Sun exposure in pigs increases the vitamin D nutritional quality of pork

D. Enette Larson-Meyer; Bennett C. Ingold; Samanta R. Fensterseifer; Kathleen J. Austin; Perry J. Wechsler; Bruce W. Hollis; Andrew J. Makowski; Brenda M. Alexander

doi:10.1371/journal.pone.0187877

Abstract

There is a high prevalence of vitamin D insufficiency and deficiency worldwide likely because of both limited sun-exposure and inadequate dietary intake. Meat, including pork, is not typically considered a dietary source of vitamin D, possibly because of management practices that raise pigs in confinement. This experiment determined the vitamin D content of loin and subcutaneous adipose tissue in sun-exposed finisher pigs. Two separate groups of pigs were used. The first group (28 white Landrace-Duroc) was assigned at random to either sunlight exposure (SUN) in spring and summer or confinement per standard practice (Control). The second (24 Yorkshire-Duroc-Landrace) underwent the same exposure protocol but was exposed in summer and fall or assigned to control (Control). A subsample of five SUN and four Control pigs, matched for weight and body condition score, was selected for slaughter from each group. Pigs (n = 10 SUN, n = 8 Control) had blood drawn for analysis of 25(OH)D₃ concentration before/after sun exposure or control, and tissue samples were taken at slaughter for analysis of tissue vitamin D3 and 25(OH)D₃ concentration. Three random samples from a single loin chop and surrounding adipose were collected and analyzed. Serum concentrations of 25(OH)D₃ did not differ (P≥0.376) between treatments prior to sun exposure in either group, but was increased (time*treatment interaction, P<0.001) with SUN exposure. Total vitamin D content (D3 plus 25(OH)D₃) of loin tissue was increased (P < 0.001) with sun exposure and averaged 0.997±0.094 μg/100g and 0.348±0.027 μg/100g for sun and control pigs, respectively. While exposure to sunlight increased (P = 0.003) tissue content of 25(OH) D in subcutaneous adipose tissue, vitamin D₃ content was similar between treatments (P = 0.56). Sunlight exposure in pigs increased the vitamin D content of loin, and may provide an additional source of dietary vitamin D.

Citation: Larson-Meyer DE, Ingold BC, Fensterseifer SR, Austin KJ, Wechsler PJ, Hollis BW, et al. (2017) Sun exposure in pigs increases the vitamin D nutritional quality of pork. PLoS ONE 12(11): e0187877. https://doi.org/10.1371/journal.pone.0187877

Editor: Cristina Óvilo, INIA, SPAIN

Received: July 21, 2017; Accepted: October 29, 2017; Published: November 14, 2017

Copyright: © 2017 Larson-Meyer et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting Information files.

Funding: This study was supported by University of Wyoming, Agriculture Experiment Station. Bruce W. Hollis and Andrew J. Makowski at Heartland Assays provided the analytical services for fee. There was no additional external funding received for this study. Andrew J. Makowski is employed by Heartland Assays. Heartland Assays provided support in the form of salary for author AJM, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific role of this author is articulated in the ‘author contributions’ section.

Competing interests: Serum and tissue vitamin D analyses were conducted by Heartland Assays (Ames, IA) who were blinded for treatment group. Bruce W. Hollis and Andrew J. Makowski at Heartland Assays provided the analytical services for fee. Andrew J. Makowski wrote the methods section for the LCMSMS analysis and Bruce W. Hollis assisted with the discussion. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Introduction

Vitamin D is known for its critical role in bone health [1]. Increasing evidence also suggests vitamin D plays a role in the prevention of many chronic diseases including certain cancers [2,3,4], cardiovascular disease [5], type 2 diabetes [6], and Alzheimer’s disease [7]. Of the 30 leading causes of death in the US in 2010 19 were linked to low vitamin D status [8]. At the same time, a high prevalence of vitamin D insufficiency worldwide has been identified [9,10].

Vitamin D is unique among vitamins in that it can be obtained from diet as well as synthesized in the body from exposure to UVB radiation from sunlight. Endogenous synthesis, however, is considered the most available source of vitamin D₃ [11]. Compared to what is typically consumed in the diet, higher amounts of vitamin D can be obtained from sun exposure. It is estimated, for example, that a single 10–15 minute [12] exposure during peak sunlight in July in a bathing suit will produce between 10,000 and 20,000 IU of vitamin D [13]. Concerns of increased risk of skin cancer and/or photo-aging, however, keep many people out of the sun. To achieve sufficiency, these individuals must obtain vitamin D through diet and/or supplementation. Food sources of vitamin D include oily fish, egg yolks, sun-dried mushrooms, and fortified milk, yogurt, margarine and several ready-to-eat cereals [14].

Meat, in general, is not considered a good source of vitamin D. The vitamin D content of pork may be particularly low because of husbandry practices, which confine pigs indoors with limited exposure to sunlight. Furthermore, the USDA nutrient database only evaluates vitamin D₃ and D₂ content of food sources [15]. Heaney et al. has recently argued that vitamin D content in meat products is underestimated because of the failure to consider the hydroxylated form, 25(OH)D₃ [16], the immediate product of liver hydroxylation of vitamin D₃ and D₂. Later work from Heaney has suggested that solar inputs of vitamin D are less than previously thought. Instead, there is a significant input of vitamin D from undocumented food sources such as preformed 25(OH)D₃ in animal products[17]. Moreover, 25(OH)D₃ is estimated to be about five times as potent as vitamin D₃ in raising serum 25(OH)D₃ concentrations [18]. Recent tissue culture and animal studies highlight that vitamin D₃ is readily sequestered by adipose tissue [19], while 25(OH)D₃ is distributed throughout the body and is taken up by skeletal muscle tissue [16,20].

Although swine are generally raised in confinement, they [21], like other agricultural animals including cattle [22] and chickens [23], have the capacity to synthesize vitamin D. Sun exposure in pigs, therefore, has the potential to increase the vitamin D content in pork. The objective of this experiment was to determine the effects of sunlight exposure of pigs on serum concentration as well as loin and subcutaneous adipose tissue content of 25(OH) and vitamin D3.

Materials and methods

All experimental protocols were approved by the University of Wyoming (UW) institutional animal care and use committee (IACUC).

