Introduction
As a nutritionist, I am often asked about the health benefits of different foods. One food that consistently tops the list as being good for you is apples. Apples have many health benefits, which can be attributed to their high antioxidant content, including a group of compounds known as polyphenols. In this article, I will provide an overview of apple polyphenols, including what they are, their health benefits, what foods contain them, and some of the best dietary sources.
What are apple polyphenols?
Apple polyphenols are a type of natural plant compound found in apples. Polyphenols act as antioxidants within the apple, protecting the fruit from factors such as sun exposure, insects, and fungal infections. There are over 8,000 known polyphenol compounds found in plant foods.
In apples, some of the most active and beneficial polyphenols include:
Quercetin: This flavonoid has strong antioxidant and anti-inflammatory properties.
Catechin: This flavanol-type polyphenol may help regulate blood sugar.
Chlorogenic acid: This polyphenol is thought to help moderate carbohydrate metabolism.
Epicatechin: This flavanol exhibits antioxidant activity and is linked to potential heart health benefits.
Procyanidins: These condensed tannins help give apples their astringency and support the cardiovascular system.
Many polyphenols in apples are found in the skin, as this is where the pigments that produce the red, green, and yellow colors are located. The flesh of apples contains fewer polyphenols, but still contributes to their overall content.
apple polyphenols benefits
A diet rich in apple polyphenols has been linked to many potential health benefits:
Antioxidant effects: Polyphenols act as antioxidants that may protect cells from oxidative stress and lower inflammation. This can reduce risk factors for various chronic diseases.
Heart health: The polyphenols in apples may support healthy cholesterol levels, blood pressure, and vascular function. Apples have been associated with a lower risk of cardiovascular disease.
Blood sugar regulation: Compounds like chlorogenic acid help slow the digestion of carbohydrates and the absorption of sugar, which can stabilize blood sugar spikes after meals.
Gut health: Apple polyphenols act as prebiotics in the digestive system, promoting the growth of beneficial bacteria in the gut microbiome. This supports digestive and immune function.
Anti-cancer activity: Laboratory studies indicate apple polyphenols may inhibit cancer cell growth, particularly of colon, liver, and lung cancer cells. More research is needed to confirm effects in humans.
Brain health: Quercetin and other apple polyphenols aid neuron signaling pathways involved in learning and memory. They may help protect the brain from neurodegenerative diseases like Alzheimer's and Parkinson's.
The effects of apple polyphenols in isolation are still being elucidated. But eating whole apples appears to provide antioxidant, anti-inflammatory, and prebiotic benefits.
Do apples have polyphenols?
Yes, apples are one of the best dietary sources of polyphenols. Many large-scale observational studies show health benefits associated with eating apples.
Some research indicates that the average apple contains anywhere between 100-300 mg of polyphenol compounds. However, the exact polyphenol content can vary:
Type of apple: Red apple varieties including Red Delicious, Braeburn, and Gala tend to be highest in polyphenols. Granny Smith and Golden Delicious apples contain fewer polyphenols.
Portion of apple: The skin contains 3-6 times more polyphenols than the flesh. So eating a whole apple, versus just the insides, provides more polyphenols.
Ripeness: Mature, ripened apples contain more polyphenols than unripe, green apples. The polyphenol content increases as chlorophyll breaks down during the ripening process.
Processing: Apples lose polyphenol content when processed into juices, sauces, jams or when dried/frozen. Whole fresh apples provide the most benefit.
What are the 4 types of polyphenols?
There are over 8,000 identified polyphenol compounds, which are categorized into four main classes:
Flavonoids: This includes flavonols like quercetin, flavan-3-ols like catechin, anthocyanins, and more. They are found in many fruits, vegetables, red wine, and tea.
Phenolic acids: These include compounds like gallic acid and ellagic acid. They are found in berries, some fruits, coffee, and whole grains.
Stilbenes: Resveratrol is a key stilbene; it's found in red wine and grape skins. Stilbenes act as phytoalexins, compounds produced by plants as a defense mechanism.
Lignans: Found in flaxseeds, sesame seeds, legumes, cereals, and certain vegetables. They exhibit estrogen-like activity in humans and may play protective roles.
Each polyphenol type has unique health effects due to differences in their chemical structure and metabolism in the body. Getting a mix of polyphenols from various sources is ideal for overall health.
What is the best source of polyphenols?
Some of the foods highest in polyphenols include:
Cloves
Cocoa powder
Dark chocolate
Pecans
Black elderberry
Blueberries
Raspberries
Coffee
Apples
Cherries
Artichokes
Capers
Black olives
Hazelnuts
For most people, focusing on eating a balanced diet with a variety of fruits (especially berries), vegetables, nuts, seeds, whole grains, and plants like traditional herbs and spices will provide beneficial levels of polyphenols.
Drinking moderate amounts of coffee and red wine, which are rich in unique polyphenols, may also contribute to total intake for some individuals. But fruits and vegetables should make up the core food sources.
What foods are high in polyphenols?
Here is an overview of some foods particularly high in polyphenols:
Fruits:
Berries, especially blackberries, strawberries, blueberries, raspberries
Cherries
Plums
Apples
Pears
Oranges
Grapes/red wine
Kiwi
Pomegranate
Vegetables:
Onions
Spinach
Kale
Broccoli
Artichokes
Potatoes
Carrots
Asparagus
Okra
Beets
Red cabbage
Herbs, spices, nuts and grains:
Cloves
Oregano
Cocoa powder
Dark chocolate
Pecans
Hazelnuts
Whole wheat
Oats
Black rice
Legumes:
Soybeans
Red kidney beans
White beans
Lentils
Oils and drinks:
Extra virgin olive oil
Flaxseed oil
Green/black tea
Red wine
Coffee
Conclusion,
Apple polyphenols are a type of antioxidant plant compound that exhibits many potential health benefits. Apples are among the best sources of dietary polyphenols, with most contained in the skin. Eating whole apples, preferably organic, provides polyphenols like quercetin, catechin, chlorogenic acid, and epicatechin. These compounds help fight inflammation, protect cardiovascular health, balance blood sugar, enhance gut microbiota, and may have anti-cancer effects. Aim for a diet that focuses on a variety of fruits, veggies, herbs, spices, beans, nuts, whole grains, and plant-based beverages for an optimal mix of polyphenols. Incorporating apples as a daily snack or food is an easy way to promote overall wellbeing.
References:
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Crozier, S. J., et al. "Polyphenol compounds in the human diet: relationships with digestion and absorption." Critical reviews in food science and nutrition 50.2 (2010): 154-183.
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Smeriglio, Antonella, et al. "Polyphenols in fruit and vegetables and its effect on human health." International Journal of Molecular Sciences 21.22 (2020): 8373.
Francini, Alessandra, and Luca Sebastiani. "Phenolic compounds in apple (Malus x domestica Borkh.): compounds characterization and stability during postharvest and after processing." Antioxidants 2.3 (2013): 181-193.
