Tryptophan is an essential amino acid required for protein synthesis, immune regulation and the production of serotonin, melatonin and kynurenine. Its metabolism proceeds through three major pathways – the kynurenine, serotonin and gut microbiota–derived indole pathways – which are influenced by diet, microbiota and inflammation. The Mediterranean diet generally improves tryptophan bioavailability, enhances serotonin synthesis and limits excessive kynurenine activation through anti-inflammatory and microbiota-mediated mechanisms. In contrast, Western diets promote systemic inflammation, increase kynurenine production and reduce serotonin and beneficial indole metabolites. High-protein and ketogenic diets elevate substrate availability but may increase microbial production of indoles such as skatole and alter the balance of tryptophan utilisation, while calorie-restricted diets appear to downregulate pro-inflammatory tryptophan degradation and improve serotonin-related satiety regulation. Collectively, these findings demonstrate that diet is a key regulator of tryptophan metabolism, with implications for mood, sleep, inflammation, cancer progression and cardiometabolic health. Despite these advances, several knowledge gaps remain, including limited standardisation of dietary assessment methods, insufficient databases on the tryptophan content of foods and a lack of controlled comparative trials. Addressing these limitations may enable the development of nutritional strategies that optimise tryptophan metabolism and improve health outcomes.

Individuals with type 2 diabetes are at increased risk for developing CVD. We assessed how dietary counselling on a high-quality, fibre-rich diet influenced cardiometabolic health of patients with type 2 diabetes. In this 6-month trial, 121 patients with type 2 diabetes (67 (sd 8·7) years, 68 % men, BMI 27·8 kg/m2) were assigned to dietary counselling (n 61) or standard care (n 60). Counselling included 4–7 individual sessions with a dietitian, aimed at increasing fibre intake to improve diet quality. The primary outcome was a composite risk score estimating 10-year CVD risk. Secondary outcomes included diet quality, assessed by the Dutch Healthy Eating Index-2015 (DHD15-index), HbA1c, LDL-cholesterol, blood pressure, body weight and medication use. Diet quality score at baseline was 115 (sd 26) and similar across groups. Over 6 months, DHD15-index scores improved by 4·5 points (95 % CI: −0·2, 9·1) in the intervention group v. control, but not significant. The change in 10-year CVD risk across the 6 months of the trial (primary outcome) did not differ between groups −0·1 %, 95 % CI: −0·2, 0·1. Changes over time in HbA1c (–1·1 mmol/mol, 95 % CI: −4·4, 2·3), LDL-cholesterol (0·0 mmol/l, 95 % CI: −0·2, 0·3), blood pressure (–1 mmHg, 95 % CI: −6, 4), body weight (–0·1 kg, 95 % CI: −1·2, 1·1) or medication use did not differ between groups. Dietary counselling for 6 months slightly improved adherence to a high-quality, fibre-rich diet in patients with type 2 diabetes but did not significantly impact cardiometabolic health or medication use.

Maternal Hb and fetal growth change dynamically throughout pregnancy. We examined the associations of time-specific Hb levels and Hb trajectories with fetal biometrics and adverse birth outcomes. This prospective study included 6844 pregnant women (mean age 26·6 (sd 3·7) years) from the Tongji-Huaxi-Shuangliu Birth Cohort. Hb levels were measured at four periods: early (6–12 gestational weeks), middle (13–27), middle-late (28–32) and late pregnancy (33–37). Fetal biometrics were assessed by ultrasound from middle to late pregnancy. Birth outcomes were obtained from medical records, including small for gestational age (SGA), low birth weight (LBW) and preterm birth. Three Hb trajectories were identified: consistent decline (Trajectory 1), consistently low (Trajectory 2) and increase from middle-late pregnancy (Trajectory 3). Compared with Trajectory 1, Trajectory 3 was associated with lower estimated fetal weight (β, −0·54; 95 % CI −0·99, −0·09) and abdominal circumference (β, −0·21; 95 % CI −0·40, −0·01) in late pregnancy and higher umbilical artery resistance index across pregnancy (β, 0·65; 95 % CI 0·31, 1·00). Trajectory 3 was also associated with higher risk of LBW (OR, 1·57; 95 % CI 1·09, 2·26). In middle-late pregnancy, higher Hb (≥ 130 g/l) was associated with higher risks of LBW (OR, 2·26; 95 % CI 1·08, 4·25) and preterm birth (OR, 2·03; 95 % CI 1·12, 3·44) compared with the reference (110–129 g/l). Elevated maternal Hb from middle-late pregnancy onwards may be associated with lower fetal weight and increased risk of LBW. Dynamic monitoring of maternal Hb may facilitate targeted nutritional management in pregnant women.

