Antioxidants: What They Are, Proven Benefits, Antioxidant Foods and More (Evidence Based)
Antioxidants are naturally occurring compounds that help prevent free radicals from damaging the cells in your body. Antioxidants are found in a many fruits, vegetables, drinks and supplements.
Consuming foods rich in antioxidants is important to help protect your cells from damage caused by free radicals. A buildup of these harmful molecules (reactive oxygen species, or ROS) can increase oxidative stress in your body. This can lead to a number of chronic diseases including heart disease, type 2 diabetes, rheumatoid arthritis, and cancer.
Foods high in antioxidants include fresh fruits and vegetables, legumes, nuts, and berries. Generally, these healthy foods contain antioxidant vitamins such as vitamin A, C, and E. Antioxidant activity in foods also comes from nutrients such as manganese, selenium, and other phytochemicals to help keep you healthy.
Antioxidant drinks also contain compounds with free radical scavenging activity. For example, green tea and red wine contain antioxidant polyphenols that help prevent DNA cell structure damage due to oxidation.
In this article, you will learn about what antioxidants are and why they are so important for your health. You will also find out about the best antioxidant foods that will help keep you healthy.
What are Antioxidants?
Antioxidants are various vitamins, minerals, and phytochemicals that are found in plants and some animal products. Antioxidants work by neutralizing the effects of free radicals and are sometimes referred to as a “free radical scavengers.” (1)
Doctors say that free radicals occur when oxidation in the body creates unstable molecules. These “free radicals” steal electrons from other molecules which can result in DNA damage to cells. Too many of these unstable reactive molecules in the body can result in certain chronic diseases that are difficult to treat. (2)
The journal Antioxidants says that antioxidants are essential for proper kidney, liver, and digestive function. Free radical scavengers are also necessary to lower your risk of heart disease and cancer. (1)
Researchers say that the reason it’s important to eat foods rich in antioxidants is that the body can’t produce some antioxidant vitamins. Enjoying a well-balanced diet that includes antioxidants help keep the proper balance to help boost your health. (3)
Later on in the article, you will find out how scientists measure the levels of antioxidants in foods.
Antioxidants List
Let’s look briefly at the best antioxidants that can contribute to good health and better skin:
Beta-carotene
Beta-carotene is the antioxidant pigment that gives many fruits and vegetables their bright colors. Studies have shown that beta-carotene can promote good health when you get enough of it in your diet. Beta-carotene converts into vitamin A and has been linked to a stronger immune system, good vision, and a lower risk of cancer and heart disease. (4)
Vitamin C
One of the best-known antioxidants is vitamin C which is found in citrus fruits, bell peppers, green vegetables, and berries. Research has shown that the antioxidant properties of vitamin C help protect the body from the damaging effect of free radicals. Vitamin C has been linked to a healthy immune system with fewer infections, better vision, improved heart health, and a lower risk of cancer. (5)
Vitamin E
Another vitamin with powerful antioxidant activity is vitamin E. Studies have shown that all forms of vitamin E help to neutralize the effects of free radicals and also lower inflammation. Many nuts, seeds, and healthy oils are good sources of vitamin E. (6)
Lycopene
Lycopene is an antioxidant that is found in tomatoes and tomato-based foods. This type of antioxidant is a form of vitamin A that has free radical scavenging properties. A diet rich in lycopene has been linked to better cardiovascular health and lower instances of cancer. (7)
Lutein
Lutein is a carotenoid and one of the antioxidant vitamins that is essential for good vision and to protect against age-related macular degeneration. Some studies have found that lutein helps prevent the damaging effects of oxidative stress in the retina which, in turn, protects against eye disease. (8)
Zeaxanthin
Zeaxanthin is another antioxidant that, together with lutein, helps protect your vision from the harm that free radicals can do. Zeaxanthin is also a carotenoid and gives foods such as carrots, salmon, and eggs their orange or yellow color. (9)
Bioflavonoids
Natural antioxidant substances called bioflavonoids are found in many vegetables, plants, tea, and wine. Flavonoids cover many types of antioxidants that include phytoestrogens, flavanols, flavones, anthocyanins, catechins, and polyphenols. Studies have shown that flavonoids have free radical scavenging activity to help lower inflammation, boost cognitive function, keep bones healthy, and improve cardiovascular health. (10)
Manganese
Foods containing manganese can help to protect the integrity of your cells as it combats oxidative damage. (11)
Selenium
One important antioxidant mineral is selenium because it helps prevent oxidative stress which can damage DNA in cells. Making sure your diet includes selenium-rich foods such as Brazil nuts, chicken, and seafood, can help protect against various chronic diseases. (12)
Coenzyme Q10
Coenzyme Q10 (CoQ10) is an important antioxidant that reduces inflammation and neutralizes free radical activity. Studies have shown that CoQ10 may be a beneficial antioxidant supplement to help recover better after surgery. CoQ10 antioxidant is also important for good dental health. (13, 14)
Alpha lipoic acid (ALA)
Another important antioxidant found in foods such as spinach, tomatoes, carrots, beets, and broccoli is alpha lipoic acid. This free radical scavenger helps to protect against neurodegenerative diseases, diabetes, cataracts, and age-related illnesses. (15, 16)
Benefits of Antioxidants
Antioxidant foods are good for helping to protect your health from the negative effects of free radicals.
