Cross-continental national nutrition surveys: a narrative review.

Many countries use national nutrition surveys (NNSs) to assess their population's health and nutrition needs. However, NNS aims, approaches, tools, and measurements vary among countries. To date, there has been no review evaluating the NNSs and their practices worldwide to help conduct future NSSs. Therefore, this narrative review was conducted to 1) explore and tabulate current NNSs in five continents (Asia, Europe, Africa, North America, and Australia) and 2) help lay the foundation for establishing clear guidelines for future NNSs. The NNSs were identified using two approaches. First, an electronic database search was conducted with key terms in PubMed database. Second, a general web-based search on the survey webpages of governmental organizations was conducted using the same key terms to identify eligible surveys. The review included general adult population (≥ 18 years) with a cross-sectional design, excluding NNSs related to household-only surveys, specific age groups, or insufficient sample sizes. A total of 41 NNSs were identified in 37 countries across four continents: Asia (n = 15), Europe (n = 21), North America (n = 3), and Australia (n = 2). Broad differences between the surveys were identified, including survey purposes and designs, definitions of geographic areas and target groups, and dietary assessments. Currently, there are 26 ongoing NNSs, while 15 have ended. Among the ongoing NNSs, the cycles of the surveys were either at regular intervals (n = 8) or irregular intervals (n = 8). Of the 41 surveys, 24-h dietary recalls were used in 27 surveys, while only 6 surveys used diet diaries and 8 surveys relied on FFQs. Some surveys (n = 17) utilized multiple tools to assess dietary intake. Most of the surveys that assessed biochemical status (n = 12) focused on blood glucose, haemoglobin A1c (HbA1c), and lipid status, whereas some surveys (n = 6) tested for vitamin and mineral status in blood and/or urine samples. The review identified key characteristics, time frames, sampling methods, and dietary and physical assessment methods obtained from different surveys worldwide. The information organized in this review will be important for researchers, policymakers, and public health programme developers in developing and improving NNS.

Development and validation of a food frequency questionnaire in adult Saudi subjects in Jeddah city.

BACKGROUND AND AIMS: In Saudi Arabia, very limited studies have been conducted to evaluate the validity of culturally appropriate food frequency questionnaire (FFQ). The aim of this study was to validate a newly designed FFQ against two reference methods in Saudi adults. METHODS: A new FFQ adapted from the Block FFQ was completed via interview and validated against three-day food records (3DFRs; n = 126) and 24-hour urinary urea nitrogen (UUN)-based protein intake estimates (n = 118) in adult Saudis living in Jeddah. FFQ-estimated nutrient intake was compared to the 3DFR and UUN methods using Pearson's correlations (r), Bland-Altman plots, and weighted kappa (κw) statistics. RESULTS: This study included 126 participants (80 females and 46 males). The FFQ generally overreported nutrient intakes compared to the reference methods. The FFQ was strongly correlated with 3DFRs for energy, protein, carbohydrate, and total fat (r > 0.7); moderately correlated with cholesterol (r = 0.55) and iron (r = 0.44); and weakly correlated with the other micronutrients (r = 0.1-0.3). A moderate positive correlation for protein intake was found (r = 0.62) between the FFQ and 24-hour UUN method. The Bland-Altman analysis indicated the FFQ had an acceptable level of agreement with no significant proportional bias (P > 0.05) with the 3DFRs for energy, protein, total fat, and iron and with protein intake. Similarly, an acceptable level of agreement was found between the FFQ and the 24-hour UUN method for estimating protein intake. Cross-classification analysis showed that ≥ 50% of participants were ranked within the same quartile for energy, protein, and total fat. The FFQ showed good agreement with the 3DFRs for energy and protein (κw ≥ 0.61) and acceptable agreement with protein intake. An acceptable agreement was reported between the FFQ and 24-hour UUN method (κw = 0.56). Separate analyses of females and males showed stronger correlations and agreements between the FFQ and the two reference methods only in females. CONCLUSION: The developed FFQ is an effective and valid tool for assessing dietary intake in Saudi adults. However, it still requires future optimization to improve its validity.

Understanding nursing perspective towards barriers to the optimal delivery of enteral nutrition in intensive care settings.

