Vitamin D Levels and Seasonal Changes in Elderly Cretans, Men and Women

Special Article - Vitamin D Deficiency: Clinical Cases & Short Reports

Austin J Nutri Food Sci. 2016; 4(1): 1076.

Vitamin D Levels and Seasonal Changes in Elderly Cretans, Men and Women

Dretakis OE¹*, Malliaraki N¹, Dretakis EK² and Margioris AN¹

¹Department of Clinical Chemistry, School of Medicine, University of Crete, Greece

²School of Medicine, University of Crete, Greece

*Corresponding author: Dretakis OE, Department of Clinical Chemistry, School of Medicine, University of Crete, Greece

Received: November 29, 2015; Accepted: January 11, 2016; Published: January 19, 2016


Background: Low serum 25-hydroxyvitamin D [s25(OH)D] levels have been reported in a high proportion of institutionalized or home bound subjects and also in ambulatory elderly people with limited exposure to sunlight due to geographical location.

Aim of this study is to investigate the s25(OH)D status as well as its seasonal variation in ambulatory elderly people permanent inhabitants of Crete, the southernmost island of Europe.

Subjects and Methods: 101 ambulatory subjects, selected after applying strict exclusion criteria, from the Centres of Open Care for the Elderly, of Heraklion-Crete, 70 women and 31 men, (70,00±5,00 years and 73,00±5,49 respectively) Serum 25(OH)D, serum parathormone (sPTH), Ca, P, Cre, BMI and grade of mobility were assessed. In a subgroup of 25 subjects, s25(OH)D and sPTH were evaluated twice (winter and summer).

Results: Mean s25(OH)D was 51,46±27,32 nmol/L in women and 71,7±28,65 nmol/L in men. Levels = 30nmol/L were found to 10% of men and 30% of women whereas levels = 50nmol/L were found to 29% of men and 53,6% of women.

Mean sPTH was 59,77±28,92 pg/ml in women and 63,91±24,82 in men

Subjects with mobility A had higher levels of s25(OH)D than subjects with mobility B (t(99)=3,612 p=0,000) and summer levels of s25(OH)D were higher than the winter ones (p<0,001) whereas summer levels of sPTH were lower (p=0,007).

Conclusion: Despite of the geographic location of Crete, and the ?editerranean diet followed, there is a high prevalence of vitamin D deficiency among ambulatory community dwelling elderly, being much higher in women, which can be attributed to the inadequate exposure to sunlight and to the lack of foods fortified with vitamin D and/or the supplementation of Vitamin D.

Keywords: Vitamin D; Seasonal changes; Geographical location


The importance of vitamin D in calcium and phosphate homeostasis and bone metabolism and also the harmful effects of its deficiency in skeletal health in infancy (rickets) as well as in adult life (osteomalacia- osteoporosis) is well known [1].

Less known is the role of vitamin D in the development and function of the muscles [2-4].

Vitamin D deficiency has been found to be associated with muscle weakness, thus implicated as a risk factor for falling and hip fractures in the elderly [5,6].

Epidemiologic studies have shown that vitamin D deficiency is common among community dwelling people in European countries regardless of geographic location [7].

Serum 25(OH)D concentration <50 nmol/L are classed as mild vitamin D deficiency or insufficiency [8], whereas levels < 25 nmol/L denote moderate vitamin D deficiency and levels < 12.5 nmol/L denote severe vitamin D deficiency [9].

Many authors however claim that the cut-off value below which vitamin D insufficiency can be present is somewhere between 20 and 40 ng/ml (50-100 nmol/L) and have tendency to target values <30 ng/ ml (75 nmol/L) [10-12].

Currenty the most commonly agreed cut-off for vitamin D insufficiency is a serum 25(OH)D level < 75 nmol/L. This cut off value was derived from studies using immunoassays or protein-binding assays [13].

Vitamin D,

1) is produced endogenically by the action of solar ultra violet (UVB) rays on the skin from 7-dehydrocholesterol.

2) is taken by diet mainly from oily fish, meat, eggs and milk products.

Both sunlight and diet contribute to the store of the human body in vitamin D.

As long as the subject can be sufficienty exposed to sunlight in regular base there is no need for dietary intake for vitamin D. The dietary intake is also important because the prolonged exposure to sunlight may be harmful to the skin and also because the geographical location, the dressing habits, the quality of the skin and the urban mode of life reduce the possibility of the people to be exposed to the sunlight. The greatest proportion of circulating 25(OH)D and of 1, 25(OH)2D is binded with DBP (80-90%) and with alboumin (10- 20%), while only a very small proportion of them is free.

Thus, measurement of the free metabolites of vitamin D is not reliable index for clinical use. The half time of life of the free circulating 1, 25 (OH)2D is only 4 hours whereas that of 25(OH)D is 3 weeks.