Researchers explain that a buildup of free radicals can lead to oxidative stress. Free radicals result as a normal part of cell metabolism. However, environmental factors such as pollution, radiation, and cigarette smoke can add to the problem of oxidative stress. (17)
The benefits of antioxidants are that they help protect your body from degenerative and chronic illnesses caused by oxidative stress. Reducing the number of free radicals can help to prevent diseases such as Alzheimer’s disease, cardiovascular disease, autoimmune disorders, cancer, and vision problems. (17)
Let’s look in more detail at the many benefits that you get from enjoying a diet rich in antioxidants.
Promote Good Cardiovascular Health
Vitamin C is a powerful antioxidant that has a number of benefits for your heart and vascular system.
A 2015 study found that a high intake of antioxidant foods rich in vitamin C is linked with lower instances of heart disease. (18)
Another way that antioxidants protect your heart’s health is that they help lower blood pressure. Studies have shown that free radical scavengers such as vitamin A, vitamin C, vitamin E, flavonoids, CoQ10, and ALA all have a hypotensive (blood pressure lowering) effect. (19)
These findings are in harmony with the American Heart Association’s recommendation to increase fruits and vegetable intake to help control high blood pressure. (20)
Learn more about the foods you should include in a heart-healthy diet to help lower your cardiovascular disease risk.
Boost Cognitive Health
Antioxidant vitamins and minerals are also essential to keep your brain healthy and help prevent age-related cognitive illnesses.
Some reports indicate that foods rich in antioxidants can act as natural anti-depressants. For example, addressing deficiencies of vitamins A, C, and E can help to improve symptoms of stress-related mental disorders. Antioxidant supplements may help improve the symptoms in some people of general panic disorder. (21)
Other vitamin-rich foods and antioxidant drinks such as tea can also help to improve cognitive health. Carotenoids, flavonoids, and vitamins C and E all help to boot brain health. Although some studies are inconclusive, there is evidence that including antioxidant foods in your diet has a positive effect on mental health. (22)
As well as antioxidants helping boost your brain power, learn about ways to increase dopamine naturally to help improve mood and improve feelings of depression.
Strengthen Your Immune System
Reducing the effects of reactive oxygen species (ROS) helps limit the stress they cause on your immune system. This means that a diet rich in antioxidant foods can help ward off infections or even prevent them in the first place.
Researchers say that you need to maintain a fine balance between free radicals and antioxidants to maintain your body’s immune defenses. Antioxidant compounds such as selenium, vitamins C and A, beta-carotene, and CoQ10 have strong antioxidant activity. (23)
Getting the required number of antioxidants is necessary for a healthy immune response in the body and to prevent a number of autoimmune conditions. Antioxidants work to protect your cells from damage by limiting the damaging effect of free radicals.
Boosting your immunity with the right antioxidants can help prevent diseases such as cancer, rheumatoid arthritis, Parkinson’s disease, and other inflammation-related conditions. (23)
However, researchers also warn about taking too many antioxidant supplements. An excess intake of antioxidants can have a pro-oxidant effect and cause certain diseases. (23)
Find out about some lifestyle changes that can help boost your immune system’s health almost immediately. Also learn about foods, vitamins and supplements for boosting the immune system.
