Policy decisions and the practice of public health nutrition need to be based on solid evidence, developed through rigorous research studies where objective measures are used and results that run counter to dogma are not dismissed but investigated. In recent years, enhancements in study designs, and methodologies for systematic reviews and meta-analysis, have improved the evidence-base for nutrition policy and practice. However, these still rely on a full appreciation of the strengths and limitations of the measures on which conclusions are drawn and on the thorough investigation of outcomes that do not fit expectations or prevailing convictions. The importance of ‘hard facts’ and ‘misfits’ in research designed to advance knowledge and improve public health nutrition is illustrated in this paper through a selection of studies from different stages in my research career, focused on the nutritional requirements of resource-poor populations in Africa and Asia.

Recent research points to a renewed scholarly interest in the West African Middle Ages and the Sahelian imperial tradition. However, in these works only tangential attention is paid to the role of Muslims, and especially to clerical communities. This essay tackles theoretical and historiographical insights on the role of African Muslims in the era of the medieval empires and argues that the study of Islam in this region during the Middle Ages still suffers from undertheorizing. On the contrary, by using a ‘discursive approach’ scholars can unravel access to fascinating aspects of the history of West African Muslims and in particular to the crucial role played by clerical communities, who represented one node of the web of diffused authority which is characteristic of precolonial West African social and political structures.

The life of Ayuba Sulayman Diallo (also known as Job ben Solomon) receives a fresh examination in this article, based primarily on his own writings. The son of an Imam from Bundu in Senegambia, Diallo was enslaved in 1731 and transported to America. He survived to gain his freedom, make his mark in London society, and return to Africa in 1734. This article offers an analysis of documents from the British Library, including items that have not been previously analysed and are here translated into English for the first time. In addition, they bring together what is known of his archive, including the letters he wrote before, during, and after his time in London, the Qur'ans he scribed there, and the scraps and snippets created as he discussed the Arabic language with friends.

A close analysis of Diallo's writings reveals new information about his life history; his relationships with the elites in both Bundu and London; his scholarly abilities; and the history of Bundu itself. Diallo used the technology of writing to direct the course of his own life and career, converting a disastrous course of events into favourable opportunities for himself.

Exposures during the early life (periconceptional, prenatal and early postnatal) period are increasingly recognized as playing an important role in the aetiology of chronic non-communicable diseases (NCD), including coronary heart disease, stroke, hypertension, Type 2 diabetes and osteoporosis. The ‘Developmental Origins of Health and Disease’ (DOHaD) hypothesis states that these disorders originate through unbalanced nutrition early in life and risk is highest when there is a ‘mismatch’ between the early- and later-life environments. Thus, the DOHaD hypothesis would predict highest risk in countries where an excess of infants are born with low birth weight and where there is a rapid transition to nutritional adequacy or excess in adulthood. Here, I will review data from work conducted in rural Gambia, West Africa. Using demographic data dating back to the 1940s, the follow-up of randomized controlled trials of nutritional supplementation in pregnancy and the ‘experiment of nature’ that seasonality in this region provides, we have investigated the DOHaD hypothesis in a population with high rates of maternal and infant under-nutrition, a high burden from infectious disease, and an emerging risk of NCDs.

The end of internal slavery in West Africa is generally associated with an increase in labour mobility. This article complicates this picture by showing that the effects of status – the rank effect – on people's ability to migrate often outlasted emancipation. In Sabi, a Soninke village in Upper River Gambia, economic migration intensified and globalised from the 1950s onwards. Although they have since been free to move, the descendants of slaves have migrated less than those of the freeborn. The article attributes this relative immobility to the enduring dynamics of socioeconomic marginalisation based on slave descent.

25-Hydroxyvitamin D (25(OH)D) half-life is a potential biomarker for investigating vitamin D metabolism and requirements. We performed a pilot study to assess the approach and practical feasibility of measuring 25(OH)D half-life after an oral dose. A total of twelve healthy Gambian men aged 18–23 years were divided into two groups to investigate the rate and timing of (1) absorption and (2) plasma disappearance after an 80 nmol oral dose of 25(OH)D2. Fasting blood samples were collected at baseline and, in the first group, every 2 h post-dose for 12 h, at 24 h, 48 h and on day 15. In the second group, fasting blood samples were collected on days 3, 4, 5, 6, 9, 12, 15, 18 and 21. Urine was collected for 2 h after the first morning void at baseline and on day 15. 25(OH)D2 plasma concentration was measured by ultra-performance liquid chromatography-tandem MS/MS and corrected for baseline. Biomarkers of vitamin D, Ca and P metabolism were measured at baseline and on day 15. The peak plasma concentration of 25(OH)D2 was 9·6 (sd 0·9) nmol/l at 4·4 (sd 1·8) h. The terminal slope of 25(OH)D2 disappearance was identified to commence from day 6. The terminal half-life of plasma 25(OH)D2 was 13·4 (sd 2·7) d. There were no significant differences in plasma 25(OH)D3, total 1,25(OH)2D, parathyroid hormone, P, Ca and ionised Ca and urinary Ca and P between baseline and day 15 and between the two groups. The present study provides data on the plasma response to oral 25(OH)D2 that will underpin and contribute to the further development of studies to investigate 25(OH)D half-life.

