Suvi T. Itkonen

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.

The positive impact of general vitamin D food fortification policy on vitamin D status in a representative adult Finnish population: evidence from an 11-y follow-up based on standardized 25-hydroxyvitamin D data

Background: A systematic vitamin D fortification of fluid milk products and fat spreads was started in 2003 in Finland to improve vitamin D status. Objective: We investigated the effects of the vitamin D fortification policy on vitamin D status in Finland between 2000 and 2011.Design: Serum 25-hydroxyvitamin D [S-25(OH)D] concentrations of a nationally representative sample comprising 6134 and 4051 adults aged ≥30 y from the Health 2000 and Health 2011 surveys, respectively, were standardized according to the Vitamin D Standardization Program with the use of liquid chromatography-tandem mass spectrometry. Linear and logistic regression models were used to assess the change in S-25(OH)D concentrations.Results: Between 2000 and 2011, the mean S-25(OH)D increased from 48 nmol/L (95% CI: 47, 48 nmol/L) to 65 nmol/L (95% CI: 65, 66 nmol/L) (P < 0.001). The prevalence of vitamin D supplement users increased from 11% to 41% (P < 0.001). When analyzing the effect of fortification of fluid milk products, we focused on supplement nonusers. The mean increase in S-25(OH)D in daily fluid milk consumers (n = 1017) among supplement nonusers was 20 nmol/L (95% CI: 19, 21 nmol/L), which was 6 nmol/L higher than nonconsumers (n = 229) (14 nmol/L; 95% CI: 12, 16 nmol/L) (P < 0.001). In total, 91% of nonusers who consumed fluid milk products, fat spreads, and fish based on Finnish nutrition recommendations reached S-25(OH)D concentrations >50 nmol/L in 2011.Conclusions: The vitamin D status of the Finnish adult population has improved considerably during the time period studied. The increase is mainly explained by food fortification, especially of fluid milk products, and augmented vitamin D supplement use. Other factors, such as the difference in the ultraviolet radiation index between 2000 and 2011, may partly explain the results. When consuming vitamin D sources based on the nutritional recommendations, vitamin D status is sufficient [S-25(OH)D ≥50 nmol/L], and supplementation is generally not needed.

Associations among total and food additive phosphorus intake and carotid intima-media thickness – a cross-sectional study in a middle-aged population in Southern Finland

BackgroundDietary phosphorus (P) intake in Western countries is 2- to 3-fold higher than recommended, and phosphate is widely used as a food additive in eg. cola beverages and processed meat products. Elevated serum phosphate concentrations have been associated with cardiovascular disease (CVD) risk factors and CVD itself in several studies in patients with renal dysfunction and in a few studies in the general population. Carotid intima-media thickness (IMT) is a CVD risk factor, thus the aim of the study was to determine if an association between dietary P, especially food additive phosphate (FAP), intake, and IMT exists.MethodsAssociations among total phosphorus (TP) and FAP intake and carotid IMT were investigated in a cross-sectional study of 37- to 47-year-old females (n = 370) and males (n = 176) in Finland. Associations among TP intake, FAP intake, and IMT were tested by analysis of covariance (ANCOVA) in quintiles (TP) and sextiles (FAP) using sex, age, low-density/high-density lipoprotein cholesterol ratio, smoking status, and IMT sonographer as covariates.ResultsNo significant associations were present between TP or FAP intake and IMT (p > 0.05, ANCOVA), but in between-group comparisons some differences were found indicating higher IMT among subjects with higher P intake. When testing for a significant linear trend with contrast analysis, a positive trend was observed between energy-adjusted TP intake and IMT among all subjects (p = 0.039), and among females a tendency for a trend existed (p = 0.067). Among all subjects, a significant positive linear trend was also present between FAP intake and IMT (p = 0.022); this trend was also seen in females (p = 0.045). In males, no significant associations or trends were noted between TP or FAP intake and IMT (p > 0.05).ConclusionsOur results indicate that a significant linear trend exists between energy-adjusted TP intake and FAP intake, and IMT among all subjects. Based on these results, high dietary P intake should be further investigated due to its potential association with adverse cardiovascular health effects in the general population.

Food fortification as a means to increase vitamin D intake.

