Iodine status and determinants in adults in Norway - results from a population-based health examination survey (The HUNT Study).

Background: In Norway, there is a lack of knowledge about the iodine status in the general and older adult population, and there is no established national monitoring programme for iodine. Several studies have indicated that iodine deficiency is prevalent in subgroups of the population. Salt iodisation is currently being considered as a measure to increase the population iodine status. In this cross-sectional study, the aim was to evaluate iodine status and determinants in the adult and older adult population in Mid-Norway, before salt iodisation is likely to be initiated. Methods: The study sample was a subsample of participants in the fourth wave of the population-based Trøndelag Health Study (HUNT4, 2017-2019) with available spot-urine samples. This subsample included participants with 25-64 years (n = 500) and 70-79 years (n = 250). The urine samples were analysed for iodine and creatinine. Information on the habitual intake of milk/yoghurt, fish, supplement use, use of thyroid medication and relevant background factors was collected through a general questionnaire. Multivariable quantile regression was used to model differences in the median urinary iodine concentration (UIC) by determinants. Estimates were weighted to match the age and sex distribution of the Norwegian population aged 25-79 years in 2019. Results: Median UIC was 97 µg/L (95% confidence interval [CI]: 92, 103) indicating borderline iodine deficiency at a group level. The median UIC increased with age, and iodine status was insufficient in participants below age 55 years (median 92 µg/L [95% CI: 85, 99]). Important determinants of UIC were habitual milk/yoghurt intake, daily supplement use and current use of thyroid medication, but not intake of lean or fatty fish. Risk of mild-to-moderate iodine deficiency was seen in those with a low intake of milk/yoghurt, no supplement use and who did not use thyroid medication. No group was identified as being at risk of iodine excess. Conclusion: Iodine status was adequate in older adults but mildly deficient in adults under 55 years. Milk intake, supplement use and use of thyroid medication are important determinants of iodine intake in Norway.

Vitamin D - a scoping review for Nordic nutrition recommendations 2023.

Vitamin D is an essential nutrient. Its role in calcium and phosphorous metabolism, and in the development and maintenance of a healthy skeleton is well documented. In addition, there is some evidence for vitamin D decreasing total mortality and cancer mortality modestly, but not cancer incidence. Vitamin D is unique, as both diet and sun induced production in skin are sources to this vitamin. Individual vitamin D status is thus a sum of both sun exposure and dietary intakes. The discovery of vitamin D receptors and the activation of biological active vitamin D in numerous tissues and organs in the body has given support to hypothesis on vitamin D having extra-skeletal functions. The scientific literature on vitamin D and several health outcomes is high in numbers and has been increasing exponentially the last two decades. However, despite this large body of scientific publications and improvement in study quality, vitamin D supplementation has not shown to give additional health benefits when status is in sufficient range (i.e. circulating 25 hydroxyvitamin D >50 nmol/L). Well-designed studies on insufficient or deficient individuals are lacking. The totality of evidence does not support that increased intake of vitamin D beyond current recommendation will have additional beneficial health effects.

Prevention of covid-19 and other acute respiratory infections with cod liver oil supplementation, a low dose vitamin D supplement: quadruple blinded, randomised placebo controlled trial.

