We aimed to investigate the effectiveness of n-3 fatty acids supplementation on the risk of developing depression, depressive symptoms and remission of depression. We searched PubMed, Scopus and Web of Science from inception to December 2022 to find randomised trials of n-3 fatty acids supplementation in adults. We conducted random-effects meta-analyses to estimate standardised mean differences (SMD) and 95 % CI for continuous outcomes and risk difference and 95 % CI for binary outcomes. A total of sixty-seven trials were included. Each 1 g/d n-3 fatty acids supplementation significantly improved depressive symptoms in adults with and without depression (moderate-certainty evidence), with a larger improvement in patients with existing depression. Dose–response analyses indicated a U-shaped effect in patients with existing depression, with the greatest improvement at 1·5 g/d. The analysis showed that n-3 fatty acid supplementation significantly increased depression remission by 19 more per 100 in patients with depression (low-certainty evidence). Supplementation with n-3 fatty acids did not reduce the risk of developing depression among the general population, but it did improve the severity of depression among patients with existing depression.

The benefits of branched-chain amino acid (BCAA) administration after hepatic intervention in patients with liver diseases remain unclear. We conducted a systematic review and meta-analysis to evaluate the effects of BCAA on patients undergoing hepatectomy, trans-arterial embolisation and radiofrequency ablation. Relevant randomised controlled trials (RCT) were obtained from PubMed, EMBASE and Cochrane Library databases. A meta-analysis was performed to calculate the pooled effect size by using random-effects models. The primary outcomes were survival and tumour recurrence. The secondary outcomes were hospital stay, nutrition status, biochemistry profile, complication rate of liver treatment and adverse effect of BCAA supplementation. In total, eleven RCT involving 750 patients were included. Our meta-analysis showed no significant difference in the rates of tumour recurrence and overall survival between the BCAA and control groups. However, the pooled estimate showed that BCAA supplementation in patients undergoing hepatic intervention significantly increased serum albumin (mean difference (MD): 0·11 g/dl, 95 % CI: 0·02, 0·20; 5 RCT) at 6 months and cholinesterase level (MD: 50·00 U/L, 95 % CI: 21·08, 78·92; 1 RCT) at 12 months and reduced ascites incidence (risk ratio: 0·39, 95 % CI: 0·21, 0·71; 4 RCT) at 12 months compared with the control group. Additionally, BCAA administration significantly increased body weight at 6 months and 12 months and increased arm circumference at 12 months. In conclusion, BCAA supplementation significantly improved the liver function, reduced the incidence of ascites and increased body weight and arm circumference. Thus, BCAA supplementation may beneficial for selected patients undergoing liver intervention.

Diminished skeletal muscle strength and size, termed sarcopenia, contributes substantially to physical disability, falls, dependence and reduced quality of life among older people. Physical activity and nutrition are the cornerstones of sarcopenia prevention and treatment. The optimal daily protein intake required to preserve muscle mass and function among older adults is a topic of intense scientific debate. Older adults require protein intakes about 67 % higher than their younger counterparts to maximally stimulate postprandial muscle protein synthesis rates. In addition, evidence suggests a possible benefit of increasing protein intake above the population reference intake (0⋅83 g/kg/d) on lean mass and, when combined with exercise training, muscle strength. In addition to protein quantity, protein quality, the pattern of protein intake over the day and specific amino acids (i.e. leucine) represent key considerations. Long-chain n-3 PUFA (LC n-3 PUFA) supplementation has been shown to enhance muscle protein synthesis rates, increase muscle mass and function and augment adaptations to resistance training in older adults. Yet, these effects are not consistent across all studies. Emerging evidence indicates that an older person's dietary, phenotypic and behavioural characteristics may modulate the efficacy of protein and LC n-3 PUFA interventions for promoting improvements in muscle mass and function, highlighting the potential inadequacy of a ‘one-size-fits-all’ approach. The application of personalised or precision nutrition to sarcopenia represents an exciting and highly novel field of research with the potential to help resolve inconsistencies in the literature and improve the efficacy of dietary interventions for sarcopenia.

