Popular nitrate supplements may blunt exercise-driven heart benefits in female mice — what athletes and clinicians need to know

Table of Contents

1. Key Highlights
2. Introduction
3. What the Dalhousie study did, and what it found
4. Why these cardiac adaptations matter: how exercise remodels the heart
5. How dietary nitrates and beetroot supplements are supposed to help
6. Why the Dalhousie results challenge assumptions about chronic supplementation
7. Why female hearts responded differently: potential mechanisms
8. Broader context: how sex has been overlooked in preclinical and clinical research
9. What this means for athletes, recreational exercisers and clinicians
10. Regulatory and commercial background: how nitrate products reached athletes
11. Limitations of the Dalhousie study and what it cannot tell us
12. What the next research agenda should include
13. Practical guidance for athletes, coaches and clinicians today
14. Real-world examples and context
15. Safety considerations and interactions
16. Communication and messaging: how to translate the evidence
17. Research ethics and industry responsibility
18. Final reflections before the FAQs
19. FAQ

Key Highlights

• Dalhousie University research found that chronic sodium nitrate supplementation prevented several beneficial cardiac adaptations to aerobic exercise in female mice, while producing few changes in males.
• The supplement interfered with heart structural remodeling, ventricular function and calcium handling in heart cells — processes central to healthier, stronger hearts produced by regular running.
• Findings raise questions about long-term nitrate supplementation during exercise, underscore sex-specific responses, and highlight the need for human trials before changing athlete or public-health recommendations.

Introduction

Nitrate-rich supplements — most commonly beetroot juice and concentrated preparations marketed to runners, cyclists and gym-goers — are widely used to boost endurance and reduce fatigue. These products rest on a well-established biochemical pathway: dietary nitrate is converted to nitrite and then to nitric oxide (NO), a molecule that dilates blood vessels, improves blood flow and influences cellular metabolism.

A new preclinical study from Dalhousie University, published in Scientific Reports (2026), complicates the simple narrative that nitrates are uniformly beneficial. Researchers found that when female mice received chronic sodium nitrate while undertaking aerobic exercise, the usual improvements to heart structure and function from exercise failed to appear. The same supplement produced few effects in male mice. The results challenge assumptions about supplement safety and effectiveness when combined with regular training, and underscore how sex-specific biology can alter outcomes.

The study stops short of proving identical effects in humans. Still, the findings demand closer scrutiny because they touch on three intersecting realities: the popularity of nitrate supplementation among active people, the known cardiovascular benefits of aerobic training, and the historical tendency for research to generalize male-derived results to females. Athletes, coaches and clinicians need a clearer understanding of what current evidence does — and does not — say about nitrate use with exercise.

What the Dalhousie study did, and what it found

Researchers led by Dr. Susan Howlett investigated how sodium nitrate supplementation affected cardiac adaptations to voluntary running in mice. The team divided animals into groups that either received sodium nitrate in their drinking water or did not, and either had access to running wheels or remained sedentary. Both female and male mice were included to compare sex-specific responses.

Key outcomes measured included:

• Heart structure and size (remodeling associated with endurance training).
• Ventricular function, encompassing systolic and diastolic performance.
• Calcium handling in cardiac myocytes — the molecular process that regulates contraction and relaxation of heart muscle cells.

In female mice that ran regularly, sodium nitrate supplementation largely blocked the favorable cardiac changes normally induced by exercise. Those blocked changes included shifts in heart structure and improvements in ventricular function. At the cellular level, the supplement disrupted adaptations in calcium handling that facilitate efficient contractions and relaxation in trained hearts.

Male mice showed far fewer changes when given the same nitrate regimen; running still produced many of the expected benefits in males regardless of supplementation. The magnitude and pattern of sex differences persuaded the authors to emphasize the need for sex-specific testing rather than assuming parity.

The paper’s central line captures the unexpected outcome: "We expected nitrates and exercise to work together to improve heart health. Instead, in females, the supplement prevented many of the positive cardiac adaptations normally produced by exercise," Dr. Howlett said.

