The Importance of Phytonutrients for Your Health

Colorful fruit and vegetables

Verywell / Alexandra Shytsman

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Phytonutrients, also known as phytochemicals, are plant-based compounds or chemicals that have a beneficial effect on the body and may play a role in preventing and even treating disease. While it's thought that there are tens of thousands of these phytochemicals, only a small number have been isolated and tested.

Including classes such as carotenoids, flavonoids, isothiocyanates, and much more, these nutrients can have effects that range from antioxidants to anti-inflammatory agents and properties that may be neuroprotective, and provide immune support, regulate hormones, and much more.

Below, you can learn more about phytonutrients, their beneficial effects on prevention and disease, some of the major classes and examples, and then share tips on enriching your diet with these preventive substances.

What Are Phytonutrients?

Phytonutrients are different than vitamins, minerals, and macronutrients such as proteins, carbohydrates, and fats. They are found in fruits and vegetables, many spices, and even edible flowers.

Many of these phytochemicals give the foods their color or smell. Foods containing phytochemicals are often very colorful, but white foods such as onions, garlic, and even olive oil are high in these nutrients.

As far as function, these nutrients can be thought of as part of the plant's "immune system," as they offer protection against viruses, bacteria, fungi, and parasites.

Benefits of Phytonutrients

Phytonutrients play an essential role in maintaining health and preventing disease. Some of the roles played by phytochemicals include:

Fights Oxidative Stress

Some phytochemicals function as antioxidants or "scavengers" in the body. Free radicals are unstable and very reactive molecules produced by toxins (carcinogens) in the environment and normal metabolic processes in the body.

Left unchecked, free radicals can damage DNA and other components of cells. (Oxidative damage to DNA and subsequent mutations are a precursor to cancer and many other conditions.) Antioxidants neutralize these free radicals, preventing the damage they could cause.

Reduces Inflammation

Many phytonutrients can reduce inflammation in the body. While inflammation is the body's natural response to damage, chronic inflammation has been linked with many medical conditions ranging from connective tissue diseases to cancer.

Enhances Immunity

Some phytonutrients support immune system function and can have specific effects. For example, some phytochemicals act as anti-microbial agents, reducing the chance that pathologic (harmful) bacteria or viruses will divide and grow in the body.

Phytonutrients may also help modulate the immune system, helping to maintain the delicate balance between an overactive immune system (that can lead to autoimmune diseases) and an underactive immune system (that can predispose to infections or cancer).

Protects Your Brain

Recent studies have found evidence of neuroprotective effects with some phytonutrients in people who have conditions such as Alzheimer's disease and Parkinson's disease. These include such as epigallocatechin-3-galate, berberin, curcumin, resveratrol, quercetin and limonoids. More research is needed.

Prevents Cancer

In addition to the functions above, some phytochemicals can help in DNA repair (repairing mutated genes that can lead to cancer), slow the growth of tumors, or facilitate apoptosis (the process of cell death that gets rid of abnormal cells).

A 2018 review found that phytochemicals are essential in preventing skin cancers (both melanoma and non-melanoma cancers).

A few of the beneficial nutrients included curcumin (a component of turmeric), proanthocyanidins (found in berries and pistachios), and capsaicin (found in sweet red and chili peppers). In a sense, your diet may be a form of sunscreen.

Some phytonutrients may prevent substances in food or the environment from becoming carcinogens (cancer-causing agents) in the first place.

Reduces Effects of Aging

Several phytochemicals have demonstrated possible anti-aging effects in at least a few clinical trials and various mechanisms. Some of the more common include resveratrol, epicatechin, quercetin, curcumin, and allicin.

Helps Treat Disease

Most research has focused on the ability of phytonutrients to maintain health or prevent disease. Researchers are now trying to determine if phytochemicals may help treat diseases.

These compounds could provide a much less expensive adjunct to treatment with fewer side effects than traditional therapies. While the research is young, early studies have found some phytochemicals that may help fight cancer, such as phloretin in pears and epigallocatechin-3-gallate (EGCG) in green tea quercetin in capers.

