1. Introduction
Allergies
ALLERGIES
Vitamin D is crucial to the health and performance of athletes. Although the exact vitamin D requirements for athletes have not been established, maintaining a 25(OH)D level of at least 40 ng/mL is considered beneficial. This randomized controlled intervention study aimed to determine whether an individual loading dose formula for vitamin D supplementation is more effective than standardized supplementation and suitable enough for athletes to meet a target value of 40 ng/mL. In a 10-week supplementation study conducted during the winter months in Germany, 90 athletes with insufficient vitamin D levels (25(OH)D < 30 ng/mL) were randomly assigned to receive either a universal dose of 2000 IU/day of vitamin D or a loading dose of 4000 IU/day, followed by a maintenance dose of 1000 IU/day. The total 25(OH)D concentration was measured from dried blood spots at three time points: at baseline, at the computed date of 40 ng/mL, and after the 10-week period. Additionally, a vitamin-D-specific questionnaire was issued. On the day when 25(OH)D blood concentrations of 40 ng/mL were calculated to prevail, the individualized group had a significantly higher 25(OH)D level than the standardized group (41.1 ± 10.9 ng/mL vs. 32.5 ± 6.4 ng/mL, Vitamin D has hormone-like effects that exert its actions ubiquitously in the human body [Vitamin D is crucial for athletes whose bones may be more strained than those of the general population because of its main impact on bone metabolism by modulating calcium resorption from the bone [Given its active role in muscle function, the potential of vitamin D to enhance athletic performance is a topic of much debate [To date, no athlete-specific recommendations have been established for vitamin D intake or supplementation. Athletes at a higher risk of vitamin D inadequacy may benefit from vitamin D supplementation guidelines. These include indoor athletes, athletes living at a latitude of 50° N or higher, and athletes with training regimens in the early mornings or evenings [Several investigations have been undertaken to determine the optimal vitamin D supplementation regimens for correcting vitamin D status when endogenous synthesis is impaired. However, none of these studies provided specific guidelines applicable to athletes’ daily lives. Reference values for vitamin D intake for adults in Northern Europe (latitudes above 40° N) range from 200 to 800 IU per day [In addition, the tolerable upper intake level (UL) of vitamin D exhibits a range of discrepancies among the various sources. According to the EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA) [As standardized recommendations for vitamin D intake do not exist, and due to many factors influencing vitamin D status, a more individualized supplementation strategy for vitamin D status optimization should be targeted. A personalized approach to correct insufficient vitamin D status could be based on body weight and the 25(OH)D baseline concentration. In 2010, Groningen et al. published a formula to correct individual vitamin D deficiencies [The objective of this study was to determine the applicability of Groningen’s formula in athletes. To achieve this, this study compared the effectiveness of individualized vitamin D supplementation versus standardized supplementation in correcting inadequate 25(OH)D concentrations enough to reach a level of 40 ng/mL. Therefore, for a 10-week intervention period, athletes with an insufficient vitamin D status (25(OH)D < 30 ng/mL) were administered either a loading dose followed by a maintenance dose or a standardized dose throughout the study period.