Abstracts of Original Communications (University of Ireland, Galway, Republic of Ireland. 19–20 June 2002)

Plasma or serum 25-hydroxyvitamin D3 (25(OH) D3) is the most commonly used index of vitamin D status.Low 25(OH) D3 status, which is most likely to occur during late winter to early spring, may increase parathyroid hormone (PTH) concentrations, which, in turn, can lead to increased bone turnover and risk of bone mineral loss.While there is some limited data on the vitamin D status of elderly (>70 years) Irish women (Meade et al. 1986; Freaney et al. 1993), there is a dearth of information on the vitamin D status of Irish women aged 50-70 years, a group at increased risk of oestrogen deficiency-induced osteopenia.In the current study, fasting blood samples were collected (between 08.00 and 10.00 hours) from sixtysix apparently healthy free-living Irish women from the Cork city region, by advertising in a local newspaper.Respondents were aged between 50 and 70 years (mean age was 60 years).Blood sampling took place during February and March 2002.Bloods were processed to serum and analysed for 25(OH) D3 and PTH by enzymeimmunoassays (IDS Ltd, UK).The quality of serum 25(OH) D3 analysis in our laboratory is assured on an ongoing basis by participation in the DEQAS external quality assurance scheme (London, UK).Serum 25(OH) D3 cut-off values for defining vitamin D status as adequate, marginally deficient or severely deficient were: >40 nmol/l, 25-40 nmol/l and <25 nmol/l, respectively (Vieth, 1999).The adult normal range for PTH is 0.8-3.9pmol/l, and PTH levels >4.1 pmol/l were indicative of a state of hyperparathyroidism (as indicated by IDS Ltd).The current use of vitamin D-containing supplements was ascertained by questionnaire.None of the women had been on a sunshine holiday during the 3 months previous to the blood sampling period.Mean serum 25(OH) D3 concentration in all subjects (n 66) was 56.3 nmol/l (range 16.7-114.5nmol/l).Of the women tested, 24% and 6% could be classified as marginally and severely vitamin D deficient, respectively.However, of the 66 women sampled, 55% were taking a vitamin D-containing supplement (containing 5-10 µg vitamin D).Dividing the group into vitamin D supplement users and non-users revealed that of the supplement users none were severely vitamin D deficient and 17% were marginally vitamin D deficient.However, on the other hand, 37% and 13% of the non-supplement users were marginally or severely vitamin D deficient, respectively.In addition, the mean (SD) serum 25 (OH) D3 concentration in women taking vitamin D-containing supplements was significantly (P=0.001) higher than that in women not taking supplements (64.7 (23.4) versus 46.2 (20.8) nmol/l, respectively).Mean serum PTH concentration in all subjects (n 66) was 2.55 pmol/l (range 0.26-6.15pmol/l).There was no significant difference (P=0.262) in serum PTH levels between women who took vitamin D-containing supplements and those who did not (2.70 (1.26) versus 2.28 (1.16) pmol/l, respectively).In addition, 12% of the women could be classified as being in a state of hyperparathyoidism (PTH levels >4.1 pmol/l).Linear regression analysis showed there was no significant (P=0.194)correlation between serum PTH and 25 (OH) D3.In conclusion, a significant number of 50 to 70-year-old Irish women may be at risk of hypovitaminosis D during winter and early spring-time.Consumption of vitamin D-containing supplements appeared to protect against severe vitamin D deficiency and lessened the prevalence of marginal vitamin D deficiency in this group of women.In spite of the marked depletion in vitamin D stores in some women after the winter, in general the PTH concentrations of these subjects remained within the normal range.Further research is needed to determine the impact of hypovitaminosis D on bone metabolism and bone health in this age group.This work was supported by funding made available by the Irish

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