Six out of every ten adults in the United States grapple with a chronic health condition, while four in ten contend with two or more. Among these conditions, the leading causes of disability and death are cardiovascular disease (CVD), chronic obstructive pulmonary disease (COPD), chronic kidney disease (CKD), Alzheimer’s disease, type 2 diabetes, and cancer. Underlying these conditions is oxidative stress. It is also involved in the aging process and implicated in age-associated functional losses such as sarcopenia and frailty. Functional medicine utilizes oxidative stress markers to assess the equilibrium between antioxidants and free radicals within the body and reveal any potential imbalances and health risks. 

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What is Oxidative Stress? 

Oxidative stress is the condition resulting from an imbalance between the production of free radicals and the body’s ability to neutralize them with antioxidants. Free radicals, or reactive oxygen species (ROS), are highly reactive molecules with one or more unpaired electron(s) formed when oxygen interacts with specific molecules. They serve bodily functions, including cellular signaling and fighting off pathogens. Antioxidants scavenge and neutralize free radicals to maintain cellular balance. When excessive production of free radicals or the antioxidant systems are overwhelmed, an imbalance ensues, giving rise to oxidative stress. Free radicals can trigger reactions, including lipid peroxidation, protein oxidation, and DNA damage, compromising cellular structures and functions. 

As cells experience cumulative damage from reactive oxygen species (ROS), they undergo cellular senescence, a process in which cells undergo irreversible growth arrest. This phenomenon contributes to the aging process by impairing cellular function and promoting the secretion of pro-inflammatory molecules. Oxidative stress also plays a central role in the pathogenesis of various NCDs, contributing to their initiation, progression, and complications. In cardiovascular diseases, oxidative stress promotes endothelial dysfunction, lipid peroxidation, and inflammation, all critical factors in the development of atherosclerosis. Chronic respiratory diseases, particularly COPD, exhibit heightened oxidative stress due to environmental factors like cigarette smoke, leading to lung inflammation and tissue damage. The progression of kidney disease is intricately linked to oxidative stress, as reactive oxygen species contribute to renal cell damage, inflammation, and fibrosis. 

Neurodegenerative diseases, such as Alzheimer's and Parkinson's, are characterized by oxidative damage to neurons and the accumulation of abnormal protein aggregates. Oxidative stress also plays a significant role in cancer, influencing genetic mutations, cell proliferation, and resistance to apoptosis. Additionally, in metabolic disorders like type 2 diabetes, there is a connection between oxidative stress and insulin resistance (IR), contributing to chronic low-grade inflammation.  

Common Causes of Oxidative Stress 

Free radicals can arise from sources within the body (endogenous) as well as from external sources (exogenous). Specific cellular processes naturally produce free radicals as byproducts. For instance, the electron transport chain in mitochondria, the process by which cells generate energy from adenosine triphosphate (ATP), is a significant endogenous source. Immune cells also release ROS to combat pathogens. At low or moderate levels, ROS benefits cellular responses and immune function. However, at high concentrations, they cause oxidative stress and subsequent damage to proteins, lipids, and DNA. When the body's antioxidant systems function optimally, they maintain a delicate balance with ROS, preventing excessive oxidative damage. However, poor function or an imbalance in these systems can lead to oxidative stress. A deficiency in essential nutrients, particularly antioxidants, obtained through the diet can compromise the body's ability to counteract ROS. Genetic variations can influence the efficiency of antioxidant enzymes and other defense mechanisms, impacting an individual's susceptibility to oxidative stress. The natural aging process is associated with a decline in the efficiency of antioxidant systems, making older individuals more susceptible to oxidative stress.

Exogenous sources of free radicals significantly contribute to increased oxidative stress. Smoking, alcohol consumption, exposure to heavy metals, and air pollution all increase free radical generation. Cooking methods, especially those involving high temperatures and fats, produce oxidative stress-inducing compounds. Ionizing radiation from sources like X-rays and nuclear materials directly damages cellular components, intensifying the production of free radicals. Certain drugs, like cyclosporine, tacrolimus, and gentamicin, can also increase oxidative stress. Ultraviolet (UV) light exposure increases the generation of ROS in the skin.