Elevated LDL-cholesterol concentration is a major risk factor for CVD. Regular consumption of marine fish and seafood is associated with a reduced risk of CVD, although the n-3 PUFAs EPA and DHA have no cholesterol-lowering effect when given in physiologically relevant doses. Recent studies have demonstrated a lower LDL-cholesterol concentration in rodents after intake of cetoleic acid (CA, C22:1n-11), found in pelagic fish species such as herring. The primary aim was to investigate the effect of consuming capsules containing CA on LDL-cholesterol concentration in adults with overweight or obesity. The study was designed as a randomised clinical trial with two arms. Eighty participants were enrolled, and data from 75 participants were included in the statistical analyses. Participants consumed capsules containing either a CA concentrate (CECO group; 1480 mg CA and 232 mg EPA per day) or soyabean oil mixed with an n-3 PUFA concentrate without CA as comparator arm (SOYO3 group; 258 mg EPA/d) for 8 weeks. The within-group changes in LDL-cholesterol were compared using ANCOVA with changes in body fat percentage as covariate. The LDL-cholesterol concentration was decreased from baseline to 8 weeks in the CECO group (n 37, median −0·1 (quartiles −0·1, 0·0) mmol/l) in comparison to the SOYO3 group (n 38, median 0·2 (quartiles 0·1, 0·2) mmol/l), with F = 19·35, P = 0·033 and ηp2 = 0·212, corresponding to a 7 % reduction in the CECO group relative to the SOYO3 group. To conclude, 8 weeks of dietary supplementation with CECO decreased the LDL-cholesterol concentration in adults with overweight or obesity.

Metabolic disorders have a detrimental effect on individuals’ health status, regardless of their weight. We aimed to assess the link between diet-related behaviours and metabolic health status as well as serum levels of adropin and brain-derived neurotrophic factor (BDNF). A cross-sectional investigation involving 527 adults was conducted in Isfahan, Iran. Dietary habits were assessed in five domains including meal pattern, eating rate, meal-to-sleep interval, intra-meal fluid intake and fatty food intake. Based on the lipid and glycaemic profile, inflammation status and insulin resistance, participants were classified as having either metabolically healthy or metabolically unhealthy (MU) status. Serum concentrations of BDNF and adropin were also evaluated. Metabolic unhealthy normal-weight and overweight/obese status were prevalent in 8·7 % and 33·8 % of study population, respectively. We recognised three eating rate classes, two meal pattern classes, two meal-to-sleep interval classes, two intra-meal fluid intake classes, and two fatty food intake classes. Slow eating rate was related to lower odds of MU profile (OR = 0·39, 95 % CI: 0·17, 0·91). Moreover, fast eating rate was positively associated with hyperglycaemia (OR = 3·55, 95 % CI: 1·48, 8·51). More intra-meal fluid intake was also associated with higher chance of MU profile (OR = 2·21, 95 % CI: 1·35, 3·63), high homeostasis model assessment of insulin resistance (OR = 2·20, 95 % CI: 1·06, 4·58), hypertriglyceridaemia (OR = 2·23, 95 % CI: 1·36, 3·65) and hypertension (OR = 1·66, 95 % CI: 1·03, 2·69). Serum BDNF or adropin was not associated with classes of diet-related habits. More intra-meal fluid intake was linked to higher chance of having MU profile, while slow eating rate was related to decreased odds of MU profile among Iranian adults.

Little is known about the factors that influence inter-individual variability in the thermic effect of food (TEF). Factors such as age, physical activities, insulin resistance and body weight and composition have been proposed as potential predictors, but findings remain inconsistent. TEF may also be influenced by hormonal status in females. Therefore, this study aimed to explore potential physiological and dietary predictors of TEF in a well-phenotyped cohort of females approaching menopause. This study is a secondary analysis of the MONET study. Eighty-six females had complete data for all predictors included in the analyses: fat mass (kg), resting energy expenditure (REE), VO2peak, fasting glucose, follicle-stimulating hormone and habitual protein intake. Stepwise multiple linear regression analyses were conducted to identify predictors of TEF. Mean TEF over the 180-min measurement period was 33 (sd 8·7) kcal. Habitual daily protein intake was the only consistent significant predictor of TEF across regression models (B ≈ 0·12–0·14 kcal·g−1, β ≈ 0·23–0·24, P ≤ 0·04), explaining 6 % of the variance (R2 = 0·060). Inclusion of fat mass, REE, VO2peak, fasting glucose or follicle-stimulating hormone did not meaningfully improve model fit. These findings suggest that TEF may represent a relatively stable physiological trait, with modest contributions from habitual dietary protein intake, and that additional, unmeasured factors may contribute to inter-individual variability.