White Landrace-Duroc cross pigs (n = 28, 14 male, 14 female; 81±16 d of age, 29±1 kg) were assigned at random to either sunlight exposure (SUN) in the spring and summer (n = 14) or confined to indoors as per standard practice (Control) with limited exposure to outdoor sunlight (n = 14). The study was replicated with a second group of white Yorkshire-Duroc-Landrace cross-bred pigs (n = 24, 10 male, 14 female) aged 80±13 d, 31.6±2.1 kg with sunlight exposure (SUN) in the summer and fall (n = 12) or Control (n = 12). From each group of pigs, a subsample of sun-exposed (n = 5 per group) and control (n = 4 per group) pigs, matched for body condition score, were selected for blood and tissue analysis; these analyses were performed only in a subsample due to cost constraints. Pig breeds selected are commonly used for pork production. Waldo Farms (DeWitt, NE) supplied the spring-summer group of pigs. The summer-fall group of pigs was born to the University of Wyoming Research and Extension Center farm.

Pigs were raised at UW research and extension center in a confined temperature-controlled system with natural airflow and provided standard care including ad libitum water and feed. Diets were formulated as a growth ration with a corn and soybean base and vitamin and trace mineral premixes added (nutrient analysis is shown in Table 1). Pigs were housed by group in 3.7 x 3.7 m pens (n = 14 max/pen) with a combination of solid and slotted flooring; the slotted flooring portion of the pens were washed with water twice a day.

Download:

Table 1. Nutrient content of soybean and corn feed with added vitamin and mineral premixes.

https://doi.org/10.1371/journal.pone.0187877.t001

Spring-summer pigs assigned to sun exposure were exposed to natural sunlight one hour each day during solar noon (12:30–1:30 PM standard time) for two weeks surrounding the spring equinox (March 20–April 3) and summer solstice (June 13–26). Summer-fall pigs were exposed to sunlight for an hour daily during solar noon for two weeks surrounding the summer solstice (June 17–30) and fall equinox (September 18-October 1). Sun pigs traveled down a short alley to an outdoor pen on the southern side of the facility. In both groups of SUN pigs, the first exposure period occurred when the pigs were young growers and the second exposure occurred when the pigs were near slaughter weight. Control pigs were raised conventionally, and kept in confinement, with limited sun exposure, throughout the duration of the experiment. Total UV radiation was measured during the exposure period by using a UV spectrometer (Eppley Laborotories Inc. Newport, RI) and a logging data acquisition system (National Instruments, Austin, TX). UVB was calculated by using a UVA/UVB ratio of 20:1,i.e. 5% of total [24]. Blood samples were obtained via cranial vena cava puncture at the beginning and end of the second exposure period in SUN and Control pigs. Blood samples were allowed to clot for 60 minutes and centrifuged (800 g for 20 minutes) by using a Beckman TJ-6 (Brea, CA). Serum was collected and stored at -20°C until analysis.

The selected pigs from spring-summer and summer-fall were slaughtered at the University of Wyoming abattoir on the morning following the last day of sun exposure. At slaughter the pigs were killed by electrical stun followed by exsanguination as per standard slaughter procedures and as approved by the IACUC. Three random samples (≈ 3 g) from a single pork chop (i.e. center loin, tenth rib, and the surroundingadipose) were collected and frozen on dry ice, and stored in eppendorf tubes at -80°C until analysis. Back fat thickness was taken by the average of measurements at the 10^th and last rib. Percentage of fat-free lean was calculated by using the equation of Boggs et al [25].

Serum and tissue vitamin D analyses were conducted by Heartland Assays (Ames, IA) who were blinded for treatment group. Serum concentrations of 25(OH)D₃ were determined by radioimmunoassay (RIA) with tissue content of vitamin D₂, D₃ and 25(OH)D determined via liquid chromatography-mass spectrometry (LC/MS/MS).

Serum 25(OH)D via RIA

The 25(OH)D assay is a two-step procedure [26] using rapid extraction of 25-OH-D and other hydroxylated metabolites with acetonitrile followed by RIA analysis. The RIA utilizes a first antibody co-specific for 25(OH)D₂ and 25(OH)D₃. Following incubation at room temperature, antigen-antibody complexes were separated with a second antibody precipitating complex followed by centrifugation. 25(OH)D equivalent values were calculated directly by the γ-radiation counting system via a smooth-spline method [26]. The 25(OH)D assay has a range of 2.5–100 ng/ml with 8% intra- and 10% inter-assay CV.

25(OH)D₂/25(OH)D₃ and vitamin D₂/vitamin D₃ in adipose and meat/tissue

All samples were weighed and saponified with methanolic potassium hydroxide [27] and spiked with deuterated internal standard for each metabolite being measured (vitamin D3(6,19,19-d3) and 25-hydroxyvitamin D3 (6,19,19-d3). Both deuterated and non-deutrated reagents were purchased from Sigma-Aldrich (St. Louis, MO). Following saponification, samples were extracted by using hexane/ethyl acetate (85:15 v:v). The organic layer was dried and reconstituted in hexane/methylene chloride (90:10 v:v) and both 25OH and vitamin D were isolated on a 0.5 gram silica SPE column. HPLC was utilized to further purify samples [27]. After purification, samples were dried in Savant vacuum dryer and then re-constituted into LCMS-grade methanol and LCMS high-purity water both with 0.1% formic acid, and then injected onto an Agilent 1290 HPLC with an Agilent C18 Poroshell Column coupled to an Agilent 6460 Triple-quad mass spec (Quantitative Analysis, Version B.07.00, Agilent Technologies, Santa Clara, CA) with electrospray ionization source (ESI) in positive mode and analyzed by using Masshunter software[27]. Both assays had R² values greater than 0.99. 25(OH)D_2/D₃ intra-assay %CV = 5.0% and inter-assay %CV = 8.6% with extraction efficiencies of >68% and assay range of 0.5–312.5ng/g. Vitamin D₂/D₃ intra-assay %CV = 9.9% and inter-assay %CV = 11.2% with extraction efficiencies of >64%. Limit of quantification was 0.5ng/g and assay range of 0.5-625ng/g with a limit of detection of 0.1ng/g for all analytes. All values were adjusted for extraction efficiency prior to statistical analysis.

Statistical procedures

Only serum 25(OH)D₃ data for the second exposure period when the pigs were close to slaughter are included. Data are presented as mean ± standard error unless otherwise specified. Data were analyzed by using Minitab statistical software version 17 (State College, PA). Two sample t-test with equal or unequal variances were used to compare differences in body weights and body composition and pre-treatment serum 25(OH)D₃ concentrations between SUN and Control pigs. Repeated Measures ANOVA was used to test for a time (pre versus post sun exposure) by treatment (SUN versus Control) effect on serum 25(OH)D₃ concentrations. A two-sample t-test with equal or unequal variances was used to test for differences in vitamin D₃ and 25(OH)D₃ in loin and subcutaneous adipose from the SUN versus control pigs at slaughter and to test for differences between summer and fall exposure pigs for serum and tissue vitamin D concentrations. Pearson correlation coefficients were used to determine associations between tissues and serum concentrations of vitamin D.