This article begins with a quotation from a local informant highlighting a perception in the Gambia/Casamance borderlands that there is a pattern linking the violence of the later nineteenth century with more recent troubles. It argues that there is some merit in this thesis, which is encapsulated in a concatenation of events: systematic raiding by Fodé Sylla led to the creation of a relatively depopulated colonial border zone which was later filled by Jola immigrants from Buluf to the southeast. In the perception of some, it is these immigrants who attracted the MFDC rebels. Mandinkas and Jolas of Fogny Jabankunda and Narang, and Karoninkas from the islands of Karone have therefore been largely unreceptive to appeals to Casamance nationalism. The article also argues that there are more twisted historical connections. Whereas in the later nineteenth century, the Jolas associated Islam with violent enslavement, they later converted en masse. Their attitude towards Fodé Sylla remained negative, whilst the Mauritanian marabout, Cheikh Mahfoudz, was credited with the introduction of a pacific form of Islam that valorized hard work and legitimated physical migration. This legacy has posed a further barrier to militant nationalism. Islam and violence remain linked, but the signs have been reversed.

In rural Gambia the risk of mainly infection-related mortality is 10-fold higher for adults born in the nutritionally-debilitating ‘hungry’ season, suggesting that immune function may be compromised by events early in life. The current programme of research focuses on the biological mechanisms underlying this hypothesis, exploring early-life environmental influences on immune development and the long-term functional consequences these influences may have. Results obtained to date show that thymus development during infancy is critically sensitive to environmental exposures, with smaller thymuses observed in the hungry season. Measurement of the frequency of T-cell receptor excision circles indicate that thymus function is also sensitive to seasonal influences, with further studies implicating variations in breast-milk IL-7 as a possible mediator of these effects. Studies in adults have shown that size at birth is positively correlated with antibody responses to vaccination with polysaccharide antigens, thus providing evidence for long-term functional deficits. The present paper will review progress made to date within this field of research.

The disease risk indicator plasma total homocysteine (tHcy) is influenced by genetic and environmental factors, including folate and vitamin B12 status. Little is known about the determinants of tHcy in rural West Africa. We explored the hypothesis that tHcy in rural Gambian adults might vary between the sexes and physiological groups, an/r with folate and vitamin B12 status. Comparisons were made with a British national survey. Non-pregnant Gambian women (n 158) had tHcy concentrations (geometric mean 9·0μmo/) similar to those of non-pregnant UK women (n 449; 9·4μmo/), whereas pregnant Gambian women (n 12) had significantly lower values (6·2μmo/). Gambian men (n 22) had significantly higher values (14·7μmo/) than British men (n 354; 10·8μmo/). Gambian lactating women and British men and women exhibited significant inverse relationships between loge(tHcy) and folate status; however, only the British subjects exhibited significant inverse relationships between loge(tHcy) and vitamin B12 status. In the British sample, and in Gambian lactating women, folate and vitamin B12 status variations together accounted for 20–25% of the variation in loge(tHcy). Within the UK, black-skinned adults had folate and tHcy levels similar to those of their white-skinned counterparts, but significantly higher vitamin B12 values. We conclude that, whereas folate and vitamin B12 status are similar between British and rural Gambian populations, tHcy is higher in Gambian men and lower in pregnant Gambian women, and that serum vitamin B12 values appear to be higher in black-skinned than white-skinned British subjects. Possible reasons are discussed.

The Gambia Estuary, a “normal” estuary with a decreasing salinity gradient from the mouth towards the head, is moderately exploited by small-scale fisheries and does not receive any severe pollution from either agriculture or industrial activities. Neither the Gambia River nor its estuary are artificially impounded. As the last large West African estuary free of major human disturbance, it is of considerable interest for comparative studies on the effect of major environmental perturbations in West African estuarine ecosystems. The aquatic environment and fish communities of the Gambia Estuary (about 250 km long) were studied by purse seine sampling at different periods in the river cycle, covering all hydro-climatic seasons that are characteristic of West African estuaries. Emphasis was placed on the diversity, composition, structure and distribution of fish assemblages in relation to fluctuations in physico-chemical factors such as water temperature, salinity and turbidity. Results on the aquatic environment, mainly the salinity range (from freshwater to 39) and dissolved oxygen (never a limiting factor for fish in the estuary) and on the main characteristics of the fish fauna (high diversity of life cycles, all the ecological categories represented) indicated that the Gambia Estuary was free of major climatic perturbation and reinforced the choice of this system as a reference for the study of the effects of major perturbations on estuarine tropical fish communities.

The Gambia Estuary is one of the last estuaries in West Africa not to have been affected by strong environmental changes and adverse human disturbances. In order to describe the spatio-temporal change in fish biomass in this estuary, and the seasonal changes in fish size classes, five research surveys have been conducted at characteristic periods in the river's water regime and meteorological seasons. The fish assemblages were sampled by two vertical echosounding protocols: mobile surveys (zigzag transects) in the estuary and moored stations. The two sampling methods produced a similar image of the fish assemblages in terms of the distribution of total biomass and target strength distributions. Large fish aggregations were detected in the most marine area at the end of the wet season, and fish biomass increased through the dry season in the upstream zone. Fish were smaller at the beginning of the wet season and they were always larger in downstream areas.