Types of Oxidative Stress Markers 

Several testing methods can be employed to assess oxidative stress levels. These tests help healthcare professionals understand the extent of oxidative damage and the balance between reactive oxygen species (ROS) and antioxidants. The oxidative damage that free radicals cause to lipids, proteins, and nucleic acids of the cells can be measured. Enzyme activity assays are utilized to assess the activity of antioxidant enzymes involved in the defense against ROS. These assays provide insights into the cellular capacity to neutralize harmful radicals and manage oxidative stress. Redox assays, using a free radical generating system and seeing how well the cells resist damage, measure the cells’ resistance to oxidative stress and their overall antioxidant capacity. Additionally, levels of important antioxidants can also be measured to assess the body’s antioxidant potential.

Testing for Oxidative Stress Markers 

Functional medicine labs assist in assessing and treating oxidative stress, providing an understanding of an individual's biochemical status. The information gathered from functional medicine labs is instrumental in tailoring targeted interventions to address specific imbalances and enhance antioxidant defense.

Oxidative Stress 2.0

The Oxidative Stress 2.0 by Genova Diagnostics is a urine test measuring levels of 8-hydroxy-2'-deoxyguanosine (8-OHdg) and lipid peroxides. 8-OHdG is a modified nucleoside and a biomarker for oxidative DNA damage. It is formed when ROS reacts with guanine, one of the DNA bases. Lipid peroxides, including malondialdehyde, are products of lipid peroxidation, a process initiated by the attack of ROS on cellular lipids. Urinary measurements of lipid peroxides and 8-OHdG, therefore, provide valuable information on the overall oxidative stress status in the body, offering a non-invasive and easily accessible means of assessing cellular damage caused by ROS. Elevated levels of these biomarkers indicate increased oxidative stress and potential cellular damage. 

Advanced Oxidative Stress

The Advanced Ox Stress test by Precision Point is a urine test that not only measures 8-OHdg, but also includes F2-isoprostane, reduced glutathione, oxidized glutathione, and total glutathione. F2-isoprostanes are prostaglandin-like compounds that are formed through the peroxidation of arachidonic acid, a polyunsaturated fatty acid present in cell membranes. Glutathione is a crucial antioxidant that plays a central role in the cellular defense against oxidative damage. GSH is the active, reduced form of glutathione that can actually neutralize ROS. GSH can become oxidized to GSSG during the process of neutralizing ROS. Assessing the levels of reduced glutathione, oxidized glutathione, and total glutathione, along with calculating the GSH/GSSG ratio, provides a comprehensive understanding of the redox status within cells (24). High levels of 8-OHdg and F2-isoprostane are associated with increased oxidative stress. A balanced and healthy redox state is characterized by a relatively high level of GSH and a low level of GSSG. A decrease in the GSH: GSSG ratio suggests an imbalance between antioxidants and oxidants, indicating increased oxidative stress.

Full Cellular Nutrition Assay

The Full Cellular Nutrition Assay by Cell Science Systems combines the Cellular Micronutrient Assay and the Redox/Antioxidant Protection Assay to provide a personalized assessment of a patient's nutritional needs. The body requires micronutrients to help fuel cellular metabolism and function. A cellular micronutrient assay (CMA) measures metabolic activity in cells after specific micronutrients are provided. The nutrients that enhance cellular function are reported as nutrient insufficiency. The Redox Assay is a measurement of the cells’ resistance to oxidative stress and its overall antioxidant capacity. A free radical generating system is added to cells, and their growth rates and/or damage are assessed. The cells’ ability to resist oxidative damage and prevent further damage to cells is determined and compared to that of the general population, creating a redox score. A low redox score is associated with an increased risk of oxidative stress. In the Antioxidant Protection Assay, single antioxidants are added to the patient’s cells in the presence of oxidative stress molecules. This process is repeated for each individual antioxidant. Specific antioxidants that support the recovery of patients’ cells from the effect of oxidative stress are reported as highly protective or protective. 

