Nikhil Prasad Fact checked by:Thailand medical News Team Aug 16, 2026 46 minutes ago
Oxidative Damage May Persist Long After Infection
Scientists studying long COVID have found striking evidence that the body can remain under prolonged oxidative stress months, and sometimes years, after the original coronavirus infection.
Long COVID patients showed substantially greater oxidative damage together with weakened antioxidant
defenses, even many months after their initial infection.
The study examined 85 people with post-COVID-19 syndrome, or long COVID, and compared them with 53 healthy controls. Researchers measured oxidative damage, antioxidant defenses and nitric oxide, a molecule important for healthy blood vessels. Most patients had experienced only mild COVID-19 initially, yet 61 percent had persistent symptoms lasting more than 12 months.
Fatigue was reported by 83.3 percent of patients, while 54.8 percent experienced headaches and 46.4 percent reported insomnia.
Researchers From Multiple Brazilian Institutions
The researchers were from the State University of Pará, Federal University of São Paulo, Federal University of Pará, Federal Rural University of the Amazon, Metropolitan University Center of the Amazon (UNIFAMAZ), and Evandro Chagas Institute in Brazil. Their participating units included laboratories specializing in infectious diseases, molecular biology, natural-products chemistry, preclinical studies, health education and arbovirology.
Major Signs of Oxidative Stress
One of the strongest findings involved TBARS, a laboratory marker reflecting lipid peroxidation, or oxidative damage affecting fats in cell membranes. Median TBARS levels reached 5.490 micromoles per liter in long COVID patients compared with only 1.846 in healthy controls—approximately three times higher.
At the same time, several important antioxidant defenses were dramatically reduced. Superoxide dismutase activity was 0.600 versus 1.940 U/mg Hb in controls, while catalase was 0.136 versus 0.310. Glutathione peroxidase showed an especially striking difference: 0.097 versus 0.420 U/mg Hb.
Total antioxidant capacity was also significantly lower. In simple terms, patients showed more evidence of oxidative cellular damage while simultaneously having weaker biological systems available to control that damage.
As explained in this Thailand
Medical News report, oxidative stress develops when harmful reactive molecules overwhelm the body's antioxidant defenses. Persistent imbalance could potentially interfere with cell membranes, proteins and other cellular structures.
Blood Vessel Function May Also Be Affected
Nitric oxide levels were lower in long COVID patients, measuring 29.01 micromoles per liter compared with 31.45 among controls. Nitric oxide helps blood vessels relax and supports normal circulation, so reduced availability is consistent with a possible vascular component to long COVID.
Importantly, researchers divided patients according to symptoms lasting s
ix months or less, six to 12 months, and more than 12 months. None of the oxidative-stress markers differed significantly between these groups. This suggests the abnormal redox pattern was not simply disappearing as more time passed; abnormalities were observed across durations extending to 32 months.
Important Limitations
The study cannot prove oxidative stress causes long COVID symptoms. It was cross-sectional, involved a relatively small population and used historical healthy controls collected before the pandemic. Differences in age and sex between groups also require consideration, although sex-stratified analyses generally preserved the oxidative-stress pattern.
Conclusions
The findings suggest long COVID can involve a remarkably persistent biological imbalance, combining increased lipid oxidation, depleted antioxidant defenses and reduced nitric oxide availability. Further longitudinal studies are needed to determine whether these abnormalities drive symptoms, result from other ongoing disease processes, or could eventually become useful targets for treatment.
The study findings were published in the peer reviewed journal: Antioxidants.
https://www.mdpi.com/2076-3921/15/8/1013
Read Also:
https://www.thailandmedical.news/articles/long-covid
Share
Tweet
Share
