Vitamins are essential nutrients for our bodies, which our bodies do not produce, and we need to obtain them either from our diet or from the sun (Vitamin D). When we consider all the benefits of the different types of vitamins, how many of us know the function of Vitamin K? In 1929, a Danish scientist was investigating the effects of a low-cholesterol diet in chickens. When he lowered their cholesterol intake, the chickens developed hemorrhages and bleeding. Adding purified cholesterol back to their diet did not resolve the problem, therefore he determined that another substance had to have been inadvertently removed from the chicken’s diet at the same time. When the scientist was able to isolate this substance, he called it the “coagulation vitamin”. He published his findings in a German journal, and they, in turn, assigned the vitamin the letter “K”. “K” comes from the German word, “Koagulations,” or in English, “coagulation”. For many years, the only way to determine the amount of Vitamin K in a food was to make chickens Vitamin K deficient, and then feed them a food which was known to contain Vitamin K. The amount of blood coagulation restored by the diet was taken as the measure of the Vitamin K in the food.
Eventually, the scientists who did most of the research to determine the structure and chemical nature of Vitamin K received the Nobel Prize for their work in 1943. They discovered that Vitamin K helped blood to clot by activating certain proteins in the liver. This coagulation system is very tightly controlled in our body. Blood must flow smoothly as a liquid through miles of blood vessels each day, yet also be capable of starting a solid clot within seconds of encountering a break in the blood vessel system, such as a wound or other injury. If the blood fails to clot, a fatal hemorrhage can result; if the blood clots just a little too readily, blood vessel blockage can occur, leading to tissue and organ damage by preventing blood from circulating, also leading to oxygen deprivation of the body’s tissues. This delicate balance is maintained with the help of vitamin K.
With low body levels of Vitamin K, bleeding can occur. Without enough vitamin K, small cuts can go on bleeding for a very long time and big bruises can happen from small injuries. Bleeding can also occur in other parts of the body, such as the gums, nose, and brain (causing a stroke). Women can have heavy menstrual bleeding. Recently, scientists have discovered that Vitamin K has many more health benefits than just clotting our blood. A true Vitamin K deficiency is very rare, but you may not be getting enough in your diet to enjoy its other health benefits.
Vitamin K is unique in several ways, compared to the other vitamins. It is the only vitamin that is produced within the human body, but not by the human body. To be called a Vitamin, the substance cannot be produced by human tissue. Beneficial bacteria (probiotics) in the intestine produces about 75% of the Vitamin K that the body absorbs each day, with the other 25% coming from food. The combination from both sources equals the minimum amount required for the body.
There are two forms of Vitamin K. Vitamin K1 is an important chemical in plants, and is found in highest amounts in green leafy vegetables because K1 is directly involved in photosynthesis (the process by which plants make food). It may be thought of as the “plant” form of vitamin K. K2 is the form that is produced by the bacteria in our intestine. We can also convert K1 to K2 in our body. Bacteria in the large intestine can also convert K1 into vitamin K2. K2 is more important in functions such as the mineralization of bone. Unlike the other fat-soluble vitamins (A, D, E), vitamin K is not stored in the fat tissue of the human body. A person can become Vitamin K deficient after 7–10 days of a diet low in Vitamin K. For this reason, the daily balance of Vitamin K is important. Scientists are now discovering that Vitamin K is needed for many more functions in the body than just blood clotting, therefore the amount we need is higher than once thought.
Newborn infants represent the highest risk of developing bleeding from a Vitamin K deficiency. Some of you may recall your newborn receiving a needle containing Vitamin K directly after birth. Babies are born with very limited amounts of Vitamin K because their intestines do not contain any bacteria at birth with which to produce Vitamin K. Their Vitamin K levels are lowest at days 2–3 and do not reach adult levels until about 6 months of age. The injection of vitamin K at birth reduces the risk of bleeding in newborns. Bleeding due to vitamin K deficiency can be severe, leading to hospitalization, blood transfusions, brain damage, and death. Supplementation can prevent most cases of vitamin K deficiency bleeding in the newborn.
Studies show that even if a mother consumes foods high in Vitamin K during the pregnancy, the levels of Vitamin K in their infants do not increase. Babies have very little vitamin K in their bodies at birth. After birth, there is little vitamin K in breast milk and breastfed babies can be low in vitamin K for several weeks until the normal intestinal bacteria start making it. Infant formula has added vitamin K, but even formula-fed babies have very low levels of vitamin K for several days.
