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Subjects:
Nutrition & Dietetics
To examine the effects of micronutrient intake on athletic performance and (ii) to determine the specific micronutrients, such as vitamins, minerals, and antioxidants, that offer the most significant enhancements in terms of athletic performance, with the goal of providing guidance to athletes and coaches in optimizing their nutritional strategies.
- vitamins
- minerals
- sport
- performance
1. Introduction
Optimal performance is a primary objective for many athletes, and this can be attained by following a suitable exercise protocol and ensuring proper nutrition [1]. Food is composed of nutrients that are essential for growth, repair, and energy generation depending on the amount that meets the body’s need [2]. Nutrients are typically categorized into two main groups: micronutrients and macronutrients [3]. When it comes to athletic performance, the importance of micronutrients should not be neglected [4]. Athletes are prone to consuming insufficient amounts of micronutrients due to inappropriate dietary habits, especially if they are not matching their physical activity requirements [5]. By making sure they are receiving adequate levels of micronutrients, athletes can give themselves a competitive edge and maximize the potential of their training [6]. Micronutrients may boost mental performance, help balance hormones, and keep cognitive performance at its peak [7].
2. Vitamins
Vitamins are organic essential compounds that cannot be synthesized by the human body [29]. They play a vital role in numerous functions that are relevant to the athlete’s performance [7]. Their functions are evident in co-enzymes, hormones, and autoxidation, as well as their contribution to energy production [242]. There are thirteen various kinds of vitamins currently divided into two major groups due to their chemical and biological functions, four of which are fat-soluble vitamins (FSV) including vitamins A, D, E, and K, and the rest are water-soluble vitamins (WSV) including B complex vitamins and vitamin C [243].
3. Fat-Soluble Vitamins (FSV)
Vitamin A
Vitamin A plays a significant role in promoting the overall wellbeing of athletes, as it aids in the formation of healthy tissues and improves oxygen access throughout the body, thereby supporting the maintenance of an adequate level of physical activity [3]. It also has a crucial influence on vision, skin health, and immune system functioning [29]. Moreover, vitamin A is a potent antioxidant that helps in neutralizing free radicals generated by oxidative stress during advanced physical training.
Vitamin A mainly exists in two forms: animal source (retinol) and plant-based provitamin A (carotenoids). The intake of sufficient amounts of beef liver, eggs, dairy products, and seafood as well as dark leafy green vegetables may ensure meeting the dietary requirements for athletes. It is noteworthy that athletes may benefit from supplementation with multivitamins that contain vitamin A, as a part rather than its own sole use [29].
Vitamin A has been proved to enhance and support various body functions, including reaction time, muscles recovery [245,246], and protein synthesis, which is essential for muscle growth and recovery and can be important for those competing in events requiring fast reflexes [247]. Furthermore, vitamin A can help protect athletes against injuries by increasing healing times and promoting the formation of healthy connective tissues [3]. Finally, vitamin A may help fight off colds, flu, and other illnesses, which can be particularly helpful for traveling athletes.
To evaluate the effect of crocetin on fatigue, a study test was conducted by athletes to measure stamina using a bicycle ergometer at a standard workload for 120 min twice. They also performed non-workload tests of 10 s at 30 min at a maximum velocity (MV) [242]. A difference in MV from 30 to the 210 min test was remarkably reported only in men who consumed crocetin when compared to their counterpart who used a placebo (p < 0.05) [248]. No difference was observed with the consumption of ascorbic acid in all candidates with the same period [248]. The daily consumption of crocetin would reduce physical exhaustion in men, according to these results [179]. The attenuating effect of saffron carotenoids on muscle fatigue is due to their provitamin A activity [248]. Athletes should meet their daily recommended intake of vitamin A to guarantee a perfect peak physical condition [249].
