Nutrition, Immunosenescence, and Infectious Disease: An Overview of the Scientific Evidence on Micronutrients and on Modulation of the Gut Microbiota.

The immune system is key to host defense against pathogenic organisms. Aging is associated with changes in the immune system, with a decline in protective components (immunosenescence), increasing susceptibility to infectious disease, and a chronic elevation in low-grade inflammation (inflammaging), increasing the risk of multiple noncommunicable diseases. Nutrition is a determinant of immune cell function and of the gut microbiota. In turn, the gut microbiota shapes and controls the immune and inflammatory responses. Many older people show changes in the gut microbiota. Age-related changes in immune competence, low-grade inflammation, and gut dysbiosis may be interlinked and may relate, at least in part, to age-related changes in nutrition. A number of micronutrients (vitamins C, D, and E and zinc and selenium) play roles in supporting the function of many immune cell types. Some trials report that providing these micronutrients as individual supplements can reverse immune deficits in older people and/or in those with insufficient intakes. There is inconsistent evidence that this will reduce the risk or severity of infections including respiratory infections. Probiotic, prebiotic, or synbiotic strategies that modulate the gut microbiota, especially by promoting the colonization of lactobacilli and bifidobacteria, have been demonstrated to modulate some immune and inflammatory biomarkers in older people and, in some cases, to reduce the risk and severity of gastrointestinal and respiratory infections, although, again, the evidence is inconsistent. Further research with well-designed and well-powered trials in at-risk older populations is required to be more certain about the role of micronutrients and of strategies that modify the gut microbiota-host relationship in protecting against infection, especially respiratory infection.

Daily preventive zinc supplementation increases the antibody response against pathogenic Escherichia coli in children with zinc insufficiency: a randomised controlled trial.

Zinc deficiency impairs the antibody-mediated immune response and is common in children from lower-income countries. This study aimed to investigate the impact of different zinc supplementation regimens (7, 10 or 20 mg/day elemental zinc)-therapeutic dispersible zinc tablets (TZ), daily multiple micronutrient powder (MNP), daily preventive zinc tablets (PZ) and placebo powder (control)-and compare between baseline and endline antibody production against pathogenic Escherichia coli in Laotian children (aged 6-23 months). Fifty representative plasma samples of each treatment group were randomly selected from 512 children to determine anti-E. coli IgG antibody levels and avidity. Of the 200 children, 78.5% had zinc deficiency (plasma zinc concentration < 65 µg/dL) and 40% had anaemia before receiving zinc supplementation. aAfter receiving the TZ, MNP or PZ regimen, the plasma anti-E. coli IgG levels were significantly increased compared with baseline; the effect on the antibody level was more pronounced in children with zinc deficiency. Interestingly, there was increased anti-E. coli IgG avidity in the control and PZ groups. This study suggests that PZ might be the optimal zinc supplementation regimen to increase both the quantity and quality of antibody responses in children with zinc deficiency. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT02428647 (NCT02428647, 29/04/2015).

High-Dose Neonatal Vitamin A Supplementation to Bangladeshi Infants Increases the Percentage of CCR9-Positive Treg Cells in Infants with Lower Birthweight in Early Infancy, and Decreases Plasma sCD14 Concentration and the Prevalence of Vitamin A Deficiency at Two Years of Age.

BACKGROUND: Vitamin A (VA) stores are low in early infancy and may impair development of the immune system. OBJECTIVE: This study determined if neonatal VA supplementation (VAS) affects the following: 1) development of regulatory T (Treg) cells; 2) chemokine receptor 9 (CCR9) expression, which directs mucosal targeting of immune cells; and 3) systemic endotoxin exposure as indicated by changed plasma concentrations of soluble CD14 (sCD14). Secondarily, VA status, growth, and systemic inflammation were investigated. METHODS: In total, 306 Bangladeshi infants were randomly assigned to receive 50,000 IU VA or placebo (PL) within 48 h of birth, and immune function was assessed at 6 wk, 15 wk, and 2 y. Primary outcomes included the following: 1) peripheral blood Treg cells; 2) percentage of Treg, T, and B cells expressing CCR9; and 3) plasma sCD14. Secondary outcomes included the following: 4) VA status measured using the modified relative dose-response (MRDR) test and plasma retinol; 5) infant growth; and 6) plasma C-reactive protein (CRP). Statistical analysis identified group differences and interactions with sex and birthweight. RESULTS: VAS increased (P = 0.004) the percentage of CCR9+ Treg cells (13.2 ± 1.37%) relative to PL (9.17 ± 1.15%) in children below the median birthweight but had the opposite effect (P = 0.04) in those with higher birthweight (VA, 9.13 ± 0.89; PL, 12.1 ± 1.31%) at 6 and 15 wk (values are combined mean ± SE). VAS decreased (P = 0.003) plasma sCD14 (1.56 ± 0.025 mg/L) relative to PL (1.67 ± 0.032 mg/L) and decreased (P = 0.034) the prevalence of VA deficiency (2.3%) relative to PL (9.2%) at 2 y. CONCLUSIONS: Neonatal VAS enhanced mucosal targeting of Treg cells in low-birthweight infants. The decreased systemic exposure to endotoxin and improved VA status at 2 y may have been due to VA-mediated improvements in gut development resulting in improved barrier function and nutrient absorption. This trial was registered at clinicaltrials.gov as NCT01583972 and NCT02027610.

