The ketogenic diet is becoming a popular nutritional model among athletes. However, the relationship between its use and metabolism during exercise seems to have not been fully investigated. The aim of the study was to assess the effects of a four-week ketogenic diet (KD) on fat and carbohydrate (CHO) utilization during an incremental cycling test (ICT) in CrossFit-trained female (n = 11) and male (n = 11) athletes. During the ICT (while consuming the customary diet and after the KD), oxygen uptake and carbon dioxide exhalation were registered, and CHO and fat utilization as well as energy expenditure were calculated. In males, the KD led to an increase in fat utilization (g·min− 1·kgFFM− 1 and % oxidation). It was particularly noticeable at exercise intensities up to 80% of VO2max. An increase in the area under the curve (AUC) was seen in males but not in females at up to ≤65% VO2max of fat utilization. Male CrossFit-trained athletes seem to be more prone to shifts in macronutrient utilization (in favor of fat utilization) during submaximal intensity exercise under a ketogenic diet than are female athletes. Clinical Trials Gov, NCT03665948 . Registered 11 September 2018 (retrospectively registered).

The increasing consumption of chia seeds is followed by a growing interest in their nutritional and toxicological characterization. To assess the characterization of the essential and PTEs of this novel food, 20 samples of conventional and organic chia seeds available on the European market were analyzed using ICP-OES. Then, the dietary exposure to these elements was assessed. An exhaustive investigation into the metal content of this food serves to elucidate the paucity of existing knowledge. The results show that the levels of essential elements are similar in both types of production, while the levels of PTEs are higher in the organic samples. The exposure assessment indicates that Mn contributes the most among the essential elements, followed by Cu in women. Exposure to PTEs through doses of 50 g/day of chia seeds analyzed would hardly pose short-term health risks as the contributions are below 10%, except for Sr, although they could produce a long-term toxicological risk. To promote safety in chia seed consumption, it is recommended to encourage responsible and moderate consumption, continue monitoring PTE levels in this novel food, and establish concentration limits for PTEs in future European regulations.

Background: The ketogenic diet (KD) is becoming a popular nutritional model for athletes. One limitation of this diet is the use of animal-meat products, which may be unacceptable to some people. Moreover, the relationship between this diet’s use, body composition, and strength capacity has not been thoroughly investigated. This study aimed to assess the effects of a two-week fish-based restrictive KD on body composition, strength capacity (isometric muscle strength), and somatic disorders in healthy adults. Methods: Participants were recruited through advertisements, posters displayed at the university, and information shared among colleagues. Ultimately, 14 individuals qualified for this study. For two weeks, they followed a designated ketogenic diet enriched with fish and omega-3 fatty acids, with a calorie reduction of −500 kcal/day. The study was designed and conducted as a single-group pre–post study. Before and after completing the diet, participants’ body composition (body mass, body fat, fat-free mass, and visceral fat) and strength capacity (knee extensor peak torque [KEPT] and knee flexor peak torque [KFPT]) were measured. The survey also analyzed participants’ somatic disorders such as nausea, vomiting, energy level, diarrhea, constipation, drowsiness, sleep problems, hunger, thirst, and bad breath. The average results of both trials obtained before and after the diet were compared using the paired Student’s t-test or non-parametric test. The significance level was set at 0.05. Results: After two weeks of a fish-based restrictive KD, significant increases in ketone bodies were observed in both the blood (pre: 0.21 mmol/L ± 0.15 vs. post: 2.20 ± 1.19, p < 0.001) and urine (pre: 0.00 mmol/L ± 0.00 vs. post: 4.64 mmol/L ± 3.24, p < 0.001). Body composition changes included significant reductions in total body mass (pre: 76.66 kg ± 11.06 vs. post: 73.77 kg ± 10.76, p < 0.001), fat mass (pre: 21.34 kg ± 7.36 vs. post: 19.73 kg ± 7.20, p < 0.001), and visceral fat (pre: 708.50 g ± 627.67 vs. post: 603.21 g ± 567.82, p = 0.0012). Skeletal muscle mass decreased by 2% (pre: 27.75 kg ± 5.80 vs. post: 27.03 kg ± 5.47, p = 0.01), though no significant changes were seen in muscle strength when adjusting for body mass or skeletal muscle mass. No major adverse effects were noted in relation to somatic disorders, although some participants reported increased thirst and bad breath. Conclusions: After 14 days of a fish-based restrictive KD, a significant reduction in body mass and changes in body composition were observed, with no loss of muscle strength. This type of diet may serve as an effective method for rapid body mass reduction in sports with weight categories, while preserving muscle strength, which is crucial for athletes. It could also be an alternative means for individuals to eliminate animal meat from their diet.

