Debunking The Truth About Antioxidants and Their Health Benefits

Introduction

Antioxidants have become intriguing substances within the scientific community due to their numerous advantages. Recently, there has been a growing focus on the role of naturally occurring phytochemicals in foods that may act as antioxidants within the human body. This interest has been fueled by popular literature that characterizes oxidants as detrimental and antioxidants as their beneficial counterparts.

In 2024, the global antioxidants market was valued at USD 4.84 billion. Projections indicate it will expand from USD 5.11 billion in 2025 to USD 7.64 billion by 2032. The Asia Pacific region led the antioxidants market, holding a significant market share of 43.8%. (Source: https://www.fortunebusinessinsights.com/industry-reports/food-antioxidants-market-100789).

While the popularity of antioxidants is on the rise, it is crucial to balance their advantages and possible risks. Over-reliance on antioxidant supplements or excessive intake can lead to an “antioxidant paradox,” where antioxidants may promote rather than prevent damage.

This review provides a clear and concise exploration of oxidative stress, the different types of antioxidants, and the strengths and limitations they possess.

Oxidative Stress and Impact on Human Health

Definition

Oxidative stress is a condition resulting from an imbalance between the production of free radicals, i.e. reactive oxygen/nitrogen species (ROS/RNS), and the antioxidant defenses available within the cells. While ROS and RNS play a crucial role in normal cellular functions and the host’s defense mechanisms, their overproduction can lead to the development and worsening of several diseases.

Causes of Oxidative Stress

Factors that elevate the levels of free radicals in the body beyond healthy limits can result in oxidative stress. Common examples include unhealthy eating habits, smoking ,excessive alcohol consumption , sedentary lifestyle , exposure to chemicals, toxins like pesticides, heavy metals, food additives , environmental pollution , exposure to ultraviolet radiation from sunlight and other forms of radiation etc.

Detrimental Effect of Oxidative Stress

The disparity between the production and elimination of ROS and RNS leads to their excessive buildup. While ROS and RNS function as signaling molecules at normal physiological levels, their overabundance in oxidative environments can cause cellular harm by reacting adversely with proteins, lipids, and DNA, ultimately contributing to the development of numerous diseases associated with oxidative stress. It has been established that oxidative stress is linked to more than a hundred diseases. Oxidative stress plays a role in the initiation and advancement of several diseases, including diabetes, diabetic nephropathy, diabetic neuropathy, obesity and neurological disorders such as Alzheimer’s disease, amyotrophic lateral sclerosis, and Parkinson’s disease. It is also implicated in cardiovascular disease, cancer, hypertension and aging.

Understanding Antioxidants

Definition

The term “antioxidant” is not consistently well-defined. Broadly speaking, antioxidants are either natural or synthetic substances that work directly or indirectly to reduce the harm caused by free radicals.

Antioxidants Classification

Natural antioxidants

These compounds can either be synthesized within the body or obtained from dietary sources, particularly from a variety of foods such as fruits, vegetables, whole grains, nuts, seeds, herbs, and spices. Depending on their source, they can be classified into the following categories:

• Endogenous (produced within the body):
  • Enzymatic: Superoxide dismutase (SOD), Catalase, Glutathione peroxidase
  • Non-enzymatic: Glutathione, Uric acid, Coenzyme Q10, Alpha lipoic acid
• Exogenous (obtained from diet or supplements):
  • Vitamins: Vitamin C, Vitamin E, Vitamin A
  • Minerals: Selenium, Zinc, Copper, Manganese (co-factors for antioxidant enzymes)
  • Phytochemicals: Biflavonoids (Isoflavones, Flavanols, Flavanones, Quercetin, Anthocyanins), Carotenoids (Carotenes – beta-carotene, alpha-carotene, and lycopene and Xanthophylls-lutein, zeaxanthin, and beta-cryptoxanthin), Polyphenols (Curcumin, Resveratrol), Sulforaphane

Synthetic antioxidants

These are laboratory-synthesized chemical compounds designed to impede or slow the oxidation process. Butylated Hydroxyanisole (BHA), Butylated Hydroxytoluene (BHT), and Propyl Gallate (PG) are synthetic antioxidants mainly used to prevent spoilage and rancidity in various products, including food, packaging, cosmetics, and pharmaceuticals.

