You optimise your training load. You track your recovery. You invest in your nutrition. So when the research points to antioxidants reducing oxidative stress from exercise, supplementing seems like a logical performance lever to pull.

But what if that investment was quietly working against your returns?

This is one of sport nutrition's most counterintuitive findings: in certain situations, high-dose antioxidant supplements can interfere with the very physiological adaptations your training is designed to produce. For athletes focused on long-term gains, understanding this trade-off isn't optional but rather strategic.

The Signal You Don't Want to Silence

Exercise generates reactive oxygen species (ROS). In excessive amounts, ROS cause cellular damage. But at the levels produced during regular training, ROS function as critical signalling molecules. Thes are the biological triggers that tell your body to adapt and grow stronger.

This is hormesis in action: a controlled stressor driving a beneficial response. Specifically, ROS signals initiate mitochondrial biogenesis, boost your body's own antioxidant enzyme production, improve insulin sensitivity, and drive muscle remodelling. These are the fundamental physiological upgrades that separate a trained athlete from an untrained one.

Flood your system with high-dose antioxidant supplements, and you risk silencing those signals and potentially blunting the return on every training session.

Chronic supplementation with approximately 1,000 mg/day of vitamin C and/or 200–400 IU/day of vitamin E has been shown to reduce activation of key pathways involved in mitochondrial development and endogenous antioxidant defences.^[1][2] A 2026 review published in Antioxidants framed this as a redox balance problem: the goal isn't zero oxidative stress, it's the right amount.^[2]

This concern applies specifically to chronic, high-dose supplementation. Context matters: illness, extreme training loads, and specific recovery protocols are different conversations.

The scale of this issue is significant as vitamin C is taken by nearly 60% of athletes^[3] many of whom may be unknowingly compromising their adaptation response.

The Smarter Play: Food First

Dietary antioxidants sidestep this problem. Consumed through whole foods, antioxidants arrive in lower doses alongside other nutrients and phytochemicals that modulate their absorption making interference with training adaptation far less likely.^[2]

Vitamin C from whole foods also plays a critical structural role beyond antioxidant activity — it is essential for collagen synthesis and tendon repair, and enhances iron absorption both critical for athlete health and energy production.

Beyond vitamin C and E, other whole-food antioxidant sources offer targeted recovery benefits: blueberries have demonstrated reductions in exercise-induced muscle soreness and inflammation, while tart cherries support both recovery and sleep quality without the risk of blunting adaptation.

Top 10 Vitamin C–Rich Foods

Per 100g — FSANZ Australian Food Composition Database (AFCD)^[5]

Vitamin E–Rich Foods

Per 100g — FSANZ Australian Food Composition Database (AFCD)^[5]

 The Bottom Line

Stand firm and demand a return on every investment including nutritional ones. Antioxidant-rich whole foods deliver recovery support, structural benefits, and immune resilience without compromising adaptation. Routine high-dose vitamin C or E supplements may do the opposite.

Build your antioxidant strategy around food first. Reserve supplementation for specific, evidence-based applications and let your training deliver the results it was designed to produce.

Have you ever heard of hepcidin? It’s worth understanding mainly if you are a female athlete or someone who suffers from iron deficiency anaemia.

Iron is an essential element for many biological processes. Too little iron can have many detrimental effects on your health and sports performance. We have previously discussed the impact iron deficiency and anaemia has on thyroid health and poor immunity. Excess iron can be toxic, so regulating iron levels are vital to a healthy, balanced body.

Hepcidin is an iron-regulating peptide hormone that’s produced in your liver. It works to control the delivery of iron to your blood from food through the lining of the intestines. It is the master regulator in iron metabolism and the balance between iron storage and the absorption better known as iron homeostasis. Hepcidin also tightly influences red blood cell production.

When hepcidin levels are unusually high, it reduces intestinal iron absorption and red blood cell production. Low hepcidin levels stimulate iron absorption, and iron supply to bone marrow and promote hemoglobin and red blood cell production. Iron deficiency is common among female athletes, and is much higher than their male counterparts. It is often cited as being a result of the menstrual cycle during premenopausal years. Depleted iron stores can have many adverse effects, including poor performance, low energy levels, and general well-being.

Some research has shown that active females with compromised iron possess an inherent protective mechanism once iron deficient. This adaptation allows the body to adjust to a reduced iron supply. It is proposed iron depletion may be a combination of exercise-induced losses and hepcidin accumulation.

