[Vitamin D Intake and Serum 25-OH-vitamin D Concentration in Different Age Groups of Icelandic Women.]

Objective: The aim of this study was to evaluate the vitamin D intake and serum concentrations of 25-OH-vitamin D (25-OH-D) in different age groups of Icelandic women. The seasonal variation of 25-OH-D and its relationship with parathyroid hormone (PTH) level was evaluated but some studies have indicated that subclinical vitamin D deficiency may lead to osteoporosis because of secondary elevations of parathyroid hormone levels and subsequent bone mineral release.

Material And Methods: 25-OH-D was measured (RIA, Incstar) in serum from the following age groups of women; 12-15 years (n=325), 16, 18 and 20 years (n=247), 25 years (n=86), 34-48 years (n=107) and in 70 years old (n=308). PTH (IRMA, Nichols) was measured only in the 70 years old. vitamin D intake was assessed by a standardized food frequency questionnaire. The seasonal variation of 25-OH-D was evaluated in the age group 12-15 years and 70 years old.

Results: In the different age groups the 25-OH-D concentration was positively correlated to vitamin D intake (r=0.2-0.54; p<0.05). The mean concentration of 25-OH-D in 12-15 years old was 34.6+/-22 nmol/L compared to 53.9120 nmol/L in the 70 years old, p<0.01. The levels of the other age groups were in between. A marked seasonal variation in 25-OH-D was obser notved in the 12-15 years old with low vitamin D intake whereas only a slight seasonal variation was noted in the 70 years old with a mean vitamin D intake of 15 ug/day.

Conclusions: The vitamin D status amongst 70 years old women in Iceland is good because of common intake of codliveroil and vitamin D supplements (83%). The desirable level for 25-OH-D in this age group seems to be around 50 nmol/L and this level is achieved by the intake of 15-20 ug/day (600-800 units) of vitamin D. Vitamin D deficiency is however common amongst 12-15 years old during late winter. Low serum 25-OH-D levels are also common amongst the other age groups studied during late winter. From the results it seems reasonable to recommend that foods like milk should be fortified with vitamin D in Iceland, especially during winter time.