BACKGROUND: The management process of Enteral Nutrition (EN) typically involves the interaction between a team of health care practitioners. Nurses being the closest to the patients, have crucial responsibilities and play a major role in feeding delivery along with other medical treatments. This study was conducted to investigate the perception of the nurses working in adult and paediatric intensive care Units (ICUs) regarding the EN barriers and identify the factors that influenced their perception. METHODS: The data in this cross-sectional study was collected via online survey between 15 October 2021 and January 2022. All nurses working in adult or paediatric ICUs across Saudi Arabia were eligible to participate. The tool used for the data collection was adapted from Cahill et al. (2016) and then reviewed and modified by the researchers. The survey collected information about the demographics of the nurses, and it included 24 potential EN barriers where the participants were asked to rate their importance on a scale from 1 to 5. Descriptive statistics were performed to describe the variables, univariant analysis were performed to compare the perceptions of the nurses regarding the EN barriers based on their characteristics followed by stepwise linear regression analysis. RESULTS: A total of 136 nurses working in adult and paediatric ICUs were included in this study. The results showed that the most important barriers as perceived by the nurses was "Frequent displacement of feeding tube, requiring reinsertion" [3.29 ± 1.28], "Delays in initiating motility agents in patients not tolerating enteral nutrition" [3.27 ± 1.24] and "Enteral formula not available on the unit". [3.27 ± 1.24]. Our results showed that the responses of the participants statistically varied based on their work settings, gender, region, and educational level for some items in the survey (P-value ≤ 0.05). In the regression analysis, gender was the only variable statistically influenced the total Likert rating scores of the participants (r = -0.213, p-value = 0.013). CONCLUSION: This study identified several barriers that exist in the nursing practice of EN in critical care settings. There are distinct differences in the perception of the nurses to these barriers based on their characteristics. Understanding such differences is important for implementing future strategies for units that needed the most help in prioritizing EN delivery.

Low Emulsifier Diet in Healthy Female Adults: A Feasibility Study of Nutrition Education and Counseling Intervention.

Emulsifiers are food additives commonly found in processed foods to improve texture stabilization and food preservation. Dietary emulsifier intake can potentially damage the gut mucosal lining resulting in chronic inflammation such as Crohn's disease. This study investigates the feasibility of a low-emulsifier diet among healthy female adults, as no previous reports have studied the feasibility of such a diet on healthy participants. A quasi-experimental study for a nutrition education and counseling intervention was conducted over 14 days among healthy Saudi participants aged 18 years and over. Assessment of dietary intake using 3-day food records was conducted at the baseline and 2-week follow-up. Participants attended an online educational session using the Zoom application illustrating instructions for a low-emulsifier diet. Daily exposure to emulsifiers was evaluated and nutrient intake was measured. A total of 30 participants completed the study. At baseline, 38 emulsifiers were identified, with a mean ± SD exposure of 12.23 ± 10.07 emulsifiers consumed per day. A significant reduction in the mean frequency of dietary emulsifier intake was observed at the end of the intervention (12.23 ± 10.07 vs. 6.30 ± 7.59, p < 0.01). However, intake of macronutrients and micronutrients was significantly reduced (p < 0.05). Good adherence to the diet was achieved by 40% of the participants, and 16.66% attained a 50% reduction of emulsifier intake. The study demonstrates that a low-emulsifier diet provided via dietary advice is feasible to follow and tolerable by healthy participants. However, the diet still needs further investigation and assessment of it is nutritional intake and quality before implementing it in patients with inflammatory bowel disease who are at high risk of poor nutritional intake.

Exploring the practice of nutritional support during hospitalization across physicians, dietitians, and pharmacists based in Saudi Arabia.

Background: Nutritional support has a pivotal role in preventing and treating malnutrition. Recognizing the gaps in nutritional support practice can aid the development of tailored nutritional protocols. Therefore, this study aimed to assess the current practices, attitudes, and perceptions related to nutritional support for hospitalized patients in one of the largest Middle Eastern countries. Methods: A cross-sectional study was conducted among different healthcare professionals currently working in hospitals in Saudi Arabia and involved in nutritional support practice. Data were collected using convenient sample via a self-administered web-based questionnaire. Results: A total of 114 participants were included in this study. The majority were dietitians (54%), followed by physicians (33%) and pharmacists (12%), and were from the western region (71.9%). Various attitudes in many practices were observed among the participants. Only 44.7% of the participants had a formal nutritional support team. The mean confidence level of all respondents was significantly higher for enteral nutrition practice (7.7 ± 2.3) than for parenteral nutrition practice (6.1 ± 2.5) (p < 0.01). The confidence level for enteral nutrition practice was significantly influenced by nutritional qualification (ß = 0.202, p < 0.05), type of healthcare facility (ß = 0.210, p < 0.05), profession (ß = -0.308, p < 0.01), and years of experience (ß = 0.220, p < 0.05). Conclusion: This study comprehensively assessed various aspects of nutritional support practice in Saudi Arabia. Healthcare practice of nutritional support should be guided by evidence-based guidelines. Professional qualification and training in nutritional support are essential for promoting practice in hospitals.

