Q. I was surprised to see spinach and kale recommended as “superfoods” for heart health in your
March issue. I take Coumadin for atrial fibrillation and have been told to avoid green leafy vegetables.
I had always enjoyed these foods in the past, so I’d be glad to know if it’s okay to eat them.
A. Yes, you can eat these foods in moderation if you choose to, but check with your doctor first. Just take care to eat about the same amount on a day-to-day basis. The reason? Spinach, kale, and other leafy greens are all rich in vitamin K, which plays an essential role in forming blood clots. Warfarin (the generic name for Coumadin) helps prevent blood clots by blocking vitamin K’s actions. As a result, it’s important to keep your vitamin K levels stable, which, in turn, keeps your warfarin level stable. If your warfarin level gets too low, you risk a dangerous blood clot. If it’s too high, you risk a serious bleeding problem.
No need to avoid leafy greens if you take Warfarin
So rather than having a big spinach salad once a week, have a modest serving of a vitamin K–rich food on most days of the week if you choose to eat these foods. Broccoli, Brussels sprouts, and prunes are also good sources of vitamin K. You can look up the vitamin K content of different vegetables at health.harvard.edu/VitK. If your diet changes dramatically while you’re taking warfarin (if you’re ill or on vacation, for example), alert your doctor in case your dosage needs to be adjusted.
— Deepak L. Bhatt, MD, MPH
Editor in Chief, Harvard Heart Letter