Soininen et al. recently reported about vitamin D intake, serum 25-hydroxyvitamin D (25(OH)D) concentration, determinants of 25(OH)D and risk factors for serum 25(OH)D < 50 nmol/l in Finnish children. The authors draw conclusions that 80% of the children did not meet the current recommendation for vitamin D intake from food and supplements and 20% had serum 25(OH)D concentrations <50 nmol/l. This may cause concern about the adequacy of the vitamin D status at northern latitudes. The study and its results are potentially interesting, but the authors have misled the reader to some extent by not stressing that the data collection was carried out between the years 2007–2009. At the time of the study, a decree on general vitamin D fortification had been adopted in 2002. It stated that the vitamin D levels for fluid milk products (with exception of organic products) and respective lactose-free milk and soyaand cereal-based drinks should be 0·5 μg/100 g and for spreadable fats 10 μg/100 g. These levels were, however, much lower than the present ones. Studies and reports about the efficacy of that fortification level on vitamin D intake and 25(OH)D concentrations in different population groups in Finland were already carried out in 2000s. The main message of these studies was that, although the 25(OH)D concentrations and vitamin D intake mainly tended to increase because of the fortification, a significant percentage of the subjects remained with inadequate vitamin D status in all age groups. From that point of view, the study of Soininen et al. does not provide any new data, as this has already been reported in children and adolescents as well. The results of those earlier studies from the 2000s led to the discussion on new recommendations on fortification levels in 2010. In April 2010, The National Nutrition Council launched a new recommendation that the fortification levels should be doubled to 1·0 μg/100 g for all fluid milks and respective products and to 20 μg/100 g for spreadable fats. These recommendations were based on simulations on the effect of fortification. Especially the dairy industry responded immediately and almost all fluid milk products were fortified, with the exception of ecological products. Soininen et al. discuss this, but they still seem to hide this fact from their conclusions. They do not point out that nowadays, since 2010, the range of vitamin D content in dairy products in Finland has increased because of the new fortification policy. In addition, a wide selection of vitamin D-fortified products, not only fluid milk and spreads, are currently on the market. Some fluid milk products contain even 2 μg vitamin D/100 g and, for example, a number of yogurts may have the same amount. Thus, it is probable that this later fortification has had a positive impact on the vitamin D intake and status among Finnish children, especially among those who consume fluid milk products. This has been reported in adults, whose mean vitamin D intake now is about 10 μg, and close to 40–50% of it comes from fortified milk products. Moreover, the supplementation recommendations for children and adolescents have been increased and extended to cover the whole year since 2011. Consequently, the conclusion of the authors that many children need more vitamin D from food or supplements to reach sufficient serum 25(OH)D concentrations in northern latitudes is drawn from outdated data, which is a serious flaw in the interpretation of it. These actions have already been taken in 2010, and what we need is new data from the time after that. The Physical Activity and Nutrition in Children (PANIC) study is an ongoing trial, and the second 2-year follow-up was carried out in 2009–2011. Thus, we wonder why the authors have not presented new data after the year 2010 fortification, because they seem to have it already. Further, the results of the Soininen et al. study have a significant and serious methodological problem, which subsequently weakens the conclusions regarding vitamin D status. The analytical assay used for 25(OH)D, the LIAISON 25OHD Total assay (DiaSorin Inc.), has been shown to have a negative bias in external analyses, for example, DEQAS (Vitamin D External Quality Assessment Scheme, deqas.kpmd.co.uk). Thus, the 25(OH)D data are flawed and make subsequent analyses worthless. This is a common problem with 25(OH)D, which causes bias in the result assays. This is extremely important to understand when vitamin D status cut-off values are reported and used. During the last few years, the Vitamin D Standardization Programme (VDSP) has been initiated by National Institute of Health, with the aim to standardise commercial assays against two reference laboratories using National Institute of Standards and Technology reference material. An important focus of the VDSP is on standardising the measurement of 25(OH)D in national health and nutrition surveys around the world by recalibrating 25(OH)D values from past surveys. As the assay used is of such importance in reporting vitamin D status in populations, it is astonishing that the authors do not even mention any external quality control system. British Journal of Nutrition (2016), 115, 2075–2076

Development and validation of an interview-administered FFQ for assessment of vitamin D and calcium intakes in Finnish women

Increased vitamin D fortification of dairy products has increased the supply of vitamin D-containing products with different vitamin D contents on the market in Finland. The authors developed a ninety-eight-item FFQ with eight food groups and with a question on supplementation to assess dietary and supplemental vitamin D and Ca intakes in Finnish women (60ºN). The FFQ was validated in subgroups with different habitual vitamin D supplement use (0-57·5 µg/d) against the biomarker serum 25-hydroxyvitamin D (S-25(OH)D) and against 3-d food records (FR) (n 29-67). Median total vitamin D intake among participants was 9·4 (range 1·6-30·5) µg/d. Spearmans correlations for vitamin D and Ca ranged from 0·28 (P 0·146, FFQ v. S-25(OH)D, persons not using supplements) to 0·75 (P<0·001, FFQ v. FR, supplement use included). The correlations between the FFQ and S-25(OH)D concentrations improved within increasing supplement intake. The Bland-Altman analysis showed wide limits of agreement between FFQ and FR: for vitamin D between -7·8 and 8·8 µg/d and for Ca between -938 and 934 mg/d, with mean differences being 0·5 µg/d and 2 mg/d, respectively. The triads method was used to calculate the validity coefficients of the FFQ for vitamin D, resulting in a mean of 1·00 (95 % CI 0·59, 1·00) and a range from 0·33 to 1·00. The perceived variation in the estimates could have been avoided with a longer FR period and larger number of participants. The results are comparable with earlier studies, and the FFQ provides a reasonable estimation of vitamin D and Ca intakes.