Diarrhoea is common in enterally fed patients and can impact their nutritional and overall outcomes. This meta-analysis evaluates the potential benefits of fibre-supplemented (FS) feeds on incidence of diarrhoea and stool frequency in non-critically ill tube-fed adults. Databases including PubMed, Embase and CINAHL with full text were searched for randomised controlled trials (RCT) with adults on exclusive tube feeding, published until August 2022. The Cochrane Collaboration’s tool was used for quality assessment. Studies with published results on incidence of diarrhoea and stool frequency were analysed using RevMan 5. Thirteen RCT with 847 non-critically ill patients between 20 and 90 years old without diarrhoea at the onset of enteral feeding were included. Study duration ranged from 3 to 35 d. Nine papers investigated the incidence of diarrhoea where intervention group was given FS and control was given non-fibre-supplemented (NFS) enteral feeds. Those receiving FS feeds were significantly less likely to experience diarrhoea as compared with those using NFS feeds (OR 0·44; 95 % CI 0·20, 0·95; P = 0·04; I2 = 71 %). Combined analysis showed no differences in stool frequency in those receiving NFS feeds (SMD 0·32; 95 % CI −0·53, 1·16; P = 0·47; I2 = 90 %). Results should be interpreted with caution due to considerable heterogeneity between study population, assessment tool for diarrhoea, potential conflict of interest and short duration of studies. This meta-analysis shows that FS feeds can reduce the incidence of diarrhoea in non-critically ill adults; however, the effects of stool frequency remain debatable.

Food-based dietary guidelines have been the basis of public health recommendations for over half a century, but more recently, there has been a trend to classify the health properties of food not by its nutrient composition, but by the degree to which it has been processed. This concept has been supported by many association studies, narrative reviews and the findings from one randomised controlled feeding trial, which demonstrated the sustained effect of ultra-processed diets on increasing both energy intake and body weight. This has led to widespread speculation as to specific features of ultra-processed foods that promote increased energy intakes. Rising interest in the ultra-processed topic has led to proposals to include guidance and restrictions on the consumption of processed foods in national dietary guidelines, with some countries encouraging consumers to avoid highly processed foods completely, and only choose minimally processed foods. However, there remains a lack of consensus on the role of processed foods in human health when faced with the challenges of securing the food supply for a growing global population, that is, healthy, affordable and sustainable. There has also been criticism of the subjective nature of definitions used to differentiate foods by their degree of processing, and there is currently a lack of empirical data to support a clear mechanism by which highly processed foods promote greater energy intakes. Recommendations to avoid all highly processed foods are potentially harmful if they remove affordable sources of nutrients and will be impractical for most when an estimated two-thirds of current energy purchased are from processed or ultra-processed foods. The current review highlights some considerations when interpreting the dietary association studies that link processed food intake to health and offers a critique on some of the mechanisms proposed to explain the link between ultra-processed food and poor health. Recent research suggests a combination of higher energy density and faster meal eating rates are likely to influence meal size and energy intakes from processed foods and offers new perspectives on how to manage this in the future. In going beyond the ultra-processed debate, the aim is to summarise some important considerations when interpreting existing data and identify the important gaps for future research on the role of processed food in health.

Age-related frailty and cognitive decline are complex multidimensional conditions that significantly impact the ability of older adults to sustain functional capacity and independence. While underlying causes remain poorly understood, nutrition continually emerges as one associated risk element. Many studies have addressed the importance of adequate nutrition in delaying the onset of these conditions, but the specific role of micronutrients is not well established. The consideration of pre-frailty as an outcome variable is also limited in the current literature. In this review, we focus on the potential value of maintaining micronutrient sufficiency to sustaining the health of the ageing population. Using data from the Irish longitudinal study on ageing, we consider several vitamins known to have a high prevalence of low status in older adults and their impact on pre-frailty, frailty and cognitive impairment. They include vitamin B12 and folate, both of which are associated with multiple biological mechanisms involved in long-term health, in particular in cognitive function; vitamin D, which has been associated with increased risk of musculoskeletal disorders, depression and other chronic diseases; and the carotenoids, lutein and zeaxanthin, that may help mitigate the risk of frailty and cognitive decline via their antioxidant and anti-inflammatory properties. We show that low concentrations of folate and carotenoids are implicated in poorer cognitive health and that the co-occurrence of multiple nutrient deficiencies confers greatest risk for frailty and pre-frailty in the Irish longitudinal study on ageing cohort. These health associations contribute to evidence needed to optimise micronutrient status for health in the older adult population.