The Recommended Dietary Allowance (RDA) of retinol activity equivalents (mcg RAE), is 900 micrograms for men aged 19 years old and older, equal to 3000 international units (IU), and 700 mcg RAE for women aged 19 years old and older, equivalent to 2333 (IU). However, the adherence to a maximum Tolerable Upper Limit (UL) of 10,000 IU (3000 mcg)/day for adults is important to avoid any dangerous effect. It is also important to emphasize that toxicity may occur when frequent doses of more than 25,000 IU are taken daily [3].
β-carotene is a member of the carotenoid family that is thought to provide numerous health benefits, including immunity system boosting, antioxidation properties, and performance enhancement [250]. β-carotene is an essential antioxidant, meaning that it helps prevent the harmful effect of free radicals on cells [251]. This is important for athletes, as free radicals are generated during strenuous exercise and can lead to fatigue and soreness [176]. Several studies have reported similar findings, highlighting the ability of vitamin A to potentially reduce recovery time from exercise [7,250]
Sumac juice drink was tested in a study to evaluate its impact on pain scores through post-exercise intervals. Forty healthy candidates involved in an aerobic training protocol for four weeks received a dose of placebo or sumac juice consumption two times/day for a month. The results revealed that participants of the sumac juice group had a lower pain score increment and even a better enhancement during pain relief. The potency of protecting muscles might be due to the sumac juice antioxidant potency of β-carotene-linoleic acid components. These results highlight the possibility of sumac juice consumption in improving muscle performance among athletes [252]. Nevertheless, future studies of athletes are warranted.
Athletes often push their bodies to the limit, therefore compromising their immune systems and making them more susceptible to infections and illness [176]. Taking a supplement with β-carotene may have potential benefits for the immune system, helping to prevent illness and potentially enabling athletes to train harder and longer [250,251]. Apparently healthy nonsmoker adult males were involved in consuming placebo or 15 mg/day of β-carotene for 26 days. After oral administration, significant increases in the monocytes percentage representing the major histocompatibility complex class II molecule human leukocyte antigen DR isotype (HLA-DR) and the adhesion molecules intercellular adhesion molecule-1 and leukocyte function-associated antigen-3 were observed. Furthermore, tumor necrosis factor-alpha (TNF-alpha) was notably elevated due to the dose intake, arguing that a slight increment in the consumption of dietary β-carotene can enhance the responses of immune cells within the short term, supporting the process of the carcinogenic potency [253].
Lastly, β-carotene has been found to improve physical performance [254]. Studies have shown that β-carotene supplementation may lead to endurance strength improvement and injury risk prevention [3,150]. Similarly, a meta-analysis of nine studies including participants from both genders, with a total 190,545 candidates, emphasized that β-carotene leads to a significant enhancement in overall performance [29]. There was a 95% possibility that β-carotene consumption attenuates the possibility of hip fracture and other different fracture types by over 20% [251]. According to research, despite the uncertain effect of the antioxidant’s supplementation, consuming β-carotene and combining antioxidants or not still has an effective impact in reducing exercise-induced peroxidation [33]. This may enhance athletes’ endurance in the long term [251,254,255].
4. Vitamin E
As research progresses, the potential advantages of vitamin E for athletes are becoming increasingly apparent. Vitamin E helps in protecting athletes’ bodies and may improve both performance and recovery [75]. Overtraining and intense exercise are associated with reactive oxygen species (ROSs) production, which aids in enhanced muscular and endurance adaptation to exercise through the upregulation of endogenous antioxidant enzymes [256]. However, excess accumulation of ROS accompanied by the inability of the body to scavenge these compounds is harmful to the body’s cell components which is associated with fatigue, delayed recovery, and reduced performance [257]. Accordingly, research suggests the possible protective effects of vitamin E supplements against chronic stress associated with exercise [257,258]. This vitamin possesses antioxidant properties by neutralizing free radicals, protecting cells and tissues [257,258].