Results

Body mass, composition and weight gain

Starting weights, slaughter weights, and average daily gain (ADG) were not different between control and SUN pigs for spring-summer and summer-fall groups (Table 2, S1 Table). At slaughter, body composition measured as back fat thickness at the first and last ribs and percentage fat-free lean tissue were similar between control and SUN pigs (Table 2, S1 Table).

Download:

Table 2. Body weight and body composition in the subgroup of sun-exposed and control pigs selected for tissue analysis.

https://doi.org/10.1371/journal.pone.0187877.t002

UV exposure

Average UVB radiation at solar noon (±30 minutes) for the 14 days of exposure around the summer solstice and 14 days around the fall equinox is shown in Fig 1. Average UVB during the 14-day exposure was higher in the summer compared to the fall (P = 0.009).

Download:

Fig 1. Summer and fall average UVB exposure.

Average UVB radiation during noontime sun exposure for 14 days in the summer and fall at close to the summer solstice and fall equinox, respectively. Data were recorded every second for the one hour exposure period around solar noon (± 30 minutes). Each point represents the mean of the 3600 points. Error, expressed as 95% confidence intervals about the mean are not visible (range = 6.2 X 10⁻⁵ to 0.033731). Days with low UVB radiation were cloudy during the sun exposure period.

https://doi.org/10.1371/journal.pone.0187877.g001

Serum 25(OH)D₃

There were no differences (P≥0.325) in serum concentrations of 25(OH)D₃ between SUN (46.1±1.7 ng/ml) and Control pigs (39.9±5.6 ng/ml) prior to sun exposure. Serum 25(OH)D₃, however, was increased (P<0.001) following sun exposure in SUN but not Control pigs (P<0.001, time*treatment interaction [S1 Fig]) (Fig 2), and was higher post-exposure in the SUN pigs exposed in the fall compared those exposed in the summer (Fig 2).

Download:

Fig 2. Effects of sun exposure on vitamin D status.

Serum 25(OH)D₃ concentrations before (Pre) and after (Post) sun exposure for one hour daily at solar noon for 2-weeks (SUN) or standard confinement (Control) in the summer and fall. Summer exposure occurred in the spring-summer group and fall exposure occurred in the summer-fall group in finisher pigs 2-weeks prior to slaughter.

https://doi.org/10.1371/journal.pone.0187877.g002

Tissue vitamin D

Loin tissue.

Following sun exposure, vitamin D₃ content was higher (P<0.001, [S2 Fig]) in the loin of SUN pigs (0.716± 0.097 μg/100g; 28.6± 3.9 IU/100g) compared to control pigs (0.218± 0.024 μg/100g; 8.7± 1.0 IU/100g) as was loin content of 25(OH)D₃ (SUN = 0.281± 0.014, control = 0.130± 0.016 μg /100g). Total vitamin D content (D3 plus 25(OH)D₃) of loin was also higher (P = 0.001) in SUN pigs (0.997±0.094 μg/100g) compared to control pigs (0.348±0.027 μg/100g) (Fig 3).

Download:

Fig 3. Effects of sun exposure on vitamin D concentrations in loin tissue.

Total vitamin D content includes both vitamin D₃ and 25(OH)D₃. The black bar represents the value presented in the USDA national nutrient database for the vitamin D content of “raw pork, center loin.” Center loin samples were collected on the day of slaughter. Error bars represent the standard error. (1 ug vitamin D₃ = 40 IU).

https://doi.org/10.1371/journal.pone.0187877.g003

Subcutaneous adipose.

Adipose content of 25(OH)D₃ content was greater in SUN pigs (0.814±0.1 μg /100g) versus that in control pigs (0.406±0.044 μg /100g; P = 0.003 [S2 Fig]). Vitamin D₃ content was not different between groups (SUN = 4.6±0.6 μg/100g; 184.2±25.7 IU/100g; Control = 4.1±0.0.5 μg/100g; 164.3±19.6 IU/100g, P = 0.56). Total vitamin D content in subcutaneous adipose, as well, did not differ (P = 0.35) between SUN (5.42 μg/100g) and control (4.513 μg/100g) pigs.

Vitamin D₂ was not detectable in any tissue samples.

Association between serum 25(OH)D₃ and tissue concentrations

Serum 25(OH)D₃ concentrations were positively associated with loin vitamin D₃ (r = 0.63, P = 0.005) loin 25(OH)D₃ (r = 0.83, P<0.001) and subcutaneous fat 25(OH)D₃ (r = 0.73, P = 0.001) content, but not with subcutaneous adipose vitamin D₃ content (r = 0.19, P>0.05).

Discussion

We have demonstrated sun exposure prior to slaughter in pigs significantly increases serum concentrations of vitamin D and vitamin D content in the lean tissue of the loin. To our knowledge, this is the first study demonstrating the effects of natural sunlight in pigs on the vitamin D content of pork products.

The main finding of this experiment is of significant importance when considering dietary intake of vitamin D. The current recommended dietary allowance (RDA) for vitamin D is 600 IU/d for children and adults <70 years old [28]. Despite a recent increase in the RDA of vitamin D from 400 IU to 600 IU, many researchers believe the current RDA is still not sufficient for optimal health [29,30]. For example, the Endocrine Society recommends 1500–2000 IU/d of vitamin D for most individuals with higher intakes recommended for individuals at risk for vitamin D deficiency [30]. While the RDA of 600 IU/d supports circulating 25(OH)D₃ concentrations of 20 ng/ml (sufficient to prevent clinical rickets) such circulating concentrations may not provide further health benefits including reduced risk of certain cancers [31,32,33] and prevention of stress fractures [34]. Heaney suggests the optimal concentration of 25(OH)D₃ should be at least 30 ng/ml and further stresses that maintaining circulating concentrations of 25(OH)D₃ in the range of 30–50 ng/ml may produce added health benefits [35]. Furthermore, there is evidence that a concentration of 48 ng/ml 25(OH)D₃ may be optimal for many physiological functions such as fully suppressed parathyroid hormone, efficient intestinal calcium absorption, and optimized vitamin D concentrations in breastmilk [8]. These higher concentrations of 25(OH)D₃ are believed to approach those of our hominid ancestors based on research in African tribes [36]. Considering this evidence, increased vitamin D in the diet may be beneficial for achieving optimal 25(OH)D₃ status, or at a minimum, meeting the RDA for vitamin D. Many people in the US [10] and worldwide [9] fail to maintain vitamin D concentrations above 20 ng/ml.