Organic Acids

The Organic Acids test (OAT) from Mosaic Diagnostics provides a comprehensive metabolic analysis, including information about yeast and bacteria levels, vitamins and minerals, oxidative stress, and neurotransmitters. Metabolic processes in the body produce organic acids as by-products, which can then be measured in the urine. The OAT includes markers that reflect the efficiency of mitochondrial function, such as citric acid cycle intermediates. High levels of these intermediates can indicate mitochondrial dysfunction, which is often associated with increased oxidative stress. It also measures specific markers related to oxidative stress, including products of lipid peroxidation. Elevated levels of these markers are suggestive of oxidative stress and damage. It provides information about the levels of essential nutrients and antioxidants, like glutathione and CoQ10. Deficiencies in these nutrients can compromise the body’s ability to manage oxidative stress effectively. Pyroglutamic acid is a metabolite of glutathione, and elevated values are most commonly caused by glutathione deficiency. 3-Hydroxy-3-methylglutaric Acid (HMG) is a precursor of coenzyme Q10, and an increase in urine HMG may indicate decreased synthesis of coenzyme Q10.

Micronutrients

The Micronutrient Test by SpectraCell Laboratories measures 31 vitamins, minerals, and other nutrients. Many nutrients, such as Vitamin E, vitamin C, selenium, and glutathione, play important roles as antioxidants in the body. Low levels can increase the risk of oxidative stress (25, 29).

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Interpreting Oxidative Stress Marker Results 

Interpreting oxidative stress markers requires an understanding of which type of marker is being evaluated. Elevated markers of oxidative damage, such as 8-OHdg, malondialdehyde, and F2-isoprostane, are associated with increased oxidative stress and damage. If directly measuring levels of antioxidants, such as Vitamin C, E, and glutathione, low levels are associated with deficiencies that can lower the body’s antioxidant potential and increase the risk of oxidative stress.  

When confronted with imbalanced levels, healthcare professionals should further investigate root causes, such as environmental exposures, nutritional deficiencies, or chronic inflammation. Depending on the causes, interventions may involve lifestyle modifications, dietary changes, or targeted antioxidant supplementation to mitigate oxidative stress and enhance overall well-being. The interpretation of these results is a crucial step in developing personalized strategies for health optimization and disease prevention. 

Managing Oxidative Stress 

A multifaceted approach that includes dietary adjustments, lifestyle modifications, and the strategic incorporation of antioxidants when needed can help to manage and prevent oxidative stress. Embracing this type of comprehensive strategy empowers individuals to take charge of their health, preventing the future health risks associated with oxidative stress. 

Nutrition

Western diets are characterized by excess consumption of saturated fats, refined sugars, and sodium and low consumption of plant-based fiber. People who regularly eat Western diets have been shown to have higher levels of oxidative stress and a greater risk of chronic disease. High-calorie, high-fat, and/or high-carbohydrate diets have been associated with increased oxidative stress. Fruits and vegetables, on the other hand, are rich in polyphenols and antioxidants that help to manage ROS. The Mediterranean diet is rich in vegetables, unrefined cereals, fruits, legumes, fish, olive oil, and nuts. Its higher intake of phytonutrients, as well as anti-inflammatory fats, such as omega-3 fatty acids in fish and nuts, make it a smart choice for preventing excess oxidative stress. Studies have shown that the Mediterranean diet promotes weight loss and prevents diseases like type 2 diabetes, stroke, CVD, cognitive impairment, Alzheimer’s disease, metabolic syndrome, and other chronic diseases associated with inflammation and oxidative stress (13).

Stress Management

Chronic stress triggers the activation of the neuroendocrine system, influencing a number of physiological responses and contributing to an elevation in oxidative stress. The sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenal (HPA) axis release catecholamines and glucocorticoids, like cortisol. Prolonged exposure to elevated levels of glucocorticoids can disrupt mitochondrial electron transport chain activity, leading to the formation of ROS. Catecholamines modulate the activity of enzymes responsible for redox in the cell, increasing mitochondrial dysfunction and ROS production. Implementing mind-body practices assists in restoring equilibrium to the nervous system and alleviating feelings of stress. Mind-body therapies are known to activate the parasympathetic nervous system, often referred to as the "rest and digest" system, which counterbalances the sympathetic nervous system's "fight or flight" response triggered during stress. Specific practices such as meditation, yoga, and diaphragmatic breathing have all been shown to help attenuate oxidative stress. 

