Blood Thinners and Broccoli

People taking anticoagulants are usually told to avoid broccoli, spinach, and other super-healthy veggies. Nutrition Diva has a better idea.

Monica Reinagel, MS, LD/N, CNS
4-minute read
Episode #187

Annie writes:

“I recently developed a blood clot in my leg and my doctor put me on blood-thinners. The nurse handed me a print-out of foods that I shouldn’t eat because they would interact with the medicine—things like broccoli, kale, spinach, and Brussels sprouts. Since starting to listen to your show, I’ve been trying to eat more vegetables and I’ve been eating lots of the foods on this list. Could eating too many vegetables have caused my blood clot?”

Your efforts to eat something good for me didn’t backfire, Annie! The vegetables on this list are all high in vitamin K—an important nutrient that helps strengthen bones and protects against hardening of the arteries. But vitamin K gets its name from the German word for coagulation (which, in German, is spelled with a “k”). That’s because in addition to its many other jobs, this nutrient is required for proper blood clotting.

If you don’t get enough vitamin K in your diet, you might bruise easily or it might take a long time for a paper cut to stop bleeding. However, the opposite is not true: getting a lot of vitamin K in your diet doesn’t make you more likely to form a blood clot in a blood vessel. 

Blood clots in the leg (also known as DVTs) are more likely to be caused by sitting for too long, such as on a long flight. Being laid up in bed for an extended period of time due to illness or injury can also increase the risk of DVTs, as can smoking or taking birth control pills or hormone replacement therapy.  DVTs can cause pain and swelling, usually in the calf. But the real danger is that a piece of the clot might break free and travel through the circulatory system to the lungs or heart, where they can really wreak havoc.

Diet and Anticoagulants

Doctors use anticoagulants (or blood-thinning drugs) to help dissolve a blood clot before it causes trouble—or to prevent one from forming in the first place in people who are at increased risk. But giving anticoagulant medication is a delicate balancing act. You want to block enough of the coagulating activity to prevent inappropriate blood clotting, but not so much that you cause uncontrolled bleeding or hemorrhage elsewhere in the body.   People taking blood-thinning medications have regular blood tests to be sure that the dosage is just right. And that’s where the vegetables come in.

Anticoagulant drugs work by blocking the action of vitamin K. The more vitamin K you’re consuming, the higher your dosage would need to be. Now, that wouldn’t be a problem if you consumed more or less the same amount of Vitamin K every day.  Your dosage could be adjusted to accommodate that intake. But if your vitamin K intake fluctuated wildly from day to day, it would make it very hard to keep your coagulation levels in the target zone. And that’s why people who are prescribed blood-thinning medications are often advised to avoid vitamin K-rich foods altogether. It just keeps things simpler.


About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.