How Do Heart Meds and Food Interact?

Can your diet affect how your medication works? Find out in our latest podcast episode as we explore the relationship between dark green leafy vegetables and grapefruit, with certain prescription drugs. Get ready for a dose of eye-opening insights into the intersection of food and medicine.

Shownotes: yournutritionprofs.com

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Transcript

Everyone knows fruits and vegetables are good for you. But did you know that there are some fruits and vegetables that should be avoided when taking certain medications? In this episode we will discuss dark green leafy vegetables and grapefruit and their possible interactions with some cardiac medications.  

M: I’m Professor Megan 

S: and I’m Professor Susan, and we’re

Both: Your Nutrition Profs!

M: We are registered dietitians and college professors who have taught more than 10,000 students about health and nutrition. We have answered a LOT of questions about nutrition over the years – 

S: Some questions we get asked every year and some are rarely asked but very interesting.

M: We’re here to share our answers to these common (and uncommon) nutrition questions with you.

S: So bring your curiosity and let’s get started. 

Both: Welcome to our class!

S: Today we have a special episode for you. As you may know, February is American Heart Month. 

M: Since its inception in 1964, the purpose of American Heart Month is to raise awareness that heart disease is the leading cause of death in the U.S. and to share ways we can reduce our risk. 

S: And today we have two really good questions to answer. Both have to do with food and drug interactions. We’ve decided to share this episode now in February, as the main drugs we will be discussing are related primarily to cardiovascular disease. 

M: While these are not the most common of questions, when I do get them in class, it usually happens early in the semester when we’re just starting off talking about the importance of consuming a variety of fruits and vegetables. 

S: Right.

M: And someone will ask, “If dark green leafy vegetables are so good for you, then why did my grandmother’s doctor tell her she can’t eat them?” 

S: Right, I get that one a lot too. Or another common question is, “Why was my mother told not to eat grapefruit? We just talked about how great they are!”

M: It can be confusing. But some commonly prescribed medications interact with fruits and vegetables and today we’re going to talk about it.

S: That sounds good, so let’s start with leafy green veggies, I call them DGLV.  What are they? Well they’re just like they sound. They’re dark green and leafy and there are a lot of vegetables in this category – kale, spinach, romaine lettuce, greens (like collard, or mustard or beet greens), swiss chard, arugula, endive, watercress, cabbage, and even bok choy. 

M: And if you haven’t heard of some of those, don’t worry, you’re not alone. 

S: There are many, many options! Greens like bok choy or watercress, they are a little bit more unusual so stay tuned! We may actually do a snackisode about them.

M: And typically consuming more of these greens is recommended! The most recent Dietary Guidelines for Americans recommend that you consume at least 1.5 cups of dark green vegetables per week for most adults. 

S: But it’s really important to note that in this instance 1 “cup” or 1 serving of raw leafy greens would actually be measured out as two 8oz servings. So to meet the 1.5 cup recommendation, you’d actually need to consume ~three 8oz servings. A regular pre-washed bag of spinach or mixed greens at the grocery store is usually between 6 and 10 oz, so to meet the recommendation you’d have to eat 2-3 bags of these raw spinach or leafy greens per week. 

M: That seems like a lot, but think about all of the air in those bags. And then if you cook the greens then the 1 cup is equivalent to 1 serving. And 1 cup is about the size of your fist. 

S: Your Nutrition Profs always recommend consuming more whole fruits and veggies unless there is a medical reason not to. And dark green vegetables are really nutrient dense. They’re low Calorie, they’re a good source of fiber, several B vitamins, vitamins A, C, K, and several phytochemicals. There’s a lot of research showing that consuming these veggies reduces your risk of several chronic diseases. 

M: Yes. But unfortunately, reports suggest that only 25% of adults in the U.S. consume dark green vegetables at all on a given day. This is the lowest of all categories of vegetables. 

S: That is really too bad. 

M: Yeah. 

