Effects of skin thickness, age, body fat, and sunlight on serum 25-hydroxyvitamin D

Abstract

We tested the hypothesis that the age-related decline in skin thickness may contribute to the age-related decline in serum 25-hydroxyvitamin D [25(OH)D]. We measured skinfold thickness on the back of the hand, serum 25(OH)D, height, and weight in 433 normal postmenopausal women. We also noted the average daily hours of sunlight in the month in which the observations were made and in the preceding 2 mo. Serum 25(OH)D was positively related to hours of sunlight (with a time lag of 2 mo) and to skin thickness, and negatively to body mass index (wt/ht2). Serum 25(OH)D fell significantly after age 69 y. Seasonal variation of serum 25(OH)D was greater in lean than in fat subjects, which we attributed to the larger fat mass and consequent larger pool size in the latter group. The results suggest that the tendency for serum 25(OH)D to fall with age is due in part to the age-related decline in skin thickness.

Assessment of serum 25(OH)D concentration in women of childbearing age and their preschool children in Northern Jordan during summer

“…Although the literature suggests that obesity is related to low serum 25(OH)D concentrations among individuals (Liel et al, 1988;Need et al, 1993;Holick, 2003;Parikh et al, 2004), and percentage body fat is inversely proportional to serum 25(OH)D concentrations in healthy women (Arunabh et al, 2003), owing to the decrease in bioavailability of vitamin D with obesity (Wortsman et al, 2000), in this study, BMI had no significant impact on mean serum 25(OH)D concentration among women.…”

Sunlight is an important determinant of vitamin D serum concentrations in cystic fibrosis

“…The total amount of UV light during the period May-October at our location is approximately 5889 J/cm 2 (estimated amount of UVB light 589 J/cm 2 ) and the total amount of UV light during the period November-April is approximately 1761 J/cm 2 (estimated amount of UVB light 176 J/cm 2 ). The curve of 25 (OH) D serum concentrations and that of varying intensity of UVB light from the sun run a parallel course with a time-lag of approximately 2 months, as was also described in healthy people (Need et al, 1993). A maximum is reached in late summer and a minimum at the end of the winter.…”

Change in plasma levels of vitamin D after consumption of cod-liver and fresh cod-liver oil as part of the traditional north Norwegian fish dish “Molje”

“…An inverse association between the BMI and 25(OH)D in blood has been reported in other studies (16,(25)(26)(27). Obesity has been considered to be an independent predictor of vitamin D deficiency (28).…”

“…The vitamin D concentrations found in the present study were low for the majority of the participants and, thus, contradict the anecdotal assumption that vitamin D status in north Norway is satisfactory (5). Since sunshine exposure has been considered to be the main source of vitamin D, its status is known to drop during winter and improve during summer months (16)(17)(18)(19). Lehtonen-Veromaa et al (7) found a prevalence of 25(OH)D levels ≤ 37.5 nmol/L in excess of sixty percent during winter, which reduced to less than two percent during the summer among 15-year-old Finnish girls in Turku, Southwest Finland.…”