Daily Preventive Zinc Supplementation Decreases Lymphocyte and Eosinophil Concentrations in Rural Laotian Children from Communities with a High Prevalence of Zinc Deficiency: Results of a Randomized Controlled Trial.

BACKGROUND: Zinc deficiency impairs immune function and is common among children in South-East Asia. OBJECTIVES: The effect of zinc supplementation on immune function in young Laotian children was investigated. METHODS: Children (n = 512) aged 6-23 mo received daily preventive zinc tablets (PZ; 7 mg Zn/d), daily multiple micronutrient powder (MNP; 10 mg Zn/d, 6 mg Fe/d, plus 13 other micronutrients), therapeutic dispersible zinc tablets only in association with diarrhea episodes (TZ; 20 mg Zn/d for 10 d after an episode), or daily placebo powder (control). These interventions continued for 9 mo. Cytokine production from whole blood cultures, the concentrations of T-cell populations, and a complete blood count with differential leukocyte count were measured at baseline and endline. Endline means were compared via ANCOVA, controlling for the baseline value of the outcome, child age and sex, district, month of enrollment, and baseline zinc status (below, or above or equal to, the median plasma zinc concentration). RESULTS: T-cell cytokines (IL-2, IFN-γ, IL-13, IL-17), LPS-stimulated cytokines (IL-1ß, IL-6, TNF-α, and IL-10), and T-cell concentrations at endline did not differ between intervention groups, nor was there an interaction with baseline zinc status. However, mean ± SE endline lymphocyte concentrations were significantly lower in the PZ than in the control group (5018 ± 158 compared with 5640 ± 160 cells/µL, P = 0.032). Interactions with baseline zinc status were seen for eosinophils (Pixn = 0.0036), basophils (Pixn = 0.023), and monocytes (P = 0.086) but a significant subgroup difference was seen only for eosinophils, where concentrations were significantly lower in the PZ than in the control group among children with baseline plasma zinc concentrations below the overall median (524 ± 44 compared with 600 ± 41 cells/µL, P = 0.012). CONCLUSIONS: Zinc supplementation of rural Laotian children had no effect on cytokines or T-cell concentrations, although zinc supplementation affected lymphocyte and eosinophil concentrations. These cell subsets may be useful as indicators of response to zinc supplementation.This trial was registered at clinicaltrials.gov as NCT02428647.

Impact of Daily Preventive Zinc or Therapeutic Zinc Supplementation for Diarrhea on Plasma Biomarkers of Environmental Enteric Dysfunction among Rural Laotian Children: A Randomized Controlled Trial.

Environmental enteric dysfunction (EED) may be ameliorated by zinc supplementation. The objective of this study was to investigate the impact of different forms of zinc supplementation on biomarkers of EED (i.e., plasma citrulline, kynurenine, and tryptophan concentrations and the kynurenine:tryptophan [KT] ratio) among young Laotian children. In a double-blind randomized controlled trial, 3,407 children aged 6-23 months were randomized into one of four groups: daily preventive zinc dispersible tablets (PZ; 7 mg zinc), daily multiple micronutrient powders (MNP; 10 mg zinc, 6 mg iron, and 13 other micronutrients), therapeutic zinc supplements for diarrhea treatment (TZ; 20 mg/day for 10 days), or daily placebo powder, and followed up for ∼36 weeks. Plasma samples at baseline and endline for 359 children were analyzed for citrulline, kynurenine, and tryptophan concentrations. At baseline, the prevalence of stunting and zinc deficiency was 37% and 76.5%, respectively. The mean plasma citrulline, kynurenine, and tryptophan concentrations were 24.6 ± 5.4 µmol/L, 3.27 ± 0.83 µmol/L, and 72.3 ± 12.9 µmol/L, respectively; the mean KT ratio (×1,000) was 45.9 ± 12.0. At endline, neither plasma citrulline, kynurenine, or tryptophan concentrations, nor the KT ratio differed among intervention groups (P > 0.05). In this population, PZ, MNP, and TZ had no overall effect on plasma concentrations of citrulline, kynurenine, and tryptophan, or the KT ratio. The need remains to better understand the etiology of EED, and the development of biomarkers to diagnose EED and evaluate the impact of interventions.