OBJECTIVE: To determine if daily supplementation with cod liver oil, a low dose vitamin D supplement, in winter, prevents SARS-CoV-2 infection, serious covid-19, or other acute respiratory infections in adults in Norway. DESIGN: Quadruple blinded, randomised placebo controlled trial. SETTING: Norway, 10 November 2020 to 2 June 2021. PARTICIPANTS: 34 601 adults (aged 18-75 years), not taking daily vitamin D supplements. INTERVENTION: 5 mL/day of cod liver oil (10 µg of vitamin D, n=17 278) or placebo (n=17 323) for up to six months. MAIN OUTCOME MEASURES: Four co-primary endpoints were predefined: the first was a positive SARS-CoV-2 test result determined by reverse transcriptase-quantitative polymerase chain reaction and the second was serious covid-19, defined as self-reported dyspnoea, admission to hospital, or death. Other acute respiratory infections were indicated by the third and fourth co-primary endpoints: a negative SARS-CoV-2 test result and self-reported symptoms. Side effects related to the supplementation were self-reported. The fallback method was used to handle multiple comparisons. RESULTS: Supplementation with cod liver oil was not associated with a reduced risk of any of the co-primary endpoints. Participants took the supplement (cod liver oil or placebo) for a median of 164 days, and 227 (1.31%) participants in the cod liver oil group and 228 (1.32%) participants in the placebo group had a positive SARS-CoV-2 test result (relative risk 1.00, multiple comparison adjusted confidence interval 0.82 to 1.22). Serious covid-19 was identified in 121 (0.70%) participants in the cod liver oil group and in 101 (0.58%) participants in the placebo group (1.20, 0.87 to 1.65). 8546 (49.46%) and 8565 (49.44%) participants in the cod liver oil and placebo groups, respectively, had ≥1 negative SARS-CoV-2 test results (1.00, 0.97 to 1.04). 3964 (22.94%) and 3834 (22.13%) participants in the cod liver oil and placebo groups, respectively, reported ≥1 acute respiratory infections (1.04, 0.97 to 1.11). Only low grade side effects were reported in the cod liver oil and placebo groups. CONCLUSION: Supplementation with cod liver oil in the winter did not reduce the incidence of SARS-CoV-2 infection, serious covid-19, or other acute respiratory infections compared with placebo. TRIAL REGISTRATION: ClinicalTrials.gov NCT04609423.

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

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.

Association of High Intakes of Vitamins B6 and B12 From Food and Supplements With Risk of Hip Fracture Among Postmenopausal Women in the Nurses' Health Study.

Importance: Vitamin supplementation far exceeding recommended doses is popular in segments of the population. However, adverse effects can occur. In a previous secondary analysis of combined data from 2 double-blind randomized clinical trials (RCTs), an unexpected increased risk of hip fracture was found among those treated with high doses of vitamin B6 in combination with vitamin B12. Objectives: To study if high intakes of vitamins B6 and B12 from food and supplements were associated with a risk of hip fracture in the Nurses' Health Study and to investigate whether combined high intakes of both vitamins conferred a particularly increased fracture risk. Design, Setting, and Participants: In this prospective cohort study, 75 864 postmenopausal women in the United States were followed up from June 1984 through May 2014. The dates of analysis were July 2016 to June 2018. Information on hip fracture and a wide range of potential confounders was collected at baseline and with biennial follow-up questionnaires. Extensive dietary information was collected approximately every 4 years with a semiquantitative food frequency questionnaire. Relative risks (RRs) were calculated by Cox proportional hazards regression, with cumulative average intakes of vitamins B6 and B12 as main exposures, adjusting for potential confounders. Main Outcome and Measure: Hip fracture. Results: During follow-up, 2304 of 75 864 women had a hip fracture. Among the women with hip fractures, the median (range) age at hip fracture was 75.8 (46.7-93.0) years and the mean (SD) body mass index (calculated as weight in kilograms divided by height in meters squared) was 24.3 (4.6). Median (interquartile range) cumulative average intakes of total vitamins B6 and B12 were 3.6 (4.8) mg/d and 12.1 (11.7) µg/d, respectively. Both vitamin B6 (RR, 1.29; 95% CI, 1.04-1.59 for an intake of ≥35 vs <2 mg/d; P = .06 for linear trend) and vitamin B12 (RR, 1.25; 95% CI, 0.98-1.58 for an intake of ≥30 vs <5 µg/d; P = .02 for linear trend) were associated with increased fracture risk. Risk was highest in women with a combined high intake of both vitamins (B6 ≥35 mg/d and B12 ≥20 µg/d), exhibiting an almost 50% increased risk of hip fracture (RR, 1.47; 95% CI, 1.15-1.89) compared with women with a low intake of both vitamins (B6 <2 mg/d and B12 <10 µg/d). Conclusions and Relevance: In this cohort study, a combined high intake of vitamins B6 and B12 was associated with an increased risk of hip fracture. The intakes were far higher than the recommended dietary allowances. These findings add to previous studies suggesting that vitamin supplements should be used cautiously because adverse effects can occur.