Therefore the measurement of serum of 25(OH)D is considered to be the more reliable index to determine the vitamin D status of the subject.

Aim of the current study is to investigate the serum concentrations of 25(OH)D in community dwelling >65 years Cretans men and women.

Serum levels of parathormone (PTH), Cre, Ca and P are also investigated.

Subjects and Methods

One hundred and one community dwelling elderly subjects >/ 65 years, 70 women and 31 men were randomly enrolled from the centers of open care for the elderly in the city of Heraklion Crete. All 101 participants were informed for the purpose of the study and consent was obtained for participation and the study was approved by the local medical Committee. All 101 participants had the following characteristics:

More specifically the mean age of the 70 women was 70.00 ± 5.00 (65-81) and that of the 31 men was 73.00± 5.49 (65-82 years).

Clinical data

Age, body mass index (BMI) mobility, falls during preceding year, exposure to sunlight, type of diet, clothing habits, calcium intake were recorded.

The time of direct exposure to sunlight was estimated by questioning the patient about the time of direct exposure to sunlight and about the type of clothes used.

The 101 study participants followed (type A) Mediterranean diet of Crete in which the mean daily calcium intake was found to be 826mg [14]. Mobility was graded as (A) or (B) according to the ability of the participant to walk outdoors a distance of = 500m and to perform her or his activities without or with the occasional aid of a stick, respectively.

Biochemical data

Fasting blood samples were obtained between 9 and 10 am in the University Hospital of Heraklion Crete, from January to April, and were immediately transferred to the laboratories of Biochemistry and Nuclear Medicine of the hospital, where the following assays were done:

-Serum 25(OH)D concentrations. IDS OCTEIA 25-OH vitamin D kit. Enzyme immunoassay for quantification of 25(OH)D in human serum. Ref values 48-144nmol/L.

-Serum Parathormone (PTH).ELSA PTH. A solid phase two-site immunoradiometric assay. Model 13-CIS biointernational SA. Ref values: 15-65 pg/ml.

-Serum calcium, phosphate and creatinine were also measured using conventional methods, in all 101 study participants.

Statistical analysis

Data is expressed as mean ± SD, range (minimum-maximum), or medians (in case of violation of normality) for continuous variables and as percentages for categorical data. The Kolmogorov–Smirnov test was utilized for normality analysis of the parameters. . The comparison of variables between different groups was performed using the independent samples t-test and the Mann–Whitney U- test were used in case of a violation of normality.

The correlation between variables was estimated using Pearson or Spearman correlation coefficients.

All tests were two-sided and a p-value < 0,05 was considered to be statistically significant.

All analyses were carried out using the statistical package SPSS vers.

13.00 (SPSS Inc., Chicago, IL, USA) for Windows.


Clinical evaluation

Mobility, Falls, BMI, exposure to sunlight, diet: Able to walk a distance of =500 meters without the aid of a stick (mobility A), were 82% of the men vs 68%of the women, whereas 18% of the men vs 32% of the women used occasionally a stick (mobility B).

All 101 study participants performed everyday indoor and outdoors physical activity. Men spent more time in outdoors moderate to heavy physical activity including brisk walking, gardening and heavy lifting.

During the preceding year, women fell more often than men (24/70 vs 4/31 respectively) and 15 of these 24 women had mobility B.

Moreover, within the sample of 101 subjects, it was found that subjects with mobility A (63 subjects) had higher levels of 25(OH)D than subjects with mobility B (38 subjects), i.e. 63,89 ± 30.87 nmol/L vs 43.50 ± 20.59 nmol/L respectively (t(99) = 3,612 p = 0,000).

Thirteen of the 101 study subjects (5 males and 8 females) had a BMI<25.

Forty four (18 males and 26 females) had a BMI between 25,1 and 30 kg/m² (overweight) and 44 (7 males and 37 females) had a BMI >30 kg/m² (obese). Thus, 84% of the subjects, were overweight and obese.

All 101 study participants wore clothing covering their arms and legs (ie long sleeves and trousers or stockings) during the study period (ie January to April), which is traditional apparel in Crete, for the period from October to the end of May. None of the study participants used sun lamps.

?ll study participants followed the Mediterranean type A diet of Crete (Kafatos, 2000). More specifically the majority of study subjects (n=85), consumed three portions per day and 16 consumed two portions per day of locally produced milk or dairy products. All participants consumed olive oil and wholemeal bread or rusks often home made. Meat and fish consumed twice and once a week respectively whereas locally produced vegetables and fruits were consumed daily and fried legumes were consumed once a week by most of the participants. The type of diet followed by each of the study subjects, provided a dietary calcium intake of > 800mg/day. No one consumed foods fortified with vitamin D (Table 1).