Iceland and Vitamin D - many studies

Does less sun mean more disease? 215 days of winter in Iceland (No vitamin D from the sun)

Does Less Sun mean More Disease 5 minute video

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Icelanders (like others) with dementia have low levels of vitamin D - April 2020

Lifestyle and 25-hydroxy-vitamin D among community-dwelling old adults with dementia, mild cognitive impairment, or normal cognitive function
Aging Clinical and Experimental Research vol32, pg 2649–2656
Hrafnhildur Eymundsdottir, M. Chang, O. G. Geirsdottir, L. S. Gudmundsson, P. V. Jonsson, V. Gudnason, L. Launer, M. K. Jonsdottir & A. Ramel

Several studies have indicated that older adults with cognitive impairment have a poorer lifestyle than their healthy peers including lower 25-hydroxy-vitamin D levels (25OHD).

To investigate the associations between lifestyle and 25OHD depending on cognitive status among old adults.

Community-dwelling old adults (65–96 years) participated in this cross-sectional study based on the Age-Gene/Environment-Susceptibility-Reykjavik-Study. The analytical sample included 5162 subjects who were stratified by cognitive status, i.e., dementia (n = 307), mild cognitive impairment (MCI, n = 492), and normal cognitive status (NCS, n = 4363). Lifestyle variables were assessed and 25OHD was measured. The associations between lifestyle and 25OHD were calculated using linear models correcting for potential confounders.

According to linear regression models, 25OHD was significantly lower in older people with dementia (53.8 ± 19.6 nmol/L) than in NCS participants (57.6 ± 17.7 nmol/L). Cod liver oil (7.1–9.2 nmol/L, P < 0.001) and dietary supplements (4.4–11.5 nmol/L, P < 0.001) were associated with higher 25OHD in all three groups. However, physical activity ≥ 3 h/week (2.82 nmol/L, P < 0.001), BMI < 30 kg/m2 (5.2 nmol/L, P < 0.001), non-smoking (4.8 nmol/L, P < 0.001), alcohol consumption (2.7 nmol/L, P < 0.001), and fatty fish consumption ≥ 3x/week (2.6 nmol/L, P < 0.001) were related to higher 25OHD in NCS only, but not in participants with dementia or MCI.

Older people living in Iceland with dementia are at higher risk for 25OHD deficiency when compared to healthy individuals. Physical activity reported among participants with dementia, and MCI is low and is not significantly associated with 25OHD.

Lifestyle factors among NCS participants are associated with 25OHD levels. Importantly, healthy lifestyle should be promoted among individuals with MCI and dementia.
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See in VitaminDwiki Dementia is associated with low vitamin D - many studies

Fewer than 9% of Icelandic ICU patients had more than 30 ng of Vitamin D - June 2016

Severe vitamin D deficiency is common in critically ill patients at a high northern latitude
R. B. Kvaran, M. I. Sigurdsson, S. J. Skarphedinsdottir, G. H. Sigurdsson

Critically ill patients at southern latitudes have been shown to have low vitamin D levels that were associated with prolonged hospital stay. To our knowledge no studies have been conducted on vitamin D status amongst critically ill patients at high northern latitudes. Despite the Icelandic population traditionally taking vitamin D supplements, we hypothesized that the majority of critically ill patients in Reykjavik, Iceland have low vitamin D levels.
This was a prospective observational study on 122 patients admitted to Landspitali University Hospital intensive care unit. Serum vitamin D (25(OH)D) was measured in all patients on two occasions (first and second day). The prevalence of vitamin D deficiency and its effect on hospital stay was calculated.
Only 9% of patients had vitamin D levels recommended for good health (>75 nmol/l) and 69% were deficient (25(OH)D < 50 nmol/l). The average difference between the first and second vitamin D samples was 2.8 nmol/l. Forty-three percentage of the severely vitamin D deficient stayed in the ICU for more than 4 days compared to 19% of patients with better status (P = 0.196).
Vitamin D deficiency is very common in critically ill patients at high northern latitudes and patients with severely deficient vitamin D levels had trend towards longer intensive care unit stay. Furthermore, 43% of the patients had vitamin D levels under 25 nmol/l that is associated with osteomalacia. It appears that a single vitamin D measurement gives a reasonable clue about the vitamin D status in critically ill patients.

