[Vitamin D status of Icelandic children and youngsters: Longitudinal study]. / D-vítamínbúskapur íslenskra barna og ungmenna. Langtímarannsókn

OBJECTIVE: Vitamin D plays a key role for children's growth and physical developement, not only by promoting bone health but also by its influence on extraskeletal systems. The Icelandic Directorate of Health recommends a vitamin D concentration in blood of at least 50 nmol/l. The object of this study was to evaluate the vitamin D status of Icelandic children and youngsters at four different ages, and furthermore to evaluate changes in vitamin D concentrations over time and connection to parathyroid hormone status (S-PTH). MATERIAL AND METHODS: The subjects were students from six elemen-tary schools in Reykjavík, born in 1999. Blood tests were taken four times, in 2006, 2008, 2015 og 2017. Some of the subjects took part in all four tests, but more students joined in 2015 and 2017. RESULTS: In all the tests, around 60% of the subjects had lower vitamin D concentrations than recommended by The Icelandic Directorate of Health. Only 13% met the recommended criteria of a concentration over 50 nmol/l in repeated tests and 38.9% of the subjects had lower concentrations than recommended in at least two tests. There was no significant difference between sexes except that 17 year old girls had significantly higher Vitamin D concentrations than boys (p=0.04). S-PTH was negatively correlated to vitamin D concentrations at ages 7, 15 and 17 but there was not a significant correlation at age 9. S-PTH values were lowest at age 7 and then increased with age. CONCLUSION: The majority of Icelandic children and youngsters have vitamin D concentrations under the values recommended by The Icelandic Directorate of Health. In many cases, the concentrations are repeatedly too low. It is clear that there is a need for increased vitamin D intake within this group if the goal regarding recommended concentrations is to be achieved. However, the influence of vitamin D deficiency on public health is not fully known.

Vitamin D intake, serum 25-hydroxyvitamin D status and response to moderate vitamin D3 supplementation: a randomised controlled trial in East African and Finnish women.

Insufficient vitamin D status (serum 25-hydroxyvitamin D (S-25(OH)D)0·05 for differences between ethnic groups). In conclusion, high prevalence of vitamin D insufficiency existed among East African women living in Finland, despite higher vitamin D intake than their Finnish peers. Moderate vitamin D3 supplementation was effective in increasing S-25(OH)D in both groups of women, and no ethnic differences existed in the response to supplementation.

Effects of vitamin D2-fortified bread v. supplementation with vitamin D2 or D3 on serum 25-hydroxyvitamin D metabolites: an 8-week randomised-controlled trial in young adult Finnish women.

There is a need for food-based solutions for preventing vitamin D deficiency. Vitamin D3 (D3) is mainly used in fortified food products, although the production of vitamin D2 (D2) is more cost-effective, and thus may hold opportunities. We investigated the bioavailability of D2 from UV-irradiated yeast present in bread in an 8-week randomised-controlled trial in healthy 20-37-year-old women (n 33) in Helsinki (60°N) during winter (February-April) 2014. Four study groups were given different study products (placebo pill and regular bread=0 µg D2 or D3/d; D2 supplement and regular bread=25 µg D2/d; D3 supplement and regular bread=25 µg D3/d; and placebo pill and D2-biofortified bread=25 µg D2/d). Serum 25-hydroxyvitamin D2 (S-25(OH)D2) and serum 25-hydroxyvitamin D3 (S-25(OH)D3) concentrations were measured at baseline, midpoint and end point. The mean baseline total serum 25-hydroxyvitamin D (S-25(OH)D=S-25(OH)D2+S-25(OH)D3) concentration was 65·1 nmol/l. In repeated-measures ANCOVA (adjusted for baseline S-25(OH)D as total/D2/D3), D2-bread did not affect total S-25(OH)D (P=0·707) or S-25(OH)D3 (P=0·490), but increased S-25(OH)D2 compared with placebo (P<0·001). However, the D2 supplement was more effective than bread in increasing S-25(OH)D2 (P<0·001). Both D2 and D3 supplementation increased total S-25(OH)D compared with placebo (P=0·030 and P=0·001, respectively), but D2 supplementation resulted in lower S-25(OH)D3 (P<0·001). Thus, D2 from UV-irradiated yeast in bread was not bioavailable in humans. Our results support the evidence that D2 is less potent in increasing total S-25(OH)D concentrations than D3, also indicating a decrease in the percentage contribution of S-25(OH)D3 to the total vitamin D pool.