Brightly colored fruits and vegetables contain phytonutrients like carotenoids and flavonoids, pigments and natural chemical compounds that promote health.

Phytochemicals: Carotenoids and Flavonoids

By Stephen T. Sinatra, M.D., F.A.C.C., F.A.C.N., C.N.S., C.B.T.

Most of us know that fruits and veggies are good for us…maybe we’ve read up on the health benefits associated with a diet rich in them, or are lucky enough to have been pleasantly haunted by the words, “eat your veggies,” since childhood. While mom just seemed to know that if it came from Nature, it was probably packed with the stuff we need to keep healthy, scientists have told us that vitamins, minerals, fiber and phytochemicals (also called   phytonutrients) in plants are some of the specific substances that nourish, sustain, and protect our bodies.

Very Important Phytochemicals: Carotenoids

If the food your eating is orange or red by Nature’s design, chances are you’re consuming carotenoids, a class of naturally occurring red, orange and yellow plant pigments. While there are over 600 carotenoid phytochemicals found in nature, six most commonly find their way onto our plates: beta-carotene, alpha-carotene, lycopene, beta-cryptyzanthin, lutein and zeaxanthin. Many foods contain a combination of these carotenoids, all of which are antioxidants. Found primarily in carrots, pumpkin, tomatoes, cantaloupe, papaya, oranges, and dark-green leafy vegetables, carotenoids are associated with a strengthened immune system and lowered incidence of cardiovascular disease, eye diseases, and cancer.

Lutein and Zeaxanthin are the only two carotenoids found in the retina, and may protect against cataracts and age-related macular degeneration (blindness), for which there is no cure. These carotenoids may be found in green, leafy vegetables, peas, and pumpkin. Primarily found in tomatoes and tomato products like sauce and salsa, lycopene is one of the most potent carotenoid antioxidants. Several studies suggest that lycopene-rich diets are associated with reduced risk of prostate cancer.

One of the reasons carotenoid phytochemicals may protect against cancer is that they help facilitate communication between cells, which keeps the cells differentiated. Eating a diet rich in a variety of carotenoids (not just beta-carotene) has also been linked to a lowered risk of lung cancer in studies, which suggests that carotenoids work best synergistically. Fat-soluble carotenoids, which hitch a ride through the body on lipoproteins, may also help prevent cardiovascular disease by protecting LDL molecules from oxidation. Because carotenoids are fat-soluble, it’s important to eat them with at least 3 to 5 grams of healthy fat to insure that the small intestine absorbs them.

Pro-vitamin A Carotenoids

Beta-carotene, alpha-carotene and beta-cryptyzanthin are provitamin A carotenoids, which means that our bodies can convert them to retinol, a form of vitamin A; beta-carotene is the one which converts most efficiently. We need vitamin A for numerous reasons. It is crucial for normal growth and development (especially of bone tissues) and for reproductive health. Vitamin A protects our eyes, and most importantly, helps make the white blood cells our immune systems need to defend against illness and infections. There can be too much of a good thing with vitamin A, though: long term ingestion of more than 5000 IU vitamin A per day is linked to osteoporosis and acute toxicity (hypervitaminosis A) may occur with extremely high vitamin A consumption (500,000+ IU), through over-supplementation, for example.

Carotenoid Phytochemical Sub-class  Sources  Health Benefits
Beta-carotene Foods: Carrots, pumpkin, spinach, kale, sweet potatoes, winter squash, cantaloupe, broccoli, mangoes, apricots, and red peppers.


Supplements: Beta-carotene

*Pro-vitamin A – efficiently converts to retinol; promotes growth and development, and immune system health.
Alpha-carotene Foods: Winter squash, pumpkins, and carrots. Pro-vitamin A; promotes growth and development, and immune system health.
Lycopene Foods: Tomatoes,watermelon, pink grapefruit, Japanese persimmon.


Supplements: Lycopene

Powerful antioxidant; may protect against prostate cancer.
Beta-cryptyzanthin Foods: Mango, papaya, oranges, tangerines, carrots, red peppers, and pumpkins. Pro-vitamin A; promotes growth and development, and immune system health.
Lutein Foods: Kale, spinach, collard greens, peas, squashes, pumpkin, Brussels sprouts, broccoli, and sweet corn.


Supplements: Free lutein or lutein ester.

Found in the retina; absorbs blue light to protect eyes against oxidative damage.
Zeaxanthin Foods: Same as lutein; also in egg yokes.


Supplements: Free xeaxanthin or xeaxanthin ester.

Found in the retina; absorbs blue light to protect eyes against oxidative damage.

