-
1.
The Effects of Dairy Product and Dairy Protein Intake on Inflammation: A Systematic Review of the Literature.
Nieman, KM, Anderson, BD, Cifelli, CJ
Journal of the American College of Nutrition. 2021;40(6):571-582
-
-
-
Plain language summary
Systemic inflammation contributes to the risk and progression of chronic disease, which is in turn influenced by several factors including diet. The aim of this study was to conduct a systematic review to evaluate the effect of dairy products and dairy protein on markers of inflammation in adults that do not have inflammatory-related disorders. The authors analysed 27 previous randomised controlled trial, of which 19 looked at dairy products, and eight looked at dairy protein (casein or whey). In the trials which evaluated dairy products, 10 reported no effect of the intervention, while eight reported a reduction in at least one biomarker of inflammation. All eight trials that investigated dairy protein intake on markers of inflammation reported no effect. The researchers concluded that the available literature suggests that dairy products and dairy proteins have neutral to beneficial effects on biomarkers of inflammation. Additional clinical studies designed using inflammatory biomarkers as the primary outcome are needed to fully understand the effects of dairy intake on inflammation.
Abstract
Systemic inflammation is associated with obesity and chronic disease risk. Intake of dairy foods is associated with reduced risk of type 2 diabetes and cardiovascular disease; however, the impact of dairy foods on inflammation is not well-established. The objective of this study was to conduct a systematic review to evaluate the effect of dairy product (milk, cheese, and yogurt) and dairy protein consumption on low-grade systemic inflammation in adults without severe inflammatory disorders. A literature search was completed in September 2019 using PubMed and CENTRAL as well as inspection of reference lists from relevant review articles. The search resulted in the identification of 27 randomized controlled trials which were included in this analysis. In the 19 trials which evaluated dairy products, 10 reported no effect of the intervention, while 8 reported a reduction in at least one biomarker of inflammation. All 8 trials that investigated dairy protein intake on markers of inflammation reported no effect of the intervention. The available literature suggests that dairy products and dairy proteins have neutral to beneficial effects on biomarkers of inflammation. Additional clinical studies designed using inflammatory biomarkers as the primary outcome are needed to fully elucidate the effects of dairy intake on inflammation.
-
2.
Associations of Dietary Intake on Biological Markers of Inflammation in Children and Adolescents: A Systematic Review.
Bujtor, M, Turner, AI, Torres, SJ, Esteban-Gonzalo, L, Pariante, CM, Borsini, A
Nutrients. 2021;13(2)
-
-
-
Free full text
Plain language summary
Inflammation is the normal physiological response to injury in the body and is designed to protect the host. However, in children and adolescents, chronic low-grade inflammation has been linked to a wide range of conditions. Certain markers in the blood can be measured and used to determine levels of inflammation in the body. This review of 53 studies provides the first evidence for the association between dietary intake and biological markers of inflammation in children and adolescents. Results show that adhering to a healthy way of eating such as the Mediterranean diet, are associated with decreased levels of pro-inflammatory biomarkers. The Western Dietary pattern, as well as intake of ultra-processed foods is associated with higher levels of the same pro-inflammatory markers. A good quality diet, high in fruit and vegetables, wholegrains, fibre and healthy fats ameliorates low-grade inflammation, and therefore represents a potential therapeutic approach. It is also an important element for disease prevention in both children and adolescents.
