Vitamin D Status Increases During Pregnancy and in Response to Vitamin D Supplementation in Rural Gambian Women

Exercise without Weight Loss Prevents Seasonal Decline in Vitamin D Metabolites: The VitaDEx Randomized Controlled Trial

Many adults become vitamin D deficient or insufficient during winter at northerly latitudes when cutaneous vitamin D synthesis does not occur. Vitamin D accumulates in adipose tissue and people with overweight or obesity are more likely to have low systemic vitamin D. This randomized controlled trial demonstrates that regular exercise completely maintains serum concentrations of the active vitamin D metabolite 1,25(OH)2D3 over winter and may ameliorate the decline in 25(OH)D status in overweight men and women, even without weight loss. The binding of 1,25(OH)2D3 to the vitamin D receptor mediates the crucial role for vitamin D in the healthy function of multiple organ systems and vitamin D supplementation does not impact circulating 1,25(OH)2D3. Thus, the VitaDEx study provides causal evidence that exercise plays an important role in vitamin D metabolism that is distinct from the effects of oral supplementation.

The validation of an LC-MS/MS method for the quantification of vitamin D metabolites in human milk and their biological variability in Gambian women

Vitamin D is required for healthy growth and development, but data on human milk vitamin D content is limited. We describe a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the analysis of vitamin D metabolites in human milk, and its application in samples collected on two consecutive days from women in rural Gambia. Vitamin D compounds were extracted from 1 mL of milk by liquid-liquid extraction and derivatised with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) prior to analysis by LC-MS/MS. The limit of quantification was 0.05 nmol/L for vitamin D2, 0.025 nmol/L for vitamin D3 and 0.1 nmol/L for 25(OH)D2 and 25(OH)D3. Within- and between-day imprecision was <12 % for all analytes except vitamin D2 (14 %). From all data combined, geometric mean (-/+ 1 SD) vitamin D3 concentration was 0.94 (0.43, 1.80) nmol/L and for 25(OH)D3 0.32 (0.23, 0.42) nmol/L. The within-person (intra-individual) coefficient of variation (%CV) was 32 % and 12 % for vitamin D3 and 25(OH)D3, respectively. Between-person (inter-individual) %CVs were 89 % and 34 % for vitamin D3 and 25(OH)D3, respectively. There was no significant association between vitamin D metabolite concentrations and milk fat (creamatocrit). Mean vitamin D content of human milk as ARA averaged 42 IU/L with 25(OH)D3 responsible for around two-thirds of the biological activity. In conclusion, this work describes a reliable LC-MS/MS method for quantification of vitamin D and 25(OH)D in low volumes of human milk providing a platform for future work. This study contributes to current understanding of variability of milk vitamin D content.

Vitamin D concentration in the blood of women with twin pregnancies and in the umbilical cord blood of newborns in relation to environmental factors

Background

There is a huge gap in the knowledge of the body's nutrient resources in women with multiple gestations. Due to the increased demand hypothesis and taking into account common vitamin D deficits in women with singleton pregnancies, this issue should also be investigated in twin pregnancies. This study evaluated blood vitamin D concentration in women with twin pregnancies and in the umbilical cord blood of their newborns as well as analyzed environmental factors that may affect the level of this nutrient.

Methods

The study included 56 women with twin pregnancies. Venous blood samples were collected from the women before delivery and umbilical cord blood at delivery to determine the total 25(OH)D concentration. The women were interviewed by a dietitian to collect data on their diet and lifestyle.

Results

The average maternal 25(OH)D concentrations were 38.4 ± 11.0 ng/mL vs. 23.7 ± 6.1 ng/mL determined in the umbilical cord blood of the newborns. The concentration of 25(OH)D in the umbilical cord blood was strongly correlated with the concentration in the mother (p < 0.001). Vitamin D deficiency was found in 7% of women and 21% of newborns. Factors increasing the risk of too low 25(OH)D concentration in the mothers were age below 27 years (p = 0.002) and short duration of pregnancy (p = 0.011). In newborns, the risk factors included low maternal concentrations (p < 0.001) and delivery before 36 weeks of gestation (p = 0.008). The mean cord blood 25(OH)D levels were almost identical in both twins and amounted to 24.0 ± 6.1 ng/mL in the first-born and 23.4 ± 6.1 ng/mL in the second-born infant. Vitamin D supplementation was declared by 98% of the women, with 85% taking ≤2,000 IU vitamin D daily.