Flavonoids Are Also Very Important Phytochemicals

Flavonoids are natural phytochemical compounds found in fruits, vegetables and beverages (fruit drinks, tea, coffee, beer, wine) which can help protect us against cardiovascular disease and cancer. Not only are flavonoid phytochemicals anti-inflammatory, but they have antimicrobial and antiplatelet capabilities too. They also can extend vitamin C activity in the body, and may help chelate excess metals like iron and copper from the body. Approximately 4,000 flavonoids have been identified (they are generally categorized by subclass) and most foods containing flavonoids feature more than one type.

 Flavonoid Phytochemical Sub-class  Sources  Health Benefits
 Anthocyanidins Food: Berries, cherries, red grapes, plum, red cabbage, and red onion.


Supplements:  Bilberry, elderberry, black current, red grape, blueberry, and mixed-berry extracts.

Can strengthen cellular antioxidant defenses; may help preserve brain function.
Flavanols  – Proanthocyanidins Food: Teas (especially green), cocoa, chocolate, apples, red grapes, berries, cranberries, and red wine.


Supplements: Tea catechin or polyphenol extracts.

Have anti-inflammatory and antioxidant capabilities; may contribute to maintenance of heart health and urinary tract health; can help stabilize collagen (a component of connective tissue, skin, and bone), and promote circulation and oxygenation of the blood.
Flavanones Food: Citrus fruits and juices.



Supplements: Citrus


Protect against oxidative stress; strengthen cellular antioxidant defenses.
Flavonols Yellow onions, leeks, kale, broccoli, teas, apples, and berries.


Supplements: Quercetin (effective at 100+mg doses) and rutin.

Protect against oxidative stress; strengthen cellular antioxidant defenses, can reduce risk of various cancers, cardiovascular disease, asthma, and diabetes.
Flavones Food: Hot peppers, parsley, celery, and thyme.


Supplements: Citrus bioflavonoids.

Anti-estrogenic effects.

Flavonoid phytochemicals can protect us against cardiovascular disease, cancer, age-related cognitive decline, and maybe even neurodegenerative diseases. By helping cells maintain healthy communication (they modulate cell signaling pathways), flavonoids may play a role in the prevention of cancer and cardiovascular disease. Such modulation promotes detoxification of carcinogenic substances, preserves regulation of cell cycles (is anti-mutagenic), decreases inflammation, and helps prevent tumors from spreading. With anti-inflammatory and antiplatelet capabilities, flavonoids also help prevent the sticky, thick blood and blood vessel disrepair that are hallmarks of cardiovascular disease. Additionally, they are cardioprotective because they prevent the oxidation of LDL cholesterol and increase nitric oxide production, which helps relax blood vessels. Onions (quercetin), in particular, simultaneously support blood pressure and reduce LDL cholesterol. By helping chelate metals, flavonoids may play a role in preventing neurodegenerative diseases. Eating plenty of flavonoid-rich fruits and vegetables, as opposed to inflammatory, processed foods, is a crucial part of a health-preserving lifestyle.

Other Phytochemicals of Mention

Cruciferous vegetables like broccoli, cabbage, Brussels sprouts, bok choy, cauliflower, turnip and watercress, contain glucosinolates, sulfur-containing compounds that help prevent cancer when broken down into various isothiocyanates like sulforaphane. Cruciferous veggies are also great defenses against cancer because they are high in fiber, which helps eliminate toxins before they have a chance to enter the bloodstream (this also helps prevent inflammation). Additionally, these veggies are full of cancer-fighting phytonutrients like flavonoids, carotenoids, chlorophyll, potassium, selenium and vitamin C.

Boswellia: Used for centuries by folk healers, boswellia is an anti-inflammatory herb that comes from the resin of the Boswellia Serratatree. Recently boswellia has shown promise as adjunctive treatment for many inflammatory conditions including asthma, inflammatory bowel disease, arthritis, cardiovascular disease, and even cancer because it blocks a pro-inflammatory enzyme (5-lipoxygenase) in the body.

Chlorophyll: A pigment found in green plants and algae which helps protect against cancer by binding with carcinogens before they are absorbed in the gastrointestinal tract. Chlorophyll is most abundant in foods like spinach, parsley, watercress, arugula, and green beans.