These studies are often done in lab-grown cells or animals but, in some cases, conducted on humans. Other foods may help fight heart disease, such as the flavonoids in berries.

Other potential effects are just beginning to be evaluated. For example, scientists are looking at the ability of some phytochemicals to sensitize breast cancer cells to treatment and much more.

Types of Phytonutrients

Phytonutrients can be considered "bioactive food components," as their biological activities in the human body play a role in health. Classification can be confusing, as the major classes are based on chemical structure.

More commonly, these compounds are broken down into phytonutrient groups. The following list is not comprehensive but includes several of the phytonutrients that should be included in a "rainbow diet," as discussed below.


Polyphenols are a category of phytonutrients that includes at least 500 known (and likely many yet to be discovered) compounds. Many of these compounds are antioxidants, and together these nutrients are thought to reduce the risk of many diseases. They are broken down into flavonoids, non-flavonoids, and phenolic acids.


Sometimes referred to as vitamin P, flavonoids are not a vitamin but rather phytonutrients. They have anti-inflammatory properties and may inhibit tumor growth.

Types of Flavonoids

  • Anthocyanidins
  • Quercetin
  • Proanthocyanidins
  • Resveratrol
  • Flavanols
  • Flavanones, such as hesperetin
  • Flavones
  • Isoflavones
  • Catechins

Phenolic Acids

Hydroxybenzoic acids such as gallic acid, ellagic acid, vanillic acid, and hydroxycinnamic acids such as curcumin.

Non-Flavonoid Polyphenols

Non-flavonoid polyphenols include curcuminoids such as curcumin, tannins, stilbenes, such as resveratrol, cinnamic acid, and lignans, such as silymarin.


Terpenoids are broken down into both carotenoid and non-carotenoid phytochemicals. Carotenoids are plant pigments related to vitamin A, but they have antioxidant and immune system effects. Some of these may inhibit tumor growth. They consist of alpha-carotene, beta-carotene, lycopene, lutein, beta-cryptoxanthin, zeaxanthin, and astaxanthin.

Researchers have been studying lycopene for its possible role in reducing the risk of prostate cancer. Lycopene is the highest concentration in cooked tomato products (think: spaghetti sauce, as heating results in better lycopene absorption). Foods high in lutein also include fresh tomatoes, watermelon, and more.

Lutein is found in leafy greens, kiwi, egg yolk, and more; lutein has been linked with a lower risk of macular degeneration (the leading cause of blindness in the United States) and may relieve eye symptoms related to computer use.

Non-carotenoid terpenoids include limonene, carnosol, saponins, phytosteroids, perillyl alcohol, and ursolic acid.


Thiols include several types of phytonutrients with anti-cancer properties and may block carcinogens introduced into the body. They include glucosinolates, allylic sulfides, and indoles.

Glucosinolates include isothiocyanates, such as sulforaphane. Sulforaphane is found in cruciferous vegetables such as broccoli, cabbage, cauliflower, radishes, and more and has powerful antioxidant properties.

Adding Phytonutrients to Your Diet

Adding a healthy variety of phytonutrients to your diet can have many benefits, but many people wonder where to start. After all, it would be cumbersome to stand in the produce section of your market with a list such as that above.

Yet there are relatively simple ways to ensure you get what you need from the currently recommended minimum of five and up to thirteen servings of fruits and vegetables daily. Try to eat a rainbow.

While many of these components are healthy in their own right, it's the optimal combination of nutrients (think: the sounds of an orchestra rather than a single instrument). Various families of plant colors tend to contain similar nutrients; for example, orange foods tend to have the carotenoid group.

Eating a rainbow allows people to get the best phytonutrients as their different colors offer various health benefits. For example, the lycopene in tomatoes and pink grapefruit, the anthocyanins in blue and purple berries, and the chocolate flavonoids are beneficial phytonutrients that function differently.

Here are five of the colors of phytonutrients and some of the functions.


