Effect of ß-hydroxybutyrate monoester on markers of iron metabolism in new-onset prediabetes: findings from a randomised placebo-controlled trial.

Background: People with prediabetes often have altered iron metabolism and may benefit from mild exogenous ketosis, which can now be successfully achieved thanks to recent developments in chemistry of food components. Objective: The objective was to investigate the effect of acute exogenous ketone monoester (ß-hydroxybutyrate) on plasma levels of markers of iron metabolism in people with prediabetes. Methods: Eighteen participants with new-onset prediabetes after acute pancreatitis aged 18 years or above took part in randomised controlled cross-over trial in Auckland, New Zealand. After an overnight fast, participants consumed the exogenous ketone supplement or placebo. Blood samples were collected in the fasted state (0 minutes) and then serially every 30 minutes for 150 minutes. Both participants and study personnel were blinded to the intervention/placebo allocation. Repeated measures analysis of variance was performed using total area under the curve to determine the change in hepcidin and ferritin over time after consumption of the exogenous ketone supplement and placebo. Results: Consumption of the exogenous ketone supplement significantly elevated blood levels of ß-hydroxybutyrate from 0.20 mmol L-1 at baseline to 3.50 mmol L-1 at 30 minutes (p < 0.05) and remained significantly elevated for the duration of the trial. The total area under the curve of hepcidin was 340.5 ± 121.1 ng mL-1 after the exogenous ketone supplementation as compared with 343.2 ± 119.6 ng mL-1 min-1 after the use of placebo (p = 0.91). The total area under the curve of ferritin was 786.7 ± 129.1 ng mL-1 min-1 after the exogenous ketone supplementation as compared with 776.9 ± 131.4 ng mL-1 min-1 after the use of placebo (p = 0.10). Conclusion: Acute supplementation of ß-hydroxybutyrate did not significantly affect the circulating levels of hepcidin or ferritin in people with prediabetes. Long-term effects of ß-hydroxybutyrate warrant investigations in the future.

Prevalence of vitamin D deficiency in Africa: a systematic review and meta-analysis.

BACKGROUND: Vitamin D deficiency is associated with non-communicable and infectious diseases, but the vitamin D status of African populations is not well characterised. We aimed to estimate the prevalence of vitamin D deficiency in children and adults living in Africa. METHODS: For this systematic review and meta-analysis, we searched PubMed, Web of Science, Embase, African Journals Online, and African Index Medicus for studies on vitamin D prevalence, published from database inception to Aug 6, 2019, without language restrictions. We included all studies with measured serum 25-hydroxyvitamin D (25[OH]D) concentrations from healthy participants residing in Africa. We excluded case reports and case series, studies that measured 25(OH)D only after a clinical intervention, and studies with only a meeting abstract or unpublished material available. We used a standardised data extraction form to collect information from eligible studies; if the required information was not available in the published report, we requested raw data from the authors. We did a random-effects meta-analysis to obtain the pooled prevalence of vitamin D deficiency in African populations, with use of established cutoffs and mean 25(OH)D concentrations. We stratified meta-analyses by participant age group, geographical region, and residence in rural or urban areas. The study is registered with PROSPERO, number CRD42018112030. FINDINGS: Our search identified 1692 studies, of which 129 studies with 21 474 participants from 23 African countries were included in the systematic review and 119 studies were included in the meta-analyses. The pooled prevalence of low vitamin D status was 18·46% (95% CI 10·66-27·78) with a cutoff of serum 25(OH)D concentration less than 30 nmol/L; 34·22% (26·22-43·68) for a cutoff of less than 50 nmol/L; and 59·54% (51·32-67·50) for a cutoff of less than 75 nmol/L. The overall mean 25(OH)D concentration was 67·78 nmol/L (95% CI 64·50-71·06). There was no evidence of publication bias, although heterogeneity was high (I2 ranged from 98·26% to 99·82%). Mean serum 25(OH)D concentrations were lower in populations living in northern African countries or South Africa compared with sub-Saharan Africa, in urban areas compared with rural areas, in women compared with men, and in newborn babies compared with their mothers. INTERPRETATION: The prevalence of vitamin D deficiency is high in African populations. Public health strategies in Africa should include efforts to prevent, detect, and treat vitamin D deficiency, especially in newborn babies, women, and urban populations. FUNDING: Wellcome Trust and the DELTAS Africa Initiative.