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Mood Disorders and Gluten: It's Not All in Your Mind! A Systematic Review with Meta-Analysis.
Busby, E, Bold, J, Fellows, L, Rostami, K
Nutrients. 2018;10(11)
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Gluten is a protein found in grains such as wheat, barley and rye. For some people, gluten can cause serious health issues such as coeliac disease (CD). A growing body of research suggests that mood symptoms are associated with gluten-related disorders. The objective of this systematic review and meta-analysis was to establish whether a relationship exists between mood and gluten consumption. 13 studies were included in the meta-analysis. A gluten-free diet (GFD) significantly reduced depressive symptoms in 953 participants overall. Subgroup analyses revealed no difference in effect on mood between those with and without diagnosed CD or between those with a genetic predisposition to CD. In patients diagnosed with classical CD, a GFD resulted in a statistically significant reduction in mood symptoms, whereas the effect for silent CD patients was not significant. The authors concluded that gluten elimination may represent an effective treatment strategy for mood disorders in individuals with gluten-related disorders. Future studies should focus on gluten and mood in participants without a gut-related disorder, for example, in a population sample with depression. Finally, the level of support available to help a patient in maintaining a GFD diet over time should be carefully considered when recommending a GFD in practice.
Abstract
Gluten elimination may represent an effective treatment strategy for mood disorders in individuals with gluten-related disorders. However, the directionality of the relationship remains unclear. We performed a systematic review of prospective studies for effects of gluten on mood symptoms in patients with or without gluten-related disorders. Six electronic databases (CINAHL, PsycINFO, Medline, Web of Science, Scopus and Cochrane Library) were searched, from inception to 8 August 2018, for prospective studies published in English. Meta-analyses with random-effects were performed. Three randomised-controlled trials and 10 longitudinal studies comprising 1139 participants fit the inclusion criteria. A gluten-free diet (GFD) significantly improved pooled depressive symptom scores in GFD-treated patients (Standardised Mean Difference (SMD) -0.37, 95% confidence interval (CI) -0.55 to -0.20; p < 0.0001), with no difference in mean scores between patients and healthy controls after one year (SMD 0.01, 95% CI -0.18 to 0.20, p = 0.94). There was a tendency towards worsening symptoms for non-coeliac gluten sensitive patients during a blinded gluten challenge vs. placebo (SMD 0.21, 95% CI -0.58 to 0.15; p = 0.25). Our review supports the association between mood disorders and gluten intake in susceptible individuals. The effects of a GFD on mood in subjects without gluten-related disorders should be considered in future research.
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Consumption of ultra-processed foods and body fat during childhood and adolescence: a systematic review.
Costa, CS, Del-Ponte, B, Assunção, MCF, Santos, IS
Public health nutrition. 2018;21(1):148-159
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Childhood and adolescent obesity has presented a growing prevalence over the last three decades. Consumption of ultra-processed foods has been pointed out as a risk factor for increasing obesity, as measured by body mass index, among both adolescents and adults. The aim of this study was to identify papers on the association between consumption of ultra-processed food and body fat during childhood and adolescence. This study is a systemic review of 26 articles that evaluated groups of ultra-processed foods or specific ultra-processed foods. Results showed positive associations between consumption of ultra-processed foods and body fat levels. Authors conclude that the use of a standardized food classification, which makes it possible to consider the level of food processing, is much needed in future studies in order to uncover the role of such foods in obesity epidemics.
Abstract
OBJECTIVE To review the available literature on the association between consumption of ultra-processed foods and body fat during childhood and adolescence. DESIGN A systematic review was conducted in the PubMed, Web of Science and LILACS databases. Studies that evaluated the association between consumption of ultra-processed food (exposure) and body fat (outcome) during childhood and adolescence were eligible. SUBJECTS Healthy children and adolescents. RESULTS Twenty-six studies that evaluated groups of ultra-processed foods (such as snacks, fast foods, junk foods and convenience foods) or specific ultra-processed foods (soft drinks/sweetened beverages, sweets, chocolate and ready-to-eat cereals) were selected. Most of the studies (n 15) had a cohort design. Consumption was generally evaluated by means of FFQ or food records; and body composition, by means of double indirect methods (bioelectrical impedance analysis and skinfolds). Most of the studies that evaluated consumption of groups of ultra-processed foods and soft drinks/sweetened beverages found positive associations with body fat. CONCLUSIONS Our review showed that most studies have found positive associations between consumption of ultra-processed food and body fat during childhood and adolescence. There is a need to use a standardized classification that considers the level of food processing to promote comparability between studies.