Aid in Cancer Prevention
Because antioxidants kill off free radicals and help prevent cellular damage, antioxidants are important for protection against cancer.
The National Cancer Institute reports that free radical activity may play a part in the development of certain cancers. The body uses antioxidants from dietary sources to neutralize the effect of free radicals. Fruits, vegetables, and grains are all good antioxidant foods. (24)
Some studies show that there is no conclusive evidence on the benefits of taking antioxidant supplements to prevent chronic diseases such as cancer. (24) However, there are reports indicating that some types of antioxidants can help limit excessive ROS during chemotherapy treatments. For example, selenium, vitamin C, vitamin E, and carotenoids may help slow or prevent the spread of certain cancerous cells. (25, 26)
If you are undergoing a treatment for cancer, it is important to speak to your doctor on the use of antioxidants in conjunction with cancer therapy.
Learn more about the best foods to eat regularly to help lower your risk of cancer.
Necessary for Good Vision
Lutein, zeaxanthin, beta-carotene, and vitamin C are the best antioxidants to prevent oxidative stress-related eyesight problems.
A 2017 analysis on the role of antioxidants and good vision found that consuming antioxidant foods can lower your risk of cataracts, age-related macular degeneration, and glaucoma. It was found that having a diet rich in fruits and vegetables and limiting red meat helps protect against age-related vision problems. (27)
The American Optometric Association recommends getting 5 servings of fruits and vegetables every day to help lower the effects of oxidative stress on your eyesight. Also, 2 servings of nuts can help you get enough vitamin E antioxidants. (28)
Further reading: Proven foods and vitamins to improve and protect your eyesight.
May Reduce the Risk of Rheumatoid Arthritis
Consuming plenty of antioxidant foods help to lower the stress load caused by oxidation and may prevent rheumatoid arthritis.
Because antioxidants reduce inflammation by neutralizing reactive oxygen species, they may be useful in managing rheumatoid arthritis.
One small open pilot study involving 8 women found that increasing antioxidant levels helped to reduce the symptoms of rheumatoid arthritis. The high serum levels of antioxidants also helped lower oxidative stress markers. (29)
However, results from a large number of studies didn’t find a link between reduced risk of rheumatoid arthritis and increasing antioxidant intake. The researchers acknowledged this could be due to the fact that many other factors are involved in the development of autoimmune conditions. (30)
Learn about many of the foods with high antioxidant levels that are good for lowering inflammation naturally. Also learn about the best foods to consume if you have arthritis.
Promote Good Liver and Kidney Health
Increasing the number of antioxidant-rich foods in your diet also benefits your liver and kidney function.
Antioxidants are necessary to prevent free radicals in your liver causing oxidative stress. Dietary antioxidants help keep the oxidative/antioxidative balance and may prevent or help treat liver-related diseases. (31)
One study highlighted that the powerful antioxidant vitamin C can help improve kidney health. Kidney disease can increase free radical levels in the body. Increasing levels of vitamin C where there is a deficiency can help to repair oxidative damage in the kidneys. (32).
It is good to remember that researchers say that the role of oxidative stress in liver and kidney disease is complicated. However, there is enough evidence to suggest that antioxidants play a crucial role in maintaining organ health. (33, 34)
One way to prevent an increase of oxidative stress in your body is to avoid dangerous habits that damage your liver. You can also include in your diet some of the best scientifically proven foods to cleanse your liver, as well as these proven foods for healthy kidneys.
Help Keep Your Skin Healthy
One of the health benefits of antioxidants is that they keep your skin looking healthy and protect against the visible signs of aging.
Researchers have found that free radicals can damage skin cells and collagen structure. This can lead to photoaging caused by repeated exposure to ultraviolet radiation, which causes fine lines and wrinkles, and even skin cancer. Antioxidants such as vitamins A, C, and E as well as CoQ10, and alpha-lipoic acid limit oxidative stress and have many skin benefits. (35)
One 2014 review found that increasing foods loaded with antioxidants such as vitamin C and E can help protect against sun damage. Carotenoid-rich diets also provide protection against free radical damage. (36)
Antioxidants can benefit your skin if you suffer from acne. Some studies found that people with acne often have vitamin A, vitamin E, and selenium deficiencies. There is some evidence that a diet high in antioxidants can help improve the symptoms of acne. (37, 38)
Further reading: Proven hair, skin, and nail vitamins and foods that really work (evidence based).