Studies showed controversial results of vitamin E supplementation in athletes [44]. It was shown that vitamin E supplements neither inhibit exercise-induced oxidative stress nor impact endurance running performance [259]. Moreover, these results were supported by the randomized controlled trial on athletic students where vitamin E oral consumption was found to not influence exercise endurance [260]. On the other hand, among healthy individuals, vitamin E (alpha-tocopherol) consumption inhibits the exercise-induced reduction in blood paraoxonase 1/arylesterase activity [6,44,147,260]. Excess doses of supplements have been shown in studies to inhibit the signaling reactions required for adaptations to exercise, creating an interference effect [3].
A meta-analysis revealed that vitamin E supplements have a beneficial and protective effect, particularly at low doses (≤500 IU/day), in reducing biomarkers associated with exercise-induced muscle damage and oxidative stress. Beneficial effects of the antioxidant characteristics of vitamin E were observed among exercise-induced side-effects [257]; both animal and human studies have indicated that Vitamin E has the potential to enhance immune function and provide protection against various infectious diseases [6]. Vitamin E reduces PGE2 production and inhibits COX2 activity, likely by decreasing nitric oxide production [261]. Furthermore, it improves T cells immune synapse formation and activation signals, and lastly, it helps in modulating the T (Th1/Th2) balance [52]. This is particularly beneficial for athletes, who are often susceptible to illness and injury due to the intense physical demands of their sport. By supplementing with vitamin E, athletes can help increase the body’s natural immunity, thus reducing the risk of infection and promoting recovery [262].
Vitamin E may assist in improving blood flow, which is essential for athletes [242]. γ-tocopherol, which is one of the compounds that contain vitamin E, increases cardiovascular functions. γ-tocopherol expands the activity of nitric oxide synthase, which in turn produces nitric oxide, aiding in vessels relaxation and thus improving blood flow [29]. Adequate levels of nutrients and oxygen concentrations in muscles indicate a raised blood flow rate, which may help improve performance [263]. Additionally, vitamin E improves red blood cells’ flow and flexibility [264]. This is important for athletes, as improved blood flow means better performance in delivering nutrients and oxygen to the muscles, allowing them to perform at their best [176].
Free radicals such as superoxide, nitric oxide, and hydrogen peroxide are known to be of significant importance, as there must be a balance between antioxidants and free radicals in order to obtain physiological muscle adaptation in response to exercise [25]. Few studies suggested that antioxidants supplementation may be beneficial under specific circumstances, such as overtraining, high-altitude training, or hypoxic training, and claimed that antioxidant usage such as the intake of vitamin E or vitamin C may have no benefit at all or may even cause harm [6,7,29,176,256]. Misusing or consuming excessive amounts of vitamins can lead to muscle fatigue and impede the recovery process due to the inactivation of the gene expression regulator Nrf2 (Nuclear factor erythroid 2-related factor 2), which plays a role in the response to cellular stress and contributes to enhancing exercise performance [265]. It is worth noting that Vitamin E toxicity may cause increases in mortality risk factors, since there has been a positive relation accompanied by a high-sensitivity C reactive protein indicative of inflammation [266].
5. Vitamin D
Vitamin D plays a cooperative role in the synthesis of various hormones in the body [3]. Dairy products, egg yolk, and fatty fish are the rich dietary intake sources [2]. Moreover, it can be synthesized in vivo and be activated by sunlight within a duration of 15 to 20 min of exposure [44]. It also plays an important role in calcium homeostasis and constant healthy bone [30], functions of improving the immune system, musculoskeletal system, power, and force output [45].
Vitamin D supplementation has been increased among athletes [45]. Unfortunately, the widespread vitamin D insufficiency has been clearly stated in elite male athletes, with evidence of a deficit in women [46]. Percentages of insufficiency in elite athletes were above 50%, and the deficiency in other studies was 70–90%, as reported by Harju et al. [47]. Certain circumstances impact vitamin D status, such as indoor training, pigmented skin, and living in a high-altitude region [48]. Studies have reported that athletes with vitamin D deficiency may experience ergogenic benefits when taking vitamin D supplements [103].
