Brief Synopsis of vitamin D research in UCC to date
In recent years, the Nutrition Department at University College Cork has had an active role in vitamin D research, either woriking alone or collaborating with other institutes. From the late 70’s to the early 90’s most of the vitamin D research was carried out in the elderly (>65-years-old), either free-living or institutionalized. This rsearch established a high prevalence of inadequate vitamin D status [25(OH)D] (ranging from 47 to 86%). In the early 1990’s, milk fortified with vitamin D was found to substantially increase vitamin D status in the elderly. Since then there has been an emphasis on the need for foodstuff fortification and supplement use in the healthy elderly, as well as the ‘high risk’ housebound and institutionalized.
The first National Nutrition Survey in the Republic of Ireland was carried out by the Department of Health in 1948 and the next was completed in 1988-89 by the Irish Nutrition and Dietetic Institute. This survey (Irish National Nutrition Survey 1990) observed vitamin D intake to range from 1.3µg/d to 2.6µg/d across the various age groups. When this survey was completed, it was thought that low dietary intakes of vitamin D were only significant for those, such as the elderly, who might have limited exposure to sunlight.
In 2001, analysis from the North/South Ireland Food Consumption Survey (NSIFCS), which used a nationally representative sample of the Irish population, showed a high proportion of Irish adults aged 18-64 years had low dietary intakes of vitamin D and were largely dependent on sunlight exposure for adequate vitamin D status. The mean daily intake (MDI) of vitamin D from all sources (including supplements) was 3.7µg in men and women. A significant increase was observed with age. Further analysis of foods for vitamin D content increased the MDI of vitamin D from all sources to 4.2µg (Hill et al, 2004). Seventy-four percent of the adults had a MDI less than 5µg. Men had a higher intake compared with women (4.4 and 4.0µg, respectively) and this intake increased significantly with age in both sexes. Meat and meat products (30.1%), fish and fish products (14.3%) and egg and egg dishes (9.1%) were the main contributors to vitamin D intake. Supplement use was also an important contributor to vitamin D intake (6.8% for males and 12% for females). Fortified ready-to-eat breakfast cereals were found to contribute 10% of vitamin D intake in a later analysis of the NSIFCS.
Analysis of the Northern Ireland Young Hearts project (Neville et al, 2002), showed vitamin D and calcium intakes reported by female adolescents (from YH1 and YH2; n = 205; 15-y) were positively associated with their bone mineral density (BMD) when measured in young adulthood (from YH3; 20-25-y).
Data from the Northern Ireland Young Hearts II (YH2) project, showed that 12- (n = 236) and 15- (n = 232) year old girls with a serum 25(OH)D greater than 74.1nmol/l had a significantly higher forearm bone mineral density (BMD) when compared with the girls with a serum 25(OH)D less than 46.3nmol/l (Hill et al, 2007).
An Irish National Children’s Food Survey (NCFS) which used a representative sample of 596 Irish children aged 5-12 years, showed mean intakes of vitamin D were 2.3µg. The RDA for Irish children of this age group is a range 0-10µg/d, increasing during pubertal years to 0-15µg/d(FSAI, 1999). The main determinant of vitamin D intake was the use of nutritional supplements. Total vitamin D intake was almost 4 times greater in supplement users (5.6µg/d) compared with non-users (1.5µg/d).
In 2005, vitamin D status and intakes were assessed in apparently healthy, free living Irish postmenopausal women (n = 59; Hill et al, 2005). Between 17 and 36% of these women had inadequate of vitamin D concentrations (25(OH)D <40nmol/l) during late-winter. The MDI was low (3.2µg) even when supplements were accounted for (5.8µg).
In 2006, a double-blind randomized controlled intervention study in a sample of 27 young adults, (aged 18-27-years) showed that after 8-weeks of supplementation with 15µg/d vitamin D3 and 1500mg of calcium an increase in serum 25(OH)D was observed, from 47.9nmol/l to 86.5nmol/l (Barnes et al, 2006). There was no significant change in the control group (1500mg calcium). However, no effect on bone turnover or PTH was observed in either the vitamin D group or the control group.
As there is limited information on vitamin D status in other age groups, besides the elderly, a cross-sectional observational study in 2006 was completed (Hill et al, 2006). This study analysed 4 female groups (11-13yr, 23-50yr, 51-69yr and 70-75yr) and 20-64yr-old males, during the late summer and late winter for vitamin D status (25(OH)D). In females between 4 and 19% and between 34 and 85% had serum 25(OH)D below 50nmol/l during late summer and late winter, respectively. In the males, 7% and 33% had serum 25(OH)D below 50nmol/l during the late summer and late winter, respectively. No males had a serum 25(OH)D below 25nmol/l, whereas, 2-30% of the females depending on age, had a serum 25(OH)D between 12.5 and 25nmol/l.
An area of interest at UCC is the relationship between vitamin D and inflammatory bowel diseases (IBD), which has resulted in studies including Crohn's disease patients. Crohn’s disease (CD) and ulcerative colitis (UC), collectively known as IBD, are chronic aggressive disorders, which affect approximately 35-55 per 100,000 people in Western Europe, the aetiology of which is complex and probably multifactorial. Suboptimal vitamin D status is common in CD patients, even in the summertime. Some studies on CD patients have shown the low vitamin D status increased the levels of biochemical markers of bone turnover and reduced BMD. Osteopenia and Osteoporosis are common in CD patients (30% and 10-12%, respectively).