Why High-Dose Antioxidant Supplements Can Sabotage Your Training — and Why Olive Oil Doesn't

Every serious athlete knows the drill: train hard, hurt, recover, repeat. The narrative around antioxidants has long been simple — reactive oxygen species (ROS) damage your muscles after a hard session, so you load up on vitamin C and E, take your antioxidant cocktail, and accelerate recovery. It's intuitive. It's also, in many cases, exactly wrong.

A comprehensive 2025 narrative review published in Antioxidants (Basel) by researchers from the University of Naples Federico II, IRCCS San Raffaele Rome, and the University of Padova synthesizes what the sports physiology literature has been quietly accumulating for a decade: indiscriminate antioxidant supplementation can impair the very training adaptations athletes are working toward. And sitting quietly in the background of that finding is a food that athletes in the Mediterranean world have consumed for millennia — extra virgin olive oil.

The question this paper forces us to ask is genuinely important: if blunting ROS blunts adaptation, does that mean athletes should avoid all antioxidants? Or are there smarter antioxidants — ones that dampen excess oxidative damage without silencing the signaling molecules you actually need?

The review was authored by a multi-institutional Italian team spanning endocrinology, sports medicine, and human physiology. The primary affiliation — the University of Naples Federico II — sits in one of the world's great olive oil-producing regions, though the authors declare no conflicts of interest and the paper is freely available via PubMed Central.

The review's scope is ambitious: synthesize what is known about exercise-induced oxidative stress, antioxidant supplementation strategies, and the emerging role of the Mediterranean diet (with EVOO as its signature component) in modulating redox physiology for competitive athletes. It draws on randomized controlled trials, observational studies, mechanistic research, and prior systematic reviews — prioritizing human data where available.

Because this is a narrative rather than systematic review, it cannot deliver pooled effect sizes or forest plots. What it delivers instead is a mechanistic framework — a way of understanding why EVOO phenolics behave differently from isolated antioxidant supplements, and how that difference matters for anyone who trains seriously.

To understand why olive oil behaves differently from vitamin C and E tablets, you need to understand the concept of hormesis — the biological principle that stressors are beneficial at low doses and harmful in excess. Exercise-induced ROS production is hormetic. The challenge is not to suppress it but to keep it within the adaptive zone.

The review also highlights gut microbiota modulation as an underappreciated channel. EVOO polyphenols reshape the gut microbial community, which in turn influences systemic inflammatory tone and even polyphenol bioavailability through microbial biotransformation of secoiridoids into active metabolites. Athletes with different gut microbiome compositions may therefore respond differently to EVOO — a finding with significant practical implications for personalized sports nutrition.

There is also an immune dimension. EVOO's Mediterranean dietary context appears to sustain immune competence during heavy training periods — a practical concern for athletes who frequently experience upper respiratory infections during high-volume training blocks. The proposed mechanism is a more balanced cytokine milieu that avoids both excessive inflammation and the immune suppression seen after ultramarathons and multi-day events.

The "antioxidant paradox" described in this review is not a new claim — Ristow et al. published influential work in 2009 showing that vitamins C and E supplementation prevented the insulin-sensitizing effects of exercise in humans. What the Annunziata et al. 2025 review adds is a comprehensive synthesis of how the Mediterranean diet, and EVOO specifically, fits into this landscape as an alternative to isolated supplementation.

The review's positioning of the Mediterranean diet as a "biochemically coherent antioxidant system" rather than just a collection of healthy foods is theoretically important. Earlier reviews of polyphenols and exercise tended to focus on isolated compounds — quercetin, resveratrol, curcumin. The Annunziata team argues that the synergistic interactions among EVOO's phenolics, the monounsaturated oleic acid matrix, and the broader Mediterranean dietary context produce outcomes that isolated compounds cannot replicate.

This is consistent with the growing literature on food synergy — the observation that whole foods outperform their isolated components in ways not predicted by nutrient-by-nutrient analysis. For olive oil, the relevant synergy appears to be between hydroxytyrosol (Nrf2 activator), oleocanthal (NF-κB inhibitor), oleuropein (mitochondrial membrane stabilizer), and oleic acid (PUFA membrane incorporation that reduces susceptibility to lipid peroxidation).

The review also compares EVOO favorably against other antioxidant-rich dietary patterns. While the DASH and Nordic diets are acknowledged as antioxidant-rich, the review argues EVOO's unique phenolic profile and the long-term cardiometabolic evidence base make it uniquely positioned in redox physiology — a claim that is well-supported but would benefit from head-to-head dietary comparison trials in athletes.

The review does not make specific dosing recommendations for EVOO in athletes — this is an honest reflection of where the evidence currently sits. Large RCTs specifically studying EVOO and exercise performance in human athletes do not yet exist. What the review does offer is a framework, and from that framework several practical implications emerge.

The review's most practically important observation for athletes may be this: the Mediterranean diet delivers antioxidants within a food matrix, not as isolated compounds. This distinction has significant physiological implications. Polyphenols bound in food matrices show different absorption kinetics, interact differently with the gut microbiome, and appear to modulate redox biology in more contextually sensitive ways than pure compounds at pharmacological doses.

The authors are admirably candid about the limitations of the current evidence base, and this candor is itself a sign of a high-quality review. Several important caveats deserve attention:

Let's be precise: this review is not a clinical trial that proves EVOO improves athletic performance. That study has not been done. What it is — and what it does extremely well — is build a mechanistic case that is more rigorous than most of the supplement marketing that athletes consume alongside their protein shakes.

The review's most important contribution is the framing of the antioxidant paradox. The sports nutrition industry has sold antioxidant megadosing to athletes for decades based on a reductionist premise: exercise creates ROS, ROS damage muscle, antioxidants neutralize ROS, therefore antioxidants improve recovery. The 2025 Annunziata review synthesizes the evidence that this logic is incomplete. ROS are not merely damage — they are signal. Eliminate the signal, and you impair the adaptation.

Within that framework, EVOO phenolics look genuinely interesting. Not because they're more potent antioxidants — they're not. But because their mechanism of action is qualitatively different. Activating Nrf2 to upregulate the body's own antioxidant enzymes is a more contextually intelligent response than flooding cells with exogenous antioxidant molecules. The body regulates Nrf2 activity; it cannot regulate how much vitamin C you just drank.

The PGC-1α preservation data is where the real excitement lies. If EVOO polyphenols can dampen excessive post-exercise oxidative stress while leaving PGC-1α-driven mitochondrial biogenesis intact — and the animal evidence suggests they can — then they thread the needle that isolated antioxidants cannot. You get recovery without sacrificing adaptation.

The limitation we cannot ignore: elite athletes are not Sprague-Dawley rats, and 3 tablespoons of EVOO per day does not deliver 25 mg/kg of hydroxytyrosol as a pure compound. Real-world EVOO polyphenol bioavailability is substantially lower, and gut-microbiome-dependent biotransformation means that absorption varies enormously between individuals. The RCT that the field needs — 12 weeks, competitive athletes randomized to high-polyphenol EVOO vs. refined olive oil vs. control, with mitochondrial biogenesis endpoints — has not been funded or published.