Aflatoxin contamination of diets results in disease and death in humans and animals. The objective of the present paper was to review the development of innovative enterosorption strategies for the detoxification of aflatoxins. NovaSil clay (NS) has been shown to decrease exposures to aflatoxins and prevent aflatoxicosis in a variety of animals when included in their diets. Results have shown that NS clay binds aflatoxins with high affinity and high capacity in the gastrointestinal tract, resulting in a notable reduction in the bioavailability of these toxins without interfering with the utilization of vitamins and other micronutrients. This strategy is already being utilized as a potential remedy for acute aflatoxicosis in animals and as a sustainable intervention via diet. Animal and human studies have confirmed the apparent safety of NS and refined NS clay (with uniform particle size). Studies in Ghanaians at high risk of aflatoxicosis have indicated that NS (at a dose level of 0.25% w/w) is effective at decreasing biomarkers of aflatoxin exposure and does not interfere with levels of serum vitamins A and E, iron, or zinc. A new spinoff of this strategy is the development and use of broad-acting sorbents for the mitigation of environmental chemicals and microbes during natural disasters and emergencies. In summary, enterosorption strategies/therapies based on NS clay are promising for the management of aflatoxins and as sustainable public health interventions. The NS clay remedy is novel, inexpensive, and easily disseminated.

Clay, or more precisely, certain clay typologies, have been used traditionally by humans for therapeutic, nutritional, and skin-care purposes though they may be responsible for some relatively rare but significant health and skin-care risks. For example, clay particles could adsorb and make available for elimination or excretion any potential toxic elements or toxins being ingested or produced, but they could also adsorb and make available for incorporation, through ingestion or through dermal absorption, toxic elements, e.g. heavy metals. Geophagy has been observed in all parts of the world since Antiquity, reflecting cultural practices, religious beliefs, and physiological needs, be they nutritional (dietary supplementation) or as a remedy for disease. Some clays and clay minerals are employed widely in both the pharmaceutical and cosmetics industries as active compounds/agents and as excipients. In the biomedical field, some clay minerals such as halloysite and montmorillonite are known for their effective role as carriers for the control and sustainable delivery of active drug molecules, and in the biomaterials field some clay minerals are used for scaffold, hydrogel, foam, and film production. Constraints, both chemical and microbiological, on the use of clay-based products for therapeutic and cosmetic topical applications are generally imposed by sanitary regulations, and some solutions are proposed herein to control and reduce such restrictions. Particular emphasis is placed here on peloids and pelotherapy, as well as on manipulated and modified peloids, and specifically on tailored peloids or ‘designed and engineered’ peloids, and their derivatives, bactericidal peloids and ointments. As far as the so-called ‘killer clays’ are concerned, their pre-requisites, mechanisms of action, and disinfection role are also enhanced. Podoconiosis is an environment-related or geochemical disease that occurs in tropical highland areas, and is caused by long-term exposure of bare feet to volcanic, red-clay soil and affects some people, particularly those working in agriculture in some regions of Africa, Asia, and South America.

Clay is unique especially from the perspective of medical geology, that is, the impacts of geologic materials and geologic processes on animal and human health. Clay is the only natural material that can impact human health through all routes of exposure: ingestion, inhalation, and dermal contact. Moreover, these impacts can be harmful as well as beneficial. Ingestion of clay, a form of geophagy, has been practiced for millennia and is still widely practiced today. Humanoids have been ingesting clay for at least two million years to ease indigestion and counteract poisons. Some additional benefits may accrue from eating clays such as providing some nutrients but these benefits are far outweighed by the likely negative consequences such as tissue abrasion, intestinal blockage, anemia, exposure to pathogens and toxic trace elements, and potassium overdose. Inhalation of airborne minerals including clays has impacted the heath of millions. In the 1930s thousands of people living in the Dust Bowl in the U.S. southwest inhaled copious amounts of clay contributing to deadly ‘dust pneumonia.’ Using clay as a poultice to stem bleeding and cure certain skin ailments is an age-old practice that still has many adherents. A classic recent example of the antibacterial properties of clay is the use of certain clays to cure Buruli ulcer, a flesh eating disease. However, walking barefoot on clays in certain volcanic soils can result in non-filarial podoconiosis or elephantiasis. The absence of clays in soils can have serious health consequences. In South Africa, clay-poor soils yield crops lacking in essential nutrients and may be the principal cause of Msileni joint disease. Clearly, a detailed knowledge of the clays in the environment can have significant benefits to human health and wellbeing.

Geophagy is the intentional consumption of earth. Although widely documented among vulnerable populations, including children and pregnant women, the causes and consequences of geophagy remain poorly understood. Relevant literature was, therefore, reviewed to describe geophagy across species, geographies, life stages, and disease states. After a brief consideration of hypothesized etiologies, the potential harmful and beneficial consequences of geophagy are described, considering current evidence for each. Data available to date suggest that the greatest potential risks of geophagy include toxicity or heavy metal poisoning, and diseases resulting from consumed clays binding nutrients and beneficial pharmaceuticals in the gut. Evidence also suggests that geophagy may be beneficial by protecting against harmful pathogens and toxins through two distinct physiological pathways. Future research should explore causal relationships between geophagy and iron deficiency, as well as investigate the biological and psychosocial conditions that govern geophagy.