Conclusion

Only a small percentage of women with twin pregnancies presented with vitamin D deficiency, which was probably related to the widespread supplementation of this nutrient. It can therefore be assumed that a dose of 2,000 IU vitamin D currently recommended for pregnant women may also be appropriate for twin gestations, although further research is required to validate this finding.

Vitamin D Levels and Depressive Symptoms during Pregnancy: A Prospective Pregnancy Cohort Study

Objective

Depressive symptoms during pregnancy increase the risk for adverse outcomes in women and children. Lower vitamin D levels are suggested to be associated with higher depressive symptoms in nonpregnant populations. We studied if the level of or change in serum of 25-hydroxyvitamin D (25(OH)D) concentration was associated with the levels of depressive symptoms during pregnancy.

Methods

The participants of this prospective longitudinal study came from the Prediction and Prevention of Preeclampsia and Intrauterine Growth Restriction (PREDO) study. The analytic sample comprised 307 women (mean age = 32.5 (range 20.3-44.3)) who reported depressive symptoms concurrently with serum 25(OH)D measurements at a median of 13.0, 19.3, and 27.0 gestational weeks. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale. Linear and mixed-model regression analyses were used to study the associations.

Results

The 25(OH)D levels were not associated with depressive symptoms cross-sectionally (p values > 0.58) or across the three assessment points during pregnancy (B = -0.05; 95% CI, -0.12, 0.01; and p = 0.12). Yet, a higher increase in 25(OH)D during pregnancy was associated with lower levels of depressive symptoms (B = -1.41; 95% CI, -2.75, -0.07; and p = 0.04) but not after adjusting for covariates (p = 0.08).

Conclusions

The 25(OH)D levels and depressive symptoms were not associated among pregnant women throughout the pregnancy. However, there is a need for randomized controlled trials to fully exclude the possibility of vitamin D supplementation in the prevention of depression during pregnancy.

Vitamin D nutritional status in early pregnancy and its relationship with periconceptional multiple micronutrients supplementation

BACKGROUND AND OBJECTIVES

To assess the vitamin D nutritional status (VDN) of pregnant women in early pregnancy and investigate the effects of periconceptional supplementation with multiple micronutrients (MMs) on this status.

METHODS AND STUDY DESIGN

Data were taken from the Pregnancy Health Care System and Hospital Information System in 2018 in Beijing. Vitamin D nutritional status in early pregnancy was evaluated among 4,978 pregnant women, and 4,540 women who took folic acid only (FA) or multiple mi-cronutrients supplements (MM) during the periconceptional period, were include to estimate the associations between periconceptional supplementation with MM and prevalence of vitamin D deficiency or insufficiency with logistic regression model.

RESULTS

The mean early-pregnancy vitamin D concentration was 18.6 (±7.5) ng/mL, and the rates of deficiency and insufficiency were 31.6% and 60.5%, respectively. Compared to the FA group, the adjusted odds ratio (aOR, 95%confidence interval, CI) for insufficiency or deficiency of the MM group were 0.25(0.18-0.34), and the aOR (95%CI) for deficiency of the MM group were 0.17 (0.12-0.23). Women who took MMs for a longer period of time, at higher frequencies, and with higher compliance scores had lower rates of deficiency and insufficiency. In winter, spring, and autumn, taking MMs could reduce deficiency by about 70%; in summer, there was little effect.

CONCLUSIONS

Among women in Beijing, serum concentrations of vitamin D in early pregnancy are relatively low, and the rates of deficiency and insufficiency are high. Taking MMs during the periconceptional period could improve this situation.