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New Insights about How to Make an Intervention in Children and Adolescents with Metabolic Syndrome: Diet, Exercise vs. Changes in Body Composition. A Systematic Review of RCT.
Albert Pérez, E, Mateu Olivares, V, Martínez-Espinosa, RM, Molina Vila, MD, Reig García-Galbis, M
Nutrients. 2018;10(7)
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Metabolic Syndrome is the term used to group a cluster of health concerns including overweight, obesity, hypertension, elevated cholesterol, blood glucose intolerance and insulin resistance which together can contribute to the development of Type II Diabetes and Cardiovascular Disease. Diagnosis is usually given if a patient has three or more of these conditions however the diagnosis in children and adolescents is often inconsistent, and so guidelines for therapeutic strategies for metabolic syndrome also vary greatly. This review looked at 9 studies of children aged up to 19 years old, all diagnosed with metabolic syndrome, and given dietary, physical, psychological, and pharmacological interventions, to try and understand what the best clinical approach might be. It was found that a balanced diet combined with aerobic and resistance exercise helped to significantly reduce body mass, more so than the trials which included treatment with Metformin. A balance diet included calorie restriction and carbohydrate reduction, carefully planned around the daily exercise program of 2-3 resistance sessions each week and frequent cardio sessions of differing intensity and duration. They concluded that a minimum of 6 months was needed to reach optimal weight loss and body fat loss. Overall, the findings of this study support diet and physical exercise as beneficial clinical interventions, whilst the use of medication is still unclear.
Abstract
OBJECTIVE To record which interventions produce the greatest variations in body composition in patients ≤19 years old with metabolic syndrome (MS). METHOD search dates between 2005 and 2017 in peer reviewed journals, following the PRISMA method (Preferred Reporting Items for Systematic reviews and Meta-Analyses). The selection criteria were: diagnostic for MS or at least a criterion for diagnosis; randomized clinical trials, ≤19 years of age; intervention programs that use diet and/or exercise as a tool (interventions showing an interest in body composition). RESULTS 1781 clinical trials were identified under these criteria but only 0.51% were included. The most frequent characteristics of the selected clinical trials were that they used multidisciplinary interventions and were carried out in America. The most utilized parameters were BMI (body mass index) in kg/m² and BW (body weight) in kg. CONCLUSIONS Most of the clinical trials included had been diagnosed through at least 2 diagnostic criteria for MS. Multidisciplinary interventions obtained greater changes in body composition in patients with MS. This change was especially prevalent in the combinations of dietary interventions and physical exercise. It is proposed to follow the guidelines proposed for patients who are overweight, obese, or have diabetes type 2, and extrapolate these strategies as recommendations for future clinical trials designed for patients with MS.
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Commissioning guidance for weight assessment and management in adults and children with severe complex obesity.
Welbourn, R, Hopkins, J, Dixon, JB, Finer, N, Hughes, C, Viner, R, Wass, J
Obesity reviews : an official journal of the International Association for the Study of Obesity. 2018;19(1):14-27
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Treating severe and complex obesity requires specialist multi-professional teams for assessment, management and optimizing patients’ health outcomes. The aim of this study was to review existing evidence for defining commissioning and delivery of primary or secondary care weight assessment and management clinics to patients needing specialist care for severe and complex obesity. Twenty-two UK royal colleges and professional organizations were invited to develop the guidance revision according to the NICE-accreditation process. Fifty references were included in the final report. The following additions have been identified as new emergent developments to be included in the guidance: - multi-disciplinary team pathways for children/adolescent patients and their transition to adult care, and - anaesthetic assessment and recommendations for ongoing shared care with general practitioners, as a chronic disease management pathway. Authors indicate that the Guidance Development Group recommends the use of the NICE-accredited commissioning guidance as healthcare services in different countries develop services to manage patients with severe and complex obesity.