Strategies to fortify or naturally add vitamin D to the food supply are currently being explored. Green and colleagues [37] have suggested a greater range of food vehicles for fortification, other than dairy, margarine, and cereals, may be necessary to improve the vitamin D status of populations. This increase in dietary vitamin D may be achieved by enhancing the natural vitamin D content of foods, termed bio-addition. Current strategies of bio-addition include exposing mushrooms to UV light after harvest [38], and supplementing laying hens with vitamin D to increase the vitamin D content of egg yolks [39]. Altering the vitamin D content of feed has also been demonstrated to affect the vitamin D₃ and 25(OH)D₃ content in meat cuts from pigs[40]. Altering modern swine management practices to allow pigs exposure to sunlight may also be an effective means to naturally increase the vitamin D content of pork products.

A recent study found that exposing hens to artificial sunlight via 23-W UVB lamps for 3 hr daily for four weeks increased the vitamin D content of egg yolks by 337% and the content of fibularis longus muscle to detectable concentrations of 0.16 to 0.96 μg/100g [23]. This UVB exposure protocol was three to four times more effective as supplementation with 3000 IU of vitamin D/kg of feed in increasing D₃ concentrations of egg yolks and meat. Another study in a small sample of Gottingen minipigs reported that UVB exposure was more effective than dietary administration of vitamin D₃ at increasing vitamin D tissue content [21]. Our data support exposure to natural sunlight for an hour per day is effective at increasing vitamin D content of pork products.

In a previous study of Clausen and colleagues [41], a thorough analysis of vitamin D content of pork cuts in pigs conventionally raised in absence of direct sunlight exposure yielded a vitamin D₃ and 25(OH)D, content of 0.4 and 0.5 ng/g in the loin tissue, and 5 and 3.1 ng/g in the adipose, respectively. In contrast, sun-exposed pigs in our experiment had an average D₃ content of 7.16 ng/g in the loin and 46.05 ng/g in subcutaneous adipose. This increase is a near 18-fold of D₃ in loin tissue and a 9-fold increase in subcutaneous adipose tissue. In the present experiment 25(OH)D content averaged 2.81 ng/g (11.2 IU/100g) in the loin and 8.14 ng/g (32.6 IU/100g) adipose of sun-exposed pigs. Interestingly, our control pigs also had higher vitamin D content than pigs in the Clausen et al. analysis, which is likely attributable to the dietary supplementation of our pigs. The USDA nutrient database reports the vitamin D₃ content of a raw, lean center loin to be 14 IU/100g. Our sun-exposed pigs had an average total vitamin D content of 39.9 IU/100g. The USDA nutrient database currently does not include the 25(OH)D₃ content of meat products. Considering that 25(OH)D₃ is present in natural animal-based products, and has five times the biological activity of vitamin D₃, 25(OH)D₃ should be measured and accounted for in future vitamin D analysis.

Interestingly, in the current study, the vitamin D₃ content of subcutaneous adipose was not further improved by sun exposure and was similar between the sun-exposed and control pigs, despite a 100% percent increase in 25(OH)D₃. The reason for this is unclear. It is possible that a ceiling effect for D₃ storage in adipocytes was reached by the content of D₃ in feed which produced near optimal serum concentrations even before sun exposure (i.e., >40 ng/ml), and could not be further increased with sun exposure. Another possibility is that 25(OH)D₃ concentrations increased in subcutaneous adipose as a direct result of higher serum 25(OH)D₃, which may enhance adipose hydroxylation of 25(OH)D₃. Further research is needed to address these possibilities.

This study has shown that daily sun exposure for two weeks in pigs prior to slaughter increases the vitamin D content of the loin. Lean pork, recently shown to be an effective replacement for chicken and fish in the DASH (Dietary Approaches to Stop Hypertension) diet, can be an additional source of dietary vitamin D especially for individuals with high blood pressure [42]. This research has provided insight into the regulation of vitamin D content in pork products, and the possible benefits of raising pigs with controlled exposure to sunlight. Future work should confirm these findings in other breeds of pigs and determine if shorter, less frequent sunlight exposures would be equally as effective at enhancing vitamin D content of loin and other pork products.

Supporting information

S1 Table. Body weight and body composition in the subgroup of sun-exposed and control pigs selected for tissue analysis.

Starting weights were taken on same day as first blood sample collected before first sun exposure. Slaughter weights were measured immediately before slaughter. Average daily gain in kg/d was also calculated, covering the entire study period. Weights are presented as means ± the standard error. Fat-free lean percentage was calculated as noted in Boggs et al.

https://doi.org/10.1371/journal.pone.0187877.s001

(XLSX)

S1 Fig. Effects of sun exposure on vitamin D status.

Serum 25(OH)D₃ concentrations before (Pre) and after (Post) sun exposure for one hour daily at solar noon for 2-weeks (SUN) or standard confinement (Control) in the summer and fall. Summer exposure occurred in the spring-summer group and fall exposure occurred in the summer-fall group in finisher pigs 2-weeks prior to slaughter.

https://doi.org/10.1371/journal.pone.0187877.s002

(XLSX)

S2 Fig. Effects of sun exposure on vitamin D concentrations in loin tissue.

Total vitamin D content includes both vitamin D₃ and 25(OH)D₃. The black bar represents the value presented in the USDA national nutrient database for the vitamin D content of “raw pork, center loin.” Center loin samples were collected on the day of slaughter. Error bars represent the standard error. (1 ug vitamin D₃ = 40 IU).

https://doi.org/10.1371/journal.pone.0187877.s003

(XLSX)

Acknowledgments

The authors wish to thank Avery Kramer and Kacey Myers for their help with blood draw and sun exposure procedures and David Lutterman for animal care and management.