Plums are abundant in bioactive compounds which have been associated with numerous health benefits. In the present study, we aimed at examining the impact of plum supplementation on lipid profile of individuals. Electronic bibliographical databases were searched for relevant randomised clinical trials. Articles meeting our eligibility criteria were included for data extraction and final analysis. Weighted mean difference (WMD) was estimated using a random-effect model. Of the total articles retrieved in the initial search, nine articles were found to be eligible to be included in the analysis. Our results show that plum supplementation significantly improves total cholesterols levels in the unhealthy individuals. Moreover, plum supplementation reduces the LDL-c levels in the pooled sample (WMD = −11⋅52 mg/dl; 95 % CI −21⋅93, −1⋅11, P = 0⋅03, I2 = 98⋅7 %) and also in some of the subgroups of individuals (dried plum, unhealthy subjects, duration more than 8 weeks). Moreover, it had a significant reducing effect on TC levels just in unhealthy subjects. Although plum supplementation did not have any significant impact on serum levels of TG nor HDL-c. Our results show that supplementation with plums is potentially effective in reducing serum total cholesterol and LDL-c.

We performed a systematic review and dose–response meta-analysis of randomised trials on the effects of olive oil consumption on blood lipids in adults. A systematic search was performed in PubMed, Scopus and Web of Science databases until May 2021. Randomised controlled trials (RCT) evaluating the effect of olive oil intake on serum total cholesterol (TC), TAG, LDL-cholesterol and HDL-cholesterol in adults were included. The mean difference (MD) and 95 % CI were calculated for each 10 g/d increment in olive oil intake using a random-effects model. A total of thirty-four RCT with 1730 participants were included. Each 10 g/d increase in olive oil consumption had minimal effects on blood lipids including TC (MD: 0·79 mg/dl; 95 % CI (−0·08, 1·66); I2 = 57 %; n 31, GRADE = low certainty), LDL-cholesterol (MD: 0·04 mg/dl, 95 % CI (−1·01, 0·94); I2 = 80 %; n 31, GRADE = very low certainty), HDL-cholesterol (MD: 0·22 mg/dl; 95 % CI (−0·01, 0·45); I2 = 38 %; n 33, GRADE = low certainty) and TAG (MD: 0·39 mg/dl; 95 % CI (−0·33, 1·11); I2 = 7 %; n 32, GRADE = low certainty). Levels of TC increased slightly with the increase in olive oil consumption up to 30 g/d (MD30 g/d: 2·76 mg/dl, 95 % CI (0·01, 5·51)) and then appeared to plateau with a slight downward curve. A trivial non-linear dose-dependent increment was seen for HDL-cholesterol, with the greatest increment at 20 g/d (MD20 g/d: 1·03 mg/dl, 95 % CI (−1·23, 3·29)). Based on existing evidence, olive oil consumption had trivial effects on levels of serum lipids in adults. More large-scale randomized trials are needed to present more reliable results.

Controversy exists regarding the efficacy of lithium for suicide prevention. Except for a recent trial that enrolled over 500 patients, available trials of lithium for suicide prevention have involved small samples. It is challenging to measure suicide in a single randomised controlled trial (RCT). Adding a single large study to existing meta-analyses may provide insights into lithium's anti-suicidal effects. We performed a meta-analysis of RCTs comparing lithium with a control condition for suicide prevention. MEDLINE and other databases were searched up to 30 November 2021. Efficacy was assessed by calculating the summary Peto odds ratio (OR) and incidence rate ratio (IRR) with 95% confidence intervals. Among seven RCTs, the odds of suicide were lower among patients receiving lithium versus control (OR = 0.30, 95% CI 0.09–1.02; IRR = 0.22, 95% CI 0.05–1.05), although the findings were still not statistically significant. The role of lithium in suicide prevention remains uncertain.