May Help Delay Age-Related Diseases
Adequate intake of antioxidants in your diet can help to prevent various diseases that are related to the aging process.
Scientists have found that consuming fruits and veggies that are packed with antioxidants may delay the aging process. Antioxidants such as polyphenols may play a role in preventing chronic diseases such as cardiovascular disease, neurodegenerative disease, and cancer. (39)
The reason why antioxidants benefit the aging process is that they help to limit the effect of free radical activity.
Foods High in Antioxidants (Antioxidant Foods)
How can you know which foods are packed with antioxidants and are good for your health?
There are a number of tests that scientists use to determine the antioxidant effect of certain foods.
One way to check for the antioxidant content in food is to test how well the specific food neutralizes free radicals. This is called the FRAP test, or, Ferric Reducing Ability of Plasma. Results from FRAP tests are measured in millimoles (mmol) per liter or gram. (40)
Other tests for antioxidant levels in food and drink include the Oxygen Radical Absorbance Capacity (ORAC) test or the Trolox-Equivalent Antioxidant Capacity (TEAC). (41)
Generally, a higher result in these tests means a higher antioxidant activity of the food or beverage.
Fruits High in Antioxidants
Fresh fruits are excellent sources of antioxidants due to their high vitamin content.
Which are the best fruits to consume to increase antioxidant levels and scavenge free radicals?
Citrus fruits
Citrus fruits are high in antioxidants and can help to boost your immunity. Citrus fruits such as lemons, oranges, and limes may contain over 170 different types of antioxidants. Vitamin A, vitamin C, flavonoids, and limonoids all combine to make citrus fruits high in antioxidants. (42)
Berries
Berries are an excellent source of vitamins such as vitamin C and therefore are powerful antioxidants.
The berries that score highest in the FRAP test are black chokeberries, raspberries, and blackberries. Other types of berries that are very good for your health include blueberries, cranberries, and blackcurrants. (43)
Related: List of Different Kinds of Berries and Their Benefits
Vegetables High in Antioxidants
Along with fruits, vegetables are one of the best sources of antioxidants as they contain vitamins, phytochemical, and bioactive compounds.
Studies have shown that some of the vegetables highest in antioxidants are curly kale, artichokes, red beets, and red cabbage. (44)
Although technically a fruit but typically included as a vegetable in the culinary world, tomatoes are an important antioxidant food as they are a rich source of lycopene. One study found that combining tomato products with olive oil significantly increased the FRAP results and, therefore, the antioxidant activity. (45, 46)
Another important antioxidant vegetable to include in your diet are carrots. Carrots are a rich source of beta-carotene and help to increase vitamin A levels in your body. Also purple sweet potato is rich in antioxidants and have 2.5 times more antioxidants (anthocyanins) than their orange-fleshed counterparts. (58)
Nuts High in Antioxidants
Nuts are important sources of vitamin E and are good for your overall health because they contain healthy fats.
Some of the best nuts to consume for their high antioxidant levels are walnuts, chestnuts, hazelnuts, and almonds. Even the humble peanut (which is actually a legume) has a good antioxidant content. (44)
When it comes to ORAC scores, pecans scored the highest in relation to antioxidant capacity. Pecans have the highest flavonoid content from nuts with 34 mg per 100 g. (45)
Brazil nuts are also important antioxidants as they are the best source of the antioxidant selenium. In fact, just one Brazil nut gives you more than enough of your daily selenium requirements. (46)
Legumes High in Antioxidants
Foods such as peas, beans, and lentils are good for you because they contain antioxidants and a lot of fiber.
Some studies show that legumes which score the highest in FRAP assays are generally darker in color. So, lentils, black peas, red beans are the best type of legumes for their good antioxidant activity. (47)
Another way to benefit from the antioxidants in legumes is to consume sprouted peas or beans. Research has shown that germinated grains contain many types of antioxidants that are good for your health. (48)
Antioxidant drinks
Including antioxidant-rich drinks in your diet is another great way to boost your health and help prevent various diseases.
Green tea
One of the best and healthiest antioxidant drinks to consume regularly is green tea. FRAP assays have found that green tea contains more antioxidants than black tea or oolong tea. The radical scavenging activity of green tea is due to catechin compounds. (49)
Green tea is also good to drink to limit the harm radical oxygen species can do to your dental health. (50)
You can also buy green tea powder as a natural supplement to help boost your immune system.
