Does Alcohol Lower Vitamin D Levels
Abstract
The objective of this study was to evaluate the effect of 8 weeks of no alcohol, low (1 drink or 15 g/day) and moderate (2 drinks or 30 g/day) alcohol consumption on markers of bone health: fasting serum 25-hydroxy vitamin D (25(OH)D), osteocalcin (OC), bone-specific alkaline phosphatase (BSAP), urine deoxypyridinoline (DPD) and helical peptide (HP) in postmenopausal women (n=51). Compared with no alcohol, 1 or 2 drinks/day for 8 weeks had no significant impact on any of the bone markers. Within each alcohol group, obese women had significantly lower serum 25(OH)D and higher DPD concentrations than normal weight women. Season significantly affected the concentrations of serum 25(OH)D, but there was no significant interaction between alcohol and season on serum 25(OH)D concentrations. Low or moderate alcohol consumption for 8 weeks had no significant impact on markers of bone health in postmenopausal women.
Introduction
Vitamin D has an important role in maintaining bone health by acting to increase calcium and phosphorus absorption as needed, and since alcohol consumption is implicated in bone health in women, an important question arises as to whether alcohol modulates vitamin D concentrations. There are no published data from controlled feeding trials on the role of low to moderate alcohol consumption on serum 25-hydroxy vitamin D (25(OH)D) or bone turnover markers. In this report, we examined the effect of low to moderate alcohol ingestion on serum 25(OH)D and bone turnover markers in postmenopausal women.
Subjects and methods
The Women's Alcohol Study
The postmenopausal WAS (Women's Alcohol Study), including eligibility criteria, controlled diet and feeding, and biological sample collection, has previously been described.1 The WAS used a crossover design in which 65 healthy postmenopausal women were randomly assigned to zero (0 g), 15 mg and 30 mg per day alcohol for 8 weeks each and then rotated through the other treatments (three 8-week diet periods) in random order. A 2- to 5-week washout period occurred between alcohol treatments during which time the women consumed no alcohol. Participants consumed prepared diets while receiving the three alcohol treatments. Fifty-three women successfully completed the trial. Blood samples were collected at baseline, week 4 and week 8 of the study and sera were stored at −80 °C. Participants gave consent before entering the study and were compensated for their participation.
Assessment of serum 25(OH)D
Serum 25(OH)D was measured using ELISA kits (Immunodiagnostics Systems, Inc.) according to the manufacturer's instructions. The assays were conducted in duplicate and nine quality control samples were included. The precision of the quality control samples was as follows: intra-assay: 3% coefficient of variation (CV); inter-assay: 18% CV.
Assessment of bone turnover markers
Serum osteocalcin (OC) was analyzed by an enzyme immunoassay kit with within-run CVs of 4.8–10.0% and between-run CVs of 4.8–9.8% (Metra OC, Quidel Corporation, San Diego, CA, USA).
Bone-specific alkaline phosphatase (BSAP) was analyzed by an enzyme immunoassay kit with within-run CVs of 3.9–5.8% and between-run CVs of 5.0–7.6% (Metra EIA BAP, Quidel Corporation).
Urinary helical peptide (HP) was analyzed by an enzyme immunoassay kit with within-run CVs of 4.0–8.1% and between-run CVs of 7.3–16.9% (Metra Helical Peptide EIA Kit, Quidel Corporation).
Urinary deoxypyridinoline (DPD) was analyzed by an enzyme immunoassay kit with within-run CVs of 4.3–8.4% and between-run CVs of 3.1–4.8% (Metra Deoxypyridinoline EIA Kit, Quidel Corporation).
Statistical analyses
Serum 25(OH)D and bone turnover marker concentrations were transformed using the Box-Cox transformation to make them normally distributed. Mixed models were fit to the transformed 25(OH)D concentrations and bone turnover markers adjusted for race, age in four categories defined by quartiles of the ages (⩽53.9, 54–58.2, 58.3–63.6, >63.6), body mass index (BMI), season (in four categories: season 1 (January to March), season 2 (April to June), season 3 (July to September) and season 4 (October to December) and baseline values of each analyte using restricted maximum likelihood. In analyses that assessed the impact of BMI on 25(OH)D and bone turnover marker concentrations, we fit separate linear regression models to each alcohol category, for 4 and 8 weeks; all were adjusted for age in categories and race, if appropriate. For the trend test, BMI categories were coded as 0, 1 and 2, and a Wald P-value was calculated.
