Vitamin D is needed for optimal bone health and muscle strength and may regulate processes such as inflammation and immunity (1). Vitamin D supplementation resulting in optimal serum concentration may have beneficial health effects for multiple diseases and is under evaluation for therapy in many clinical settings (2–5). Kemp et al (6) raised a concern regarding vitamin D supplementation for people with previous lead exposure. They showed that seasonal variations in lead levels were associated with changes in vitamin D in young urban children, with both occurring at higher levels in the summer; however, Kersey et al (7) found no association between serum vitamin D and blood lead concentration in low-income children. Additionally, Jackson et al (8) demonstrated an inverse association between blood lead levels and vitamin D supplementation, and increased blood lead levels during periods of increased bone turnover.
Given the discordance of these previous findings, the objective of the study was to determine the safety regarding lead toxicity during 12 weeks of high-dose vitamin D3 supplementation in children and young adults with human immunodeficiency virus (HIV).
Study participants ages 8 to 24 years were recruited from the Special Immunology Family Care Clinic and the Adolescent Health Care Clinic at The Children's Hospital of Philadelphia (CHOP), and from the Jonathan Lax Center. This is a secondary analysis of a larger study to determine the safety and efficacy of high-dose vitamin D3 supplementation in children and young adults with HIV. Because it is the first high-dose vitamin D3 supplementation study in this population, we chose to focus initially on older children and adolescents to demonstrate safety. The present study was approved by the institutional review board at CHOP. Informed consent was obtained from young adult participants 18 years or older and from emancipated minors (younger than 18 years). Assent was obtained from the other participants younger than 18 years with consent from their parents/guardians. Participants’ racial and ethnic status was obtained via self-report. After enrollment, subjects were randomized to a vitamin D3 (cholecalciferol) dose of either 4000 (two 2000-IU capsules [NSI, Vitacost, Boca Raton, FL]) or 7000 IU/day (one 2000-IU capsule [NSI] and one 5000-IU supplement [Now Foods, NOW Health Group, Bloomingdale, IL]) with follow-up visits at 6 and 12 weeks. Doses of all supplements were confirmed by an independent laboratory (Tampa Bay Analytical Research, Inc [Largo, FL]). For analysis, subjects were stratified by age (8–12.9, 13–18.9, and 19–24.9 years). At all visits, serum 25-hydroxy vitamin D (25D) was measured using a liquid chromatography-tandem mass spectrometer, and whole-blood lead concentration using an inductively coupled plasma mass spectrometry by CHOP clinical laboratory. For the purpose of the present study, vitamin D status was categorized as deficient, insufficient, and sufficient based upon serum 25D concentrations <50, 50 to 79, and ≥80 nmol/L (<20, 20–31, and ≥32 ng/mL), respectively. The goal of 80 nmol/L was higher than the usual target for healthy people. The cutoff values were based on the ability of the body to regulate intestinal calcium absorption and represent benchmark values for evaluating the immunological effect of vitamin D supplementation (9–11).
Weight was measured to the nearest 0.1 kg using a digital scale (Scaltronix, White Plains, NY) and height to the nearest 0.1 cm using a stadiometer (Holtain, Crymych, UK). Age- and sex-specific standard deviation (SD) scores (z scores) for weight, height, and body mass index were calculated (12). Seasons were defined as summer (June, July, August), fall (September, October, November), winter (December, January, February), and spring (March, April, May). Adherence to vitamin D3 study supplements was assessed via final pill count and multiple telephone calls and questionnaires.
Descriptive statistics were calculated for the total sample at 3 visits (baseline, 6 weeks, and 12 weeks). Means, SDs, and medians and ranges were used to summarize continuous variables, and proportions for categorical variables. Potential trends in whole-blood lead, serum 25D, and growth and nutritional status over time were assessed using paired Student t tests or Wilcoxon rank tests depending upon skewness of the data. χ 2 tests and Fisher exact tests were used to assess differences over time for categorical variables. Pearson correlation coefficients or Spearman rank correlations, as appropriate, were performed to test for significant associations between blood lead and serum 25D status, age, growth, and nutritional status at each visit.
