Caloric restriction and n-3 polyunsaturated fatty acid (PUFA) supplementation protect from some of the metabolic complications. The aim of this study was to assess the influence of a low calorie diet with or without n-3 PUFA supplementation on glucose dependent insulinotropic polypeptide (GIP) output and insulin sensitivity markers in obese subjects. Obese, non-diabetic subjects (BMI 30-40 kg/m(2)) and aged 25-65 yr. were put on low calorie diet (1200-1500 kcal/day) supplemented with either 1.8 g/day n-3 PUFA (DHA/EPA, 5:1) (n = 24) or placebo capsules (n = 24) for three months in a randomized placebo controlled trial. Insulin resistance markers and GIP levels were analysed from samples obtained at fasting and during an oral glucose tolerance test (OGTT). Caloric restriction with n-3 PUFA led to a decrease of insulin resistance index (HOMA-IR) and a significant reduction of insulin output as well as decreased GIP secretion during the OGTT. These effects were not seen with caloric restriction alone. Changes in GIP output were inversely associated with changes in red blood cell EPA content whereas fasting GIP level positively correlated with HOMA-IR index. Blood triglyceride level was lowered by caloric restriction with a greater effect when n-3 PUFA were included and correlated positively with fasting GIP level. Three months of caloric restriction with DHA + EPA supplementation exerts beneficial effects on insulin resistance, GIP and triglycerides. Combining caloric restriction and n-3 PUFA improves insulin sensitivity, which may be related to a decrease of GIP levels.

The numerous consequences of the coronavirus disease 2019 (COVID-19) pandemic in healthy young people and the lack of clarity as to the long-term disease outcomes have spurred the search for risk factors for SARS-CoV-2 infection. We aimed to evaluate the associations of nutritional behaviors, gut microbiota, and physical activity with the risk of COVID-19 in healthy young nonobese people. Data on body composition, anthropometric measurements, physical activity, dietary intake, and gut microbiota were obtained from 95 adults (mean age, 34.66 ± 5.76 years). A balanced diet rich in vegetables and fruit, including nuts, wholegrain cereal products, and legumes, covers the need for vitamins and minerals. Such a diet can be an effective measure to reduce the risk of COVID-19 in nonobese healthy physically active young people with normal immune function. People with balanced diet and an average daily consumption of >500 g of vegetables and fruit and >10 g of nuts had an 86% lower risk of COVID-19 compared with those whose diet was not balanced and who consumed lower amounts of these products. It is well documented that proper nutrition, physical activity, and maintenance of normal weight facilitate good health by ensuring optimal immune function. The beneficial effects of these interventions should be strongly emphasized during the COVID-19 pandemic.

A rise in the incidence of infections with severe acute respiratory syndrome coronavirus 2 has sparked the search for protective strategies against the new pathogen. It is known that individual food components can interact with different immune cells, modulating the immune response of the body. The aim of this study was to develop an index assessing the immunomodulatory potential of diet (POLA index) and to test its utility for the prediction of coronavirus disease 2019 (COVID-19) in a group of healthy young people following a traditional or vegetarian diet. Data on body composition, anthropometric measurements, physical activity, dietary intake, and gut microbiota were obtained from 95 adults (mean age, 34.66 ± 5.76 years). There was a strong correlation between the dietary inflammatory index and the POLA index (r = 0.90; p < 0.0001). Based on Cohen’s kappa statistic, there was a good agreement in qualitative interpretation between the two indices (kappa = 0.61; p < 0.0001). People on a diet with beneficial immunomodulatory effects had a lower risk of COVID-19 of approximately 80%, as compared with those on a diet with highly unbeneficial immunomodulatory effects. In daily practice, the POLA index might serve as a useful tool for dietitians to identify individuals whose diet is deficient in ingredients for optimal immune system function and change their dietary behavior to ensure optimal immune function that reduces the risk of infection.

Evidence for diet-driven immunomodulation remains limited in terms of practical tools. This pilot study prospectively evaluated the dietary POLA index in 51 women aged 25–45 years and living in Kraków, Poland. At baseline (2022), 7-day dietary intake and physical activity were recorded; stool samples were analyzed for gut microbiota composition; short-chain fatty acids were quantified using high-performance liquid chromatography; and fecal secretory IgA (sIgA), human β-defensin-2 (HBD-2), and calprotectin levels were measured by the enzyme-linked immuno-sorbent assay. In June 2023, post-baseline incidence of COVID-19 and influenza was self-reported. Participants were categorized into a group with beneficial immunomodulation (BIM, POLA score ≤ 5) and a group with unbeneficial/highly unbeneficial immunomodulation (UBIM + HUBIM, POLA score > 5). The incidence of COVID-19 or influenza was 7.7% (1/13) in the BIM group vs. 36.8% (14/38) in the UBIM + HUBIM group. After adjusting for age and smoking, the UBIM + HUBIM group had higher odds of infection compared with the BIM group (adjusted OR = 6.53; 95% CI: 1.02–129.85), corresponding to a higher absolute risk of 47.9% (95% CI 26.1–70.6) versus 12.3% (95% CI 1.4–58.1). The BIM group more often met the fiber and micronutrient adequacy targets and showed a higher proportion of sIgA levels within the reference range (92.3% vs. 60.5%), along with lower fecal succinic acid concentrations (median 3.27 mg/g vs. 4.32 mg/g). In this cohort, a favorable POLA score was associated with lower self-reported COVID-19 or influenza incidence and an sIgA profile suggestive of intestinal immune homeostasis. As this pilot study is underpowered, findings should be interpreted as exploratory and hypothesis-generating. Nonetheless, results support the POLA index as a practical diet-quality metric with potential immunomodulatory relevance.