Effects of Beetroot Juice on Physical Performance in Professional Athletes and Healthy Individuals: An Umbrella Review

The selection and exclusion criteria for all relevant articles were determined by two researchers (C.T. and Q.R.J.).

Inclusion Criteria: We included peer-reviewed, full-text meta analyses with quantitative synthesis (≥2 studies) published in English; (1) healthy adults or trained athletes aged 18–65 years with no known diagnosed disorders; (2) assessed dietary-nitrate supplementation delivered specifically as beetroot juice or an equivalent nitrate-rich formulation, administered either acutely (a single dose 2–3 h before exercise) or chronically (for ≥3 days) at a dose of ≥4.6 mmol nitrate per day or per administration; (3) compared the intervention with a placebo, a low-nitrate control, or no-supplement condition; and (4) reported at least one validated physical-performance endpoint, namely muscular strength or endurance, maximal oxygen uptake (VO₂ max), lactate-tolerance measures such as time to exhaustion (TTE) or the Yo-Yo intermittent-recovery test level 1, or speed assessed by a time-trial. Only the most complete dataset was retained when multiple publications described the same cohort. Exclusion Criteria: We excluded (1) duplicate publications, Scoping reviews, narrative reviews, protocols, conference abstracts, primary RCTs, reviews without a meta-analysis; (2) articles whose full text was inaccessible; (3) trials that tested multi-ingredient formulas without a dedicated nitrate arm or employed active comparators lacking a true placebo/low-nitrate control; (4) children, elderly with chronic diseases, or any participants with diagnosed health conditions; studies mixing healthy and clinical populations without separable data; and (5) reports that failed to provide or allow extraction of the specified performance outcomes, or reported only biochemical/surrogate markers. Information about inclusion and exclusion criteria can be found in Appendix A.

A comprehensive search was conducted on the Web of Science, Embase, PubMed, Cochrane Database, SPORTDiscus, Scopus, and CINAHL databases, covering the period from 2000 to November 2024. A search strategy was employed, utilizing a systematic review filter to refine the search results. Regular updates to the search were performed to identify the most recently published systematic reviews. The search was conducted using subject headings and free-text terms related to beetroot, nitrate, and exercise. A detailed search strategy is provided in. The search strategy was adapted for different databases to ensure comprehensive coverage. Supplementary File S1

Following the completion of the literature search, reference management software (EndNote 20) was used to organize the studies. After removing duplicate records, two reviewers (C.T. and Q.R.J.) screened the titles and abstracts to exclude ineligible studies. Full-text screening of the eligible studies was then conducted by the same two independent reviewers. Any discrepancies were resolved by consulting a senior third reviewer (S.M.).

Data were extracted for the following items: authors of the review; publication date of the review; number of included studies; characteristics of the included population in the review; intervention methods of the studies; timing and dosage of dietary nitrate supplementation; and results of the review. The data extraction form used is presented in Table 1.

The methodological quality of the included systematic reviews was assessed using the A Measurement Tool to Assess systematic Reviews 2 (AMSTAR 2) checklist [73]. The reviews were classified into four categories: high, moderate, low, and critically low quality. Among the 16 items on the AMSTAR 2 checklist, 7 were identified as critical domains for evaluating methodological rigor. These key domains include the following: registering the review protocol before initiation, conducting a comprehensive literature search, providing justifications for excluding individual studies, adequately assessing the risk of bias in included studies, using appropriate statistical methods in meta-analyses, and considering the risk of bias when interpreting results. If any key domain is not met, the study was rated as low quality; studies rated as very low quality were excluded. Detailed information on the quality assessment is provided in Supplementary File S2, Table 1.

Publication bias occurs when studies with significant results are favored over those with non-significant findings, potentially influencing data analysis. Funnel plots were used to assess this bias by plotting sample size (or inverse standard error) against effect size. Larger studies yield more precise effect estimates, forming a funnel shape. An asymmetric funnel indicates possible publication bias, which was statistically tested using Egger’s test [74]. The detailed risk of bias results are presented in Supplementary File S3.

