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Published: June 8, 2024

What Are Phytonutrients? A Handy Guide to Eating the Rainbow

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Despite the hype, not all chemicals are bad for you. Plants contain thousands of natural chemicals called phytonutrients or phytochemicals, which help protect plants from germs, fungi, bugs, and other threats. The name comes from the Greek word phyto, meaning “plant.” Aside from produce, other plant-based foods – such as whole grains, nuts, beans, spices, and tea leaves – also contain phytonutrients.

Phytochemicals have antioxidant-like properties, but phytochemicals and antioxidants aren’t the same . The main purpose of antioxidants is to prevent free radicals from harming cells (fight cell oxidation), while phytochemicals have a wide variety of health benefits. Antioxidants can also be found in animal-based foods, where phytonutrients are found only in plants.

What Are the Benefits of Phytonutrients?

Unlike vitamins and minerals, phytonutrients aren’t necessary for keeping us alive. But just because they aren’t essential doesn’t mean they don’t offer lots of health benefits. Research has shown that people who follow plant-based diets (which are high in phytonutrients) have lower blood pressure; lower risk of heart disease, cancer, and stroke; fewer instances of type 2 diabetes; improved cholesterol; and longer life expectancy.

Fighting oxidative stress

Some phytonutrients have antioxidant properties and can work to neutralize free radicals in the body. Free radicals are reactive molecules produced both by toxins in the environment and through normal bodily processes. When left unchecked, free radicals can damage DNA. Oxidative stress damage is often a precursor to cancer and other health conditions.

Improved immune function

Phytonutrients work to regulate the immune system, helping to maintain the delicate balance between an underactive immune system (which can lead to infections) and an overactive immune system (which can promote autoimmune diseases). They also can act as antimicrobial agents, reducing the chances of harmful bacteria or viruses taking hold.

Reduced inflammation

Inflammation is the body’s response to damage and illness, but chronic inflammation can lead to a host of medical conditions. Cancer, asthma, arthritis, diabetes, even mental illness all have ties to increased inflammation levels in the body. It’s thought that phytonutrients activate anti-inflammatory genes and suppress pro-inflammatory genes.

Maintaining health and preventing disease

Much of the research around phytochemicals is focused on their ability to maintain health and prevent disease. Though only a few comprehensive studies have been done, they’ve found that phytonutrients may help fight cancer and prevent heart disease.

What Are the Different Types of Phytonutrients?

There are more than 25,000 phytonutrients found in plant foods, and many of these chemicals are what give plants their pigmentation and flavor. Phytonutrients are split into classes, which include:

  • Betalains
  • Chlorophyll
  • Indoles
  • Organosulfides
  • Phenols
  • Terpenes
  • Triterpenes

Within these classes, they’re further separated into dozens of groups, each containing hundreds of phytonutrients. We’ll explore the health benefits of five phytonutrient groups below.

1. Carotenoids

Carotenoids are the phytochemicals responsible for the bright colors of fruits and vegetables. While there are more than 600 carotenoids, some common types include beta-carotene, lutein, and lycopene. They act as antioxidants, and some, like beta-carotene, can be converted into vitamin A. These phytochemicals support eye health and immune function, and they may reduce your risk of developing certain cancers. Foods rich in carotenoids include:

  • Carrots
  • Oranges
  • Pumpkins
  • Spinach
  • Tomatoes
  • Yams

How to Eat: Roasted Rainbow Carrots

2. Curcuminoids

Curcuminoids are polyphenols found in turmeric. One such curcuminoid is curcumin, which has long been recognized for its medicinal properties. Curcuminoids help prevent oxidative stress and can lower inflammation levels in the body. These phytonutrients have also been shown to treat muscle soreness and enhance athletic performance.

How to Eat: Creamy Turmeric, Ginger, and Coconut Oats

3. Ellagic acid

Ellagic acid has antioxidants properties and has shown to lower cholesterol. It also has cancer-fighting abilities, both slowing the growth of cancer cells and assisting the liver in neutralizing cancer-causing chemicals. Foods rich in ellagic acid include:

  • Pomegranates
  • Raspberries
  • Strawberries

How to Eat: Fig and Strawberry Raw Bites

4. Flavonoids

Flavonoids are one of the largest groups of phytochemicals, with some common types including flavones, anthocyanins, isoflavones, and flavanols. Rich in antioxidants, flavonoids help lower blood pressure by relaxing blood vessels and promoting good circulation and can improve blood flow to the brain. Foods rich in flavonoids include:

  • Apples
  • Ginger
  • Green tea
  • Legumes
  • Onions

How to Eat: French Onion Chicken

5. Resveratrol

Another type of polyphenol, resveratrol is most commonly found in grape skins and (by extension) wine. The compound supports cardiovascular health and brain function and is the reason that red wine has been found to be good for your heart. According to the Mayo Clinic, resveratrol may “help prevent damage to blood vessels, reduce LDL cholesterol (the ‘bad’ cholesterol) and prevent blood clots.” Foods rich in resveratrol include:

  • Blueberries
  • Dark chocolate
  • Grapes and grape skins
  • Peanuts
  • Pistachios

How to Eat: Grape and Almond Butter Oatmeal

6. Glucosinolates

Glucosinolates are compounds found predominantly in cruciferous vegetables. These compounds have been shown to regulate inflammation and stress responses and have been associated with cancer prevention. Some animal studies have found that glucosinolates deactivate carcinogens and prevent cell oxidation. Foods rich in glucosinolates include:

  • Bok choy
  • Broccoli
  • Brussels sprouts
  • Cabbage
  • Cauliflower

How to Eat: Shaved Brussels Sprouts Salad

How to Incorporate Phytonutrients into Your Diet

Adding phytonutrients into your diet is easier than it may seem. Because so many phytonutrients dictate the color of fruits and vegetables, registered dietitian and IIN grad Sheri Vettel recommends eating the rainbow. “When I think about boosting phytonutrients in my eating approach, I always come back to color! Aiming to eat a variety of plant-based foods from all colors of the rainbow – on a regular basis – ensures that you're getting a good mix of these beneficial compounds.”

A member of the visiting faculty at IIN, health educator, researcher, and author Deanna Minich, PhD, is a strong proponent of eating the rainbow. To encourage the public to obtain the benefits of plant-based foods and phytonutrients, Dr. Minich suggests following an “eat by color” approach. “Although each individual food may have numerous effects...the goal of this simplified approach [is] to identify general patterns of benefits.” By grouping together phytonutrient-containing foods according to color, people may have an easier time recognizing these foods and incorporating them into their diet.

You can gain some benefit from phytochemical supplements, but it’s likely the interaction between these compounds and the vitamins, minerals, fiber, and essential fatty acids found in whole foods that’s responsible for their many health benefits.

The Bottom Line

Increasing your intake of phytonutrient-rich foods can support your immune system, lower cholesterol levels, and even prevent cancer. And it’s important to choose organic foods when possible: A 2017 study found that produce “grown under organic conditions had more significant antioxidant activity and greater concentration of flavanols and quercetin.”

If you’re looking to incorporate more of these phytochemicals into your diet but don’t know where to start, Health Coaches can help! IIN’s online Health Coach Training Program covers a variety of subjects in nutrition and nutrition science plus lifestyle and functional medicine. IIN takes an integrative and holistic approach to wellness, embracing and teaching the concept of integrative nutrition.


The Original Health Coaching Program

Learn more about IIN’s rigorous curriculum that integrates 90+ of the world’s leading experts in health and wellness, blending the scientific and the spiritual to create an immersive, holistic health education.

The Health Coach Training Program Guide