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Reducing meat and/or dairy consumption in adults: a systematic review and meta-analysis of effects on protein intake, anthropometric values, and body composition.
Habumugisha, T, Engebretsen, IMS, Måren, IE, Kaiser, CWM, Dierkes, J
Nutrition reviews. 2024;82(3):277-301
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Reduced consumption of meat and dairy is being encouraged over climate change fears, and health implications. However, meat and dairy provide high quality protein and nutrients and concerns have grown over nutrient deficiencies in people on plant-based diets. This systematic review and meta-analysis of 19 randomised control trials (RCTs) aimed to determine the effect of a reduced meat/dairy diet in protein intake, and body shape and composition. The results showed that the RCTs included ran for a median duration of 12 weeks. Participants on a reduced meat/dairy diet had lower protein intakes, and reduced meat/dairy diet had no effect on body weight, body mass index, waist circumference, body fat, or muscle mass. It was concluded that a low meat/dairy diet decreases protein intake, however it does not affect body shape, or composition. It was also concluded that studies of longer duration are warranted to determine long-term effects. This study could be used by healthcare professionals to understand that reduced meat/dairy intake over a moderate period of time may have no effect on body shape or composition but will result in lower protein intakes.
Abstract
CONTEXT Consumers are increasingly encouraged to reduce meat and dairy consumption. However, few meta-analyses of randomized controlled trials (RCTs) on the effect of reducing meat and/or dairy on (absolute) protein intake, anthropometric values, and body composition are available. OBJECTIVE The aim of this systematic review and meta-analysis was to evaluate the effect of reducing meat and/or dairy consumption on (absolute) protein intake, anthropometric values, and body composition in adults aged ≥ 45 years. DATA SOURCES The MEDLINE, Cochrane CENTRAL, Embase, ClinicalTrials.gov, and International Clinical Trials Registry Platform databases were searched up to November 24, 2021. DATA EXTRACTION Randomized controlled trials reporting protein intake, anthropometric values, and body composition were included. DATA ANALYSIS Data were pooled using random-effects models and expressed as the mean difference (MD) with 95%CI. Heterogeneity was assessed and quantified using Cochran's Q and I2 statistics. In total, 19 RCTs with a median duration of 12 weeks (range, 4-24 weeks) and a total enrollment of 1475 participants were included. Participants who consumed meat- and/or dairy-reduced diets had a significantly lower protein intake than those who consumed control diets (9 RCTs; MD, -14 g/d; 95%CI, -20 to -8; I2 = 81%). Reducing meat and/or dairy consumption had no significant effect on body weight (14 RCTs; MD, -1.2 kg; 95%CI, -3 to 0.7; I2 = 12%), body mass index (13 RCTs; MD, -0.3 kg/m2; 95%CI, -1 to 0.4; I2 = 34%), waist circumference (9 RCTs; MD, -0.5 cm; 95%CI, -2.1 to 1.1; I2 = 26%), amount of body fat (8 RCTs; MD, -1.0 kg; 95%CI, -3.0 to 1.0; I2 = 48%), or lean body mass (9 RCTs; MD, -0.4 kg; 95%CI, -1.5 to 0.7; I2 = 0%). CONCLUSION Reduction of meat and/or dairy appears to reduce protein intake. There is no evidence of a significant impact on anthropometric values or body composition. More long-term intervention studies with defined amounts of meat and dairy are needed to investigate the long-term effects on nutrient intakes and health outcomes. SYSTEMATIC REVIEW REGISTRATION PROSPERO registration no. CRD42020207325.
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An updated systematic review and meta-analysis on adherence to mediterranean diet and risk of cancer.