High-Dose Neonatal Vitamin A Supplementation Transiently Decreases Thymic Function in Early Infancy.

BACKGROUND: Vitamin A deficiency (VAD) impairs T-cell-mediated immunity. In regions where VAD is prevalent, vitamin A supplementation (VAS) reduces child mortality, perhaps by improving immune function. OBJECTIVE: Our objective was to determine if neonatal VAS would improve thymic function in Bangladeshi infants, and to determine if such effects differed by sex or nutritional status (i.e., birth weight above/below the median). METHODS: Three hundred and six infants were randomly assigned to 50,000 IU vitamin A (VA) or placebo (PL) within 48 h of birth. Primary outcomes were measured at multiple ages and included 1) thymic index (TI) at 1, 6, 10, and 15 wk; 2) T-cell receptor excision circles (TREC), an index of thymic output of naïve T cells; and 3) total/naïve T cells in peripheral blood at 6 wk, 15 wk, and 2 y. A mixed linear model for repeated measures was used to assess group differences at each age and identify interactions with sex and birth weight. RESULTS: VAS did not significantly (P = 0.21) affect TI overall (i.e., at all ages) but decreased TI by 7.8% (P = 0.029) at 6 wk: adjusted TI means for the PL and VA groups at 1, 6, 10, and 15 wk were 4.09 compared with 3.80 cm2, 7.78 compared with 7.18 cm2, 8.11 compared with 7.84 cm2, and 7.91 compared with 7.97 cm2, respectively. VAS did not significantly (P = 0.25) affect TREC overall but decreased TREC by 19% (P = 0.029) at 15 wk: adjusted TREC means for the PL and VA groups at 6 wk, 15 wk, and 2 y were 13.6 compared with 16.1 copies/pg DNA, 19.4 compared with 15.7 copies/pg DNA, and 11.8 compared with 10.0 copies/pg DNA, respectively. VAS did not significantly affect overall total (P = 0.10) or naïve (P = 0.092) T cells: adjusted naïve T-cell means for the PL and VA groups at 6 wk, 15 wk, and 2 y were 3259 compared with 3109 cells/µL, 3771 compared with 3487 cells/µL, and 1976 compared with 1898 cells/µL, respectively. CONCLUSION: In contrast to our hypothesis, VAS decreased thymic function early in infancy but health effects are presumably negligible owing to the transience and small magnitude of this effect. This trial was registered at clinicaltrials.gov as NCT01583972 and NCT02027610.

Neonatal Vitamin A Supplementation and Vitamin A Status Are Associated with Gut Microbiome Composition in Bangladeshi Infants in Early Infancy and at 2 Years of Age.

BACKGROUND: Infancy is a crucial period for establishing the intestinal microbiome. This process may be influenced by vitamin A (VA) status because VA affects intestinal immunity and epithelial integrity, factors that can, in turn, modulate microbiome development. OBJECTIVES: The aim of this study was to determine if neonatal VA supplementation (VAS) affected the abundance of Bifidobacterium, a beneficial commensal, or of Proteobacteria, a phylum containing enteric pathogens, in early (6-15 wk) or late (2 y) infancy. Secondary objectives were to determine if VAS affected the abundance of other bacterial taxa, and to determine if VA status assessed by measuring plasma retinol was associated with bacterial abundance. METHODS: Three hundred and six Bangladeshi infants were randomized by sex and birthweight status (above/below median) to receive 1 VA dose (50,000 IU) or placebo within 48 h of birth. Relative abundance at the genus level and above was assessed by 16S rRNA gene sequencing. A terminal restriction fragment-length polymorphism assay was used to identify Bifidobacterium species and subspecies at 6 wk. RESULTS: Linear regression showed that Bifidobacterium abundance in early infancy was lower in boys (median, 1st/3rd quartiles; 0.67, 0.52/0.78) than girls (0.73, 0.60/0.80; P = 0.003) but that boys receiving VAS (0.69, 0.55/0.78) had higher abundance than boys receiving placebo (0.65, 0.44/0.77; P = 0.039). However this difference was not seen in girls (VAS 0.71, 0.54/0.80; placebo 0.75, 0.63/0.81; P = 0.25). VAS did not affect Proteobacteria abundance. Sex-specific associations were also seen for VA status, including positive associations of plasma retinol with Actinobacteria (the phylum containing Bifidobacterium) and Akkermansia, another commensal with possible health benefits, for girls in late infancy. CONCLUSIONS: Better VA status in infancy may influence health both in infancy and later in life by promoting the establishment of a healthy microbiota. This postulated effect of VA may differ between boys and girls. This trial was registered at clinicaltrials.gov as NCT02027610.

