Understanding the Health Benefits of Quercetin

When it comes to staying healthy and feeling your best, the impact of polyphenols has long been ignored. In 2024, I was co-author of a review article on the potential health benefits of these compounds. One of these beneficial compounds is quercetin. Found in everyday foods like apples, onions and berries, this plant-based polyphenol is packed with powerful benefits for our gut microbes and our own health. Let’s break it down in a way that makes sense and see which ways you can bring more of into your diet.

“What Is Quercetin?”

Quercetin is a polyphenol—a large complex molecule naturally found in plants that helps protect them from environmental stress, such as UV light, drought, diseases and pests. The more a plant is exposed to such stressors, the more polyphenols it produces in its leaves and fruits. Surprisingly, for us humans, it does something very similar. When evaluated in the test tube, it functions like an antioxidant, fighting off harmful molecules, which can damage our cells and lead to aging, neurodegeneration and disease. However, beyond its antioxidant activity, quercetin plays a significant role in gut health. In the gut, quercetin feeds certain gut microbes, and the breakdown products generated by the microbiome enhance digestion, the immune response, cardiovascular health and even brain health.

You can find quercetin in foods like apples (especially the skin), onions, green tea, red wine, and berries. It’s not just about eating these foods…quercetin is what gives them many of their health-promoting benefits.

“The Science-Backed Benefits of Quercetin”

Here’s what makes quercetin worth talking about:

1. Quercetin, like all polyphenols is an antioxidant which fights oxidative stress by neutralizing free radicals. Most importantly it can modulate your gut microbiome to increase the production of health promoting short-chain fatty acids, like butyrate. This protects your cells from damage, keeps you feeling younger and reducing your risk of chronic diseases. As discussed in our review article’s findings, quercetin can also indirectly influence brain health by improving vascular function and reducing inflammation.
2. One of the coolest things about quercetin is its interaction with gut microbes. As discussed in detail in our review, research, polyphenols, including quercetin, are metabolized by gut bacteria into smaller, bioactive and absorbable compounds. These metabolites enhance the diversity of the gut microbiota and contain short-chain fatty acids, which are key for gut and brain health.
3. Chronic inflammation can lead to conditions like arthritis, heart disease and neurodegeneration. Our review discusses how quercetin supplementation can lower inflammatory markers like TNF-α and interleukin. This anti-inflammatory effect also shows promise for supporting treatments for neuroinflammatory, neurodegenerative diseases and cardiovascular diseases.
4. Quercetin’s impact on cardiovascular health is significant. In clinical trials, daily supplementation with 150 mg of quercetin for six weeks lowered blood pressure in participants at risk of cardiovascular disease, reducing systolic blood pressure by 2.9 mmHg in hypertensive individuals and by 3.7 mmHg in younger adults aged 25 to 50.
5. Quercetin helps regulate immune responses and has been shown to even shorten the duration of colds and other viral infections. It has also been shown to modulate immune pathways, contributing to better overall resilience.
6. Emerging evidence links quercetin to neuroprotection. Microbial, quercetin-derived metabolites can reduce neuroinflammation and improve synaptic plasticity. In a 24-week study, participants aged 60 to 79 who took 50 mg of quercetin daily experienced reduced age-related cognitive decline, potentially due to improvements in mood and motivation.
7. Gut microbiota-generated metabolites from polyphenols like quercetin have been shown to influence brain health. The interaction between quercetin and gut bacteria supports improved gut barrier integrity, reduces systemic inflammation, and enhances brain function by promoting beneficial microbial populations.

“Incorporating Quercetin into Your Diet”

Getting quercetin into your daily routine is easier than you think. Here are some of the best sources:

• Fruits: Apples (don’t peel them!), berries, and citrus fruits.
• Vegetables: Onions (red and yellow), kale, broccoli, and spinach.
• Beverages: Green tea, black tea, and red wine.
• Herbs: Dill, cilantro, and capers.

To really get the most out of the health benefits of polyphenols, aim for a colorful, plant-based diet with plenty of variety. If you’re considering supplements, talk to your doctor first—especially if you’re on medication or have health concerns.

Many people claim that consuming a diet rich in quercetin may not be enough, as bioavailability is low. However, this is simply because less than 5% are absorbed intact in the proximal part of the small intestine. 95% needs to be broken down by your gut microbes into absorbable smaller components. After human consumption, the antioxidant effects of polyphenols make up only a very small percentage of their overall health benefits. The main benefit comes from the fact that our gut microbes “eat” these metabolites and increase the production of beneficial short-chain fatty acids and other metabolites, which exert their beneficial effect not only in the gut but throughout our body, including the brain.

If you follow a type of diet that eliminates quercetin-rich foods, or simply don’t want to eat these food items, you may consider increasing your quercetin intake by using a high quality supplement. We are in the process of creating a carefully selected group of supplements to optimize your diet & gut microbiome. You can sign up for updates at www.mayernutrition.com and follow us on Instagram @mayernutrition – we are launching in the second half of 2025.

“Future of Polyphenols”

I have noticed hype building around some polyphenols, quercetin included. Polyphenols have become one of my favorite topics to talk about, and their potential for cognitive health is particularly exciting, as studies suggest that polyphenol-derived metabolites may play a role in delaying neurodegenerative diseases and improving mental resilience.

Quercetin is more than just a buzzword – it’s a compound your gut (and brain) loves. Whether you want to fight off inflammation, protect your brain from neurodegeneration or keep your gut happy, quercetin is worth prioritizing in your diet. Start with whole foods, get creative with your meals, and see how this powerful polyphenol can make a difference in your health.