Effect of Vitamin D on Thyroid Autoimmunity: A Randomized, Double-Blind, Controlled Trial Among Ethnic Minorities.

CONTEXT: Autoimmune thyroid disorders have been linked to vitamin D deficiency, but an effect of vitamin D supplementation is not established. OBJECTIVE: Our objective was to test whether vitamin D compared with placebo could reduce thyroid autoantibodies. DESIGN: Predefined additional analyses from a randomized, double-blind, placebo-controlled trial. SETTING: The study was conducted in different community centers in Oslo, Norway. PARTICIPANTS: A total of 251 presumed healthy men and women, aged 18 to 50 years, with backgrounds from South Asia, the Middle East, and Africa were included. INTERVENTION: Daily supplementation with 25 µg (1000 IU) vitamin D3, 10 µg (400 IU) vitamin D3, or placebo for 16 weeks. OUTCOME MEASURE: Difference in preintervention and postintervention antithyroid peroxidase antibody (TPOAb) levels. Additional outcomes were differences in thyroid-stimulating hormone (TSH) and free fraction of thyroxine (fT4). RESULTS: There were no differences in change after 16 weeks on TPOAb (27 kU/L; 95% CI, -17 to 72; P = 0.23), TSH (-0.10 mU/L; 95% CI, -0.54 to 0.34; P = 0.65), or fT4 (0.09 pmol/L; 95% CI, -0.37 to 0.55; P = 0.70) between those receiving vitamin D supplementation or placebo. Mean serum 25(OH)D3 increased from 26 to 49 nmol/L in the combined supplementation group, but there was no change in the placebo group. CONCLUSION: Vitamin D3 supplementation, 25 µg or 10 µg, for 16 weeks compared with placebo did not affect TPOAb level in this randomized, double-blind study among participants with backgrounds from South Asia, the Middle East, and Africa who had low vitamin D levels at baseline.

Vitamin D supplementation and vitamin D status in children of immigrant background in Norway.

OBJECTIVE: Sufficient vitamin D status during infancy is important for child health and development. Several initiatives for improving vitamin D status among immigrant children have been implemented in Norway. The present study aimed to evaluate the vitamin D status and its determinants in children of immigrant background in Oslo. DESIGN: Cross-sectional study. SETTING: Child health clinics in Oslo. SUBJECTS: Healthy children with immigrant background (n 102) aged 9-16 months were recruited at the routine one-year check-up from two child health clinics with high proportions of immigrant clients. Blood samples were collected using the dried blood spot technique and analysed for serum 25-hydroxyvitamin D (s-25(OH)D) concentration using LC-MS/MS. RESULTS: Mean s-25(OH)D was 52·3 (sd 16·7) nmol/l, with only three children below 25 nmol/l and none below 12·5 nmol/l. There was no significant gender, ethnic or seasonal variation in s-25(OH)D. However, compared with breast-fed children, s-25(OH)D concentration was significantly higher among children who were about 1 year of age and not breast-fed. About 38 % of the children were anaemic, but there was no significant correlation between s-25(OH)D and Hb (Pearson correlation, r=0·1, P=0·33). CONCLUSIONS: Few children in the study had vitamin D deficiency, but about 47 % of the children in the study population were under the recommended s-25(OH)D sufficiency level of ≥50 nmol/l.

B Vitamins and Hip Fracture: Secondary Analyses and Extended Follow-Up of Two Large Randomized Controlled Trials.