Infant cortisol stress-response is associated with thymic function and vaccine response.

Stress can impair T cell-mediated immunity. To determine if infants with high stress responses had deficits in T-cell mediated immunity, we examined the association of pain-induced cortisol responsiveness with thymic function and vaccine responses in infants. This study was performed among 306 (male = 153 and female = 153) participants of a randomized, controlled trial examining the effect of neonatal vitamin A supplementation on immune function in Bangladesh (NCT01583972). Salivary cortisol was measured before and 20 min after a needle stick (vaccination) at 6 weeks of age. The thymic index (TI) was determined by ultrasonography at 1, 6, 10 and 15 weeks. T-cell receptor excision circle and blood T-cell concentrations were measured at 6 and 15 weeks. Responses to Bacillus Calmette-Guérin (BCG), tetanus toxoid, hepatitis B virus and oral poliovirus vaccination were assayed at 6 and 15 weeks. Cortisol responsiveness was negatively associated with TI at all ages (p < .01) in boys only, was negatively associated with naïve helper T-cell concentrations in both sexes at both 6 (p = .0035) and 15 weeks (p = .0083), and was negatively associated with the delayed-type hypersensitivity (DTH) skin test response to BCG vaccination at 15 weeks (p = .034) in both sexes. Infants with a higher cortisol response to pain have differences in the T-cell compartment and a lower DTH response to vaccination. Sex differences in the immune system were seen as early as 6 weeks of age in these healthy infants.

Comparison of two forms of daily preventive zinc supplementation versus therapeutic zinc supplementation for diarrhea on young children's physical growth and risk of infection: study design and rationale for a randomized controlled trial.

BACKGROUND: Zinc is an essential nutrient that is required for children's normal growth and resistance to infections, including diarrhea and pneumonia, two major causes of child mortality. Daily or weekly preventive zinc supplementation has been shown to improve growth and reduce the risk of infection, while therapeutic zinc supplementation for 10-14 days is recommended for the treatment of diarrhea. The overall objective of the present study is to compare several regimens for delivering zinc to young children, both for the prevention of zinc deficiency and the treatment of diarrhea. METHODS: The present study is a community-based, randomized controlled trial in the Lao People's Democratic Republic (PDR). Three thousand, four hundred children 6-23 months of age will be randomized to one of four intervention groups (daily preventive zinc dispersible tablet, daily preventive multiple micronutrient powder, therapeutic zinc dispersible tablet for diarrhea, or placebo control); interventions will be delivered for 9 months and outcomes measured at pre-determined intervals. Primary outcomes include physical growth (length and weight), diarrhea incidence, hemoglobin and micronutrient status, and innate and adaptive immune function. Secondary outcomes include mid-upper-arm circumference, neuro-behavioral development, hair cortisol concentrations, markers of intestinal inflammation and parasite burden. Incidence of adverse events and the modifying effects of inherited hemoglobin disorders and iron status on the response to the intervention will also be examined. We will estimate unadjusted effects and effects adjusted for selected baseline covariates using ANCOVA. DISCUSSION: Many countries are now rolling out large-scale programs to include therapeutic zinc supplementation in the treatment of childhood diarrhea, but few have established programs demonstrated to be effective in the prevention of zinc deficiency. This study will address how best to deliver supplemental zinc to prevent zinc deficiency and reduce the severity of diarrhea-related health complications. TRIAL REGISTRATION: Trial registration identifier (NCT02428647) ; Date of registration: April 29, 2015.

Vitamin D3 Supplementation Increases Spine Bone Mineral Density in Adolescents and Young Adults With Human Immunodeficiency Virus Infection Being Treated With Tenofovir Disoproxil Fumarate: A Randomized, Placebo-Controlled Trial.

