Vitamin K plays a major role in blood clotting, as it is needed by many of the proteins that help blood clot. However, that means vitamin K works at cross-purposes with the warfarin:
Large quantities of dietary or supplemental vitamin K can overcome the anticoagulant effect of vitamin K antagonists [e.g., warfarin], so patients taking these drugs are cautioned against consuming very large or highly variable quantities of vitamin K in their diets. Experts now advise a reasonably constant dietary intake of vitamin K that meets current dietary recommendations (90-120 mcg/day) for patients on vitamin K antagonists like warfarin (source).
Foods highest in vitamin K include kale (660 mcg per half-cup cooked) and collard greens (520 mcg per half-cup cooked). While the majority of the American public is not in danger of consuming high doses of vitamin K, and some would rejoice rather than mourn upon being instructed to severely reduce or eliminate these foods, our regular diet is a bit different than the majority of the American public, to put it mildly.
Matthew started taking warfarin just as our garden-grown greens (kale, collards, and Swiss chard*) really hit their stride. We’ve been harvesting huge grocery bags full every week, and that seems to barely make a dent in the supply.
Clockwise from top: kale (one of two varieties we grow), perpetual spinach chard, rainbow chard, collards, and some other kind of chard.
I prefer to be the one doing the harvesting, as Matthew’s idea of how many greens we can consume in a week (not to mention how much we can stuff into our poor refrigerator!) is a bit more optimistic than mine.
Fortunately, Matthew’s hematologist gave him the green light for continuing to eat a full serving of greens every day, with the caveat that he keep intake consistent. Thus, while he previously wouldn’t have eaten a half-cup of cooked kale or collards every day, doing so is now part of his “medical” regimen.**
The garden continues to produce in abundance, so supply is not a problem, though it was a bit tricky when we separated from the garden for our trip to Wisconsin. We kept up the intake with lots of frozen grocery store spinach (560 mcg per half-cup cooked) — those little frozen boxes were convenient, but not near as tasty.
One thing I’ve discovered is that summer kale and chard do not at all resemble the tender leaves that I cook in spring, when I toss the still-damp, cut, rinsed leaves in our biggest cast iron skillet, cover to steam for a couple of minutes, and then finish uncovered, sauteing with a bit of oil, salt, and garlic.
Summer kale is a different beast entirely, with tougher, chewier leaves not suited for light cooking (or raw kale salads). It will just laugh at those preparation methods as you sit trying to chew a mouthful of tough greens.
Much as I cringe at boiling those beautiful, nutrient-packed leaves, a girl’s gotta do what a girl’s gotta do. Fortunately, there’s a happy medium between gross, boiled-to-death, pile of mush and too-tough-to-chew.
cooking hot-weather greens
Wash and chop the greens. Bring a large pan of salted water to a boil. Add your prepped greens to the boiling water. Return to low boil and cook for 10-15 minutes. Drain.
Now the greens are ready to be sauteed with onion and garlic or tossed into some kale-quinoa quiche.
A recent dinner: stuffed zucchini with a side of garlicky sauteed collards.
If greens are half the “superfood” that some people claim, Matthew is well on his way to becoming Clark Kent!
*Chard is lower in Vitamin K, with about 360 mcg per half-cup cooked, which means eating about two servings a day.
** This post is not intended as medical advice. If you are on anticoagulant/blood thinner medication, consult your physician before increasing your intake of vitamin K-rich foods.