last decade has seen an increasing interest in the benefits of vitamin K. This is mainly due to recent advances in scientific techniques enabling researchers to discover new roles for the vitamin.
These influence a far broader range of physiological processes than was originally thought.
Vitamin K is not a single chemical substance but rather a family of chemically related substances that go by the general name of ‘Vitamin K’. Over the past 20 years, no vitamin family has undergone a greater change in terms of our scientific understanding of its chemistry and function.
In the past, members of the vitamin K family have traditionally been referred to as vitamin K1, vitamin K2 and vitamin K3. This terminology is largely being replaced by a different set of terms to describe what has now been determined to be a more complicated set of vitamin K compounds.
Briefly, the vitamin known as K1 is also known as phylloquinone and is obtained in the diet from green leaves, broccoli, Brussels sprouts and plant oils such as rapeseed and olive oils.
Vitamin K2 is a family of manaquinones produced by bacteria, including those found in the colon.
Small amounts of K2 are present in the diet in meat and liver, which are bacteriologically produced by animals, and in fermented foods such as cheese. The most significant K2 source is in a fermented soy food called natto, which contains one of the family of vitamin K2 (of which there are many).
Interestingly natto is eaten widely in Japan but is far from the basis of a staple diet in Europe or the US. There are further breakdowns of the vitamin; however, we will just look at the basic definitions today.
Vitamin K was identified in 1929 by Danish scientist Henrik Dam when he investigated the role of cholesterol by feeding chickens a cholesterol-depleted diet. After several weeks, the animals developed hemorrhages and started bleeding.
These defects could not be restored by adding purified cholesterol to the diet. It appeared that –together with the cholesterol – a second compound had been extracted from the food and this compound was called the coagulation vitamin.
The new vitamin received the letter ‘K’ because the initial discoveries were reported in a German journal, in which it was designated as Koagulationsvitamin.
Studies indicate that the typical modern western diet may not be sufficient for long-term bone health. The daily intake of K1 and K2 is far higher in Japan, for example, than in countries such as the UK. Serum K2 levels are particularly high in Eastern Japan where natto is widely consumed and this correlates with a lower rate of hip fracture among elderly women.
High vitamin K foods can help in allowing the blood to clot normally, protect the bones from fracture, help prevent postmenopausal bone loss and calcification of the arteries. It also provides possible protection against liver and prostate cancer according to studies.
Vitamin K deficiency can arise in individuals with malnutrition and malabsorption problems due to medical issues such as coeliac disease, inflammatory bowel disease and alcoholism.
As vitamin K is produced by colonic bacteria it could theoretically occur in cases of imbalance in the gut which could arise from, for example, overuse of antibiotics. In addition, blood thinning medications are vitamin K antagonists.
Signs which could lead to vitamin K deficiency are excessive bleeding, including heavy menstrual bleeding, gum or nose bleeding and bleeding within the digestive tract. Pronounced easy bruising, problems with bone fractures or weakening of the bones.
Also any problems with calcification of the blood vessels or heart valves. Of course, all of these or any of these individually, could be signs of other health issues and should always be referred to a medical practitioner.
It is interesting to explore the contribution to bone health in post menopausal women; particularly as such emphasis is placed on calcium in this regard. The relationship of vitamin K to bone health has been fairly well researched, and in the big picture, vitamin K has emerged as a critical nutrient for bone health.
Most convincing is research showing protection from bone fractures that occur when vitamin K is consumed in adequate amounts.
Individuals who are vitamin K deficient have been clearly shown to have a greater risk of fracture. In addition, for women who have passed through menopause and have started to experience unwanted bone loss, vitamin K has been clearly shown to help prevent future fractures.
To assess whether or not our diet includes enough vitamin K it is worth knowing that the most beneficial sources of vitamin K in foods include parsley, kale, spinach, Brussels sprouts, Swiss chard, green beans, asparagus, broccoli, kale, mustard greens, turnip greens, collard greens, thyme, romaine lettuce, sage, oregano, cabbage, celery, sea vegetables, cucumber, leeks, cauliflower, tomatoes and blueberries.
In some cases, the benefit of a vitamin in food is negated by the way it is cooked. As a general rule, vitamin K is a resilient nutrient and is fairly well retained in most cooked or stored foods. It is difficult to draw any hard and fast conclusions because there can be at least a 20-30 per cent variation in vitamin K between different varieties of the same food, especially when grown under different circumstances (for example, in different countries).
When observing the foods which provide vitamin K, it is interesting to note that many of these foods make up the Mediterranean diet. As such, if the diet is followed carefully and the lifestyle is also beneficial, vitamin K should be well provided for.