There’s a lot of talk about the benefits of antioxidants, and for good reason. Many experts suggest they protect us from premature aging, heart disease, cancer, and possibly depression and anxiety.
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What are antioxidants?
You have probably heard of antioxidants but might not know what they are or why you need them. Selenium, vitamin C, vitamin E, and beta-carotene, and phytochemicals are antioxidants found in plants. The body also makes its own antioxidants (e.g., coenzyme Q10, glutathione), but the level of intracellular antioxidants depends almost entirely on the food we eat.
Antioxidants are compounds found in food and produced in the body that prevent or delay damage to our cells.
Antioxidants are water-soluble or fat-soluble. They reside in parts of our cells that are watery or oily (fat). For example, vitamin-C is water-soluble and is found in the watery-filled compartments of the body. Vitamin-E is fat-soluble and can be found in our cells’ lipid-rich (fat-rich) areas, like the cell membrane.
Even though they work in different areas of the body, our antioxidants communicate and support one another. Think of them as good friends or co-workers. Antioxidants work together like a fantastic team that defends against destructive unstable molecules called free radicals.
The health benefits
Decades of research suggest people who eat more generous amounts of antioxidant-rich food have increased protection against disease. Part of this protection is related to our antioxidant’s ability to fight free radicals and reduce oxidative stress.
#1) Fight free radicals
Antioxidants help protect our cells from damage caused by free radicals. So, what are free radicals? They are highly reactive, unstable molecules that are trying to become stable. They virtually steal what they do not have (an electron) to make themselves stable. They attack a molecule that is close by, such as a lipid or protein, and steal an electron.
Now the “robbed” molecule becomes a free radical and attacks another nearby molecule creating a chain reaction. All this theft creates damage to our cells and DNA. Enough damage and we end up with premature aging and diseases like diabetes, heart disease, and cancer.
We cannot escape free radicals. They are created naturally when we breathe, exercise, and convert food to energy. There are also environmental sources of free radicals such as cigarette smoke, air pollution, and sunlight. We, therefore, need an abundance of antioxidants to stop all these thieves.
Antioxidants protect our cells and DNA by giving free radicals what they are missing (an electron) without becoming radicals themselves.
When vitamin E donates an electron to a free radical, it helps stop that chain reaction of damage, but now the vitamin E needs a little support to stay active. Vitamin C comes to the rescue and restores vitamin E to its active state.
We need an abundance of dietary antioxidants to diminish free radical damage. We also want a variety of them. Different antioxidants defend against various types of free radicals. Taking a vitamin C supplement alone won’t quench the many kinds of free radicals. The table below presents a few examples of this.
|Free Radical Producer||Protective Antioxidant|
|Air Pollution||Vitamins C, E, beta-carotene, green tea extracts|
|Ionizing (x-ray) and Non-ionizing (sunlight) Radiation||Vitamins C, E, selenium, lutein, lycopene, green tee polyphenols, curcumin|
|Pesticides||Vitamins A, C, E, selenium, lycopene, EGCG, quercetin|
|Exercise||Endogenous free-radical defense systems|
Table Source: 
The goal is not to eradicate free radicals, as they do have a purpose. For example, they help the immune system fight infections. The problem is when there are too many free radicals for our antioxidant team to neutralize. If fruit and vegetable intake is low, as it is in most Americans, we do not have the resources to defend against these radicals, leading to harmful oxidative stress.
#2) Reduce oxidative stress
Oxidative stress occurs when we lack balance and it can damage our body and brain. It’s associated with cardiovascular disease (atherosclerosis), cancer, diabetes, age-related macular degeneration, neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease), autoimmune diseases (systemic lupus), mental stress, depression, and memory loss [2, 3, 4]. And, increased stress, mood disorders, and chronic disease increase oxidative stress. A vicious cycle occurs.
When we don’t have enough antioxidants, free radicals build up and cause oxidative stress.
Oxidative stress is also associated with inflammation. Inflammation is a key driver in chronic diseases like cardiovascular disease and mood disorders like depression. There appears to be a bidirectional relationship here – oxidative stress increases inflammation, and inflammation increases free radicals leading to oxidative stress.
Antioxidants help reduce inflammation. Vitamin C, for example, has been shown to reduce c-reactive protein (CRP). Elevated CRP is associated with increased cardiovascular disease. Vitamin C was found in one study to reduce CRP by 25% in those with elevated CRP. This is amazing and comparable to CRP reductions seen with statin medication .
