Four Days of Blueberry Powder Supplementation Lowers the Blood Lactate Response to Running But Has No Effect on Time-Trial Performance

Berry Fruits and Their Improving Potential on Skeletal Muscle Health and Performance: A Systematic Review of the Evidence in Animal and in Human Studies

The well-established anti-inflammatory and antioxidant properties of red fruits leave room for a biological pathway of improved muscle health promoted by berries in the diet. Our objective was to systematically review the number of trials conducted on human and animal species around the relationship between a berry diet and muscle health outcomes. Two independent examiners conducted a search for studies that utilized keywords associated with muscle health outcomes and a berry-based diet in both human and animal trials, in accordance with the PRISMA statement guidelines. The literature was searched through six electronic databases until December 2023. Screening of 152 retrieved articles resulted in a final selection of 16 reports investigating the effect of exposure to a berry-based diet and skeletal muscle health outcomes. The study protocol was registered on PROSPERO (CRD42023479682). Among the selected studies, nine involved humans and seven animal models (rats and mice). Overall, most of the studies reported positive effects on performance or muscle health. Specifically, five studies investigated the possible effects of blackcurrant on active human subjects or athletes; three studies focused on blueberry and presented results on running performance (human sample) and muscle health (rat models). The rest of the studies involved raspberries (two studies, rat models), aronia (one study, rat models), elderberry (one study, rat models), and a mixed compound (one study, rat models). In conclusion, there is some early evidence that a berry-rich diet may increase performance or muscle health, but more research is needed to fully understand the underlying biological trajectories, and thus, no firm conclusions can yet be drawn.

Effects of Vaccinium berries (blueberries, cranberries and bilberries) on oxidative stress, inflammation, exercise performance, and recovery - a systematic review

Exercise-induced muscle damage is common in athletes and recreational exercisers and can lead to muscle soreness, weakness, and impaired muscle function. The precise mechanisms are unclear but oxidative stress and inflammation are thought to play a role. (Poly)phenols are substances abundant in Vaccinium berries that have been suggested to possess antioxidant and anti-inflammatory effects that could help improve exercise performance and/or recovery from exercise. The objective of this systematic review was to evaluate the benefits of Vaccinium berry supplementation on exercise performance and recovery, as well as on exercise-induced oxidative and inflammatory biomarkers in healthy individuals. A comprehensive search was conducted in PubMed, ProQuest Medline, Web of Science, Cochrane Library, and Scopus. Studies were included if the participants were healthy individuals who were supplemented with any Vaccinium berry or Vaccinium berry-based products in comparison to a control group. Of the 13 articles included in this review, no significant differences in the exercise performance were found and only one study reported benefits for markers of recovery. Interleukins and c-reactive protein were the most frequently reported biomarkers, but there was limited evidence that Vaccinium berry supplementation impacted them post-exercise. Most studies were of high quality and showed a low risk of bias. Vaccinium berry supplementation is not effective in modulating markers of exercise-induced inflammation and oxidative distress in healthy individuals; nevertheless, more studies are required to evaluate their effects on exercise performance and recovery in this population.

The effect of dietary anthocyanins on biochemical, physiological, and subjective exercise recovery: a systematic review and meta-analysis

Anthocyanins (ACN), the sub-class of (poly)phenols responsible for the red-blue-purple pigmentation of fruit and vegetables, have gained considerable interest in sport and exercise research due to their potential to facilitate exercise recovery. A systematic literature search was performed using PubMed, The Cochrane Library, MEDLINE, SPORTDiscus and CINAHL. Thirty nine studies were included and the standardized mean difference (Hedges g) for creatine kinase (CK), anti-oxidative and inflammatory markers, strength, power and delayed onset muscle soreness (DOMS) indices were pooled in separate meta-analyses; meta-regression was also performed on reported ACN dose. Immediately post-exercise there was an increase in antioxidant capacity (g: 0.56) and reduced C reactive protein (g: -0.24) and tumor necrosis factor α (g: -40); p ≤ 0.02. Strength was improved with ACN at all time points (g: 0.45-0.67). DOMS (g: -0.23) was lower 24 hours post-exercise and power was improved 24 hours (g: 0.62) and 48 hours (g: 0.57) post exercise. The CK was lower 48 hours post-exercise (g: -0.31) and there was a trend for a positive association with ACN dose (p = 0.057). This systematic review provides new data showing ACN-rich foods promote functional and subjective recovery likely due to the antioxidant and anti-inflammatory properties of ACN.