Abstract
BACKGROUND In children and adolescents, chronic low-grade inflammation has been implicated in the pathogenesis of co- and multi-morbid conditions to mental health disorders. Diet quality is a potential mechanism of action that can exacerbate or ameliorate low-grade inflammation; however, the exact way dietary intake can regulate the immune response in children and adolescents is still to be fully understood. METHODS Studies that measured dietary intake (patterns of diet, indices, food groups, nutrients) and any inflammatory biomarkers in children and adolescents aged 2 to19 years and published until November 2020 were included in this systematic review, and were selected in line with PRISMA guidelines through the following databases: Academic Search Complete, CINAHL, Global Health, Medline COMPLETE and Web of Science-Core Collection. A total of 53 articles were identified. RESULTS Results show that adequate adherence to healthful dietary patterns such as the Mediterranean diet, or food groups such as vegetables and fruit, or macro/micro nutrients such as fibre or vitamin C and E, are associated with decreased levels of pro-inflammatory biomarkers, mainly c-reactive protein (CRP), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α), whereas adherence to a Western dietary pattern, as well as intake of food groups such as added sugars, macro-nutrients such as saturated fatty acids or ultra-processed foods, is associated with higher levels of the same pro-inflammatory biomarkers. CONCLUSIONS This is the first systematic review examining dietary intake and biological markers of inflammation in both children and adolescents. A good quality diet, high in vegetable and fruit intake, wholegrains, fibre and healthy fats ameliorates low-grade inflammation, and therefore represents a promising therapeutic approach, as well as an important element for disease prevention in both children and adolescents.
-
3.
Systematic review and meta-analysis of the associations of vegan and vegetarian diets with inflammatory biomarkers.
Menzel, J, Jabakhanji, A, Biemann, R, Mai, K, Abraham, K, Weikert, C
Scientific reports. 2020;10(1):21736
-
-
-
Free full text
Plain language summary
A growing trend towards vegetarianism and veganism has emerged in the past few years. Evidence has led to the assumption that these diets may protect against chronic disease, and one potential mechanism is through the modulation of inflammatory biomarkers. The aim of this review was to investigate the associations of veganism and vegetarianism with inflammatory markers. From the 21 cross-sectional studies included in this study, both vegan and vegetarian diets were associated with lower levels of CRP compared to omnivores. There was no association with all other inflammatory markers. Based on these findings, the authors conclude there is evidence for both vegan and vegetarian diets reducing CRP, a major marker of low-grade inflammation. More research is needed as most inflammatory markers have only been investigated in single studies thus far.
Abstract
Plant-based diets like vegetarian or vegan diets might influence circulating levels of inflammatory biomarkers, thereby reducing the risk of chronic diseases. This systematic review and meta-analysis aimed to investigate the associations of veganism and vegetarianism with circulating inflammatory biomarkers in comparison to omnivores. Literature search was conducted in Pubmed and EMBASE until April 2020 and mean differences of biomarkers were assessed for: C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-18 (IL-18), interleukin-1 receptor antagonist (IL-1 RA), tumor necrosis factor-alpha (TNF-ɑ), E-selectin, intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), adiponectin, omentin-1 and resistin. Of initially identified 1073 publications, 21 cross-sectional studies met the inclusion criteria and were included in the systematic review and meta-analysis. Vegan diet was associated with lower levels of CRP compared to omnivores [mean difference - 0.54 mg/l, 95%-CI: - 0.79 to - 0.28, p < 0.0001]. This association was less pronounced in vegetarians [mean difference - 0.25 mg/l, 95%-CI: - 0.49 to 0.00, p = 0.05]. In patients with impaired kidney function, the association between vegetarian nutrition and CRP was much stronger with - 3.91 mg/l (95%-CI: - 5.23 to - 2.60; p < 0.0001). No substantial effects were observed for all other inflammatory biomarkers. Despite strong associations between CRP and a vegan or vegetarian diet were seen, further research is needed, as most inflammatory biomarkers were investigated only in single studies so far.
-
4.
Association between consumption of ultra-processed foods and serum C-reactive protein levels: cross-sectional results from the ELSA-Brasil study.
Lopes, AEDSC, Araújo, LF, Levy, RB, Barreto, SM, Giatti, L
Sao Paulo medical journal = Revista paulista de medicina. 2019;137(2):169-176
-
-
-
Free full text
Plain language summary
Low grade chronic inflammation has been linked to many diseases. It can be measured using bio-markers such as C-reactive protein. Studies have shown that there may be a direct association between consumption of ultra-processed foods and the levels of the inflammatory marker C-reactive protein (CRP). The aim of this study was to investigate whether the consumption of ultra-processed foods is associated with CRP levels, regardless of total energy intake, among men and women. In addition, its aim was to determine whether this association is independent from body mass index (BMI). It was a cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health. This is a multi-centre cohort and 15105 adults (aged 35-74) participated. The findings suggest that the positive association of ultra-processed food consumption with CRP levels among women seems to be mediated by the presence of adiposity. The study concludes that cutting back on ultra-processed foods can decrease chronic low-grade inflammation, even if through reducing obesity. This reinforces the importance of public policies aimed towards restricting the availability of ultra-processed foods.