The body does its best to stop oxidative stress. It will produce an arsenal of antioxidants, but the body’s internal antioxidant system alone is not enough. The diet must be rich in plants to reduce the constant bombardment of free radicals successfully.
#3) Mental heath
The brain is especially susceptible to free radicals. The hippocampus, an area of the brain involved in learning and memory, takes a big hit. Oxidative stress not only kills cells in the hippocampus, but it also reduces neurogenesis (growth of new brain cells).
A smaller hippocampus reduces learning and memory and is associated with mood disorders like depression.
There is growing research showing a connection between a deficient antioxidant defense system, oxidative stress, and mood disorders . The use of antioxidants as an adjunctive treatment of neuropsychiatric disorders is promising. Some researchers believe it’s possible to reduce depression and anxiety symptoms by consuming foods rich in antioxidants .
A recent study found lower levels of vitamins A, C, and E in people with anxiety disorder and depression. After receiving 6-weeks of dietary supplementation, blood levels of antioxidants increased, and depression and anxiety symptoms were reduced . Another study found an association between total carotenoids (particularly beta-carotene and lutein, plus zeaxanthins) and reduced depression .
Caution is advised with high doses of antioxidants, as seen with dietary supplementation. This could increase oxidation (prooxidation) and interfere with some of the protective functions of free radicals . It’s always best to consult with your health care provider before making any dietary changes.
#4) Brain health
The loss of neurons due to oxidative stress is linked to the development of neurodegenerative disorders such as Alzheimer’s disease. Researchers have been examining the effects of antioxidant therapies for their neuroprotective effects.
Oxidative stress damages and kills neurons (brain cells).
Several studies have shown an association between neurodegenerative disorders (e.g., Alzheimer’s, Huntington’s diseases, amyotrophic sclerosis) and antioxidant vitamin deficiency. One of these studies found a reduced risk of cognitive decline in people 65 years of age and older when given vitamin C and/or vitamin E .
A well-respected clinical trial called The Physicians’ Health Study II, gave a placebo or a 50 mg beta-carotene supplement to nearly 6,000 men over 65 years of age. The researchers found cognitive benefits in the men who supplemented with beta-carotene for at least 15 years .
#5) Support healthy aging
Aging, oxidative stress, and inflammation are closely related. There is a theory called oxi-inflamm-aging that has been proposed. The theory suggests that chronic oxidative stress alters our regulatory systems, such as nervous, endocrine, and immune systems, as we age. Activation of the immune system leads to an inflammatory state, which creates a vicious circle.
Chronic oxidative stress and inflammation incite one another and subsequently increase age-related disease and mortality .
Researchers are also looking at cellular aging as the root cause of diseases associated with age, like heart disease and cancer. Scientists can assess cellular aging by measuring telomeres. Many studies have shown an association between shorter telomeres, aging, and poor health.
So, what are telomeres? You might think of them like the plastic end of a shoelace that protects the lace. Similarly, telomeres protect the ends of our chromosomes that contain our DNA. Every time our cells divide, the telomeres get shorter. The telomeres wear down, reducing their ability to protect our DNA [12, 13]. Damage to DNA increases the risk of premature aging and disease.
Antioxidants help protect our DNA. Part of this protection may be due to the way antioxidants affect telomeres. This is excellent news. We have some control here. Our lifestyle habits such as a healthy diet and exercise can slow telomere shortening. Antioxidants may help preserve our telomeres because they reduce oxidative stress and inflammation, both of which are associated with telomere shortening [14, 13, 15].
Eating plenty of antioxidant-rich food may delay age-related diseases by reducing oxidative stress and inflammation, thereby protecting telomere integrity and reducing DNA damage.
#6) Healthy eyes
Research has shown the protective benefits of antioxidants against age-related eye disease (AMD). AMD occurs as we age and damages the macula of the eye. AMD is a leading cause of vision loss in people 50 years of age and older. It does not cause complete blindness, but it damages our central vision. We need our central vision for things like reading, driving, recognizing faces, and doing close-up work such as cooking .
Several large clinical trials led by the National Eye Institute and the NIH (National Institutes for Health) found beneficial effects of antioxidant supplements. A six-year clinical trial found that a combination of antioxidants (vitamin C, 500 mg; vitamin E, 400 IU; and beta carotene, 15 mg, 80 mg of zinc) reduced the risk of developing AMD by 25 percent. The antioxidants used alone reduced risk by 17 percent. Another study found that lutein and zeaxanthin supplementation protected vision in participants with late AMD for up to five years [17, 18, 19].