Anaemia is a public health problem in Ghana. We sought to identify factors associated with haemoglobin concentration (Hb) and anaemia among school-attending adolescents. We analysed data from 2948 adolescent girls and 609 boys (10–19 years) selected from 115 schools from regions of Ghana as a secondary analysis of baseline surveys conducted at two time-points. We measured Hb, malaria from capillary blood, anthropometry and used a modified food frequency questionnaire to assess diet. Multivariable linear and Poisson regression models were used to identify predictors of Hb and anaemia. The prevalence of anaemia, malaria and geophagy were 24, 25, and 24 %, respectively, among girls and 13, 27 and 6 %, respectively, among boys. Girls engaging in geophagy had a 53 % higher adjusted prevalence of anaemia and 0⋅39 g/dl lower Hb. There were similar results among those who tested positive for malaria (+52 % anaemia; −0⋅42 g/dl Hb). Among girls, lower anaemia prevalence and higher Hb were associated with consumption of foods rich in haeme iron (−22 %; +0⋅18 g/dl), consumption of iron-fortified cereal/beverages consumed with citrus (−50 %; +0⋅37 g/dl) and being overweight (−22 %; +0⋅22 g/dl). Age was positively associated with anaemia among girls, but negatively associated among boys. Boys who tested positive for malaria had 0⋅31 g/dl lower Hb. Boys who were overweight or had obesity and consumed flour products were also more likely to be anaemic (119 and 56 %, respectively). Factors associated with Hb and anaemia may inform anaemia reduction interventions among school-going adolescents and suggest the need to tailor them uniquely for boys and girls.

In Central Amazonia, large mammals create water-filled puddles when consuming soil. These mineral licks are visited by pregnant and lactating frugivorous bats; possibly for two reasons. Frugivorous bats could supplement their mineral-depleted fruit diet by drinking salty water, or they could buffer dietary plant secondary compounds by consuming soil. We analysed bat fruits from Ecuador and showed that they are depleted in elemental concentrations (Na, K, P) compared with similar fruits collected from Costa Rica, where no mineral licks occur (n = 32). Analyses of water from Ecuador revealed that water samples from six mineral licks contained more physiologically relevant elements (Na, K, Mg, Ca) than four samples from river and stream water control sites (Mann–Whitney U-test). In support of the nutrient supplement hypothesis, we observed bats drinking mineral-enriched water at these licks (video observation). Furthermore, blood collected from 68 bats differed in composition with respect to physiologically relevant minerals (Na, K, Mg, Fe) from that of frugivorous bats captured at control sites. To test whether frugivorous bats also consumed clay for detoxification, we checked for soil tracer elements in 31 faecal samples. Soil tracers are insoluble in water and, thus, are not included in a strict fruit diet. Bats from mineral licks showed higher aluminium soil tracer concentrations in their faeces than bat species that never visit licks, suggesting that frugivorous bats take up clay material at mineral licks. Our results provide evidence that frugivorous bats ingest soluble mineral nutrients and insoluble soil by consuming soil-enriched water at mineral licks, thus supporting the hypothesis that frugivorous bats of western Amazonia may derive a dual benefit from drinking water from mineral licks.

Natural licks are activity hotspots for frugivorous bats in the Peruvian Amazon. Large numbers of frugivorous bats congregate at licks to drink water. Because most Amazonian soils are relatively poor in nutrients, plants may contain low concentrations of some nutrients; consequently, frugivorous bats may face nutrient limitations. Accordingly, a potential explanation for lick visitation by bats is to obtain key limited resources. We assessed this hypothesis by comparing concentrations of cations (Ca, K, Mg, Na) in water at three licks and associated non-lick sites across years and seasons at Los Amigos Conservation Concession in south-eastern Peru. We also examined bat activity patterns between lick and non-lick sites. Regardless of the season, at licks >10 bats per net h−1 were captured compared with forest and gap sites where <1 bat per net h−1 was captured. At licks bats belonged primarily to the subfamily Stenodermatinae and over 70% were reproductive females. Although calcium, magnesium and potassium concentrations varied across water sources, sodium concentrations were consistently higher in lick water (>50 ppm) compared with creeks and oxbow lakes (<2 ppm) across seasons. Therefore, since sodium is one of the most limiting nutrients for vertebrates in the tropics, licks may function as sources of sodium (or other elements) for bats. In any case, licks are reliable potential sources of sodium in the south-eastern Peruvian Amazon, an otherwise mineral-poor landscape.