Abstract
BACKGROUND There may be a direct association between consumption of ultra-processed foods and C-reactive protein (CRP) levels, under the assumption that the high glycemic index of these food products could stimulate the entire chronic inflammation cascade, along with an indirect association mediated by obesity. The types of food consumed, including ultra-processed products, strongly influence obesity, and are also associated with higher serum CRP levels. OBJECTIVE Our aim was to investigate whether the caloric contribution of ultra-processed foods to diet is associated with CRP levels, independent of body mass index (BMI). DESIGN AND SETTING Cross-sectional analysis on the Longitudinal Study of Adult Health (ELSA-Brasil) baseline cohort (2008-2010). METHODS Dietary information, obtained through a food frequency questionnaire, was used to estimate the percentage of energy contribution from ultra-processed food to individuals' total caloric intake. CRP levels were the response variable. Sex-specific associations were estimated using generalized linear models with gamma distribution and log-link function. RESULTS Ultra-processed food accounted for 20% of total energy intake. Among men, after adjustments for sociodemographic characteristics, there was no association between ultra-processed food intake and CRP levels. Among women, after adjustment for sociodemographic characteristics, smoking and physical activity, the highest tercile of ultra-processed food intake was associated with mean CRP levels that were 14% higher (95% confidence interval: 1.04-1.24) than those of the lowest tercile. However, after considering BMI, this association lost statistical significance. CONCLUSION Our findings suggest that the positive association of ultra-processed food consumption with CRP levels among women seems to be mediated by the presence of adiposity.
-
5.
Effects of ascorbic acid supplementation on oxidative stress markers in healthy women following a single bout of exercise.
Yimcharoen, M, Kittikunnathum, S, Suknikorn, C, Nak-On, W, Yeethong, P, Anthony, TG, Bunpo, P
Journal of the International Society of Sports Nutrition. 2019;16(1):2
-
-
-
Free full text
Plain language summary
Moderately intense exercise often causes muscle damage, which initiates an acute inflammatory response. Vitamin C or ascorbic acid is suggested to provide antioxidant protection against oxidative stress. The efficacy of ascorbic acid supplementation on exercise-induced oxidative stress remains unclear. The aim of this crossover study was to determine the effects of ascorbic acid supplementation on circulating biomarkers of oxidative stress and muscle damage in 19 healthy women after a single bout of moderately-intense exercise. Participants performed 30 minutes of cycling after ingesting 1000 mg of ascorbic acid or placebo with a one-week washout period. Blood samples were taken before exercise, immediately after and 30 minutes post-exercise to determine various markers of oxidative stress and muscle damage. This study found ascorbic acid supplementation prior to moderately-intense exercise improves antioxidant capacity but does not prevent muscle damage. The exercise performed in this study did not induce systemic inflammation, only low-grade muscle damage. Based on these results, the authors suggest further investigation of the effects of ascorbic acid supplementation during exercise be done to better understand the molecular interactions of ascorbic acid during exercise.
