Vitamin A in Athletes: What the Evidence Actually Says About Performance, Immunity, and Supplementation
Table of Contents
Introduction: Why Vitamin A in Athletes Deserves More Attention
In clinical practice, vitamin A is often overlooked by both clinicians and patients. Among patients, it is generally not a particularly well-understood vitamin, and even among clinicians there is often a somewhat cautious or negative association with vitamin A. Part of this stems from its well-established teratogenic potential during pregnancy. In addition, retinoid-based medications — such as those commonly used for acne treatment — are known for significant teratogenic risk and can also contribute to elevations in liver enzymes, which is why they are prescribed and monitored carefully. Vitamin A is also a fat-soluble vitamin, meaning that unlike many water-soluble nutrients it can accumulate in body stores over time, raising concerns about excessive intake and toxicity with prolonged high exposure.
Vitamin A is the generic name of a mixture of vitamers, also known as retinoids (retinol, retinal, and retinoic acid), that show the biological activity of retinol [1]. Athletes are often exposed to increased oxidative stress, higher metabolic turnover, and greater nutritional demands, which can potentially lead to deficiencies in vitamins [2]. Yet peer-reviewed RCT evidence on vitamin A specifically in athletes remains sparse — a recent decade-spanning narrative review identified fewer than ten RCTs examining vitamin A in athletic populations [2]. That data gap matters enormously, because what early research does show cuts in both directions: adequate vitamin A status appears important for immune integrity and energy metabolism, but supplementation in athletes with sufficient status may carry meaningful risks.
In this article, I’ll go through the current evidence on vitamin A in athletes — exploring its physiological role, who may be at risk of deficiency, and why routine preformed retinol supplementation is more complicated than many people realize
What Vitamin A in Athletes Actually Does: Core Physiology
Vitamin A is involved in immune function, cellular communication, growth and development, and reproduction [3]. In the athletic context, vitamin A in athletes encompasses several specific mechanisms that matter for performance and health.
Immune Modulation
Retinoic acid (RA), a major oxidative metabolite of vitamin A, plays a key role in the differentiation of T cell subsets, the migration of T cells into tissues, and the proper development of T cell-dependent antibody responses [4]. RA also promotes the differentiation of regulatory T cells, which help to suppress inflammatory reactions, and plays a significant role in normal mucosal immunity by modulating T cell activation and regulating cell trafficking [4]. In a state of vitamin A deficiency, inflammatory T cell reactions may be inadequately opposed and therefore become dominant [4].
These mechanisms are relevant background for athletes, as heavy training loads are associated with increased infection burden — though it should be noted that the older model of “post-exercise immunosuppression” has been questioned. A contemporary view is that immune resistance is not suppressed in athletes under heavy training, and that the relevant nutritional focus is on tolerogenic rather than immunostimulatory interventions [9].
That said, in clinical practice, the immunomodulatory aspect of vitamin A is largely more of a physiological curiosity than a routine clinical concern. Vitamin A concentrations are not typically measured as part of standard blood work, and deficiency is rarely considered a first-line explanation for immune-related symptoms. In everyday clinical practice, vitamin A deficiency is seldom among the primary suspected causes when evaluating impaired immunity or recurrent infections.
Antioxidant Defence and Mitochondrial Function
Vitamin A belongs to a group of antioxidant vitamins — substances capable of neutralizing free radicals that are produced during intense physical exercise [1]. An adequate intake of vitamin A contributes to the elimination of reactive oxygen species (ROS) [1]. Moreover, since exercise also increases the generation of reactive oxygen species, vitamin A stabilizes cell membranes and interacts with antioxidants, such as vitamin C in athletes and vitamin E in athletes, to reduce oxidative stress [2].
Vitamin A has been linked to muscle repair, mitochondrial biogenesis, and protein synthesis [2], although direct athlete-specific intervention evidence on these endpoints remains limited.
Energy Metabolism
In carbohydrate metabolism, vitamin A status influences insulin sensitivity and glucose transport; deficiencies have been linked to impaired gluconeogenesis and dysregulated blood glucose levels [2] — a relevant consideration for athletes in calorically restrictive phases, such as those preparing for weight-class competition, whose incidental intake of fat-soluble vitamins may be significantly reduced. For a broader overview of how micronutrient deficiencies affect athletic performance, see vitamins for athletes.
As a general rule, athletes are not considered a high-risk population for vitamin A deficiency or for the clinical syndromes associated with it. In everyday clinical practice, there is usually little rationale for routinely measuring vitamin A levels in athletes who consume a normal, balanced diet. Unless there are specific concerns — such as restrictive eating patterns, malabsorption disorders, or other clinical indicators of deficiency — routine vitamin A testing is generally unlikely to add meaningful information.
Who Is at Risk for Inadequate Vitamin A in Athletes?
