Two things that often freak people out are blood clots and bacteria. Unless a medical professional or a microbiologist, the usual consensus is “Can we talk about something else?” as if these two words pierce like needles to our ears. First in defense of clotting, it has to happen or we would bleed out like a hemophiliac. Okay so no one likes a blood clot (especially when it breaks off as an embolus into the bloodstream and clots an arterial vessel by the heart or in the brain) but everyone likes when their finger stops gushing blood after a paper cut.
Secondly in defense of bacteria, although it may seem terrifying we are covered in billions of bacterial cells from thousands of different species (At least now we don’t have to feel all depressed about being “alone” any given holiday). Matter of fact, one of the more common species that enjoys using our skin as its playground is the notorious Staphylococcus Aureus which is often responsible for the infection we experience with pimples or acne (“You’ve got Staph! Oh no!”). Also, billions of bacterial cells absolutely thrive in our large intestine (called gut flora or microflora…most are “good” but some are pathogenically bad) which can actually assist in the breakdown of undigested carbohydrates (fiber), the synthesis of our friend vitamin B7 or biotin, and the conversion of (drum roll) vitamin K to a more useable form.
Vitamin K is our last fat soluble vitamin which exists as either K1 (phylloquinone, phytomenadione, phytoadione) in plants or K2 (menaquinones) in animals. Most of the vitamin K that we get in our diets is K1, and the body will then actually convert it into the useable K2 form. Any K1 that manages to get past this process (which actually takes place in the pancreas and arterial walls) is converted into K2 by intestinal microflora. It is still unclear just how much of the K2 produced by bacteria is then absorbed by the body but it is thought to be a minor contribution. The main function of vitamin K is its involvement in what is called the clotting cascade. It helps synthesize certain proteins that are needed to helps clots form in an open wound to stop bleeding or the loss of red blood cells which are essential for survival. A good sign of clotting is when the fluid exiting the body becomes more clear which means that it is higher in plasma and lower in red blood cells (thus why a person can donate plasma twice a week [red blood cells are returned] versus donating whole blood once every 56 days…helped me get through college). Here is a very descriptive illustration of the clotting cascade:
One of the more important proteins in blood clotting that vitamin K helps synthesize is prothrombin which is needed at the start of the clotting cascade. The length of time it takes for a blood clot to form is often referred to as prothrombin time. Matter of fact, anticoagulants such as the medication warfarin are measured against prothrombin time for effectiveness. That being said, someone that is on such a medication is advised to avoid a diet that is rich in vitamin K so that the effect of an anticoagulant can be maximized. As we can recall from the vitamin E post, too much supplemental vitamin E can work antagonistically to vitamin K as a blood thinner and it can increase the risk of uncontrollable bleeding in an individual on an anticoagulant. A fun fact: mosquitoes and leeches secrete an anticoagulant when they bite us in order to prevent clotting so that they can “get their drink on” (those pesky jerks).
Aside from coagulation, vitamin K also helps us with bone mineralization and cell growth. As of 2001, the Adequate Intake (AI) for vitamin K is 120 micrograms (mcg) and 90 mcg for men and women aged 19 years or older, respectively. No Upper Tolerable Intake Level (UL) has been established for vitamin K. Deficiency is rare but symptoms could include anemia, bruising, bleeding of the gums and nose, and an increased risk for osteoporosis and coronary heart disease. Only vitamin K3 (menadione) is considered toxic but has since been banned by the Food and Drug Administration (FDA) from supplements for causing allergic reactions, anemia, and liver toxicity. Our best sources of vitamin K are cooked natto (1,103.4 mcg in 3.5 ounces [oz]; as K2), kale (531 mcg in ½ cup; as K1), spinach (444 mcg in ½ cup; as K1), collard greens (418 mcg in ½ cup; as K1), goose liver pate (369 mcg in 3.5 oz; as K2), Swiss chard (287 mcg in ½ cup; as K1), and turnip greens (265 mcg in ½ cup; as K1).