There was a direct relation between the concentrations of vitamin D and athletes’ performance, such as speed, jumps’ height, power muscle tone, and strength of handgrip [50]. Moreover, the addition of calcium to vitamin D supplements exhibited a reduction in the stress fracture rate [106,138].
In a study conducted among 70 athletes randomly assigned for 8 weeks to either vitamin D oral supplements of 50,000 IU/week group or a control group, a significant improvement in the test of the strength leg press in both groups was reported [267]. However, the results emphasized that the enhancement in the supplemented group was obviously more noted than that in the control group (p = 0.034). Moreover, when the sprint test was conducted, within-group enhancement had been noticed in the supplemented group only (p = 0.030). The results showed that regular weekly vitamin D supplementation with a dose of 50,000 IU increased the levels of circulating calcidiol (major circulating form of vitamin D) by approximately 17 ng/mL. This increment was related to a notable enhancement in sprint and power leg examinations in the vitamin D group [138]
Additionally, vitamin D is also thought to improve the body’s utilization of carbohydrates during exercise, providing the body with increased energy, which can help to enhance performance [1]. Twenty-two male adult athletes were allocated into two groups for 8 days: a one-shot dose of 150,000 IU vitamin D group and a placebo group. The vitamin D group showed a significant elevation in muscle power in the period from day 1 up to day 8, suggesting that a single dose of 150 000 IU vitamin D had a beneficial impact on serum 25-hydroxy vitamin D (25(OH)D) levels and the muscle’s role [268].
To maintain sufficient vitamin D levels, the most appropriate way is to spend time in outdoor direct sunlight for several minutes each day, as obviously indicated by many studies’ conclusions. This prescription for sun exposure should also be combined with foods that are rich in vitamin D, such as dairy products, fatty fish, and fortified foods [101]. Additionally, athletes may also benefit from daily multivitamin supplements that contain vitamin D to ensure that their body receives the best possible nutrition. The recommended daily dose of vitamin D, varies depending on age; a daily dose of 600 IU (equivalent to 15 micrograms (mcg)) is considered sufficient for the age of 19 and above in both genders, and for adults over 70 years old, an 800 IU (20 mcg) daily dose would be sufficient [7,25]. Vitamin D-deficient athletes would require 50,000 IU of vitamin D per week for 8 weeks [138,258].
A previous study was conducted for 12 weeks among 53 youth athlete swimmers who suffered from insufficient levels of vitamin D to evaluate the influence of vitamin D oral supplementation on physical performance by taking 2000 IU/day of vitamin D or placebo. No notable difference was observed in performance between the supplemented and placebo groups [269]. The results concluded that there was no remarkable correlation found between Vitamin D levels and the evaluated criteria including strength or swimming performance and even the age-adjusted balance. Although the oral administration of vitamin D had raised the concentration of Vitamin D compared to the placebo group, no significant physical performance enhancement was reported [269].
6. Vitamin K
Vitamin K is essential for blood coagulation [163]. It may also impact bone metabolism in postmenopausal women, according to a few previous studies [3,7,270]. In elite female athletes, the oral intake of vitamin K at a dose of 10 mg/day has been shown to improve bone remodeling [254] by increasing the calcium-binding capacity of osteocalcin, promoting bone formation, and reducing bone resorption [176]. Moreover, the intake of vitamin K improved cardiovascular function [18,231].
7. Water-Soluble Vitamins (WSV)
Vitamin B
B-complex vitamins are essential for athletes to maintain optimal health and performance [19]. B-complex vitamins help athletes manage stress and anxiety, aid in muscle recovery, and reduce fatigue, which may adversely affect performance if left unchecked [2]. B-complex vitamins help in blood pressure regulation [271]. Moreover, B-complex vitamins aid in maintaining a healthy sleep schedule by regulating levels of the sleep-regulating hormone melatonin, helping athletes fall in a deep continuous sleep [5]. This is essential for athletes, as the lack of sleep can affect an athlete’s performance [52]. B-complex vitamins also contribute to maintaining optimal health and performance in athletes, supporting improved brain functioning, concentration, sleep quality, and energy levels [19]. Thus, athletes need to ensure that they are receiving enough vitamin B through their diet or supplements [244].