Abstract
BACKGROUND Ascorbic acid is a water-soluble chain breaking antioxidant. It scavenges free radicals and reactive oxygen species (ROS), which are produced during metabolic pathways. Exercise can produce an imbalance between ROS and antioxidants, leading to oxidative stress-related tissue damages. This study was designed to determine the effects of ascorbic acid supplementation on circulating biomarkers of oxidative stress and muscle damage following a single bout of exercise. METHODS In a crossover design with a 1 wk. wash-out period, 19 healthy women performed 30 min moderate-intensity cycling after ingesting 1000 mg of ascorbic acid (AA) or placebo. Blood samples were taken immediately before, immediately after and 30 min post-exercise to determine plasma albumin, total protein, glucose, oxidative stress and muscle damage markers. RESULTS Plasma albumin and total protein levels increased immediately after exercise in placebo alongside slight reductions in glucose (p = 0.001). These effects were absent in AA cohort. Ferric reducing ability of plasma and vitamin C levels in AA cohort significantly increased after exercise (p < 0.05). Superoxide dismutase activity was significantly elevated after exercise (p = 0.002) in placebo but not AA. Plasma malondialdehyde did not change after exercise in placebo but was significantly decreased in AA (p < 0.05). The exercise protocol promoted slight muscle damage, reflected in significant increases in total creatine kinase in all subjects after exercise. On the other hand, plasma C-reactive protein and lactate dehydrogenase remained unchanged. CONCLUSION Supplementation with ascorbic acid prior exercise improves antioxidant power but does not prevent muscle damage.
-
6.
Effects of Tart Cherry Juice on Biomarkers of Inflammation and Oxidative Stress in Older Adults.
Chai, SC, Davis, K, Zhang, Z, Zha, L, Kirschner, KF
Nutrients. 2019;11(2)
-
-
-
Free full text
Plain language summary
Inflammation and oxidative stress are thought to contribute to the development of heart disease. A previous study suggested that drinking tart cherry juice for 12 weeks lowers blood pressure and cholesterol in older adults. The aim of this study was to investigate the effects of tart cherry juice on blood biomarkers of inflammation and oxidative stress. In this randomised-controlled clinical trial, 37 men and women between the ages of 65 and 80 were randomly assigned to drink 480 mL of tart cherry juice or a control drink daily for 12 weeks. Several blood biomarkers of inflammation and oxidative stress were measured at the beginning of the study and after 12 weeks. Tart cherry juice significantly increased blood levels of DNA repair activity of 8-oxoguanine glycosylase and lowered c-reactive protein (CRP) compared to the control group. Blood levels of CRP decreased by 25%, malondialdehyde (MDA) by 3%, and oxidised low-density lipoprotein (OxLDL) by 11% after 12 weeks of tart cherry juice consumption. The authors of this study suggest that the ability of tart cherry juice to reduce blood pressure and cholesterol, in part, may be due to its anti-oxidative and anti-inflammatory properties. Larger and longer follow-up studies are needed to confirm these findings.
Abstract
Inflammation and oxidative stress are important factors in the development of cardiovascular disease and atherosclerosis. The findings of our previous study suggest that 12 weeks consumption of tart cherry juice lowers the levels of systolic blood pressure (BP) and low-density lipoprotein (LDL) cholesterol in older adults. The present study investigated the effects of tart cherry juice on blood biomarkers of inflammation and oxidative stress. In this randomized-controlled clinical trial, a total of 37 men and women between the ages of 65⁻80 were randomly assigned to consume 480 mL of tart cherry juice or control drink daily for 12 weeks. Several blood biomarkers of inflammation and oxidative stress were assessed at baseline and after 12 weeks intervention. After the 12 weeks intervention, tart cherry juice significantly increased the plasma levels of DNA repair activity of 8-oxoguanine glycosylase (p < 0.0001) and lowered (p = 0.03) the mean c-reactive protein (CRP) level compared to the control group. There was a significant group effect observed for plasma CRP (p = 0.03) and malondialdehyde (MDA) (p = 0.03), and a borderline significant group effect observed for plasma oxidized low-density lipoprotein (OxLDL) (p = 0.07). Within group analysis showed that the plasma levels of CRP, MDA, and OxLDL decreased numerically by 25%, 3%, and 11%, respectively after 12 weeks of tart cherry juice consumption compared with corresponding baseline values. The present study suggests that the ability of tart cherry juice to reduce systolic BP and LDL cholesterol, in part, may be due to its anti-oxidative and anti-inflammatory properties. Larger and longer follow-up studies are needed to confirm these findings.