Current research has shown that people who have the highest blood levels of Vitamin K are at a much lower risk of death from cardiovascular disease (heart disease), cancers, and other diseases. Over a five year period, a group of people were studied. Participants with the highest intake of Vitamin K were 46% less likely to die of cancer and 36% less likely to die from any cause versus those with the lowest intake of Vitamin K.
Also, inflammation in the body is known to increase our risk of heart disease by increasing plaque in our blood vessel walls. This leads to increased risk of heart attacks and strokes. As Vitamin K levels increase in a person’s blood, their levels of inflammation decrease.
Chronic inflammation in the body also contributes to Arthritis, Alzheimer’s disease, cognitive decline and type-2 Diabetes. Vitamin K can also help to prevent Diabetes by improving blood sugar control. Vitamin K has been shown to prevent nerve cell damage, which also may stop the progression of Alzheimer’s.
Calcium deposits in arteries lead to atherosclerosis (build-up of plaque). Calcification of arteries is now shown to be the identical process which builds up calcium in bone and increases bone strength. However, Vitamin K in blood vessel walls decreases the amount of calcification in the blood vessels. In terms of heart health, low Vitamin K intake in younger adults does not appear to cause early calcification of vessels. However, Vitamin K’s effects on blood vessels becomes more important with advancing age. Older adults who already have calcium deposits in their arteries have less progression of calcium build-up if they eat foods high in Vitamin K.
Interestingly, Vitamin K has the opposite effect on bone. Adequate amounts of vitamin D and calcium are required to prevent osteoporosis. However, vitamin D or calcium cannot produce healthy bones without adequate supplies of vitamin K. Vitamin K is also recognized as important in binding calcium to bone. Low Vitamin K levels (less than 100 mcg daily) have been shown to increase the risk of fractures.
People who need the drug, Coumadin to thin their blood to prevent incidents such as strokes should avoid large fluctuations in the amount of Vitamin K-rich foods, as they can either increase or decrease the level of the medication in the bloodstream. Coumadin thins the blood, and Vitamin K clots the blood. Doctors will prescribe a dose of Coumadin that takes into account the amount of Vitamin K foods that you eat. As long as your Vitamin K intake remains stable, Coumadin doses will not need to be adjusted.
The Recommended Daily Allowance for Vitamin K is 120 mcg a day for men and 90 mcg a day for women.
Foods high in Vitamin K
Vitamin K1, found in leafy greens and cruciferous vegetables make up about 90% of our dietary intake.
Foods with lower levels of Vitamin K include paler green-leafed foods and other green-coloured vegetables such as peas. Vitamin K is also contained in some green-coloured fruits such as kiwis and green apples (peels).
Kale is our top source of vitamin K—a 1-cup serving will provide you with over 1,000 micrograms, which is approximately 10 times the recommended minimum daily amount! There are no maximum allowable amounts recommended, which means that eating amounts above the daily requirement is not harmful.
Dihydrophylloquinone is an unhealthy form of Vitamin K1 found in trans-fats. Any foods that contain partially hydrogenated fats such as margarines and vegetable shortenings (especially solid vs soft varieties), pancake mixes, French fries, fried/battered foods, microwave popcorn (containing toppings), tortilla chips, and cookies should be avoided.
Top Vitamin K foods:
1) Green leafy vegetables: Kale (highest), spinach, mustard greens, collards, beet greens, Swiss chard, turnip greens, dandelion greens.
2) Herbs: Dried Basil (highest), dried sage, dried thyme, fresh parsley, cilantro.
3) Salad Vegetables: Spring Onions/Scallions (highest), endive, radicchio, watercress, romaine lettuce, green and red lettuce, celery.
4) Cruciferous Vegetables: Brussels sprouts (highest), broccoli, cabbage, Chinese broccoli, red cabbage, pak choi, Savoy cabbage.
5) Other vegetables: Asparagus, fennel, leeks, okra.
6) Soybeans
7) Vegetable oils: Olive Oil (highest), soybean, canola.
8) Dried Fruit: Prunes (highest), blueberries, pears, peaches, figs, currants.
Many of these foods provide well over the recommended daily dose of Vitamin K. When thinking of blood vessel, bone and brain health, think “K”.