 Download the PDF from Sci-Hub via VitaminDWiki

Vitamin-D homeostasis amongst adult Icelandic population - 2004 (46 nmol average)

Laeknabladid. 90(1):29-36 [Article in Icelandic] PMID: 16819011
Oervar Gunnarsson 1 , Olafur Skúli Indriðason, Leifur Franzson, Edda Halldórsdóttir, Gunnar Sigurðsson
1 Division of endocrinology and metabolism, Iceland University Hospital, Fossvogi, 108 Reykjavík, Iceland.

Background: The purpose of this study was to examine the effect of vitamin D intake and production in skin on vitamin D homeostasis in adult Icelanders.

Methods: Participants were 30-85 years old, randomly selected from the registry of the Reykjavik area (64 degrees N) and answered a thorough questionnaire on diet and vitamin supplements. Concentrations of 25(OH)-vitamin D [25(OH)D] in peripheral blood were examined based on season during the study period February 2001-January 2003, vitamin D intake and age (age groups 30-45, 50-65, and 70-85 years old). We defined vitamin D deficiency as either [25(OH)D] <25 nmol/l or as [25(OH)D] where the inverse relationship between serum iPTH and [25(OH)D] became statistically significant.

Results: Of 2310 invited, 1630 subjects participated (70,6% participation) but 21 individuals were excluded due to primary hyperparathyroidism. Mean [25(OH)D] was 46.5-/+20 nmol/l but varied by season, age and vitamin D intake, highest in June-July, 52.1-/+19.8 and lowest in February-March, 42.0-/+20.5 (p<0.001). [25(OH)D] was highest in the oldest age group, 50.8-/+19.7, but lowest in the youngest, 42.5-/+20 as was the intake 16.6-/+10 microg/day compared to 9.9-/+9 microg/day in the youngest. The correlation between vitamin D intake and [25(OH)D] was highest for the oldest group, r=0.41, p<0.001 but lowest in the youngest, r=0.24, p<0.001. [25(OH)D] was significantly higher among users of vitamin supplements (45.4-/+19.7) or fish oil (53.0-/+18.4) than among non-users (38.0-/+18.9). Vitamin D insufficiency was seen among 14.5% of those participating according to traditional definition, but 50% were below [25(OH)D] of 45 nmol/l where negative correlation between [25(OH)D] and PTH became statistically significant.

Conclusions: The serum concentration of 25(OH)D at which vitamin D deficiency becomes biochemically significant is higher than traditionally thought. A daily intake of 15-20 microg/day during wintertime would be required to maintain normal homeostasis in Icelandic adults, which is considerably higher than present recommendations of 7-10 microg/day for adults. Further research is needed to define the limit for vitamin-D sufficiency.

Vitamin D status and current policies to achieve adequate vitamin D intake in the Nordic countries

Volume 49, Issue 6
Suvi T. Itkonen, Rikke Andersen, , Anne K. Björk, Åsa Brugård Konde, Hanna Eneroth, Maijaliisa Erkkola, Kristin Holvik, Ahmed A. Madar, Haakon E. Meyer, Inge Tetens, Jóhanna E. Torfadóttir, Birna Thórisdóttir, and Christel J.E. Lamberg-Allardt, +10 -10View all authors and affiliations

Aims: Nordic countries share fairly similar food culture and geographical location as well as common nutrition recommendations. The aim of this paper was to review the latest data on vitamin D status and intake and to describe the national supplementation and food fortification policies to achieve adequate vitamin D intake in the Nordic countries.

Methods: The data are based on results derived from a literature search presented in a workshop held in Helsinki in November 2018 and completed by recent studies.

Results: Vitamin D policies and the implementation of the recommendations differ among the Nordic countries. Vitamin D fortification policies can be mandatory or voluntary and widespread, moderate or non-existent. Vitamin D supplementation recommendations differ, ranging from all age groups being advised to take supplements to only infants. In the general adult population of the Nordic countries, vitamin D status and intake are better than in the risk groups that are not consuming vitamin D supplements or foods containing vitamin D. Non-Western immigrant populations in all Nordic countries share the problem of vitamin D insufficiency and deficiency.