Running is known to acutely increase hepcidin levels (peaking three hours post-exercise), therefore reducing iron absorption and recycling.

Timing iron supplementation to correlate with low hepcidin levels may enhance absorption and positively impact iron levels in the blood. In practical terms, if you exercise in the morning, you might consider taking your iron supplement straight after you exercise, before hepcidin rises.

Hundreds of athletes have used our handy anaemia quiz to help determine the likely risk of having low iron or anaemia. we encourage you to use this free tool if you have a history of iron deficiency or you are unsure if your iron stores may be declining.

Want to know more? Contact the Athlete Sanctuary to learn how we can support you further. Book an appointment here.

About the Author: Kate Smyth is a Sports naturopath, nutritionist and female-centric running coach. She is the founder of the Athlete Sanctuary- a holistic healthcare clinic for athletes of all levels and sporting codes. Kate has a thirst for knowledge with two bachelor’s and a master’s degree under her belt. She has been involved in sports for many decades and competed for Australia in the Commonwealth Games and Olympic Games marathons with a personal best time of 2 hours 28 minutes. For more information visit https://athletesanctuary.com.au/kate-smyth

References

Ganz, T. (2016). Hepcidin. Rinsho Ketsueki, 57(10), 1913-1917. DOI: 10.11406/rinketsu.57.1913.

Sim, M., Dawson, B., Landers, G., Trinder, D., & Peeling, P. (2014). Iron regulation in athletes: exploring the menstrual cycle and effects of different exercise modalities on hepcidin production. International journal of sport nutrition and exercise metabolism, 24(2), 177-187.https://pubmed.ncbi.nlm.nih.gov/24225901/

Alfaro-Magallanes, V. M., Benito, P. J., Rael, B., Barba-Moreno, L., Romero-Parra, N., Cupeiro, R. FEMME Study Group. (2020). Menopause Delays the Typical Recovery of Pre-Exercise Hepcidin Levels after High-Intensity Interval Running Exercise in Endurance-Trained Women. Nutrients, 12(12), 3866. https://pubmed.ncbi.nlm.nih.gov/33348847/

Nirengi, S., Taniguchi, H., Ishibashi, A., Fujibayashi, M., Akiyama, N., Kotani, K., & Sakane, N. (2021). Comparisons between serum levels of hepcidin and leptin in male college-level endurance runners and sprinters. Frontiers in Nutrition, 8. https://pubmed.ncbi.nlm.nih.gov/34136516/

Pagani, A., Nai, A., Silvestri, L., & Camaschella, C. (2019). Hepcidin and anemia: a tight relationship. Frontiers in physiology, 1294.  https://www.frontiersin.org/articles/10.3389/fphys.2019.01294/full

Sim, M., Dawson, B., Landers, G., Trinder, D., & Peeling, P. (2014). Iron regulation in athletes: exploring the menstrual cycle and effects of different exercise modalities on hepcidin production. International journal of sports nutrition and exercise metabolism, 24(2), 177-187.  https://pubmed.ncbi.nlm.nih.gov/24225901/[/vc_column_text][/vc_column][/vc_row]

Iron plays a crucial physiological role in your body. But despite its importance, iron deficiency anaemia is still a common problem among female athletes. Iron deficiency can have major adverse effects on your well-being and your athletic capacity.

It’s not uncommon for iron deficiency anaemia to be quite mild and go unnoticed. But women – and especially active, athletic women – are very prone to this condition. If gone untreated, the anaemia will worsen, and the signs and symptoms will intensify.

Without enough iron, your body can’t produce enough hemoglobin – the substance in red blood cells that enables them to carry oxygen – and as a result iron deficiency anaemia can leave you short of breath, headachy, tired, and unable to complete a training session or event with your usual enthusiasm. Iron deficiency is missed in 47-82% of females and 95-100% of male adolescents and young adult patients.

10 signs of iron deficiency  

*Fatigue that starts even after a good night’s sleep

*Restless legs

*Nausea

*Bruising

*Pale or itchy skin

*Hair loss

*Shortness of breath

*Poor concentration and decision-making, “foggy brain”

*Rapid heartbeat or “fluttering feeling”

*Headache, dizziness or light-headedness

Keep in mind this is just a small number of the  75 known symptoms of iron deficiency. Unusual cravings for non-nutritive substances, such as ice and dirt

CAUSES OF IRON DEFICIENCY

Low or little dietary intake of iron-rich foods is often blamed as the key factor contributing to iron deficiency. With plant-based eating increasing in popularity amongst the athlete community, this is a key factor for many athletes. Lack of awareness of how to consume foods that enhance iron absorption or knowledge on sources of plant-based iron-rich foods can render an athlete with symptoms in a matter of months.  Poor intake however is not the only cause of iron deficiency anaemia.

