Polyphenols are natural compounds found abundantly in plants, contributing to their vibrant colors and unique flavors. These compounds play a protective role for plants, shielding them from environmental stressors like UV radiation and pathogens. When consumed by humans, polyphenols continue to exert various beneficial effects within the body.
Classes of Polyphenols and Their Food Sources
Flavonoids
Flavonoids are the largest and most diverse group of polyphenols, with over 6,000 compounds. They are widely distributed in plant-based foods, contributing to their colors. Rich sources include berries, dark chocolate, onions, kale, and various teas.
Phenolic Acids
Phenolic acids are another significant class of polyphenols, found in many plant-derived foods. This group includes hydroxybenzoic and hydroxycinnamic acids. Sources include coffee, black and green tea, cherries, apples, and whole grains.
Stilbenes
Stilbenes are a smaller group of polyphenols, with resveratrol being the most known. Resveratrol is notably present in red grape skin and red wine. Other sources include peanuts and some berries.
Lignans
Lignans are polyphenols often converted by gut bacteria into hormone-like compounds. They are concentrated in seeds and whole grains. Flax seeds are a rich source, with amounts also found in sesame seeds, rye, and barley.
How Polyphenols Work in the Body
Polyphenols function primarily as antioxidants, neutralizing unstable molecules called free radicals. Free radicals are byproducts of normal bodily processes and environmental exposures, and their accumulation can lead to cellular damage. Polyphenols donate electrons to these free radicals, stabilizing them and reducing potential harm.
Beyond this, polyphenols also exhibit anti-inflammatory properties. They can modulate signaling pathways involved in inflammation, helping to reduce the body’s inflammatory responses.
The Role of Gut Bacteria in Polyphenol Activity
Many polyphenols are not directly absorbed in the small intestine due to their complex structures. Instead, a portion travels to the large intestine, where gut microbiota metabolize them into smaller, more bioavailable compounds.
This interaction is symbiotic: polyphenols act as prebiotics, nourishing beneficial gut bacteria. In return, bacteria break down polyphenols into metabolites that are more readily absorbed. These microbial-derived compounds often possess enhanced biological activity, contributing to polyphenol health effects.
Practical Ways to Increase Polyphenol Intake
Incorporating a wider variety of plant-based foods into your diet is an effective strategy to boost polyphenol intake. Aim to “eat the rainbow” by selecting fruits and vegetables across a spectrum of colors, as different pigments often indicate the presence of various polyphenol classes. Prioritizing whole fruits over juices helps retain beneficial fibers and concentrated polyphenol content.
Leaving the skin on fruits and vegetables, such as apples, potatoes, and cucumbers, whenever appropriate, can also increase polyphenol consumption, as many of these compounds are concentrated in the outer layers. Generously using a variety of herbs and spices in your cooking, like oregano, thyme, rosemary, and turmeric, adds a significant amount of polyphenols. Choosing whole grains like oats, quinoa, and brown rice instead of refined grains further enhances your dietary polyphenol profile.