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How Eating a Rainbow Protects Your Health

What Are Phytonutrients?

Phytonutrients, also called phytochemicals, are natural chemical compounds found in plants (‘phyto’ is a Greek word meaning ‘plant’). Phytonutrients are the substances that give plants their smells, colors, and flavors.  These compounds also provide protection against disease and are beneficial to human health in a variety of ways as we’ll discuss in this article.

If you’ve never heard of phytonutrients before, it may be because nutrition science is such a young field and phytonutrients are the newest nutrients on the block. Scientists have only known what vitamins are for just over a hundred years. Phytonutrients were discovered after that, and most of the discoveries and research on these plant compounds has occurred during the last couple decades. According to WebMD more than 25,000 phytonutrients have been identified to date and more are being discovered every year.  With such a large number of nutrients in any given fruit or vegetable, it is becoming harder to credit a single nutrient for health benefits. Dr. Doug Graham, nutrition expert and author of the diet book 80-10-10, writes:

“I have heard estimates that scientists today may have discovered only 10% of the nutrients in existence, particularly the so-called phytonutrients (plant nutrients). In light of this, we might stop for a moment to wonder. How can any of us claim to have zeroed in on some specific nutrient deficiency and take informed action toward correcting it? It cannot be done intelligently, in my opinion.”

Instead Dr. Graham and other leading nutrition experts are recommending people center their diet around whole plant foods from all the colors of the rainbow.

Eating a rainbow of whole plants gives you a full spectrum of phytonutrients.

Eating a rainbow of whole plants gives you a full spectrum of phytonutrients.

Phytonutrients Are in the Rainbow

There is a good reason why today’s nutrition experts are increasingly recommending that people eat the rainbow, rather than focus on counting calories or restricting a certain macronutrient. Eating foods from all the color groups ensure you are getting a variety of phytonutrients in addition to essential nutrients like fat, protein, carbohydrates, vitamins, and minerals. Phytonutrients are most concentrated in the colorful parts of foods, which allows us to link food color groups to certain health benefits they provide.  Many fruits have their highest concentration of pigment, and thus their highest phytonutrient content, in their peels. This makes sense because the role of phytochemicals in a plant is to provide protection to the plant. When we eat these microscopic phytonutrients, some of the protection benefit is passed onto us. While it can be difficult to isolate one compound–or a single phytonutrient–from the symphony of plant nutrients found in whole foods, researchers have been providing a broad foundation of evidence backing up the benefits of eating the rainbow.

Red Phytonutrients: Lycopene in Red Foods

Red foods have a reputation for the protective powers they pass on to us when we eat them. Studies have shown that consuming red foods high in the phytonutrient lycopene greatly reduce the risk of heart disease, cancer, and other ailments. Illustrating this cancer-fighting power of red foods is several studies where scientists introduced ground up apple peels to various cancer cell cultures. In every such study researchers have found that apple peels, or extracts of, either kill cancer cells or inhibit their growth. In one study researchers from the University of Wisconsin concluded:

“Our data demonstrated that APE (appeal peel extract), from organic Gala apples, imparted significant reduction in the viability of a variety of cancer cell lines.”

Cornell University has conducted multiple studies that have helped to advance our understanding of the protective benefits we can get simply by eating apples. In 2007 Rui Hai Liu, Cornell associate professor of food science, led a study that identified dozens of compounds that may be responsible for apple’s anti-cancer action, including three compounds that were previously undiscovered. The study was published in the Journal of Agricultural and Food Chemistry. In an article for the Cornell Chronicle Liu states:

“We found that several compounds have potent anti-proliferative activities against human liver, colon and breast cancer cells and may be partially responsible for the anti-cancer activities of whole apples.”

The research is giving a new depth of understanding to the old adage that an apple a day keeps the doctor away.

Eat Your Reds: You can find lycopene in red foods including red apples, red bell pepper, raspberries, watermelon, tomatoes, strawberries, pomegranate, and chili peppers.

Orange Phytonutrients: Carotenoids in Orange Foods

Beta-carotene is arguably the most famous carotenoid, a group of phytonutrients found in orange-hued foods. There are more than 600 carotenoids which give red, orange, and yellow foods their brilliant hues. Carotenoids are antioxidants that help protect the body’s cells and tissues. Some carotenoids can be converted to vitamin A by the body. Vitamin A is important for eye health and a functioning immune system. Consuming foods high in carotenoids also helps protect against the leading cause of irreversible blindness among adults–age-related macular degeneration (AMD). A 1994 study published in the Journal of the American Medical Association looked at how various nutrients impacted AMD. The study included 356 subjects who were diagnosed with AMD as well as 520 control subjects and tested multiple other nutrients to see which might correlate to declining eye health. The researchers found that the more carotenoids people consumed, the lower their risk for AMD.

“A higher dietary intake of carotenoids was associated with a lower risk for AMD. Adjusting for other risk factors for AMD, we found that those in the highest quintile of carotenoid intake had a 43% lower risk for AMD compared with those in the lowest quintile.”