Background: Tenofovir disoproxil fumarate (TDF) decreases bone mineral density (BMD). We hypothesized that vitamin D3 (VITD3) would increase BMD in youth receiving TDF. Methods: This was a randomized, double-blind, placebo-controlled trial of directly observed VITD3 vs placebo every 4 weeks for 48 weeks in youth aged 16-24 years with HIV, RNA load <200 copies/mL, taking TDF-containing combination antiretroviral therapy (TDF-cART) for ≥180 days. Participants (N = 214) received a daily multivitamin containing VITD3 400 IU and calcium 162 mg, plus monthly randomized VITD3 50000 IU (n = 109) or placebo (n = 105). Outcome was change from baseline to week 48 in lumbar spine BMD (LSBMD). Data presented are median (Q1, Q3). Results: Participants were aged 22.0 (21.0, 23.0) years, 84% were male, and 74% were black/African American. At baseline, 62% had 25-hydroxy vitamin D (25-OHD) <20 ng/mL. Multivitamin adherence was 49% (29%, 69%), and VITD3/placebo adherence 100% (100%, 100%). Vitamin D intake was 2020 (1914, 2168) and 284 (179, 394) IU/day, and serum 25-OHD concentration was 36.9 (30.5, 42.4) and 20.6 (14.4, 25.8) ng/mL at 48 weeks in VITD3 and placebo groups, respectively (P < .001). From baseline to week 48, LSBMD increased by 1.15% (-0.75% to 2.74%) in the VITD3 group (n = 99; P < .001) and 0.09% (-1.49% to 2.61%) in the placebo group (n = 89; P = .25), without between-group difference (P = .12). VITD3 group changes occurred with baseline 25-OHD <20 ng/mL (1.17% [-.82% to 2.90%]; P = .004) and ≥20 ng/mL (0.93% [-.26% to 2.15%]; P = .033). Conclusions: For youth taking TDF-cART, LSBMD increased through 48 weeks with VITD3 plus multivitamin, but not with placebo plus multivitamin, independent of baseline vitamin D status. Clinical Trials Registration: NCT01751646.

Associations of Low Vitamin D and Elevated Parathyroid Hormone Concentrations With Bone Mineral Density in Perinatally HIV-Infected Children.

BACKGROUND: Perinatally HIV-infected (PHIV) children have, on average, lower bone mineral density (BMD) than perinatally HIV-exposed uninfected (PHEU) and healthy children. Low 25-hydroxy vitamin D [25(OH)D] and elevated parathyroid hormone (PTH) concentrations may lead to suboptimal bone accrual. METHODS: PHIV and PHEU children in the Pediatric HIV/AIDS Cohort Study had total body (TB) and lumbar spine (LS) BMD and bone mineral content (BMC) measured by dual-energy x-ray absorptiometry; BMD z-scores (BMDz) were calculated for age and sex. Low 25(OH)D was defined as ≤20 ng/mL and high PTH as >65 pg/mL. We fit linear regression models to estimate the average adjusted differences in BMD/BMC by 25(OH)D and PTH status and log binomial models to determine adjusted prevalence ratios of low 25(OH)D and high PTH in PHIV relative to PHEU children. RESULTS: PHIV children (n = 412) were older (13.0 vs. 10.8 years) and more often black (76% vs. 64%) than PHEU (n = 207). Among PHIV, children with low 25(OH)D had lower TB-BMDz [SD, -0.38; 95% confidence interval (CI), -0.60 to -0.16] and TB-BMC (SD, -59.1 g; 95% CI, -108.3 to -9.8); high PTH accompanied by low 25(OH)D was associated with lower TB-BMDz. Among PHEU, children with low 25(OH)D had lower TB-BMDz (SD, -0.34; 95% CI, -0.64 to -0.03). Prevalence of low 25(OH)D was similar by HIV status (adjusted prevalence ratio, 1.00; 95% CI, 0.81 to 1.24). High PTH was 3.17 (95% CI, 1.25 to 8.06) times more likely in PHIV children. CONCLUSIONS: PHIV and PHEU children with low 25(OH)D may have lower BMD. Vitamin D supplementation trials during critical periods of bone accrual are needed.

Metabolic Effects of Inflammation on Vitamin A and Carotenoids in Humans and Animal Models.

The association between inflammation and vitamin A (VA) metabolism and status assessment has been documented in multiple studies with animals and humans. The relation between inflammation and carotenoid status is less clear. Nonetheless, it is well known that carotenoids are associated with certain health benefits. Understanding these relations is key to improving health outcomes and mortality risk in infants and young children. Hyporetinolemia, i.e., low serum retinol concentrations, occurs during inflammation, and this can lead to the misdiagnosis of VA deficiency. On the other hand, inflammation causes impaired VA absorption and urinary losses that can precipitate VA deficiency in at-risk groups of children. Many epidemiologic studies have suggested that high dietary carotenoid intake and elevated plasma concentrations are correlated with a decreased risk of several chronic diseases; however, large-scale carotenoid supplementation trials have been unable to confirm the health benefits and in some cases resulted in controversial results. However, it has been documented that dietary carotenoids and retinoids play important roles in innate and acquired immunity and in the body's response to inflammation. Although animal models have been useful in investigating retinoid effects on developmental immunity, it is more challenging to tease out the effects of carotenoids because of differences in the absorption, kinetics, and metabolism between humans and animal models. The current understanding of the relations between inflammation and retinoid and carotenoid metabolism and status are the topics of this review.