The full citation: Elise S. Bisset et al., “Sodium nitrate supplementation prevents beneficial cardiac adaptations to running in female mice with few effects on male hearts,” Scientific Reports (2026). DOI: 10.1038/s41598-026-50082-4.

Why these cardiac adaptations matter: how exercise remodels the heart

Regular aerobic training triggers a coordinated set of structural, functional and cellular adaptations that together improve cardiac performance and resilience. Understanding what was prevented by nitrate supplementation requires a brief look at these adaptations.

• Structural remodeling: Endurance exercise typically induces eccentric hypertrophy — a proportional enlargement of the heart chambers with modest wall thickening — allowing the heart to pump more blood per beat (increased stroke volume) with less effort. This remodeling is adaptive and associated with improved exercise capacity and lower resting heart rates.
• Ventricular function: Trained hearts generally show improved diastolic filling (the ability to relax and accept blood), better contractile efficiency, and often enhanced cardiac output during exercise. These functional changes underpin improved stamina and recovery.
• Calcium handling: At the cellular level, contraction and relaxation depend on precise calcium movement. Exercise training modifies the expression and activity of proteins that control calcium influx, release, reuptake and extrusion (for instance, SERCA2a, phospholamban). These shifts make each heartbeat more efficient and reduce the risk of arrhythmias.

Blocking any of these adaptations can blunt the cardiovascular benefits normally gained from aerobic training. The Dalhousie study reported that sodium nitrate specifically interfered with several of these processes in female mice, thereby preventing the heart from acquiring the improved performance profile typically induced by running.

How dietary nitrates and beetroot supplements are supposed to help

Dietary nitrate (NO3−), abundant in leafy greens and beetroot, follows a biochemical cascade: oral bacteria reduce nitrate to nitrite (NO2−), and nitrite is further reduced to nitric oxide (NO) under conditions such as low oxygen or acidic pH. NO mediates vasodilation by relaxing smooth muscle in blood vessels and influences mitochondrial efficiency and muscle contractility.

Observed benefits in human studies — generally with acute or short-term supplementation — include:

• Improved exercise economy: Lower oxygen cost for a given workload in some endurance protocols.
• Enhanced time-to-exhaustion and steady-state performance in certain athletes.
• Lower resting or exercise blood pressure in hypertensive or normotensive individuals.
• Possible reductions in the oxygen cost of submaximal exercise, making prolonged efforts easier for some users.

These effects underpin the growing commercial market for beetroot and nitrate products aimed at athletes. Manufacturers often position these supplements as legal, nutritional ergogenic aids that support performance and cardiovascular health.

Why the Dalhousie results challenge assumptions about chronic supplementation

Most human research has focused on short-term or single-dose nitrate administration: a pre-race beetroot shot, or supplementation over a few days or weeks. The Dalhousie study tested chronic supplementation in the context of repeated exercise sessions over time. Two implications arise:

1. Acute versus chronic effects may differ. A single dose can transiently increase NO bioavailability and enhance performance. Chronic exposure might alter cellular signaling or feedback systems, producing different outcomes. The Dalhousie results illustrate that chronic nitrate exposure can interfere with the physiological signaling pathways that drive long-term remodeling.
2. Interaction with adaptive signaling from exercise can be complex. Exercise activates numerous molecular pathways (e.g., AMP-activated protein kinase, PGC-1α, nitric oxide synthases) that coordinate remodeling. Introducing persistent exogenous nitrate-derived NO may shift the balance of these pathways, blunt necessary oxidative or redox signals, or alter calcium-handling regulation. The end result observed in female mice was a failure to realize exercise-induced cardiac benefits.

These complexities highlight that supplements cannot automatically be assumed to amplify exercise benefits. Some agents may help acute performance while impairing long-term adaptation.

Why female hearts responded differently: potential mechanisms

Sex differences in cardiovascular biology are well-documented. Females and males display distinct baseline physiology and divergent responses to stressors, hormones and pharmacologic agents. Several plausible mechanisms could explain why sodium nitrate blocked cardiac adaptations in female mice but not in males.