The fundamental characteristics of the included reviews were reported in tabular format, specifying which outcomes were addressed in each review. To assess the degree of overlap among systematic reviews and evaluate potential redundancy, the Corrected Covered Area (CCA) Index was utilized. The extent of literature duplication was classified into four categories: (1) CCA: 0–5% (Minimal Overlap)—indicating a low degree of overlap among systematic reviews, with minimal duplication of primary literature; (2) CCA: 6–10% (Moderate Overlap)—representing a moderate level of overlap that requires researchers’ attention to potential redundancy; (3) CCA: 11–15% (High Overlap)—suggesting a substantial degree of overlap, with multiple systematic reviews sharing a significant portion of the primary literature; and (4) CCA: >15% (Extremely High Overlap)—indicating severe overlap among systematic reviews, with a considerable amount of duplicate primary literature. In cases where overlap falls within this range, researchers should conduct a rigorous assessment before selecting systematic reviews for inclusion [75,76]. The detailed process and results are presented in Supplementary File S4.

The data synthesis was descriptive and presented in detailed tabular summaries. The extracted data were consistently analyzed for quantitative synthesis, and standardized mean differences (SMD) with 95% confidence intervals (CI) were calculated. In addition, following Cochrane’s recommended harmonized SMD directions [77]. Data analysis was performed using R (version 4.4.2) and STATA 17 (METAN package), employing both random-effects and fixed-effects models to compute the standardized mean differences. The overall effect size (95% CI) and I² statistic [78] were calculated using STATA17 (METAN package). Effect sizes were categorized as negligible (<0.2), small (<0.59), moderate (<1.19), and large (>1.19) [79]. The I² values were interpreted as follows: low heterogeneity (I² < 25%), moderate heterogeneity (25% ≤ I² < 50%), and significant heterogeneity (I² ≥ 50%) [80]. The detailed data processing results are presented in Supplementary Files S3 and S5.

A total of 2138 articles were retrieved from the Web of Science, Embase, PubMed, Cochrane Database, SPORTDiscus, Scopus, and CINAHL databases. After excluding 377 duplicate articles, 21 articles were selected by reviewing the titles and abstracts of the remaining articles. Based on the inclusion and exclusion criteria, 4 articles were excluded after full-text review, 0 articles were excluded due to low quality, and 2 articles were excluded due to their impact on the duplication rate of the original literature. Ultimately, 15 studies were included in this umbrella review. Figure 1 illustrates the selection process according to the PRISMA flowchart.

All 15 included systematic reviews met the quality requirements, as assessed using the AMSTAR 2 tool. The majority of the reviews were rated as moderate to high in methodological quality.

This umbrella review excluded two meta-analyses with a high proportion of duplicate original studies and reanalyzed the remaining studies. The Corrected Covered Area (CCA) Index was determined to be 7.07%, indicating a moderate degree of overlap. Despite this moderate overlap, the complexity of the research field necessitates the inclusion of different meta-analyses, as the original studies included in each meta-analysis vary in terms of outcome measures and study populations. These differences provide a broader perspective for a comprehensive understanding of the research question and contribute valuable information that cannot be simply disregarded by eliminating duplicate studies. While the presence of duplicate studies may introduce certain challenges, such as affecting the accuracy and interpretability of the results and increasing analytical complexity, a comprehensive synthesis of these studies allows for a deeper exploration of the multidimensional aspects of the research question. This approach enables the identification of commonalities and distinctions among different studies, ultimately offering a more comprehensive reference for future research. The details of the outcome indicator data analytics are presented in Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15.

The results of this study showed that beetroot juice supplementation did not enhance muscle strength for healthy adults (including athletes and non-athletes). Subgroup analysis indicated that this general ineffectiveness resulted primarily from a lack of effects for non-athletes, while supplementation did improve muscle strength for professional athletes.

After beetroot juice supplementation, dietary nitrate is converted into NO in the body [18], potentially enhancing muscle strength via the following mechanisms: 1. Enhanced calcium release: NO may directly promote calcium release from the sarcoplasmic reticulum through transnitrosylation of ryanodine receptors [84], thereby improving muscle strength. 2. Increased contractile force of type II (fast-twitch) muscle fibers: Type II fibers typically exhibit lower microvascular oxygen tension during contraction [85,86]. Under these hypoxic conditions, nitrite can be reduced to NO via deoxyhemoglobin or xanthine oxidoreductase [19,87]. Additionally, NO may upregulate the expression of calcium-handling proteins in type II fibers [85,88]. 3. Vasodilation and improved muscle oxygenation: NO also induces vasodilation, enhancing muscle blood flow and oxygen delivery [15,16].