Enteral Nutrition Prescription in Children and Adults with Inflammatory Bowel Diseases: Gaps in Current Gastroenterology Practice in Saudi Arabia.

Background: Evidence for the effectiveness of enteral nutrition (EN) for the management of patients with inflammatory bowel disease (IBD) is well-established. However, there is considerable global variation in EN practices. This study aimed to characterize the practices and perceptions of gastroenterologists regarding the use of EN in patients with IBD in one of the largest countries in the Gulf region. Methods: A cross-sectional study was conducted on pediatric and adult gastroenterologists working in Saudi Arabia who are involved in IBD management. A self-administered web-based survey was distributed via social media platforms and mailing lists of national gastroenterology societies. Results: A total of 80 gastroenterologists completed the survey. However, only 55 reported that they were currently practicing EN in any form. EN was mostly indicated by gastroenterologists who "sometimes" recommend EN for: the prevention and correction of undernutrition (50.9%), preoperative optimization (50.9%), and the induction of remission in patients with active and long-standing CD (36.4%), at initial diagnosis (34.5%), during the management of complications (61.8%), and after failing to respond to pharmacological therapy (58.2%). Exclusive enteral nutrition (EEN) is regularly recommended by 14.5% of gastroenterologists. The prescription of EEN was significantly associated with the pediatric profession (p < 0.01), IBD specialty (p < 0.05), level of nutrition education during training (p < 0.01), and previous training in a unit with regular EN use (p < 0.01). The most reported barriers to using EN were patients' lack of acceptance (73.8%) and poor adherence (65%). A lack of dietitian support and a lack of standardized protocols were also reported as barriers by many physicians. Pediatric gastroenterologists were more likely to use at least one assessment method to evaluate EN success. Conclusion: EN practices differ between gastroenterologists working in Saudi Arabia. Future EN protocols should be optimized to support both children and adults with IBD. Gastroenterology training programs should offer nutrition support-focused training to help physicians better utilize EN.

A Cross Sectional Survey-Based Study to Investigate the Availability and Utilisation of Home Nutrition Support in Saudi Arabia.

Background and Aims: Many patients require long-term nutrition support, typically in the form of home nutrition support (HNS). The availability and utilisation of HNS in Saudi Arabia is currently unknown; therefore, this study was conducted to assess the availability of HNS in Saudi hospitals and to explore factors associated with the availability of HNS in different healthcare facilities in Saudi Arabia. Methods: A cross-sectional study was conducted among physicians, dietitians, and pharmacists working in Saudi Arabia with regular practice in nutrition support. Data was collected through self-administered web-based survey, which was distributed via social-media platforms. Results: A total of 114 responses were received from healthcare providers involved in nutrition support across Saudi Arabia. Of the respondents, 55 (48.2%) indicated that nutrition support services were available at their facility. Regression analysis showed that other regions in Saudi Arabia had lower odds of having HNS compared with the Western region (OR=0.01; 95% CI=0.01-0.69). The university and specialised hospitals had lower odds of having HNS compared with Ministry of Health hospitals (OR=0.11; 95% CI=0.02-0.71, OR=0.11; 95% CI=0.02-0.56, respectively). Hospitals with capacities of 100-250 beds and 251-500 had higher odds of having HNS than smaller hospitals (OR=13.17; 95% CI=1.09-159.5, OR=3.11; 95% CI=2.04-248.77, respectively). Conclusion: There is lack of published reports from hospitals with implemented HNS. Therefore, it is difficult to assess the current situation of HNS programmes. Future national studies focusing on HNS are warranted as there is a rising international trend in the number of patients requiring HNS.

Effects of fluid and drinking on pneumonia mortality in older adults: A systematic review and meta-analysis.