Elevated plasma homocysteine levels are associated with increased risk of fractures in observational studies. However, it is unsettled whether homocysteine-lowering treatment affects fracture risk. The aim of this study was to investigate the effect of an intervention with B vitamins on the risk of hip fracture in a secondary analysis of combined data from two large randomized controlled trials originally designed to study cardiovascular diseases. Both trials had identical design, intervention, and primary objective. Based on a two-by-two factorial design, the intervention consisted of a daily capsule with either (1) folic acid (0.8 mg) plus vitamin B12 (0.4 mg) and vitamin B6 (40 mg); (2) folic acid (0.8 mg) plus vitamin B12 (0.4 mg); (3) vitamin B6 alone (40 mg); or (4) placebo. The participants were followed with respect to hip fracture during the trial or during an extended follow-up (from the trial start for each patient until the end of 2012). No statistically significant association was found between folic acid plus vitamin B12 treatment and the risk of hip fracture, neither during the trial (median 3.3 years; hazard ratio [HR] 0.87; 95% confidence interval [CI], 0.48 to 1.59) nor during the extended follow-up (median 11.1 years; HR 1.08; 95% CI, 0.84 to 1.40). Nor were there significant differences in the risk of hip fracture between groups receiving versus not receiving vitamin B6 during the trial (HR 1.42; 95% CI, 0.78 to 2.61). However, during the extended follow-up, those receiving vitamin B6 showed a significant 42% higher risk of hip fracture (HR 1.42; 95% CI, 1.09 to 1.83) compared to those not receiving vitamin B6 . In conclusion, treatment with folic acid plus vitamin B12 was not associated with the risk of hip fracture. Treatment with a high dose of vitamin B6 was associated with a slightly increased risk of hip fracture during the extended follow-up (in-trial plus post-trial follow-up). © 2017 American Society for Bone and Mineral Research.

Nutritional rickets in Norway: a nationwide register-based cohort study.

OBJECTIVES: Poor vitamin D status has been reported to be highly prevalent in many non-western immigrant groups living in Norway and other western countries. However, data on rickets are scarce, and the aim of the current study was to identify new cases of nutritional rickets in Norway in the period 2008-2012 among children under the age of 5 years. DESIGN: Register-based cohort study. SETTING: The Norwegian population from 2008 to 2012. PARTICIPANTS: Children with nutritional rickets under the age of 5 years. MAIN OUTCOME MEASURE: Nutritional rickets. Patients with ICD10 (International Statistical Classification of Diseases and Related Health Problems, 10th revision) diagnosis code E55.0 (active rickets) treated at all Norwegian hospitals were identified in the Norwegian Patient Registry. We were able to review 85% of the medical records for diagnosis confirmation. In addition, we identified patients with the diagnoses E55.9, E64.3 and E83.3 to identify individuals with rickets who had been given other diagnoses. RESULTS: Nutritional rickets was confirmed in 39 children aged 0-4 years with the diagnosis of E55.0. In addition, three patients with the diagnosis of unspecified vitamin D deficiency (E55.9) were classified as having nutritional rickets, giving a total of 42 patients. Mean age at diagnosis was 1.40 years (range 0.1-3.5 years), and 93% had a non-western immigrant background. The incidence rate of rickets was estimated to be 0.3 per 10 000 person-years in the total Norwegian child population under the age of 5 years and 3.1 per 10 000 person-years in those with an immigrant background from Asia or Africa. CONCLUSION: The number of children with nutritional rickets in Norway remained low in the period 2008-2012. Nearly all children had a non-western immigrant background.

Effect of vitamin D3 supplementation on iron status: a randomized, double-blind, placebo-controlled trial among ethnic minorities living in Norway.

