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According to some, apples are the second most popular fruit in the world but how do you eat yours? Do you peel it, core it, chop it, or eat it whole? However you choose to eat an apple, it’s bursting with nutrients and if you’re removing the skin before you eat it, read on to find out why you shouldn’t (or if you do why you should get yourself a pot of Apple Peel Powder instead).
“An apple a day can keep the doctor away” is a famous saying but here we’re specifically going to focus on the peel. It’s not to everyone’s taste but nestled inside the crunchy outside of the apple is an array of nutrients, including fibre, vitamins, and minerals.
The peel is also home to some pretty special antioxidants. Many of the protective benefits associated with fruits and vegetables can be attributed to antioxidants and phytochemicals[i].
One of those is quercetin, which has been linked to lowering the risk of diabetes, heart disease, and even cancer[ii]. Quercetin can be referred to as a phytochemical, polyphenol or flavonoid.
Quercetin is a potent antioxidant flavonoid, or more specifically a flavonol. It’s a plant pigment and is found in many foods, including:
The beneficial effects of flavonoids like quercetin are derived from their functions as antioxidants in the body. Antioxidants are compounds that bind to free radicals to neutralise them and stop them from causing you harm. They’re a bit like a security guard escorting a rowdy person out of a public building.
When free radicals are in a high abundance in the body, they can cause cellular damage which is linked to several chronic illnesses.
Quercetin is the most consumed flavonol in the human diet. Flavonols are a subgroup of flavonoids, natural substances that are found in deep-coloured foods. Flavonols have a ketone group and are associated with a wide range of health benefits and antioxidant potential. They are the largest and most common flavonoid subgroup[iii].
When you eat foods containing quercetin, a small amount is absorbed in the stomach, but the major absorption site is the small intestine. Any unabsorbed quercetin passes to the colon, where it is used up by the colonocytes, the cells lining your bowel.
Bacteria, including Eubacterium ramulus, Clostridium orbiscindens, Eubacterium oxidoreducens, and the Butyrovibrio spp.transform quercetin into the following metabolites:
These metabolites are then transported to tissues and cells throughout the body via the circulatory system, where they are thought to have a greater health impact than the original quercetin[iv]. For example, in a study by Vissiennon et al (2011) p-hydroxyphenylacetic acid and 3,4-dihydroxyphenylacetic acid had an anti-anxiety effect[v].
Quercetin has been linked to a variety of health properties. The potent antioxidant and anti-inflammatory effects of this flavonoid have generated much scientific interest. Here, we’ll delve into some of those effects backed up by science.
The most revered property of quercetin is its antioxidant potential. It can neutralise free radicals travelling around the body, limiting the damage they cause. When there is a build-up of free radicals, it can lead to a phenomenon called oxidative stress, so keeping them in check with antioxidants can help limit the development of chronic and age-related diseases[vi].
Research has shown that quercetin has neuroprotective benefits against chronic Alzheimer’s Disease. Specific proteins called FoxO, which are key substrates of SIRT1, are necessary for the formation of memory and cognitive function. Dysfunction in these proteins or transcription factors has been associated with numerous age-related diseases, including Alzheimer’s[vii]. Quercetin targets SIRT1 to regulate cellular senescence and age-related cellular processes[viii].
A further study by Elreedy et al (2022) found that quercetin when administered with aluminium chloride, resulted in a significant improvement in short-term memory in rodents. The study found that its benefits were linked to its ability to reduce the expression of a hallmark Alzheimer’s Disease gene[ix].
Wherever there’s a chronic disease, inflammation is never far behind. Quercetin can prevent inflammation by reducing the production of inflammatory cytokines. This can help to prevent inflammatory disease and pain associated with inflammation[x].
In a study by Kim et al. (2019) quercetin was found to reduce the clinical symptoms of arthritis by stopping the release of inflammatory cytokines, such as interleukin-17, and could have the potential to become a therapeutic agent for bone destructive processes seen in rheumatoid arthritis[xi].