Conclusions: Despite the common nutrition recommendations, there are differences between the Nordic countries in the implementation of the recommendations and policies to achieve adequate vitamin D intake and status. There is a need for wider Nordic collaboration studies as well as strategies to improve vitamin D status, especially in risk groups.
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48 nmol = Vitamin D levels of Children in Iceland - 2020

Vitamin D status of Icelandic children and youth: A long-term study

Original in Icelandic

Vitamin D in northern latitudes: Intake and status in Icelandic children - thesis - 2018

Title: Vitamin D in northern latitudes: Intake and status in Icelandic children
Alternative Title: D-vítamín á norðlægum slóðum: Inntaka og búskapur íslenskra barna.
Author: Þórisdóttir, Birna
Advisor: Ingibjörg Gunnarsdóttir og Bryndís Eva Birgisdóttir
Date: 2018-08
Language: English
University/Institute: Háskóli Íslands
University of Iceland
School: Heilbrigðisvísindasvið (HÍ)
School of Health Sciences (UI)
Department: Matvæla- og næringarfræðideild (HÍ)
Faculty of Food Science and Nutrition (UI)
ISBN: 9789935939449
Subject: Infant; Child; Vitamin D; Nutrition policy; Public health; Ungbörn; Börn; D vítamín; Næringarfræði; Næringarstefna; Doktorsritgerðir

Background: Adequate nutrition in childhood is essential for growth, development and health. Vitamin D supplement use is recommended in Iceland, starting in infancy. Little information exists on the vitamin D status of Icelandic infants and children. Vitamin D has been suggested to affect the development of sensitization to food allergens and food allergy. Aim: To study adherence to dietary guidelines among 6-year-old children (paper I), their vitamin D intake and vitamin D status at 12 months and 6 years (papers II and III) and compare vitamin D and feeding in infancy between 6-year-old children IgE-sensitized to food allergens and non-sensitized children (paper IV).

Methods: The study population is a nationally representative Icelandic cohort of infants born in 2005, followed up at 6 years of age. Three-day weighed food records were kept at 9 months (n=196), 12 months (n=170) and 6 years (n=162). Total vitamin D intake was calculated from both diet and supplements. Further infant nutrition data was collected by dietary history from birth to 5 months and by monthly 1-day food records at 5-8 and 10-11 months of age. Serum 25-hydroxyvitamin D (25(OH)D) was measured at 12 months (n=76) and 6 years (n=139) and serum-specific IgE-antibodies against food at 6 years (n=144). Cut-off values for vitamin D deficiency, insufficiency, sufficiency and possibly adversely high levels were set at 25(OH)D <30 nmol/L, 30-50 nmol/L, >50 nmol/L and >125 nmol/L, respectively. The cut-off value for sensitization was set at specific IgE ≥0.35 kUA/L.

Results: Adherence to dietary guidelines varied among 6-year-old children but was poor in general. A quarter, or less, of the children followed the guidelines for fruit and vegetables, fish, wholegrain bread and other fiber-rich cereals and vitamin D supplements. The food intake was mirrored in a non-optimal distribution of macronutrients, fiber and salt intake. Vitamin and mineral density of the diet seemed however adequate, except for vitamin D. Supplements (fish liver oil or liquid infant drops during the first months) were the main sources of vitamin D. Total vitamin D intake was higher at 9-12 months than at 6 years (the median intakes were 8.7 μg/d vs. 4.9 μg/d, respectively, p<0.01). The mean±SD concentration of 25(OH)D at 12 months was 98±32 nmol/L, with 92% of infants defined as having sufficient vitamin D status and none deficient. Vitamin D intake at 9-12 months, either from use of vitamin D supplements or consumption of fortified foods in significant amounts (e.g., 200 ml/d of formula), or both, was the main observed determinant for vitamin D status 12 months. Breastfeeding and season were not associated with vitamin D status at 12 months. Taking vitamin D supplements increased the risk of serum 25(OH)D at possibly adversely high levels, observed in a quarter of 12-month-old infants. At 6 years, vitamin D status was lower than in infancy (57±18 nmol/L), 30% of children were insufficient and 6% deficient. Higher total vitamin D intake at 6 years, blood samples collected in summer and higher serum 25(OH)D measured at 12 months, were associated with higher likelihood of vitamin D sufficiency at 6 years. The vitamin D status decreased during autumn in children not using vitamin D supplements. Fourteen 6-year-old children (10%) were sensitized to food allergens. Higher vitamin D intake at 12 months (OR=0.8, 95% CI=0.7-0.99) and vitamin D supplement use at 6 years (OR=0.2, 95% CI=0.1-0.98) were associated with lower risk of sensitization. Introduction of solid foods prior to four months was associated with increased risk of sensitization (OR=4.9, 95% CI=1.4-17). More weight gain and head circumference growth from 0-2 months and higher prevalence of overweight at 6 years was observed among sensitized than non-sensitized children.

