Inflammation, or exercise-induced oxidative stress, is a common problem among endurance athletes. But taking antioxidant supplements is not the answer, says Rob Hobson, who here explains this complicated condition further…
You’ll have heard and read the term ‘inflammation’ a lot in the media, and no doubt have suffered from it in some form, at some point, as an active triathlete. But what exactly are we talking about here? And how can we reduce the risk of ‘inflaming’ our body through exercise?
Research has shown that chronic inflammation is detrimental to health as it can increase the risk of many diseases. However, in athletes, there’s more to the story.
When discussing inflammation in athletes it usually relates to a state referred to as ‘exercise-induced oxidative stress’. This can occur in athletes that exercise for long periods of time at a high intensity, as is the case in endurance sports.
Exercise-induced oxidative stress can trigger inflammation and occurs when free radicals outweigh antioxidants. But this is not always a bad thing.
The science of free radicals and antioxidants is often oversimplified in the media. As a result, athletes may respond to the notion of exercise-induced oxidative stress by taking high doses of antioxidant supplements.
What is inflammation?
Everyone will have experienced the redness, swelling and heat that occurs when you cut yourself – this is known as acute inflammation and is a short-lived process to help trigger the healing process and prevent infection.
Chronic inflammation is something that’s more likely to occur in people who are obese. This normally begins with the same response to illness or injury but turns into a lingering state that persists for months or years when the immune system response fails to eliminate the problem.
This type of inflammation may stay active even after the initial threat has been removed, meaning the low-level inflammation becomes activated even when there’s no apparent injury or disease.
This can lead to the immune system prompting white blood cells to attack nearby healthy tissues and organs.
And it’s this level of inflammation that’s thought to play a central role in many of the most challenging human diseases, including rheumatoid arthritis, cancer, heart disease, diabetes, asthma, and even Alzheimer’s.What are free radicals and antioxidants?
The science behind free radicals and antioxidants is complex. The way they’re described in the health media is normally oversimplified as free radicals being bad and antioxidants being good. Antioxidants are often viewed as the superhero defending the body against damage caused by free radicals.
Free radicals are very reactive chemicals, and the most common found in living tissues are called reactive oxygen species (ROS), which, as the name suggests, contain oxygen.
They’re produced because of chemical processes that occur naturally in the body, such as the conversion of food into ATP, which is the energy currency of the body.
Free radicals are also produced as a by-product of consuming oxygen during exercise breaking down ATP to provide energy for muscle tissue.
The body is fully equipped to deal with free radicals, which are neutralised by antioxidants. These chemicals can perform this task without damage or becoming free radicals themselves.
If free radicals outweigh antioxidants the body becomes vulnerable to oxidative stress, which triggers inflammation and over time can damage cells and tissues.
Free radicals are not always bad, though, as they have an important role to play in many normal cellular responses.
Alongside other chemicals, free radicals are used by the immune system to help kill foreign invaders (phagocytes) by a defence mechanism known as an oxidative burst.Should athletes avoid antioxidant supplements?
Long periods of intense exercise have been shown to promote oxidative stress, which, as mentioned above, is referred to as ‘exercise-induced oxidative stress’.
This is more likely to occur among endurance athletes given the time spent exercising at a high intensity and causes damage to muscle fibres and accelerates muscle fatigue.
To offset this damage, some athletes may assume a benefit from boosting their intake of antioxidants, using high-strength supplements, but this can prove counterproductive.
Free radicals (ROS) are continually produced in muscles both at rest and during exercise. These chemicals modulate processes such as the regulation of blood flow, muscle force production and muscle adaptation.
The production of ROS in muscle during endurance exercise plays a key role in cell-signalling pathways involved in muscle adaptation. Consuming high levels of antioxidants by way of supplementation can blunt these training-induced changes in muscle fibres.
Aside from this, the body adapts to increased exercise by upregulating antioxidant enzymes in the body. Unlike dietary antioxidants that can only be used once, these enzymes, which include superoxide dismutase and glutathione peroxidase, can be used over and again.
Hence, the more exercise you do the more of these enzymes will be produced to protect the body, which is independent of dietary antioxidant intake.
How can athletes maintain a good intake of antioxidants from their diet?Antioxidants are still important, but during the initial stages of training when adaptations occur they’re better sourced from the diet. Dietary antioxidants are found in fruits, vegetables and grains, which are all a rich source.
Examples of dietary antioxidants include lycopene and beta carotene found in red, orange and green vegetables, as well as vitamins A, C, E and minerals such as selenium. Plants also contain compounds such as polyphenols, which act as antioxidants and are found in foods such as berries and raw cacao.Are there any benefits to taking antioxidant supplements?
Dietary antioxidants are important for an athlete’s overall health. The foods that contain them are also rich in many other nutrients that help to ensure an athlete’s nutrient status.
There’s little evidence to support the use of high strength antioxidant supplements containing vitamins and minerals, such as vitamins A and C. Still, if an athlete has a poor diet for whatever reason then they may benefit from a multivitamin and mineral supplement.
Supplements made from fruit extracts have grown in popularity, in particular blackcurrants and sour cherries. These fruits are rich in anthocyanins, which are plant compounds responsible for their purple, blue and red colour. Anthocyanins also act as antioxidants in the body.
These supplements have been studied for their potential to improve both performance and recovery. There have been a number of positive findings from the research of blackcurrant supplements, which have been the result of several suggested mechanisms. These supplements appear to help improve blood flow by opening up blood vessels to improve the delivery or oxygen and nutrients to muscle cells.
Blackcurrant extract has also been shown to help improve fat oxidation, which may improve performance by sparing glycogen and reducing the amount of carbohydrate refuelling during a race.
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