References

1. Turner AG, Anderson PH, Morris HA (2012) Vitamin D and bone health. Scand J Clin Lab Invest Suppl 243: 65–72.
- View Article
- Google Scholar
2. Ahonen MH, Tenkanen L, Teppo L, Hakama M, Tuohimaa P (2000) Prostate Cancer Risk and Prediagnostic Serum 25-Hydroxyvitamin D Levels (Finland). Cancer Causes & Control 11: 847–852.
- View Article
- Google Scholar
3. Bertone-Johnson ER, Chen WY, Holick MF, Hollis BW, Colditz GA, et al. (2005) Plasma 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D and risk of breast cancer. Cancer Epidemiol Biomarkers Prev 14: 1991–1997. pmid:16103450
- View Article
- PubMed/NCBI
- Google Scholar
4. Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP (2007) Vitamin D and calcium supplementation reduces cancer risk: Results of a randomized trial. American Journal of Clinical Nutrition 85: 1586–1591. pmid:17556697
- View Article
- PubMed/NCBI
- Google Scholar
5. Rimm EB, Liu Y, Hollis BW, Giovannucci E (2008) 25-Hydroxyvitamin D and Risk of Myocardial Infarction in Men: A Prospective Study. Archives of Internal Medicine 168: 1174–1180. pmid:18541825
- View Article
- PubMed/NCBI
- Google Scholar
6. Mitri J, Muraru MD, Pittas AG (2011) Vitamin D and type 2 diabetes: a systematic review. Eur J Clin Nutr 65: 1005–1015. pmid:21731035
- View Article
- PubMed/NCBI
- Google Scholar
7. Shen L, Ji HF (2015) Vitamin D deficiency is associated with increased risk of Alzheimer's disease and dementia: evidence from meta-analysis. Nutr J 14: 76. pmid:26231781
- View Article
- PubMed/NCBI
- Google Scholar
8. Baggerly CA, Cuomo RE, French CB, Garland CF, Gorham ED, et al. (2015) Sunlight and Vitamin D: Necessary for Public Health. J Am Coll Nutr 34: 359–365. pmid:26098394
- View Article
- PubMed/NCBI
- Google Scholar
9. Prentice A (2008) Vitamin D deficiency: a global perspective. Nutr Rev 66: S153–164. pmid:18844843
- View Article
- PubMed/NCBI
- Google Scholar
10. Calvo MS, Whiting SJ (2003) Prevalence of Vitamin D Insufficiency in Canada and the United States: Importance to Health Status and Efficacy of Current Food Fortification and Dietary Supplement Use. Nutrition reviews 61: 107–113. pmid:12723644
- View Article
- PubMed/NCBI
- Google Scholar
11. Macdonald HM (2013) Contributions of sunlight and diet to vitamin D status. Calcif Tissue Int 92: 163–176. pmid:23001438
- View Article
- PubMed/NCBI
- Google Scholar
12. Holick MF (2007) Vitamin D Deficiency. The New England Journal of Medicine 357: 266–281. pmid:17634462
- View Article
- PubMed/NCBI
- Google Scholar
13. Holick MF, Chen TC, Lu Z, Sauter E (2007) Vitamin D and skin physiology: a D-lightful story. J Bone Miner Res 22 Suppl 2: V28–33.
- View Article
- Google Scholar
14. Moore CE, Murphy MM, Holick MF (2005) Vitamin D intakes by children and adults in the United States differ among ethnic groups. The Journal of nutrition 135: 2478–2485. pmid:16177216
- View Article
- PubMed/NCBI
- Google Scholar
15. US Department of Agriculture ARS, Nutrient Data Library USDA National Nutrient Database for Standard Reference.
16. Heaney RP, Horst RL, Cullen DM, Armas LAG (2009) Vitamin D3 Distribution and Status in the Body. Journal of the American College of Nutrition 28: 252–256. pmid:20150598
- View Article
- PubMed/NCBI
- Google Scholar
17. Heaney RP, Laura AGA, French C (2013) All-Source Basal Vitamin D Inputs Are Greater Than Previously Thought and Cutaneous Inputs Are Smaller. The Journal of Nutrition 143: 571. pmid:23514768
- View Article
- PubMed/NCBI
- Google Scholar
18. Taylor CL, Patterson KY, Roseland JM, Wise SA, Merkel JM, et al. (2014) Including food 25-hydroxyvitamin D in intake estimates may reduce the discrepancy between dietary and serum measures of vitamin D status. J Nutr 144: 654–659. pmid:24623845
- View Article
- PubMed/NCBI
- Google Scholar
19. Brouwer DAJ, Beek JV, Ferwerda H, Brugman AM, Klis FRMvd, et al. (1998) Rat adipose tissue rapidly accumulates and slowly releases an orally-administered high vitamin D dose. British Journal of Nutrition 79: 527–532. pmid:9771340
- View Article
- PubMed/NCBI
- Google Scholar
20. Abboud M, Gordon-Thomson C, Hoy AJ, Balaban S, Rybchyn MS, et al. (2014) Uptake of 25-hydroxyvitamin D by muscle and fat cells. J Steroid Biochem Mol Biol 144 Pt A: 232–236.
- View Article
- Google Scholar
21. Burild A, Frandsen HL, Poulsen M, Jakobsen J (2015) Tissue content of vitamin D3 and 25-hydroxy vitamin D3 in minipigs after cutaneous synthesis, supplementation and deprivation of vitamin D3. Steroids 98: 72–79. pmid:25725256
- View Article
- PubMed/NCBI
- Google Scholar
22. Casas E, Lippolis JD, Kuehn LA, Reinhardt TA (2015) Seasonal variation in vitamin D status of beef cattle reared in the central United States. Domest Anim Endocrinol 52: 71–74. pmid:25917139
- View Article
- PubMed/NCBI
- Google Scholar
23. Schutkowski A, Kramer J, Kluge H, Hirche F, Krombholz A, et al. (2013) UVB exposure of farm animals: study on a food-based strategy to bridge the gap between current vitamin D intakes and dietary targets. PLoS One 8: e69418. pmid:23894475
- View Article
- PubMed/NCBI
- Google Scholar
24. Kollias N, Ruvolo E Jr., Sayre RM (2011) The value of the ratio of UVA to UVB in sunlight. Photochem Photobiol 87: 1474–1475. pmid:21770951
- View Article
- PubMed/NCBI
- Google Scholar
25. Donald L. Boggs RAM, Matthew Doumit, Kelly Bruns (2006) Livestock and Carcasses: An integrated Approach to Evaluation, Grading, and Selection. Dubuque, IA: Kendall/Hunt Publishing Company.
26. Hollis BW, Kamerud JQ, Selvaag SR, Lorenz JD, Napoli JL (1993) Determination of vitamin D status by radioimmunoassay with an 125I-labeled tracer. Clinical Chemistry 39: 529–533. pmid:8448871
- View Article
- PubMed/NCBI
- Google Scholar
27. Roseland JM, Patterson KY, Andrews KW, Phillips KM, Phillips MM, et al. (2016) Interlaboratory Trial for Measurement of Vitamin D and 25-Hydroxyvitamin D [25(OH)D] in Foods and a Dietary Supplement Using Liquid Chromatography-Mass Spectrometry. J Agric Food Chem 64: 3167–3175. pmid:27045951
- View Article
- PubMed/NCBI
- Google Scholar
28. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, et al. (2011) The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab 96: 53–58. pmid:21118827
- View Article
- PubMed/NCBI
- Google Scholar
29. Vieth R (2004) Why the optimal requirement for Vitamin D3 is probably much higher than what is officially recommended for adults. J Steroid Biochem Mol Biol 89–90: 575–579. pmid:15225842
- View Article
- PubMed/NCBI
- Google Scholar
30. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, et al. (2011) Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 96: 1911–1930. pmid:21646368
- View Article
- PubMed/NCBI
- Google Scholar
31. Lowe LC, Guy M, Mansi JL, Peckitt C, Bliss J, et al. (2005) Plasma 25-hydroxy vitamin D concentrations, vitamin D receptor genotype and breast cancer risk in a UK Caucasian population. European Journal of Cancer 41: 1164–1169. pmid:15911240
- View Article
- PubMed/NCBI
- Google Scholar
32. Mohr SB, Gorham ED, Alcaraz JE, Kane CJ, Macera CA, et al. (2011) Serum 25-hydroxyvitamin D and prevention of breast cancer: Pooled analysis. Anticancer Research 31: 2939–2948. pmid:21868542
- View Article
- PubMed/NCBI
- Google Scholar
33. Grant WB (2015) 25-Hydroxyvitamin D and Breast Cancer, Colorectal Cancer, and Colorectal Adenomas: Case-Control versus Nested Case-Control Studies. ANTICANCER RESEARCH 35: 1154–1161.
- View Article
- Google Scholar
34. Miller JR, Dunn KW, Ciliberti LJ, Patel RD, Swanson BA (2016) Association of Vitamin D With Stress Fractures: A Retrospective Cohort Study. JOURNAL OF FOOT & ANKLE SURGERY 55: 117–120.
- View Article
- Google Scholar
35. Heaney RP (2013) Health is better at serum 25(OH)D above 30ng/mL. J Steroid Biochem Mol Biol 136: 224–228. pmid:23059471
- View Article
- PubMed/NCBI
- Google Scholar
36. Luxwolda MF, Kuipers RS, Kema IP, Janneke Dijck-Brouwer DA, Muskiet FAJ (2012) Traditionally living populations in East Africa have a mean serum 25-hydroxyvitamin D concentration of 115 nmol/l. British Journal of Nutrition 108: 1–5.
- View Article
- Google Scholar
37. Green TJ, Li W, Whiting SJ (2013) Strategies for Improving Vitamin D Status: Focus on Fortification. 247–260.
38. Kristensen HL, Rosenqvist E, Jakobsen J (2012) Increase of vitamin D-2 by UV-B exposure during the growth phase of white button mushroom (Agaricus bisporus). Food and Nutrition Research 56.
- View Article
- Google Scholar
39. O'Mahony L, Stepien M, Gibney MJ, Nugent AP, Brennan L (2011) The potential role of vitamin D enhanced foods in improving vitamin D status. Nutrients 3: 1023–1041. pmid:22292109
- View Article
- PubMed/NCBI
- Google Scholar
40. Burild A, Lauridsen C, Faqir N, Sommer HM, Jakobsen J (2016) Vitamin D3 and 25-hydroxyvitamin D3 in pork and their relationship to vitamin D status in pigs. J Nutr Sci 5: e3. pmid:26793309
- View Article
- PubMed/NCBI
- Google Scholar
41. Clausen I, Jakobsen J, Leth T, Ovesen L (2003) Vitamin D3 and 25-hydroxyvitamin D3 in raw and cooked pork cuts. Journal of Food Composition and Analysis 16: 575–585.
- View Article
- Google Scholar
42. Sayer RD, Wright AJ, Chen N, Campbell WW (2015) Dietary Approaches to Stop Hypertension diet retains effectiveness to reduce blood pressure when lean pork is substituted for chicken and fish as the predominant source of protein. Am J Clin Nutr.
- View Article
- Google Scholar