Apples, watermelon, raspberries, beets, cherries, and grapefruit are examples of red foods. They support prostate, urinary tract, and DNA health. Some phytonutrients represented include lycopene, ellagic acid, quercetin, hesperidin, and anthocyanidins. They also may have a protective effect against cancer and heart disease.


Eggplant, grapes, blueberries, and blackberries are purpose foods that are good for your heart, brain, bone, arteries, and cognitive health. Phytonutrients include resveratrol, anthocyanins, phenolics, and flavonoids.


Kiwi, avocado, cantaloupe, broccoli, and spinach are excellent green foods. These foods support eye health, arterial function, liver function, and cell health. Some phytochemicals found in green foods include epicatechins, isothiocyanate, lutein, zeaxanthin, isoflavones, flavonoids, and coumestans.


Onions, mushrooms, and pears are white foods that support healthy bones and circulatory systems and may help reduce the risk of or fight heart disease and cancer. Phytochemicals in these foods include allicin, quercetin, indoles, and glucosinolates.

Yellow and Orange

Pumpkin, carrots, peaches, pineapple, and papaya are yellow and orange foods that promote healthy growth and development and good eye health. Phytochemicals common in yellow and orange foods include alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin, and hesperidin.

Many spices and even flowers can add flavor and a healthy dose of phytonutrients to your diet with few calories. Examples of phytonutrients in spices include luteolin (found in oregano, sage, thyme, and celery seed) and apigenin, found in parsley.

Strategies for Eating Healthy Phytonutrients

  • Keep a chart on the refrigerator that reminds you and your children of the "colors" you have eaten and those you still need to eat each day.
  • Become creative when preparing foods. Salads can be "doctored" to include various colors and hence phytochemicals. Add berries, veggies, avocados, chia seeds, and more.
  • Try "hiding" a serving or two of veggies in your main dishes. Foods such as cauliflower are easily hidden in spaghetti sauces, chili, and soups.
  • Skip the spaghetti noodles and try zucchini or spaghetti squash "noodles."

Phytonutrient Cautions

A diet higher in phytochemicals, especially various compounds, can mean better health. But it's important to remember that too much good food is not necessarily better. An excess of one "good" food may lead to a deficiency of phytonutrients.

Are Organic Foods Better?

While the science is young, maximizing your intake of phytonutrients may be one reason to choose organic foods when possible.

An example is the 2017 study published in the Journal of Agricultural and Food Chemistry. This study found that onions grown under organic conditions had more significant antioxidant activity and greater concentration of flavonols and quercetin.

We won't know the whole story for some time, but this thought may help justify some of the increased costs for those who try to choose organic foods.

For Those Who Have Thyroid Disease (Goitrogens)

For those who have thyroid disease or are at risk for thyroid disease, it's important to point out that many of the healthiest foods concerning phytochemical content also contain goitrogens, which have an anti-thyroid effect.

Foods (such as broccoli rich in sulforaphane) that are goitrogens can still be eaten but should be spaced out throughout the day. Eating some of these foods steamed rather than raw can reduce the goitrogen content.

Dietary vs. Supplemental Phytonutrients

In contrast, some supplements may have the opposite effect. A classic example occurred with the risk of lung cancer.

Upon noting that people who ate foods high in beta-carotene had a significantly lower risk of developing lung cancer, researchers set out to see if beta-carotene supplements would have the same effect. Not only did the supplement form of beta-carotene not reduce risk, but people who used beta-carotene supplements had a significantly higher risk of developing the disease.

Despite the multitude of studies that have found a diet rich in fruits and vegetables to be beneficial in overall health, we have yet to obtain the same benefits from supplements of the phytonutrients contained therein.

A Word From Verywell

Phytonutrients or phytochemicals play an essential role in maintaining health and preventing disease. Rather than focusing on specific phytonutrients, however, the most significant health benefits likely come from eating a wide variety of these nutrients.

After all, many of the benefits we receive from eating a wide variety of colorful fruits and vegetables may come from phytonutrients that are yet to be discovered.

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Additional Reading

By Laura Dolson
Laura Dolson is a health and food writer who develops low-carb and gluten-free recipes for home cooks.