S: I mean, a lot of people think you can only eat these greens raw like in salads, but they’re really very versatile! You can add them to soups and stews, like I usually add them to chili. They can be sauteed with veggies, added to egg dishes – all sorts of things! So you can sneak them into dishes that wouldn’t normally have them, like spaghetti or quiche, things like that. Then you can up the nutrient profile that way. And most of the time people don’t even notice they’re there.!

M: So true. If DGLVs have all these good benefits, why would anyone need to avoid them? 

S: It is a good question and the most common reason to minimize these leafy greens given by health professionals is because of their vitamin K content. Vitamin K is a really  important fat-soluble vitamin that is most well known for its role in blood clotting. 

M: Vitamin K is not just found in dark green leafy vegetables, it's also found in some vegetable oils, fruits like blueberries and figs, and even pumpkins. And while it's also necessary for the production of bone tissue, it is its role in blood clotting that is the focus of our question today. 

S: Right, and in general, blood clotting is a good thing. 

M: Yes! 

S: Right, you cut yourself, you’re bleeding, you want it to stop. Blood clotting at the site using proteins is what stops your blood loss, and these blood clots require vitamin K in order to form. 

M: But in some situations, usually for people with certain cardiovascular disorders, blood clotting is not always a good thing.

S: Right. Excessive blood clotting can actually be dangerous. Clots can form and then travel through your blood vessels, and if these vessels are narrowed by plaque buildup or if the clots are large, they can get stuck. This can cause harmful consequences, things like a heart attack, or a stroke, or even organ damage. 

M: If your doctor thinks that you’re at risk for these blood clots, you will often be prescribed blood thinners, also known as anticoagulants. Coagulant is a sciencey word for blood clotting. Blood thinners can help prevent the formation of blood clots and reduce the size of existing clots.

S: One group that takes these blood thinners are those with a heart condition called atrial fibrillation, or Afib. This is where the upper chambers of the heart, called the atria, don’t contract properly. This can cause blood to form a clot that can then travel to other parts of the body like the brain and cause a stroke. 

M: Another condition, deep vein thrombosis, also called DVT, occurs when a blood clot forms in a deep vein, usually a leg, but it could also occur in the upper extremities. A clot could also break loose and travels to the lungs, which is called a pulmonary embolism and that can be life threatening. 

S: Risk factors for DVT include being over 40, having a family history of blood clots, having excess body weight, smoking, and having long periods of inactivity. And that’s why it’s recommended to wear compression socks and to take walks in the airplane when you're taking long flights.

M: And those who have mechanical heart valves are also at increased risk of having blood clots. Ok, basic heart anatomy recap…

S: Don’t freak out. 

M: The heart has four chambers.

S: Right, we already talked about the upper two chambers, the atria. 

M: …Well the two lower chambers are the ventricles and we have four valves that control the flow of blood between these four chambers. Sometimes these valves can become damaged due to again narrowing from plaque buildup or regurgitation. 

S: Right, regurgitation in the heart occurs when a valve doesn’t close completely and blood leaks backwards into the chamber where it came from. Like when one of your doors doesn’t quite close all the way and cold air leaks in. This can occur as a result of a congenital heart defect, or damage to a valve following a heart attack or if you’ve had rheumatic fever. In some cases, a mechanical or artificial heart valve is needed and that will replace the damaged one. 

M: There are also some genetic clotting disorders that may require blood thinners to reduce risk of complications. And there’s also often an increased risk of blood clots following certain medical procedures and surgeries, so blood thinners may be prescribed temporarily. 

S: Right, that's really common. So that’s why patients with any of these conditions may be prescribed these blood thinners, something that would decrease the chances of having clots. 

M: One of the most widely prescribed blood thinners is warfarin, which is sold as Coumadin. 

S: Yeah, many of my family members take coumadin. It works specifically by blocking an enzyme that activates vitamin K in the body that way with less vitamin K, this would reduce blood clot formation. 