Further reading: Proven health benefits of green tea: weight loss, skin, and more.
Red wine
When consumed in moderation, red wine is an antioxidant drink that has benefits for your heart health. Studies have shown that red wine is a potent antioxidant beverage due to high levels of polyphenols, resveratrol, and quercetin. A glass of red wine can help to decrease oxidative stress and reduce inflammation in your body. (51)
There are on average 2.5 mmol of antioxidants in every 100 ml of red wine which puts red wine in the list of top antioxidant drinks. (43)
White wine and grape juice are also drinks with good levels of antioxidants. (52)
Pomegranate juice
The best antioxidant drink is pomegranate juice as this scores the highest in FRAP tests for antioxidant levels. In fact, studies have shown that the antioxidant content of pomegranate juice is comparable to that in human breast milk. (35, 43)
Further reading: Proven health benefits of pomegranate (fruit, juice, seeds).
Antioxidant Herbs
One way to increase the antioxidant content in foods you prepare is to add certain herbs and spices that score well on the FRAP assay.
Turmeric
The antioxidant compound curcumin in turmeric gives this spice its vibrant color and health benefits. Curcumin helps protect cells from DNA damage and has an anti-inflammatory effect in the body. Taking curcumin can help prevent inflammatory-related and oxidative related diseases. (53)
Read more about the proven medicinal health benefits of turmeric and curcumin and in this article, and whether cooking really destroys the health properties of turmeric.
Ginger
Ginger contains gingerols that have a powerful antioxidant capacity to help keep you healthy. Including ginger in your diet can increase antioxidant enzymes and help reduce inflammation. In fact, some studies have shown that ginger is just as good as vitamin C for its antioxidant potential. (54)
Dried ginger has up to 24 mmol of antioxidants per 100 g of powder. (43)
Read more about the proven health benefits of ginger root and ginger tea, and is ginger best used raw or powdered and are any of its health benefits lost during the cooking process.
Cinnamon
Cinnamon contains a number of antioxidants that help reduce the effects of oxidation. (55)
The FRAP score of cinnamon is fairly impressive with up 140 mmol of antioxidants in every 100 grams of dried cinnamon. (43)
Learn about science based benefits of cinnamon (tea, powder) and which type of cinnamon is the best to use for its health benefits in this article.
Other herbs with good antioxidant activity include clove, oregano, rosemary, thyme, and peppermint. (43)
Dark Chocolate
Dark chocolate is a good source of antioxidants that are good for your cardiovascular system, and has other scientifically proven health benefits.
Studies using the FRAP analysis have shown that dark chocolate contains up to 15 mmol per 100 g. This means that dark chocolate has better antioxidant activity than some berries and fresh fruits. (43)
How Cooking Affects Antioxidants in Foods
A study published on 2009 in the International Journal of Food Sciences and Nutrition checked how cooking methods affect the total antioxidant capacity (TAC) in vegetables that are commonly cooked before consumption.
The study found that boiling generally resulted in positive TAC changes, whereas pan-frying had a general negative effect on the TAC. However deep-frying resulted in a TAC increase of potato, artichoke and aubergine but a TAC reduction of mushroom and onion. (59)
However heat can also result in loss of some nutrients. For example: A study from the University of Arkansas found that cooked, pureed carrots contain more phenolic acids and total carotenoids than raw carrots, (60, 61) but as for vitamin C which is heat sensitive, a study from 2018 found that steaming and microwaving carrots retained higher concentrations of vitamin C than boiling them. The researchers concluded that using minimal cooking water and cooking for shorter time periods should result in higher vitamin C retention. (62)
Antioxidants Risks and Side Effects
When it comes to improving your health status by increasing antioxidants, it’s good to remember that more doesn’t always mean better.
In general, you should get enough antioxidants for good health through a healthy diet. You should try to consume adequate amounts of food rich in antioxidants. This means getting plenty of fruits and vegetables every day. (56)
It is important to remember that taking too many antioxidant supplements may even have a negative effect on your health. Taking large amounts of antioxidants such as vitamin A, E, and beta-carotene could exacerbate oxidative stress in your body. (57)
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