Morze, J, Danielewicz, A, Przybyłowicz, K, Zeng, H, Hoffmann, G, Schwingshackl, L
European journal of nutrition. 2021;60(3):1561-1586
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The development of cancer is associated with a number of risk factors, including smoking, obesity, sedentary lifestyles, alcohol consumption, infections, pollution, and dietary imbalances. Based on previous research, optimal consumption of fruits, vegetables, and whole grains, along with reduced consumption of red and processed meat, reduces cancer risk. According to this systematic review and meta-analysis, adherence to the Mediterranean diet is associated with lower cancer mortality and site-specific cancer development. A Mediterranean diet includes fruits, vegetables, nuts, legumes, fish, whole grains, extra virgin olive oil, and low amounts of red meat, processed meat, egg, and dairy, along with moderate amounts of red wine. According to this systematic review and meta-analysis, adherence to the Mediterranean diet reduces the risk of cancer mortality and the risk of developing cancers specific to the site, such as colorectal cancer, bladder cancer, gastric cancer, and lung cancer. Among the components of the Mediterranean diet, fruits, vegetables, and whole grains have been shown to reduce cancer risk. Bioactive substances found in Mediterranean diet components require additional robust studies to evaluate their benefits. A healthcare professional can use the results of this study to make clinical decisions and recommend therapeutic interventions to cancer patients.
Abstract
PURPOSE The aim of current systematic review was to update the body of evidence on associations between adherence to the Mediterranean diet (MedDiet) and risk of cancer mortality, site-specific cancer in the general population; all-cause, and cancer mortality as well as cancer reoccurrence among cancer survivors. METHODS A literature search for randomized controlled trials (RCTs), case-control and cohort studies published up to April 2020 was performed using PubMed and Scopus. Study-specific risk estimates for the highest versus lowest adherence to the MedDiet category were pooled using random-effects meta-analyses. Certainty of evidence from cohort studies and RCTs was evaluated using the NutriGrade scoring system. RESULTS The updated search revealed 44 studies not identified in the previous review. Altogether, 117 studies including 3,202,496 participants were enclosed for meta-analysis. The highest adherence to MedDiet was inversely associated with cancer mortality (RRcohort: 0.87, 95% CI 0.82, 0.92; N = 18 studies), all-cause mortality among cancer survivors (RRcohort: 0.75, 95% CI 0.66, 0.86; N = 8), breast (RRobservational: 0.94, 95% CI 0.90, 0.97; N = 23), colorectal (RRobservational: 0.83, 95% CI 0.76, 0.90; N = 17), head and neck (RRobservational: 0.56, 95% CI 0.44, 0.72; N = 9), respiratory (RRcohort: 0.84, 95% CI 0.76, 0.94; N = 5), gastric (RRobservational: 0.70, 95% CI 0.61, 0.80; N = 7), bladder (RRobservational: 0.87, 95% CI 0.76, 0.98; N = 4), and liver cancer (RRobservational: 0.64, 95% CI 0.54, 0.75; N = 4). Adhering to MedDiet did not modify risk of blood, esophageal, pancreatic and prostate cancer risk. CONCLUSION In conclusion, our results suggest that highest adherence to the MedDiet was related to lower risk of cancer mortality in the general population, and all-cause mortality among cancer survivors as well as colorectal, head and neck, respiratory, gastric, liver and bladder cancer risks. Moderate certainty of evidence from cohort studies suggest an inverse association for cancer mortality and colorectal cancer, but most of the comparisons were rated as low or very low certainty of evidence.
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Dietary Patterns and Interventions to Alleviate Chronic Pain.
