Background: Improved therapy in CF has led to an overall improvement in nutritional status. The objectives of our study are: to cross-sectionally assess nutritional status and serum levels of fat-soluble vitamins; to retrospectively evaluate the efficacy of modulators on nutritional status and fat-soluble vitamin levels. Methods: In patients younger than 2 years of age, we evaluated growth, in patients aged 2–18 years, we assessed BMI z-scores, and in adults, we assessed absolute BMI values. Levels of 25(OH)D, vitamins A, and E were measured. Results: A cross-sectional analysis was conducted on 318 patients, 109 (34.3%) with pancreatic sufficiency. Only three patients were under 2 years old. In 135 patients aged 2–18 years, the median BMI z-score was 0.11, and 5 (3.7%) patients had malnutrition (z-score ≤ 2SD). In 180 adults, the median BMI was 21.8 kg/m². Overall, 15 (13.7%) males (M) and 18 (25.3%) females (F) were underweight (18 < BMI > 20); 3 (2.7%) M and 5 (7.0%) F had a BMI < 18. Suboptimal 25(OH)D levels were found in patients with pancreatic insufficiency. The prevalence of deficiency of vitamins A and E is low. After one year of treatment with modulators, the increase in BMI was more consistent (M: 1.58 ± 1.25 kg/m² F: 1.77 ± 1.21 kg/m²) in elexacaftor/tezacaftor/ivacaftor (ETI)-treated patients compared with other modulators, with a significant increase in levels of all fat-soluble vitamins. Conclusions: Malnutrition is present in a limited number of subjects. The prevalence of subjects with suboptimal 25(OH)D levels is high. ETI showed a beneficial effect on nutritional status and circulating levels of fat-soluble vitamins.

Background/Objectives: Hereditary fructose intolerance (HFI) is a rare autosomal recessive metabolic disorder caused by variants in the ALDOB gene, resulting in aldolase B deficiency. Symptoms occur after the ingestion of fructose, sucrose, or sorbitol, leading to metabolic toxicity. Management is exclusively dietary, but clinical practice remains highly variable. This survey aimed to investigate current Italian dietary management practices for patients with HFI. Methods: A cross-sectional centre-level survey was conducted using a 29-item questionnaire distributed to metabolic dietitians within the Italian Society for the Study of Inherited Metabolic Diseases network between April and May 2026. Results: Data from 27 dietitians across 15 Italian inherited metabolic disease centres were analysed. Over half of the centres (53.3%) provided care for both paediatric and adult patients, and all centres (100%) supplied structured educational materials for the fructose-, sucrose-, and sorbitol-restricted diet. Marked heterogeneity was observed in dietary practices, particularly in the classification of sugars and sweeteners, recommendations for cereal-based products, and fibre supplementation strategies. Cereal-based dietary guidance was provided by 10/15 centres (66.7%), ranging from no specific recommendations (5/15, 33.3%) to a preference for refined grains (7/15, 46.7%) or fibre-based restrictions (2/15, 13.3%). With regard to sugars and sweeteners, consensus was observed only for maltitol and sorbitol, which were classified as prohibited by all centres (15/15, 100%). Mannitol and isomalt were prohibited in 14/15 centres (93.3%). All other compounds showed variable recommendations across centres, including xylitol (prohibited 46.7%, permitted 40.0%), erythritol (permitted 60.0%), and sucralose (prohibited 33.3%, permitted 20.0%, restricted 20.0%, unspecified 26.7%). Vitamin C (100%) and folic acid (86.6%) were the most commonly prescribed supplements. One-third (33%) of the centres required the use of fibre supplements or osmotic laxatives to manage chronic constipation, with wide variability in the specific type of fibre recommended. Conclusions: These findings highlight substantial heterogeneity in dietary management of HFI across specialised Italian centres and support the development of evidence-based, standardised nutritional guidelines to improve the consistency of care, nutritional adequacy, and patient outcomes.