When compared with the general population, people living with severe mental illness (SMI) are 1·8 times more likely to have obesity while in adult mental health secure units, rates of obesity are 20 % higher than the general population. In England, there are currently 490 000 people living with SMI. The aim of this systematic review was to collate and synthesise the available quantitative and qualitative evidence on a broad range of weight management interventions for adults living with SMI and overweight or obesity. Primary outcomes were reductions in BMI and body weight. Following sifting, eighteen papers were included in the final review, which detailed the results of nineteen different interventions; however, there was a lack of qualitative evidence. Pooled results for three studies (MD − 3·49, 95 % CI − 6·85, −0·13, P = 0·04) indicated a small effect in terms of body weight reduction but no effect on BMI for four studies (MD − 0·42, 95 % CI − 1·27, 0·44, P = 0·34). Key recommendations for future research included integration of qualitative methodology into experimental study design, a review of outcome measures and for study authors to follow standardised guidelines for reporting to facilitate complete and transparent reporting.

Recent meta-analytic work indicated that guar gum supplementation might improve lipid profile markers in different populations. However, critical methodological limitations such as the use of some unreliable data and the lack of inclusion of several relevant studies, and the scarcity in assessments of regression and dose-specific effects make it difficult to draw meaningful conclusions from the meta-analysis. Therefore, current evidence regarding the effects of guar gum supplementation on lipid profile remains unclear. The present systematic review, meta-regression and dose–response meta-analysis aimed to examine the effects of guar gum supplementation on lipid profile (total cholesterol (TC), LDL, TAG and HDL) in adults. Relevant studies were obtained by searching the PubMed, SCOPUS, Embase and Web of Science databases (from inception to September 2021). Weighted mean differences (WMD) and 95 % CI were estimated via a random-effects model. Heterogeneity, sensitivity analysis and publication bias were reported using standard methods. Pooled analysis of nineteen randomised controlled trials (RCT) revealed that guar gum supplementation led to significant reductions in TC (WMD: −19·34 mg/dl, 95 % CI −26·18, −12·49, P < 0·001) and LDL (WMD: −16·19 mg/dl, 95 % CI −25·54, −6·83, P = 0·001). However, there was no effect on TAG and HDL among adults in comparison with control group. Our outcomes suggest that guar gum supplementation lowers TC and LDL in adults. Future large RCT on various populations are needed to show further beneficial effects of guar gum supplementation on lipid profile and establish guidelines for clinical practice.

Iodine, through the thyroid hormones, is required for the development of the auditory cortex and cochlea (the sensory organ for hearing). Deafness is a well-documented feature of endemic cretinism resulting from severe iodine deficiency. However, the range of effects of suboptimal iodine intake during auditory development on the hearing ability of children is less clear. We therefore aimed to systematically review the evidence for the association between iodine exposure (i.e. intake/status/supplementation) during development (i.e. pregnancy and/or childhood) and hearing outcomes in children. We searched PubMed and Embase and identified 330 studies, of which thirteen were included in this review. Only three of the thirteen studies were of low risk of bias or of good quality, this therefore limited our ability to draw firm conclusions. Nine of the studies (69 %) were in children (one RCT, two non-RCT interventions and six cross-sectional studies) and four (31 %) were in pregnant women (one RCT, one cohort study and two case reports). The RCT of iodine supplementation in mildly iodine-deficient pregnant women found no effect on offspring hearing thresholds. However, hearing was a secondary outcome of the trial and not all women were from an iodine-deficient area. Iodine supplementation of severely iodine-deficient children (in both non-RCT interventions) resulted in improved hearing thresholds. Five of six cross-sectional studies (83 %) found that higher iodine status in children was associated with better hearing. The current evidence base for the association between iodine status and hearing outcomes is limited and further good-quality research on this topic is needed.

In May 2021, the Scientific Advisory Committee on Nutrition (SACN) published a risk assessment on lower carbohydrate diets for adults with type 2 diabetes (T2D)(1). The purpose of the report was to review the evidence on ‘low’-carbohydrate diets compared with the current UK government advice on carbohydrate intake for adults with T2D. However, since there is no agreed and widely utilised definition of a ‘low’-carbohydrate diet, comparisons in the report were between lower and higher carbohydrate diets. SACN’s remit is to assess the risks and benefits of nutrients, dietary patterns, food or food components for health by evaluating scientific evidence and to make dietary recommendations for the UK based on its assessment(2). SACN has a public health focus and only considers evidence in healthy populations unless specifically requested to do otherwise. Since the Committee does not usually make recommendations relating to clinical conditions, a joint working group (WG) was established in 2017 to consider this issue. The WG comprised members of SACN and members nominated by Diabetes UK, the British Dietetic Association, Royal College of Physicians and Royal College of General Practitioners. Representatives from NHS England and NHS Health Improvement, the National Institute for Health and Care Excellence and devolved health departments were also invited to observe the WG. The WG was jointly chaired by SACN and Diabetes UK.