If eating carotenoids lowered your risk of losing your vision by 43%, would you eat more carrots? If you slice a carrot into rounds it will resemble an eye —a good reminder that orange foods help protect healthy vision and to include more orange foods in your diet.

Eat Your Oranges: Persimmons, butternut squash, cantaloupe, clementines, delicata squash, apricots, tangerines, carrots, oranges, mango, papaya, nectarine, sweet potato, pumpkin, turmeric root, yam, and mandarins are great sources of carotenoids.

Yellow Phytonutrients: Lutein and Zeaxanthin in Yellow Foods

Yellow foods are known to contain compounds that are anti-cancer, anti-inflammatory, and which help protect the heart, brain, eyes, and skin. Lutein and zeaxanthin are two types of carotenoids found in yellow foods that protect against macular degeneation and cataracts. Like the phytonutrients found in orange foods, those in yellow foods protect the eyes. In a review of the research for the journal Nutrients, a team of Italian researchers write,

“A number of studies have suggested that lutein may indeed have favorable effects via anti-inflammatory activity, improving cognitive functions, and decreasing the risk of cancer, cardiovascular disease, and other systemic conditions.”

While much of the research on the medicinal effects of carotenoids focus on vision, some research has looked at the concentration of these nutrients in the brain and how they impact brain function. A  study published in the Journal of Gerontology: Medical Sciences in 2017 found a positive correlation  between brain performance and lutein and zeaxanthin levels in the blood. The study included 4,076 adults age 50 years and older. The researchers write:

“Higher plasma lutein and zeaxanthin were independently associated with better composite scores across the domains of global cognition, memory, and executive function. We also found evidence that higher plasma zeaxanthin, but not lutein, was associated with better processing speed. These associations were consistent across domains.”

Another study published in 2014 in the Journal of Pediatric Gastroenterology and Nutrition examined the brain tissues of 30 infants who had died in the first 1.5 years of life and found that lutein and zeaxanthin were two of the major carotenoids in their brain tissue. Lutein accounted for 59% of total carotenoids in the infant brains, a much greater share of the carotenoid pie than lutein would represent in their diet. They concluded that lutein may serve an important function in healthy brain development writing,

“These data reveal preferential accumulation and maintenance of lutein in the infant brain tissue despite underrepresentation in the typical infant diet. Further investigation on the impact of lutein on neural development in preterm infants is warranted.”

The nutrients in yellow foods appear to be important for maintaining healthy vision and a healthy brain.

Eat Your Yellows: Yellow foods like pears, corn, pineapple, potatoes, bell peppers, asian pears, summer squash, lemon, yellow apples, and bananas contain the phytonutrients lutein and zeaxanthin. 

Green Phytonutrients: Glucosinolates and Phytosterols in Green Foods

What are phytonutrients? green food color groupGreen foods are notorious for their antioxidant, anti-cancer, and other health-promoting benefits. The sharp color and odor of cruciferous vegetables—such as broccoli, kale, cabbage, and brussels sprouts—are thanks to the glucosinolates. The glucosinolates found abundantly in these crunchy plant foods are likely responsible for many of the health benefits they are known for. For starters, these phytonutrients help prevent the development and growth of cancer. According to Oregon State University,

“High intakes of cruciferous vegetables have been associated with lower risk of bladder, breast, colorectal, endometrial, gastric, lung, ovarian, pancreatic, prostate, and renal cancer.”

Glucosinolates’ anti-cancer actions include detoxifying carcinogens in the body, limiting the production of cancer-related hormones, and preventing tumor growth.

The phytonutrients found in green foods are known to protect against heart disease and cancer.
The phytonutrients found in green foods are known to protect against heart disease and cancer.

Phytosterols are another group of phytonutrients found in green foods that deliver amazing health protection benefits. Phytosterols help regulate cholesterol levels, thus reducing the risk of heart disease. Their medicinal magic comes from the fact that they are structurally similar to cholesterol and so they compete with cholesterol for absorption in the digestive system.

Cholesterol and plant sterols are structurally similar and compete for absorption in the body’s digestive system. Image from Jones, Peter “Cholesterol-lowering action of plant sterols,” Current Atherosclerosis Reports,1999.

In 2010 a study published in the American Journal of Clinical Nutrition found a direct dose-dependent response relationship between  consumption of phytosterols and cholesterol absorption. They concluded that:

“…phytosterol intakes significantly increased total fecal cholesterol excretion and biliary cholesterol excretion and reduced percentage intestinal cholesterol absorption.”

The more phytosterols are around, the less able your body is to absorb cholesterol. These plant nutrients found in green foods appear to assist extra cholesterol in exiting the body, thus avoiding the gradual buildup that can clog the blood’s passageways leading to high blood pressure and heart disease. Protect yourself from heart disease and cancer, the two leading causes of preventable death today, by eating whole green foods.

Eat Your Greens: There is an abundance of green foods to choose from: green apple, kiwi, green pear, lettuce, arugula, spinach, parsley, broccoli, cabbage, lime, avocado, green grapes, mustard greens, kale, horseradish, lettuce, peas, bean sprouts, and olives are all healthy choices in the green group.