Possible explanations include significant population specificity in the effects of beetroot juice on muscle strength: 1. In daily physical activities (such as cycling, jogging, and brisk walking), ordinary individuals primarily engage in moderate- to low-intensity aerobic exercise [89], which relies on the aerobic metabolic system. In such activities, energy supply is sufficient, and oxygen demand and supply remain relatively balanced [90]. Conversely, elite athletes (such as weightlifters and sprinters) focus more on resistance training, which predominantly relies on anaerobic metabolism [91,92]. This type of high-intensity exercise is more likely to induce local muscle hypoxia due to inadequate oxygen supply [93], accompanied by lactate accumulation and metabolic stress [94]. In such training scenarios, beetroot juice, rich in nitrates, can activate the nitric oxide (NO) pathway, leading to vasodilation that improves local blood flow [95]. Consequently, this helps to precisely alleviate hypoxia, accelerate the clearance of metabolic waste, and ultimately enhance muscle fatigue resistance [96,97]. 2. The exertion of muscle strength largely depends on rapid energy supply and neuromuscular coordination [98]. Professional athletes may gain more from the conversion of beetroot juice to NO. In contrast, the neuromuscular system of non-athletes may not yet require such optimization mechanisms, or their exercise intensity may not be sufficient to induce significant changes.

Although the present study did not observe improved muscle strength for non-athletes following beetroot juice supplementation (consistent with several previous studies [32,37,44]), other studies have reported contrasting results [31,99]. These discrepancies may stem from differences in muscle strength testing protocols (e.g., faster contraction speeds potentially activating more type II muscle fibers) and variations in participant characteristics. Therefore, further research addressing these factors is warranted.

This study employed maximal oxygen uptake (VO2max) as the marker of aerobic endurance. The results indicated that beetroot juice supplementation produced a statistically significant improvement (p = 0.033) in VO2max among healthy adults; however, the effect size remained below a meaningful threshold (SMD < 0.2). However, subgroup analysis revealed significant population differences: this ineffectiveness was attributed to the inclusion of professional athletes. This study included a total of four studies related to maximal oxygen uptake, two of which reported GXT [70,71] performance (the common method for determining VO2max in a laboratory setting), one directly reported maximal oxygen uptake [72], and another reported peak oxygen uptake [65] (some subjects were elderly, and peak oxygen uptake can be used to assess the level of cardiorespiratory endurance in this population [100]).

Consistent with the results of this study, several studies have confirmed that beetroot juice supplementation can improve aerobic endurance in healthy adult populations [9,12]. The following mechanisms may account for these observed effects: 1. Beetroot juice is reduced to nitrite (NO₂⁻) by oral bacteria and then converted to NO [95] in the body. NO, as a potent vasodilator, acts on vascular smooth muscle to cause dilation, thereby reducing peripheral resistance and increasing blood flow to skeletal and cardiac muscles [14,16,21]. 2. NO can regulate mitochondrial respiratory efficiency [19]. It reduces proton (H⁺) leak across the mitochondrial inner membrane, thereby enhancing oxidative phosphorylation efficiency [101]. 3. Under hypoxic conditions induced by intense exercise, such as within the microenvironment of type II muscle fibers, nitrite (NO₂⁻) can act as an alternative electron acceptor in the mitochondrial respiratory chain, theoretically substituting for oxygen [102].

Beetroot juice was effective for improving aerobic endurance for non-athletes but not for athletes, consistent with findings from previous studies [14,53,60,62,87]. The reasons for this discrepancy may be as follows: 1. Significant population differences in aerobic endurance were also observed in this study, a possible explanation for this discrepancy is that individuals with higher aerobic capacity tend to exhibit in-creased expression of nitric oxide synthase (NOS) enzymes [103], thereby enhancing their ability to produce NO via the L-arginine pathway. Additionally, professional athletes typically undergo training adaptations that enhance capillary function, allowing them to maintain muscle oxygenation and upregulate NOS activity under most conditions. Consequently, they exhibit a reduced dependence on the nitrate–nitrite–NO pathway [104]. This physiological adaptation results in higher baseline plasma nitrite levels in professional endurance athletes compared to untrained individuals [103]. Supporting this, Poveda et al. [105] found that endurance-trained athletes had 158% higher plasma nitrite concentrations than their untrained counterparts. As a result, nitrate supplementation does not further increase NO production in these individuals. 2. Genetic and training adaptations influencing VO₂ max: VO₂ max is significantly influenced by genetic factors [106]. Athletes typically possess an inherently higher maximal oxygen uptake compared to non-athletes, and after long-term intensive training, their VO₂ max may approach an individual’s physiological upper limit [107]. Thus, performance-enhancing supplements such as beetroot juice may have minimal additional impact on their maximal oxygen uptake.