In analyses that assessed the impact of season on 25(OH)D concentrations, we fit separate linear regression models to each alcohol category; all were adjusted for age in categories, BMI and race, if appropriate. P-values for heterogeneity for alcohol effects by season were computed by including an interaction term of season with alcohol group in a model that was fit to all observations jointly. For this test, season categories were coded as 1, 2, 3, 4 and assumed to follow a trend. Statistical analyses were conducted using SAS v 9.1 (SAS Institute, Cary, NC, USA).
Results
Characteristics of the study participants with baseline 25(OH)D and bone turnover marker measurements are shown in Table 1. Their ages ranged from 49.2 to 78.8 years, with a median of 58 years. BMI ranged from 17.7 to 42.5, with a median of 26.9. The majority of the participants were white (75%), 22% were black and 4% were Asian. The women were an educated group, 56% reported college or graduate school education. Eighty-two percent of the women had natural menopause while eighteen percent had a hysterectomy. At baseline, which represents the free-living state, there was wide variation in serum 25(OH)D concentrations overall and in whites and blacks. Similar observations were made for the bone turnover markers (OC, BSAP, DPD and HP).
Full size table
Table 2 shows participants' fasting mean serum 25(OH)D concentrations on placebo and percent difference after consumption of 15 and 30 g/day alcohol. The data indicate that low (15 g/day) to moderate (30 g/day) alcohol consumption vs no alcohol for either 4 or 8 weeks did not significantly change serum 25(OH)D concentrations or biochemical markers of bone turnover (OC, BSAP, DPD and HP) among all women or by race. However, for each level of alcohol, increased BMI was associated with decreased 25(OH)D levels (data not shown).
Full size table
In our analysis, we found that season affected serum 25(OH)D levels in the women. However, we found no significant interaction between season and alcohol after 8 weeks of intervention (data not shown).
Discussion
Main findings
We found that low to moderate alcohol consumption for up to 8 weeks had no significant effect on fasting concentrations of serum 25(OH)D or other biochemical markers of bone turnover in postmenopausal women.
Findings in relation to other literature
To our knowledge, this is the first controlled feeding study to examine the effects of low to moderate alcohol consumption on markers of bone health in postmenopausal women. A cross-sectional study reported positive associations between moderate alcohol and serum vitamin D.2 In that study, information about alcohol and diet were collected using questionnaires and this may have resulted in misclassification.2 Another study reported that short-term (14 days) moderate alcohol intake lowered bone turnover markers in postmenopausal women.3 Our finding that obesity is associated with low serum 25(OH)D is consistent with previous findings from observational studies.4, 5, 6
Strengths and weaknesses
Our study had strengths and limitations. It was the first study to utilize controlled feeding conditions to investigate the role of alcohol on markers of bone health in postmenopausal women, all participants were healthy postmenopaual women who did not smoke and were not on hormone replacement therapy. Since the primary goal of the parent study (WAS) was to investigate the effect of alcohol on sex hormones, the design did not consider sun exposure. For the current ancillary study, this is a limitation since sun exposure is a major determinant of 25(OH)D status. We were able to use data on season as a surrogate for sun exposure and found, as expected, that season affected serum 25(OH)D concentrations, but that season did not influence the effect of alcohol on serum vitamin D concentrations. Another potentially important limitation of the study is that the duration of alcohol intervention was only 8 weeks.
Conclusion
In conclusion, we showed that daily consumption of low to moderate alcohol for up to 8 weeks under controlled dietary conditions had no significant effects on serum 25(OH)D concentrations or other biochemical markers of bone turnover in postmenopausal women.
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Acknowledgements
This study was supported by NIH and the National Cancer Institute Interagency agreement Y1-SC-8012 and the Intramural Research Program.
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Competing interests
The authors declare no conflict of interest.
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Mahabir, S., Baer, D., Pfeiffer, R. et al. Low to moderate alcohol consumption on serum vitamin D and other indicators of bone health in postmenopausal women in a controlled feeding study. Eur J Clin Nutr 68, 1267–1270 (2014). https://doi.org/10.1038/ejcn.2014.191
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DOI : https://doi.org/10.1038/ejcn.2014.191
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Does Alcohol Lower Vitamin D Levels
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