Previous studies evaluating the effects of betaine supplementation on body composition offer contradictory findings. This systematic review and meta-analysis assessed the effects of betaine supplementation on body composition indices (body mass (BM), BMI, body fat percentage (BFP), fat mass (FM), fat-free mass (FFM)), and dietary intakes. Studies examining the effects of betaine supplementation on body composition and dietary intakes published up to August 2021 were identified through PubMed, the Cochrane Library, Web of Science, Embase, SCOPUS and Ovid databases. Betaine supplementation failed to significantly affect BM ((weighted mean difference (WMD): −0·40 kg, 95 % CI −1·46, 0·64), P = 0·447), BMI ((WMD: −0·05 kg/m2, 95 % CI −0·36, 0·25), P = 0·719), BFP ((WMD: 0·26 %, 95 % CI −0·82, 1·36), P = 0·663), FM ((WMD: −0·57 kg, 95 % CI −2·14, 0·99), P = 0·473) and FFM ((WMD: 0·61 kg, 95 % CI −1·27, 2·49), P = 0·527). Subgroup analyses based on participant’s age (< 40 and > 40 years), sex, BMI, trial duration (< 8 and ≥ 8 weeks), betaine supplementation dosage (< 4 and ≥ 4 g) and health status (healthy or unhealthy) demonstrated similar results. Other than a potential negligible increase in protein intake (WMD: 3·56 g, 95 % CI 0·24, 6·88, P = 0·035), no changes in dietary intakes were observed following betaine supplementation compared with control. The present systematic review and meta-analysis does not show any beneficial effects of betaine supplementation on body composition indices (BM, BMI, FM and FFM).

Adhering to a Mediterranean diet (MD) is associated with reduced CVD risk. This study aimed to explore methods of increasing MD adoption in a non-Mediterranean population at high risk of CVD, including assessing the feasibility of a developed peer support intervention. The Trial to Encourage Adoption and Maintenance of a MEditerranean Diet was a 12-month pilot parallel group RCT involving individuals aged ≥ 40 year, with low MD adherence, who were overweight, and had an estimated CVD risk ≥ 20 % over ten years. It explored three interventions, a peer support group, a dietician-led support group and a minimal support group to encourage dietary behaviour change and monitored variability in Mediterranean Diet Score (MDS) over time and between the intervention groups, alongside measurement of markers of nutritional status and cardiovascular risk. 118 individuals were assessed for eligibility, and 75 (64 %) were eligible. After 12 months, there was a retention rate of 69 % (peer support group 59 %; DSG 88 %; MSG 63 %). For all participants, increases in MDS were observed over 12 months (P < 0·001), both in original MDS data and when imputed data were used. Improvements in BMI, HbA1c levels, systolic and diastolic blood pressure in the population as a whole. This pilot study has demonstrated that a non-Mediterranean adult population at high CVD risk can make dietary behaviour change over a 12-month period towards an MD. The study also highlights the feasibility of a peer support intervention to encourage MD behaviour change amongst this population group and will inform a definitive trial.

Alzheimer’s disease (AD) is the most common major neurocognitive disorder of ageing. Although largely ignored until about a decade ago, accumulating evidence suggests that deteriorating brain energy metabolism plays a key role in the development and/or progression of AD-associated cognitive decline. Brain glucose hypometabolism is a well-established biomarker in AD but was mostly assumed to be a consequence of neuronal dysfunction and death. However, its presence in cognitively asymptomatic populations at higher risk of AD strongly suggests that it is actually a pre-symptomatic component in the development of AD. The question then arises as to whether progressive AD-related cognitive decline could be prevented or slowed down by correcting or bypassing this progressive ‘brain energy gap’. In this review, we provide an overview of research on brain glucose and ketone metabolism in AD and its prodromal condition – mild cognitive impairment (MCI) – to provide a clearer basis for proposing keto-therapeutics as a strategy for brain energy rescue in AD. We also discuss studies using ketogenic interventions and their impact on plasma ketone levels, brain energetics and cognitive performance in MCI and AD. Given that exercise has several overlapping metabolic effects with ketones, we propose that in combination these two approaches might be synergistic for brain health during ageing. As cause-and-effect relationships between the different hallmarks of AD are emerging, further research efforts should focus on optimising the efficacy, acceptability and accessibility of keto-therapeutics in AD and populations at risk of AD.

