Environmental factors such as sunshine hours, temperature and UV radiation (UVR) are known to influence seasonal fluctuations in vitamin D concentrations. However, currently there is poor understanding regarding the environmental factors or individual characteristics that best predict neonatal 25-hydroxyvitamin D (25(OH)D) concentrations. The aims of this study were to (1) identify environmental and individual determinants of 25(OH)D concentrations in newborns and (2) investigate whether environmental factors and individual characteristics could be used as proxy measures for neonatal 25(OH)D concentrations. 25-Hydroxyvitamin D3 (25(OH)D3) was measured from neonatal dried blood spots (DBS) of 1182 individuals born between 1993 and 2002. Monthly aggregated data on daily number of sunshine hours, temperature and UVR, available from 1993, were retrieved from the Danish Meteorological Institute. The individual predictors were obtained from the Danish National Birth register, and Statistics Denmark. The optimal model to predict 25(OH)D3 concentrations from neonatal DBS was the one including the following variables: UVR, temperature, maternal education, maternal smoking during pregnancy, gestational age at birth and parity. This model explained 30 % of the variation of 25(OH)D3 in the neonatal DBS. Ambient UVR in the month before the birth month was the best single-item predictor of neonatal 25(OH)D3, accounting for 24 % of its variance. Although this prediction model cannot substitute for actual blood measurements, it might prove useful in cohort studies ranking individuals in groups according to 25(OH)D3 status.

More than one-third of humans and companion dogs in Western societies are overweight or obese. In people, vitamin D deficiency is widespread and associated with obesity, a now recognised inflammatory state. Low vitamin D status occurs in dogs with inflammatory conditions, but its relationship with obesity has not been investigated. In otherwise healthy privately owned adult dogs of ideal body condition (control, n 7) and dogs with overweight to obese body condition (treatment, n 8), serum 25-hydroxyvitamin D (25(OH)D) concentration and body composition as inferred from 2H-labelled water dilution space were evaluated. Subsequently, the dogs were transitioned to a commercial canine therapeutic weight-loss diet; control dogs were fed to maintain body weight and treatment dogs were energy-restricted to achieve a safe weight-loss rate. Thereafter, serum 25(OH)D concentration was re-evaluated 8 weeks after diet transition, and at the study end, which was 6 months or when ideal body condition was achieved. At study end, body composition analysis was repeated. Initial body condition scores and percentage body fat were positively correlated (ρ = 0·891; P < 0·001). However, percentage body fat and serum 25(OH)D concentration were not significantly correlated. Final serum 25(OH)D concentrations were greater (P < 0·05) than initial concentrations for control and treatment groups, indicating a diet but not weight-loss effect on vitamin D status. These findings suggest that vitamin D status of dogs is not affected by obesity or loss of body fat with therapeutic weight reduction.

The ability to synthesise sufficient vitamin D through sunlight in human subjects can be limited. Thus, diet has become an important contributor to vitamin D intake and status; however, there are only a few foods (e.g. egg yolk, oily fish) naturally rich in vitamin D. Therefore, vitamin D-enriched foods via supplementing the animals’ diet with vitamin D or vitamin D fortification of foods have been proposed as strategies to increase vitamin D intake. Evidence that cholecalciferol (vitamin D3) and calcifediol (25(OH)D3) content of eggs, fish and milk increased in response to vitamin D3 supplementation of hens, fish or cows’ diets was identified when vitamin D-enrichment studies were reviewed. However, evidence from supplementation studies with hens showed only dietary 25(OH)D3, not vitamin D3 supplementation, resulted in a pronounced increase of 25(OH)D3 in the eggs. Furthermore, evidence from randomised controlled trials indicated that a 25(OH)D3 oral supplement could be absorbed faster and more efficiently raise serum 25(OH)D concentration compared with vitamin D3 supplementation. Moreover, evidence showed the relative effectiveness of increasing vitamin D status using 25(OH)D3 varied between 3·13 and 7·14 times that of vitamin D3, probably due to the different characteristics of the investigated subjects or study design. Therefore, vitamin D-enrichment or fortified foods using 25(OH)D3 would appear to have advantages over vitamin D3. Further well-controlled studies are needed to assess the effects of 25(OH)D3 enriched or fortified foods in the general population and clinical patients.