Dragan, S, Șerban, MC, Damian, G, Buleu, F, Valcovici, M, Christodorescu, R
Nutrients. 2020;12(9)
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A common symptom of many conditions is pain, with chronic pain being a significant cause of emotional distress and disability. Chronic pain is associated with a pro-inflammatory state. Diet interventions can be a helpful tool for the management of chronic pain and its associated inflammation. The increase of nutrient-dense, antioxidant-rich foods and the reduction of pro-inflammatory foods, as well as correcting nutrient deficiencies, all appear to have a positive effect on pain. Whilst previous research on the impact of diet therapy in chronic pain yielded varied results, the authors of this article sought to analyse the most important literature to gain more clarity and direction for future research. After a detailed introduction on the different types of pain, the article summarises the outcome of a range of dietary interventions for chronic pain management. These include calorie restriction and fasting, polyunsaturated fatty acids, low-fat plant-based diets, high protein diet, elimination diet, antioxidants and vitamins including vitamin D, fruits and fibres, prebiotics and probiotics. In the discussion, a helpful table presents the key results organised by type of pain (chronic musculoskeletal pain, chronic headache, neuropathic pain, chronic abdominal pain) and the clinical interventions that showed positive outcomes. In conclusion, diet interventions could be part of a multidisciplinary approach in the management of chronic pain. This article yields an oversight of the possible interventions to consider when supporting people with different types of chronic pain.
Abstract
Pain is one of the main problems for modern society and medicine, being the most common symptom described by almost all patients. When pain becomes chronic, the life of the patients is dramatically affected, being associated with significant emotional distress and/or functional disability. A complex biopsychosocial evaluation is necessary to better understand chronic pain, where good results can be obtained through interconnected biological, psychological, and social factors. The aim of this study was to find the most relevant articles existent in the PubMed database, one of the most comprehensive databases for medical literature, comprising dietary patterns to alleviate chronic pain. Through a combined search using the keywords "chronic pain" and "diet" limited to the last 10 years we obtained 272 results containing the types of diets used for chronic pain published in the PubMed database. Besides classical and alternative methods of treatment described in literature, it was observed that different diets are also a valid solution, due to many components with antioxidant and anti-inflammatory qualities capable to influence chronic pain and to improve the quality of life. Thirty-eight clinical studies and randomized controlled trials are analyzed, in an attempt to characterize present-day dietary patterns and interventions to alleviate chronic pain.
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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
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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.
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Plant-Based Diets for Cardiovascular Safety and Performance in Endurance Sports.
Barnard, ND, Goldman, DM, Loomis, JF, Kahleova, H, Levin, SM, Neabore, S, Batts, TC
Nutrients. 2019;11(1)
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Studies suggest that endurance athletes are at higher risk of some types of heart disease. This review looked at the ability of plant-based diets to reduce risk and affect athletic performance. The authors found evidence that plant-based diets are associated with beneficial effects on health, such as reducing body fat, blood pressure, cholesterol, oxidative stress and inflammation. The authors of this review argue that there is a sound scientific basis for recommending plant-based diets to endurance athletes.
Abstract
Studies suggest that endurance athletes are at higher-than-average risk for atherosclerosis and myocardial damage. The ability of plant-based regimens to reduce risk and affect performance was reviewed. The effect of plant-based diets on cardiovascular risk factors, particularly plasma lipid concentrations, body weight, and blood pressure, and, as part of a healthful lifestyle, reversing existing atherosclerotic lesions, may provide a substantial measure of cardiovascular protection. In addition, plant-based diets may offer performance advantages. They have consistently been shown to reduce body fat, leading to a leaner body composition. Because plants are typically high in carbohydrate, they foster effective glycogen storage. By reducing blood viscosity and improving arterial flexibility and endothelial function, they may be expected to improve vascular flow and tissue oxygenation. Because many vegetables, fruits, and other plant-based foods are rich in antioxidants, they help reduce oxidative stress. Diets emphasizing plant foods have also been shown to reduce indicators of inflammation. These features of plant-based diets may present safety and performance advantages for endurance athletes. The purpose of this review was to explore the role of nutrition in providing cardioprotection, with a focus on plant-based diets previously shown to provide cardiac benefits.
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Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis.