Transmission of Oesophagostomum dentatum and Trichuris suis was studied in outdoor reared pigs. Six farrowing paddocks were naturally contaminated in May to mid-June 2001 by experimentally infected seeder pigs. In early July 1 sow farrowed on each paddock and starting at week 3 post-partum (p.p.) the offspring was slaughtered serially every 2 weeks for parasite recovery. Faeces were collected regularly for parasite egg counts and acid-insoluble ash (AIA) content as an indicator of geophagy. Weaning took place at week 7 p.p. by removing the sow. Paddock infection levels were estimated in mid-June (O. dentatum) and late November (O. dentatum and T. suis) using helminth-naïve tracer pigs. Soil and vegetation samples were collected regularly. Despite a high initial contamination by the seeder pigs, O. dentatum paddock infectivity was negligible to low throughout the raising of the experimental piglets, which had a slow accumulation of nodular worms ending with a mean of 422 worms/pig at week 19 p.p. As only few eggs developed to infectivity overall T. suis transmission was minimal. The first T. suis were recovered at week 11 p.p. and the highest mean burden of 21 worms/pig was recorded at week 19 p.p. The experimental pigs initially had a high faecal level of AIA although it decreased over time. The results are discussed in relation to the biological characteristics of the 2 parasites and their occurrence in organic pig production.

Subsamples of termite mound soil used by chimpanzees for geophagy, and topsoil never ingested by them, from the forest floor in the Mahale Mountains National Park, Tanzania, were analysed to determine the possible stimulus or stimuli for geophagy. The ingested samples have a dominant clay texture equivalent to a claystone, whereas the control samples are predominantly sandy clay loam or sandy loam, which indicates that particle size plays a significant role in soil selection for this behaviour. One potential function of the clays is to bind and adsorb toxins. Although both termite mound and control samples have similar alkaloid-binding capacities, they are in every case very high, with the majority of the samples being above 80%. The clay size material (<2 μm) contains metahalloysite and halloysite, the latter a hydrated aluminosilicate (Al2Si2O4·nH2O), present in the majority of both the termite mound soil and control soil samples.Metahalloysite, one of the principal ingredients found in the pharmaceutical Kaopectate™, is used to treat minor gastric ailments in humans. The soils commonly ingested could also function as antacids, as over half had pH values between 7.2 and 8.6. The mean concentrations of the majority of elements measured were greater in the termite mound soils than in the control soils. The termite mound soils had more filamentous bacteria, whereas the control soils contained greater numbers of unicellular bacteria and fungi.

The golden-faced saki monkey Pithecia pithecia chrysocephala (Cebidae, Primates) was observed eating soil from termite nests during a long-term study of a family group in a Central Amazonian forest fragment. In this paper we describe the behaviour involved in the geophagy in these monkeys, and the results of geochemical and physical analyses of the termite nest material, as well as root mat and topsoil samples below the trees, in order to clarify the possible reasons for it. The sakis ate soil from nine arboreal termite nests on 26 soil feeding-bouts (in 853 observation hours); 25 soil feeding-bouts occurred in March 1987 (rainy season), during 19 days or 132 observation hours, and occupied 0.7% of the feeding time. Geophagy frequencies did not differ between sexes (17 feeding-bouts of four females and 8 for two males). Mineral composition was higher in arboreal termitaria than in the topsoil. Kaolinite was the major clay component. Tannin adsorptive capacity, tested through a modified radial diffusion method of Hagerman, was around 10–20%, similar to a control with kaolin (10–20%), but lower than bentonite or celite (30–45%). The observations reported here, although inconclusive as to the function of geophagy in this species, indicate that it is not a mineral supplement during times of scarcity or high consumption of leaves, as has been reported for other primates, nor that it is related to fruit consumption (redressing possible mineral imbalance), as has been suggested for some other frugivorous mammals. Our results do not rule out tannin adsorptive hypothesis for the ingestion of clays, but, being an irregular habit, we argue that it is most likely related to rare and occasional dietary components.

Geophagy (soil eating) by the forest elephant (Loxodonta africana cyclotis) and other mammal species in the Dzanga National Park, Central African Republic, has led to large treeless licks. The geological and physical properties of these licks were studied and the chemical characteristics and particle sizes of geophagical lick soils were compared with soils from the forest and from licks where evidence of geophagy was absent. Average lick size of 20 licks in the Hokou lick area was 12,900 m2 (SE = 3,400 m2). Licks were situated exclusively in areas of outcropping dolerite intrusions. Physico-chemical analysis of the geophagical lick soil showed significantly higher quantities of sodium, potassium, calcium, magnesium, phosphorus, manganese and clay compared with the other soils. Several samples of the geophagical lick soil had lower nutrient levels than the mean level of forest topsoil, indicating that nutrient supplementation is probably not the only reason for geophagy. The high clay content of the geophagical soil may help absorbing and combating secondary plant compounds. Pronounced geophagy in rainforests may be a sign for poor habitat quality for large mammals living in these ecosystems.