C3-epi-25(OH)D3 percentage, not level, may be a potential biomarker to reflect its pathological increase in multiple diseases: a cross-sectional case-control study

National surveys in developed countries have examined the presence of C3-epimer of 25-hydroxyvitamin D3 [C3-epi-25(OH)D3]. However, controversy remains regarding its association with disease occurrence due to its high correlation with 25-hydroxyvitamin D3 [25(OH)D3]. This study aims to investigate whether %C3-epi-25(OH)D3 can serve as an indicator for this relationship with various diseases. A total of 3086 healthy participants and 4120 patients were included in this study. We investigated the association between C3-epi-25(OH)D3 and %C3-epi-25(OH)D3 levels with gender, age, and season; compared the performance of C3-epi-25(OH)D3 and %C3-epi-25(OH)D3 across different disease conditions; and explored the correlation between %C3-epi-25(OH)D3 and various diseases. Results indicated that C3-epi-25(OH)D3 varied significantly by gender, age, and season (z/χ2 = 3.765, 10.163, and 150.975, all P < 0.01), while only season for %C3-epi-25(OH)D3 (χ2 = 233.098, P < 0.001). In contrast to the significant decrease in C3-epi-25(OH)D3, %C3-epi-25(OH)D3 showed a significant increase in 8 out of 11 disease categories (z = 3.464 ~ 11.543, all Padj < 0.05). Similar opposite changes were also observed in most of the investigated 32 specific diseases. Moreover, an elevation in %C3-epi-25(OH)D3 was found to be significantly associated with 29 specific diseases both in univariate analysis (OR = 1.16 ~ 2.10, all P < 0.05) and after adjusting for gender, age, and season (OR = 1.15 ~ 1.50, all P < 0.05). However, after further adjustment for 25(OH)D3 levels, the association remained significant only for 15 specific diseases (OR = 1.11 ~ 1.50, all P < 0.05). Seasonal stratification analysis further supports the consistent association of %C3-epi-25(OH)D3 with disease across all or nearly all four seasons. In conclusion, %C3-epi-25(OH)D3 may better reflect the production of C3-epi-25(OH)D3 in disease conditions, thereby offering a more applicable approach to investigate its association with diseases. However, the interpretation of this relationship may be confounded by 25(OH)D3 as a potential covariate.

Quantification and reporting of vitamin D concentrations measured in human milk by LC-MS/MS

Vitamin D is essential for optimal bone health, and vitamin D deficiency has been associated with an increased risk of adverse pregnancy, growth and developmental outcomes. In early life, and in the absence of endogenous vitamin D production from UVB light, infants are reliant on vitamin D stores established in utero and the vitamin D supply from human milk (HM). However, comprehensive data on vitamin D in HM is lacking. Thus, in this review we explore the application of liquid-chromatography tandem mass spectrometry (LC-MS/MS) to the assessment of vitamin D in HM. We discuss the challenges of extracting and measuring multiple vitamin D metabolites from HM including the frequent requirement for a large sample volume, and inappropriate poor sensitivity. Shortcomings in the reporting of experimental procedures and data analysis further hinder advances in the field. Data collated from all studies that have applied LC-MS/MS reveal that, in general, cholecalciferol concentration is greater and more variable than 25-hydroxyvitamin D concentration, and that the vitamin D content of HM is low and less than the currently recommended dietary requirement of infants, although maternal supplementation can increase the vitamin D content of HM. Improvements in analytical methods and their validation and larger, more representative studies are required to better characterize HM milk vitamin D metabolite concentrations and their relationship with maternal status. These data are essential to understand relationships with infant health and to inform public health policies around vitamin D fortification and supplementation.

Evaluation of Vitamin D Status and the Analysis of Risk Factors of Vitamin D Deficiency in Twin Pregnancies

OBJECTIVE

Optimization of maternal vitamin D (VD) status has beneficial effects on pregnancies, but little is known about it of twin pregnancies (TP). Our aim was to promote the current understanding of VD status and its associated factors in TP.