BACKGROUND AND AIMS: Advice to drink plenty of fluid is common in respiratory infections. We assessed whether low fluid intake (dehydration) altered outcomes in adults with pneumonia. METHODS: We systematically reviewed trials increasing fluid intake and well-adjusted, well-powered observational studies assessing associations between markers of low-intake dehydration (fluid intake, serum osmolality, urea or blood urea nitrogen, urinary output, signs of dehydration) and mortality in adult pneumonia patients (with any type of pneumonia, including community acquired, health-care acquired, aspiration, COVID-19 and mixed types). Medline, Embase, CENTRAL, references of reviews and included studies were searched to 30/10/2020. Studies were assessed for inclusion, risk of bias and data extracted independently in duplicate. We employed random-effects meta-analysis, sensitivity analyses, subgrouping and GRADE assessment. Prospero registration: CRD42020182599. RESULTS: We identified one trial, 20 well-adjusted cohort studies and one case-control study. None suggested that more fluid (hydration) was associated with harm. Ten of 13 well-powered observational studies found statistically significant positive associations in adjusted analyses between dehydration and medium-term mortality. The other three studies found no significant effect. Meta-analysis suggested doubled odds of medium-term mortality in dehydrated (compared to hydrated) pneumonia patients (GRADE moderate-quality evidence, OR 2.3, 95% CI 1.8 to 2.8, 8619 deaths in 128,319 participants). Heterogeneity was explained by a dose effect (greater dehydration increased risk of mortality further), and the effect was consistent across types of pneumonia (including community-acquired, hospital-acquired, aspiration, nursing and health-care associated, and mixed pneumonia), age and setting (community or hospital). The single trial found that educating pneumonia patients to drink ≥1.5 L fluid/d alongside lifestyle advice increased fluid intake and reduced subsequent healthcare use. No studies in COVID-19 pneumonia met the inclusion criteria, but 70% of those hospitalised with COVID-19 have pneumonia. Smaller COVID-19 studies suggested that hydration is as important in COVID-19 pneumonia mortality as in other pneumonias. CONCLUSIONS: We found consistent moderate-quality evidence mainly from observational studies that improving hydration reduces the risk of medium-term mortality in all types of pneumonia. It is remarkable that while many studies included dehydration as a potential confounder, and major pneumonia risk scores include measures of hydration, optimal fluid volume and the effect of supporting hydration have not been assessed in randomised controlled trials of people with pneumonia. Such trials, are needed as potential benefits may be large, rapid and implemented at low cost. Supporting hydration and reversing dehydration has the potential to have rapid positive impacts on pneumonia outcomes, and perhaps also COVID-19 pneumonia outcomes, in older adults.

Long-term effects of increasing omega-3, omega-6 and total polyunsaturated fats on inflammatory bowel disease and markers of inflammation: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND AND AIM: Effects of long-chain omega-3 (LCn3) and omega-6 fatty acids on prevention and treatment of inflammatory bowel diseases (IBD, including Crohn's Disease, CD and ulcerative colitis, UC), and inflammation are unclear. We systematically reviewed long-term effects of omega-3, omega-6 and total polyunsaturated fats (PUFA) on IBD diagnosis, relapse, severity, pharmacotherapy, quality of life and key inflammatory markers. METHODS: We searched Medline, Embase, Cochrane CENTRAL, and trials registries, including RCTs in adults with or without IBD comparing higher with lower omega-3, omega-6 and/or total PUFA intake for ≥ 24 weeks that assessed IBD-specific outcomes or inflammatory biomarkers. RESULTS: We included 83 RCTs (41,751 participants), of which 13 recruited participants with IBD. Increasing LCn3 may reduce risk of IBD relapse (RR 0.85, 95% CI 0.72-1.01) and IBD worsening (RR 0.85, 95% CI 0.71-1.03), and reduce erythrocyte sedimentation rate (ESR, SMD - 0.23, 95% CI - 0.44 to - 0.01), but may increase IBD diagnosis risk (RR 1.10, 95% CI 0.63-1.92), and faecal calprotectin, a specific inflammatory marker for IBD (MD 16.1 µg/g, 95% CI - 37.6 to 69.8, all low-quality evidence). Outcomes for alpha-linolenic acid, omega-6 and total PUFA were sparse, but suggested little or no effect where data were available. CONCLUSION: This is the most comprehensive meta-analysis of RCTs investigating long-term effects of omega-3, omega-6 and total PUFA on IBD and inflammatory markers. Our findings suggest that supplementation with PUFAs has little or no effect on prevention or treatment of IBD and provides little support for modification of long-term inflammatory status.

Effect of fat composition in enteral nutrition for Crohn's disease in adults: A systematic review.