Longitudinal mixed effects analysis was used to assess time trends in blood lead and potential differences among the 3 age groups and among vitamin D3 supplementation dose groups (4000 vs 7000 IU/day) in these trends (using age group × time or dose group × time interaction terms). Study data were collected and managed using REDCap (Research Electronic Data Capture, Vanderbilt University, Nashville, TN) tools hosted at CHOP (13). All data were analyzed using STATA 9.0 (STATACorp, College Station, TX). Statistical significance was defined as P value <0.05, and data are presented as mean ± SD (unless otherwise indicated).
A total of 44 subjects with HIV ages 18.7 ± 4.7 years were enrolled and 42 completed the study. At baseline (Table 1), participants’ characteristics showed altered immune but normal nutritional status. Table 2 presents serum 25D, blood lead, and serum alkaline phosphatase during 12 weeks of vitamin D3 supplementation. At baseline, serum 25D was 48.3 ± 18.6 nmol/L with 50% of the subjects <50 nmol/L. A significant increase from baseline in serum 25D was evident at both 6 (114.8 ± 35.6 nmol/L) and 12 weeks (118.0 ± 46.5 nmol/L) and 81% of subjects achieved sufficient 25D concentrations (≥80 nmol/L) by 12 weeks. The whole-blood lead was low at baseline and no subject had blood lead >5 μg/dL. Lead values did not change and serum alkaline phosphatase remained stable for 12 weeks. Serum 25D was low at baseline (11.0 to 84.0 nmol/L). Serum 25D increased by 57.1 ± 37.8 nmol/L after 6 weeks and 62.1 ± 46.3 nmol/L after 12 weeks of vitamin D3 supplementation in the 4000-IU/day group. In the 7000-IU/day group, the increase was 77.2 ± 39.1 nmol/L after 6 weeks and 77.4 ± 60.4 nmol/L after 12 weeks of supplementation. No difference was observed in the change in whole-blood lead over time between subjects who received 4000 versus 7000 IU of vitamin D3.
Figure 1 presents the whole-blood lead levels over time by age group where subjects were grouped by age (8–12.9 years, n = 8; 13–18.9 years, n = 8; and 19–24.9 years, n = 28). Although the whole-blood lead remained <5 μg/dL, a significantly higher level at baseline and 12 weeks was found in the youngest age group when compared with the older subjects (P ≤ 0.02). Whole-blood lead was not correlated with 25D at baseline; however, blood lead was significantly negatively correlated (r = −0.38, P = 0.014) with 25D after 12 weeks of supplementation evaluating all subjects together. Subjects enrolled in winter and spring had significantly lower serum 25D at baseline than those enrolled in summer and fall (38.5 ± 17.7 vs 55.1 ± 16.2 nmol/L, P = 0.003), but both groups had comparable whole-blood lead levels at baseline. Increase in serum 25D after 12 weeks of supplementation was significantly greater in the subjects enrolled during winter and spring compared with the others enrolled during summer and fall (100.7 ± 51.6 vs 48.7 ± 44.9 nmol/L, P = 0.001). This increase in 25D was accompanied by no change in whole-blood lead level in the group of all subjects. For participants enrolled in winter and spring who had robust increases in 25D during the subsequent 12 weeks (into spring and summer) whole-blood lead decreased (−0.12 ± 0.32 μg/dL, P = 0.04).
Adherence was assessed via patient report in 42 subjects (by telephone contact and in-person questionnaires), and via pill count in 31 subjects. Adherence assessed with pill count was 87% for the 4000-IU dose and 93% for the 7000-IU dose. Adherence assessed with telephone calls was 94% for both doses. Adherence assessed with questionnaires was 92% for the 4000-IU dose and 90% for the 7000-IU dose. No correlation was found between adherence to supplementation and whole-blood lead level.