METHODS

We performed liquid chromatography-tandem mass spectrometry to quantify 25-hydroxyvitamin D [25(OH)D] and used the enzyme-linked immunosorbent assay method to detect vitamin D binding protein (VDBP) in 218 singleton pregnancies (SP) and 236 TP.

RESULTS

Levels of 25(OH)D and VDBP were higher in TP than SP. The 25(OH)D, free 25(OH)D, C-3 epimer of 25-hydroxyvitamin D [epi-25(OH)D], and VDBP all increased with gestational progress. Age, body 
mass index, and hemoglobin level were associated with VD deficiency (VDD). Analysis of covariance demonstrated that the 25(OH)D and VDBP of TP and SP still showed differences after adjusting for the above associated factors.

CONCLUSION

Differences in VD status were found in SP and TP, suggesting that the assessment of VD status in TP should be treated with caution. High VDD prevalence is observed among pregnant Chinese women, and it is recommended to promote evaluation for VDD.

Multidimensional analysis of the essential elements in pregnant women's whole blood and characterization of maternal status by elemental pattern

BACKGROUND

During pregnancy, the fetus needs to obtain a lot of nutrients from the mother, but the micronutrient deficiencies in pregnancy are not clear at present, and there is no reliable basis for nutrient intake and supplement. The purpose of this study was to understand the levels of essential elements in whole blood of pregnant women during various pregnancy stages at different ages and in different regions, to evaluate the deficiency of essential elements in Chinese pregnant women, and to explore the feasibility of using the elemental pattern to characterize maternal status.

METHODS

Whole blood samples of 11222 healthy pregnant women enrolled in different areas of China from Jan-Dec 2019, were analyzed for concentrations of six essential elements including Mn, Cu, Zn, Ca, Mg, and Fe, using the inductively coupled plasma mass spectrometer. A retrospective comparative study during different pregnancy periods at different ages and in different regions in whole blood essential elements content from non-pregnant normal women and pregnant normal women was developed using multivariate statistical analysis. Principal component analysis evaluation elemental pattern was used to characterize pregnancy status of pregnant women.

RESULTS

In general, the levels of six essential elements in whole blood of pregnant women can satisfy the needs of normal physiological activities. With the development of pregnancy, the contents of Cu and Mn increased, while the contents of Fe and Mg decreased, and the contents of Zn and Ca have no noteworthy change. At the same gestation stage, the Cu content in whole blood of elderly pregnant women was higher. There were some differences in whole blood essential elements content of pregnant women in different regions. Principal component analysis and heat map analysis showed the feasibility of using bioinformatics research strategies to identify different pregnancies.

CONCLUSIONS

There are differences in the content of whole blood essential elements of women at different stages of pregnancy in different regions. It was found that there was no obvious deficiency in whole blood essential elements levels of pregnant women in recent years. The pattern of essential elements has a certain application potential in the evaluation of pregnancy and pregnant women's health status.

C3-Epimer of 25-Hydroxyvitamin D3 as a Superior Marker for Predicting the Severity of Chronic Kidney Disease in Rheumatoid Arthritis Patients