Daily Cholecalciferol Supplementation during Pregnancy Alters Markers of Regulatory Immunity, Inflammation, and Clinical Outcomes in a Randomized Controlled Trial.

BACKGROUND: Vitamin D deficiency is widespread in pregnancy and has been associated with adverse health conditions in mothers and infants. Vitamin D supplementation in pregnancy may support the maintenance of pregnancy by its effects on innate and adaptive immunity. OBJECTIVE: We assessed the effects of vitamin D supplementation during pregnancy on vitamin D status and markers of immune function associated with adverse pregnancy outcomes. METHODS: We conducted a randomized, controlled, double-blind intervention of 2 doses of cholecalciferol (400 and 2000 IU/d) from <20 wk to delivery in 57 pregnant women. Vitamin D status, regulatory and inflammatory T cells, markers of innate immunity and systemic inflammation, and clinical outcomes including maternal blood pressure and birth weight were assessed at 26 and 36 wk of pregnancy. RESULTS: Supplementation with 2000 IU/d vitamin D had a greater effect on the change in vitamin D status over pregnancy (P < 0.0001) and the final value at 36 wk (P < 0.0001) than 400 IU/d, increasing serum 25-hydroxyvitamin D from 81.1 nmol/L at baseline to 116 nmol/L at 36 wk and from 69.6 nmol/L at baseline to 85.6 nmol/L at 36 wk, respectively. The 2000-IU/d group had 36% more interleukin-10+ regulatory CD4+ T cells at 36 wk than did the 400-IU/d group (P < 0.007). The daily intake of 2000 compared with 400 IU/d tended to dampen the pregnancy-related increase in diastolic blood pressure by 1.3-fold (P = 0.06) and increase birth weight by 8.6% (P = 0.06), but these differences were not statistically significant. CONCLUSIONS: Supplementation with 2000 IU/d is more effective at increasing vitamin D status in pregnant women than 400 IU/d and is associated with increased regulatory T cell immunity that may prevent adverse outcomes caused by excess inflammation. This trial was registered at clinicaltrials.gov as NCT01417351.

Biomarkers of Nutrition for Development (BOND)-Vitamin A Review.

The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-informed advice to anyone with an interest in the role of nutrition in health. The BOND program provides information with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect, which will be especially useful for readers who want to assess nutrient status. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutritional status at the individual and population levels. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, folate, zinc, iron, vitamin A, and vitamin B-12. This review of vitamin A is the current article in this series. Although the vitamin was discovered >100 y ago, vitamin A status assessment is not trivial. Serum retinol concentrations are under homeostatic control due in part to vitamin A's use in the body for growth and cellular differentiation and because of its toxic properties at high concentrations. Furthermore, serum retinol concentrations are depressed during infection and inflammation because retinol-binding protein (RBP) is a negative acute-phase reactant, which makes status assessment challenging. Thus, this review describes the clinical and functional indicators related to eye health and biochemical biomarkers of vitamin A status (i.e., serum retinol, RBP, breast-milk retinol, dose-response tests, isotope dilution methodology, and serum retinyl esters). These biomarkers are then related to liver vitamin A concentrations, which are usually considered the gold standard for vitamin A status. With regard to biomarkers, future research questions and gaps in our current understanding as well as limitations of the methods are described.

The effect of newborn vitamin A supplementation on infant immune functions: trial design, interventions, and baseline data.

In recent years, neonatal vitamin A supplementation is considered as an essential infant-survival intervention but the evidence is not conclusive. This randomized controlled clinical trial was conducted to evaluate the effect of vitamin A on immune competence in early infancy. Results would provide a mechanistic basis for understanding the effect of this intervention on infant survival. Within 2 days of birth, infants born at one maternity clinic located in a poor slum area of Dhaka city were supplemented with either 50,000 IU vitamin A or placebo. Live attenuated oral polio vaccine (OPV) and BCG vaccine were provided after supplementation. Infants also receive diphtheria, pertussis, tetanus (TT), hepatitis B (HBV) and Haemophilus influenzae B vaccines (pentavalent combination) along with OPV at 6, 10 and 14 weeks of age. Infant thymus size, anthropometry, feeding practice and morbidity data were collected at regular interval. Infant blood samples were collected to determine T-cell-receptor excision circle (TREC), total, naïve and memory T cells and mucosal targeting lymphocytes including Treg cells. TT-, HBV-, BCG- and OPV-specific T cell blastogenic, cytokine and plasma cell antibody responses were also measured. In 16 mo enrollment period, 306 newborns, equal number of boys and girls, were enrolled. ~95% completed the 4-month follow-up period. Baseline characteristics are presented here. Anthropometry and immune assays with fresh blood samples were completed immediately while stored samples were analyzed in single batches at the end of the trial. Connecting different aspects of immunological data in early infancy will help elucidate immune competence for protecting infection. Trial registration ClinicalTrials.gov: NCT01583972.

