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Vitamin K: “Ask The Expert” Column
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By Liz Pearson
I just read that vitamin K is an important nutrient, but I don’t know much about it. What is it, and do I need it?
Poor vitamin K. It doesn’t get nearly as much attention as other nutrients, but it plays a crucial role in blood clotting and, possibly, bone strength and heart health. And chances are, you’re not getting enough of it if you’re not eating vitamin K-rich leafy greens like romaine lettuce, spinach and kale every day. Don’t count on your over-the-counter multivitamin either there are only two products in Canada that contain vitamin K, but you need a
prescription for both. Health Canada recently proposed an amendment to make the vitamin non-prescription when the recommended daily dose is 120 micrograms or less. These products should be available at your drugstore soon.
Build better bones
Vitamin K may help you build stronger bones. More studies are needed, but preliminary research shows that vitamin K activates at least three proteins that appear to play a role in normal bone growth and development. A study from Boston’s Tufts University which has an entire lab devoted to vitamin K research found that women who ate the least amount of vitamin K-rich foods were more likely to have weaker bones. And in the Harvard Nurses’
Health Study involving over 72,000 women, the risk of hip fracture was 30 per cent lower in women with higher intakes of vitamin K, most of which came from green leafy vegetables.
Help your heart
While we tend to think of cholesterol as the culprit in heart disease, researchers now know that calcium can also stick to artery walls. This makes the arteries hard and brittle, which increases the risk of heart attack because they are unable to dilate properly in the event of a clot or blockage. Research is ongoing, but both test tube and animal studies show that vitamin K may help prevent this calcium buildup.
Get your greens
How much vitamin K do you need? Some vitamin K is made in your body by the bacteria that line your gastrointestinal tract, but you also need to get vitamin K from food. The recommended daily allowance for adequate vitamin K intake is currently 90 mcg daily for women and 120 mcg for men. Some researchers believe even higher amounts are required for optimal bone and heart health, but further studies will help clarify this issue.
- Both raw and cooked veggies are good sources of vitamin K. Add one cup (250 ml) of finely chopped kale to your minestrone soup to up your vitamin K intake by a whopping 547 mcg. A delicious small (one cup/250 ml) spinach salad contains 145 mcg; a small caesar salad, 48 mcg. Or how about half a cup (125 ml) of brussels sprouts (78 mcg), cooked broccoli (110 mcg) or asparagus (45.5 mcg).
- Consume small amounts of healthy oils like canola and soybean. Products made from these oils, like salad dressing, margarine and mayonnaise also contribute significant amounts of vitamin K to the diet. For example, one Tbsp (15 ml) of soybean oil contains 19 mcg of vitamin K, one Tbsp (15 mL) of canola oil contains 17 mcg, and one Tbsp (15 ml) of low calorie mayonnaise has 3.5 mcg.
- If you are taking the blood thinner medication warfarin (also known as coumadin), ingesting a lot of vitamin K may reduce its effectiveness. Don’t cut vitamin K rich foods out of your diet completely, though. It’s better to maintain a regular intake of this nutrient each day so that warfarin levels also remain constant. Talk to your doctor.
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