Frank vitamin A deficiency is uncommon in well-nourished athletes in affluent countries. Evidence of vitamin A and E deficiencies in athletic individuals is lacking apparently because body storage is appreciable [5]. The liver stores vitamin A as retinyl esters — a substantial buffer that water-soluble micronutrients simply do not have. (The liver’s central role in vitamin A metabolism is also why liver enzymes in athletes can occasionally provide indirect context for fat-soluble vitamin assessment.)
However, certain athletic subpopulations face elevated risk of inadequate vitamin A intake. Young girls and individuals participating in activities with weight classifications or aesthetic components are prone to nutrient deficiencies because they restrict food intake and specific micronutrient-rich foods [5]. Fat-soluble vitamin intake is particularly vulnerable to low-fat or energy-restricted dietary patterns.
Dietary reference intakes for athletes are not differentiated from those for the general population [2], meaning there are no sport-specific RDA values. The established RDA for vitamin A is 900 µg retinol activity equivalents (RAE) per day for adult males and 700 µg RAE per day for adult females [3]. Beef liver (pan-fried, 85 g) provides 6,582 µg RAE [3] — meaning most well-nourished athletes eating varied diets including animal products, eggs, dairy, and orange or dark green vegetables will meet this threshold without difficulty.
A recent review emphasized that athletes with high training loads should pay attention to adequate vitamin A intake, particularly when energy or dietary fat intake is restricted [2]. In my own clinical practice, I would frame this more simply: the priority is not to chase vitamin A numbers, but to make sure the athlete is eating a varied, balanced diet. I do not routinely measure vitamin A in athletes who have a normal diet, and I do not generally recommend vitamin A supplementation without a clear clinical reason. If an athlete develops vitamin A deficiency, I would usually look for an underlying explanation — such as restrictive eating, very low dietary fat intake, malabsorption, or another clinical risk factor — rather than attributing it to athletic status itself. Being an athlete, on its own, is not a reason to screen for vitamin A deficiency.
Vitamin A in Athletes and Supplementation: Where the Evidence Gets Uncomfortable
Here is where the narrative around vitamin A in athletes shifts significantly — and where many sports nutrition discussions fall short of the evidence.
No Support for Performance Enhancement
The current limited evidence available does not appear to support beneficial effects of chronic supplementation with either preformed vitamin A (e.g. retinol) or β-carotene on systemic markers of exercise-induced oxidative stress [6]. This is a key finding that sets vitamin A apart from other commonly supplemented micronutrients.
Potential to Impair Training Adaptations
More provocatively, in rodents, chronic supplementation with retinyl palmitate in combination with exercise training increased skeletal muscle oxidative stress and decreased exercise-induced induction of endogenous antioxidant enzymes [6]. This finding implicates an impairment in exercise-induced antioxidant adaptations in skeletal muscle with exogenous vitamin A [6].
A separate rodent study — where animals were submitted to intense swimming five times per week alongside a daily vitamin A intake — found that vitamin A supplementation impaired the total serum antioxidant capacity acquired by exercise. In skeletal muscle, vitamin A caused lipid peroxidation and protein damage. Furthermore, vitamin A supplementation decreased anti-inflammatory interleukin-10 and heat shock protein 70 expression — important factors for positive exercise adaptations and tissue damage prevention [7]. These findings are from animal models and have not yet been replicated in human athletes, but the mechanistic implications are relevant to the broader discussion.
The principle behind both findings is the same one that applies to other antioxidant supplements, including vitamin C in athletes and vitamin E in athletes: exercise-induced ROS participate in redox signalling involved in mitochondrial biogenesis and endogenous antioxidant enzyme induction; some antioxidant strategies may interfere with selected adaptations [6].
There is a notable lack of studies investigating effects of vitamin A or β-carotene on either exercise performance or skeletal muscle mitochondrial biogenesis in both humans and animals [6]. The current evidence base cannot support routine preformed retinol supplementation for vitamin A in athletes without a confirmed deficiency.
In general clinical practice, excessive antioxidant intake is not usually considered a decisive factor in athletic performance. From my perspective, most athletes do not need to worry about getting “too much” vitamin A if they eat a balanced diet, avoid high-dose vitamin A supplements, and do not consume liver very frequently. The main concern is not normal dietary intake, but prolonged high exposure to preformed vitamin A from supplements or unusually high intake of liver.
Vitamin A in Athletes and Bone Health: A Clinically Underappreciated Risk
A clinically important concern for athletes is the relationship between excess preformed vitamin A and bone health — a risk rarely discussed in sports nutrition contexts but relevant for high-volume training populations.
A review of the current evidence describes that increased dietary retinol intake was associated with reductions in bone mineral density (BMD) at the femoral neck, Ward’s triangle, trochanter region of the proximal femur, lumbar spine, and total body [8]. Some observational studies have linked higher retinol intake with elevated fracture risk, though findings across studies are not fully consistent [8].