BACKGROUND & AIMS: The role of enteral nutrition (EN) fat composition in regulating inflammation in Crohn's disease (CD) is not clear. There is, moreover, insufficient evidence to guide the choice of EN in CD with any confidence. We have reanalysed the findings of previous studies in a systematic review focussing on the relationship between EN fat content and remission rates (RR). METHODS: A systematic search with no language restriction was undertaken in Medline and Embase databases supplemented by a manual search in the reference lists of identified studies. The selection criteria were: clinical trial, exclusive EN, adults and CD. Data on the type of EN, its fat composition, achieved RR, and study design were extracted. An established assessment tool was used to assess the quality of the studies. RESULTS: A total of 29 clinical trials are included in this review. The quality of the studies was highly variable. No fewer than 27 formulations of enteral feed were identified including 4 elemental and 23 non-elemental preparations. There was a positive correlation between the total n-6 fatty acid content and response rates, which was significant when expressed as the ratio between n-6 and n-3 fatty acids (r = 0.378, p = 0.018). A non-significant positive trend was founded (r = 0.072; p = 0.643) between medium chain triglycerides (MCT) delivery as a percentage of the total energy provision and RR. While a non-significant negative trend was reported for the delivery of monounsaturated fatty acids (MUFA) (r = -0.23, p = 0.13). A qualitative advantage to regimens based on safflower oil suggest that optimised therapeutic approaches are within reach.

Polyunsaturated fatty acids for the primary and secondary prevention of cardiovascular disease.

BACKGROUND: Evidence on the health effects of total polyunsaturated fatty acids (PUFA) is equivocal. Fish oils are rich in omega-3 PUFA and plant oils in omega-6 PUFA. Evidence suggests that increasing PUFA-rich foods, supplements or supplemented foods can reduce serum cholesterol, but may increase body weight, so overall cardiovascular effects are unclear. OBJECTIVES: To assess effects of increasing total PUFA intake on cardiovascular disease and all-cause mortality, lipids and adiposity in adults. SEARCH METHODS: We searched CENTRAL, MEDLINE and Embase to April 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing higher with lower PUFA intakes in adults with or without cardiovascular disease that assessed effects over 12 months or longer. We included full texts, abstracts, trials registry entries and unpublished data. Outcomes were all-cause mortality, cardiovascular disease mortality and events, risk factors (blood lipids, adiposity, blood pressure), and adverse events. We excluded trials where we could not separate effects of PUFA intake from other dietary, lifestyle or medication interventions. DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias. We wrote to authors of included trials for further data. Meta-analyses used random-effects analysis, sensitivity analyses included fixed-effects and limiting to low summary risk of bias. We assessed GRADE quality of evidence. MAIN RESULTS: We included 49 RCTs randomising 24,272 participants, with duration of one to eight years. Eleven included trials were at low summary risk of bias, 33 recruited participants without cardiovascular disease. Baseline PUFA intake was unclear in most trials, but 3.9% to 8% of total energy intake where reported. Most trials gave supplemental capsules, but eight gave dietary advice, eight gave supplemental foods such as nuts or margarine, and three used a combination of methods to increase PUFA.Increasing PUFA intake probably has little or no effect on all-cause mortality (risk 7.8% vs 7.6%, risk ratio (RR) 0.98, 95% confidence interval (CI) 0.89 to 1.07, 19,290 participants in 24 trials), but probably slightly reduces risk of coronary heart disease events from 14.2% to 12.3% (RR 0.87, 95% CI 0.72 to 1.06, 15 trials, 10,076 participants) and cardiovascular disease events from 14.6% to 13.0% (RR 0.89, 95% CI 0.79 to 1.01, 17,799 participants in 21 trials), all moderate-quality evidence. Increasing PUFA may slightly reduce risk of coronary heart disease death (6.6% to 6.1%, RR 0.91, 95% CI 0.78 to 1.06, 9 trials, 8810 participants) andstroke (1.2% to 1.1%, RR 0.91, 95% CI 0.58 to 1.44, 11 trials, 14,742 participants, though confidence intervals include important harms), but has little or no effect on cardiovascular mortality (RR 1.02, 95% CI 0.82 to 1.26, 16 trials, 15,107 participants) all low-quality evidence. Effects of increasing PUFA on major adverse cardiac and cerebrovascular events and atrial fibrillation are unclear as evidence is of very low quality.Increasing PUFA intake probably slightly decreases triglycerides (by 15%, MD -0.12 mmol/L, 95% CI -0.20 to -0.04, 20 trials, 3905 participants), but has little or no effect on total cholesterol (mean difference (MD) -0.12 mmol/L, 95% CI -0.23 to -0.02, 26 trials, 8072 participants), high-density lipoprotein (HDL) (MD -0.01 mmol/L, 95% CI -0.02 to 0.01, 18 trials, 4674 participants) or low-density lipoprotein (LDL) (MD -0.01 mmol/L, 95% CI -0.09 to 0.06, 15 trials, 3362 participants). Increasing PUFA probably has little or no effect on adiposity (body weight MD 0.76 kg, 95% CI 0.34 to 1.19, 12 trials, 7100 participants).Effects of increasing PUFA on serious adverse events such as pulmonary embolism and bleeding are unclear as the evidence is of very low quality. AUTHORS' CONCLUSIONS: This is the most extensive systematic review of RCTs conducted to date to assess effects of increasing PUFA on cardiovascular disease, mortality, lipids or adiposity. Increasing PUFA intake probably slightly reduces risk of coronary heart disease and cardiovascular disease events, may slightly reduce risk of coronary heart disease mortality and stroke (though not ruling out harms), but has little or no effect on all-cause or cardiovascular disease mortality. The mechanism may be via TG reduction.