Thiamine (B1) is a water-soluble vitamin that must be consumed regularly from the diet [6]. Although free thiamine is stable at acidic pH, it is destroyed by ultraviolet (UV) and gamma irradiation and is heat-sensitive [29]. Whole grains, bread, and nuts are the most common thiamine food sources, while milled wheat flour, polished rice, vegetables, and fruits contain less thiamin [272]. The large intestine’s bacteria in the human body are able to produce thiamine and thiamine pyrophosphate (TPP) [52]. Thiamine leaches into the water due to its solubility and is inevitably lost in any discarded soaking or cooking water, as well as destroyed by heating during culinary methods [7].
Thiamine, in its active state (TPP), is a cofactor of numerous important enzymes involved in the metabolism of carbohydrates and branched-chain amino acids [7]. Moreover, it is necessary for several other cellular functions, including the development of nucleic acid precursors, myelin, and neurotransmitters (such as acetylcholine), as well as antioxidant defense [272]. A deficiency of this vitamin leads to a decline in oxidative metabolism [265]. The biochemical outcomes include a failure to create adenosine triphosphate (ATP), lactic acidosis resulting in a greater lactic acid generation, and a reduction in neurotransmitter synthesis (e.g., acetylcholine, glutamate, aspartate, and gamma-aminobutyric acid (GABA)) [6]. The major causes of thiamin deficiency are either the insufficient intake, poor absorption or metabolism, or an increase the body demand [265]. Furthermore, diuretics and diarrhea lead to thiamine deficiency [272]. Regarding thiamin and exercise, research suggests that thiamin availability in the diet appears to influence exercise capacity when athletes consume the recommended amount [254].
Riboflavin (B2) is the second vitamin from the B-complex vitamins [270]. It appears as a yellow-orange chemical molecule that is water-soluble [273]. Riboflavin is relatively heat- and oxygen-stable, especially in an acidic environment [19]. It is very light-sensitive, destroyed by reducing agents, and unstable in alkaline solutions [4]. Riboflavin is essential and must be obtained from food sources [2]. Riboflavin is abundant in almonds, beef liver, sardines, mushrooms, cheddar cheese, and eggs [271]. When athletes consume a typical amount of riboflavin, their exercise capability would be optimum [254].
Niacin (B3) is the third water-soluble member of the B vitamins family [176]. Humans can partially convert the essential amino acid tryptophan to nicotinamide, which is a dietary supply of niacin [270]. However, the conversion cannot meet the demands for niacin, so dietary niacin supplies around 50% of the daily niacin requirement [256]. Meat, whole grains, milk, and dairy products are good sources of niacin [242]. Niacin is abundant in peanuts, seafood, mushrooms, and yeasts [29]. Food items high in tryptophan-containing proteins, such as milk, cheese, and eggs, are good sources of niacin [7]. Its roles include reduction and oxidation (redox) processes, as well as acting as a ligand for a range of purine receptors [243].
It is hypothesized that this vitamin lowers cholesterol, improves thermoregulation, and improves oxidative metabolism [274]. In hypercholesteremic individuals, a niacin intake of 100–500 mg/day may help lower blood lipid levels while increasing homocysteine levels [176]. Nevertheless, consuming 280 mg of niacin during exercise has been demonstrated to reduce exercise capacity by moderating fatty acid mobilization [275].
Pantothenic acid (B5) is a water-soluble vitamin that is widely available in the diet [3]. It is often provided as calcium pantothenate, which is more stable against light, heat, and oxygen, but is unstable in both alkaline and acidic circumstances [273]. Sodium pantothenate is also available, but its use is restricted due to its hygroscopicity [272]. Pantothenic acid functions as a coenzyme for acetyl coenzyme A (acetyl CoA), implying its importance in aerobic or oxygen-based energy systems [2]. Acetyl CoA supplementation has not been shown to increase aerobic performance in studies [25,52,202,276]. Yet, one study found a reduction in the lactic acid buildup, but no benefit in performance was concluded [277].