Blue and Purple Phytonutrients: Anthocyanins and Resveratrol in Blue/Purple Foods

What are phytonutrients? purple food color groupAnthocyanins are the pigments that give blue, purple, and red foods their brilliant hues. These particular pigments belong to a class of plant chemicals call flavanoids, a group of phytonutrients that include over 4,000 aromatic plant compounds. Anthocyanins are a primary member of this group of plant nutrients known for their anti-oxidant action. Throughout folk history foods with the blue/purple hue of anthocyanins have long been believed to have special medicinal benefits. More recently scientific studies of anthocyanins have provided evidence backing up their beneficial effects.

Good for Vision: Studies have verified that anthocyanin pigment can improve vision—particularly night vision—when given to human and animal subjects.

Prevents Cancer Growth: Other studies have shown that anthocyanin both reduces cancer cell proliferation and tumor formation. This anti-cancer action has been observed in both in vitro and in vivo trials.

Blueberries and blackberries are excellent sources of anthocyanin.
Blueberries and blackberries are excellent sources of anthocyanin.

Improves Brain Function: There has also been research into the anti-aging and brain-boosting action of these compounds. In a review of the research published in the Journal of Biomedical Biotechnology, Mary Ann Lila describes a study where purple foods appear to reverse brain function loss associated with aging in mice. She writes,

“Cho et al reported that administration of isolated semi purified anthocyanin from purple sweet potato enhanced cognitive performance as assessed by passive avoidance tests in ethanol treated mice, and also effectively inhibited lipid preoccupation in rat brain tissues. By administering blueberry extracts with significant anthocyanin content (but not purified pigments), it was noted that the blueberry-supplemented diets let to effective reversal of age-related deficits in various neural and behavioral parametric (memory and motor functions).”

The mice brains appear to have reversed in age simply by eating natural  blue and purple pigments from plant foods. Additional evidence suggests consuming foods high in anthocyanins helps to prevent both neurodegenerative disorders and atherosclerosis (hardening of the arteries).

Eat Your Blues and Purples: Get your blue/purple phytonutrients from foods like blueberries, blackberries, eggplant, figs, olives, grapes, prunes, raisins, purple carrots, purple cauliflower, cabbage, and black rice.

Eat Your Whites and Tans Too!

What are phytonutrients? white food color group

Not to be forgotten are all the nutrient-dense white, tan, and brown foods that also contain an array of phytonutrients. Some of the compounds common in this color group include allicin, allyl sulfides, cellulose (fiber), lignins, lignans, sesamin, sesamol, tannins, terpenoids, and theobromine.  Many white and brown foods are actually the seeds of plants—including grains, beans, legumes, and nuts. Seeds contain everything needed to grow an entire new plant and are thus a dense source of nutrients including fiber, protein, vitamins and minerals.

Beans and legumes are so beneficial for health that they are now being referred to as, “the most important dietary predicator of survival in older people.” This is according to one study of 785 adults, age 70 years and older, from Japan, Sweeden, Greece, and Australia. The seniors in the study were followed for up to seven years, tracking details of their diet. The data revealed that the single biggest predictor for survival among the group was how much beans they had been eating. No matter where the study subjects lived, having more legumes in the diet appeared to have life-extending effects. The study was published in the Asian Pacific Journal of Clinical Nutrition where the authors write,

“…the legume food group showed 7-8% reduction in mortality hazard ratio for every 20g increase in daily intake with or without controlling for ethnicity (RR 0.92; 95% CI 0.85-0.99 and RR 0.93; 95% CI 0.87-0.99, respectively). Other food groups were not found to be consistently significant in predicting survival.”

Eat Your Whites and Tans: To benefit from the phytonutrients in the white and tan color group you can choose from numerous whole plant foods including onions, garlic, cauliflower, white beans, mushrooms, ginger, pumpkin seeds, cashews, rice, oats, barley, coffee, pears, apples, coconut, ginger, dates, jicama, legumes, nuts, soy, and tea.

Eating the Rainbow

Recent research on the health benefits of phytonutrients has changed the way nutrition experts approach a balanced diet. Rather than focusing on food groups, counting calories, or specific macronutrients, today’s nutrition experts recommend you focus on eating a rainbow of whole plant foods.

Rainbow Salad
Rainbow Salad* contains foods from all the color groups.

Eating the rainbow ensures you get the full spectrum of phytonutrients that nature has to offer, and all the health and protective benefits these foods provide. For optimal health, aim to eat a rainbow every day.

Healing With Plants is empowering people to heal themselves at home, with plants. Explore more nutrition facts, healing whole foods plant-based recipes, and inspiring stories that testify for the amazing healing power of plants. “What Are Phytonutrients” introduces the the importance of eating the rainbow of plant foods.

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Reya Steele Andrews

Reya (Steele) Andrews is a holistic health writer, educator, and publisher at Healing With Plants. Reya is a certified Holistic Nutritionist (AFPA), is certified in Plant-based Nutrition, and teaches nutrition science and healthy food preparation. Find her book, The Frugivore Diet, on Amazon.

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