Physical Activity

Regular physical activity improves antioxidant defenses and reduces lipid peroxidation. Engaging in moderate exercise and maintaining an active lifestyle not only aids in preventing oxidative stress but also serves as protection against cardiovascular disorders, type II diabetes, metabolic syndrome, and neurodegenerative conditions. Chronic exposure to high levels of ROS can be detrimental, overwhelming the body's antioxidant systems and causing cellular dysfunction. Therefore, excessive exercise can be harmful, especially for untrained individuals. However, through progressive training, cells can enhance their ability to manage a greater amount of ROS. Exercise-induced ROS generation triggers an upregulation in the activity of enzymatic antioxidants, thereby improving resistance to oxidative challenges. 

Antioxidants

The body's antioxidant system is a complex network of molecules and enzymes that work together to defend against oxidative stress. A balanced and varied diet helps to ensure the body has an abundant supply of nutrients that help to power the antioxidant system.

Glutathione is an intracellular antioxidant that also assists in detoxifying harmful substances that can increase oxidative stress. Additionally, it recycles other antioxidants in the body, such as vitamins C and E. It is a tripeptide molecule composed of three amino acids: cysteine, glutamic acid, and glycine. There are several foods that contain the thiol-rich compounds glutathione, NAC, and cysteine, including asparagus, avocado, cucumber, green beans, and spinach. N-acetyl cysteine (NAC) supplementation serves as a precursor for the synthesis of glutathione, or individuals can choose to directly supplement with liposomal glutathione. 

CoQ10 is an important cofactor for energy production in the mitochondria, a lipid antioxidant, and also regenerates vitamin E. CoQ10 is both produced endogenously and absorbed through the diet. Major dietary sources of CoQ10 include meats, fish, nuts, and soybeans. Many individuals can obtain sufficient amounts of CoQ10 through a balanced diet, but supplementation may be useful for individuals with particular health conditions, such as cardiovascular disease and diabetes (28, 31).

Vitamin E is a lipid-soluble antioxidant that helps to protect cell membranes from oxidative damage. Naturally occurring vitamin E exists in eight chemical forms (alpha-, beta-, gamma-, and delta-tocopherol and alpha-, beta-, gamma-, and delta-tocotrienol) that have varying levels of biological activity. Alpha-tocopherol is the most biologically active form of vitamin E. Nuts, seeds, and vegetable oils are among the best sources of alpha-tocopherol. Vitamin E supplements are available in either alpha-tocopherol form or as mixed tocopherols or tocotrienols. Evidence suggests that vitamin E can help inhibit the formation of oxidized low-density (LDL) cholesterol and blood clots and prevent cardiovascular disease (43).

Vitamin C is a water-soluble antioxidant that neutralizes free radicals in cellular fluids. Vitamin C is found in foods like bell peppers, citrus fruits, kiwi, and broccoli. Low levels of vitamin C have been associated with a number of conditions, including high blood pressure, gallbladder disease, stroke, cancers, and atherosclerosis. Vitamin C supplements come in various types and forms to suit different preferences and health needs. Ascorbic acid is the most common and basic form of vitamin C. Buffered forms, such as sodium ascorbate or calcium ascorbate, are available and may be more suitable for those who experience stomach upset with ascorbic acid. Ester-C, a combination of calcium ascorbate with vitamin C metabolites, is also easier on the stomach.

Selenium is a trace mineral that is incorporated into selenoproteins, some of which serve antioxidant functions. One important selenoprotein is glutathione peroxidase. Brazil nuts and seafood are great sources of selenium. It is also available as both a stand-alone supplement and as part of multivitamin complexes. Studies have shown that selenium helps lower products of oxidative stress, like malondialdehyde, and increases glutathione levels.

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Oxidative Stress Markers: Final Thoughts

Oxidative stress plays a significant role in the aging process and the development of many chronic, inflammatory diseases. Functional medicine testing provides individuals with an opportunity to identify the signs of oxidative stress and make proactive healthcare decisions to prevent future complications. Embracing healthy lifestyle changes, dietary modifications, and mindfulness practices can tip the scales in favor of balance, fortifying our defenses against oxidative stress.