Pyridoxine (B6) is marketed as a supplement that increases muscular growth, strength, and aerobic capacity in the lactic acid and oxygen systems [141]. It might additionally have a relaxing effect, which has been related to increased mental power [24]. Surprisingly, research showed that pyridoxine did not increase the capacity of aerobic exercise or the accumulation of lactic acid in well-nourished athletes [23]. However, when paired with vitamins B1 and B12, it has been shown to raise serotonin levels and enhance motor abilities, which are required in sports such as pistol shooting and archery [24]. Moreover, vitamin B6, thiamin, and pantothenic acid showed inverse relationships with stress risk and anxiety [25]. Another study revealed that after a month of vitamin B6 intake, young adult athletes reported feeling less anxiety [25].
Cyano-cobalamin (B12) is a coenzyme required for the synthesis of deoxyribonucleic acid (DNA) and serotonin [176]. In theory, it would enhance muscular mass and blood oxygen-carrying capacity and lessen anxiety [273]. However, no ergogenic impact has been documented in well-nourished athletes [242]. Interestingly, it may enhance pistol shooting performance due to the stimulation of serotonin production, which reduces anxiety [2]. A cross-sectional research work studied 100 amnestic mild cognitive impairment (MCI) patients characterized by low-normal and high-normal vitamin B12 levels, who were then enrolled in an Auditory Verbal Learning test to evaluate their memory’s function. The results showed that those with low-normal B12 concentrations had notable defects in learning and recognition abilities and even in memory performance due to the low microstructure integrity of the hippocampus [23]. It is important to acknowledge that vitamin B12 is crucial for proper brain functioning, as it aids in faster information processing and enhances concentration levels [21]. This has been demonstrated in patients with mild cognitive impairment (MCI) who had low-normal levels of vitamin B12 [262]. This is especially important for athletes, as improved brain functioning may help improve performance in many ways, from learning new techniques to continuous focus maintenance during long competitions [24].
Folic acid (folate) is a coenzyme that aids in the synthesis of DNA and red blood cells [278]. An increased red blood cell count enhances oxygen supply to muscles during exercise [21,79]. It is thought to be crucial in preventing birth abnormalities and may lower homocysteine levels, which is a risk factor for heart disease [22]. Folic acid supplements did not increase exercise performance among malnourished athletes with folate deficiency [254].
8. Vitamin C
Vitamin C (also known as ascorbic acid) can be found in many types of food, including oranges, strawberries, broccoli, and sweet potatoes [15]. Athletes require more vitamin C than the average person since their bodies are working harder and being pushed to the limits [15,279]. Therefore, they need to receive enough of this vital nutrient to perform at their best. Researchers have reported that the intake of vitamin C supplements does not boost physical performance in well-nourished athletes [52]. Nevertheless, athletes are recommended to receive an adequate amount of vitamin C from their balanced diet.
The crucial role of vitamin C in neutralizing free radicals has been raised from its antioxidative potency [69], thereby improving the immune system [15] and reducing the risk of illnesses such as colds and other viruses [280]. It plays an important role in immunity by enhancing the differentiation and proliferation of B and T lymphocytes and increasing antibodies levels [25]. Furthermore, vitamin C has been reported to modulate cytokine production and decrease histamine levels [169,281]. Studies have also shown that vitamin C can eliminate fatigue, improve coordination, and increase endurance [15].
