Abstract There is a need for food-based solutions for preventing vitamin D deficiency. Vitamin D 3 (D 3 ) is mainly used in fortified food products, although the production of vitamin D 2 (D 2 ) is more cost-effective, and thus may hold opportunities. We investigated the bioavailability of D 2 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 D 2 or D 3 /d; D 2 supplement and regular bread=25 µg D 2 /d; D 3 supplement and regular bread=25 µg D 3 /d; and placebo pill and D 2 -biofortified bread=25 µg D 2 /d). Serum 25-hydroxyvitamin D 2 (S-25(OH)D 2 ) and serum 25-hydroxyvitamin D 3 (S-25(OH)D 3 ) concentrations were measured at baseline, midpoint and end point. The mean baseline total serum 25-hydroxyvitamin D (S-25(OH)D=S-25(OH)D 2 +S-25(OH)D 3 ) concentration was 65·1 nmol/l. In repeated-measures ANCOVA (adjusted for baseline S-25(OH)D as total/D 2 /D 3 ), D 2 -bread did not affect total S-25(OH)D ( P =0·707) or S-25(OH)D 3 ( P =0·490), but increased S-25(OH)D 2 compared with placebo ( P <0·001). However, the D 2 supplement was more effective than bread in increasing S-25(OH)D 2 ( P <0·001). Both D 2 and D 3 supplementation increased total S-25(OH)D compared with placebo ( P =0·030 and P =0·001, respectively), but D 2 supplementation resulted in lower S-25(OH)D 3 ( P <0·001). Thus, D 2 from UV-irradiated yeast in bread was not bioavailable in humans. Our results support the evidence that D 2 is less potent in increasing total S-25(OH)D concentrations than D 3 , also indicating a decrease in the percentage contribution of S-25(OH)D 3 to the total vitamin D pool.
Secondary hyperparathyroidism (SHPT) is one of the outcomes of vitamin D deficiency that negatively affects bone metabolism. We studied the ethnic differences in vitamin D status in Finland and its effect on serum intact parathyroid hormone (S-iPTH) concentration and bone traits. The study was done in the Helsinki area (60°N) during January-February 2008. A total of 143 healthy women (20-48 years of age) from two groups of immigrant women (Bangladeshi, n 34 and Somali, n 48), and a group of ethnic Finnish women (n 61) were studied in a cross-sectional setting. Serum concentrations of 25-hydroxyvitamin D (S-25OHD) and S-iPTH were measured. Peripheral quantitative computed tomography measurements were taken at 4 and 66 % of the forearm length. In all groups, the distribution of S-25OHD was shifted towards the lower limit of the normal range. A high prevalence of vitamin D insufficiency (S-25OHD < 50 nmol/l) was observed (89·6 %) in the Somali group. The prevalence of SHPT (S-iPTH>65 ng/l) was higher (79·1 %) in Somali women than in Finnish women (16 %). There was a significant association between S-25OHD and S-iPTH (r - 0·49, P < 0·001). Ethnicity and S-25OHD together explained 30 % of the variation in S-iPTH. The total bone mass at all sites of the forearm, fracture load and stress-strain index was higher (P < 0·001) in Bangladeshi and Finnish women than in Somali women. The high prevalence of hypovitaminosis D, SHPT and low bone status in Somali women indicates a higher risk of osteoporosis.
Vitamin 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. We 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. We 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). Our 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.
Abstract Insufficient vitamin D status (serum 25-hydroxyvitamin D (S-25(OH)D)<50 nmol/l) is common among immigrants living at the northern latitudes. We investigated ethnic differences in response of S-25(OH)D to vitamin D 3 supplementation, through a 5-month randomised controlled trial, in East African and Finnish women in Southern Finland (60°N) from December 2014 to May 2015. Vitamin D intakes (dietary and supplemental) were also examined. Altogether, 191 subjects were screened and 147 women (East Africans n 72, Finns n 75) aged 21–64 years were randomised to receive placebo or 10 or 20 µg of vitamin D 3 /d. S-25(OH)D concentrations were assessed by liquid chromatography–tandem MS. At screening, 56 % of East Africans and 9 % of Finns had S-25(OH)D<50 nmol/l. Total vitamin D intake was higher in East Africans than in Finns (24·2 ( sd 14·3) v. 15·2 ( sd 13·4) µg/d, P <0·001). Baseline mean S-25(OH)D concentrations were higher in Finns (60·5 ( sd =16·3) nmol/l) than in East Africans (51·5 ( sd 15·4) nmol/l) ( P =0·001). In repeated-measures ANCOVA (adjusted for baseline S-25(OH)D), mean S-25(OH)D increased by 8·5 and 10·0 nmol/l with a 10-µg dose and by 10·7 and 17·1 nmol/l with a 20-µg dose for Finns and East Africans, respectively ( P >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 D 3 supplementation was effective in increasing S-25(OH)D in both groups of women, and no ethnic differences existed in the response to supplementation.
Abstract 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. Spearman’s 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.
Abstract Background Dietary 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. Methods Associations 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. Results No 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). Conclusions Our 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.