Abstract
The challenge of managing the epidemic of patients with severe and complex obesity disease in secondary care is largely unmet. In England, the National Institute of Health and Care Excellence and the National Health Service England have published guidance on the provision of specialist (non-surgical) weight management services. We have undertaken a systematic review of 'what evidence exists for what should happen in/commissioning of: primary or secondary care weight assessment and management clinics in patients needing specialist care for severe and complex obesity?' using an accredited methodology to produce a model for organization of multidisciplinary team clinics that could be developed in every healthcare system, as an update to a previous review. Additions to the previous guidance were multidisciplinary team pathways for children/adolescent patients and their transition to adult care, anaesthetic assessment and recommendations for ongoing shared care with general practitioners, as a chronic disease management pathway.
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Headache Associated with Coeliac Disease: A Systematic Review and Meta-Analysis.
Zis, P, Julian, T, Hadjivassiliou, M
Nutrients. 2018;10(10)
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Coeliac disease (CD) is the best-recognised gluten-related disorder (GRD), and it is characterized by a small bowel enteropathy occurring in genetically susceptible individuals whilst exposed to the protein gliadin. The aim of this study was to systematically review the current literature in order to establish the relationship between headache and CD. This study is a systematic review of 40 articles, studying a total of 42,388 individuals with either headache or GRD. Results show that: - There is an increased prevalence of headache amongst patients with CD. - There is an increased prevalence of CD amongst patients with idiopathic headache. - Headaches associated with CD are mainly migraines. - Gluten-free diet is a very effective treatment for headaches associated with CD. Authors conclude that further studies on the prevalence of gluten sensitivity in patients with idiopathic headache are needed, including further research on the pathogenetic mechanisms.
Abstract
OBJECTIVE The aim of this systematic review was to explore the relationship between coeliac disease (CD) and headache. The objectives were to establish the prevalence of each entity amongst the other, to explore the role of gluten free diet (GFD), and to describe the imaging findings in those affected by headaches associated with CD. METHODOLOGY A systematic computer-based literature search was conducted on the PubMed database. Information regarding study type, population size, the age group included, prevalence of CD amongst those with headache and vice versa, imaging results, the nature of headache, and response to GFD. RESULTS In total, 40 articles published between 1987 and 2017 qualified for inclusion in this review. The mean pooled prevalence of headache amongst those with CD was 26% (95% CI 19.5⁻33.9%) in adult populations and 18.3% (95% CI 10.4⁻30.2%) in paediatric populations. The headaches are most often migraine-like. In children with idiopathic headache, the prevalence of CD is 2.4% (95% CI 1.5⁻3.7%), whereas data for adult populations is presently unavailable. Brain imaging can be normal, although, cerebral calcifications on CT, white matter abnormalities on MRI and deranged regional cerebral blood flow on SPECT can be present. GFD appears to be an effective management for headache in the context of CD, leading to total resolution of headaches in up to 75% of patients. CONCLUSIONS There is an increased prevalence of CD amongst idiopathic headache and vice versa. Therefore, patients with headache of unknown origin should be screened for CD, as such patients may symptomatically benefit from a GFD.
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Nutritional strategies for psoriasis: current scientific evidence in clinical trials.
