Thinking Nutrition

Want a healthy heart? Eat more of these flavonoid foods

March 08, 2022 Dr Tim Crowe Episode 94
Thinking Nutrition
Want a healthy heart? Eat more of these flavonoid foods
Show Notes Transcript

Heard about flavonoids? They are just one group from a long list of beneficial natural polyphenol chemicals you’ll find in plant foods. While the chemistry and naming structure can be daunting, there is nothing daunting about the foods that contain lots of these flavonoids. In our body, these flavonoids can operate as antioxidant and anti-inflammatory agents. And that all spells good news for your heart health. In this podcast, I’ll explain what flavonoids are, what foods contain lots of them, and unveil the latest evidence linking them to good heart health.

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Heard about flavonoids? They are just one group from a long list of beneficial natural polyphenol chemicals you’ll find in plant foods. While the chemistry and naming structure can be daunting, there is nothing daunting about the foods that contain lots of these flavonoids. In our body, these flavonoids can operate as antioxidant and anti-inflammatory agents. And that all spells good news for your heart health. In this podcast, I’ll explain what flavonoids are, what foods contain lots of them, and unveil the latest evidence linking them to good heart health.

Here’s some shocking news: fruits and vegetables are good for you. I know, crazy, right? But why are they so good for you? The list is long and includes the multitude of nutrients they contain and also all the fibre, a lot of it prebiotic fibre which is A-grade fuel for your gut microbiome. And then there is a class of chemicals called polyphenols.

Talking about polyphenols is akin to opening up Pandora’s box. That’s because there are thousands, of different types. And you find them in fruits, vegetables, wholegrains, legumes, herbs and spices, tea and even coffee. And the key theme is that they’re all plant foods which is why they are also referred to as phytochemicals.

A brief reading about polyphenols on the Internet will bring up article after article highlighting that polyphenols are antioxidants and that explains their health benefits. Nutrition science though has well-and-truly moved on from using such simplistic language and concepts to describe how these thousands of polyphenols found in food work. They are much more than antioxidants. Focusing only on antioxidants or a single phytonutrient is like zeroing in on a section of a painting and seeing only the dots. You need to step back and see the bigger picture. It should instead be about polyphenols and their multitude of benefits and actions in the body such as:

  • regulating cell growth and death
  • slowing down cancer cell proliferation
  • altering glucose responses and insulin sensitivity
  • increasing activity of enzymes involved in removing harmful substances from the body
  • and decreasing inflammation


One branch of the very big polyphenol family is a group of chemicals called flavonoids. These flavonoids can be categorised further into other chemical classes. Welcome to the polyphenol rabbit hole. I’ll just quickly go over some of the names of these flavonoid chemicals as you may have heard of some of them in passing, but if not, don’t worry, there is no chemistry exam at the end of this podcast.  

So, here are the flavonoid groups: flavonols, flavones, flavan-3-ols, anthocyanins, flavanones, and isoflavones. Grab the transcript of this episode if you want to see the subtle differences in the spelling of some of these groups.

But back to food because that’s the ‘carrier’ of all these chemicals. And here are some of the top foods that contain lots of some of these flavonoids: berries, red cabbage, onions, kale, soy, parsley, tea, citrus fruits, grapes and dark chocolate.

And if you want a nice article that goes over the different flavonoid classes and the main foods in them in a little more detail, then I’ll link to a Healthline article on it in the show notes. https://www.healthline.com/health/what-are-flavonoids-everything-you-need-to-know 

In fact, I’ve already gone into depth on one of these flavonoid groups called the anthocyanins – these are what are responsible for putting the ‘blue’ into blueberries and a bunch of other berries as well as some foods with bright red-orange colouration. So, check out podcast episode 81 on anthocyanins for more detail on what they can do for your brain and overall health.

But back to the broader flavonoids. Having lots of these in your diet has been linked to a positive influence on the risk of a range of diseases such as cardiovascular disease, cancer and even brain decline with ageing.

Just looking at heart disease, it is already known that diets high in flavonoids are associated with a lower risk. But not all flavonoids, and the foods that contain them, are equal. So, could there be some clues in the research as to which ones may be better to focus on for someone at higher risk of heart disease?

That was the question posed in a recent systematic review and meta-analysis. All up, 19 prospective observational studies were included that looked at the association between various flavonoid subclasses and the risk of coronary heart disease events like heart attacks and death. And I’ll link to the study in the show notes. https://pubmed.ncbi.nlm.nih.gov/34470681

Here’s the summary of the results. Comparing people who had the least amount of a flavonoid class to those having the most, it was the anthocyanins and proanthocyanidins (these are your berries) that saw a lower heart disease risk of 10 and 22 percent respectively. 

For flavonols (things like kale and onions) it was a 12 percent lower risk. And for isoflavones (which you’ll find in soy) a 10 percent lower risk was seen. For the other classes of flavonoids, there wasn’t much of a significant benefit seen.

Eighteen of the 19 studies were considered to be of high quality. That gives some confidence in the findings. And to add to this, there are some very plausible mechanisms to explain the benefits into how flavonoids can reduce the risk of coronary heart disease. And these include dilating blood vessels, enhancing the antioxidant defence system and reducing inflammation.

Now, all of this research was observational, so none of it can prove that it was the flavonoids that were responsible for the benefit on coronary heart disease. But there are lots of clinical trials using them as supplements that did show improvements in risk factors for heart disease such as blood pressure, fasting glucose, inflammation and blood lipids. So, that all points in the right direction that these chemicals are having a real physiologic effect. And because they exist in a complex food matrix, there will likely be additional compounding benefits from other nutrients in the food.

Which is kinda just another way of saying after all this detailed science to: eat lots of plant foods, and not too processed as you’ll lose some of these beneficial flavonoids. And it is berries, onions, kale, soy and dark chocolate for the win here for your heart health.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.