Conclusions: The results indicate that a public health effort among Icelandic children is needed to increase adherence to dietary guidelines, including vitamin D supplement use. Healthy Icelandic infants and children receiving the recommended 10 µg/d vitamin D are likely to be vitamin D sufficient. Vitamin D insufficiency and deficiency may however be prevalent among 6-year-old children due to insufficient intake. Monitoring of diet and vitamin D status among Icelandic infants and children is important, looking both at low and high vitamin D levels. Further studies are needed on the associations of vitamin D and diet with food sensitization and allergy.
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Note: Thesis includes several of the author's publications

Vitamin D levels crash in Icelandic children by age 6 - Feb 2016

Vitamin D Intake and Status in 6-Year-Old Icelandic Children Followed up from Infancy
Nutrients 2016, 8(2), 75;
by Birna Thorisdottir 1,*,Ingibjorg Gunnarsdottir 1,Laufey Steingrimsdottir 1,Gestur I. Palsson 2,Bryndis E. Birgisdottir 1 andInga Thorsdottir 1

  • 1 Unit for Nutrition Research, Faculty of Food Science and Nutrition, School of Health Sciences, University of Iceland and Landspitali University Hospital, Reykjavik 101, Iceland
  • 2 Children’s Hospital, Landspitali University Hospital, Reykjavik 101, Iceland

5X fewer children with > 30 ng at age 6:
Possible reasons: 1) Only give 400 IU independent of weight; 2) Cease giving Vitamin D after age 1

High serum 25-hydroxyvitamin D (25(OH)D) levels have been observed in infants in Nordic countries, likely due to vitamin D supplement use. Internationally, little is known about tracking vitamin D status from infancy to childhood. Following up 1-year-old infants in our national longitudinal cohort, our aims were to study vitamin D intake and status in healthy 6-year-old Icelandic children (n = 139) and to track vitamin D status from one year of age. At six years, the mean 25(OH)D level was 56.5 nmol/L (SD 17.9) and 64% of children were vitamin D sufficient (25(OH)D ≥ 50 nmol/L). A logistic regression model adjusted for gender and breastfeeding showed that higher total vitamin D intake (Odds ratio (OR) = 1.27, 95% confidence interval (CI) = 1.08–1.49), blood samples collected in summer (OR = 8.88, 95% CI = 1.83–43.23) or autumn (OR = 5.64, 95% CI = 1.16–27.32) compared to winter/spring, and 25(OH)D at age one (OR = 1.02, 95% CI = 1.002–1.04) were independently associated with vitamin D sufficiency at age six. The correlation between 25(OH)D at age one and six was 0.34 (p = 0.003). Our findings suggest that vitamin D status in infancy, current vitamin D intake and season are predictors of vitamin D status in early school age children. Our finding of vitamin D status tracking from infancy to childhood provides motivation for further studies on tracking and its clinical significance.
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Note: Iceland is one of the potential sites for a very large Vitamin D trial in 2023

Possible large Vitamin D intervention trial: Iceland, Saudi Arabia etc.

Top Icelandic disease concerns (Global Burden of Disease) - 2010

Top Icelandic disease concerns - Global Burden of Disease 2010
Top 10 causes of death in Iceland


Iceland Vitamin D level 46 n mol(18 ng)

Details: Age: 30-85
Gender: Men and Women
Vitamin D Levels (nmol/L): 46.1
Number of participants: 944
Steingrimsdottir L et al (2005) Relationship between serum parathyroid hormone levels, vitamin D sufficiency, and calcium intake. JAMA 294:2336-2341 URL:

Vitamin D intake from cod = ~400 IU daily average - not nearly enough for aduls

100 IU of vitamin D per ounce of cod
assume 50 kg of cod consumed per year (Icelanders consume 92 kg of fish/year
Daily consumtion of cod = 140 grams/day = 140 grams/day * 1 ounce/30 grams = 4 ounces/day

