Study after study after study has shown that a diet high in fruits and vegetables is especially beneficial to human health and can even reduce the risk of many serious health conditions.[4, 5] Phytochemicals may be one of the reasons why.
Phytochemicals are chemical compounds produced by plants. They are commonly found in fruits, vegetables, nuts, legumes, and grains. Phytochemicals are frequently confused with phytonutrients. Whereas phytochemicals include plant compounds that are beneficial as well as those that are detrimental, phytonutrients specifically refers to compounds that have a positive effect. In other words, all phytonutrients are phytochemicals, but not all phytochemicals are phytonutrients.
The distinction between phytochemicals and phytonutrients is an important one, as not all phytochemicals are beneficial. Technically, cocaine, codeine, oxycodone, and nicotine are all phytochemicals. Even ricin, one of the most deadly and potent poisons in the world, is a phytochemical. This doesn’t mean that all phytochemicals are bad, quite the opposite. Some phytochemicals offer incredible health benefits.
Types of Phytochemicals
There are thousands of different phytochemicals. Here are a few that are of particular interest from a dietary perspective.
Carotenoids are plant pigments responsible for the yellow, orange, and red color of many fruits and vegetables, including red peppers, papayas, paprika, tomatoes, and watermelon. There are more than 750 types of carotenoids, the one you’re probably most familiar with is beta-carotene. Beta-carotene gives carrots, pumpkins, and sweet potatoes their rich orange pigmentation. Beta-carotene also offers a number of health benefits; the human body even converts it into vitamin A. Other carotenoids include alpha-carotene, beta-cryptoxanthin, lutein, zeaxanthin, and lycopene.
Carotenoids are strong antioxidants. Antioxidants can help reduce the oxidative damage caused by free radicals. Epidemiological studies have shown a link between dietary intake of carotenoids and a reduced risk of many diseases.
Carotenoids are why carrots are credited as being good for the eyes. One of the reasons eyesight gets worse with age is because absorbing short-wave blue light (tablets, smartphones, and televisions are a major source of short-wave blue light) causes oxidative damage. Lutein and zeaxanthin filter blue light and protect the eyes like tiny, internal sunglasses.[10, 11]
Polyphenols are the largest group of phytochemicals with over 8000 identified compounds. Like carotenoids, polyphenols are powerful antioxidants. Polyphenols can be split into several subgroups, including flavonoids and lignans.
Flavonoids are a subgroup of polyphenols, and a large family of phytonutrients themselves. There are over 4000 individual flavonoids and several subclasses of flavonoids, including anthocyanins, flavonols, flavanols, flavanones, flavones, and isoflavones.
Of these, flavonols are the most common in the human diet. They’re found in apples, apricots, beans, broccoli, cherry tomatoes, chives, cranberries, kale, leeks, pears, onions, red grapes, sweet cherries, and white currants.
The similarly named flavanols (not to be confused with the previously mentioned flavonols — note the a and the o) are another subgroup of flavonoids. To avoid obvious confusion, flavanols are sometimes referred to by their less elegant name flavan-3-ols. They can help reduce the risk of cardiovascular disease and lower blood pressure. Dark chocolate is an excellent source of flavanols.
Like carotenoids, anthocyanins are plant pigments. They are responsible for the rich reds, blues, and purples found in fruits and vegetables. High concentrations of anthocyanins are found in blueberries, cranberries, strawberries, raspberries, blackberries, cherries, eggplants, grapes, red cabbage, and red apples.
Anthocyanin-rich plants have been used in folk medicine for centuries and we’re just now rediscovering their benefits. Anthocyanins are strong antioxidants that can help protect the liver, improve eyesight, reduce blood pressure, and even reduce the risk of many serious diseases.
Lignans are another type of polyphenol. They’re found in seeds, grains, legumes, fruits, berries, and veggies. Flaxseeds are the richest dietary source of lignans and crushed or milled flaxseed is the most bioavailable source. A diet heavy in lignan-rich food seems to have beneficial, protective effects on the body. Animal studies have found that lignans may have anticarcinogenic effects.
Indole-3-carbinol (I3C) is a phytonutrient that's highly concentrated in cruciferous vegetables like broccoli, brussels sprouts, cauliflower, collard greens, kale, and cabbage. A diet high in cruciferous vegetables has long been associated with a lower risk of several types of cancer. I3C may be the mechanism behind this defense. Animal tests have found that I3C supports normal cell development and protects against DNA damage.
Isoflavones are phytoestrogens — plant compounds that mimic the effects of estrogen in the human body. Soybeans are an especially rich source of isoflavones sometimes referred to as soy isoflavones.
Because they mimic the effects of estrogen, isoflavones can cause hormonal disruptions in both men and women. They can bind to and block the body’s natural estrogen receptors. Isoflavones can inhibit thyroid function, and even increase the risk of breast cancer. In my opinion, it’s best to limit your intake of isoflavones, soy, and soy products.
You’ve probably heard of the so-called “French Paradox” — the phenomenon of low rates of heart disease in France despite a diet relatively high in saturated fats. Many speculate it's influenced by daily, moderate consumption of red wine. Resveratrol may be the primary agent responsible for the healthy effects of red wine.
Plants produce resveratrol to help protect against harmful organisms and environmental challenges, like drought. Resveratrol offers many benefits to humans as well, including heart-protective effects and defense against many degenerative health conditions because of its antioxidant action.
While the incredible benefits of resveratrol appear to be real, the hype behind red wine is less so. When studies about resveratrol made the news a few years ago, media outlets went crazy with headlines like “Can Drinking Red Wine Help You Live Forever?” These hyperbolic headlines turned out to be more sensational than fact. While certain red wines do contain resveratrol, the amount varies by quality and grape variety.
The publicized health benefits of resveratrol have also resulted in the market being flooded with low-quality wine by those hoping to cash in. There was a report a few years ago that found dozens of wine brands were contaminated with arsenic. Even if you find an excellent red wine, be sure to exercise moderation. Alcohol can upset your gut microbiome, disrupt your hormones, and damage your liver.
Fortunately, red wine is not the only source of resveratrol. Resveratrol is found in grapes, peanuts, pistachios, blueberries, cranberries, mulberries, lingonberries, and even dark chocolate.
Getting the Right Phytochemicals
Phytochemicals are not a magical health elixir but they are something to consider when planning a healthy diet. When combined with regular exercise, a balanced, plant-based diet that provides a variety of beneficial phytochemicals and phytonutrients can contribute greatly to your overall health. Currently, there is no official recommended daily allowance for phytochemicals but regularly consuming a variety of fruits and vegetables will ensure you receive a steady, diverse supply.
Plant-based food is the best way to get valuable phytochemicals into your body and, in fact, plants are the only natural source of phytochemicals. Some nutritional supplements contain phytochemicals that have been extracted from plants (and some contain synthetically produced versions, which I prefer to avoid). It's always best to talk to your trusted healthcare professional who can evaluate your individual needs before taking any new supplements.
Have you had any experience incorporating more phytonutrients into your diet? Leave a comment below and share your thoughts with the community.
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†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. If you have a severe medical condition or health concern, see your physician.