August 15, 2023

Foods Rich in Polyphenols — and Why They’re Important

Polyphenols come from natural foods with vibrant colors, like berries and turmeric

Two bento boxed filled with colorful stawberries, blueberris, cherries, nuts and wheat crackers.

Some of the best nutrition advice out there is to “eat the rainbow.” As in, eat a variety of natural, colorful foods.

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Red strawberries, purple plums, green … greens. You get the picture.

That’s because the vibrancy of the blue in your blueberries is a sign they’re packed with chemical compounds called polyphenols, which are rich in antioxidant and anti-inflammatory properties.

We talked with registered dietitian Devon Peart, RD, MHSc, about the importance of polyphenols in a healthy diet — what do they do for you? And how can you spot polyphenol-rich food?

What are polyphenols?

Polyphenols are nutrients in plants and plant-based foods that help your body manage inflammation and protect you from oxidative stress.

Peart explains, “Polyphenols are simply a category of phytonutrients, which are chemical compounds in plants that provide specific health benefits. Along with other nutrients in plants, like fiber, vitamins and minerals, polyphenols can help protect your body from the root causes of many chronic illnesses.”

Benefits of polyphenols

Polyphenols help keep plants healthy. They make sure the plant can absorb the sunlight it needs to grow, and they protect the plant from disease.

When you eat polyphenol-rich plants, those same polyphenols that kept the plant healthy do similar good for your body. Polyphenols have two main benefits for your body: They’re antioxidants and anti-inflammatory.

As an antioxidant, polyphenols help fight free radicals (unstable molecules) in your body. That’s important because a buildup of free radicals damages your cells. That damage is called oxidative stress, and it can lead to a range of health conditions, like:

  • Cancer.
  • Autoimmune disease
  • Heart disease.
  • Aging skin.

Polyphenols are also anti-inflammatory. Anyone who’s ever stubbed their toe knows a bit about inflammation — that’s the swelling and pain that signals your body going into “repair mode.” But inflammation can happen even when you’re not sick or injured. When your body sends out inflammatory cells when they’re not needed, it can lead to chronic conditions, like arthritis and Alzheimer’s disease. A diet rich in polyphenols can help keep your inflammation response in check.

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Four types of polyphenols

There are more than 1,000 kinds of polyphenols. They fall into four main categories:

  1. Phenolic acids.
  2. Flavonoids.
  3. Stilbenes.
  4. Lignans.

Those categories are broken down into subcategories. And those subcategories are broken down into subclasses … and so on. Those classifications are based on specific differences in chemical makeup, like how many rings they have, and the molecules attached to each ring.

Sparing you the lessons in organic chemistry, all those various kinds of polyphenols essentially do the same thing: They help defend your body from chronic disease.

Polyphenols and food

Polyphenols occur naturally in plants. So, just about any time you eat fruits, vegetables, herbs, spices, seeds, nuts and whole grains, you can feel confident you’re doing good for your body. The key is to eat a wide range of natural foods to get a mix of as many polyphenols (and other nutrients) as possible.

“There’s so much nutritional value in all plant foods,” Peart says. “To get the benefits of the broad array of micronutrients, you need to eat a variety.”

A list of the best foods for polyphenolic content could literally read like an encyclopedia of the plant kingdom. They’re that widespread. But a short list of polyphenol-rich foods includes things like:

  • Apples.
  • Berries.
  • Broccoli.
  • Carrots.
  • Chili peppers.
  • Cumin.
  • Dark chocolate (because cocoa is a major source of polyphenols).
  • Flax seeds.
  • Ginger.
  • Gingko biloba.
  • Green tea.
  • Oats.
  • Olives and olive oil.
  • Onions.
  • Red cabbage.
  • Sesame seeds.
  • Spinach.
  • Turmeric.
  • Whole grains.

But rather than committing a list to memory, there’s an easy shortcut for estimating a food’s polyphenolic content, Peart says. “Look for natural plant foods with vibrant colors. When it comes to fruit, generally speaking, the darker the fruit, the greater the polyphenol content. And eating the skins and or seeds where appropriate, gets you more of the polyphenols.”

Polyphenols also affect foods’ flavors (often bitter/astringent) and odors. For example, iceberg lettuce will have a lower polyphenolic content than dark leafy greens, like spinach or kale.

Freshness matters

Peart adds that the polyphenolic content of any particular food can vary. That’s because polyphenols can be affected by things like air exposure, water conditions, soil conditions, and the age and stage of the plant itself.

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Remember, polyphenols help keep plants healthy, so the healthier the plant, the more benefits you’ll reap from eating that plant. That also means fruits or vegetables lose some of their polyphenolic content over time, as they’re transported to your local grocery store or as they sit in your fruit bowl waiting to be eaten, for example.

So, in-season, local produce is going to be your best bet whenever possible.

Now, that’s not always going to work as easily as you’d hope. For instance, if you live in Canada, getting your hands on a case of Canada-grown berries in January can be a tough find. And if they’re imported, those berries will lose some of their nutrients on the journey to your home.

“It’s always preferable to buy local produce that’s in-season when you can. That’s your best bet for getting the highest nutritional value,” Peart reiterates. “But in some places and at some times of the year, those options may be quite limited. So, to get a good variety of nutrient-rich foods, I recommend mixing in some frozen produce. Fruits and vegetables are frozen at peak ripeness, so sometimes they can be more nutritious than fresh if the fresh produce has traveled far or has been sitting in the store waiting for you to buy it.”

Polyphenols as supplements

If you’re concerned you’re not getting a variety of healthy plant foods in your diet, you’re probably thinking, “That’s OK. I bet there’s a supplement for that!

On one hand, that’s true. There is a supplement for just about any nutrient you need (or think you need.) But, Peart cautions, polyphenol supplements aren’t likely to give you the health benefits you’re looking for.

“When you isolate nutrients from foods and manufacture them into supplements, some aspects of the whole food may get lost in translation, so to speak,” she explains. “Polyphenols, like other nutrients in foods, are likely activated or made more powerful by working in harmony with other compounds in the food. So you’re almost always going to get better nutrition from food than from supplements.”

Instead, enjoy your polyphenols straight from the source. Your body (and your taste buds!) will thank you for it.

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