Blueberries and their bioactives in the modulation of oxidative stress, inflammation and cardio/vascular function markers: a systematic review of human intervention studies

Blueberries represent a rich source of (poly)phenols and other bioactive compounds. Numerous in vitro and animal model studies documented the potential health-promoting properties of blueberries and blueberry-bioactives, while little is still known about their effects in humans. The objective of the present systematic review is to provide main evidence and the potential mechanisms of action of blueberry and its (poly)phenols in the regulation of markers related to oxidative stress, inflammation, vascular and cardiometabolic function in health and disease states. A total of 45 human intervention studies were included in this review. Overall, the evidence suggests that blueberries may play a role in the improvement of markers of vascular function. Their effects were observed following both post-prandial and long-term consumption, particularly in subjects with risk factors and/or disease conditions. Conversely, the conflicting results on inflammation, oxidative stress and cardiometabolic risk markers were most likely due to differences among studies in terms of study design, subject characteristics, duration of intervention, dosage, and type of biomarkers analyzed. For these reasons, high-quality, well-designed, human intervention studies are warranted to strengthen the current findings on vascular function and provide more evidence about the impact of blueberries on the different markers considered. In addition, studies focusing on the relationship between the structure and the function of (poly)phenols will be fundamental for a better comprehension of the mechanisms behind the health effects observed.

Nutritional Compounds to Improve Post-Exercise Recovery

The metabolic and mechanical stresses associated with muscle-fatiguing exercise result in perturbations to bodily tissues that lead to exercise-induced muscle damage (EIMD), a state of fatigue involving oxidative stress and inflammation that is accompanied by muscle weakness, pain and a reduced ability to perform subsequent training sessions or competitions. This review collates evidence from previous research on a wide range of nutritional compounds that have the potential to speed up post-exercise recovery. We show that of the numerous compounds investigated thus far, only two-tart cherry and omega-3 fatty acids-are supported by substantial research evidence. Further studies are required to clarify the potential effects of other compounds presented here, many of which have been used since ancient times to treat conditions associated with inflammation and disease.

Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Increasing nitric oxide bioavailability may induce physiological effects that enhance endurance exercise performance. This review sought to evaluate the performance effects of consuming foods containing compounds that may promote nitric oxide bioavailability.

METHODS

Scopus, Web of Science, Ovid Medline, EMBASE and SportDiscus were searched, with included studies assessing endurance performance following consumption of foods containing nitrate, L-arginine, L-citrulline or polyphenols. Random effects meta-analysis was conducted, with subgroup analyses performed based on food sources, sex, fitness, performance test type and supplementation protocol (e.g. duration).

RESULTS

One hundred and eighteen studies were included in the meta-analysis, which encompassed 59 polyphenol studies, 56 nitrate studies and three L-citrulline studies. No effect on exercise performance following consumption of foods rich in L-citrulline was identified (SMD=-0.03, p=0.24). Trivial but significant benefits were demonstrated for consumption of nitrate and polyphenol-rich foods (SMD=0.15 and 0.17, respectively, p<0.001), including performance in time-trial, time-to-exhaustion and intermittent-type tests, and following both acute and multiple-day supplementation, but no effect of nitrate or polyphenol consumption was found in females. Among nitrate-rich foods, beneficial effects were seen for beetroot, but not red spinach or Swiss chard and rhubarb. For polyphenol-rich foods, benefits were found for grape, (nitrate-depleted) beetroot, French maritime pine, Montmorency cherry and pomegranate, while no significant effects were evident for New Zealand blackcurrant, cocoa, ginseng, green tea or raisins. Considerable heterogeneity between polyphenol studies may reflect food-specific effects or differences in study designs and subject characteristics. Well-trained males (V̇O2max ≥65 ml.kg.min-1) exhibited small, significant benefits following polyphenol, but not nitrate consumption.

CONCLUSION

Foods rich in polyphenols and nitrate provide trivial benefits for endurance exercise performance, although these effects may be food dependent. Highly trained endurance athletes do not appear to benefit from consuming nitrate-rich foods but may benefit from polyphenol consumption. Further research into food sources, dosage and supplementation duration to optimise the ergogenic response to polyphenol consumption is warranted. Further studies should evaluate whether differential sex-based responses to nitrate and polyphenol consumption are attributable to physiological differences or sample size limitations.

OTHER

The review protocol was registered on the Open Science Framework ( https://osf.io/u7nsj ) and no funding was provided.

Blueberry supplementation reduces the blood lactate response to running in normobaric hypoxia but has no effect on performance in recreational runners

Background

Blueberries are concentrated with anthocyanins possessing antioxidant properties. As these properties counter fatigue, blueberry supplementation may improve performance and recovery, particularly in hypoxia, where oxidative stress is elevated.