In 250 men (21·4 (sd 2·9) years; BMI 24·2 (sd 3·0) kg·m–2) commencing arduous military training during winter, we investigated the effect of 12 weeks of vitamin D supplementation on lower body (pelvic girdle, sacrum, coccyx and lower limb) overuse musculoskeletal injury risk in a randomised, placebo-controlled trial. Participants received either simulated sunlight (1·3 × standard erythemal dose in T-shirt and shorts, three times per week for 4 weeks and then once per week for 8 weeks), oral vitamin D3 (1000 IU · d–1 for 4 weeks and then 400 IU · d–1 for 8 weeks) or placebo for each intervention. Serum vitamin D metabolites and bone metabolism biomarkers were measured at baseline, week 5 and week 12. At baseline, 29 % of participants were vitamin D sufficient (25-hydroxyvitamin D ≥ 50 nmol·L–1). Vitamin D supplementation achieved vitamin D sufficiency in 95 % of participants after 4 weeks. During 6 months of training and subsequent 3 years of military service, 100 lower body overuse musculoskeletal injuries were diagnosed by clinicians. Frailty models indicated no difference in injury risk between vitamin D and placebo during military training (HRplacebo:vitamin D = 1·23 (95 % CI 0·57, 2·66), P = 0·597) or military service (HRplacebo:vitamin D = 0·94 (95 % CI 0·60, 1·46), P = 0·782). Both safe simulated sunlight and oral vitamin D3 were effective in achieving and maintaining vitamin D sufficiency in almost all. There was no clear evidence that vitamin D affects the risk of lower body overuse musculoskeletal injury during 6 months of military training or subsequent 3 years of military service.

Fe-deficiency anaemia is common during pregnancy and can lead to serious health consequences for mothers and babies. Antenatal Fe supplementation is associated with lower anaemia prevalence and improved pregnancy outcomes, and the WHO recommends daily oral Fe (30–60 mg) with folic acid (0·4 mg) during pregnancy. However, data on uptake and adherence in many low- and middle-income countries remain fragmented and outdated. We conducted a secondary analysis of Demographic and Health Surveys from sixty-nine low- and middle-income countries to assess uptake and adherence to Fe-containing supplements and explore associations with socio-demographic characteristics and antenatal care (ANC). Overall, 86 % of respondents reported receiving Fe supplements during pregnancy. Among these women, 46·1 % consumed ninety or more supplements, 23·3 % consumed 120 or more, and only 7·1 % consumed 180 or more. Higher education, wealth, and media access were strongly associated with increased odds of initiating supplementation (OR: 1·32; 95 % CI: 1·25, 1·38; OR: 1·29; 95 % CI: 1·20, 1·38; OR: 1·15; 95 % CI: 1·05, 1·26, respectively) and adhering to the regimen (OR: 1·16; 95 % CI: 1·12, 1·21; OR: 1·21; 95 % CI: 1·13, 1·30; OR: 1·14; 95 % CI: 1·08, 1·20, respectively). Early ANC attendance was also associated with higher supplement consumption. Country-specific ANC guidelines are needed to provide clear guidance on the timing and frequency of ANC attendance and supplementation.