[ref1] 1. Turner AG, Anderson PH, Morris HA (2012) Vitamin D and bone health. Scand J Clin Lab Invest Suppl 243: 65–72.
View Article
Google Scholar

[2] View Article

[3] Google Scholar

[ref2] 2. Ahonen MH, Tenkanen L, Teppo L, Hakama M, Tuohimaa P (2000) Prostate Cancer Risk and Prediagnostic Serum 25-Hydroxyvitamin D Levels (Finland). Cancer Causes & Control 11: 847–852.
View Article
Google Scholar

[5] View Article

[6] Google Scholar

[ref3] 3. Bertone-Johnson ER, Chen WY, Holick MF, Hollis BW, Colditz GA, et al. (2005) Plasma 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D and risk of breast cancer. Cancer Epidemiol Biomarkers Prev 14: 1991–1997. pmid:16103450
View Article
PubMed/NCBI
Google Scholar

[8] View Article

[9] PubMed/NCBI

[10] Google Scholar

[ref4] 4. Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP (2007) Vitamin D and calcium supplementation reduces cancer risk: Results of a randomized trial. American Journal of Clinical Nutrition 85: 1586–1591. pmid:17556697
View Article
PubMed/NCBI
Google Scholar

[12] View Article

[13] PubMed/NCBI

[14] Google Scholar

[ref5] 5. Rimm EB, Liu Y, Hollis BW, Giovannucci E (2008) 25-Hydroxyvitamin D and Risk of Myocardial Infarction in Men: A Prospective Study. Archives of Internal Medicine 168: 1174–1180. pmid:18541825
View Article
PubMed/NCBI
Google Scholar

[16] View Article

[17] PubMed/NCBI

[18] Google Scholar

[ref6] 6. Mitri J, Muraru MD, Pittas AG (2011) Vitamin D and type 2 diabetes: a systematic review. Eur J Clin Nutr 65: 1005–1015. pmid:21731035
View Article
PubMed/NCBI
Google Scholar

[20] View Article

[21] PubMed/NCBI

[22] Google Scholar

[ref7] 7. Shen L, Ji HF (2015) Vitamin D deficiency is associated with increased risk of Alzheimer's disease and dementia: evidence from meta-analysis. Nutr J 14: 76. pmid:26231781
View Article
PubMed/NCBI
Google Scholar