Rationale and Plan for Vitamin D Food Fortification: A Review and Guidance Paper

Vitamin D deficiency can lead to musculoskeletal diseases such as rickets and osteomalacia, but vitamin D supplementation may also prevent extraskeletal diseases such as respiratory tract infections, asthma exacerbations, pregnancy complications and premature deaths. Vitamin D has a unique metabolism as it is mainly obtained through synthesis in the skin under the influence of sunlight (i.e., ultraviolet-B radiation) whereas intake by nutrition traditionally plays a relatively minor role. Dietary guidelines for vitamin D are based on a consensus that serum 25-hydroxyvitamin D (25[OH]D) concentrations are used to assess vitamin D status, with the recommended target concentrations ranging from ≥25 to ≥50 nmol/L (≥10–≥20 ng/mL), corresponding to a daily vitamin D intake of 10 to 20 μg (400–800 international units). Most populations fail to meet these recommended dietary vitamin D requirements. In Europe, 25(OH)D concentrations <30 nmol/L (12 ng/mL) and <50 nmol/L (20 ng/mL) are present in 13.0 and 40.4% of the general population, respectively. This substantial gap between officially recommended dietary reference intakes for vitamin D and the high prevalence of vitamin D deficiency in the general population requires action from health authorities. Promotion of a healthier lifestyle with more outdoor activities and optimal nutrition are definitely warranted but will not erase vitamin D deficiency and must, in the case of sunlight exposure, be well balanced with regard to potential adverse effects such as skin cancer. Intake of vitamin D supplements is limited by relatively poor adherence (in particular in individuals with low-socioeconomic status) and potential for overdosing. Systematic vitamin D food fortification is, however, an effective approach to improve vitamin D status in the general population, and this has already been introduced by countries such as the US, Canada, India, and Finland. Recent advances in our knowledge on the safety of vitamin D treatment, the dose-response relationship of vitamin D intake and 25(OH)D levels, as well as data on the effectiveness of vitamin D fortification in countries such as Finland provide a solid basis to introduce and modify vitamin D food fortification in order to improve public health with this likewise cost-effective approach.

Low free 25-hydroxyvitamin D and high vitamin D binding protein and parathyroid hormone in obese Caucasians. A complex association with bone?

Background Studies have shown altered vitamin D metabolism in obesity. We assessed differences between obese and normal-weight subjects in total, free, and bioavailable 25-hydroxyvitamin D (25(OH)D, 25(OH)DFree, and 25(OH)DBio, respectively), vitamin D binding protein (DBP), parathyroid hormone (PTH) and bone traits. Methods 595 37-47-year-old healthy Finnish men and women stratified by BMI were examined in this cross-sectional study. Background characteristic and intakes of vitamin D and calcium were collected. The concentrations of 25(OH)D, PTH, DBP, albumin and bone turnover markers were determined from blood. 25(OH)DFree and 25(OH)DBio were calculated. pQCT was performed at radius and tibia. Results Mean±SE (ANCOVA) 25(OH)DFree (10.8±0.6 vs 12.9±0.4 nmol/L; P = 0.008) and 25(OH)DBio (4.1±0.3 vs 5.1±0.1 nmol/L; P = 0.003) were lower in obese than in normal-weight women. In men, 25(OH)D (48.0±2.4 vs 56.4±2.0 nmol/L, P = 0.003), 25(OH)DFree (10.3±0.7 vs 12.5±0.6 pmol/L; P = 0.044) and 25(OH)DBio (4.2±0.3 vs 5.1±0.2 nmol/L; P = 0.032) were lower in obese. Similarly in all subjects, 25(OH)D, 25(OH)DFree and 25(OH)DBio were lower in obese (P<0.001). DBP (399±12 vs 356±7mg/L, P = 0.008) and PTH (62.2±3.0 vs 53.3±1.9 ng/L; P = 0.045) were higher in obese than in normal-weight women. In all subjects, PTH and DBP were higher in obese (P = 0.047and P = 0.004, respectively). In obese women, 25(OH)D was negatively associated with distal radius trabecular density (R2 = 0.089, P = 0.009) and tibial shaft cortical strength index (CSI) (R2 = 0.146, P = 0.004). 25(OH)DFree was negatively associated with distal radius CSI (R2 = 0.070, P = 0.049), radial shaft cortical density (CorD) (R2 = 0.050, P = 0.045), and tibial shaft CSI (R2 = 0.113, P = 0.012). 25(OH)DBio was negatively associated with distal radius CSI (R2 = 0.072, P = 0.045), radial shaft CorD (R2 = 0.059, P = 0.032), and tibial shaft CSI (R2 = 0.093, P = 0.024). Conclusions The associations between BMI and 25(OH)D, 25(OH)DFree, and 25(OH)DBio, DBP, and PTH suggest that obese subjects may differ from normal-weight subjects in vitamin D metabolism. BMI associated positively with trabecular bone traits and CSI in our study, and slightly negatively with cortical bone traits. Surprisingly, there was a negative association of free and bioavailable 25(OH)D and some of the bone traits in obese women.