Dietary Sources of Antioxidants

For a diet rich in antioxidants, concentrate on eating a variety of colorful fruits, vegetables, whole grains, nuts, seeds, legumes, and spices, as these foods are outstanding sources of these beneficial compounds. The table below illustrates several important foods that are rich in antioxidants.

Health Effects of Antioxidants

In recent years, antioxidants, sourced from both dietary intake and pharmaceutical supplements, have garnered considerable attention from both researchers and the general public, with claims of their ability to protect against or treat various health conditions. Diseases that have been studied include cancer, cardiovascular disease, eye diseases associated with aging (macular degeneration and cataracts), and Alzheimer’s disease. 

A significant body of research has highlighted the importance of antioxidants in managing various health issues, including leukemia, thalassemia, ischemic stroke, hemodialysis, rheumatoid arthritis, critically ill individuals, postmenopausal women, schizophrenia, and depression.

The importance of antioxidants in addressing male infertility cannot be overstated, as medical studies have substantiated their efficacy and safety in the treatment of idiopathic male infertility. Recently, a range of antioxidants has been researched for their ability to prevent kidney stones resulting from hyperoxaluria. Additionally, there are reports suggesting that antioxidant supplementation may serve as a valuable adjunct therapy for patients suffering from stress-induced psychiatric disorders and generalized anxiety disorders.

Clinical Facts

• Cancer
  • The available evidence fails to endorse the belief that antioxidant supplements effectively prevent cancer.
  • In reality, research indicates that beta-carotene supplements may elevate the risk of lung cancer, especially among smokers and individuals exposed to asbestos.
• Cardiovascular disease
  • In 2022, the U.S. Preventive Services Task Force recommended against the use of beta-carotene and vitamin E supplements to prevent cardiovascular disease.
• Age-related macular degeneration
  • While antioxidant supplements have not been proven to prevent age-related macular degeneration in those without the disease
  • Certain formulations that include both antioxidants and zinc have been found to slow age-related macular degeneration progression.
• Athletes
  • Evidence suggests that athletes should be cautioned against the prolonged intake of high doses of antioxidants, as this may hinder the physiological adaptations of skeletal muscle and cardiovascular health that are induced by exercise.
• Interaction with Medications
  • Antioxidants may interfere with chemotherapy and radiation therapy in cancer treatment.
  • Some supplements, such as vitamin E, vitamin C, selenium, and beta-carotene, may also affect blood thinners or cholesterol medicines. 

Key Recommendations

Further Reading

• https://pmc.ncbi.nlm.nih.gov/articles/PMC9774584/#sec1-antioxidants-11-02388
• https://pmc.ncbi.nlm.nih.gov/articles/PMC7347016/#abstract1
• https://pmc.ncbi.nlm.nih.gov/articles/PMC5551541/#sec4
• https://pmc.ncbi.nlm.nih.gov/articles/PMC10669448/#sec1-biomedicines-11-02925
• https://www.ncbi.nlm.nih.gov/books/NBK541064
• https://www.mdpi.com/2076-3921/11/12/2388#
• https://www.sciencedirect.com/science/article/pii/S0974694313003733
• https://www.nccih.nih.gov/health/antioxidant-supplements-what-you-need-to-know
• https://pmc.ncbi.nlm.nih.gov/articles/PMC4665397
• https://www.sciencedirect.com/science/article/pii/S0002916523240915#ab0005
• https://www.sciencedirect.com/science/article/pii/S1728869X22000351#sec5
• https://pmc.ncbi.nlm.nih.gov/articles/PMC1173059/#