Omega-6 fats for the primary and secondary prevention of cardiovascular disease.

BACKGROUND: Omega-6 fats are polyunsaturated fats vital for many physiological functions, but their effect on cardiovascular disease (CVD) risk is debated. OBJECTIVES: To assess effects of increasing omega-6 fats (linoleic acid (LA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AA)) on CVD and all-cause mortality. SEARCH METHODS: We searched CENTRAL, MEDLINE and Embase to May 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing higher versus lower omega-6 fat intake in adults with or without CVD, assessing effects over at least 12 months. We included full texts, abstracts, trials registry entries and unpublished studies. Outcomes were all-cause mortality, CVD mortality, CVD events, risk factors (blood lipids, adiposity, blood pressure), and potential adverse events. We excluded trials where we could not separate omega-6 fat effects from those of other dietary, lifestyle or medication interventions. DATA COLLECTION AND ANALYSIS: Two authors independently screened titles/abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias of included trials. We wrote to authors of included studies. Meta-analyses used random-effects analysis, while sensitivity analyses used fixed-effects and limited analyses to trials at low summary risk of bias. We assessed GRADE quality of evidence for 'Summary of findings' tables. MAIN RESULTS: We included 19 RCTs in 6461 participants who were followed for one to eight years. Seven trials assessed the effects of supplemental GLA and 12 of LA, none DGLA or AA; the omega-6 fats usually displaced dietary saturated or monounsaturated fats. We assessed three RCTs as being at low summary risk of bias.Primary outcomes: we found low-quality evidence that increased intake of omega-6 fats may make little or no difference to all-cause mortality (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.88 to 1.12, 740 deaths, 4506 randomised, 10 trials) or CVD events (RR 0.97, 95% CI 0.81 to 1.15, 1404 people experienced events of 4962 randomised, 7 trials). We are uncertain whether increasing omega-6 fats affects CVD mortality (RR 1.09, 95% CI 0.76 to 1.55, 472 deaths, 4019 randomised, 7 trials), coronary heart disease events (RR 0.88, 95% CI 0.66 to 1.17, 1059 people with events of 3997 randomised, 7 trials), major adverse cardiac and cerebrovascular events (RR 0.84, 95% CI 0.59 to 1.20, 817 events, 2879 participants, 2 trials) or stroke (RR 1.36, 95% CI 0.45 to 4.11, 54 events, 3730 participants, 4 trials), as we assessed the evidence as being of very low quality. We found no evidence of dose-response or duration effects for any primary outcome, but there was a suggestion of greater protection in participants with lower baseline omega-6 intake across outcomes.Additional key outcomes: we found increased intake of omega-6 fats may reduce myocardial infarction (MI) risk (RR 0.88, 95% CI 0.76 to 1.02, 609 events, 4606 participants, 7 trials, low-quality evidence). High-quality evidence suggests increasing omega-6 fats reduces total serum cholesterol a little in the long term (mean difference (MD) -0.33 mmol/L, 95% CI -0.50 to -0.16, I2 = 81%; heterogeneity partially explained by dose, 4280 participants, 10 trials). Increasing omega-6 fats probably has little or no effect on adiposity (body mass index (BMI) MD -0.20 kg/m2, 95% CI -0.56 to 0.16, 371 participants, 1 trial, moderate-quality evidence). It may make little or no difference to serum triglycerides (MD -0.01 mmol/L, 95% CI -0.23 to 0.21, 834 participants, 5 trials), HDL (MD -0.01 mmol/L, 95% CI -0.03 to 0.02, 1995 participants, 4 trials) or low-density lipoprotein (MD -0.04 mmol/L, 95% CI -0.21 to 0.14, 244 participants, 2 trials, low-quality evidence). AUTHORS' CONCLUSIONS: This is the most extensive systematic assessment of effects of omega-6 fats on cardiovascular health, mortality, lipids and adiposity to date, using previously unpublished data. We found no evidence that increasing omega-6 fats reduces cardiovascular outcomes other than MI, where 53 people may need to increase omega-6 fat intake to prevent 1 person from experiencing MI. Although benefits of omega-6 fats remain to be proven, increasing omega-6 fats may be of benefit in people at high risk of MI. Increased omega-6 fats reduce serum total cholesterol but not other blood fat fractions or adiposity.