Dietary habits play an important role in the development of obesity and type 2 diabetes. However, evidence on association between diet frequency and type 2 diabetes was limited and inconclusive. We aimed to examine the association between meal frequency and risk of type 2 diabetes. The cohort study used data from China Health and Retirement Longitudinal Study of 8874 community-dwelling people aged over 45 years. Participants were classified as eating two meals per day, three meals per day and four meals per day. Multiple Poisson regression models were used to examine risk of 4-year incident type 2 diabetes among people who ate more or less than three meals per day compared with people who ate three meals per day. We documented 706 type 2 diabetes cases during follow-up. After adjustment for known risk factors for type 2 diabetes, except for BMI, participants who ate four meals per day were at a lower risk of type 2 diabetes than those who ate three meals per day (relative risk(RR) = 0·73 (0·58, 0·92)). After further adjustment for baseline BMI, the association was slightly attenuated but remained statistically significant (RR = 0·76 (0·60, 0·97)). Subgroup analysis showed that the fully adjusted RR of type 2 diabetes for people eating four meals per day were 0·66 (0·48, 0·91) and 0·93 (0·65, 1·34) among those had a BMI < 25 and ≥ 25 kg/m2, respectively. Eating four meals per day, compared with eating three meals per day was associated with lower risk of developing type 2 diabetes in a Chinese population, particularly in those with a BMI < 25 kg/m2.

School-based studies, despite the large number of studies conducted, have reported inconclusive results on obesity prevention. The sample size is a major constraint in such studies by requiring large samples. This pooled analysis overcomes this problem by analysing 5926 students (mean age 11·5 years) from five randomised school-based interventions. These studies focused on encouraging students to change their drinking and eating habits, and physical activities over the one school year, with monthly 1-h sessions in the classroom; culinary class aimed at developing cooking skills to increase healthy eating and attempts to family engagement. Pooled intention-to-treat analysis using linear mixed models accounted for school clusters. Control and intervention groups were balanced at baseline. The overall result was a non-significant change in BMI after one school year of positive changes in behaviours associated with obesity. Estimated mean BMI changed from 19·02 to 19·22 kg/m2 in the control group and from 19·08 to 19·32 kg/m2 in the intervention group (P value of change over time = 0·09). Subgroup analyses among those overweight or with obesity at baseline also did not show differences between intervention and control groups. The percentage of fat measured by bioimpedance indicated a small reduction in the control compared with intervention (P = 0·05). This large pooled analysis showed no effect on obesity measures, although promising results were observed about modifying behaviours associated with obesity.

The association between fish consumption and decreased risk of CVD is well documented. However, studies on health effects of fish consumption suggest that other components than n-3 PUFA have beneficial cardiometabolic effects, including effects on glucose metabolism. The aim of the present study was to investigate effects of salmon fish protein on cardiometabolic risk markers in a double-blind, randomised controlled parallel trial. We hypothesised that daily intake of a salmon fish protein supplement for 8 weeks would improve glucose tolerance in persons with increased risk of type 2 diabetes mellitus (T2DM). Our primary outcome measure was serum glucose (s-glucose) 2 h after a standardised oral glucose tolerance test. In total, eighty-eight adults with elevated s-glucose levels were randomised to 7·5 g of salmon fish protein/d or placebo, and seventy-four participants were included in the analysis. We found no significant effect of salmon fish protein supplementation on our primary outcome or other markers related to glucose tolerance, serum lipids, weight or blood pressure compared with placebo. The present study does not support the hypothesis that daily intake of a salmon fish protein supplement for 8 weeks improves glucose tolerance in persons with increased risk of T2DM.