Our bodies’ immune responses to viruses or bacteria can create oxidative stress.
“That causes the rest of the body to go into a response state and bring in everything to start fighting the infection,” Mitchell explains.
And while the goal is to get rid of germs, this immune response can also trigger inflammation, which can worsen as we get older.
“As you age, you have sterile immune responses, which means there’s no virus, there’s no bacteria, there’s nothing that’s really causing a problem – but you’re now having a big immune response which is causing chronic inflammation, which is causing this constant oxidative stress.
“This can lead to inflammation so overwhelming that it can actually kill you.”
Long-term, chronic inflammation can lead to a range of diseases, from cancer to diabetes, heart disease, autoimmune conditions, organ failure and neurodegenerative diseases like Alzheimer’s and Parkinson’s.
How does oxidative stress happen?
Oxidative stress is the term given to damage caused by an imbalance between your body’s free radicals and protective antioxidants.
This imbalance is usually well controlled by your body’s systems, but can easily get out of control, causing inflammation and potentially leading to diabetes, cancer, heart disease and more.
Free radicals take electrons from other molecules, like lipids and proteins, doing damage to them in the process.
“For instance, DNA needs all its electrons to function the way it’s supposed to, but when the free radical grabs that electron from the DNA, now the DNA’s damaged. It’s not going to be read the right way, it’s mutated,” Mitchell explains.
“When you’re under stress, when you’re having too much inflammation or too much energy use, you’re going to cause more and more oxidative stress to the point where your body can’t fix it anymore.”
WATCH: Dr Siobhan Mitchell explains how women can look after their heart health
Who is most at risk of excess stress and inflammation?
Obesity is a risk factor – but Mitchell notes that high-performance athletes can have too much oxidative stress too.
“People think athletes are kind of protected from everything because they’re so strong… [but] for instance, people who do the Tour de France die sooner because they have probably put too much oxidative stress into their bodies,” she says.
“People who are obese or overweight also have more oxidative stress because they have more inflammation in their adipose tissue [body fat], and that inflammation is causing more oxidative stress throughout the body.”
Does it impact men and women differently?
There are some differences between men and women when it comes to oxidative stress, mostly due to hormones.
“Women have better control of their oxidative stress, especially in their brain and also their muscles and their heart, before menopause because of estrogen,” Mitchell says.
Estrogen has a protective effect on the body, acting as an antioxidant – but after menopause, it’s no longer produced by the ovaries.
“Unfortunately that all goes away during menopause, and [women] start to have more oxidative stress.”
Oxidative stress can also accelerate ageing and associated health problems. Mitchell cites a study showing that oxidative stress in the brain has been correlated with cognitive fatigue as well as cognitive decline over time.
“Oxidative stress in the brain is not only linked to dementia but literally how much motivation you have,” she says.
“If you’re not taking care of your oxidative stress, even just the motivation to do daily activities can go down a lot.”
Eating a healthy diet with plenty of fruits and vegetables can help balance your oxidative stress levels. Photo / 123rf
Can you measure – and control – your oxidative stress?
Before menopause, most women probably have their oxidative stress under control, Mitchell says.
“It’s mostly maintenance – eat a lot of antioxidants in their diet and exercise.
“But as they go through menopause, they really need to look at their diet and make sure they’re not leaning towards obesity. Stay away from all those things that cause oxidative stress. For instance, drinking a lot [of alcohol] – the oxidative stress in our liver is worse if you’re a woman, because our livers are just smaller and they can’t deal with it as well.”
Mitchell says you can get an idea of your oxidative stress levels through measuring your heart rate variability (HRV) on a smart watch.
“When HRV is a low number, that means you have worse HRV. This just means you are using more energy in your body, and you’re making more oxidative stress in your body at the same time … so you want to keep your HRV as high as possible.”
When it’s controlled, oxidative stress helps build resilience in the body, Mitchell says.
“This is especially seen with exercise. [It’s] going to cause a lot of oxidative stress, but when it’s controlled for a certain amount of time, it’s actually very beneficial for the cells to learn to build more machinery… and make better antioxidant systems to deal with all this oxidative stress.”
Oxidative stress in the muscles from an intense workout can cause DNA damage – one reason why recovery from exercise is so important.
“If you don’t give yourself enough recovery time, you’ll just have more and more damage in your muscles to the point where everyone’s like, ‘Why do we not have the same exercise performance in our 30s or 40s as we did in our 20s?’ That’s because oxidative stress has damaged our muscles beyond repair.
“So… you need to give yourself the right amount of recovery.”
Bethany Reitsma is a lifestyle writer who has been with the NZ Herald since 2019. She specialises in all things health and wellbeing and is passionate about telling Kiwis’ real-life stories.