Zuccotti, E, Oliveri, M, Girometta, C, Ratto, D, Di Iorio, C, Occhinegro, A, Rossi, P
European review for medical and pharmacological sciences. 2018;22(23):8537-8551
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Psoriasis is an inflammatory skin disease that results in patches of dry, scaly skin that can be itchy or sore. This review looked at the evidence for a variety of nutritional and herbal strategies for reducing the risk and severity of psoriasis. Obesity is associated with both an increased risk of psoriasis, and increased severity of the disease, with obese patients being twice as likely to suffer from psoriasis as people of normal weight. Abdominal obesity in particular is associated with chronic low-grade inflammation that contributes to immune dysregulation. In obese patients, weight reduction via a low-calorie diet has been shown to reduce the severity of psoriasis. A Mediterranean-style diet, rich in extra virgin olive oil, fish, fruit vegetables, legumes, nuts and seeds is associated with a lower incidence of psoriasis. In contrast, a diet high in simple carbohydrates, high in arachidonic acid, and a low omega 3: omega 6 ratio is likely to drive inflammation, worsening severity of the disease. The microbiota plays a role in the development of psoriasis, with disruption of the gut and skin microbiomes both associated with psoriasis. In particular, psoriasis patients have a reduced abundance of Akkermansia muciniphilia in their gut. Several Lactobacillus strains have demonstrated potential for therapeutic effects in psoriasis patients when taken as a supplement. Common nutritional supplements used by psoriasis patients are fish oil, selenium, and zinc. In a review of the efficacy of fish oil supplementation, 12 of 15 trials showed a benefit. The evidence for zinc supplementation is less robust. There is limited data on the effectiveness of selenium supplementation, however low serum selenium levels are associated with increased psoriasis severity. Vitamin D levels are lower in psoriasis patients and correlate with disease severity. In individuals who are deficient, supplementing with vitamin D may prevent psoriasis-related comorbidities. Amongst the herbal and botanical remedies studied, neem, turmeric, Tripterygium wilfordii (Thunder God Vine), and the carotenoid-rich alga Dunaliella bardawil may reduce the severity of psoriasis. The review authors concluded that an integrated multidisciplinary approach should be considered for the management of psoriasis patients. Education to modify lifestyle and environmental risk factors is important. A collaboration between nutritionists and medical specialists with a holistic approach may be useful for psoriasis patients.
Abstract
OBJECTIVE Several nutritional strategies for the management of psoriasis are promising. Even if recent data support that nutrition may play a pivotal role in prevention and co-treatment and despite patient's concerns regarding the best nutritional habits, the consensus regarding the nutritional strategies to be adopted lacks in clinical settings. In this manuscript, the effects of several nutritional strategies for psoriasis patients such as hypocaloric diet, vitamin D, fish oil, selenium, and zinc supplementation were systematically reviewed. Randomized controlled trials (RCTs) on beneficial botanical oral supplements were also included in the analysis. MATERIALS AND METHODS For each topic, a search was conducted in MEDLINE electronic databases for articles published in English between January 1, 1990 and September 2018. Two independent reviewers assessed and extracted the data. Only controlled clinical trials were selected. RESULTS The evidence regarding the current nutritional strategies for psoriasis patients were summarized and translated into a global, comprehensible recommendation. CONCLUSIONS Weight loss combined with a healthy lifestyle was shown to be very beneficial for patients with moderate to severe disease with a significant reduction of the Psoriasis Area and Severity Index (PASI) score. Currently, oral vitamin D supplementation for prevention or treatment of psoriasis in adults with normal vitamin D levels is not recommended; however, psoriasis patients with a deficit in plasma vitamin D levels are advised to complement with oral supplements to prevent psoriasis-related comorbidities. Instead of zinc, selenium, and omega 3 supplements have been proven beneficial for psoriasis patients. Among botanical species, Dunaliella bardawil (D. bardawil), Tripterygium wilfordii (T. wilfordii), Azadirachta indica (A. indica), Curcuma longa (C. longa), and HESA-A are the most beneficial. In conclusion, a close cooperation between nutritionists and dermatologists may be useful for the management of psoriasis.
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Body mass index, abdominal fatness, weight gain and the risk of psoriasis: a systematic review and dose-response meta-analysis of prospective studies.
