How to safely enjoy all the healthful foods you’ve been warned about…

Could a spinach salad ever be considered dangerous? That may sound impossible. But if you’re one of the millions of Americans who takes the popular blood thinner warfarin (Coumadin, Jantoven, Marevan, etc.) to help prevent stroke, heart attack or pulmonary embolism,  chances are your doctor has told you to limit your intake of spinach and other vitamin K–rich foods.

It’s true that vitamin K promotes blood clotting, and consuming too many foods that contain abundant amounts of this nutrient could weaken warfarin’s effect.

Taken to the extreme, however, this dietary advice often causes warfarin users to become fearful of eating any of the highly nutritious foods that contain vitamin K.

What many people don’t realize is that following this guideline too strictly creates almost as much of a problem as getting too much of this crucial nutrient, which has been shown to promote heart and bone health.

The solution: There is a simple way that you can have your warfarin—and your green veggies, too! Here’s how…


If you watch TV, you’ve no doubt seen plenty of ads for the newer generation of blood thinners, such as apixaban (Eliquis), rivaroxaban (Xarelto) and dabigatran (Pradaxa). These medications work similarly to warfarin by blocking production of blood-clotting proteins in the body, but they use a different mechanism that doesn’t require vitamin K vigilance.

Even though these newer blood-thinning drugs are being prescribed more and more, warfarin is still the most widely used medication for stroke and heart attack patients.

But the use of warfarin requires a delicate balancing act that weighs the risk for excessive bleeding against the risk for unwanted clotting. To keep tabs on how long it takes a patient’s blood to clot, frequent blood testing is used (initially on a daily basis, then gradually decreased until a target level has been reached) to determine the patient’s INR, which stands for “international normalized ratio.” For most patients, the target for this standardized measurement ranges from about 2.0 to 3.0.

Other risks: In addition to the dietary considerations, warfarin interacts with a number of medications (such as certain antibiotics, other heart medications, cholesterol drugs and antidepressants) as well as supplements (including St. John’s wort and ginkgo biloba).

Dr. Harlan’s stay-safe formula: There is no definitive research pointing to optimal levels of vitamin K for warfarin users, but I find that most patients thrive on a plan in which their daily intake of this vitamin is about 75 micrograms (mcg) per day—a level that is lower than the recommended daily allowance for adults (90 mcg per day for women…and 120 mcg per day for men). That intake of vitamin K seems to strike the balance between offering an adequate amount of healthful foods rich in the vitamin while allowing warfarin to do its job.


It’s amazing to see how much the vitamin K content varies depending on the food. Some foods are absolute vitamin K powerhouses—one cup of raw parsley, for example, has a whopping 984 mcg…one cup of cooked spinach contains 888 mcg…and one cup of raw kale, 547 mcg. Note: Cooking a vegetable will decrease its volume, but won’t change the vitamin K content.

To avoid slipping into a vitamin K danger zone, I advise warfarin users to regularly incorporate vegetables with low-to-moderate amounts of vitamin K into their diet (up to 20 mcg per serving).

Good choices (serving sizes are one cup unless otherwise indicated): Arugula (one-half cup), beets, carrots, celery (one stalk), corn, eggplant, sweet red or green peppers, peas (one-half cup), turnips, tomatoes and zucchini. 

Other foods that are naturally low in vitamin K include most fruits, cereals, grains, beans, seeds and tubers (such as white potatoes, sweet potatoes and yams).

A good rule of thumb: Stick to side dishes with 20 mcg to 25 mcg of vitamin K per serving and main courses with 35 mcg to 40 mcg per serving. That should keep you at a safe level.

But what if you reach your daily limit and are still craving some sautéed greens or a big kale salad? Don’t despair. You can still enjoy these foods…as long as your intake of vitamin K is consistent.

This means that you can exceed 75 mcg of vitamin K per day—but you must consume the same amount of the vitamin every day. So you can have a spinach salad, but you need to eat the same-sized salad (or another dish with an equivalent amount of vitamin K) every single day.

Important: Be sure to first tell your doctor if you plan to increase your intake of vitamin K so that you can be closely monitored and, if needed, your dose of warfarin adjusted. The frequency of monitoring depends on the patient’s specific circumstances.

To find the vitamin K content of various foods: Go to


Unless you’re a nutritionist, you probably don’t know the vitamin K content of most foods off the top of your head. To help you stay safe when you’re close to reaching your limit of the vitamin, here are some healthful foods that contain virtually no vitamin K in a single serving…

Acorn squash…raw mushrooms…cooked grits…yellow sweet pepper…cooked salmon, halibut or sole…cooked pork…light-meat turkey (no skin)…lemon, lime or orange…almonds…nonfat sour cream…rosemary, garlic powder or ground allspice, ginger or nutmeg.