This study evaluated lactate tolerance using the TTE and Yo-Yo IR1 tests. Results indicated that beetroot juice supplementation significantly improved performance in both TTE and Yo-Yo IR1 tests. The results of some studies are consistent with the present study [70,71,72]. This may be because after supplementation with beetroot juice, NO causes dilation of capillaries or small arteries, increases microcirculatory blood flow, improves the transport of tissue oxygen, nutrients, and metabolic wastes [16,21,97,108], accelerates the rate of lactic acid clearance, and allows for a more adequate supply of oxygen to the tissues, as well as mediating an increase in mitochondrial efficiency [19,96,109] (the detailed mechanism is mentioned in the previous section). The above mechanisms result in lower oxygen consumption by the muscles at the same exercise intensity, reduced lactic acid production, increased metabolism, and delayed onset of fatigue.

These findings suggest that beetroot juice supplementation enhances performance not only by optimizing oxygen delivery and utilization efficiency, but also by improving lactate tolerance and delaying the onset of fatigue. These benefits are particularly relevant for high-intensity interval training and competitive sports performance. Although the TTE and Yo-Yo IR1 studies did not differentiate between athletes and non-athletes, athletes likely have a greater demand for such supplements than non-athletes, who prioritize health promotion and exercise experience. Therefore, future research should specifically investigate the effects of beetroot juice supplementation in professional athletic populations.

In this study, time trials (TTs) were used as a metric to evaluate speed performance.

A time trial (TT) assesses the actual exercise efficiency through exercise performance over a fixed distance or time, and is able to objectively integrate physiological abilities and psychological factors to respond to the subject’s true exercise performance [110]. Although the present study found no significant improvement in TT performance following beetroot juice supplementation, several inherent factors may influence TT results, including the following: 1. participants’ psychological conditions [111], 2. environmental factors [112], and 3. energy reserves and nutritional status during testing [113]. The study also considered its small sample size, variations in testing protocols (e.g., long- vs. short-distance), and differences in subject characteristics (such as age and occupation), since these factors may account for the moderate heterogeneity observed in TT results.

In summary, although TT was used in this study to evaluate speed performance in healthy adults, this metric does not provide a comprehensive measure of speed capability. Further research is necessary to address this limitation in the future.

This study recommends beetroot juice as a route to nitrate supplementation to improve physical performance. As discussed earlier, dietary nitrate supplementation, particularly through beetroot juice, offers greater physiological advantages compared to isolated nitrate supplementation [114]. Numerous studies have shown that nitrate supplementation alone does not enhance physical performance, whereas beetroot juice exhibits ergogenic effects [54,115,116,117,118,119,120]. This discrepancy may stem from the unique phytochemical composition of beetroot juice. It is rich in antioxidants, such as betalains, which not only facilitate the reduction in nitrate to promote NO production but may also enhance performance through multi-target mechanisms, such as modulating oxidative stress and energy metabolism [14,121]. Furthermore, beetroot juice contains about 6–10% carbohydrates, the main component being sucrose (more than 80%) [6], which can serve as an immediate energy substrate during exercise, in addition to providing dietary nitrate. However, as also mentioned in the introduction, some studies have compared nitrate-removed beetroot juice with normal beetroot juice and found that nitrate-removed beetroot juice did not improve physical performance [11,12]. In summary, although it cannot be concluded that beetroot juice improves physical performance solely due to the abundance of nitrates in it, NO₃⁻ is indispensable for its performance-enhancing effects. At the same time, the synergistic effects of the various compounds in beetroot juice may amplify its performance-enhancing effects [13,122].

