The interaction between nutrition and the immune system is very complex. In particular, at every stage of the immune response, specific micronutrients, including vitamins and minerals play a key role and often synergistic, and the deficiency of only one essential nutrient may impair immunity. An individual’s overall nutrition status and pattern of dietary intake (comprised of nutrients and non-nutritive bioactive compounds and food) and any supplementation with nutraceuticals including vitamins and minerals, can influence positively or negatively the function of the immune system. This influence can occur at various levels from the innate immune system and adaptive immune system to the microbiome. Although there are conflicting evidence, the current results point out that dietary supplementation with some nutrients such as vitamin D and zinc may modulate immune function. An update on the complex relationship between nutrition, diet, and the immune system through gut microbiota is the aim of this current review. Indeed, we will provide the overview of the link among immune function, nutrition and gut microbiota, paying particular attention at the effect of the Mediterranean diet on the immune system, and finally we will speculate the possible role of the main one functional supplements on immune function.

Coronavirus disease 2019 (COVID-19) has quickly become a global pandemic. Reports from different parts of the world indicate that a significant proportion of people who have recovered from COVID-19 are suffering from various health problems collectively referred to as “long COVID-19”. Common symptoms include fatigue, shortness of breath, cough, joint pain, chest pain, muscle aches, headaches, and so on. Vitamin D is an immunomodulatory hormone with proven efficacy against various upper respiratory tract infections. Vitamin D can inhibit hyperinflammatory reactions and accelerate the healing process in the affected areas, especially in lung tissue. Moreover, vitamin D deficiency has been associated with the severity and mortality of COVID-19 cases, with a high prevalence of hypovitaminosis D found in patients with COVID-19 and acute respiratory failure. Thus, there are promising reasons to promote research into the effects of vitamin D supplementation in COVID-19 patients. However, no studies to date have found that vitamin D affects post-COVID-19 symptoms or biomarkers. Based on this scenario, this review aims to provide an up-to-date overview of the potential role of vitamin D in long COVID-19 and of the current literature on this topic.

Polycystic Ovary Syndrome (PCOS) is an endocrine/metabolic disorder with an ever-increasing prevalence. It has various clinical characteristics; the cardinals are androgen excess, oligo-anovulatory infertility, polycystic ovaries, insulin resistance (IR), and cardiometabolic alterations. These disturbances are a consequence of PCOS's complex etiology. PCOS is mainly related to women with obesity; however, there are many PCOS lean patients too. Even though they share some aspects in their metabolic profiles, each group has individual differences in body composition and other parameters. Thus, in order to achieve successful therapeutic strategies, they should be tailored to these details. The authors reviewed PubMed's updated and related publications about body composition and nutritional strategies for PCOS lean and obese patients. As previous reports have determined, dietary patterns are essential in PCOS treatment. Several diets have been studied to control and improve IR, infertility, and cardiometabolic dysfunctions in PCOS. This review will explain the specific features in metabolic characterization and body composition among these patients. Finally, the diverse nutritional strategies used in women with PCOS will be analyzed depending on their lean or obese phenotype.

Psoriasis is an immune-mediated inflammatory skin disease associated with multiple comorbidities. Considered one of the most common inflammatory skin diseases among the general population, it not only affects the skin, but also negatively impacts other organs and joints. In addition, psoriasis has been associated with several chronic cardio-metabolic diseases such as obesity, which would seem to be (i) a risk factor for the onset of psoriasis and (ii) a worsening factor of the severity of the disease. Weight loss appears to improve severity in overweight patients. Recently proposed as an obesity management nutritional strategy, the very-low-calorie ketogenic diet (VLCKD) has demonstrated significant effects in reducing inflammatory processes. In the current review, we describe the evidence available on psoriasis and VLCKD, and provide a practical guide to the prescription of VLCKD in the different phases, evaluation and management of possible adverse events, and the importance of physical activity as a lifestyle modification to reduce psoriasis and associated comorbidities. Randomized control trials are, however, necessary to determine the most effective VLCKD protocol for patients with obesity and psoriasis, optimal protocol duration, composition of micronutrients and macronutrients, choice of special supplements, and management of carbohydrate reintroduction.

Background: Preoperative nutritional interventions, including low-calorie diets (LCDs) and very low-calorie diets (VLCDs), are commonly implemented in metabolic and bariatric surgery. This systematic review and meta-analysis aimed to evaluate the efficacy and safety of preoperative dietary interventions in patients undergoing bariatric surgery, with primary outcomes including perioperative complications, operative time, and length of hospital stay. Methods: A systematic review and meta-analysis were conducted, including studies that compared LCD and VLCD with regular diets in adults undergoing bariatric surgery. The primary outcomes assessed were perioperative complications, operative time, and length of hospital stay. Random- and fixed effects models were used for quantitative synthesis. Risk of bias was evaluated using the Cochrane Risk of Bias tool and ROBINS-I, while the certainty of evidence was assessed using the GRADE approach. Results: Eight trials comprising 1197 patients were included in the meta-analysis. VLCDs were associated with a significant reduction in perioperative complications (OR 0.59; 95% CI: 0.37–0.94; p = 0.03), whereas LCDs showed no significant effect on complications (OR 1.64; 95% CI: 0.71–3.78; p = 0.25). No significant reduction in operative time was observed (MD −2.64 min; 95% CI: −6.01 to 0.73; p = 0.12). Hospital stay was slightly reduced (MD −0.17 days; p = 0.0001), though the clinical significance remains uncertain. The certainty of evidence was low, primarily due to the risk of bias and small sample sizes. Conclusions: VLCDs may lower the risk of perioperative complications, while LCDs do not appear to provide this benefit. However, the evidence is limited by methodological heterogeneity and low certainty. Further high-quality studies are needed to establish optimal preoperative nutritional protocols.

Because of their condition, patients with morbid obesity develop several histopathological changes in the liver, such as non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), cirrhosis, and end-stage liver disease (ESLD). Hence, a liver transplant (LT) becomes an opportune solution for them. Due to many challenges during the perioperative and postoperative periods, these patients are recommended to lose weight before the surgery. There are many proposals to achieve this goal, such as intragastric balloons and many different bariatric surgery (BS) procedures in combination with a preparation diet (very-low-calorie diet, ketogenic diet, etc.). All the interventions focus on losing weight and keeping the continuity and functionality of the digestive tract to avoid postoperative complications. Thus, this review analyzes recent publications regarding the metabolic and pathophysiological impacts of BS in LT patients suffering from NAFLD-related cirrhosis, the effect of weight loss on postoperative complications, and exposes the cost-effectiveness of performing BS before, after, and at liver transplantation. Finally, the authors recommend BS before the LT since there are many positive effects and better outcomes for patients who lose weight before the procedure. Nevertheless, further multicentric studies are needed to determine the generalizability of these recommendations due to their impact on public health.