M: So vitamin K from foods such as DGLVs can decrease the effectiveness of this drug in the body. So this interaction is why people taking Coumadin need to be aware of their dark green leafy vegetable intake. 

S: But they usually don’t have to avoid them completely, right? Consistency is key. Your body needs to maintain a balance of vitamin K and Coumadin in the system. 

M: Right. People on this drug have to have their blood levels regularly checked to make sure the drug is still working effectively. So they can still consume some DGLVs, but don’t go crazy and consume a whole bunch in a few days if that’s not what you normally do.

S: Right. So be consistent with your intake. A randomized controlled study evaluating dietary vitamin K intake and the use of anticoagulants was conducted recently.

• Half of the subjects attended diet-related counseling sessions and cooking lessons that included general nutrition information. The other half attended the same sessions but instead of general information, they got information with a focus on increasing green vegetables and vitamin K-rich oils and herbs. 
• After six months, those who got the vitamin K lessons maintained more stable anticoagulation levels better than those who only received the general nutrition lessons.

M: And the counseling sessions were promoting consumption of vitamin K in those taking Coumadin.

S: Exactly. And those who were increasing vitamin K had more consistent levels of the drug. I’ll have to tell my family members, who are on Coumadin, that they can eat a moderate amount of DGLVs regularly! I mean, one of them definitely doesn’t eat any… I think he uses it as an excuse because he’s not a fan of vegetables in pretty much any form….

M: Well there goes his excuse. So the official FDA prescription information for Coumadin, states “the amount of vitamin K in food may affect therapy with COUMADIN. Eat a normal, balanced diet maintaining a consistent amount of vitamin K. Avoid drastic changes in dietary habits, such as eating large amounts of green leafy vegetables. You should also avoid intake of cranberry juice or any other cranberry products.”  

S: So that’s pretty clear evidence that it’s ok to consume at least some DGLVs while you're on blood thinners. I mean, consistent intake is the goal. So if your diet changes significantly or you have specific concerns or questions, check with your healthcare provider. 

M: And just a note about that last sentence about cranberry juice.

S: Yeah.

M: That sort of came out of left field. 

S: Surprising. 

M: There is some evidence that flavonoids in cranberry juice can inhibit an enzyme responsible for the metabolism of Coumadin. But more research is needed. 

S: Right, so that’s a totally different deal than the vitamin K deal. 

M: Yes. Most recommendations say that, like DGLV, don’t go crazy on cranberry juice but you can consume some. 

S: Alright but back to vitamin K. Is this “avoiding vitamin K” true for all blood thinners? I know there are others on the market besides Coumadin.

M: Good question. Not all blood thinners interact with vitamin K. Newer anticoagulants like Xarelto, Pradaxa, and Eliquis are not noted to have any food-drug interactions. 

S: So I also have family members taking some of these. They don’t have any DGLV restrictions – great.

M: And before we move on from leafy greens, we do want to mention that there are a few other health conditions where limiting DGLVs may be warranted. 

S: Right, like kidney disease… When your kidneys aren’t functioning correctly, it can be difficult to filter out some waste products and people can end up having very high levels of potassium in their systems. Because leafy greens like spinach, and swiss chard, and beets and all those other that we mentioned are fairly high in potassium, those with severe kidney disease may need to limit their intake. 

M: And the same is true for those prone to kidney stones. They may also benefit from limiting their spinach and swiss chard but for a different reason. Instead of the high potassium you may limit leafy greens due to their oxalate content. 

S: Right. Oxalates, or oxalic acids naturally occur in plants. Small amounts are fine, but larger amounts may prevent the absorption of some minerals like calcium, and can increase the risk of kidney stones in those who have already had kidney stones. 

M: All that being said, check with your health care provider or registered dietitian before cutting out whole groups of foods like leafy greens. And in general for most people, consuming more fruits and vegetables is better.

S: Right, so moving on to our second question, why should some people avoid grapefruit consumption? 

M: Well first, let’s give some background on the grapefruit. It’s a cross between an orange and a pomelo and it’s actually the youngest of all the citrus fruits.