Vitamin C has a crucial role to play in wound healing and collagen production [3]. It helps boost energy levels and protects the body from illnesses and injuries [242]. Vitamin C works as a co-factor to produce collagen for the propyl and lysol hydroxyls enzymes, which stabilize the structure of collagen [29]. Furthermore, vitamin C also enhances collagen gene expression in fibroblasts [7], contributing to the strength and integrity of joints and muscles, which is essential for the success of any athlete. This is supported by the fact that vitamin C is crucial in protecting against ROS damage, enhancing keratinocyte differentiation, lipid synthesis, fibroblast proliferation, and migration, which has been seen to shorten the time of wound healing [28,282].
However, high levels of vitamin C can, in turn, act as a pro-oxidant rather than an antioxidant [29]. The overconsumption of vitamin C supplement decreases exercise-induced adaptation, delays post-exercise recovery, increases lipid peroxidation, and diminishes mitochondrial biogenesis [127]. These effects can hinder skeletal muscle adaptation to exercise [3].
9. Minerals
Numerous physiological and metabolic processes in the human body involve minerals [283]. Minerals have physiological effects on the body during exercise, including maintaining a normal heartbeat, oxygen transportation, antioxidation activity, healthy bone, and immune system enhancement [283]. Sufficient levels of minerals are required for optimal performance because many of these processes are enhanced during sports activity [284]. For athletes to perform at their best, maintaining a healthy body necessitates the intake of a variety of nutrients. Some minerals make weightlifting more effective by enhancing athletic performance; these are the minerals that degrade faster when used in sports endeavors [285] and thus need to be replaced routinely among athletes to sustain their performance.
10. Iron
Iron (Fe) is a crucial mineral for physical performance, and its importance cannot be overstated [286]. When it comes to peak performance, an adequate intake of iron can make all the difference [149]. It helps the body produce red blood cells, which are necessary for transporting oxygen to the muscles [71]. Without enough iron, athletes and other physically active individuals may suffer from fatigue and lethargy as the body struggles to meet the increased demands [71]. A huge part of the pool of plasma iron (almost 80%) is utilized by the bone marrow; this is equivalent to a 20–30 mg/day dose to ensure the efficient production of erythrocyte [31].
In addition to red blood cells production, iron is also important for energy metabolism [31]. It is necessary for converting food into energy, and it helps to ensure that the body can use energy efficiently for physical activities [280]. Iron also helps the body in regulating its temperature, making it an essential nutrient for athletes competing in warm climates or hot weather [149]. Finally, it is important for other bodily functions, such as the immune system, growth, and hormone production [284]. When considering physical performance, it is important to ensure that iron intake is adequate and balanced. The human physiological mechanism preserves the maximum iron [29]. Based on the total compulsory iron depletion that occurs daily and the average of 10% absorption and bioavailability, the World Health Organization (WHO) and other national institutes have estimated iron-recommended doses depending on several characteristics including gender, age, and race. The recommended dietary intake for females is 18 mg, and for males, it is 8 mg [31]. Poorly planned diets, coupled with inadequate levels of exercise, can lead to anemia and other problems associated with low iron levels [286]. This may cause fatigue, poor performance, and a decreased ability to perform physical activities [285]. Therefore, it is necessary to consume a high-quality variant diet that involves iron-rich sources [284].
It is also important to make sure that athletes have enough time to rest and recover between workouts. Iron helps to replenish energy stores and reduce fatigue, so it is important to give the body time to absorb the nutrient [287]. Additionally, certain supplements may also help in providing additional iron to meet the demands of physical performance [205]. Athletic training can result in alterations including higher vascularization (creation of new blood vessels), elevated hematocrit, and higher erythrocyte awareness in the blood, which may lead to an increase in iron needs [122]. A shortage of iron may result from hemorrhages, gastric blood loss, and/or urinary tract bleeding, especially among high-intensity sports [121]. Professionals are predicted to have 70% higher iron needs than non-professionals [287]. Iron deficiency anemia can impede progress in an athlete’s training by reducing oxygen delivery [283]. Lastly, most research concluded that iron supplements do not enhance aerobic performance, unless there is a specific depletion and/or anemia reported [149].
This entry is adapted from the peer-reviewed paper 10.3390/sports11060109
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