BACKGROUND: Both vitamin D and iron deficiencies are widespread globally, and a relationship between these deficiencies has been suggested. However, there is a paucity of randomised controlled trials assessing the effect of vitamin D supplementation on iron status. PURPOSE: We aimed to investigate whether 16 weeks of daily vitamin D3 supplementation had an effect on serum ferritin, haemoglobin, serum iron and transferrin saturation. METHODS: Overall, 251 participants from South Asia, Middle East and Africa aged 18-50 years who were living in Norway were randomised to receive daily oral supplementation of 10 µg vitamin D3, 25 µg vitamin D3, or placebo for 16 weeks during the late winter. Blood samples from baseline and after 16 weeks were analysed for serum 25-hydroxyvitamin D (s-25(OH) D), serum ferritin, haemoglobin and serum iron. In total, 214 eligible participants completed the intervention (86 % of those randomised). Linear regression analysis were used to test the effect of vitamin D3 supplementation combined (10 or 25 µg) and separate doses 10 or 25 µg compared to placebo on change (T2-T1) in each outcome variable adjusted for baseline s-25(OH)D values. RESULTS: There was no difference in change in the levels of s-ferritin (1.9 µg/L, 95 % CI: -3.2, 7.0), haemoglobin (-0.02 g/dL, 95 % CI: -0.12, 0.09), s-iron (0.4 µg/L, 95 % CI: -0.5, 1.3) or transferrin saturation (0.7 %, 95 % CI: -0.6.1, 2.0) between those receiving vitamin D3 or those receiving placebo. Serum 25-hydroxyvitamin D increased from 29 nmol/L at baseline to 49 nmol/L after the intervention, with little change in the placebo group. CONCLUSIONS: In this population of healthy ethnic minorities from South Asia, the Middle East and Africa who had low vitamin D status, 16 weeks of daily supplementation with 10 or 25 µg of vitamin D3 did not significantly affect the haemoglobin levels or other markers of iron status.

No increase in risk of hip fracture at high serum retinol concentrations in community-dwelling older Norwegians: the Norwegian Epidemiologic Osteoporosis Studies.

BACKGROUND: Norway has the highest hip fracture rates worldwide and a relatively high vitamin A intake. Increased fracture risk at high intakes and serum concentrations of retinol (s-retinol) have been observed in epidemiologic studies. OBJECTIVE: We aimed to study the association between s-retinol and hip fracture and whether high s-retinol may counteract a preventive effect of vitamin D. DESIGN: We conducted the largest prospective analysis of serum retinol and hip fracture to date in 21,774 men and women aged 65-79 y (mean age: 72 y) who attended 4 community-based health studies during 1994-2001. Incident hip fractures occurring up to 10.7 y after baseline were retrieved from electronic hospital discharge registers. Retinol determined by high-pressure liquid chromatography with ultraviolet detection in stored serum was available in 1154 incident hip fracture cases with valid body mass index (BMI) data and in a subcohort defined as a sex-stratified random sample (n = 1418). Cox proportional hazards regression weighted according to the stratified case-cohort design was performed. RESULTS: There was a modest increased risk of hip fracture in the lowest compared with the middle quintile of s-retinol (HR: 1.41; 95% CI: 1.09, 1.82) adjusted for sex and study center. The association was attenuated after adjustment for BMI and serum concentrations of α-tocopherol (HR: 1.16; 95% CI: 0.88, 1.51). We found no increased risk in the upper compared with the middle quintile. No significant interaction between serum concentrations of 25-hydroxyvitamin D and s-retinol on hip fracture was observed (P = 0.68). CONCLUSIONS: We found no evidence of an adverse effect of high serum retinol on hip fracture or any interaction between retinol and 25-hydroxyvitamin D. If anything, there tended to be an increased risk at low retinol concentrations, which was attenuated after control for confounders. We propose that cod liver oil, a commonly used food supplement in Norway, should not be discouraged as a natural source of vitamin D for fracture prevention.

Effect of vitamin D3-supplementation on bone markers (serum P1NP and CTX): A randomized, double blinded, placebo controlled trial among healthy immigrants living in Norway.