• Hormonal interactions: Estrogen modulates nitric oxide synthase (NOS) expression and NO signaling. Exogenous nitrate supplementation may interact with estrogen-mediated pathways in ways that alter signaling cascades crucial for remodeling. For example, estrogen enhances endothelial function and NO bioavailability; adding exogenous sources could create feedback that reduces endogenous adaptive signaling.
• Redox balance and reactive species: NO and derivative reactive nitrogen species can have both signaling and damaging roles depending on concentration, timing and cellular context. Females and males display differences in antioxidant systems and redox regulation. Chronic nitrate may shift redox balance differently in females, impairing the redox-sensitive signaling that coordinates structural and functional remodeling.
• Calcium handling regulation: The study found changes in calcium handling in female hearts. Hormones and sex-specific protein expression patterns influence calcium-handling proteins. If chronic nitrate alters phosphorylation states or expression levels of SERCA, phospholamban, or ryanodine receptors differently in females, that could explain impaired contractile adaptation.
• Metabolic substrate use: Training induces shifts in substrate utilization (fatty acids versus glucose) and mitochondrial adaptations. NO signaling influences mitochondrial biogenesis and efficiency. Sex-specific differences in these metabolic pathways may lead to divergent responses when external nitrate is introduced.

At present, these mechanisms remain hypotheses. The Dalhousie paper presents robust phenotypic findings but is not designed to establish definitive molecular causation. The observed sex differences strongly argue for targeted mechanistic follow-up that disaggregates male and female biology.

Broader context: how sex has been overlooked in preclinical and clinical research

Historically, both animal and human research have favored male subjects or failed to disaggregate results by sex. Regulatory and policy shifts have improved inclusion, but gaps remain. The consequence is an incomplete understanding of how drugs, supplements and interventions perform across sexes.

Examples from medicine illustrate the stakes: drugs later found to have different efficacy or safety profiles in women often lacked early sex-specific testing. Cardiovascular disease itself presents differently in women — symptoms, pathophysiology and outcomes can vary — yet guidelines and therapies were long based predominantly on male cohorts.

The Dalhousie study joins a growing list of research that demonstrates sex-specificity in physiological responses. For supplements consumed widely by both sexes, sex-stratified data are essential for safe and effective recommendations.

What this means for athletes, recreational exercisers and clinicians

Immediate practice changes are not warranted solely on the basis of this mouse study. However, the findings should prompt caution and inform conversations between athletes, coaches, and healthcare providers.

Points to consider:

• Evidence gap: Mouse physiology differs from human physiology. Dose translation, metabolism, exercise patterns and myocardial responses are not identical. Human trials are required to determine whether comparable effects occur in women who use nitrate supplements chronically while training.
• Acute versus chronic use: Current evidence for performance benefits comes mostly from short-term administration. If chronic nitrate blunts adaptive remodeling in humans, athletes relying on daily high-dose products might sacrifice long-term cardiovascular gains for transient performance enhancements.
• Sex-specific risk-benefit calculus: Women may require different dosing strategies or periodic breaks from supplementation if human studies confirm similar effects. Clinicians and coaches should avoid one-size-fits-all advice.
• Medical interactions and contraindications: Individuals taking blood-pressure medications, especially nitrates or phosphodiesterase type 5 inhibitors, should exercise caution. Although dietary nitrates are not pharmacologic nitrates like nitroglycerin, they influence NO pathways and can affect hemodynamics. Clinical oversight is recommended for people with cardiovascular disease or those on vasoactive drugs.
• Whole-food versus concentrated supplements: Dietary sources of nitrate (vegetables like beetroot, spinach, arugula) come with fiber, antioxidants and a broader nutrient matrix. It is plausible that the physiological effects of whole foods differ from concentrated supplement formulations. Current findings do not directly compare food sources with supplements.

Clinicians should discuss supplement use with patients who train regularly. Questions about dose, duration, and purpose of supplementation, along with underlying cardiovascular risk, should guide individualized advice.