Aune, D, Snekvik, I, Schlesinger, S, Norat, T, Riboli, E, Vatten, LJ
European journal of epidemiology. 2018;33(12):1163-1178
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Psoriasis is an immune-mediated inflammatory skin disease characterised by red, itchy, scaly and flaky skin. Research has shown an association between adiposity and inflammation cytokine release triggered by adipose tissue and increased body mass index and psoriasis. In this meta-analysis, seven prospective studies were included, and the association between BMI, abdominal fat, and psoriasis was examined. According to this meta-analysis, the relative risk of psoriasis increases by 19% for every 5-unit increase in BMI, 24% for a 10 cm increase in waist circumference, 37% for a 0.1-unit increase in waist-to-hip ratio, and 11% for a 5 kg weight gain. The risk of psoriasis was lower for people with a BMI below 20, and it was significantly higher for those with a BMI between 22.5-24. Psoriasis risk was positively associated with waist circumference, waist-to-hip ratio, and weight gain. Psoriasis risk escalates by 2-4 times with an increase in each measure of adiposity. Several potential strategies to reduce the risk of psoriasis are identified in this meta-analysis, including weight loss, dietary factors, and physical activity. To evaluate their effectiveness and develop appropriate strategies, further robust studies are needed. Healthcare professionals can use the results of this study to develop potential therapeutic strategies to reduce the risk of psoriasis by understanding the mechanisms and factors associated with the disease.
Abstract
Greater body mass index (BMI) has been associated with increased risk of psoriasis in case-control and cross-sectional studies, however, the evidence from prospective studies has been limited. We conducted a systematic review and dose-response meta-analysis of different adiposity measures and the risk of psoriasis to provide a more robust summary of the evidence based on data from prospective studies. PubMed and Embase databases were searched for relevant studies up to August 8th 2017. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using a random effects model. The summary relative risk (RR) for a 5 unit increment in BMI was 1.19 (95% CI 1.10-1.28, I2 = 83%, n = 7). The association appeared to be stronger at higher compared to lower levels of BMI, pnonlinearity < 0.0001, and the lowest risk was observed at a BMI around 20. The summary RR was 1.24 (95% CI 1.17-1.31, I2 = 0%, pheterogeneity = 0.72, n = 3) per 10 cm increase in waist circumference, 1.37 (95% CI 1.23-1.53, I2 = 0%, pheterogeneity = 0.93, n = 3) per 0.1 unit increase in waist-to-hip ratio, and 1.11 (95% CI 1.07-1.16, I2 = 47%, pheterogeneity = 0.15, n = 3) per 5 kg of weight gain. Adiposity as measured by BMI, waist circumference, waist-to-hip ratio, and weight gain is associated with increased risk of psoriasis.
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Dairy product consumption and risk of hip fracture: a systematic review and meta-analysis.
Bian, S, Hu, J, Zhang, K, Wang, Y, Yu, M, Ma, J
BMC public health. 2018;18(1):165
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Dairy products contain calcium and Vitamin D, two elements that are known to support bone health. The consumption of dairy products therefore, may affect the risk of bone fracture, however the research remains inconclusive. This meta-analysis examined and quantified the potential association between dairy consumption and the risk of hip fracture. The final analysis included 10 cohort studies and 8 case-control studies. After pooling the data from these studies, the researchers concluded that: • Consumption of yoghurt and cheese was associated with a lower risk of hip fracture • Consumption of total dairy products and cream was not significantly associated with the risk of hip fracture • There was insufficient evidence to deduce an association between milk consumption and the risk of hip fracture. 200g of milk per day may be beneficial however the effects of higher volumes were unclear.
Abstract
BACKGROUND Dairy product consumption may affect the risk of hip fracture, but previous studies have reported inconsistent findings. The primary aim of our meta-analysis was to examine and quantify the potential association of dairy product consumption with risk of hip fracture. METHODS We searched the databases of PubMed and EMBASE for relevant articles from their inception through April 17, 2017. The final analysis included 10 cohort studies and 8 case-control studies. Random-effects models were used to estimate the pooled risk. Subgroup and dose-response analyses were conducted to explore the relationships between the consumption of milk and the risk of hip fracture. RESULTS After pooling the data from the included studies, the summary relative risk (RR) for hip fracture for highest versus lowest consumption were 0.91 (95% CI: 0.74-1.12), 0.75 (95% CI: 0.66-0.86), 0.68 (95% CI: 0.61-0. 77), 1.02 (95% CI: 0.93-1.12) for milk, yogurt, cheese, and total dairy products in cohort studies, respectively. Higher milk consumption [Odds ratio (OR), 0.71, 95% CI: 0.55-0. 91] was associated with lower risk of hip fracture for highest versus lowest consumption in case-control studies. After quantifying the specific dose of milk, the summary RR/OR for an increased milk consumption of 200 g/day was 1.00 (95% CI: 0.94-1.07), and 0.89 (95%CI: 0.64-1.24) with significant heterogeneity for cohort and case-control studies, respectively; There was a nonlinear association between milk consumption and hip fracture risk in cohort, and case-control studies. CONCLUSIONS Our findings indicate that consumption of yogurt and cheese was associated with lower risk of hip fracture in cohort studies. However, the consumption of total dairy products and cream was not significantly associated with the risk of hip fracture. There was insufficient evidence to deduce the association between milk consumption and risk of hip fracture. A lower threshold of 200 g/day milk intake may have beneficial effects, whereas the effects of a higher threshold of milk intake are unclear.