We previously found a weak response in serum 25-hydroxyvitamin D3 (25(OH)D3) concentrations when dogs were supplemented with oral vitamin D3 (D3). In the present study, we determined the relative potency of oral 25(OH)D3 compared with D3 for increasing vitamin D status in dogs with low serum 25(OH)D concentrations. Four male and three female, 4-year-old, intact, lean, genetically related, Chinese-crested/beagle dogs were studied in a randomised, single cross-over trial. After feeding a low-vitamin D diet (<4 IU/100 g) for 30 d, four dogs received daily D3 supplementation at 2·3 µg/kg body weight0·75, while three dogs received a molar equivalency as 25(OH)D3. The supplements, dissolved in ethanol, were applied to a commercial treat for consumption. Serum 25(OH)D3 and 24R,25-dihydroxyvitamin D3 (24R,25(OH)2D3) were analysed weekly using a validated HPLC method. Both supplementations increased (P ≤ 0·01) serum 25(OH)D3 concentrations. However, oral 25(OH)D3 resulted in greater (P < 0·0001) concentrations than D3 by week 1, with a difference of 173 % (P < 0·0001) by week 2. The supplementation period was limited to 14 d after serum 25(OH)D3 concentrations were not appearing to plateau. Thereafter, a washout period of 1 month separated the cross-over. Following 25(OH)D3, but not D3 supplementation, serum 24R,25(OH)2D3 concentrations increased (P ≤ 0·02), 3 to 5 weeks after initiating supplementation. Vitamin D status, as indicated by serum 25(OH)D3 and 24R,25(OH)2D3 concentrations, is more rapidly and efficiently increased in adult dogs by oral supplementation of 25(OH)D3 than D3.

Vitamin D is obtained by cattle from the diet and from skin production via UVB exposure from sunlight. The vitamin D status of the cow impacts the vitamin D content of the milk produced, much like human breast milk, with seasonal variation in the vitamin D content of milk well documented. Factors such as changes in husbandry practices therefore have the potential to impact the vitamin D content of milk. For example, a shift to year-round housing from traditional practices of cattle being out to graze during the summer months and housed during the winter only, minimises exposure to the sun and has been shown to negatively influence the vitamin D content of the milk produced. Other practices such as changing dietary sources of vitamin D may also influence the vitamin D content of milk, and evidence exists to suggest genetic factors such as breed can cause variation in the concentrations of vitamin D in the milk produced. The present review aims to provide an overview of the current understanding of how genetic and environmental factors influence the vitamin D content of the milk produced by dairy cattle. A number of environmental and genetic factors have previously been identified as having influence on the nutritional content of the milk produced. The present review highlights a need for further research to fully elucidate how farmers could manipulate the factors identified to their advantage with respect to increasing the vitamin D content of milk and standardising it across the year.

Recent studies have suggested an association between vitamin D and non-alcoholic fatty liver disease (NAFLD); however, some results are subject to debate. This study was carried out to evaluate the correlation between NAFLD and vitamin D in men and women in East China. The data were obtained from a cross-sectional study that focused on the health and metabolic status of adults in sixteen areas of East China. According to ultrasonic assessments, the patients were divided into normal and NAFLD groups. Demographic characteristics and biochemical measurements were obtained. Binary logistic regression analysis was used to explore the association. In total, 5066 subjects were enrolled, and 2193 (43·3 %) were diagnosed with NAFLD; 84·56 % of the subjects showed vitamin D deficiency. Subjects with high vitamin D levels had a lower prevalence of NAFLD, particularly male subjects. Within the highest quartile of vitamin D levels, the prevalence of NAFLD was 40·8 %, whereas the lowest quartile of vitamin D levels showed a prevalence of 62·2 %, which was unchanged in women across the vitamin D levels. Binary logistic analysis showed that decreased vitamin D levels were associated with an increased risk of NAFLD (OR 1·54; 95 % CI 1·26, 1·88). This study suggests that vitamin D levels are significantly associated with NAFLD and that vitamin D acts as an independent factor for NAFLD prevalence, particularly in males in East China. Vitamin D interventional treatment might be a new target for controlling NAFLD; elucidating the mechanism requires further research.

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 content of vitamin D in pork produced in conventional systems depends on the vitamin D concentration in the pig feed. Both vitamin D3 and 25-hydroxyvitamin D3 (25(OH)D3) are essential sources of dietary vitamin D; however, bioavailability assessed by serum 25(OH)D3 concentration is reported to be different between the two sources. Furthermore, the relationship between serum 25(OH)D3 level and the tissue content of vitamin D3 and 25(OH)D3 is unknown. The objective of this study was to investigate the potential of increasing the content of vitamin D in different pig tissues by increasing the levels of vitamin D3 and 25(OH)D3 in the pig feed for 49 d before slaughter. Concurrently, the 25(OH)D3 level in serum was investigated as a biomarker to assess the content of vitamin D3 and 25(OH)D3 in pig tissues. Adipose tissue, white and red muscle, the liver and serum were sampled from pigs fed feed containing either vitamin D3 or 25(OH)D3 at 5, 20, 35 or 50 µg/kg feed for 7 weeks before slaughter. The tissue 25(OH)D3 level was significantly higher in the pigs fed 25(OH)D3 compared with those fed vitamin D3, while the tissue vitamin D3 level was higher in the pigs fed vitamin D3 compared with those fed 25(OH)D3. The content of 25(OH)D3 in the different tissues fully correlated with the serum 25(OH)D3 level, whereas the correlation between the tissue content of vitamin D3 and serum 25(OH)D3 was dependent on the source of the ingested vitamin D3.