-
7.
Zinc, Magnesium, Selenium and Depression: A Review of the Evidence, Potential Mechanisms and Implications.
Wang, J, Um, P, Dickerman, BA, Liu, J
Nutrients. 2018;10(5)
-
-
-
Free full text
Plain language summary
Adequate micronutrient consumption and mental health are of major public health importance. Recent findings suggest micronutrient deficiencies may play a role in the development and progression of depression, yet the findings remain unclear. The aim of this review is to present the recent evidence on the association between several micronutrients and depression and discuss the potential mechanisms and clinical implications. Based on the current literature, evidence shows an association between both zinc and magnesium deficiency and the risk of depression, with stronger evidence supporting zinc. Studies on selenium are limited or inconclusive. According to these findings, the authors support the importance of adequate micronutrient consumption for promoting mental health. They suggest future research should investigate the safety and efficacy of micronutrient supplementation as an adjunct treatment for depression to better inform current prevention and treatment strategies.
Abstract
Micronutrient deficiency and depression are major global health problems. Here, we first review recent empirical evidence of the association between several micronutrients—zinc, magnesium, selenium—and depression. We then present potential mechanisms of action and discuss the clinical implications for each micronutrient. Collectively, empirical evidence most strongly supports a positive association between zinc deficiency and the risk of depression and an inverse association between zinc supplementation and depressive symptoms. Less evidence is available regarding the relationship between magnesium and selenium deficiency and depression, and studies have been inconclusive. Potential mechanisms of action involve the HPA axis, glutamate homeostasis and inflammatory pathways. Findings support the importance of adequate consumption of micronutrients in the promotion of mental health, and the most common dietary sources for zinc and other micronutrients are provided. Future research is needed to prospectively investigate the association between micronutrient levels and depression as well as the safety and efficacy of micronutrient supplementation as an adjunct treatment for depression.
-
8.
Inflammation and glucose homeostasis are associated with specific structural features among adults without knee osteoarthritis: a cross-sectional study from the osteoarthritis initiative.
Stout, AC, Barbe, MF, Eaton, CB, Amin, M, Al-Eid, F, Price, LL, Lu, B, Lo, GH, Zhang, M, Pang, J, et al
BMC musculoskeletal disorders. 2018;19(1):1
-
-
-
Free full text
Plain language summary
Individuals with osteoarthritis (OA) typically present with greater systemic inflammation and impaired glucose homeostasis. Currently it is unclear whether these factors are associated with early-stage OA, namely bone marrow lesions and swelling. The purpose of this cross-sectional study was to investigate the role of inflammation and glucose homeostasis in early-stage OA. Using baseline data from the Osteoarthritis Initiative, 343 participants were enrolled and tested for markers of inflammation and impaired glucose homeostasis. Bone marrow lesions and swelling were also assessed through imaging results. Results indicate that among individuals without OA, those with greater systemic inflammation were more likely to have bone marrow lesions and knee swelling. According to these results, the authors conclude that systemic inflammation and glucose homeostasis are related to structural features of osteoarthritis. Future studies should explore whether these factors are predictive of OA in order to identify therapeutic targets to prevent or delay the onset of knee OA.