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Systematic review of palm oil consumption and the risk of cardiovascular disease.
Ismail, SR, Maarof, SK, Siedar Ali, S, Ali, A
PloS one. 2018;13(2):e0193533
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Palm oil, the most widely consumed vegetable oil in the world, derives from the palm tree fruit with a balanced ratio of unsaturated and saturated fatty acids. Studies have shown an association between high contents of saturated fats in palm oil with the detrimental atherogenic profile. The review aims at synthesising the available evidence reporting the association of palm oil consumption with cardiovascular disease risk and cardiovascular disease-specific mortality, including specifically Coronary Heart Disease (CHD) and stroke. The authors systematically searched three databases up to June 2017 without restriction on setting or language. Published interventional and observational studies that evaluated palm oil consumption with coronary heart disease or stroke in adults were searched. Separate searches were performed depending on the outcome. The study did not find a clear association between palm oil consumption and risk or mortality of cardiovascular disease, namely coronary heart disease and stroke. The health effects found between association of palm oil consumption and risk of coronary heart disease were not unique to just palm oil consumption as other food items were also included in the analysis. The review could not establish strong evidence for or against palm oil consumption relating to cardiovascular disease risk and cardiovascular disease-specific mortality. A healthy overall diet is suggested for good cardiometabolic health.
Abstract
BACKGROUND The high amount of saturated fatty acids (SFA) coupled with the rising availability and consumption of palm oil have lead to the assumption that palm oil contributes to the increased prevalence of cardiovascular diseases worldwide. We aimed at systematically synthesising the association of palm oil consumption with cardiovascular disease risk and cardiovascular disease-specific mortality. METHODS We systematically searched Central, Medline and Embase databases up to June 2017 without restriction on setting or language. We performed separate searches based on the outcomes: coronary heart disease and stroke, using keywords related to these outcomes and palm oil. We searched for published interventional and observational studies in adults (Age: >18 years old). Two investigators extracted data and a consensus was reached with involvement of a third. Only narrative synthesis was performed for all of the studies, as the data could not be pooled. RESULTS Our search retrieved 2,738 citations for stroke with one included study and 1,777 citations for coronary heart disease (CHD) with four included studies. Palmitic acid was reported to be associated with risk of myocardial infarction (MI) (OR 2.76; 95%CI = 1.39-5.47). Total SFA intake was reported to be not significant for risk of MI. Varying intake of fried foods, highest contributor to total SFA with 36% of households using palm oil for frying, showed no significant associations to risk of MI. Odds of developing first non-fatal acute MI was higher in palm oil compared to soybean oil with 5% trans-fat (OR = 1.33; 95%CI = 1.09-1.62) than palm oil compared to soybean oil with 22% trans-fat (OR = 1.16; 95%CI = 0.86-1.56). Nevertheless, these risk estimates were non-significant and imprecise. The trend amongst those taking staple pattern diet (characterised by higher palm oil, red meat and added sugar consumption) was inconsistent across the factor score quintiles. During the years of 1980 and 1997, for every additional kilogram of palm oil consumed per-capita annually, CHD mortality risk was 68 deaths per 100,000 (95% CI = 21-115) in developing countries and 17 deaths per 100,000 (95%CI = 5.3-29) in high-income countries, whereas stroke was associated with 19 deaths per 100,000 (95%CI = -12-49) and 5.1 deaths per 100,000 (95% CI: -1.2-11) respectively. The evidence for the outcomes of this review were all graded as very low. The findings of this review should be interpreted with some caution, owing to the lack of a pooled effect estimate of the association, significant bias in selection criteria and confounding factors, inclusion of other food items together with palm oil, and the possible out-dated trend in the ecological study. CONCLUSION In view of the abundance of palm oil in the market, quantifying its true association with CVD outcomes is challenging. The present review could not establish strong evidence for or against palm oil consumption relating to cardiovascular disease risk and cardiovascular disease-specific mortality. Further studies are needed to establish the association of palm oil with CVD. A healthy overall diet should still be prioritised for good cardiometabolic health.