Omega-3 intake from cod = ~300 mg/day

Cod contains 221 milligrams of omega-3 fatty acids per 100 grams,
Assume 50 kg of cod consumed per year (Icelanders consume 92 kg of fish/year
Omega-3 Reduces risk of Breast Cancer sometimes reduced by a larger amount than by Vitamin D

VitaminDWiki - Many diseases increase with latitude (low UV, Vitamin D) charts with Iceland

Breast Cancer

Lung Cancer

See also VitaminDWiki

172 Vitamin D publications by Icelandic authors as of Jan 2023

European PubMed

2 out of 3 Icelandic men are overweight or obese (highest rate in Europe)

Statistica 2022
Overview Obesity and Vitamin D contains the following summary


  • Normal weight     Obese     (50 ng = 125 nanomole)

9,630 Iceland and Vitamin D articles in Google Scholar as of Jan 2023

Google Scholar

Chronic pain in Iceland

Multidisciplinary Pain Rehabilitation Programs in Iceland: An Exploration and Description of the Short-term and Long-term Effects - Feb 2022

A population based study of the prevalence of pain in Iceland - 2010
Prevalence estimates of pain differ depending on how it is defined and measured and on the populations
studied. It has been estimated that on a given day, as many as 30–44% of the general population experience some kind of pain. Information about the prevalence of pain in Iceland is not available.
The aims of this study were to evaluate the prevalence of pain of various origins among the general population of Iceland,
to test hypotheses regarding relationships between pain, quality of life (QOL) and demographic variables,
to evaluate participants’ beliefs about causes of their pain, and to evaluate how those who experience
pain manage it. A random sample of 1286 adults was drawn from a national registry holding information about all citizens of Iceland. Data were collected with a postal-survey. Pain was evaluated with the
Brief Pain Inventory (BPI), with instructions modified to evaluate pain in the past week as opposed to
the past 24 h. Of 1286 invited, 599 (46.6%) participated, of which, 232 had experienced pain in the past
week (40.3%). Participants had a mean (SD) age of 44.94 (17.12) years and 56% were women. Those who
had pain perceived their health to be worse than those who had not [B = −0.91, SE = 0.15, Wald = 38.75,
p = 0.00], but did not differ on other variables. Of 232 individuals reporting pain, 183 (79.6%) or 30.6%
of the total sample had experienced pain for more than three months. On a scale from 0 “no pain” to
10 “pain as bad as I can imagine” the mean (SD) pain severity score (composite of four pain severity
scores) for the 232 participants reporting pain was 3.21 (1.73) and pain interference with life activities
2.59 (1.98), also on a 0–10 scale. Pain severity predicted pain interference [B = 0.71; F = 126.14; df = 1,206;
p = 0.00], which mediated the effects of pain severity on mood and QOL. Between Pain Interference with
Life and Positive Affect [B = −0.06; F = 4.53; df = 1,196; p = 0.04], between Pain Interference and Negative Affect [B = 0.15; F = 23.21; df = 1,196; p = 0.00], and between Pain Interference and Global Quality of
Life [B = −0.18; F = 29.11; df = 1,196; p = 0.00].
Most frequent causes for pain were

  • strain injuries (n = 79),
  • resulting from work or sports activity, arthritis (n = 39),
  • mechanical problems (e.g. due to birth defects,curvature, slipped discs, etc.) (n = 37),
  • various diseases (n = 31) and accidents (n = 30).

Nineteen participants did not know what caused their pain. Treatments for pain varied, but most had used medications alone (n = 76) or in combination with other treatments (n = 61). The prevalence of pain in the general population of Icelandic adults is similar to what has been reported. Estimates of chronic pain are towards the
higher end when compared to data from other European counties, yet comparable to countries such as
Norway. This raises questions about possible explanations to be looked for in genetics or cultural point of
view. This population based study provides valuable information about the prevalence of pain in Iceland
and also supports findings previously reported about pain in the neighboring countries.

Whether the weather influences pain: High prevalence of chronic pain in Iceland and Norway: Common genes? Or lack of sunshine and vitamin D? - 2010
Prevalence chronic pain 31% in Iceland vs 12% in Spain

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