Objective. 25-hydroxyvitamin D3 (25[OH]D3) is involved in oxidative stress regulation by upregulating the expression of antioxidant genes except for mineral homeostasis physiological role. C3-epimer of 25(OH)D3 (C3-epi-25[OH]D3) is a form of vitamin D metabolite with low bioaffinity in vivo, but little is known about the relationship between C3-epi-25(OH)D3 and diseases. This study was aimed at investigating the relationship between C3-epi-25(OH)D3 and the severity of chronic kidney disease (CKD) in patients with rheumatoid arthritis (RA). Method. A total of 318 RA inpatients were enrolled and divided into mild ( $n=247$ ), moderate ( $n=46$ ), and severe ( $n=25$ ) CKD groups according to the CKD prognosis criterion of the Kidney Disease Improving Global Outcomes guidelines. Serum levels of 25(OH)D2, 25(OH)D3, C3-epi-25(OH)D3, and free 25(OH)D (F25[OH]D) were measured, and the value of 25(OH)D was calculated. The relationship and changing trend of the indexes based on CKD severity were analyzed. Results. The serum levels of 25(OH)D, 25(OH)D3, and F25(OH)D showed a decreasing trend ( $z=-2.781–-3.996$ , $P<0.01$ ) in RA patients with CKD progression from mild to severe, while C3-epi-25(OH)D3 showed an increasing trend ( $z=6.741$ , $P<0.001$ ) and 25(OH)D2 showed no significant difference among the groups ( $z=0.976$ , $P=0.329$ ). Only levels of C3-epi-25(OH)D3 presented significant differences between adjacent CKD severity groups in RA patients (mild to moderate: $z=3.963$ , $Padj<0.001$ ; moderate to severe: $z=3.269$ , $Padj=0.002$ ). Multiple logistic regression analysis showed that 25(OH)D3 and C3-epi-25(OH)D3 were significant predictors for CKD progression in RA patients, and C3-epi-25(OH)D3 had a better predictive advantage (moderate vs. mild: $\text{OR}=4.79$ , $P<0.001$ ; severe vs. mild: $\text{OR}=17.85$ , $P<0.001$ ). Conclusions. To the best of our knowledge, this is the first study to reveal that C3-epi-25(OH)D3 is a dominant predictor of CKD severity in RA patients. Further studies are needed to explore the relationship between C3-epi-25(OH)D3 and other diseases.

Maternal and Neonatal 3-epi-25-hydroxyvitamin D Concentration and Factors Influencing Their Concentrations

BACKGROUND

Little is known about the presence of 3-epi-25 hydroxyvitamin D in maternal and neonatal circulation, the extent of its contribution to total 25 hydroxyvitamin D, or factors influencing its levels.

METHODS

A total of 1502 and 1321 archived maternal and umbilical cord serum samples from the Hyperglycemia and Adverse Pregnancy Outcome Study cohort from Hong Kong were assayed for 25(OH)D2, 25(OH)D3, and isomeric form of 25(OH)D3 (3-epi-25(OH)D3) by a liquid chromatography-tandem mass spectrometry method.

RESULTS

Vitamin D deficiency (total serum 25(OH)D level < 50 nmol/L) and severe vitamin D deficiency (total serum 25(OH)D level < 25 nmol/L) occurred in 590 (39.3%) and 25 (1.7%) mothers, respectively. 3-epi-25(OH)D3 could be detected in 94.5% of maternal and 92.1% of neonatal umbilical sera, with the highest 3-epi-25(OH)D3 levels contributing to 19.9% and 15.3% of the maternal and umbilical cord sera 25(OH)D3 levels, respectively. Pregnancy with a male fetus, ambient solar radiation, and maternal glycemia and 25(OH)D3 levels were independent factors associated with maternal 3-epi-25(OH)D3 level. Advanced maternal age, multiparity, maternal gestational weight gain below the Institute of Medicine recommendation, maternal glycemic status, and earlier gestational age at delivery were significantly associated with higher umbilical cord serum 3-epi-25(OH)D3.

CONCLUSIONS

3-epi-25(OH)D3 accounted for a significant portion of total 25(OH)D in maternal and neonatal circulations. Further study is needed to determine the possible mechanism underlying this observation.

Longitudinal changes in vitamin D and its metabolites in pregnant South Africans

BACKGROUND

Vitamin D deficiency (VDD) has been associated with adverse maternal and foetal outcomes and is determined by measuring 25 hydroxyvitamin D (25(OH)D). The 25(OH)D is catabolized to 24, 25-(OH) ₂D and the ratio of 25(OH) D to 24, 25-(OH)₂D, the vitamin D metabolite ratio (VMR), is thought to be a superior marker of VDD, being elevated in such states. The aims of this study were to assess the longitudinal vitamin D status of pregnant women by measuring cholecalciferol, 25(OH)D, 24, 25-(OH)₂D and VMR at two time points and also to determine any association of vitamin D and metabolites with gestational age at birth, birth length and weight.

