A Few Words About Antioxidants

Antioxidants are natural substances that protect our body’s cells from oxidative damage caused by free radicals – unstable chemical compounds that form naturally during metabolism or due to external factors such as air pollution, ultraviolet radiation, and smoking.

Antioxidants combat these reactive molecules, contributing to:

• Protecting cells from damage related to aging
• Preventing chronic diseases such as diabetes, cardiovascular diseases, cancer, and neurodegenerative disorders.

Incorporating a variety of antioxidants as part of a healthy and balanced diet can serve as a shield for our health and protect us from the occurrence of oxidative stress.

What Are the Main Antioxidants Found in Foods and Where Can We Find Them?

The term “antioxidant” does not refer to a single substance, but describes a large and diverse group of compounds that can neutralize free radicals and prevent cell damage.

The most common antioxidants found in foods are:

1. Vitamin C

Vitamin C is a water-soluble vitamin known for its strong antioxidant action. In fact, it is one of the most powerful antioxidant elements in nature.

2. Vitamin E

Vitamin E belongs to the family of fat-soluble vitamins and is known for its strong antioxidant properties, protecting our cells from damage caused by free radicals.

3. Carotenoids

Carotenoids are one of the main categories of natural pigments.

In fact, the characteristic red, yellow, and orange color of many familiar fruits and vegetables, such as tomatoes, peppers, carrots, apricots, etc., is attributed to the presence of these pigment compounds.

These compounds have strong antioxidant action, and due to this action, it has been hypothesized that they may contribute to the prevention of many chronic conditions, such as cardiovascular diseases, cancer, neurodegenerative disorders, etc., which are caused by oxidative stress.

4. Polyphenols

Polyphenols constitute a large and diverse group of chemical compounds found in plant foods and are known for their strong antioxidant properties.

To date, over 8000 phenolic compounds are known which are widely present in the plant kingdom.

In general, polyphenols are classified into four categories based on their chemical structure:

• Flavonoids (flavonols, flavones, flavanones, flavanols, anthocyanins, and isoflavones)
• Phenolic acids (hydroxybenzoic acid, gallic acid, caffeic acid, p-coumaric acid, salicylic acid)
• Stilbenes (resveratrol)
• Lignans.

5. Selenium

Selenium is an important trace element that has strong antioxidant action and plays a crucial role in the health of the organism.

Although needed in very small quantities, selenium is essential for the proper functioning of antioxidant enzymes that protect our cells from oxidation and damage caused by free radicals.

Specifically, selenium is a key component of glutathione peroxidase, one of the main antioxidant enzymes produced by our body to remove free radicals.

6. Phytochemical Compounds

Phytochemical compounds (or phytochemicals) are natural bioactive substances produced by plants and are mainly found in plant foods, such as fruits, vegetables, legumes, grains, nuts, spices, and herbs.

These compounds do not belong to nutrients, such as vitamins, proteins, or minerals, but play an important role in health, protecting the body from various diseases.

Some of these compounds have strong antioxidant action among other properties.

The category of phytochemical compounds includes: polyphenols, flavonoids, carotenoids, glucosinolates, terpenes, and others.

Where Are Antioxidants Found?

Antioxidants are found in many plant foods and beverages, some of which are extremely rich sources of these beneficial compounds.

The table below presents the main dietary sources of the above-mentioned antioxidants:

Antioxidants Found in Foods	Main Dietary Sources
Vitamin C	kiwi, orange, mandarin, strawberries, pepper, broccoli, cauliflower, lemon
Vitamin E	vegetable oils, such as sunflower oil, canola oil, olive oil, nuts and seeds like sunflower seeds, almonds, hazelnuts, all types of peanuts,
Carotenoids	carrot, sweet potatoes, kale, spinach, pumpkin, tomato, red pepper, mango
Polyphenols	Berries, such as strawberries, blackberries, blueberries, goji berries, tea, coffee, red wine, dark chocolate, olive oil, turmeric, ginger
Selenium	Brazil nuts, tuna, salmon, cod, shrimp, chicken, beef, egg
Phytochemical compounds	berries, citrus fruits, cruciferous vegetables (broccoli, cauliflower, cabbage), soy and soy products, turmeric, red wine, cocoa

 

What are the health benefits of antioxidants?

Antioxidants became widely known in the 1990s when scientists began to understand that oxidative stress might be involved in the early stages of atherosclerosis, the development of cancer, vision loss, and a range of other chronic health conditions.

Oxidative stress refers to the imbalance created when free radicals (ROS – Reactive Oxygen Species) exceed our body’s antioxidant systems.

Antioxidants are believed to protect the body from damage caused by free radicals and thus reduce the risk of various diseases.

Some of the health benefits of antioxidants include:

They contribute to cancer prevention

Several common antioxidants, such as polyphenols and carotenoids, have been shown to have anti-cancer properties.

For example, lycopene, which belongs to the carotenoid category, appears to have a protective effect against prostate cancer.

There are several studies in the literature that have reported that individuals who consume larger amounts of lycopene have a lower risk of developing prostate cancer compared to those with lower intake.[1]

Additionally, several pre-clinical studies, laboratory studies, and animal studies have highlighted the anti-cancer properties of polyphenols.[2]

However, we should emphasize that so far, the studies conducted have not been able to demonstrate that supplemental administration of antioxidants can offer benefits in cancer prevention.

What has been shown by many epidemiological studies is that a diet rich in fruits and vegetables, which are natural sources of antioxidants, may be associated with a reduced risk of developing cancer, such as upper digestive system cancers (e.g., oral cavity, esophagus) and possibly colorectal cancer.

