Vitamin K
Daily Value: 80 micrograms
Good Food Sources: Cauliflower, broccoli and green, leafy vegetables such as spinach and kale
Unless you were born within the past couple of minutes, your chances of having a vitamin K deficiency are pretty slim.
Your body needs such tiny amounts of this nutrient to help blood clot when you're injured--this is vitamin K's primary job--that you most likely get more than enough without making any effort at all. You can even manufacture your own vitamin K. About half of the vitamin K your body needs is normally produced by your own intestinal bacteria.
Babies are the big exception. They lack the bacteria necessary to produce vitamin K, and they're usually not up to a diet of green, leafy vegetables for quite a while. And although breast milk has a small amount of the nutrient, it's one of the few instances in which breast milk is simply not enough. So babies are generally given a shot of vitamin K at birth.
The only other folks who need an extra boost of supplemental vitamin K are those who have a digestive disease such as cystic fibrosis, says James Sadowski, Ph.D., chief of the vitamin K laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston.
But there are some folks who are afraid that they get too much vitamin K. Many people who are taking anticoagulants, or blood thinners, to prevent heart attack and stroke actually cut down on the amounts of green, leafy vegetables they eat because they're afraid that their lettuce will trigger the same events that their medications are trying to prevent.
"This is absolutely wrong," says John W. Suttie, Ph.D., professor and chair of nutritional sciences at the University of WisconsinMadison. "Physicians tell a lot of people whom they put on anticoagulants to limit their vitamin K intakes. I don't know why they do this, but it's fairly common. It is not good advice."
Dr. Sadowski agrees. "If someone is on oral anticoagulants because he has had a heart attack, a stroke or blood clots in his legs, he should keep his vitamin K consumption at a fairly constant level every day. But it probably doesn't matter how much he's getting as long as it's pretty close to the same thing every day."
The reason? Every individual's anticoagulant dose is custom-tailored to his particular needs, says Dr. Suttie. Those needs are identified through a series of blood tests when the anticoagulants are started. The amount of anticoagulant then prescribed is intended to strike a very delicate balance, giving your body enough vitamin K to clot and heal wounds but not enough to clot and cause a heart attack.
Using Vitamin K Safely
Since your body can absorb vitamin K only when it's accompanied by dietary fat, it's best to eat your leafy greens with a food that contains at least some fat. A dollop of oil-based salad dressing on a bed of greens or even a serving of lettuce on a lean burger will make sure your vitamin K is there when you need it.