Methods

This study examined the effects of blueberry supplementation on running performance, physiological responses, and recovery in normobaric hypoxia. Eleven experienced runners completed a 30-minute time-trial (TT) in normobaric hypoxia (%O₂ = 15.5 %) on separate days after supplementation with four days of blueberries (BLU) or four days of placebo (PLA). Heart rate (HR), oxygen saturation (SaO₂) and ratings of perceived exertion (RPE) were monitored during the TT. Blood lactate and fraction of exhaled nitric oxide (F_ENO) were assessed pre-TT, post-TT, and during recovery.

Results

No significant differences were observed in the distance run during the TT, HR, SaO₂, and RPE. The post-TT increase in blood lactate was significantly lower in BLU than PLA (p = 0.036). Pre-TT and post-TT F_ENO did not differ between conditions. Blood lactate recovery following the TT was similar between conditions.

Conclusions

Four days of blueberry supplementation did not alter running performance or cardiovascular and perceptual responses in normobaric hypoxia. Supplementation lowered the blood lactate response to running, however, the significance of this finding is uncertain given the absence of an ergogenic effect.

Blueberry Consumption and Exercise: Gap Analysis Using Evidence Mapping

Objective: Strenuous muscular workouts can increase markers of inflammation that can potentially damage components of skeletal muscles. Blueberries contain a variety of nutrients and phytochemicals that have individually been related to reduction in oxidative stress and inflammation. The objective was to conduct a systematic overview using evidence mapping to identify research-dense and evidence gap areas that examine the impact of blueberry consumption on exercise performance and inflammatory markers in adults. Design: The authors searched Medline, Cochrane Central, and Commonwealth Agricultural Bureau for literature published between 1946 and September 2019. Abstracts and full-text publications were screened in duplicate for studies that evaluated outcomes related to metabolism, lipoprotein, muscle damage, markers of oxidative stress, inflammatory markers, or gait after participants consumed blueberries and were subjected to some form of exercise. Results: The authors found nine randomized controlled trials, one single-arm study, and one observational study that met the eligibility criteria. Inflammatory markers, F2-isoprostanes, and gait speed were the most frequently reported outcomes, with each one reported by at least three studies. Outcomes related to metabolism, lipoproteins, muscle damage, and most markers of oxidative stress and most gait-related outcomes were each reported by one study. Intervention trials were generally conducted with a small number of participants and the majority included mostly younger individuals. Using multivariate analysis, the sole observational study examined physical ability among participants who consumed higher doses of blueberries compared with participants who consumed a half cup of blueberries less than once a month. Conclusions: Evidence mapping found that further research in both randomized controlled trials and cohort studies examining the impact of blueberry consumption on exercise performance and inflammatory markers is needed to establish an association.

The effect of acute stress on salivary markers of inflammation: A systematic review and meta-analysis

BACKGROUND

Salivary biomarkers of inflammation are increasingly used in stress research. This systematic review and meta-analysis provides a quantitative summary of changes in salivary inflammatory markers in response to acute stress.

METHOD

The review included 1558 participants (42 unique samples, 33 studies) obtained through electronic databases (PubMed, PsycINFO, Embase), reference treeing, and articles identified by a 2015 review on a similar topic. To be eligible, articles had to be quantitative and assess change in at least one biomarker of salivary inflammation in response to acute stress in adults. The primary outcome was magnitude of change in inflammatory biomarkers (Cohen's d for repeated measures [dav]).

RESULTS

Measures of salivary inflammation included: C-reactive protein (CRP), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, IL-13, IL-17A, IL-18, IL-21, interferon (IFN)-α, IFN-γ, and tumor necrosis factor (TNF)-α. Cytokines IL-6 (k = 26, dav = 0.27), IL-10 (k = 11, dav = 0.34), TNF-α (k = 10, dav = 0.57), and IFN-γ (k = 6, dav = 0.28) significantly increased in response to stress. Post hoc sensitivity analyses revealed that IL-1β (k = 19, dav = 0.16) and IL-8 (k = 7, dav = 0.30) also increased from pre- to post-stress, but findings with IFN-γ did not hold after removing one outlier study. Examination of moderators suggested that study methodology and sample demographics moderated some associations.

CONCLUSIONS

This meta-analysis revealed that certain salivary inflammatory cytokines increase in response to acute stress. Significant heterogeneity in results and moderator analyses suggest need for standardization of research protocols. Directions for future research are discussed.