METHODS

We recruited 400 pregnant black African women in their first trimester (V1) and measured weights and heights. Ultrasound scans were performed for gestational age. Blood was drawn at V1 and at about 26 weeks (V2) of gestation for cholecalciferol, 25(OH)D, 24, 25-(OH)₂D, VMR and parathyroid hormone (PTH). An OGTT was performed at V2 where fasting glucose, insulin and 30-minute glucose were measured. At birth, we measured birth weight, length and gestational age. Maternal insulin, PTH and vitamin D binding protein (VDBP) were measured by immunoassay. Maternal albumin was measured colorimetrically. Maternal cholecalciferol, 25(OH)D and 24, 25-(OH)₂D, were measured by mass spectrometry and free and bioavailable vitamin D were calculated. Initial gestation was determined by ultrasound. We compared analytes by visit as well as by 25(OH)D status. Vitamin D deficiency (<30 nmol/L) was defined according to the National Academy of Medicine guidelines. Linear regression analysis was used to determine associations of vitamin D molecules with maternal blood pressure, fasting and 30-minute insulin and blood glucose and neonatal parameters.

RESULTS

Results are presented for participants for whom we had complete data (n = 330-346 depending on variable). The prevalence of vitamin D deficiency (VDD) was 35.8 % at V1 and 32.4 % at V2. Levels of 25(OH)D did not change significantly between visits. Levels of 24, 25(OH)₂D dropped from the first to the second visit (17.64 ± 12.64 to 9.39 ± 9.07 nmol/L; p < 0.0001) while VMR increased ((3.15 (1.31; 7.67) to 7.90 (2.44; 25.98); p < 0.0001). The proportion of women with the lowest cholecalciferol concentrations increased at V2 compared to the V1 (36.1-42.8 %; p = 0.02). In multivariable regression models 25(OH)D was negatively associated with 30-minute glucose concentrations (p = 0.038) whilst 24, 25-(OH)₂D was positively associated with fasting insulin (p = 0.017) and HOM A-I R (p = 0.023). There was no correlation of 25(OH)D or metabolites with infant birth weight, birth length or gestational age.

CONCLUSIONS

Maternal VDD is common in pregnant black South African women. Decreased VMR suggest that catabolism of 25(OH)D is reduced in pregnancy to maintain adequate free vitamin D levels.

Basal Vitamin D Status and Supplement Dose Are Primary Contributors to Maternal 25-Hydroxyvitamin D Response to Prenatal and Postpartum Cholecalciferol Supplementation

BACKGROUND

Variability in the 25-hydroxyvitamin D [25(OH)D] response to prenatal and postpartum vitamin D supplementation is an important consideration for establishing vitamin D deficiency prevention regimens.

OBJECTIVES

We aimed to examine interindividual variation in maternal and infant 25(OH)D following maternal vitamin D supplementation.

METHODS

In a randomized trial of maternal vitamin D supplementation (Maternal Vitamin D for Infant Growth Trial), healthy pregnant women (n = 1300) received a prenatal cholecalciferol (vitamin D-3) dose of 0, 4200, 16,800, or 28,000 IU/wk from 17 to 24 wk of gestation followed by placebo to 6 mo postpartum. A fifth group received 28,000 IU cholecalciferol/wk both prenatally and postpartum. In a subset of participants, associations of 25(OH)D with hypothesized explanatory factors were estimated in women at delivery (n = 655) and 6 mo postpartum (n = 566), and in their infants at birth (n = 502) and 6 mo of age (n = 215). Base models included initial 25(OH)D and supplemental vitamin D dose. Multivariable models were extended to include other individual characteristics and specimen-related factors. The model coefficient of determination (R2) was used to express the percentage of total variance explained.

RESULTS

Supplemental vitamin D intake and initial 25(OH)D accounted for the majority of variance in maternal 25(OH)D at delivery and postpartum (R2 = 70% and 79%, respectively). Additional characteristics, including BMI, contributed negligibly to remaining variance (<5% increase in R2). Variance in neonatal 25(OH)D was explained mostly by maternal delivery 25(OH)D and prenatal vitamin D intake (R2 = 82%). Variance in 25(OH)D in later infancy could only partly be explained by numerous biological, sociodemographic, and laboratory-related characteristics, including feeding practices (R2 = 43%).