Abstract
BACKGROUND Greater age and body mass index are strong risk factors for osteoarthritis (OA). Older and overweight individuals may be more susceptible to OA because these factors alter tissue turnover in menisci, articular cartilage, and bone via altered glucose homeostasis and inflammation. Understanding the role of inflammation and glucose homeostasis on structural features of early-stage OA may help identify therapeutic targets to delay or prevent the onset of OA among subsets of adults with these features. We examined if serum concentrations of glucose homeostasis (glucose, glycated serum protein [GSP]) or inflammation (C-reactive protein [CRP]) were associated with prevalent knee bone marrow lesions (BMLs) or effusion among adults without knee OA. METHODS We conducted a cross-sectional study using baseline data from the Osteoarthritis Initiative. We selected participants who had no radiographic knee OA but were at high risk for knee OA. Blinded staff conducted assays for CRP, GSP, and glucose. Readers segmented BML volume and effusion using semi-automated programs. Our outcomes were prevalent BML (knee with a BML volume > 1 cm3) and effusion (knee with an effusion volume > 7.5 cm3). We used logistic regression models with CRP, GSP, or glucose concentrations as the predictors. We adjusted for age, sex, body mass index (BMI), and Physical Activity Scale for the Elderly (PASE) scores. RESULTS We included 343 participants: mean age = 59 ± 9 years, BMI = 27.9 ± 4.5 kg/m2, PASE score = 171 ± 82, and 64% female. Only CRP was associated with BML prevalence (odds ratio [OR] = 1.43, 95% confidence interval [CI] = 1.09 to 1.87). For effusion, we found an interaction between BMI and CRP: only among adults with a BMI <25 kg/m2 was there a significant trend towards a positive association between CRP and effusion (OR = 1.40, 95% CI = 1.00 to 1.97). We detected a U-shaped relationship between GSP and effusion prevalence. Fasting glucose levels were not significantly associated with the presence of baseline effusion or BML. CONCLUSIONS Among individuals without knee OA, CRP may be related to the presence of BMLs and effusion among normal weight individuals. Abnormal GSP may be associated with effusion. Future studies should explore whether inflammation and glucose homeostasis are predictive of symptomatic knee OA.
-
9.
A low-dose, 6-week bovine colostrum supplementation maintains performance and attenuates inflammatory indices following a Loughborough Intermittent Shuttle Test in soccer players.
Kotsis, Y, Mikellidi, A, Aresti, C, Persia, E, Sotiropoulos, A, Panagiotakos, DB, Antonopoulou, S, Nomikos, T
European journal of nutrition. 2018;57(3):1181-1195
-
-
-
Free full text
-
Plain language summary
In elite athletes, recovery time between matches is often suboptimal. Since exercise-induced muscle damage (EIMD) can determine the duration of the recovery period, several strategies have been explored to reduce recovery time by attenuating EIMD. The aim of this placebo-controlled, double-blind randomised trial was to examine the effect of a long-term, low-dose bovine colostrum (BC) supplementation on EIMD and performance in 18 elite soccer players. To set a baseline, all participants completed the Loughborough Intermittent Shuttle Test (LIST), a fitness test that simulates the activity pattern of a soccer match, and muscle damage indices were monitored for 72 hours post-exercise. Subjects were then randomised to consume either BC or whey as placebo daily for 6 weeks, and complete the LIST post-intervention with the same indices monitored. This study found that BC helped maintain performance and attenuate post-exercise inflammatory markers compared to whey. Based on these results, the authors conclude a low-dose of BC may reduce post-exercise EIMD and help enhance muscle recovery during a soccer match.
Abstract
PURPOSE The aim of the study was to investigate the effect of a 6-week, low-dose bovine colostrum (BC) supplementation on exercise-induced muscle damage (EIMD) and performance decline in soccer players following the Loughborough Intermittent Shuttle Test (LIST) during a competitive season period. METHODS In a double-blind, randomized, placebo-controlled design, two groups of soccer players were allocated to a 3.2 g/day of whey protein (WP, N = 8) or BC (N = 10) and performed a pre- and a post-supplementation LIST. Maximum isometric voluntary contraction, squat jump (SQJ), countermovement jump, muscle soreness, blood cell counts, creatine kinase (CK), C-reactive protein (CRP) and interleukin-6 (IL-6) were monitored for 2, 24, 48, 72 h post-LIST. RESULTS LIST induced transient increases in leukocytes, granulocytes, CK, muscle soreness, CRP, IL-6 and declines in lymphocytes and performance indices. Supplementation resulted in a faster recovery of SQJ, CK and CRP compared to pre-supplementation kinetics (trial × time: p = 0.001, 0.056, 0.014, respectively) and lower incremental area under the curve (iAUC) for IL-6, only in the BC group [pre-: 31.1 (6.78-46.9), post-: 14.0 (-0.16 to 23.5) pg h/ml, p = 0.034]. Direct comparison of the two groups after supplementation demonstrated higher iAUC of SQJ [WP: -195.2 (-229.0 to (-52.5)), BC: -15.8 (-93.2 to 16.8) cm h, p = 0.034], a trend for lower iAUC of CK in the BC group [WP: 18,785 (4651-41,357), BC: 8842 (4807-14,802) U h/L, p = 0.081] and a significant intervention × time interaction for CRP (p = 0.038) in favor of BC. CONCLUSIONS Post-exercise EIMD may be reduced and performance better maintained by a low dose of BC administration following LIST in soccer players.
