Health

Heart Health and Leafy Greens: What’s Nitrate Got to do With It?

Dark leafy greens and cruciferous vegetables are often given the title of “superfoods,” and for good reason! While they provide many different health benefits, we are going to focus on the specific role that they play in heart health. You might have heard this advice before, but it can often feel abstract, so we want to break it down in a way that makes sense and give you some ideas to help you add more greens to your diet. While these vegetables are loaded with all sorts of beneficial nutrients such as fiber, protein, vitamins, minerals, and phytochemicals, one key nutrient they contain is nitrate. Let’s talk about how nitrate from these food sources can lead to heart health.

Blood vessels are the highways that blood travels from your heart to all parts of the body and then back again. When we measure blood pressure, this looks at the pressure that is being exerted against those blood vessels and can be an indicator for chronic diseases such as cardiovascular disease and type 2 diabetes. One important compound when it comes to blood vessel health is called nitric oxide. Nitric oxide works as a vasodilator which means that it helps the blood vessels to widen or dilate, causing blood pressure to decrease. It also works in keeping the smooth muscle of the blood vessels healthy, which is important in the prevention of atherosclerosis, or the buildup of plaque. But to get to nitric oxide, there are a few steps that need to happen beforehand in a process called the nitrate-nitrite-nitric oxide pathway. Let’s break this down. 

Nitrate is a nitrogen-containing compound that is mainly found naturally in green leafy vegetables, cruciferous vegetables and meat products as an added preservative. 

Nitrate is then converted to nitrite by bacteria in our mouth and stomach, which is then converted to nitric oxide, once inside our tissues and blood. This is the magic compound that helps to keep our blood vessels healthy and leads to heart health.

Because of the relationship between nitric oxide and blood pressure, there are indications for the role of nitrates in heart health. If blood pressure is too high, the heart has to work harder to pump blood throughout the body. This is a problem because the high pressure can cause the blood vessels to weaken, which can decrease the flow of blood to the heart. Because of this, we should aim to keep our blood pressure within normal limits, and one of the best ways to do this is to consume foods that contain nitrate, as it will eventually be converted to nitric oxide and help decrease blood pressure. Check out this chart from the American Heart Association to see a breakdown of blood pressure levels. 

You may have heard some confusing information around the topic of nitrates. However, this is only in the context of meat products. Both plant and animal sources contain nitrates and nitrites. Research has suggested that nitrates added to processed meats is associated with increased disease risk, such as various types of cancer. Conversely, research has also shown that nitrates found in fruits and vegetables are associated with a decrease in disease risk. How can this be? How is it possible that the same compound can be good for our heart coming from one food source, and wreak havoc and cause disease when coming from another food source? 

The secret lies within the other nutrients found in the food. Think of a food item as a package: a handful of spinach or a slice of deli meat doesn’t just contain 1 nutrient. Rather it is a package of nutrients. A serving of spinach is “packaged” with nitrate and also fiber, protein, vitamins, minerals, and phytochemicals. Deli meat, on the other hand, comes “packaged” with protein, saturated fat, cholesterol, hormones, heme iron, chemicals, and other compounds that can be dangerous. It is when the nitrates and nitrites react with these other compounds found within meat that they form cancer-causing molecules that increase the risk of disease. 

When you look at the nutrients that come in plant foods, such as vitamin C, vitamin E, and polyphenols, these actually inhibit certain reactions between nitrate and other molecules. Therefore, it is important to consume nitrates in the form of whole plant foods for their heart health benefits, as they are packaged with other nutrients that will help to inhibit the formation of disease-causing compounds. 

Green leafy vegetables are the greatest contributor of nitrate to the diet, such as lettuce, kale, spinach, chard, arugula, cabbage, and dill. Cruciferous vegetables such as kale and broccoli are also good sources. But most fruits and vegetables, in general, contain small amounts. For even more sources of nitrate, check out Dr. Michael Greger’s article. 

To get a good amount of nitrate in your diet, it’s important to eat a few servings of these vegetables. 

• Aim to eat 2 servings of leafy greens. 1 cup of raw vegetables counts as 1 serving. 
• Aim to eat 1 serving of cruciferous veggies. ½ cup of cooked vegetables counts as 1 serving. 

• Eat a big salad for lunch with a variety of greens such as romaine lettuce, spinach, and arugula. 
• Try eating roasted veggies like kale and broccoli for dinner. This is also great for leftovers the next day as a cold salad!
• Layer sandwiches with lots of lettuce to add that irresistible crunch. 
• Freeze spinach or collard greens to add into smoothies, which is a super sneaky way to get more greens!

Karwowska, M., & Kononiuk, A. (2020). Nitrates/Nitrites in Food-Risk for Nitrosative Stress and Benefits. Antioxidants (Basel, Switzerland), 9(3), 241. https://doi.org/10.3390/antiox9030241

By Ryan Herring, MD, MPH Dr. Ryan Herring utilizes a whole person approach in primary care to restore health and optimize wellbeing. He is originally from Central Illinois where he attended college and medical school at the University of Illinois. He completed residency training in Preventive Medicine at Loma Linda University.