Regarding the supplementation dose of beetroot juice, in order to improve physical performance, this study recommends supplementation with beetroot juice resulting in nitrate levels of 8.3–16.4 mmol/d (515–1017 mg/d NO₃⁻). Current research has not yet reached a consensus on the optimal dose of beetroot juice supplementation. Studies utilizing lower doses (4–5.5 mmol of NO₃⁻) have reported either no effect on physical performance [8,37,123] or a positive impact [54,124,125,126]. Similarly, studies administering higher doses (>10 mmol) have yielded conflicting results, showing either no effect [41,127] or a beneficial impact on performance [8,128]. In this study, based on the data from the included research, the dosage range was categorized into 4.6–8.3 mmol/d (285–515 mg/d of NO₃⁻) and 8.3–16.4 mmol/d (515–1017 mg/d of NO₃⁻). High-dose beetroot juice supplementation (8.3–16.4 mmol/d) produced a significant improvement in physical performance (p = 0.029), although the effect size was negligible (SMD = 0.14). In contrast, the low-dose group (4.6–8.3 mmol/d) did not achieve significant improvement (p = 0.061) and exhibited substantial heterogeneity (I² = 65.6%). Taken together, high doses of supplementation are more recommended in this study. Although the high-dose effect size is marginal, even such minor differences can influence competitive outcomes in elite sports [2]. In addition, the safety of beetroot juice as a natural diet is guaranteed, and higher doses of supplementation are not harmful to the body. This conclusion aligns with the dose–response findings of Wylie et al. [8], and similarly, Hoon et al. [129] demonstrated that an 8.4 mmol dose improved 2000 m rowing performance, whereas a 4.2 mmol dose did not.

This study classified supplementation protocols into two modes: acute (administered 2–3 h prior to exercise) and chronic (administered more than 3 days prior to exercise). Although both approaches produced statistically significant improvement in physical performance, their effect sizes differed substantially: the acute supplementation group demonstrated a clear benefit (SMD = 0.20), whereas the chronic supplementation group exhibited a minimal effect (SMD = 0.13). Several considerations support the superiority of acute supplementation. First, its timing (2–3 h before exercise) aligns closely with the pharmacokinetics of dietary nitrate: bioavailability approaches 100%, and plasma nitrate concentrations peak approximately two hours post-ingestion (t₁/₂ ≈ 6 h) [9]. Notably, the International Olympic Committee (IOC) also recommends supplementing with 5–9 mmol of nitrate 2–3 h before exercise [2]. Second, the immediacy of acute dosing confers practical advantages in real-world settings. However, it is noteworthy that, despite its marginal effect size, chronic supplementation demonstrates the most robust statistical result (I² = 27.1%), whereas acute supplementation exhibited positive heterogeneity (I² = 67.1%). This suggests that, although acute dosing yields greater average gains, its effects are more variable, whereas chronic dosing provides greater stability. These findings need not be mutually exclusive: we hypothesize that layering an acute 2–3 h pre-competition dose onto a multiday chronic regimen may optimize performance benefits. Nonetheless, the ideal supplementation schedule for beetroot juice warrants further investigation.

Although this study suggests a nitrate level of 8.3–16.4 mmol (515–1017 mg/d NO₃⁻) by supplementing with beetroot juice acute (2–3 h before exercise) or chronic supplementation (≥3 days) in order to improve physical performance, this represents only one effective strategy for reference; the optimal supplementation regimen warrants further investigation.

Despite the comprehensive analysis conducted in this study on the effects of beetroot juice on physical performance in both athletes and healthy individuals, several limitations must be acknowledged. First, within the included meta-analyses, the duplication rate of all original data was 7.07%, and duplicate original studies were not excluded. This may have led to certain study results being over-weighted, potentially affecting the accuracy and reliability of the overall conclusions. Second, high heterogeneity was observed in specific outcome measures, such as the Yo-Yo IR1 test and time to exhaustion (TTE), which could be attributed to variations in experimental design, participant characteristics, beetroot juice dosage, or intervention duration across studies. Such high heterogeneity limits the generalizability of the findings and underscores the need for future research to further standardize experimental conditions to reduce variability. These limitations should be carefully considered when interpreting and applying the results of this study.

The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.