Omega-6 fats for the primary and secondary prevention of cardiovascular disease.

BACKGROUND: Omega-6 fats are polyunsaturated fats vital for many physiological functions, but their effect on cardiovascular disease (CVD) risk is debated. OBJECTIVES: To assess effects of increasing omega-6 fats (linoleic acid (LA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AA)) on CVD and all-cause mortality. SEARCH METHODS: We searched CENTRAL, MEDLINE and Embase to May 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing higher versus lower omega-6 fat intake in adults with or without CVD, assessing effects over at least 12 months. We included full texts, abstracts, trials registry entries and unpublished studies. Outcomes were all-cause mortality, CVD mortality, CVD events, risk factors (blood lipids, adiposity, blood pressure), and potential adverse events. We excluded trials where we could not separate omega-6 fat effects from those of other dietary, lifestyle or medication interventions. DATA COLLECTION AND ANALYSIS: Two authors independently screened titles/abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias of included trials. We wrote to authors of included studies. Meta-analyses used random-effects analysis, while sensitivity analyses used fixed-effects and limited analyses to trials at low summary risk of bias. We assessed GRADE quality of evidence for 'Summary of findings' tables. MAIN RESULTS: We included 19 RCTs in 6461 participants who were followed for one to eight years. Seven trials assessed the effects of supplemental GLA and 12 of LA, none DGLA or AA; the omega-6 fats usually displaced dietary saturated or monounsaturated fats. We assessed three RCTs as being at low summary risk of bias.Primary outcomes: we found low-quality evidence that increased intake of omega-6 fats may make little or no difference to all-cause mortality (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.88 to 1.12, 740 deaths, 4506 randomised, 10 trials) or CVD events (RR 0.97, 95% CI 0.81 to 1.15, 1404 people experienced events of 4962 randomised, 7 trials). We are uncertain whether increasing omega-6 fats affects CVD mortality (RR 1.09, 95% CI 0.76 to 1.55, 472 deaths, 4019 randomised, 7 trials), coronary heart disease events (RR 0.88, 95% CI 0.66 to 1.17, 1059 people with events of 3997 randomised, 7 trials), major adverse cardiac and cerebrovascular events (RR 0.84, 95% CI 0.59 to 1.20, 817 events, 2879 participants, 2 trials) or stroke (RR 1.36, 95% CI 0.45 to 4.11, 54 events, 3730 participants, 4 trials), as we assessed the evidence as being of very low quality. We found no evidence of dose-response or duration effects for any primary outcome, but there was a suggestion of greater protection in participants with lower baseline omega-6 intake across outcomes.Additional key outcomes: we found increased intake of omega-6 fats may reduce myocardial infarction (MI) risk (RR 0.88, 95% CI 0.76 to 1.02, 609 events, 4606 participants, 7 trials, low-quality evidence). High-quality evidence suggests increasing omega-6 fats reduces total serum cholesterol a little in the long term (mean difference (MD) -0.33 mmol/L, 95% CI -0.50 to -0.16, I2 = 81%; heterogeneity partially explained by dose, 4280 participants, 10 trials). Increasing omega-6 fats probably has little or no effect on adiposity (body mass index (BMI) MD -0.20 kg/m2, 95% CI -0.56 to 0.16, 371 participants, 1 trial, moderate-quality evidence). It may make little or no difference to serum triglycerides (MD -0.01 mmol/L, 95% CI -0.23 to 0.21, 834 participants, 5 trials), HDL (MD -0.01 mmol/L, 95% CI -0.03 to 0.02, 1995 participants, 4 trials) or low-density lipoprotein (MD -0.04 mmol/L, 95% CI -0.21 to 0.14, 244 participants, 2 trials, low-quality evidence). AUTHORS' CONCLUSIONS: This is the most extensive systematic assessment of effects of omega-6 fats on cardiovascular health, mortality, lipids and adiposity to date, using previously unpublished data. We found no evidence that increasing omega-6 fats reduces cardiovascular outcomes other than MI, where 53 people may need to increase omega-6 fat intake to prevent 1 person from experiencing MI. Although benefits of omega-6 fats remain to be proven, increasing omega-6 fats may be of benefit in people at high risk of MI. Increased omega-6 fats reduce serum total cholesterol but not other blood fat fractions or adiposity.