The protective effect of high fruit and vegetable consumption may be attributed to the presence of antioxidant compounds as well as a variety of other nutrients and phytochemicals found in them, such as dietary fiber. It is this combination of beneficial components that makes foods more effective than individual supplements.

They Contribute to Heart Health

Given that oxidative stress is a recognized pathophysiological mechanism involved in the development of atherosclerosis, adequate intake of antioxidants as part of a healthy and balanced diet appears to be an effective way to improve our cardiovascular health.

Several epidemiological studies have highlighted the protective effect of antioxidants on heart health.

Specifically, a large observational study (National Health and Nutritional Examination Study – NHANES III), which included 13,293 participants followed for up to 18 years, concluded in its results that higher levels of α- and β-carotene were associated with lower mortality rates from cardiovascular diseases.[3]

Also, randomized clinical trials have shown that supplemental administration of polyphenols can improve key cardiovascular risk factors, such as “bad” cholesterol (LDL-C) levels and blood pressure.[4]

However, the usefulness of supplemental polyphenol administration in the prevention of cardiovascular diseases requires further investigation and analysis.

In any case, a diet rich in antioxidants when combined with an overall healthy lifestyle can significantly enhance heart health.

They contribute to eye health

Certain antioxidants, such as the carotenoids lutein and zeaxanthin, appear to play a crucial role in eye health.

These carotenoids are found in the macula of the eye, protecting the retina from oxidative damage caused by ultraviolet radiation, which can lead to eye disorders.

They contribute to good cognitive function

Antioxidants play an important role in cognitive function. [5]

Antioxidant compounds protect brain cells from oxidative damage caused by free radicals, which are thought to be responsible for cognitive decline and the development of neurodegenerative diseases such as Alzheimer’s disease.

Therefore, adequate intake of these compounds through diet can contribute to maintaining cognitive function as we age.

Should I take an antioxidant supplement?

Oxidative stress is known to contribute to the development of chronic diseases. However, this does not mean that taking antioxidants through supplements is always the appropriate solution. Especially when taken in large quantities, supplements can have negative effects on health.

What research says:

• Limited evidence: There is no strong evidence that antioxidant supplements have a significant effect on the prevention or management of chronic conditions.
• Negative effects: In some cases, high doses of antioxidants showed serious consequences:
  • Beta-carotene: Administration of high doses was associated with an increased risk of lung cancer and cardiovascular diseases, especially in high-risk individuals such as smokers.
  • Vitamin E: In high doses, it was associated with an increased risk of bleeding.
  • Vitamin C: Excessive doses can cause gastrointestinal problems (diarrhea, nausea, abdominal pain) and affect the effectiveness of anticancer treatments (e.g., chemotherapy, radiotherapy).

Prefer antioxidants through diet:

Adopting a healthy diet is the safest and most effective way to get the antioxidants you need. Choose foods such as:

• Fruits and vegetables
• Whole grains
• Legumes
• Plant oils (e.g., olive oil)
• Nuts and seeds

Foods provide a wide range of nutrients that work synergistically, offering significant health benefits.

Recommendations:

Before using any supplement:

• Consult your treating physician or dietitian to assess your needs.
• Focus on your diet, enhancing natural antioxidant intake through foods.

Conclusion

Antioxidants are molecules that fight free radicals in our body. This is particularly important as these compounds, when exceeding a “safety threshold” in the body, a condition called oxidative stress, begin to cause significant problems.

Specifically, oxidative stress has been linked to the onset of many chronic health conditions, such as diabetes, cardiovascular diseases, cancer, and neurodegenerative disorders.

For this reason, in recent years there has been increasing discussion about the valuable antioxidant components of our diet as a means to promote good health.

Incorporating antioxidants into our diet by increasing the consumption of a variety of plant foods, such as fruits, vegetables, whole grains, legumes, seeds, and nuts, is a natural and accessible way to promote our health.

Although antioxidant supplements may seem attractive, there is no strong evidence that they offer significant benefits in disease prevention and may cause undesirable effects, especially in high doses.

Therefore, it is better to prefer the intake of antioxidants through a healthy and balanced diet.

Bibliography

[1] Chen J, Song Y, Zhang L. Lycopene/tomato consumption and the risk of prostate cancer: a systematic review and meta-analysis of prospective studies. J Nutr Sci Vitaminol (Tokyo) 2013 59:213–223.

[2] Bhosale P, Ha S, Vetrivel P, Kim H, Kim S, Kim G. Functions of Polyphenols and Its Anticancer Properties in Biomedical Research: A Narrative Review. Transl Cancer Res. 2020 9(12):7619–7631. doi: 10.21037/tcr-20-2359.

[3] Shardell MD, Alley DE, Hicks GE, El-Kamary SS, Miller RR, Semba RD, et al. Low-Serum Carotenoid Concentrations and Carotenoid Interactions Predict Mortality in US Adults: The Third National Health and Nutrition Examination Survey. Nutrition Res. 2011 31:178–189. doi: 10.1016/j.nutres.2011.03.003.

[4] Potì F, Santi D, Spaggiari G, Zimetti F, Zanotti I. Polyphenol Health Effects on Cardiovascular and Neurodegenerative Disorders: A Review and Meta-Analysis. Int J Mol Sci. 2019 20(2):351. doi: 10.3390/ijms20020351.

[5] Nazzi C, Avenanti A, Battaglia S. The Involvement of Antioxidants in Cognitive Decline and Neurodegeneration: Mens Sana in Corpore Sano. Antioxidants (Basel). 2024 7;13(6):701. doi: 10.3390/antiox13060701.