*Blood loss. Blood contains iron within red blood cells. If you lose blood, you lose some iron. Women with heavy periods are at risk of iron deficiency anaemia because they lose blood during menstruation. Athletes who are frequent blood donors are at increased risk for iron deficiency.¹ Athletes who regularly use nonsteroidal anti-inflammatories are likely to have increased gastrointestinal blood losses increasing their risk of iron deficiency³.

*An inability to absorb iron. Dietary iron is absorbed into the bloodstream through the small intestine. An intestinal disorder, such as celiac disease, stomach ulcers, ulcerative colitis or Crohn’s disease, which affects the intestine's ability to absorb nutrients from digested food, can lead to iron-deficiency anaemia. If part of the small intestine has been bypassed or removed surgically, the ability to absorb iron and other nutrients will be reduced. Inflammation in the digestive tract is aligned with symptoms such as bloating, gas, diarrhoea or constipation, food intolerances, or loud gurgling, and may signal the integrity of the gut lining may be compromised. Without good integrity, absorption of nutrients is also reduced.

*Low stomach acid. Adequate stomach acid (hydrochloric acid- HCL) is required to break down minerals such as iron and extract them from the food we eat. Low stomach acid is a common issue following times of prolonged physical or emotional stress and can be found alongside iron deficiency.

*Iron stealers. Bacteria overgrowth, Helicobacter pylori, and parasites within the digestive tract can impact the way iron is absorbed and may contribute to blood loss, therefore, contributing to iron deficiency over time.

*Post natal- Without iron supplementation, iron deficiency anaemia occurs in many pregnant women due to the iron requirements of the mother and baby. Post-natal iron deficiency can occur as many women are naturally preoccupied with their new arrival and forget to have adequate medical checkups for themselves. Fatigue is often experienced by mother’s and therefore iron deficiency can go undetected for many months. This depletes not only the mother but also the baby’s supply of iron who depends on the mother for iron for the first 6 months of life until solids are introduced.

Hundreds of athletes have used our handy anaemia quiz to help determine the likely risk of having low iron or anaemia. Find out if you are getting low on iron here.

Want to know more? Contact the Athlete Sanctuary to learn how we can support you further.

About the Author: Kate Smyth is a Sports naturopath, nutritionist and female-centric running coach. She is the founder of the Athlete Sanctuary- a holistic healthcare clinic for athletes of all levels and sporting codes. Kate has a thirst for knowledge with two bachelor’s and a master’s degree under her belt. She has been involved in sports for many decades and competed for Australia in the Commonwealth Games and Olympic Games marathons with a personal best time of 2 hours 28 minutes. For more information visit https://athletesanctuary.com.au/kate-smyth

References

1. Choe, Y. H., Kwon, Y. S., Jung, M. K., Kang, S. K., Hwang, T. S., & Hong, Y. C. (2001). Helicobacter pylori-associated iron-deficiency anemia in adolescent female athletes. The journal of Pediatrics, 139(1), 100-104.
2. Eiduson, R., Heeney, M. M., Kao, P.-C., London, W. B., Fleming, M. D., & Shrier, L. A. (2022). Prevalence and Predictors of Iron Deficiency in Adolescent and Young Adult Outpatients: Implications for Screening. Clinical Pediatrics, 61(1), 66–75. https://doi.org/10.1177/00099228211059647
3. Safarova, K. N., Dorogoykina, K. D., & Rebrov, A. P. (2019). Is anemia a clinical marker of NSAID-induced upper gastrointestinal lesions in patients with spondyloarthritis?. Almanac of Clinical Medicine, 47(5), 410-418. https://doi.org/10.18786/2072-0505-2019-47-037
4. Hinton P. S. (2014). Iron and the endurance athlete. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolism, 39(9), 1012–1018. https://doi.org/10.1139/apnm-2014-0147
5. Mayo Clinic (2022). Iron Deficiency anemia. https://www.mayoclinic.org
6. Sim, M., Dawson, B., Landers, G., Trinder, D., & Peeling, P. (2014). Iron regulation in athletes: exploring the menstrual cycle and effects of different exercise modalities on hepcidin production. International journal of sports nutrition and exercise metabolism, 24(2), 177–187. https://doi.org/10.1123/ijsnem.2013-0067