Flax (Linum usitatissimum L.) is valued for its fibers and nutrient-rich seeds, which are increasingly consumed for their health benefits. However, flaxseeds can also accumulate potentially toxic elements (PTEs), raising concerns about safety. This study quantified 11 essential elements (e.g., Ca, Fe, Mg, and Zn) and 9 PTEs (e.g., Al, Cd, Pb, and Ni) in commercial flaxseed samples using inductively coupled plasma–optical emission spectrometry. Two intake scenarios (15 g/day and 30 g/day) were analyzed to estimate dietary exposure, with health risks assessed through the target hazard quotient (THQ) and hazard index (HI). The results showed that organic flaxseeds had higher levels of certain elements (e.g., Cu, K, and Pb), while Al and Ni were more abundant in conventional samples. Cadmium levels in both remained below the EU regulatory limit. The highest estimated daily intakes were for K, Mg, and Ca, highlighting the seeds’ nutritional value. However, HI values suggested that Al and Pb could pose health risks. These findings emphasize flaxseeds’ dual nature as both beneficial and potentially harmful, particularly given the lack of specific regulatory limits and limited data on elemental composition. Continued monitoring and risk assessment are recommended to safeguard public health.

Background: A ketogenic diet (KD) is increasingly investigated as a nutritional approach for improving glycemic control and metabolic health. However, relatively few studies have examined fish‐rich ketogenic interventions. Fish consumption may substantially increase circulating trimethylamine N‐oxide (TMAO), while habitual fish intake is generally associated with favourable cardiometabolic outcomes. The metabolic significance of a short‐term diet‐induced increase in TMAO therefore remains unclear. This study aimed to characterize changes in circulating TMAO and related metabolites, glycemic and insulin‐related biomarkers, oxidative stress markers, and lipid profiles during a fish‐rich, calorie‐restricted KD in healthy adults. Methods: Nine men and five women (mean age 45 ± 3 years) participated in a 2‐week, single‐arm, within‐subject pre–post dietary intervention. TMAO and related metabolites, selected glycemic and insulin‐related biomarkers, oxidative stress markers, and lipid‐profile parameters were assessed before and after the intervention. Participants followed individualized fish‐rich ketogenic meal plans providing an approximately 500 kcal/day energy deficit. Results: Following the intervention, circulating TMAO and betaine concentrations increased significantly, whereas carnitine and glycerophosphocholine (GPC) concentrations decreased. Favourable changes were observed in fasting glucose, insulin, C‐peptide, leptin, and resistin. HDL cholesterol decreased significantly, while total cholesterol, LDL cholesterol, and triglycerides remained unchanged. No evidence of increased oxidative stress was observed. The direct estimate of insulin sensitivity (HOMA‐%S) did not reach statistical significance after correction for multiple comparisons. Conclusions: A 2‐week, calorie‐restricted, fish‐rich ketogenic intervention was associated with a marked increase in circulating TMAO together with favourable changes in selected glycemic, insulin‐related, and adipokine biomarkers, without evidence of increased oxidative stress. HDL cholesterol decreased, whereas other lipid‐profile parameters remained largely unchanged. Because caloric restriction, ketogenic macronutrient composition, high fish intake, and reductions in body weight and adiposity occurred simultaneously, the independent contribution of TMAO to these metabolic changes cannot be determined. These findings should therefore be considered preliminary and hypothesis‐generating.