Healthy Living

Vitamin K

Vitamin K

The essential cofactor

Vitamin K is required for the correct mineralization of bone as it plays a role in the production of fully-formed osteocalcin, one of the proteins used in building bone. Although the exact function of osteocalcin, concerning bone health, is not completely understood, it is considered to play a role in the mineralization of bone tissue.

There is strong evidence that vitamin K not only works synergistically with vitamin D to increase bone mineral density but it positively influences calcium balance, the key mineral in bone metabolism. People with osteoporosis have been found to have lower levels of vitamin K indicating it plays an important role preventing the disease. Vitamin K is also important in helping broken bones heal themselves and is the vitamin that helps blood clot, which means it helps wounds heal properly

How much vitamin K do I need?

Adults need approximately 1μg a day of vitamin K for each kilogram of their body weight. For example, someone who weighs 65kg would need 65μg a day of vitamin K. The Vitamin K Nutrient Reference Value (NRV) is 75μg per day, a level of intake considered to be adequate to meet the known nutritional needs of practically all healthy people.

There are two naturally found forms of Vitamin K: K1 (Phylloquinone) and K2 (Menaquinone). Vitamin K1 -which plays a role in photosynthesis and is naturally present in large amounts in leafy vegetables is easily converted into the required K2 in humans. As the body is able to convert K1 to K2 you should be able to get all the vitamin K you need by eating a varied and balanced diet. Any vitamin K that your body does not need immediately is stored in the liver for future use. In addition to the natural forms of the vitamin there are also three known synthetic.

The Vitamin K recommended daily adequate intake table below is based upon information available from the the Food and Nutrition Board.

Age Male Female Pregnacy Lactation
Birth to 6 months 2 μg* 2 μg*    
7-12 months 2.5 μg* 2.5 μg*    
1-3 years 30 μg 30 μg    
4-8 years 60 μg 60 μg    
9-13 years 75 μg 75 μg    
14-18 years 120 μg 90 μg  75μg 75 μg
19-30 years 120 μg 90 μg 90 μg 90 μg
31-50 years 120 μg 90 μg 90 μg 90 μg
51+ years 120 μg 90 μg    
Source: Food and Nutrition Board, 2015        

Good sources of vitamin K

Many people don't get enough vitamin K. This isn't surprising given how few of us eat the recommended servings of vegetables and fruits each day. Phylloquinone (vitamin K1), is found in plants, such as kale, collard greens, spinach, Brussel sprouts and other green leafy vegetables. Menaquinones (a group of compounds collectively known as vitamin K2), come from animal foods, such as meat, liver, butter, egg yolks, and cheese. Vitamin K2 also is found in fermented foods, such as kefir, yogurt and natto.

Food Vitamin K (μg)
Broccoli (1 cup, 100g raw) 205
Brussels Sprouts (1 cup, 100g raw) 175
Butter (100g) 15
Cabbage (1 cup, 100g raw) 145
Cheese: Brie (100g) 57
Cheese: Chedder (100g) 15
Cheese: Gouda (100g) 76
Kale (1 cup, 100g raw) 817
Olive Oil (1 cup, 100g) 55
Parsley (1 cup, 100g raw) 540
Parsley (1 cup, 100g cooked) 900
Spinach (1 cup 100g, raw) 400
Source: Booth et. al., 2005  

Note: If you're on blood-thinning medication (coumarin-type anticoagulant, such as warfarin or nicoumalone), be sure to ask your doctor before using supplements with vitamin K. An anticoagulant is a medication which prevents the formation of blood clots in your blood vessels. Coumarin anticoagulants are sensitive to major changes in vitamin K intake, especially in people who do not receive sufficient quantities of this vitamin. You should not avoid foods or supplements that contain it, but ensure a constant intake of vitamin K. Talk to your doctor or pharmacist to find out how much vitamin K you need, especially if you're on any blood-thinning medication, as the amount of vitamin K you ingest daily may limit the effectiveness of those medicines.

Ways to increase your vitamin K intake

Many people don't get enough vitamin K1, the type found in green leafy vegetables. This isn?t surprising given how few of us eat the recommended 5 servings of vegetables and fruit each day. Use the following tips and tricks to make sure you get all the K you need:

  •  Eat your greens: Green leafy vegetables are a terrific source of vitamin K. Just one cup of cooked kale, collard greens, or spinach provides more than three times the recommended dietary allowance for vitamin K.
  •  Go healthy on fats: Whether you have your greens raw or cooked, make sure to include a little fat -such as olive oil in the meal to aid absorption of vitamin K. Adding a drizzle of olive oil makes this fat-soluble vitamin more absorbable. Most of us get plenty of fat, but if you're eating a plain spinach salad, have a healthy dressing with it.
  •  Get creative: Throw green leaves into soups and stews. Add them at the last minute, right before serving, so they are bright and flavourful on the table.