Iodine is a component of thyroid hormones and essential for neurological development. To evaluate the iodine nutritional status of pregnant women residing in Veneto and the possible role of thyroglobulin (Tg) as a proxy. 528 pregnant women in the third trimester of pregnancy were consecutively enrolled in this cross-sectional study and were asked to provide an early-morning spot urine sample (for UI/Creat) and a blood sample (for thyroid function and Tg). They also completed a questionnaire. Infant anthropometric data at birth were obtained. Median UI/Creat was 112·8 μg/g. 34·1 % of women had a UI/Creat ≥ 150 μg/g. Iodised salt (IS) was used by 76·9 % of women, iodine-containing supplements (ICS) by 74·2 % and cow’s milk was regularly consumed by 46·0 %. At multivariable analysis, consumption of regular cow’s milk and ICS were significant predictors of UI/Creat ≥ 150 μg/g (OR 1·57, 95 % CI: 1·06, 2·32 and OR: 2·83, 95 % CI: 1·66, 4·82, respectively). The median Tg value was lower among the iodine-sufficient than among the iodine-deficient women (P = 0·005). At multiple linear regression analysis, Tg was among the factors associated with weight (β = –81·83, P < 0·001) and length (β = –0·3, P < 0·01) at birth, although weakly. Tg was a factor associated with pre-term delivery (OR: 1·52, 95 % CI: 1·20, 1·92). Regular use of cow’s milk and ICS is a factor associated with UI/Creat ≥ 150 μg/g. Tg was associated with iodine status and pregnancy outcomes, although it had only a modest discriminative ability for sufficiency.

The Mediterranean diet has emerged as a promising dietary pattern for preventing non-alcoholic fatty liver disease (NAFLD). This study aimed to examine the role of the Mediterranean diet on the risk of NAFLD in Turkish adults. A total of 252 individuals (126 NAFLD and 126 age- and sex-matched controls) participated in this case–control study. Dietary intake was assessed with a 24-h recall, and adherence to the Mediterranean diet was evaluated using the Mediterranean Diet Adherence Screener (MEDAS). Logistic regression models were applied to estimate OR. The prevalence of NAFLD was higher in the lowest tertile (64·6 %) and lower in the highest tertile (30·5 %; P < 0·001). Moderate adherence to the Mediterranean diet was associated with a 57·0 % lower risk of NAFLD after adjusting for age, sex, BMI and energy intake. High adherence conferred an 86·0 % reduction after adjusting for age, sex, BMI, energy intake and co-morbidities. Frequent consumption of butter, margarine, cream (OR = 2·75; 95 % CI 1·72, 6·43) and sugar-sweetened beverages (OR = 2·87; 95 % CI 1·20, 6·87) significantly increased the risk. However, consuming nuts three or more servings per week was protective (OR = 0·46; 95 % CI 0·21, 0·99). In individuals who did not consume ≥ 3 servings of fruit daily, the risk of NAFLD was significantly reduced (OR = 0·28; 95 % CI 0·16, 0·69). Adherence to the Mediterranean diet was strongly associated with a reduced risk of NAFLD, highlighting the importance of limiting saturated fats and sugar-sweetened beverages while promoting nuts as practical strategies for prevention.

Vitamin D has been associated with depression, potentially via anti-inflammatory mechanisms, yet data are scarce, particularly in adolescence. We investigated (1) whether lower vitamin D status is associated with greater depression severity and (2) whether this association is statistically moderated by inflammation in patients of a child and adolescent psychiatry department. At admission, fasting morning venous blood was drawn. Serum vitamin D (25-hydroxy-cholecalciferol (25(OH)D)) and C-reactive protein (CRP) were analysed in all participants (n 465 (64·7 %♀; 11·3–18·9 years)). In a subsample (n 177), we additionally measured tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ) and interleukin (IL)-1β, IL-6, IL-8 and IL-10. Depression severity was assessed by the Beck Depression Inventory II (BDI-II) (n 450), the Diagnostic System for Mental Disorders in Childhood and Adolescence via self-assessment (DISYPS Self) (n 441) and parent-assessment (DISYPS Proxy) (n 422). Overall, 43·2 % (n 201) were at risk for vitamin D deficiency (< 30 nmol/l), and 73·5–83·2 % – depending on assessment tool – showed at least mild depression. Linear regression revealed an inverse association between 25(OH)D and BDI-II in both crude and CRP-adjusted full-sample models. Logistic regressions showed a robust inverse association between 25(OH)D and DISYPS Proxy, but not for DISYPS Self. Although 25(OH)D was inversely correlated with some pro-inflammatory markers, neither their inclusion in regression models nor formal mediation analyses supported inflammation as a mediator of the vitamin D–depression association. Overall, our results suggest that vitamin D relates modestly to both depression and inflammation in adolescence. However, based on the measured parameters, we cannot confirm that anti-inflammatory effects are the link between vitamin D and depression.