Curcumin: A curcuminoid found in turmeric, curry spices, and in supplement form, curcumin is a fat-soluble yellow pigment that has been used for centuries in India as a medicine, spice and dye. Research has shown that curcumin has anti-inflammatory and antioxidant properties, and can increase glutathione (another antioxidant) in cells. By inducing apoptosis (cell death) in cancer cells, curcumin has shown promise as a cancer preventative and adjunctive treatment. It may also prove useful to treat rheumatoid arthritis and Alzheimer’s disease. As curcumin is an anticoagulant, people on blood thinning drugs like Coumadin should talk to their doctors about drug interactions.

Lignans: Lignans are a major class of phytoestrogens found mainly in seeds (flax, sesame, pumpkin, sunflower) and nuts, as well as in legumes, fruits and vegetables. Flax seed (which also contains omega-3 fatty acids and fiber), in particular, is one of the richest food sources of lignans. Plant lignin consumption has been consistently associated with reduced risk of cardiovascular disease, and may help reduce risk of prostate, breast, endometrial and ovarian cancers. Lignans are also available in supplements containing flax seed.

Soy isoflavones (phytoestrogens) are a type of flavonoid that can mimic the effects of estrogen by binding with estrogen receptors in cells. As soy has been a part of traditional Asian diets for centuries, it is thought to be safe, if not beneficial. Scientific evidence has yet to conclusively determine whether high dose supplementation of isoflavones can help prevent or treat osteoporosis, cardiovascular disease, cognitive decline, and breast, endometrial or prostate cancers. Tofu, miso, soybeans, tempeh and soymilk are the best food sources of isoflavones.

Resveratrol is an antioxidant polyphenol that some plants produce in response to injury, stress, infection, or UV radiation. Found in red wine (red grapes), it has been credited with keeping the French healthy despite a high-fat diet (the French paradox). Other food sources of resveratrol include blueberries, cranberries and peanuts. Resveratrol may reduce risk of cardiovascular disease. In animal studies, it has demonstrated promise in helping keep blood vessels clear (vasodilative) and blood thin, as well as preventing blood clots (more research with humans is necessary to determine actual cardiac potential). Resveratrol has also been shown to inhibit cancer cell growth and current clinical trials may determine its value as a cancer preventative or treatment. It is available in supplement and extract form.

Nature Knows Best

Nutritional supplements should be taken to supplement, not replace, already healthy meals. We do need to supplement to make up for nutritional deficiencies in our food that are caused by poor soil quality, environmental pollution, and electrical or emotional stress; however, taking a handful of supplements to balance out a diet of processed and fried foods just doesn’t cut it. There’s something to be said about “Nature knows best.”

Fruits and vegetables contain a mixture of antioxidants and other compounds which work synergistically to keep us healthy. In other words, even if scientists aren’t yet able to explain the exact mechanisms of such synergism, “1 + 1 = 3” when we get a wide variety of antioxidants through various sources. Vegetables and fruits also are full of fiber which we need to help slow down the digestion of sugar and avoid the excess insulin release which can lead to diabetes and obesity. Fiber also decreases transit time of food through the gastrointestinal tract to help prevent accumulation of toxins, which can lead to cancer and other illnesses. Consuming a wide variety of fruits and vegetables, as well as supplements, is the best way to get most of the nutrients we need.

Ideally, we should eat 9 one-half cup servings of fruits and vegetables daily. When possible, eat organically produced fruits and vegetables in order to avoid ingesting toxic chemicals and metals which may be found in the soil of, or sprayed onto, conventionally grown crops. Not only is organically grown produce less toxic, it may protect us better against illness: the natural phytochemical defenses plants have had to develop against insects and disease, in turn, help us.

If you are new to eating lots of naturally colorful foods, at first it may seem to involve too much advance planning and preparation. Unless you’re a chef, grocer or farmer, you probably don’t want your life to revolve around food availability and preparation. Eating fruits and vegetables with each snack and meal gets easier, though, and can become a habit you don’t think twice about if you give it enough time. Although always having fresh fruits and vegetables on hand may seem to cost more money and time, remember – as a preventative measure – the health dividends are worth the investment.


  • Shop for fresh, organic produce at your local farmer’s market or farm stand as much as possible;
  • Shop along the periphery of the supermarket and fill your basket or cart with as much produce as you think you and your family can realistically eat; avoid the center aisles which tend to be filled with processed foods.
  • When preparing and eating foods, fill 2/3 of your plate with fresh, colorful fruits and vegetables.
  • Try, as much as possible, to eat raw fruits and vegetables; cooking them diminishes the nutrients.
  • Fill portable containers with sliced fruit or veggies for snacks.
  • Soak fruits and veggies in water with a few drops of grapefruit seed oil, vinegar, lemon juice, and/or baking soda to help remove bacteria, toxins, and dirt, then rinse.

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