Posted on May 11, 2026 at 06:00 AM
Athletes are regularly told to eat more antioxidants, and there’s a lot of aggressive marketing around this to make them seem like a no-brainer.
What is rarely said about triathletes is that too much, at the wrong time, can work against them. I see this all the time in my work as a sports nutritionist: Athletes are gasping for the latest miracle antioxidant supplement that will solve all their problems, yet there’s no actual evidence to back up such claims.
In this article, I’ll review the latest Attitude toward antioxidants and exercise performance by the International Society of Sports Nutrition (ISSN), and how it relates to training and racing performance.
I will also relate this to what I see In reality The business, having supported amateur and professional athletes to reach the podium over the past seven years.
What are antioxidants and what do they do?
Antioxidants are compounds found in food and produced by your body that help neutralize free radicals: unstable molecules that, in excessive amounts, damage cells, proteins and DNA.
This process is called oxidative stress, and when it becomes chronic, it is associated with increased risk of disease, poor recovery, and decreased performance.
When you exercise, a moderate rise in free radicals is part of what tells your body to adapt by building more mitochondria, improving oxygen delivery, and ultimately getting you fitter.
The problem comes at the extreme: too little, and you don’t create enough pressure to drive adaptations. Too much, and you can suffer long-term oxidative damage that impairs performance.
The idea is that antioxidants can help manage this response, keeping oxidative stress in the beneficial zone rather than allowing it to cause damage. But if you consume too many antioxidants at the wrong time, it can impair the adaptations you’re training.
The first nutritional approach to antioxidants for triathletes
Whole foods rich in antioxidants are the preferred strategy, with supplements tailored to true nutritional gaps or specific periods of high stress.
Here’s a simple guide, drawn from the classes of antioxidants that the research identifies as most relevant:
My biggest practical piece of advice for athletes: Eat plenty of plants in a wide range of colors.
You don’t have to eat all the foods on the above list in the exact amounts and frequencies, but instead consider adding these foods regularly to your diet.
In my experience working with athletes, this single habit makes a bigger difference than most people expect, and it’s one of the first things I focus on with new clients.
5 antioxidants worth considering
If your diet is already solid and you would like to consider targeted antioxidant supplements to advance your triathlon goals, the following has the best evidence base.
I always recommend that athletes targeting antioxidant supplements use products that have been third party tested through programs such as Informed sportAnd understand that all nutritional supplements carry the risk of containing banned substances, to ensure you make an informed decision.
1. Cherry tart
A 2021 meta-analysis of 14 studies I found improvements in muscle strength recovery, reduced delayed onset muscle soreness, and decreased markers of inflammation after strenuous exercise.
A separate meta-analysis found this Eating tart cherries for seven days up to 90 minutes before an endurance event improved time trial and time to exhaustion performance..
It is too Raises circulating melatonin levelsThis is why it is especially useful during difficult training periods where sleep quality often suffers along with fatigue. This combination of recovery, performance, and sleep support is why Tart Cherry earns its place on my list.
dose: 480 mg of powder or 60-90 ml of concentrate daily for 7-14 days.
Not for daily use year round – reserve it for race buildups and heavy training blocks.
2. Omega-3 fatty acids
A meta-analysis of 39 trials with over 28,000 participants Improvements in total antioxidant capacity and reductions in markers of lipid peroxidation were found.
In the course of the exercise, Fish oil supplements have been shown to reduce signs of muscle damage and inflammation After resistance training.
Most of the evidence for exercise comes from resistance training groups, so we can’t be completely clear about the benefits for triathletes – but the mechanisms are sound, and the safety profile is excellent.
dose: 1000-2000 mg of EPA+DHA daily from food or from a high-quality fish oil supplement. Suitable for continuous use.
Higher doses of up to 6,000 mg/day have been used in studies for acute recovery periods – consider this for 2-3 weeks around heavy training periods.
3. Creatine monohydrate
Creatine is one of the most widely researched nutritional supplementsImprove high-intensity performance, power output, and sprint ability.
Its antioxidant and anti-inflammatory effects are minor and not well proven – I would not recommend it specifically for recovery.
But for athletes who do strength and high-intensity work, the performance benefit is real, and any anti-inflammatory effect is a welcome bonus.
One study found that creatine supplementation before an Ironman 70.3 reduced increases in inflammatory markers after the race.But it is unclear what the long-term benefit is from an inflammatory perspective.
dose: 0.1 g/kg/day (maintenance). The typical dose is 5 grams per day for adults. This is suitable for continuous use, without the need for breaks.
4. Vitamin C
The evidence for the use of vitamin C as a standalone performance supplement is weak, but it has its place on my list for supporting immune function during periods of intense training or at the onset of illness.
Low levels of vitamin C are associated with decreased physical performance and increased oxidative stressand A 2023 meta-analysis found that taking 1,000 mg/day of vitamin C reduces cold severity by 15% and may also shorten the duration of illness..
dose: 1000 mg/day short term (1 or 2 weeks at the beginning of the disease or during a particularly severe block). Experts do not recommend this dose long-term – to learn more about why, see the ‘Avoid’ section below.
5. Vitamin E
Vitamin E works best with vitamin C The two recycle each otherwith C regenerating E after it neutralizes the free radicals.
The evidence on supplements alone is limited, and the priority here should be food sources such as nuts, seeds and vegetable oils that give you significant amounts.
Like vitamin C, the danger of supplementation comes with high doses over time.
dose: 400-800 IU/day if taking supplements, and in conjunction with vitamin C only. But again, it is recommended to eat foods rich in vitamin E daily instead of taking supplements.
Antioxidants to be suspicious of
High doses of vitamins C and E – long term
Yes, these items have appeared on the list of nutritional supplements worth paying attention to!
But when taken in large doses over long periods, Research shows that they can actually impair training modifications.
So, while marketing likes to tout high doses of antioxidants for athletes, science says caution should be taken.
Beetroot – for antioxidant purposes
Beetroot may play a role in performance through its nitrate content The evidence is more controversial Than the headlines suggest – but as an antioxidant supplement, the case simply isn’t there.
For antioxidant and recovery purposes, Systematic reviews consistently show that beets have no measurable effect on oxidative stress or inflammatory biomarkers.
Several well-designed studies in marathon runners, collegiate athletes, and ultra-endurance runners have found no effect on exercise-induced oxidative stress.
Spirulina
Spirulina appears in almost every “superfood” supplement blend.
Evidence of any meaningful benefit in trained athletes is Weak at best. Most studies show no measurable effect on performance or recovery, so save your money.
My honest story from seven years supporting professional, race-winning athletes
My honest opinion as a sports nutritionist is that antioxidants can be helpful in specific scenarios, but they rank pretty low on the priority list.
The triathletes I’ve worked with who perform the best are not the ones with the most optimized combination of supplements. Instead, they are people who eat well, sleep right, and treat supplements as just a little extra, not the foundation.