A further study by El-Said et al (2022), demonstrated quercetin from Egyptian Fenugreek seeds has an anti-inflammatory effect in rodent models against rheumatoid arthritis. That’s because it can downregulate the expression of adenosine deaminase (ADA) genes. ADA is an inflammatory enzyme that causes pain and joint stiffness in rheumatoid arthritis patients[xii].
There is a lot of research into the effect of quercetin on heart health. A study published in 2007 investigated the effects of quercetin on high-blood pressure patients and those with prehypertension. The researchers found that quercetin reduced, systolic, diastolic and mean arterial pressure in high blood pressure patients. Blood pressure was unchanged in prehypertensive patients[xiii].
Several studies have also shown that quercetin can reduce the progression of atherosclerosis in animal models. A study by Juźwiak et al. (2005) investigated the effects of quercetin on high blood fat levels and the development of atherosclerotic plaques in animal models. It was shown that quercetin reduced triglyceride and cholesterol levels caused by eating a high-fat diet after 3 months. Quercetin also lowered the formation of plaques in the aorta and carotid artery in animals fed a high-fat diet[xiv].
Quercetin’s anti-inflammatory and antioxidant properties help to bolster the immune system. Animal studies have shown that quercetin may have an important role in relieving allergy symptoms.
For example, quercetin supplementation in animals has shown that this potent flavonoid could protect against immunoglobulin E-mediated food allergies, such as peanuts[xv]. As well as anti-allergic properties, quercetin is also known for its antioxidant activity and stimulation of the immune system, which means it can be used in the treatment of other illnesses such as bronchial asthma and allergic rhinitis[xvi].
An emerging area of research for quercetin is cancer prevention. Early studies are showing that quercetin can increase cell apoptosis, effectively cell suicide, and autophagy. It can also prevent metastasis of cancer cells[xvii].
Currently, this research is in its early stages, so more research is needed. However, the inclusion of quercetin could have some potent protective benefits.
Although quercetin steals the spotlight because of its numerous, and quite frankly remarkable, health benefits, apple peel in general is a treasure trove of nutrients.
One of which is fibre. The peel of an apple contains a large proportion of its overall dietary fibre content. Fibre can support the normal function of your gut microbiome and regular bowel movements, preventing constipation.
Apple peel is also packed with phenols, like polyphenols (including quercetin), that can improve digestion, cognitive function, blood sugar levels and a whole host of other wonderful things.
Zahid et al (2023) investigated the stability and bioaccessibility of freeze-dried apple peel powder in invitro digestion and colonic phases. They found that gut microbes utilised the phenolic compounds present in the apple peel powder. The fermentation of the peel caused a reduction in pH, increasing the abundance of Bifidobacteria.Therefore, the study showed that freeze-dried apple peel powder could support the growth and activity of intestinal bacteria, demonstrating its prebiotic effects, which in turn could support your health[xviii].
Squeezing quercetin, and more specifically apple peels, into your diet couldn’t be easier with our Organic Apple Peel Powder. Each 4.2g serving of apple peel powder is bursting with vitamins A and C, potassium, calcium, folate and iron. It’s also bursting with polyphenols that will support the growth and activity of your gut microbiota.
Check out our prevention and repair recipes to show you how you can easily incorporate this pot of magic into your diet or combine it with our PureHMO® range for a simple gut health smoothie.
Despite being discarded in favour of the flesh, apple peel is a powerhouse of nutrition and health benefits. It contains an array of nutrients, including flavonols, like quercetin, which offer antioxidant and anti-inflammatory effects, as well as benefits for your heart health, immunity, and potentially even cancer protection.
Why not explore the world of apple peels and incorporate them into your diet, to give your body a nutritious boost?
Written by: Leanne Edermaniger, M.Sc. Leanne is a professional science writer who specializes in human health and enjoys writing about all things related to the gut microbiome.
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