Seemingly paradoxical seasonal influences on vitamin D status in nursing-home elderly people from a Mediterranean area

Objective We investigated vitamin D status in institutionalized elderly subjects by measuring serum 25-hydroxyvitamin D (25[OH]D) and its association with season and other factors: age, gender, nutritional status, cognitive function, functional ability, dietary intake, vitamin D supplement consumption, and disease. Methods The cross-sectional study included 86 subjects, 65–94 y of age (29 men and 57 women), who lived in three nursing homes in Murcia, a Spanish Mediterranean area. The Mini Nutritional Assessment, Short Portable Mental Status Questionnaire, and BI were used to evaluate nutritional status, functional ability, and cognitive function, respectively. Serum 25(OH)D concentrations were used to assess vitamin D status. The thresholds of inadequacy were considered to be <25 nmol/L (vitamin D deficiency) and <50 nmol/L (vitamin D insufficiency). Results Body mass index was 28.8 ± 5.8 kg/m2 (mean ± SD). Vitamin D dietary intake was very much below the recommended dietary intake. The Mini Nutritional Assessment was 23.6 ± 4.0, cognitive function was 7.8 ± 1.9, and functional ability 82.9 ± 23.1. The percentages of subjects with inadequate serum 25(OH)D concentrations were 58.2% and 32.6%, taking into consideration cutoffs of 50 and 25 nmol/L, respectively. Vitamin D deficiency was more common in women (40.3%) than in men (20.7%). Serum 25(OH)D concentrations varied significantly with the season in which the samples were taken, but not with the other factors analyzed. Conclusion In this Mediterranean area, a substantial percentage of institutionalized subjects showed an inadequate vitamin D status, which could be remedied by the consumption of vitamin D–fortified foods and/or vitamin D supplements, especially during the summer months.