Concerns about the environmental impact of animal-source foods have led to a shift towards plant-based alternatives (PBA). While dairy products and seafood are rich in iodine, an essential nutrient for thyroid function and cognitive development, PBA often lack iodine fortification. As the market expands, there is increasing concern that individuals replacing dairy products and seafood with unfortified PBA may be at risk of iodine deficiency. This study assessed changes in the iodine fortification of plant-based milk, yogurt, cheese and seafood alternatives through a cross-sectional survey of UK supermarkets (2020–2024). Supermarkets were surveyed online each December, and product nutrition and ingredient data were extracted. Between 2020 and 2024, the number of PBA increased by 55 %, with 466 PBA identified in 2024, including milk (n 246), yogurt (n 81), cheese (n 110) and seafood alternatives (n 29). Iodine fortification was inconsistent: in 2024, 48 % of non-organic milk alternatives were fortified, while only 5 % of non-organic yogurt and 4 % of cheese alternatives contained iodine. In comparison, 28 %, 6 % and 0 % of non-organic milk, yogurt and cheese alternatives were fortified with iodine in 2020. No fortified seafood alternatives were identified. Fortified PBA provided 75–83 % of the iodine content of cow’s milk, but most remained poor iodine sources. Although iodine fortification has increased, it lags behind that of calcium and vitamin B12 (48 % v. 88 % and 71 %, respectively). Given iodine’s critical role in health, clearer public health guidance and improved fortification policies are needed. Increased reliance on PBA may exacerbate iodine insufficiency in the UK without intervention.

This longitudinal, prospective, multicentre observational cohort study investigates the associations between maternal nutritional status – assessed using the first trimester SIMPLE score and pregestational BMI – and fetal growth trajectories and velocity, as proxies for intrauterine development. Healthy women with singleton pregnancies undergoing first trimester screening were enrolled. Adherence to a healthy lifestyle was evaluated using the SIMPLE score, categorising participants into low (< 6) and high (≥ 6) adherence groups. Fetal growth parameters – including biparietal diameter, head circumference, abdominal circumference (AC), femur length and estimated fetal weight (EFW) – were assessed during second and third trimester ultrasounds, and birth outcomes were recorded. Multi-adjusted linear mixed models examined associations between SIMPLE score groups, individual score items, pregestational BMI and fetal growth, with analyses stratified by fetal sex. Out of 938 enrolled women, 109 (11·6 %) were classified as the low-adherence group. Multi-adjusted linear mixed models showed that low adherence was associated with decreased EFW acceleration from the second to the third trimester. Stratification by fetal sex confirmed the association only among male fetuses. Analysis of pregestational BMI and individual SIMPLE score items revealed significant positive associations between pregestational BMI, AC and EFW growth velocity and a negative association between first trimester Hb (> 110 g/l) and EFW growth velocity. Overall, these findings confirm the clinical utility of the SIMPLE score, demonstrating significant associations with intrauterine growth trajectories and velocity, independent of other markers of nutritional status (e.g. pregestational BMI).

Plasma levels of procollagen type 1 N-propeptide (P1NP) and C-terminal telopeptide of type 1 collagen (CTX) are bone turnover markers (BTM) used to predict risk of fracture. We compared the effects of vitamin D supplements on plasma levels of P1NP and CTX in the Biochemical Efficacy and Safety Trial of vitamin D (BEST-D) trial (305 participants) after treatment with 2000 IU/d or 4000 IU/d vitamin D3 or placebo. The results of BEST-D were combined in a meta-analysis of all trials of vitamin D v. placebo on levels of P1NP (12 trials, 2654 participants) or CTX (16 trials, 2695 participants). In BEST-D, allocation to vitamin D3 resulted in a dose-dependent increase in 25-hydroxy-vitamin D (25(OH)D) levels but had no effects on P1NP or CTX. Geometric mean (se) levels at 12 months were similar for P1NP (41·7 (0·7) v. 42·9 (1·0) ng/ml; P = 0·29: either dose v. placebo) and likewise for CTX (0·23 (0·01) v. 0·23 (0·01) ng/ml; P = 0·98). In a meta-analysis of eighteen trials, the average difference between the within-trial change in P1NP for allocated vitamin D and control was −3·3 % (95 % CI −5·6, −1·0, P < 0·005). For CTX, this difference was slightly greater (−3·8 % (−6·8, −0·8); P = 0·01). There was no significant heterogeneity between these trials after stratifying trials with or without Ca, higher or lower doses of vitamin D, or lower v. higher pre-treatment levels of 25(OH)D. Overall, vitamin D supplementation was associated with modest reductions in both P1NP and CTX, and results provide support for further trials of vitamin D for prevention of fracture in older people.