Vitamin D3 supplementation increases fibroblast growth factor-23 in HIV-infected youths treated with tenofovir disoproxil fumarate.

BACKGROUND: Tenofovir (TDF) is associated with phosphaturia and elevated 1,25 dihydroxy vitamin D (1,25-OH(2)D). Fibroblast growth factor 23 (FGF23) causes phosphaturia and increases in response to elevated 1,25-OH(2)D. Vitamin D-binding protein (VDBP) binds to 1,25-OH(2)D, decreasing its biological activity, and is elevated in individuals with higher plasma tenofovir concentrations. We compared FGF23 and VDBP before and after vitamin D3 (VITD) supplementation in youths treated with combination antiretroviral therapy (cART) containing or not containing TDF. METHODS: A randomized controlled trial in HIV-positive youths aged 18-25 years enrolled participants based on cART treatment with TDF (TDF; n=118) or without TDF (no-TDF; n=85), and randomized within those groups to VITD (50,000 IU every 4 weeks) or placebo (PL). We measured FGF23 and VDBP and calculated free 1,25-OH(2)D at baseline and week 12, and compared changes by TDF treatment and VITD randomized group. RESULTS: At baseline, serum FGF23 concentration showed a quadratic relationship with 1,25-OH(2)D most pronounced in the TDF group. At week 12, total and free 1,25-OH(2)D increased in the VITD but not PL groups, independent of TDF use. FGF23 increased in the TDF group receiving VITD, but there was no FGF23 change in the no-TDF group receiving VITD or the PL groups. The adjusted mean change in FGF23 from baseline to week 12 was 7.7 pg/ml in the TDF/VITD group, compared with -1.7 (no-TDF/VITD, P=0.010), -1.3 (TDF/PL, P=0.006) and 1.1 (no-TDF/PL, P=0.035). CONCLUSIONS: These results suggest that TDF-containing cART may alter the FGF23 response to vitamin D supplementation in HIV-infected youths. Clinical trials number: NCT00490412.

Habitual diets rich in dark-green vegetables are associated with an increased response to ω-3 fatty acid supplementation in Americans of African ancestry.

Although substantial variation exists in individual responses to omega-3 (ω-3) (n-3) fatty acid supplementation, the causes for differences in response are largely unknown. Here we investigated the associations between the efficacy of ω-3 fatty acid supplementation and a broad range of nutritional and clinical factors collected during a double-blind, placebo-controlled trial in participants of African ancestry, randomly assigned to receive either 2 g eicosapentaenoic acid (EPA) + 1 g docosahexaenoic acid (n = 41) or corn/soybean oil placebo (n = 42) supplements for 6 wk. Food-frequency questionnaires were administered, and changes in erythrocyte lipids, lipoproteins, and monocyte 5-lipoxygenase-dependent metabolism were measured before and after supplementation. Mixed-mode linear regression modeling identified high (n = 28) and low (n = 13) ω-3 fatty acid response groups on the basis of changes in erythrocyte EPA abundance (P < 0.001). Compliance was equivalent (∼88%), whereas decreases in plasma triglycerides and VLDL particle sizes and reductions in stimulated monocyte leukotriene B4 production were larger in the high-response group. Although total diet quality scores were similar, the low-response group showed lower estimated 2005 Healthy Eating Index subscores for dark-green and orange vegetables and legumes (P = 0.01) and a lower intake of vegetables (P = 0.02), particularly dark-green vegetables (P = 0.002). Because the findings reported here are associative in nature, prospective studies are needed to determine if dietary dark-green vegetables or nutrients contained in these foods can enhance the efficacy of ω-3 fatty acid supplements. This trial was registered at clinicaltrials.gov as NCT00536185.

Dietary long-chain omega-3 fatty acids do not diminish eosinophilic pulmonary inflammation in mice.