-
10.
Effect of bilberry juice on indices of muscle damage and inflammation in runners completing a half-marathon: a randomised, placebo-controlled trial.
Lynn, A, Garner, S, Nelson, N, Simper, TN, Hall, AC, Ranchordas, MK
Journal of the International Society of Sports Nutrition. 2018;15:22
-
-
-
Free full text
Plain language summary
There is a growing interest in identifying alternative approaches for reducing inflammation and lessening recovery time among long distance runners. This type of exercise causes inflammation and muscle soreness which impacts performance and ability to train. Recent studies have shown that various plant-derived polyphenols can counter exercise-induced inflammation and muscle soreness. The aim of this single blind, randomised, parallel study was to investigate whether supplementation of bilberry juice (BJ), a polyphenol-rich fruit, would reduce inflammation and muscle soreness in 19 runners completing a half marathon. Participants were randomised to consume BJ or a placebo fruit drink for 5 days prior to the half marathon, on the day of the race and for two days after the race. Blood samples were collected at baseline, pre-race, post-race, 1 day post-race and 2 days post-race and markers of muscle soreness and damage were measured. Contrary to hypothesis, this study found evidence that BJ produced possibly harmful effects on muscle soreness and inflammatory markers compared to placebo. Based on these results, the authors recommend a larger study to confirm the findings and further explore the underlying cause of the observed detrimental changes.
Abstract
BACKGROUND Emerging evidence indicates that fruits rich in polyphenols may attenuate exercise-induced muscle damage and associated markers of inflammation and soreness. This study was conducted to determine whether bilberry juice (BJ), which is particularly rich in polyphenols, reduces markers of muscle damage in runners completing a half marathon. METHODS A total of 21 recreationally trained runners (age 30.9 ± 10.4 y; mass 71.6 ± 11.0 kg; M = 16; F = 5) were recruited to a single blind, randomised, placebo-controlled, parallel study. Participants were block randomised to consume 2 × 200 ml of BJ or energy-matched control drink (PLA) for 5 d before the Sheffield Half Marathon, on race day, and for 2 days post-race. Measurements of delayed onset muscle soreness (DOMS), muscle damage (creatine kinase; CK) and inflammation (c-reactive protein; CRP) were taken at baseline, pre-race, post-race, 24 h post-race and 48 h post-race. The effect of treatment on outcome measures was analysed using magnitude-based inferences based on data from 19 participants; 2 participants were excluded from the analyses because they did not provide samples for all time points. RESULTS The half marathon caused elevations in DOMS, CRP and CK. BJ had a possibly harmful effect on DOMS from pre-race to immediately post-race (11.6%, 90% CI ± 14.7%), a likely harmful effect on CRP from pre-race to 24 h post-race (mean difference ES 0.56, 90% CI ± 0.72) and a possibly harmful effect on CRP from pre-race to 48 h post-race (ES 0.12, 90% CI ± 0.69). At other time points, the differences between the BJ and PLA groups in DOMS and CRP were unclear, possibly trivial or likely trivial. Differences in the changes in CK between BJ and PLA were unclear at every time point other than from baseline to pre-race, where BJ had a possibly harmful effect on reducing muscle damage (ES 0.23, 90% CI ± 0.57). CONCLUSION Despite being a rich source of antioxidant and anti-inflammatory phytochemicals, BJ evoked small to moderate increases in exercise-induced DOMS and CRP. Further larger studies are required to confirm these unexpected preliminary results.