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Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis.
Grgic, J, Trexler, ET, Lazinica, B, Pedisic, Z
Journal of the International Society of Sports Nutrition. 2018;15:11
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The possible physical performance enhancing (or 'ergogenic) effects of caffeine have been extensively studied since the early 1900s. Recent focus has shifted to its impact on anaerobic physical performance outcomes such as muscular strength, endurance and jumping tasks that require power. Although it has been found to enhance muscle endurance, less is known about its impact on strength and power. This is the first meta-analysis on caffeine and muscle power, and includes 20 studies - ten on muscle strength outcomes and ten on muscle power. The analysis found that caffeine significantly improves muscle strength (SMD = 0.20; 95% confidence interval [CI]: 0.03, 0.36; p = 0.023) but only for upper and not lower body strength. These results were found for men but more robust studies are needed to examine the impact for women (although the limited research suggests there may be a positive impact). This is in contrast to a previous meta-analysis that found no impact of caffeine on muscle strength (Polito, Souza, Casonatto & Farinatti, 2016). It was also found to significantly improve muscle power (SMD = 0.17; 95% CI: 0.00, 0.34; p = 0.047). Although the pooled effect of caffeine on performance outcomes was small to medium, even small improvements can make a big difference competitively. Future research is needed to identify the best dosage and form of caffeine to maximise its performance enhancing effects. Additionally, more robust research is needed to reduce bias, and studies including women. It is important to recognise that individual physical performance changes as a result of caffeine are variable, so these findings must be applied on a case-by-case basis. * Polito MD, Souza DB, Casonatto J, Farinatti P. Acute effect of caffeine consumption on isotonic muscular strength and endurance: a systematic review and meta-analysis. Sci Sports. 2016;31:119–28.
Abstract
BACKGROUND Caffeine is commonly used as an ergogenic aid. Literature about the effects of caffeine ingestion on muscle strength and power is equivocal. The aim of this systematic review and meta-analysis was to summarize results from individual studies on the effects of caffeine intake on muscle strength and power. METHODS A search through eight databases was performed to find studies on the effects of caffeine on: (i) maximal muscle strength measured using 1 repetition maximum tests; and (ii) muscle power assessed by tests of vertical jump. Meta-analyses of standardized mean differences (SMD) between placebo and caffeine trials from individual studies were conducted using the random effects model. RESULTS Ten studies on the strength outcome and ten studies on the power outcome met the inclusion criteria for the meta-analyses. Caffeine ingestion improved both strength (SMD = 0.20; 95% confidence interval [CI]: 0.03, 0.36; p = 0.023) and power (SMD = 0.17; 95% CI: 0.00, 0.34; p = 0.047). A subgroup analysis indicated that caffeine significantly improves upper (SMD = 0.21; 95% CI: 0.02, 0.39; p = 0.026) but not lower body strength (SMD = 0.15; 95% CI: -0.05, 0.34; p = 0.147). CONCLUSION The meta-analyses showed significant ergogenic effects of caffeine ingestion on maximal muscle strength of upper body and muscle power. Future studies should more rigorously control the effectiveness of blinding. Due to the paucity of evidence, additional findings are needed in the female population and using different forms of caffeine, such as gum and gel.