This bone health concern is particularly relevant to consider alongside calcium in athletes, where the interplay between nutrients and bone integrity is central to fracture prevention and stress fracture management.
It is critical to note that these concerns apply specifically to preformed retinol (from animal sources and supplements), not to provitamin A carotenoids from plant foods. Unlike preformed vitamin A, no Tolerable Upper Intake Level has been set for beta-carotene and other provitamin A carotenoids [3]. A review of provitamin A data also suggests that carotene and β-cryptoxanthin may promote osteogenesis and inhibit osteoclastic bone resorption via retinoic acid receptor signalling, with postmenopausal women in the highest quintile for β-carotene and β-cryptoxanthin showing lower risk of osteopenia [8].
In clinical practice, the potential relationship between high vitamin A intake and bone density is usually a relatively minor consideration compared with vitamin D status and overall calcium intake. For most athletes and patients, I would not consider vitamin A a primary bone health concern unless there is clear prolonged excess intake, such as high-dose retinol supplementation or very frequent liver consumption. From a bone density perspective, vitamin D status, calcium intake, energy availability, and overall training load are usually much more clinically relevant targets.
Assessing Vitamin A Status in Athletes: What Blood Work Tells You
In clinical practice, plasma retinol levels can be used to document significant deficiency. A serum or plasma retinol concentration of 20 mcg/dL (0.70 micromoles/L) or less frequently reflects moderate vitamin A deficiency, and a level of 10 mcg/dL (0.35 micromoles/L) or less is considered an indicator of severe vitamin A deficiency [3].
However, serum retinol is not always a reliable indicator of vitamin A status, because levels do not decline until liver and other storage sites are almost depleted, and because acute and chronic infections can decrease serum and plasma retinol concentrations [3]. This is a particularly important clinical nuance: an athlete presenting during a period of recurrent upper respiratory infections may show suppressed serum retinol that does not reflect true whole-body vitamin A stores. Clinical interpretation always requires integration with dietary history, training load, and the full clinical picture — the same principle that applies to cortisol in athletes, testosterone in athletes, and many other markers whose context-dependence is frequently underappreciated.
In everyday clinical practice, vitamin A is very rarely measured at all. Its deficiency states are not something most clinicians commonly encounter, and athlete status alone is not a specific reason to test vitamin A. In practice, vitamin D status is usually far more relevant, especially in Finland, where deficiency is genuinely common.
Personally, I cannot recall a single case over the past ten years in which a patient clearly suffered from clinically meaningful vitamin A deficiency. This may partly reflect the fact that vitamin A is rarely tested, but in most real-world situations, a patient with true vitamin A deficiency would likely have broader dietary, gastrointestinal, or nutritional problems that would become clinically apparent first and require more urgent attention.
For this reason, I do not see routine vitamin A testing as important for athletes, nor do I think most athletes need to specifically optimize or supplement vitamin A intake. For the vast majority, a varied and balanced diet is enough.
Conclusion: What Vitamin A in Athletes Actually Means for Practice
Vitamin A in athletes is an interesting topic physiologically, but in everyday clinical practice it is usually not one of the most important micronutrients to chase, measure, or optimize. Vitamin A clearly has roles in immune regulation, antioxidant defence, cellular function, and energy metabolism, and deficiency can matter in specific clinical contexts. However, for most well-nourished athletes eating a varied diet, true vitamin A deficiency appears uncommon, and athlete status alone is not a strong reason to measure serum vitamin A or to start supplementation.
The more practical message is moderation. Normal dietary intake from a balanced diet — including eggs, dairy, fish, vegetables, and occasional animal sources — is usually enough. At the same time, high-dose preformed retinol supplementation is not supported as a performance-enhancing strategy and may carry unnecessary risks, particularly with prolonged intake or when combined with frequent liver consumption. The available evidence does not justify routine vitamin A supplementation in non-deficient athletes, and the animal data on antioxidant adaptation provide another reason to avoid unnecessary high-dose use.
From my perspective, vitamin A should be interpreted in context rather than treated as a performance target. If an athlete has restrictive eating patterns, very low dietary fat intake, malabsorption, recurrent nutritional deficiencies, or other clinical risk factors, then vitamin A status may deserve attention. But for the vast majority of athletes, the goal is simple: eat a varied, balanced diet, avoid unnecessary high-dose retinol supplements, and focus clinical attention on more common and actionable issues such as vitamin D status, calcium intake, energy availability, sleep, recovery, and the overall quality of the diet
Bibliography
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC8834970/
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC12845069/
[3] https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
[4] https://pmc.ncbi.nlm.nih.gov/articles/PMC3471201/
[5] https://pubmed.ncbi.nlm.nih.gov/15212745/
[6] https://pmc.ncbi.nlm.nih.gov/articles/PMC7284926/
[7] https://pubmed.ncbi.nlm.nih.gov/28368329/