Seidelmann, SB, Claggett, B, Cheng, S, Henglin, M, Shah, A, Steffen, LM, Folsom, AR, Rimm, EB, Willett, WC, Solomon, SD
The Lancet. Public health. 2018;3(9):e419-e428
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Previous trials have shown that low carbohydrate diets are beneficial for short-term weight loss. However, the long-term impact of carbohydrate restriction on mortality is less clear, with research producing conflicting results. Additionally, previous studies have not addressed the source or quality of proteins and fats consumed in low-carbohydrate diets. This study aimed to find out whether there is an association between carbohydrate consumption and mortality. It also looked at whether animal-based or plant-based foods had any impact on the association. The researchers began by studying over 15,000 adults in the US, enrolled between 1987 and 1989. At the start of the study and again six years later, participants completed food frequency questionnaires. These were used to estimate the percentage of calories they derived from carbohydrate, fat and protein. The results showed a U-shape association between overall carbohydrate intake and life expectancy, with low (less than 40% of calories from carbohydrates) and high (more than 70%) intake of carbohydrates associated with a higher risk of mortality compared with moderate intake (50-55% of calories). The researchers estimated that the average life expectancy was 4 years shorter for those with low carbohydrate consumption, and 1 year shorter for those with high carbohydrate consumption, compared to those with a moderate carbohydrate intake. However, the authors point out that since diets were only recorded at the start of the trial and six years later, participants’ diets could have changed during the 25-year follow-up period. Next, the authors performed a meta-analysis of data from eight previous studies. This revealed similar trends, with participants whose overall diets were high and low in carbohydrates having a shorter life expectancy than those with moderate consumption. In further analyses examining the source of proteins and fats, animal-derived protein and fat sources, such as lamb, beef, pork and chicken, were associated with higher mortality, whereas plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter and whole-grains, were associated with lower mortality. The authors suggest that, when restricting carbohydrate intake, replacement of carbohydrates with predominantly plant-based fats and proteins could be considered as a long-term approach to promote healthy ageing.
Abstract
BACKGROUND Low carbohydrate diets, which restrict carbohydrate in favour of increased protein or fat intake, or both, are a popular weight-loss strategy. However, the long-term effect of carbohydrate restriction on mortality is controversial and could depend on whether dietary carbohydrate is replaced by plant-based or animal-based fat and protein. We aimed to investigate the association between carbohydrate intake and mortality. METHODS We studied 15 428 adults aged 45-64 years, in four US communities, who completed a dietary questionnaire at enrolment in the Atherosclerosis Risk in Communities (ARIC) study (between 1987 and 1989), and who did not report extreme caloric intake (<600 kcal or >4200 kcal per day for men and <500 kcal or >3600 kcal per day for women). The primary outcome was all-cause mortality. We investigated the association between the percentage of energy from carbohydrate intake and all-cause mortality, accounting for possible non-linear relationships in this cohort. We further examined this association, combining ARIC data with data for carbohydrate intake reported from seven multinational prospective studies in a meta-analysis. Finally, we assessed whether the substitution of animal or plant sources of fat and protein for carbohydrate affected mortality. FINDINGS During a median follow-up of 25 years there were 6283 deaths in the ARIC cohort, and there were 40 181 deaths across all cohort studies. In the ARIC cohort, after multivariable adjustment, there was a U-shaped association between the percentage of energy consumed from carbohydrate (mean 48·9%, SD 9·4) and mortality: a percentage of 50-55% energy from carbohydrate was associated with the lowest risk of mortality. In the meta-analysis of all cohorts (432 179 participants), both low carbohydrate consumption (<40%) and high carbohydrate consumption (>70%) conferred greater mortality risk than did moderate intake, which was consistent with a U-shaped association (pooled hazard ratio 1·20, 95% CI 1·09-1·32 for low carbohydrate consumption; 1·23, 1·11-1·36 for high carbohydrate consumption). However, results varied by the source of macronutrients: mortality increased when carbohydrates were exchanged for animal-derived fat or protein (1·18, 1·08-1·29) and mortality decreased when the substitutions were plant-based (0·82, 0·78-0·87). INTERPRETATION Both high and low percentages of carbohydrate diets were associated with increased mortality, with minimal risk observed at 50-55% carbohydrate intake. Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality. FUNDING National Institutes of Health.