[24] View Article

[25] PubMed/NCBI

[26] Google Scholar

[ref8] 8. Baggerly CA, Cuomo RE, French CB, Garland CF, Gorham ED, et al. (2015) Sunlight and Vitamin D: Necessary for Public Health. J Am Coll Nutr 34: 359–365. pmid:26098394
View Article
PubMed/NCBI
Google Scholar

[28] View Article

[29] PubMed/NCBI

[30] Google Scholar

[ref9] 9. Prentice A (2008) Vitamin D deficiency: a global perspective. Nutr Rev 66: S153–164. pmid:18844843
View Article
PubMed/NCBI
Google Scholar

[32] View Article

[33] PubMed/NCBI

[34] Google Scholar

[ref10] 10. Calvo MS, Whiting SJ (2003) Prevalence of Vitamin D Insufficiency in Canada and the United States: Importance to Health Status and Efficacy of Current Food Fortification and Dietary Supplement Use. Nutrition reviews 61: 107–113. pmid:12723644
View Article
PubMed/NCBI
Google Scholar

[36] View Article

[37] PubMed/NCBI

[38] Google Scholar

[ref11] 11. Macdonald HM (2013) Contributions of sunlight and diet to vitamin D status. Calcif Tissue Int 92: 163–176. pmid:23001438
View Article
PubMed/NCBI
Google Scholar

[40] View Article

[41] PubMed/NCBI

[42] Google Scholar

[ref12] 12. Holick MF (2007) Vitamin D Deficiency. The New England Journal of Medicine 357: 266–281. pmid:17634462
View Article
PubMed/NCBI
Google Scholar

[44] View Article

[45] PubMed/NCBI

[46] Google Scholar

[ref13] 13. Holick MF, Chen TC, Lu Z, Sauter E (2007) Vitamin D and skin physiology: a D-lightful story. J Bone Miner Res 22 Suppl 2: V28–33.
View Article
Google Scholar

[48] View Article

[49] Google Scholar

[ref14] 14. Moore CE, Murphy MM, Holick MF (2005) Vitamin D intakes by children and adults in the United States differ among ethnic groups. The Journal of nutrition 135: 2478–2485. pmid:16177216
View Article
PubMed/NCBI
Google Scholar

[51] View Article

[52] PubMed/NCBI

[53] Google Scholar

[ref15] 15. US Department of Agriculture ARS, Nutrient Data Library USDA National Nutrient Database for Standard Reference.

[ref16] 16. Heaney RP, Horst RL, Cullen DM, Armas LAG (2009) Vitamin D3 Distribution and Status in the Body. Journal of the American College of Nutrition 28: 252–256. pmid:20150598
View Article
PubMed/NCBI
Google Scholar

[56] View Article

[57] PubMed/NCBI

[58] Google Scholar

[ref17] 17. Heaney RP, Laura AGA, French C (2013) All-Source Basal Vitamin D Inputs Are Greater Than Previously Thought and Cutaneous Inputs Are Smaller. The Journal of Nutrition 143: 571. pmid:23514768
View Article
PubMed/NCBI
Google Scholar

[60] View Article

[61] PubMed/NCBI

[62] Google Scholar

[ref18] 18. Taylor CL, Patterson KY, Roseland JM, Wise SA, Merkel JM, et al. (2014) Including food 25-hydroxyvitamin D in intake estimates may reduce the discrepancy between dietary and serum measures of vitamin D status. J Nutr 144: 654–659. pmid:24623845
View Article
PubMed/NCBI
Google Scholar

[64] View Article

[65] PubMed/NCBI

[66] Google Scholar

[ref19] 19. Brouwer DAJ, Beek JV, Ferwerda H, Brugman AM, Klis FRMvd, et al. (1998) Rat adipose tissue rapidly accumulates and slowly releases an orally-administered high vitamin D dose. British Journal of Nutrition 79: 527–532. pmid:9771340
View Article
PubMed/NCBI
Google Scholar

[68] View Article

[69] PubMed/NCBI

[70] Google Scholar

[ref20] 20. Abboud M, Gordon-Thomson C, Hoy AJ, Balaban S, Rybchyn MS, et al. (2014) Uptake of 25-hydroxyvitamin D by muscle and fat cells. J Steroid Biochem Mol Biol 144 Pt A: 232–236.
View Article
Google Scholar

[72] View Article

[73] Google Scholar

[ref21] 21. Burild A, Frandsen HL, Poulsen M, Jakobsen J (2015) Tissue content of vitamin D3 and 25-hydroxy vitamin D3 in minipigs after cutaneous synthesis, supplementation and deprivation of vitamin D3. Steroids 98: 72–79. pmid:25725256
View Article
PubMed/NCBI
Google Scholar

[75] View Article

[76] PubMed/NCBI

[77] Google Scholar

[ref22] 22. Casas E, Lippolis JD, Kuehn LA, Reinhardt TA (2015) Seasonal variation in vitamin D status of beef cattle reared in the central United States. Domest Anim Endocrinol 52: 71–74. pmid:25917139
View Article
PubMed/NCBI
Google Scholar

[79] View Article

[80] PubMed/NCBI

[81] Google Scholar

[ref23] 23. Schutkowski A, Kramer J, Kluge H, Hirche F, Krombholz A, et al. (2013) UVB exposure of farm animals: study on a food-based strategy to bridge the gap between current vitamin D intakes and dietary targets. PLoS One 8: e69418. pmid:23894475
View Article
PubMed/NCBI
Google Scholar

[83] View Article

[84] PubMed/NCBI

[85] Google Scholar

[ref24] 24. Kollias N, Ruvolo E Jr., Sayre RM (2011) The value of the ratio of UVA to UVB in sunlight. Photochem Photobiol 87: 1474–1475. pmid:21770951
View Article
PubMed/NCBI
Google Scholar

[87] View Article

[88] PubMed/NCBI

[89] Google Scholar

[ref25] 25. Donald L. Boggs RAM, Matthew Doumit, Kelly Bruns (2006) Livestock and Carcasses: An integrated Approach to Evaluation, Grading, and Selection. Dubuque, IA: Kendall/Hunt Publishing Company.