Consumption of healthy foods and associated socio-demographic factors among Russian, Somali and Kurdish immigrants in Finland

Aims: We evaluated the consumption of healthy foods among Russian, Somali and Kurdish immigrants in Finland, and examined the relationship between socio-demographic factors and food consumption. Methods: We used data from the Migrant Health and Wellbeing Study (Maamu), a population-based health interview and examination survey in six different municipalities in Finland between 2010 and 2012. Altogether, 635 men and 737 women, aged 18–64 years, of Russian (n = 527), Somali (n = 337) and Kurdish (n = 508) origin were included. The important socio-demographic determinants of healthy food consumption – sex, age, education, place of residence and household size – were assessed by logistic regression. Results: Based on the consumption frequencies of recommended healthy foods – fruits, berries, vegetables, fish and rye bread – immigrants of Russian origin had higher consumption of healthy foods than their peers of Kurdish and Somali origin. Low consumption of fresh vegetables, fruits and berries was found among Somali immigrants. Sex and age were the most important determinants of healthy food consumption, as women and older age groups had diets closer to the national nutrition recommendations. High educational level was also positively associated with healthy food consumption. Conclusions: We found ethnic differences in the consumption of healthy foods among the immigrant groups of Russian, Somali and Kurdish origin in Finland. Socio-demographic factors, especially age, sex and education, seem to also play an important role in immigrants’ food consumption. Further studies examining the consumption of fruits, berries and fresh vegetables among Somali immigrants in Finland are needed.

Letter to the Editor Re: McClure et al. Nutrients 2017, 9, 95

n/a.

Serum parathyroid hormone is related to genetic variation in vitamin D binding protein with respect to total, free, and bioavailable 25-hydroxyvitamin D in middle-aged Caucasians – a cross-sectional study

BackgroundVitamin D binding protein (DBP) binds vitamin D and its plasma metabolites, including 25-hydroxyvitamin D (25(OH)D), in the circulation. Only a small fraction circulates free (free 25(OH)D). Genetic variation of the GC gene, encoding DBP, has been associated with 25(OH)D concentrations. The roles of DBP and free 25(OH)D concentrations in the biological actions of vitamin D remain unclear.MethodsWe assessed the relationship between GC gene variants rs4588, rs7041, and rs705124, and serum total 25(OH)D, free and bioavailable 25(OH)D, and serum DBP and parathyroid hormone (PTH) concentrations in 622 Caucasian females (421) and males (201) aged 37–47 years. Concentrations of 25(OH)D, DBP, and PTH were measured from fasting blood samples. Dietary intakes of vitamin D and Ca were evaluated using 1-month food use frequency data, which were collected by a validated Food Frequency Questionnaire on vitamin D and calcium intakes. The subjects filled in the questionnaire covering overall health, medications, use of vitamin D and calcium supplements, and holidays in sunny locations. Three SNPs in the GC gene were genotyped: rs4588, rs7041, and rs705124. The SNPs rs4588 and rs7041 combine to form six common diplotypes. Free and bioavailable 25(OH)D were calculated by using specific binding coefficients. Differences among the diplo- and haplotypes of the GC gene in measures of 25(OH)D, DBP, and PTH were tested by analysis of covariance (ANCOVA) using appropriate covariates.ResultsWe found significant variation among the SNPs rs4588 and rs7041 variants in DBP, total, free, and bioavailable 25(OH)D, and PTH. DBP concentration was lowest in genotype GC2/2 in both diplotypes and haplotypes (p = 0.039 and 0.039, respectively). The lowest 25(OH)D concentrations were found in diplotype variants GC1S/2, GC1S/F, and GC2/2 (p = 0.033), but free and bioavailable 25(OH)D concentrations were highest in the GC2/2 variant after corrected with a genotype-specific binding coefficient (p < 0.001 in both groups). Surprisingly, one of the lowest PTH concentrations was also present in variant GC2/2 in diplotypes (p = 0.040 of the overall ANCOVA analysis of PTH). Among SNP rs705124, there was a difference only in PTH concentrations (p = 0.013).ConclusionsOur findings indicate that genetic variation of the DBP coding gene, and free concentrations of 25(OH)D may be relevant when vitamin D status, metabolism, and action are investigated.