Regulatory and commercial background: how nitrate products reached athletes

Beetroot juice and concentrated nitrate supplements reached mainstream sports nutrition through a combination of laboratory evidence and marketing. Early human studies reported modest improvements in submaximal endurance and reductions in oxygen cost after acute dosing. Those signals appealed to athletes seeking legal, nutritional ergogenic aids.

The supplement industry expanded rapidly. Compared to pharmaceutical interventions, dietary supplements operate under different regulatory frameworks in many jurisdictions. Claims often focus on performance support rather than therapeutic effects, which permits broad marketing without the same premarket evidence standards required for drugs.

Consumers interpret marketing in various ways. Some athletes use nitrate products strategically — for races or time trials — rather than daily. Others consume them habitually as part of training programs. The Dalhousie study speaks most directly to the latter practice and suggests a need to reassess how chronic supplementation interacts with adaptive physiology.

Manufacturers and regulators should promote balanced messaging: acute ergogenic potential does not guarantee long-term safety or additive health benefits when combined with repeated exercise.

Limitations of the Dalhousie study and what it cannot tell us

Skepticism and caution are appropriate because animal models provide important but limited insights. Key limitations to consider:

• Species differences: Mice have faster heart rates, different cardiac energetics and distinct nitrate metabolism compared with humans. Translating dose and exposure from mice to humans is not straightforward.
• Exercise model: Voluntary wheel running in mice approximates aerobic exercise but differs qualitatively from structured human training in intensity, duration and behavioral context.
• Dose and formulation: The study used sodium nitrate in drinking water. Commercial beetroot products vary widely in nitrate concentration and include other bioactive phytochemicals that may modulate effects.
• Chronology and duration: The timing of supplementation relative to training and the duration of exposure may influence outcomes. Human athletes adopt diverse supplementation schedules — occasional, pre-event, or continuous — that were not individually tested here.
• Mechanistic detail: The study identifies physiological disruptions but does not fully elucidate the molecular steps by which nitrate interferes with remodeling in female mice. That requires additional mechanistic experiments.

These limitations mean the study raises a red flag rather than a ban. Human trials that mirror real-world patterns of use and stratify by sex are the essential next step.

What the next research agenda should include

To move from an important preclinical finding to actionable human guidance, researchers should prioritize:

• Randomized controlled trials in humans with sex-disaggregated endpoints. Trials should include both acute and chronic supplementation arms and enroll sufficiently large and diverse samples.
• Dose-ranging studies to determine whether lower, intermittent or strategically timed nitrate intake avoids interference with training adaptations while preserving acute ergogenic benefits.
• Mechanistic investigations in human tissue or advanced models to trace how chronic nitrate exposure affects signaling pathways governing remodeling, redox balance and calcium handling, with attention to hormonal milieu.
• Comparative studies of whole-food versus concentrated supplement sources to assess whether the nutrient matrix alters outcomes.
• Longitudinal monitoring of athletic populations who use nitrate products habitually, including cardiac imaging (echocardiography, MRI) and functional testing to detect subtle remodeling differences over time.
• Studies that examine interaction with common medications (antihypertensives, PDE5 inhibitors) to clarify safety profiles for people with cardiovascular conditions.

Funding agencies, journals and industry stakeholders should incentivize sex-specific research and require reporting of sex-stratified results to avoid future blind spots.

Practical guidance for athletes, coaches and clinicians today

Pending human data, practical recommendations should balance existing evidence of acute benefits against the possibility of unwanted chronic effects in females. Suggestions for different stakeholders:

• Recreational exercisers and athletes who use nitrate supplements regularly: Consider temporary moderation. Using nitrate products strategically for specific events rather than daily may preserve acute performance benefits while limiting prolonged exposure. Discuss individual use with a sports physician or registered dietitian.
• Female athletes: Be aware that preclinical data indicate a potential for suppressed cardiac adaptation. If training goals prioritize long-term cardiovascular resilience and heart health, conservative use or periodic breaks from chronic supplementation is reasonable until human evidence clarifies risk.
• Male athletes: Current animal data suggest fewer adverse cardiac effects, but human confirmation is lacking. Risk-benefit assessments should still be individualized.
• Clinicians: Ask patients about supplement use, including nitrate products. Assess cardiovascular risk, medication interactions and training practices before making recommendations. For patients on vasoactive agents, a cautious approach is warranted.
• Coaches and sports scientists: Monitor athletes’ training adaptations over time. If an athlete using nitrate supplements shows unexpected plateaus in performance measures or signs of maladaptive cardiac changes (e.g., atypical symptoms, arrhythmias, abnormal echocardiography), reevaluate supplement use in collaboration with medical staff.
• General public: Dietary nitrate from vegetables remains a component of a healthy diet. Current concerns center on concentrated and chronic supplementation used as a performance aid. Prioritizing a balanced diet rich in leafy greens and beets supplies nitrates alongside vitamins and antioxidants, which may influence physiological responses differently than single-ingredient supplements.

These recommendations are pragmatic and provisional. They aim to protect long-term cardiac adaptation while acknowledging documented short-term performance effects.

Real-world examples and context

Professional and amateur athletes take decisions about supplementation in high-stakes environments. Examples from the sports world illustrate practical diversity:

• Elite cyclists: Some Grand Tour teams have experimented with beetroot products to reduce oxygen cost during long stages. Use tends to be strategic — pre-race or during multi-day efforts — rather than continuous daily dosing.
• Recreational runners: Many recreational runners use beetroot juice regularly in training, believing it aids recovery and performance. If chronic intake blunts cardiac adaptations, these users may unintentionally sacrifice long-term gains.
• Masters athletes and aging exercisers: For older adults with cardiovascular risks, acute blood-pressure-lowering effects of dietary nitrates can be beneficial. Yet caution is necessary if chronic nitrate interferes with heart remodeling that supports resilience.

Real-world decision-making rarely aligns perfectly with evidence. Athletes often rely on coaching, tradition, and perceived short-term gains. The new animal data encourage re-evaluating customary practices and underscore the need for tailored strategies.

Safety considerations and interactions

While dietary nitrates are not identical to medicinal nitrates like nitroglycerin, they influence the NO pathway and can affect blood pressure and vascular function. Safety points include:

• Potential for hypotension: Individuals on antihypertensive medications or vasodilators may experience additive blood-pressure effects. Medical supervision is advisable when combining supplements with prescribed therapies.
• Drug interactions: PDE5 inhibitors (e.g., sildenafil) and certain nitrates carry a risk of severe hypotension when combined. While dietary nitrate is not directly equivalent, patients should disclose supplement use and consult prescribers.
• Oral microbiome role: Reduction of nitrate to nitrite depends on oral bacteria. Antibacterial mouthwashes can reduce this conversion and alter the expected physiological effects. This interplay complicates dosing predictability.
• Gastrointestinal tolerance: Beetroot products can cause beeturia (red urine), gastrointestinal discomfort or transient changes in stool color. These effects are benign but can be alarming to users.
• Long-term safety: Chronic high-dose nitrate intake has not been evaluated comprehensively in humans for long-term cardiovascular outcomes. The Dalhousie study suggests the need to examine potential adverse remodeling effects, especially in women who exercise regularly.

Clinicians should track supplement use as part of routine health assessments and discuss potential interactions.

Communication and messaging: how to translate the evidence

Accurate, balanced messaging must reflect nuance: nitrates have demonstrated acute ergogenic and blood-pressure-lowering effects in many short-term human studies, but a new preclinical finding reveals possible interference with long-term cardiac adaptations in female mice. Messaging strategies should:

• Avoid absolutist claims: Do not declare supplements categorically “safe” or “dangerous” without adequate human data.
• Highlight uncertainty and next steps: Explain the preclinical nature of the findings while calling for targeted human research.
• Tailor advice: Recognize that risk tolerance and goals differ across athletes, clinicians and recreational exercisers.
• Encourage shared decision-making: Athletes and patients should weigh immediate performance objectives against long-term health priorities in consultation with medical professionals.

Clear, sex-aware communication will minimize confusion and support informed choices.