Increased serum 25D concentration did not result in increased whole-blood lead in this group of children and young adults with HIV living in the northeast urban United States, 75% of whom were African American. The more robust increase in serum 25D after 12 weeks of vitamin D3 supplementation for participants enrolled during winter and spring was accompanied by a decrease in whole-blood lead concentration. Whole-blood lead did not differ between those receiving 4000 versus 7000 IU of vitamin D3. These data are likely generalizable outside HIV care because there is no known effect of HIV on lead metabolism, and limited effect on vitamin D metabolism.
Previous work included Kemp et al (6) who reported an increase in blood lead during summer, which was significantly associated with an increase in serum 25D in urban African American and Hispanic children ages 4 to 8 years in Newark, NJ. Our youngest participants were 8 years of age, which may be an important consideration because higher blood levels are mainly observed in younger children. Data from the National Report on Human Exposure to Environmental Chemicals 1999–2008 showed that children ages 1 to 5 years had a higher blood lead level compared with other age groups (14). Kemp et al (6) also reported an increased blood lead during summer in the subgroup of 1- to 3-year-old children without a significant increase in serum 25D. Kersey et al (7) studied healthy toddlers and children younger than 6 years in Minneapolis, MN, and found no association between vitamin D and lead levels. We did not find a positive association between 25D and blood lead and there was no increase in blood lead during the summer months in our 8- to 24-year-old sample of subjects. Jackson et al (8) found that the use of vitamin D supplements (by report) in the last month was associated with significantly lower adjusted mean blood lead levels in postmenopausal women, suggesting that 1 month of vitamin D supplementation per se did not increase blood lead in these women. The association between high-dose vitamin D3 supplementation and blood lead in contemporary groups of infants and preschool children remains to be evaluated.
The relation of serum vitamin D and whole-blood lead is possibly influenced by growth and/or calcium homeostasis in some children and adults. More than 95% of body lead is located in bone (15). Mobilization of bone lead can be increased during periods of higher bone turnover including childhood growth (16,17). Low dietary intake of vitamin D and calcium are known risk factors for high bone lead levels (18). Vitamin D enhances calcium absorption and calcium competes with lead for gut-binding sites (19). Animal studies have shown an inverse relation between calcium intake and lead levels (20,21). This inverse relation was also documented in pregnant women (22), and calcium supplementation during pregnancy was associated with reductions in blood lead (23).
The United States has experienced dramatic decreases in environmental lead exposure since 1980 (24). Blood lead levels declined in all age groups during the 1999–2008 survey period (25). Kemp et al (6) reported seasonal blood lead variations in 2001 and 2002, whereas the study of Kersey et al (7) and the present study were more recent. The participants of the 3 studies were from Newark, Minneapolis, and Philadelphia. Although all 3 are urban, northern US cities with socioeconomically similar populations, differences in environmental exposures and in adherence to lead abatement may exist. Of note, there were still 130 children between 7 and 16 years of age with confirmed elevated blood lead level (>10 μg/dL) in Pennsylvania in 2010 (year of our study), 66 of whom lived in Philadelphia (26).
These results demonstrate that in this sample of children and young adults ages 8 to 24 with HIV and low baseline blood lead levels, 12 weeks of high-dose vitamin D3 supplementation resulted in significantly increased serum 25D with no concomitant change in whole-blood lead concentration. These data provide safety information when considering higher-dose vitamin D intervention.
We thank the subjects, parents, and other care providers for their participation and cooperation in this study, the CHOP Special Immunology Family Care Clinic, the Adolescent Health Care Clinic, the Jonathan Lax Center, the CHOP Clinical and Translational Research Center, and Alia Tanko and Savannah Knell.
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Keywords:Copyright 2013 by ESPGHAN and NASPGHAN
blood lead; children; HIV/AIDS; nutrition; vitamin D supplementation