S: That’s really interesting. 

M: I know, it’s only been commercially grown for the past 200 years or so. 

S: Wow, and Texas, particularly the lower Rio Grande Valley, is the 2nd largest producer of grapefruit after Florida and you can see them growing in people’s yards all over South Texas, including my mother-in-laws!

M: There are basically three major types that exist today: white, pink/red, and ruby red. And they have a sweet and tangy flavor.

S: And grapefruit is nutrient dense. It provides significant amounts of vitamins A and C. It would have been a good cure for scurvy that we talked about on our last episode! It's also a good source of fiber, potassium, and magnesium. But beyond nutrients, it provides several phytochemicals including flavonoids, carotenoids, coumarins, terpenes, and limonoids. 

M: Research suggests that grapefruit juice may reduce plaque formation in arteries and inhibit breast cancer cell proliferation. 

S: And of course, there’s the grapefruit diet, which originated in the 1930s, but became much more popular in the 1970s and 80s. 

M: Oh yes, the grapefruit diet. For those of you that may be unfamiliar, the grapefruit diet is thought to be one of the oldest fad diets around. So like Susan said it’s been traced back to the 1930s and is linked to the film industry, which makes sense considering that the grapefruit diet is also known as the Hollywood diet. 

S: There are several different variations of the diet and most commonly involve eating a grapefruit or drinking grapefruit juice with each meal along with meat, eggs and other high protein and high fat foods. You’re also supposed to avoid other carbohydrates including other fruits, grains, and several vegetables.

M: So essentially a low carbohydrate diet and lots and lots of grapefruit. 

S: And it was meant to be followed for 10 to 18 days and then you cut your Calories down to 500 to 800 a day. The belief was that grapefruit contains specific enzymes that burn fat. 

M: This is, of course, not true. 

S: Whaaaaat? I am shocked that a fad diet is based on something that’s not true!

M: But speaking of enzymes…..

S: Yeah, let’s get back to the question, why should grapefruit be avoided by some people? 

M: Enzymes! 

S: Oh my gosh! 

M: Grapefruit juice causes a quick and irreversible inhibition of the cytochrome P450 enzyme system within the small intestine. 

S: That is some fancy science for you! The cytochrome P450 enzyme system. Well one of the important functions of the enzymes in this system is to metabolize or process substances like drugs by breaking them down into manageable pieces. This helps your body get rid of substances that are harmful or that it no longer needs. So this cytochrome P450 system- it’s pretty important!

M: Yes, so how does grapefruit inhibit or interfere with this system? Well, grapefruit contains high amounts of chemical compounds called furanocoumarins that serve as a defense mechanism for the plant against being consumed. Which is really pretty cool if you think about it. 

S: That is pretty cool! I mean, it’s great for the plant but it’s not necessarily great for us. 

M: True.

S: It’s these compounds that can slow down the ability of specific enzymes in this cytochrome P450 system to process substances. This can lead to a delayed breakdown of certain medications and that can result in medication remaining in the body for longer than it’s supposed to or higher levels of medication in the bloodstream. And both of these could lead to toxicity.

M: This enzyme interference is most well known for cardiovascular related medications such as those prescribed to lower blood cholesterol. 

S: You may have heard of statin drugs. These reduce how much cholesterol a person produces. Less cholesterol may reduce risk of atherosclerosis which is a sciency word for the narrowing and hardening of the arteries and this hardening of the arteries can potentially lead to a heart attack or a stroke.

M: The most commonly prescribed statins in the U. S. today are atorvastatin sold as Lipitor, simvastatin sold as Zocor, and rosuvastatin sold as Crestor. But not all statins are affected by grapefruit. For example,  Lipitor and Zocor are, but Crestor is not. 

S: I actually take Crestor for my cholesterol levels and so I don’t have to avoid grapefruit. 