Polyunsaturated fatty acids for the primary and secondary prevention of cardiovascular disease.

BACKGROUND: Evidence on the health effects of total polyunsaturated fatty acids (PUFA) is equivocal. Fish oils are rich in omega-3 PUFA and plant oils in omega-6 PUFA. Evidence suggests that increasing PUFA-rich foods, supplements or supplemented foods can reduce serum cholesterol, but may increase body weight, so overall cardiovascular effects are unclear. OBJECTIVES: To assess effects of increasing total PUFA intake on cardiovascular disease and all-cause mortality, lipids and adiposity in adults. SEARCH METHODS: We searched CENTRAL, MEDLINE and Embase to April 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing higher with lower PUFA intakes in adults with or without cardiovascular disease that assessed effects over 12 months or longer. We included full texts, abstracts, trials registry entries and unpublished data. Outcomes were all-cause mortality, cardiovascular disease mortality and events, risk factors (blood lipids, adiposity, blood pressure), and adverse events. We excluded trials where we could not separate effects of PUFA intake from other dietary, lifestyle or medication interventions. DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias. We wrote to authors of included trials for further data. Meta-analyses used random-effects analysis, sensitivity analyses included fixed-effects and limiting to low summary risk of bias. We assessed GRADE quality of evidence. MAIN RESULTS: We included 49 RCTs randomising 24,272 participants, with duration of one to eight years. Eleven included trials were at low summary risk of bias, 33 recruited participants without cardiovascular disease. Baseline PUFA intake was unclear in most trials, but 3.9% to 8% of total energy intake where reported. Most trials gave supplemental capsules, but eight gave dietary advice, eight gave supplemental foods such as nuts or margarine, and three used a combination of methods to increase PUFA.Increasing PUFA intake probably has little or no effect on all-cause mortality (risk 7.8% vs 7.6%, risk ratio (RR) 0.98, 95% confidence interval (CI) 0.89 to 1.07, 19,290 participants in 24 trials), but probably slightly reduces risk of coronary heart disease events from 14.2% to 12.3% (RR 0.87, 95% CI 0.72 to 1.06, 15 trials, 10,076 participants) and cardiovascular disease events from 14.6% to 13.0% (RR 0.89, 95% CI 0.79 to 1.01, 17,799 participants in 21 trials), all moderate-quality evidence. Increasing PUFA may slightly reduce risk of coronary heart disease death (6.6% to 6.1%, RR 0.91, 95% CI 0.78 to 1.06, 9 trials, 8810 participants) andstroke (1.2% to 1.1%, RR 0.91, 95% CI 0.58 to 1.44, 11 trials, 14,742 participants, though confidence intervals include important harms), but has little or no effect on cardiovascular mortality (RR 1.02, 95% CI 0.82 to 1.26, 16 trials, 15,107 participants) all low-quality evidence. Effects of increasing PUFA on major adverse cardiac and cerebrovascular events and atrial fibrillation are unclear as evidence is of very low quality.Increasing PUFA intake slightly reduces total cholesterol (mean difference (MD) -0.12 mmol/L, 95% CI -0.23 to -0.02, 26 trials, 8072 participants) and probably slightly decreases triglycerides (MD -0.12 mmol/L, 95% CI -0.20 to -0.04, 20 trials, 3905 participants), but has little or no effect on high-density lipoprotein (HDL) (MD -0.01 mmol/L, 95% CI -0.02 to 0.01, 18 trials, 4674 participants) or low-density lipoprotein (LDL) (MD -0.01 mmol/L, 95% CI -0.09 to 0.06, 15 trials, 3362 participants). Increasing PUFA probably causes slight weight gain (MD 0.76 kg, 95% CI 0.34 to 1.19, 12 trials, 7100 participants).Effects of increasing PUFA on serious adverse events such as pulmonary embolism and bleeding are unclear as the evidence is of very low quality. AUTHORS' CONCLUSIONS: This is the most extensive systematic review of RCTs conducted to date to assess effects of increasing PUFA on cardiovascular disease, mortality, lipids or adiposity. Increasing PUFA intake probably slightly reduces risk of coronary heart disease and cardiovascular disease events, may slightly reduce risk of coronary heart disease mortality and stroke (though not ruling out harms), but has little or no effect on all-cause or cardiovascular disease mortality. The mechanism may be via lipid reduction, but increasing PUFA probably slightly increases weight.