Nutrient Spotlight: Vitamin K

Most people can name at least one reason they need Vitamin C or calcium. However, Vitamin K rarely gets the same attention, despite being essential to two processes that quite literally keep you alive: blood clotting and bone health. Here's what you need to know. Vitamin K is a fat-soluble micronutrient that serves as a cofactor (think of it as an assistant) to the enzymes responsible for producing the proteins that enable blood clotting (hemostasis) and bone mineralization. Without it, your blood cannot clot properly and your bones cannot retain their density and strength over time.

Vitamin K exists in two main forms. Phylloquinone (Vitamin K1) is the primary dietary source and is found abundantly in green leafy vegetables. Menaquinone (Vitamin K2) is found in animal products and fermented foods, owing to its bacterial origin. Interestingly, the bacteria living in your gut also produce Vitamin K2, contributing to your body's daily requirement.

Vitamin K is fat-soluble, which means dietary fat increases its bioavailability. In simple terms, fat helps your body absorb it through the intestines and put it to work. This is worth knowing because even the most nutrient-rich foods can't benefit you if the nutrients aren't actually absorbed.

Simple Ways to Increase Vitamin K Absorption

• Pair your salad with an oil based dressing

• Pair leafy greens with meat

• Add a few slices of avocado to your salad or sandwich. Avocadoes are a great source of fat that will help to boost the absorption of the vitamin K from the greens.

Recommended Dietary Intake

Unlike some nutrients that have a Recommended Dietary Allowance (RDA), Vitamin K is assigned an Adequate Intake (AI) level. This means experts have identified the amount most people need to maintain normal health and prevent deficiency, based on the best available evidence.

The current daily AI values for adults are:

• Men: 120ug per day

• Women: 90ug per day

Clinically, Vitamin K deficiency is assessed using a test called prothrombin time (a measure of how long it takes your blood to clot). Prothrombin is a clotting protein naturally present in your blood plasma, and its activity depends on adequate Vitamin K. When Vitamin K levels are insufficient, prothrombin function is compromised and clotting takes longer than it should. A longer prothrombin time is indicative of a vitamin K deficiency.

In case you're wondering what blood clotting has to do with your everyday health, think of it this way. When you get a cut, scrape, or undergo a surgery, blood clotting is a critical part of the healing process. Your blood stops flowing, crusts over, and forms a protective seal that allows the wound to close and eventually heal. Without adequate clotting, bleeding continues unchecked (a condition known as hemorrhage), which if left untreated can become life threatening. In other words, blood clotting isn't just a minor biological detail. It's a mechanism your body depends on every single day.

Additionally, as mentioned earlier, vitamin K is also important for bone health. It works with the protein osteocalcin to regulate bone mineralization. Thus, a vitamin K deficiency increases risk of osteoporosis by reducing bone mineralization.

Sources of Vitamin K

Below is a list of common Vitamin K‑rich foods along with the approximate amount they provide per typical serving:

Collard Greens 530ug

Spinach 145ug

Kale 113ug

Broccoli 110ug

Carrot Juice 28ug

Edamame 21ug

Blueberries 14ug

Grapes 11ug

Chicken Breast 10ug

Cashew 10ug

Egg 4ug

Cheddar Cheese 4ug

Milk 1ug

Who Should Pay Close Attention to Vitamin K Intake?

Certain groups should be especially mindful of their Vitamin K intake. Individuals taking warfarin (a blood thinning medication) should pay close attention, as warfarin works by disrupting Vitamin K activity to prevent clotting. For this reason, sudden changes in Vitamin K intake can interfere with how the medication works, so consistency is key. Always consult your healthcare provider before making any significant dietary changes if you are on warfarin.

Those with conditions that affect intestinal integrity and nutrient absorption are also at risk of Vitamin K inadequacy. This includes individuals living with celiac disease, ulcerative colitis, or Crohn's disease, all of which can significantly compromise the intestinal lining where nutrient absorption takes place during digestion. Similarly, individuals who have undergone bariatric surgery involving the removal or bypass of parts of the gastrointestinal tract may also be prone to nutrient malabsorption and should monitor their Vitamin K levels accordingly.

If any of these situations apply to you, speak with your healthcare provider about whether supplementation or dietary adjustments may be appropriate.

I hope this blogpost has put vitamin K on your radar. It might be a micronutrient but it most certainly packs a punch.