What foods are high in antioxidant?
Foods rich in vitamin E, vitamin C, beta carotene, selenium, and phytochemicals provide antioxidants.
There are several methods used to assess antioxidant content in food. ORAC (oxygen radical absorbance capacity) was once considered the gold standard but is rarely used today. FRAP (ferric reducing ability of plasma) has emerged as one of the best tests to measure antioxidant content by its ability to quench a specific free radical . Berries, leafy greens, nuts, dark chocolate, beans, and cruciferous vegetables have high FRAP values, meaning they are high in antioxidants.
The table below presents foods rich in antioxidant vitamins and minerals.
|Vitamin C||Citrus fruits (oranges, grapefruit), strawberries, sweet potatoes, tomatoes, broccoli, cauliflower, potatoes|
|Vitamin E||Vegetable oils, nuts, peanut butter, seeds, whole-grains, wheat germ, fortified cereals|
|Carotenoids||Sweet potatoes, carrots, mangoes, apricots, tomatoes, spinach, Brussels sprouts, broccoli, winter squash|
|Selenium||Nuts, whole grains, seafood, meat|
In addition to vitamin C, E, beta-carotene, and selenium, many phytochemicals act as antioxidants.
To keep it simple, look for vibrantly colored plants. Healthy plant-based foods that are vibrant in color tend to have high FRAP scores.
Green. Green plants provide us with many phytonutrients including lutein and zeaxanthin (green leafy vegetables), isoflavones (soy), isothiocyanate (broccoli, kale, Brussel’s sprouts), EGCG (green tea), quercetin (green chili peppers), and flavones (fresh oregano, fresh parsley, fresh peppermint) .
Red. Red-colored plants provide us with lycopene (tomatoes), flavonoids (red delicious apple with skin), ellagic acid (strawberries, raspberries), isothiocyanate (red cabbage), anthocyanidins (radish, red cabbage, red wine) .
Blue/Purple. Blue and purple colored plants provide resveratrol (grapes, grape juice, wine) and anthocyanidins (blueberries, blackberries, purple grapes) .
Adding antioxidants to your diet
There are no blanket recommendations for antioxidant intake. A diet that includes vegetables, fruits, whole grains, nuts, seeds, herbs, spices, and tea will provide plenty of these nutrients .
The simplest way to get your antioxidants is to fill half your plate with fruits and vegetables for every meal. And eat a rainbow of colors every day.
If you follow the 2015-2020 Dietary Guidelines for Americans, you will most likely have a diet rich in antioxidants. The guidelines recommend 2 cups of fruit and 2.5 cups of vegetables per day for people requiring 2,000 calories per day.
|Food Group||2,000 Calorie Diet|
|Vegetables||2½ cups per day|
|— Dark-green vegetables||1½ cups per week|
|— Red and orange vegetables||5½ cups per week|
|— Legumes (beans and peas)||1½ cups per week|
|— Starchy vegetables||5 cups per week|
|— Other vegetables||4 cups per week|
|Fruits||2 cup per day|
|Grains||6 oz per day (½ from whole grains)|
|Nuts seeds, soy products||5 oz per week|
Table Source: 23
Are there any cons?
Antioxidants from food do not raise concern. However, high dose dietary supplements are a concern for some people. Antioxidants in high doses may become prooxidants . They can increase free radicals, oxidative stress, and harm health.
High amounts of beta-carotene and vitamin E from supplements have been shown to increase lung cancer risk in smokers. Research has also seen a greater risk of prostate cancer and stroke with high dose vitamin E supplements.
High doses of antioxidants can also interfere with certain medications. Vitamin E supplements, for example, can interfere with blood thinners (e.g., warfarin) and increase the risk of bleeding [24, 25, 26]. To prevent complications, it’s best to consult with your healthcare provider before adding any dietary supplements.
Risks of low antioxidant intake
A diet low in antioxidant-rich fruits and vegetables is associated with a greater risk of diseases, including cancer, heart disease, stroke, and cataracts. Eating enough plants is critically important in providing us with the antioxidants we need to ward off illness.
Take home message
Antioxidants are compounds found primarily in plants that protect us from damaging free radicals and oxidative stress. Decades of research suggest a diet full of antioxidant-rich foods protects us from disease. Foods rich in vitamin E, vitamin C, beta carotene, selenium, and phytochemicals provide us with antioxidants. A simple strategy to increase your antioxidants is to eat an abundance of colorful plants every day.