Eating of soil has been internationally practised throughout the world, in all age groups, races, and socio-economic environment [1]. The eating of clay (kaolin) occurs among cultural groups in many continents. Clay eating is widespread among women in Africa but in particular five African countries of Malawi, Zambia, Zimbabwe, Swaziland and South Africa, where an estimated prevalence level in the rural areas of these countries is put at 90% [2]. In human, it is postulated that kaolin consumption creates iron, zinc, or potassium deficiencies [3]. Kaolin ingestion is thought to inhibit absorption of iron from foods. Those who eat clay at the expense of healthier foods often develop malnutrition. This phenomenon of nutrient deficiency is exacerbated when clays with high cation-exchange capacities are ingested. Complications from geophagia include hypokalemia, hypogonadism, and iron deficiency [4]. In sub-Saharan Africa, the rate of geophagia among pregnant women ranges from 28% in Tanzania to 65% in Kenya [5], Geophagia has also been reported in Senegal, Mali [6], Guinea [7] as well as Nigeria [8]. Kaolin consumption (geophagia) is common among pregnant women, perhaps because of its anti-nausea effect [9]. A cross-sectional study showed that 46.4% of pregnant women in Southern Ebonyi State, Nigeria who were in attendance at antenatal clinics deliberately and regularly indulged in the habit of earth consumption [10]. Clay eating is observed among pregnant women in South Africa where the prevalence of pica among urban and rural black South African women was reported to be high [2]. There are reports that geophagia is common among the Tanzanians and Kenyans in the Eastern part of Africa, and that the prevalence remained high during pregnancy, and then declined after post-partum [11].

There is a hypothesis that geophagy is a physiological response to nutrients deficiencies, such as iron and calcium [12]. Pregnancy is a period of both increased nutritional needs and increased vulnerability Nutrition during pregnancy is increasingly demanding, especially regarding minerals such as iron and calcium, to support both the growing fetus and elevated blood production. Unfortunately, this period of nutritional need often occurs coincidentally with digestive difficulties such as nausea and vomiting. This, often enhances the eating of kaolin at first and second trimesters as anti-nausea agent [1]. Since kaolin consumption occurs during pregnancy, there is a likelihood of deleterious effects on both the mother and unborn child [13]. Kaolin has been noted to have adsorbing effect on other elements; thus chronic exposure may result in nutritional and electrolytes deficiency or even affect carbohydrate metabolism and intestinal enzyme activities, such as amylase. These likely biological consequences of kaolin consumption prompted this study in geophargic pregnant women.

The calcium content of kaolin was 10.6 mg/g while the estimated daily calcium intake by the three groups of pregnant women on kaolin was 151.6, 226.8 and 303.2 mg for 100, 150 and 200 g kaolin per week respectively. These values are below the recommended daily calcium intake of 1000 mg per day.

Our findings revealed that potassium level in kaolin consuming pregnant women significantly decreased in both 1^st and 2^nd trimester in a concentration dependent manner. A few studies have made similar observations [14] [15]. The low serum potassium in maternal blood could be attributed to cation binding activities of kaolin in the gastrointestinal tract [16]. This would reduce intestinal absorption and increased gastrointestinal loss of potassium. Hypokalaemia is a very dangerous situation in pregnancy as it can adversely affect both the mother and foetus. Hypokalaemia in pregnancy causes extreme muscle weakness and temporary paralysis of the arms and legs.

The reduced serum sodium level was noticeable in 2^nd trimester and at high kaolin concentration. This agreed with the report of Deloris et al. [17]. Low sodium concentration in 2^nd trimester may be as a result of increased plasma volume [18] [19]. The effect of kaolin consumption on plasma glucose was dependent on the quantity of kaolin consumed. The effect of unregulated and continuous kaolin consumption in pregnancy may manifest as gestational diabetes and its associated complications. The mechanism by which kaolin elevates plasma glucose is not known, however, previous findings revealed that some heavy metals were elevated in pregnant women on kaolin [20]. Heavy metals especially lead and arsenic had demonstrated inhibitory activities on insulin and were capable of inactivating over 200 enzymes [21]. It has been postulated that arsenite from kaolin has high affinity for sulphydryl group of insulin which can form a covalent bond with disulfide bridges in insulin receptors, thereby altering glucose metabolism [22]. An increased glucose level in maternal blood predisposes foetus to excessive birth weight, early (pretem) birth, respiratory distress syndrome, low blood sugar after birth, while the mother may exhibit high blood glucose and pre-eclampsia [23].

The low serum amylase level may be connected with kaolin adsorption of biomolecules. Studies have shown that kaolin can adsorb some substances [16] [24] [25] and may likely bind and inactivate intestinal enzymes. Though, clinical relevance of low serum amylase is poorly understood, animal and cellular studies regarding the relationship with endocrine and exocrine pancreas have shown that insulin secretion affected the basal and stimulatory amylase secretion via islet of acinar axis, and there was negative association between serum amylase and heavy metals [26]. High concentration of some heavy metals in geophargic pregnant women has been documented [20], and in biological systems heavy metals have been reported to inactivate enzymes, and affect cellular organelles and components [27].

There are significant reductions in the serum potassium, sodium and amylase levels, and increased plasma glucose level in geophargic pregnant level. There may be likelihood of gestational diabetes, electrolyte imbalance and low intestinal enzyme activity in geophargic pregnant women. Uncontrolled and unregulated consumption of kaolin by pregnant women as practised in many rural African communities may adversely impact on the outcome of pregnancy.

The authors wish to acknowledge the Antenatal Clinic, Chukwuemeka Odimegwu Ojukwu University Teaching Hospital (COOUTH), Awka, Anambra State, Nigeria for the permission to perform this study in the hospital.

Experiments were designed by PAA and MNO, and carried out by TOZ. Execution of the study was supervised by PAA and MNO. All the authors participated in the manuscript preparation which was directed by PAA. The final manuscript was approved by all the authors.

The authors declare no conflicting interest.

Zeigbo, T.O., Akah, P.A. and Ofokansi, M.N. (2020) Kaolin Consumption Affects Serum Electrolytes, Glucose and Amylase Levels of Pregnant Women. Journal of Biosciences and Medicines, 8, 160-168. https://doi.org/10.4236/jbm.2020.86015