OBJECTIVE: Vitamin D is essential for the maintenance of calcium homeostasis and bone mineralization; and low serum 25-hydroxyvitamin D (s-25-(OH)D) concentrations are associated with increased bone turnover. However, there is a lack of randomized controlled trials that have investigated the effect of vitamin D treatment on bone turnover in immigrant populations. We aimed to investigate the effect of 16-week daily vitamin D3 supplementation on bone formation marker serum procollagen type 1 amino-terminal propeptide (P1NP) and bone resorption marker C-terminal crosslinked telopeptide of type I collagen (CTX). DESIGN: Double-blind, randomized, placebo-controlled trial. SETTING: Immigrant community centers in Oslo, Norway. PARTICIPANTS: 251 healthy adults aged 18-50 years with a non-Western immigrant background were recruited. INTERVENTION: 16 weeks of daily oral supplementation with either 10 µg vitamin D3, 25 µg vitamin D3, or placebo. MAIN OUTCOME MEASURES: Difference in change during the 16-week intervention between the intervention groups combined (10 or 25 µg of vitamin D3/day) and placebo, in serum P1NP and serum CTX. RESULTS: A total of 214 (85%) participants completed the study. S-25-(OH)D increased from 29 nmol/L at baseline to 49 nmol/L in the intervention group with no significant change in the placebo group. However, there was no difference in change of serum P1NP (mean difference: - 1.2 µg/L (95% CI: - 5.4, 2.9, P = 0.6)) and serum CTX (mean difference: - 0.005 µg/L (95% CI: - 0.03, 0.02, P = 0.7)) between those receiving vitamin D3 supplementation compared with placebo. The plasma PTH had decreased by a mean of - 1.97 pmol/L (95% CI: - 2.7, - 1.3, P < 0.0001) in the vitamin D3 group compared to placebo. CONCLUSIONS: Supplementation with 10 or 25 µg oral vitamin D3 during winter and spring for 16 weeks did not significantly affect serum P1NP and serum CTX, despite increasing s-25(OH)D and decreasing PTH in a healthy immigrant population with low baseline vitamin D status. Trial registration number: NCT01263288.

Effect of vitamin D3 supplementation on glycated hemoglobin (HbA1c), fructosamine, serum lipids, and body mass index: a randomized, double-blinded, placebo-controlled trial among healthy immigrants living in Norway.

OBJECTIVE: Despite the suggested role of vitamin D in the prevention of diabetes and cardiovascular disease or its risk factors, the evidence is not consistent and there is a paucity of randomized controlled trials in this field. We aimed to investigate the effect of 16-week daily vitamin D3 supplementation on glycated hemoglobin (HbA1c), fructosamine, body mass index (BMI), and serum lipids. DESIGN: Double-blind, randomized, placebo-controlled trial. SETTING: Immigrant community centers in Oslo, Norway. PARTICIPANTS: 251 healthy adults aged 18-50 years with a non-Western immigrant background. All participants performed the baseline test and 215 (86%) returned to the follow-up test. INTERVENTION: 16 weeks of daily oral supplementation with either 10 µg vitamin D3, 25 µg vitamin D3, or placebo. MAIN OUTCOME MEASURES: Difference in absolute change during the 16-week intervention between the intervention groups combined (10 or 25 µg of vitamin D3/day) and placebo, in HbA1c, fructosamine, serum lipids (total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides), and BMI. RESULTS: A total of 215 (86%) participants completed the study. Serum 25-hydroxyvitamin D increased from 29 nmol/L at baseline to 49 nmol/L after intervention, with little change in the placebo group. However, there was no difference in change of HbA1c between those receiving vitamin D3 compared with placebo (mean difference: 0.01% (95% CI -0.04 to 0.06, p=0.7)). Neither did the vitamin D3 supplementation have any effect on the other end points: fructosamine, serum lipids, and BMI. CONCLUSIONS: 16-week vitamin D3 supplementation to healthy immigrants from South Asia, the Middle East, or Africa and now living in Norway with low vitamin D status did not improve HbA1c, fructosamine, lipid profiles, or BMI. An updated meta-analysis of similar published trials showed that our results were generally consistent with those of other studies. TRIAL REGISTRATION NUMBER: NCT01263288.

Effect of vitamin D on musculoskeletal pain and headache: A randomized, double-blind, placebo-controlled trial among adult ethnic minorities in Norway.