Research ethics and industry responsibility

Supplement producers have an ethical stake in funding and supporting rigorous research that clarifies long-term effects and sex-specific responses. Industry commitments could include:

• Sponsoring trials with transparent design and sex-stratified reporting.
• Supporting independent research and data-sharing.
• Advertising responsibly, aligning claims with evidence and limitations.

Regulators and professional sports organizations can encourage evidence-based use by promoting labeling clarity and supporting research initiatives.

Final reflections before the FAQs

The Dalhousie study reframes a familiar story: a compound with acute benefits does not necessarily enhance long-term physiological adaptation. The sex-specific nature of the findings places an obligation on the scientific community, clinicians and athletes to demand human data that disaggregate by sex and examine chronic use patterns. Until those data arrive, measured, individualized approaches to nitrate supplementation are prudent.

FAQ

Q: Should women stop taking beetroot juice or sodium nitrate supplements immediately? A: Immediate cessation is not mandated by the current evidence. The study used a mouse model and cannot be directly translated to humans without further research. However, women who take nitrate supplements daily may consider reducing chronic use or using supplements strategically (e.g., occasional pre-event dosing) while awaiting human data, and should discuss concerns with a healthcare professional.

Q: Are males at risk of the same effects? A: The Dalhousie study found minimal cardiac interference in male mice under the tested conditions. That suggests risk may be sex-specific in this model, but human studies are necessary to determine whether males are similarly unaffected or display subtler responses.

Q: Does this affect dietary nitrate from vegetables like spinach or beets? A: The study used sodium nitrate, not whole foods. Whole vegetables include antioxidants, fiber and other phytochemicals that may modulate physiological effects. Until direct comparisons are performed, emphasizing a balanced diet rich in vegetables remains advisable.

Q: Can nitrate supplements be used safely for acute performance benefits? A: Short-term and acute use has evidence supporting modest performance benefits in some contexts. Strategic, intermittent use for competitions rather than continuous daily supplementation may preserve acute benefits while potentially reducing long-term risks suggested by animal data. Individual tolerance and medical history should guide decisions.

Q: Do nitrates interact with medications? A: Yes. Nitrates can affect blood pressure and interact with vasodilators or PDE5 inhibitors, potentially causing hypotension. Individuals on cardiovascular medications should consult their healthcare provider before using nitrate supplements.

Q: How much more research is needed? A: Human randomized controlled trials that specifically compare chronic versus acute supplementation, stratify by sex, examine a range of doses and formulations, and include cardiac imaging and cellular biomarkers are essential. Longitudinal observational studies of habitual supplement users would also be valuable.

Q: What markers should clinicians monitor if a patient uses these supplements? A: Clinicians could monitor blood pressure, heart rate, exercise capacity, and consider periodic cardiac imaging (echocardiography) in athletes using chronic, high-dose supplements — especially if symptoms or performance plateaus arise. Assessment of medication interactions and review of dosing patterns are also important.

Q: If an athlete wants short-term performance help but avoid potential long-term issues, what is a reasonable approach? A: Using nitrate supplements selectively for key competitions rather than every training day is a conservative strategy. Incorporating whole-food sources of nitrate intermittently, ensuring adequate recovery, and focusing on training principles that promote healthy cardiac remodeling may offer a balanced path.

Q: How should researchers incorporate these findings into study design? A: Future trials should pre-specify sex-stratified analyses, include chronic dosing arms, measure structural and cellular cardiac endpoints, and account for variables like diet, oral microbiome status, and concurrent medications. Transparent reporting and publicly available data will accelerate understanding.

Q: Where can athletes find reliable guidance about supplements? A: Seek advice from sports physicians, registered dietitians specializing in sports nutrition, and evidence-based resources from professional sports organizations. Beware of marketing that overstates benefits and minimize reliance on anecdotal reports.

The Dalhousie study offers a cautionary example: an intervention that appears straightforward and beneficial in the short term may have counterintuitive effects on long-term adaptation, and those effects can differ by sex. Athletes and clinicians should treat supplemental nitrates as a tool that requires strategic use and further study, not as an unqualified enhancer of cardiovascular health.