Although the effects of fish oil supplements on airway inflammation in asthma have been studied with varying results, the independent effects of the fish oil components, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), administered separately, are untested. Here, we investigated airway inflammation and hyperresponsiveness using a mouse ovalbumin exposure model of asthma assessing the effects of consuming EPA (1.5% wt/wt), DHA (1.5% wt/wt), EPA plus DHA (0.75% each), or a control diet with no added omega-3 polyunsaturated fatty acids. Consuming these diets for 6 weeks resulted in erythrocyte membrane EPA contents (molar %) of 9.0 (± 0.6), 3.2 (± 0.2), 6.8 (± 0.5), and 0.01 (± 0.0)%; DHA contents were 6.8 (± 0.1), 15.6 (± 0.5), 12.3 (± 0.3), and 3.8 (± 0.2)%, respectively. The DHA group had the highest bronchoalveolar lavage (BAL) fluid eosinophil and IL-6 levels (P < 0.05). Similar trends were seen for macrophages, IL-4, and IL-13, whereas TNF-α was lower in omega-3 polyunsaturated fatty acid groups than the control (P < 0.05). The DHA group also had the highest airway resistance, which differed significantly from the EPA plus DHA group (P < 0.05), which had the lowest. Oxylipins were measured in plasma and BAL fluid, with DHA and EPA suppressing arachidonic acid-derived oxylipin production. DHA-derived oxylipins from the cytochrome P450 and 15-lipoxygenase pathways correlated significantly with BAL eosinophil levels. The proinflammatory effects of DHA suggest that the adverse effects of individual fatty acid formulations should be thoroughly considered before any use as therapeutic agents in asthma.

Serum 25-hydroxyvitamin D response to vitamin D3 supplementation 50,000 IU monthly in youth with HIV-1 infection.

CONTEXT: Vitamin D deficiency and insufficiency occur frequently in youth with HIV infection, particularly among those receiving the antiretroviral drug efavirenz. Optimal vitamin D dosing for treatment is unclear. OBJECTIVE: Our objective was to evaluate safety and measure change in 25-hydroxyvitamin D (25-OHD) concentration from baseline to study wk 4 and 12 during treatment with vitamin D(3), 50,000 IU monthly. DESIGN, SETTING, AND PARTICIPANTS: We conducted a randomized double-blind, placebo-controlled multicenter trial of HIV-infected youth ages 18-24 yr, with viral load below 5000 copies/ml, on stable antiretroviral therapy. INTERVENTION: INTERVENTION included vitamin D(3), 50,000 IU (n = 102), or matching placebo (n = 101) administered in three directly observed oral doses at monthly intervals. RESULTS: At baseline, mean (sd) age was 20.9 (2.0) yr; 37% were female and 52% African-American, and 54% were vitamin D deficient/insufficient (25-OHD < 20 ng/ml), with no randomized group differences. Of evaluable participants vitamin D deficient/insufficient at baseline who were administered vitamin D, 43 of 46 (93%) had sufficient 25-OHD by wk 12. Vitamin D supplementation increased 25-OHD serum concentration from a baseline of 21.9 (13.3) to 35.9 (19.1) ng/ml at wk 12 (P < 0.001) with no change for placebo. Although use of the antiretroviral efavirenz was associated with lower baseline 25-OHD concentration, efavirenz did not diminish the response to vitamin D supplementation. There was no treatment-related toxicity. CONCLUSIONS: Supplementation with vitamin D(3) 50,000 IU monthly for three doses was safe. Increases in 25-OHD occurred in treated participants regardless of antiretroviral regimen.

Arachidonate 5-lipoxygenase gene variants affect response to fish oil supplementation by healthy African Americans.

Arachidonate 5-lipoxygenase (ALOX5) gene variants that are common in people of African ancestry are associated with a differential cardiovascular disease (CVD) risk that may be ameliorated by intake of (n-3) PUFA, such as EPA or DHA. We conducted a double-masked, placebo (PL)-controlled trial of fish oil (FO) supplements to determine if changes in erythrocyte (n-3) PUFA composition, heart rate, blood pressure, and plasma lipid and lipoprotein concentrations are modified by genotype. Participants received 5 g/d FO (2 g EPA, 1 g DHA) or 5 g/d corn/soy oil (PL). A total of 116 healthy adults of African ancestry with selected genotypes (genotypes = "dd," "d5," and "55" with "d" representing the deletion of 1 or 2 Sp1 binding sites in the ALOX5 promoter and "5" indicating the common allele with 5 sites) were enrolled and 98 completed the study. FO caused significant increases (relative to PL) in erythrocyte EPA, DHA, and total (n-3) PUFA and a decrease in the (n-6) PUFA:(n-3) PUFA ratio in the low-CVD risk "d5" and "55" genotypes but not in the high-risk "dd" genotype. Similarly, HDL particle concentration decreased with FO relative to PL in the "d5" and "55" but not "dd" genotypes. The plasma TG concentration decreased significantly with FO relative to PL in the "d5" but not "dd" and "55" genotypes. No changes were seen in LDL particle or cholesterol concentrations, heart rate, or blood pressure. These findings indicate that the efficacy of FO supplements vary by ALOX5 genotype.