Vitamin D and folate are associated with decreased colorectal cancer risk and their association with colorectal cancer prognosis is under investigation. We assessed the levels of plasma 25-hydroxyvitamin D3 (25(OH)D3), folate and vitamin B12 in an international pilot study in order to determine variability of these biomarkers based on geographical location. Plasma 25(OH)D3, folate and vitamin B12 concentrations were measured in 149 invasive, newly diagnosed colorectal cancer cases from Heidelberg (Germany), Seattle (WA, USA), and Tampa (FL, USA) and in ninety-one age- and sex-matched controls. Their associations with potential predictors were assessed using multivariate linear regression analyses. Plasma 25(OH)D3, folate and vitamin B12 concentrations differed by location. Other predictors were season for 25(OH)D3 and tumour stage (vitamin B12). Season-corrected average 25(OH)D3 concentrations were higher in Heidelberg (31·7 ng/ml; range 11·0–83·0 ng/ml) than in Seattle (23·3 ng/ml; range 4·0–80·0 ng/ml) and Tampa (21·1 ng/ml; range 4·6–51·6 ng/ml). In Heidelberg, a strong seasonal variation was observed. Folate (11·1 ng/ml) and vitamin B12 (395 pg/ml) concentrations in Heidelberg were lower than those in Seattle (25·3 ng/ml and 740 pg/ml, respectively) and Tampa (23·8 ng/ml and 522 pg/ml, respectively). Differences in plasma 25(OH)D3 and folate concentrations between Heidelberg and the US sites were observed, probably reflecting variation in outdoor activities and sun-avoidance behaviour during summer as well as in folic acid fortification and supplement use. Intra-site differences at each study location were greater than between-location variability, suggesting that individual health behaviours play a significant role. Nevertheless, the intra-site differences we observed may be due to chance because of the limited sample size. Our pilot study illustrates the value of an international cohort in studying colorectal cancer prognosis to discern geographical differences in a broad range of exposures.

Two experiments, a performance experiment and a mineral balance study, were conducted on grower–finisher pigs (42 to 101 kg live weight) to investigate the effects of Peniophora lycii phytase enzyme and 25-hydroxyvitamin D3 (25-OHD3) on growth performance, carcass characteristics, nutrient retention and excretion, and bone and blood parameters. The two experiments were designed as a 2 × 2 factorial (two levels of phytase and two levels of 25-OHD3). The four diets were T1, low-phosphorous diet; T2, T1 + phytase; T3, T1 + 25-OHD3 and T4, T1 + phytase + 25-OHD3 diet. In all, 25 μg of 25-OHD3 was used to replace 1000 IU of vitamin D3 in diets T3 and T4. Diets were pelleted (70°C) and formulated to contain similar concentrations of energy (13.8 MJ DE/kg), lysine (9.5 g/kg) and digestible phosphorus (P; 1.8 g/kg). Neither the inclusion of phytase nor 25-OHD3 in the diet had any effect on pig performance. There was an interaction between phytase and 25-OHD3 on calcium (Ca) and P retention (P < 0.01) and on the apparent digestibility of ash (P < 0.01), P (P < 0.001) and Ca (P < 0.001). Pigs offered phytase diets only, had a higher retention of Ca and P and digestibility of ash (P < 0.01), P (P < 0.001) and Ca (P < 0.01) compared with pigs offered unsupplemented diets. However, when the combination of phytase and 25-OHD3 were offered, no effects were detected compared with 25-OHD3 diets only. Pigs fed phytase diets had higher bone ash (P < 0.01), bone P (P < 0.01) and bone Ca (P < 0.05) concentrations compared with pigs offered non-phytase diets. In conclusion, pigs offered phytase diets had a significantly increased bone ash, Ca and P than pigs offered unsupplemented phytase diets. However, there was no advantage to offering a combination of phytase and 25-OHD3 on either bone strength or mineral status compared to offering these feed additives separately.

In food databases, the specific contents of vitamin D3 and 25-hydroxyvitamin D3 in food have been implemented in the last 10 years. No consensus has yet been established on the relative activity between the components. Therefore, the objective of the present study was to assess the relative activity of 25-hydroxyvitamin D3 compared to vitamin D3. The design was a parallel study in pigs (n 24), which from an age of 12 weeks until slaughter 11 weeks later were fed approximately 55 μg vitamin D/d, as vitamin D3, in a mixture of vitamin D3 and 25-hydroxyvitamin D3, or 25-hydroxyvitamin D3. The end-points measured were plasma 25-hydroxyvitamin D3, and in the liver and loin the content of vitamin D3 and 25-hydroxyvitamin D3. Vitamin D3 and 25-hydroxyvitamin D3 in the feed did not affect 25-hydroxyvitamin D3 in the plasma, liver or loin differently, while a significant effect was shown on vitamin D3 in the liver and loin (P < 0·001). 25-Hydroxyvitamin D3 in the plasma, liver and loin significantly correlates with the sum of vitamin D3 and 25-hydroxyvitamin D3 in the feed (P < 0·05). Therefore, 25-hydroxyvitamin D3 should be regarded as having the same activity as vitamin D3 in food databases. Sole use of 25-hydroxyvitamin D3 as a vitamin D source in pig feed will produce liver and meat with a negligible content of vitamin D3, while an increased content of vitamin D3 in the feed will produce liver and meat with increased content of both vitamin D3 and 25-hydroxyvitamin D3.