CONCLUSIONS

Presupplementation 25(OH)D and vitamin D supplemental dose are the major determinants of the response to maternal prenatal vitamin D intake. Vitamin D dosing regimens to prevent maternal and infant vitamin D deficiency should take into consideration the mean 25(OH)D concentration of the target population.

Seasonal modulation of antibody response to diphtheria-tetanus-pertussis vaccination in infants: a cohort study in rural Gambia

BACKGROUND

In rural Gambia, rates of malnutrition and infection are higher during the annual rainy/'hungry' season (June-October) in comparison to the dry/'harvest' season (November-May). The effects of this seasonal pattern on an infant's immune development and their capacity to respond to childhood vaccinations remain unclear. The aim of the current analysis was to determine whether antibody responses to diphtheria-tetanus-pertussis (DTP) vaccinations in infants differ between seasons.

METHODS

Infants received the DTP vaccine at 8, 12 and 16 weeks of age and antibody titres were measured in blood samples collected at 12 (n = 710) and 24 (n = 662) weeks of age. Mean DTP antibody titres, adjusted for maternal and infant confounders, were compared by t-tests and the effect sizes of the mean differences were calculated between seasons at mid-gestation (20 weeks gestation) and first vaccination (8 weeks of infant age).

RESULTS

A smaller number of infants received their first vaccination during the rainy/hungry season months compared to the dry/harvest season (n = 224 vs. n = 486). At 12 weeks, infants vaccinated during the rainy/hungry season had lower weight-for-length Z-scores (p = 0.01) and were more likely to be anaemic (p < 0.001). Their mothers, however, were pregnant mostly during the dry/harvest season, had higher weight gain (p < 0.001) and were less likely to be anaemic during pregnancy (p < 0.001). At 12 weeks, infants vaccinated during the rainy/hungry season had significantly higher mean diphtheria, tetanus and pertussis antibody titres; by 62.3, 16.9 and 19.7%, respectively (all, p < 0.001). However, at 24 weeks, they had lower mean anti-diphtheria titres (by 20.6%, p < 0.001) compared with infants vaccinated during the dry/harvest season, and no differences were observed in mean tetanus and pertussis antibody titres by vaccination season.

CONCLUSIONS

Infant antibody response to the primary dose of the DTP vaccine was influenced by both season of pregnancy and infancy, although effects were diminished following three doses. Environmental exposures, including nutrition, to both the mother and infant are hypothesised as likely drivers of these seasonal effects.

The Paleolithic Nutrition Model in Relation to Ultraviolet Light and Vitamin D

The biology of every species has been optimized for life in the environment in which that species evolved. Humans originated in the tropics, and while some natural selection took place in response to behaviors and environments that decreased exposure to ultraviolet light, there has never been a species-wide biological accommodation. Paleolithic nutrition advocates argue that risk of disease is higher because modern diets differ from what was consumed by early humans. Early humans were the naked ape living in the tropics, exposed to high levels of ultraviolet light and vitamin D nutrition (serum 25-hydroxyvitamin D; 25(OH)D) averaging 115 nmol/L, as compared to today's population averages that are well below 70 nmol/L. Natural selection from an available gene pool cannot compensate fully to an environmental change away from the one within which the species originally evolved. Vitamin D nutrition remains a contentious area. The epidemiological evidence consistently relates lower 25(OH)D to higher disease risk. However, evidence from double-blind clinical trials looking at preventing new disease in healthy volunteers has been disappointing. But such negative trials have been the case for all nutrients except for folic acid which lowers risk of spina bifida. The Paleolithic nutrition model is based on fundamental biological concepts, but it has overlooked the environmental effects of ultraviolet light and vitamin D nutrition. This paper presents evolutionary and Paleolithic aspects of ultraviolet light and vitamin D with the aim to support pertinent research and, ultimately, public policy regarding nutrition and light exposure.