Immigrants from South Asia, the Middle East, and Africa living in Northern Europe frequently have low vitamin D levels and more pain compared to the native Western population. The aim of this study was to examine whether daily vitamin D3 (25 µg/d or 10 µg/d) supplementation for 16 weeks would improve musculoskeletal pain or headache compared to placebo. This randomized, double-blind, placebo-controlled, parallel-group trial recruited 251 participants aged 18 to 50 years, and 215 (86%) attended the follow-up visit. The pain measures were occurrence, anatomical localization, and degree of musculoskeletal pain, as measured by visual analogue scale (VAS) score during the past 2 weeks. Headache was measured with VAS and the Headache Impact Test (HIT-6) questionnaire. At baseline, females reported more pain sites (4.7) than males (3.4), and only 7% reported no pain in the past 2 weeks. During the past 4 weeks, 63% reported headache with a high mean HIT-6 score of 60 (SD 7). At follow-up, vitamin D level, measured as serum 25(OH)D3, increased from 27 nmol/L to 52 nmol/L and from 27 nmol/L to 43 nmol/L in the 25-µg and 10-µg supplementation groups, respectively, whereas serum 25(OH)D3 did not change in the placebo group. Pain scores and headache scores were improved at follow-up compared with baseline. The use of vitamin D supplements, however, showed no significant effect on the occurrence, anatomical localization, and degree of pain or headache compared to placebo.

Does vitamin D improve muscle strength in adults? A randomized, double-blind, placebo-controlled trial among ethnic minorities in Norway.

CONTEXT: The effect of vitamin D on muscle strength in adults is not established. OBJECTIVE: Our objective was to test whether vitamin D supplementation increases muscle strength and power compared with placebo. DESIGN: We conducted a randomized, double-blind, placebo-controlled trial. SETTING: The setting was immigrants' activity centers. PARTICIPANTS: Two hundred fifty-one healthy adult males and females aged 18-50 years with non-Western immigrant background performed the baseline test and 86% returned to the follow-up test. INTERVENTIONS: Sixteen weeks of daily supplementation with 25 µg (1000 IU) vitamin D3, 10 µg (400 IU) vitamin D3, or placebo. MAIN OUTCOME MEASURES: Difference in jump height between pre- and postintervention. Secondary outcomes were differences in handgrip strength and chair-rising test. RESULTS: Percentage change in jump height did not differ between those receiving vitamin D (25 or 10 µg vitamin D3) and those receiving placebo (mean difference -1.4%, 95% confidence interval: -4.9% to 2.2%, P=.44). No significant effect was detected in the subgroup randomized to 25 µg vitamin D or in other preplanned subgroup analyses nor were there any significant differences in handgrip strength or the chair-rising test. Mean serum 25-hydroxyvitamin D3 concentration increased from 27 to 52 nmol/L and from 27 to 43 nmol/L in the 25 and 10 µg supplementation groups, respectively, whereas serum 25-hydroxyvitamin D3 did not change in the placebo group. CONCLUSIONS: Daily supplementation with 25 or 10 µg vitamin D3 for 16 weeks did not improve muscle strength or power measured by the jump test, handgrip test, or chair-rising test in this population with low baseline vitamin D status.

Vitamin D - a systematic literature review for the 5th edition of the Nordic Nutrition Recommendations.