[ref26] 26. Hollis BW, Kamerud JQ, Selvaag SR, Lorenz JD, Napoli JL (1993) Determination of vitamin D status by radioimmunoassay with an 125I-labeled tracer. Clinical Chemistry 39: 529–533. pmid:8448871
View Article
PubMed/NCBI
Google Scholar

[92] View Article

[93] PubMed/NCBI

[94] Google Scholar

[ref27] 27. Roseland JM, Patterson KY, Andrews KW, Phillips KM, Phillips MM, et al. (2016) Interlaboratory Trial for Measurement of Vitamin D and 25-Hydroxyvitamin D [25(OH)D] in Foods and a Dietary Supplement Using Liquid Chromatography-Mass Spectrometry. J Agric Food Chem 64: 3167–3175. pmid:27045951
View Article
PubMed/NCBI
Google Scholar

[96] View Article

[97] PubMed/NCBI

[98] Google Scholar

[ref28] 28. Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, et al. (2011) The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab 96: 53–58. pmid:21118827
View Article
PubMed/NCBI
Google Scholar

[100] View Article

[101] PubMed/NCBI

[102] Google Scholar

[ref29] 29. Vieth R (2004) Why the optimal requirement for Vitamin D3 is probably much higher than what is officially recommended for adults. J Steroid Biochem Mol Biol 89–90: 575–579. pmid:15225842
View Article
PubMed/NCBI
Google Scholar

[104] View Article

[105] PubMed/NCBI

[106] Google Scholar

[ref30] 30. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, et al. (2011) Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 96: 1911–1930. pmid:21646368
View Article
PubMed/NCBI
Google Scholar

[108] View Article

[109] PubMed/NCBI

[110] Google Scholar

[ref31] 31. Lowe LC, Guy M, Mansi JL, Peckitt C, Bliss J, et al. (2005) Plasma 25-hydroxy vitamin D concentrations, vitamin D receptor genotype and breast cancer risk in a UK Caucasian population. European Journal of Cancer 41: 1164–1169. pmid:15911240
View Article
PubMed/NCBI
Google Scholar

[112] View Article

[113] PubMed/NCBI

[114] Google Scholar

[ref32] 32. Mohr SB, Gorham ED, Alcaraz JE, Kane CJ, Macera CA, et al. (2011) Serum 25-hydroxyvitamin D and prevention of breast cancer: Pooled analysis. Anticancer Research 31: 2939–2948. pmid:21868542
View Article
PubMed/NCBI
Google Scholar

[116] View Article

[117] PubMed/NCBI

[118] Google Scholar

[ref33] 33. Grant WB (2015) 25-Hydroxyvitamin D and Breast Cancer, Colorectal Cancer, and Colorectal Adenomas: Case-Control versus Nested Case-Control Studies. ANTICANCER RESEARCH 35: 1154–1161.
View Article
Google Scholar

[120] View Article

[121] Google Scholar

[ref34] 34. Miller JR, Dunn KW, Ciliberti LJ, Patel RD, Swanson BA (2016) Association of Vitamin D With Stress Fractures: A Retrospective Cohort Study. JOURNAL OF FOOT & ANKLE SURGERY 55: 117–120.
View Article
Google Scholar

[123] View Article

[124] Google Scholar

[ref35] 35. Heaney RP (2013) Health is better at serum 25(OH)D above 30ng/mL. J Steroid Biochem Mol Biol 136: 224–228. pmid:23059471
View Article
PubMed/NCBI
Google Scholar

[126] View Article

[127] PubMed/NCBI

[128] Google Scholar

[ref36] 36. Luxwolda MF, Kuipers RS, Kema IP, Janneke Dijck-Brouwer DA, Muskiet FAJ (2012) Traditionally living populations in East Africa have a mean serum 25-hydroxyvitamin D concentration of 115 nmol/l. British Journal of Nutrition 108: 1–5.
View Article
Google Scholar

[130] View Article

[131] Google Scholar

[ref37] 37. Green TJ, Li W, Whiting SJ (2013) Strategies for Improving Vitamin D Status: Focus on Fortification. 247–260.

[ref38] 38. Kristensen HL, Rosenqvist E, Jakobsen J (2012) Increase of vitamin D-2 by UV-B exposure during the growth phase of white button mushroom (Agaricus bisporus). Food and Nutrition Research 56.
View Article
Google Scholar

[134] View Article

[135] Google Scholar

[ref39] 39. O'Mahony L, Stepien M, Gibney MJ, Nugent AP, Brennan L (2011) The potential role of vitamin D enhanced foods in improving vitamin D status. Nutrients 3: 1023–1041. pmid:22292109
View Article
PubMed/NCBI
Google Scholar

[137] View Article

[138] PubMed/NCBI

[139] Google Scholar

[ref40] 40. Burild A, Lauridsen C, Faqir N, Sommer HM, Jakobsen J (2016) Vitamin D3 and 25-hydroxyvitamin D3 in pork and their relationship to vitamin D status in pigs. J Nutr Sci 5: e3. pmid:26793309
View Article
PubMed/NCBI
Google Scholar

[141] View Article

[142] PubMed/NCBI

[143] Google Scholar

[ref41] 41. Clausen I, Jakobsen J, Leth T, Ovesen L (2003) Vitamin D3 and 25-hydroxyvitamin D3 in raw and cooked pork cuts. Journal of Food Composition and Analysis 16: 575–585.
View Article
Google Scholar

[145] View Article

[146] Google Scholar

[ref42] 42. Sayer RD, Wright AJ, Chen N, Campbell WW (2015) Dietary Approaches to Stop Hypertension diet retains effectiveness to reduce blood pressure when lean pork is substituted for chicken and fish as the predominant source of protein. Am J Clin Nutr.
View Article
Google Scholar

[148] View Article

[149] Google Scholar

Figures

Abstract

Introduction

Materials and methods

Serum 25(OH)D via RIA

25(OH)D2/25(OH)D3 and vitamin D2/vitamin D3 in adipose and meat/tissue

Statistical procedures

Results

Body mass, composition and weight gain

UV exposure

Serum 25(OH)D3

Tissue vitamin D

Loin tissue.

Subcutaneous adipose.

Association between serum 25(OH)D3 and tissue concentrations

Discussion

Supporting information

S1 Table. Body weight and body composition in the subgroup of sun-exposed and control pigs selected for tissue analysis.

S1 Fig. Effects of sun exposure on vitamin D status.

S2 Fig. Effects of sun exposure on vitamin D concentrations in loin tissue.

Acknowledgments

References

25(OH)D₂/25(OH)D₃ and vitamin D₂/vitamin D₃ in adipose and meat/tissue

Serum 25(OH)D₃

Association between serum 25(OH)D₃ and tissue concentrations