Can You Eat Kale If You Take Blood Thinners or Aspirin? Here's What Health Experts Say

The key is consistency.

Reviewed by Dietitian Maria Laura Haddad-Garcia

Packed with nutrition and versatility, kale, a non-starchy cruciferous vegetable, is often referred to as a superfood. That said, superfood is a marketing term (not scientific), and not one food provides all the nutrients we need. Key nutrients found in this veggie include vitamin C, plant-based calcium, glucosinolates and antioxidants like beta-carotene, lutein and zeaxanthin.

Kale also contains ample amounts of vitamin K, a fat-soluble vitamin that assists in blood clotting and bone health. Because of its vitamin K content, people who take certain blood-thinning medications may wonder if they should avoid eating kale and other foods high in vitamin K due to drug-nutrient interactions.

Read on to learn more about the connection between kale and blood thinners, plus ways to safely eat kale if you’re on these medications.

Related: 4 Supplements You Shouldn't Be Taking If You Have High Blood Pressure, According to a Dietitian

What Are Blood Thinners?

The technical terminology for blood thinners is anticoagulants. Anticoagulants are often prescribed to people who have heart or blood vessel diseases, atrial fibrillation, are at risk of clots after surgery, have had a heart valve replacement, heart attack or congenital heart defects. The American Heart Association lists common brands as:

• Apixaban (Eliquis)

• Dabigatran (Pradaxa)

• Edoxaban (Savaysa)

• Heparin (various)

• Rivaroxaban (Xarelto)

• Warfarin (Coumadin)

Marlyene Perez, M.S., RDN, a registered dietitian nutritionist from Top Nutrition Coaching, says, “Blood thinners, also known as anticoagulants, are medications that prevent the formation of blood clots. They do not “thin” the blood; instead, they interfere with the blood clotting process to reduce the risk of clot formation.” They increase the amount of time it takes for your blood to clot.

But “Not all blood thinners interact with vitamin K. If you are prescribed a blood thinner, you should contact your physician about the effects of your specific medications,” notes Maria Fraga, RD, CDCES, CDN, a registered dietitian and director of the Diabetes Alliance at the Mount Sinai Health System.

For example, Peggy Kraus, M.A., RCEP, CDCES, a registered clinical exercise physiologist and certified diabetes care and education specialist with Peggy Kraus Coaching, says, “There are no food-drug interactions with the newer antiplatelet medications such as Rivaroxaban (Xarelto), Dabigatran (Pradaxa) and Apixaban (Eliquis).”

Aspirin, a pretty common medication, is an antiplatelet, which prevents platelets from clumping together to form a clot and is often prescribed to people who have had a heart attack or stroke.

How Vitamin K Helps with Blood Clotting

Vitamin K is one of the four fat-soluble vitamins and plays a role in blood clotting and bone health. Perez says, “Vitamin K helps synthesize various proteins, ‘clotting factors,’ such as prothrombin. Without sufficient vitamin K, these factors are not activated, and the clotting process is impaired.” For example, when you get a cut, vitamin K synthesizes the proteins that help the blood to clot so you stop bleeding.

Does Kale Interact with Blood Thinners?

As mentioned above, kale contains ample amounts of vitamin K. One cup of raw kale contains 80 micrograms (mcg) of vitamin K, or about 66 to 89% of the recommended daily intake. And research shows that cooking kale can increase the vitamin K content because heat causes vitamin K to be released. Because of this, people on these medications may think they should avoid kale and other foods high in vitamin K. However, the issue is when they eat them inconsistently or in large quantities.

A sudden change in the amount of vitamin K you consume can cause dangerous bleeding (if you consume less) or blood clots (if you consume more). “It’s not about avoiding vitamin K, rather the importance of keeping vitamin K intake consistent on a daily basis,” notes Fraga.

Perez says that if kale is eaten in inconsistent amounts, “The vitamin K can interfere with the balance of clotting factors and influence the effectiveness of the warfarin.” It counteracts the effects of the blood thinner.

Tips for Consuming Kale Safely

The best way to make sure your medications are working as they should is to consume consistent amounts of foods, kale and other green leafy vegetables which are rich in vitamin K.  “Maintain consistent, portion-controlled vitamin K intake to avoid instability of the anticoagulant effects of the medications and regularly monitor blood clotting parameters like the International Normalized Ratio (INR) to assess your diet and medications effectiveness,” says Perez.

If you need more clarification about portion sizes and blood clotting monitoring, contact your health care team for guidance. The key is to be consistent. For example, ”If you have a serving of kale or broccoli one day, you should plan to have a serving the next day. The idea is to keep your vitamin K intake consistent,” Fraga recommends.

Related: Healthy Kale Recipes

Other Foods to Consider

While you don’t have to avoid foods that contain vitamin K altogether, eating a variety of nutrient-dense vegetables is important for overall health.

“If you are concerned about the vitamin K content of kale or other cruciferous veggies, consider alternative veggies that have lower vitamin K content like cucumbers, tomatoes and bell peppers,” says Perez. Kraus adds, “Sweet potatoes, winter and summer squash, eggplant, corn, mushrooms and turnips are also low in vitamin K.”

Other foods and beverages that might impact the effectiveness of your blood thinners or aspirin include alcohol, herbs and other green leafy vegetables. For people who take warfarin, occasional drinking can lead to internal bleeding, and heavier drinking may cause bleeding of the opposite, resulting in possible blood clots, strokes and heart attacks.

Frequently Asked Questions

What foods cannot be eaten with blood thinners?

If you’re on blood thinners, you don’t need to avoid specific foods but moderate those high in vitamin K to prevent drug-nutrient interactions. Caution is warranted if you consume alcohol, as alcohol can increase the effects of blood thinners.

Do green vegetables thicken or thin the blood?

Green vegetables contain vitamin K, an essential nutrient involved in blood clotting.

Can you eat peanut butter on blood thinners?

Peanut butter does not contain large amounts of vitamin K, but it contains vitamin E. Taking vitamin E (as in supplements) with a blood-thinning medication can increase anti-clotting activity and increase your risk of bleeding. But eating peanut butter should not yield the same results. A two-tablespoon serving of peanut butter provides about 20% of the daily value of vitamin E.

The Bottom Line

Before modifying your dietary intake of kale, ask your health care provider if it interferes with your blood-thinning medication. Most likely, you don’t have to avoid it or other green vegetables (spinach, cabbage, Brussels sprouts, collard greens), but aim for a consistent daily intake instead. Working with a registered dietitian or another health care professional is best for individualized recommendations.

Read the original article on Eating Well.