BACKGROUND: The present literature review is part of the NNR5 project with the aim of reviewing and updating the scientific basis of the 4th edition of the Nordic Nutrition Recommendations (NNR) issued in 2004. OBJECTIVES: The overall aim was to review recent scientific data on the requirements and health effects of vitamin D and to report it to the NNR5 Working Group, who is responsible for updating the current dietary reference values valid in the Nordic countries. METHODS: The electronic databases MEDLINE and Swemed were searched. We formulated eight questions which were used for the search. The search terms related to vitamin D status and intake and different health outcomes as well as to the effect of different vitamin D sources on vitamin D status. The search was done in two batches, the first covering January 2000-March 2010 and the second March 2009-February 2011. In the first search, we focused only on systematic literature reviews (SLRs) and in the second on SLRs and randomized control trials (RCTs) published after March 2009. Furthermore, we used snowballing for SLRs and IRCTs published between February 2011 and May 2012. The abstracts as well as the selected full-text papers were evaluated in pairs. RESULTS: We found 1,706 studies in the two searches of which 28 studies were included in our review. We found 7 more by snowballing, thus 35 papers were included in total. Of these studies, 31 were SLRs and 4 were RCTs. The SLRs were generally of good or fair quality, whereas that of the included studies varied from good to poor. The heterogeneity of the studies included in the SLRs was large which made it difficult to interpret the results and provide single summary statements. One factor increasing the heterogeneity is the large variation in the assays used for assessing 25-hydroxyvitamin D concentration [25(OH)D], the marker of vitamin D status. The SLRs we have reviewed conclude that the evidence for a protective effect of vitamin D is only conclusive concerning bone health, total mortality and the risk of falling. Moreover, the effect was often only seen in persons with low basal 25(OH)D concentrations. In addition, most intervention studies leading to these conclusions report that intervention with vitamin D combined with calcium and not vitamin D alone gives these benefits. It was difficult to establish an optimal 25(OH)D concentration or vitamin D intake based on the SLRs, but there are evidence that a concentration of ≥50 nmol/l could be optimal. The dose-response studies relating vitamin D intake (fortification and supplementation) to S-25(OH)D suggested that an intake of 1-2.5 µg/day will increase the serum concentration by 1-2 nmol/l but this is dependent on the basal concentration with a response being greater when the basal concentration is low. CONCLUSION: Data show that a S-25(OH)D concentration of 50 nmol/l would reflect a sufficient vitamin D status. Results from this review support that the recommendation in NNR 2004 needs to be re-evaluated and increased for all age groups beyond 2 years of age. We refer to the total intake from food as well as supplements, given minimal sun exposure. Limited sunshine, however, does not reflect the situation for the majority of the Nordic population in the summertime. It should also be emphasized that there are large differences in results depending on assay methods and laboratories measuring 25(OH)D, adding to the uncertainty of determining an appropriate target concentration. Moreover, the dose-response of vitamin D on serum 25(OH)D-concentrations is not well established and is dependent on the basal concentrations, sunshine exposure and dietary intake. We advise that these uncertainties should be taken into account when setting the final Nordic recommendations.

A pooled analysis of vitamin D dose requirements for fracture prevention.

BACKGROUND: The results of meta-analyses examining the relationship between vitamin D supplementation and fracture reduction have been inconsistent. METHODS: We pooled participant-level data from 11 double-blind, randomized, controlled trials of oral vitamin D supplementation (daily, weekly, or every 4 months), with or without calcium, as compared with placebo or calcium alone in persons 65 years of age or older. Primary end points were the incidence of hip and any nonvertebral fractures according to Cox regression analyses, with adjustment for age group, sex, type of dwelling, and study. Our primary aim was to compare data from quartiles of actual intake of vitamin D (including each individual participant's adherence to the treatment and supplement use outside the study protocol) in the treatment groups of all trials with data from the control groups. RESULTS: We included 31,022 persons (mean age, 76 years; 91% women) with 1111 incident hip fractures and 3770 nonvertebral fractures. Participants who were randomly assigned to receive vitamin D, as compared with those assigned to control groups, had a nonsignificant 10% reduction in the risk of hip fracture (hazard ratio, 0.90; 95% confidence interval [CI], 0.80 to 1.01) and a 7% reduction in the risk of nonvertebral fracture (hazard ratio, 0.93; 95% CI, 0.87 to 0.99). By quartiles of actual intake, reduction in the risk of fracture was shown only at the highest intake level (median, 800 IU daily; range, 792 to 2000), with a 30% reduction in the risk of hip fracture (hazard ratio, 0.70; 95% CI, 0.58 to 0.86) and a 14% reduction in the risk of any nonvertebral fracture (hazard ratio, 0.86; 95% CI, 0.76 to 0.96). Benefits at the highest level of vitamin D intake were fairly consistent across subgroups defined by age group, type of dwelling, baseline 25-hydroxyvitamin D level, and additional calcium intake. CONCLUSIONS: High-dose vitamin D supplementation (≥800 IU daily) was somewhat favorable in the prevention of hip fracture and any nonvertebral fracture in persons 65 years of age or older. (Funded by the Swiss National Foundations and others.).