M: Nice! Well in addition to these, there are actually several other drugs that may be negatively impacted by grapefruit as well. These include drugs that treat high blood pressure like nifedipine, sold as Procardia and some that treat abnormal heart rhythms like amiodarone, sold as Cordarone.

S: Grapefruit may also interfere with several chemotherapy drugs, organ-transplant rejection drugs, and some corticosteroids such as those used to treat Crohn’s disease and ulcerative colitis.

M: It can also interfere with some anti-anxiety medications, like buspirone, sold as Buspar, erectile dysfunction drugs like sildenafil sold as viagra, and even some antihistamines, such as fexofenadine, which is sold as Allegra.

S: You know that last one really surprised me! I mean Allegra is a really common over-the-counter allergy medication!

M: Oh definitely. I actually took Allegra for quite some time in my youth for allergies and I’m pretty sure I was never told to avoid any particular food or drink.  Although to be fair, for some of these drugs the warning is “use grapefruit with caution” as opposed to “avoid grapefruit”. 

S: Well most of the drugs we’ve mentioned experience a delayed enzyme response with grapefruit which means that the drug won’t be broken down and removed from the body as fast, but with Allegra grapefruit works differently…

M: Right. In Allegra a specific transporter is impacted leading to too little of the drug being absorbed from the intestines and so you may not have enough in your system to help with your symptoms. And other fruit juices, like orange and maybe even apple may also inhibit this transporter.

S: So grapefruit causes the opposite to happen in Allegra than it does in the statins?

M: Yes.

S: Interesting…. 

M: I know!

S: So how much grapefruit is too much? 

M: Excellent question… and I don’t have the answer. It really depends on the severity of the interaction and that is dependent upon the person and how much the enzyme they produce, which drug they’re taking, how much of the drug they are taking, and of course, the grapefruit. 

S: So it sounds like it’s really important that if you’re on these types of medications that you have your levels regularly checked to make sure they’re actually working correctly. 

M: Yes and if you are curious about any of your medications and reactions with any foods or beverages, please, make sure to speak with your healthcare provider or pharmacist. 

S: Ok, so we’ve covered a wide variety of information here. So let’s bottom line it. 

M: Ok, bottom line for blood thinners and dark green leafy vegetables. The  general consensus is that it’s ok to consume moderate amounts of DGLVs.

S: If you’re taking coumadin. 

M: Yes.

S: So instead of cutting out those DGLVs completely, you need to just be consistent in your consumption. Consider consuming a spinach salad or something like that on a regular basis because they are super nutrient dense.

M: And as for grapefruit? While it doesn’t contain anything that’s going to increase your fat burning ability, grapefruit and its juice can prevent certain enzymes from breaking down certain compounds, including several types of cardiovascular disease medication which can lead to toxic levels in the blood. 

S: Or not enough if it's Allegra.

M: Exactly.

S: So definitely speak with your healthcare provider or pharmacist or your registered dietitian to make sure you shouldn’t be avoiding or minimizing your grapefruit intake if you don’t have to. 

M: So that’s it for our discussion on a few food and drug interactions.

S: Thanks for joining us today. We hope you enjoyed the discussion and learned something new. I know I did. Join us next time when we will answer the question: Is red wine healthy?

M: I hope the answer is yes!

S: We’ll see…but I hope so too!

Both: Class Dismissed!

S: We hope you enjoyed this episode. You can find the show notes and a list of sources on our website, yournutritionprofs.com. 

M: Your homework is to follow us at your nutrition profs on Instagram and to listen to our next episode. You can listen on Amazon Prime, Apple Podcasts, Spotify, YouTube, or anywhere podcasts are found. We’d appreciate it if you’d “like” us, write a review, subscribe, and invite your family and friends to join us too. 

S: If you have a nutrition or health question you’d like answered, let us know! We may even do a show about it! Send an email to yournutritionprofs@gmail.com or click on the “Contact Us” page on our website.

M: Thanks to Brian Pittman for creating our artwork. You can find him on instagram @BrianPittman77

Both: See you next time!