the act of eating the earth including clay and chalk is neither new nor outdated .
geophagia , the practice of eating earth is associated with religious beliefs , medicinal and dietary purposes . the implication of this act is the exposure to toxic substances and parasites that are present in the ingested earth.[24 ] one of such geophagic materials is the calabash chalk , consumed largely in west africa as a remedy for morning sickness ; hence it is highly patronized by pregnant women.[57 ] the chalk is found largely in nigeria and other west african communities .
it is also found in ethnic stores and markets in the united states of america and the united kingdom .
different names have been ascribed to this chalk : calabar stone in english , la craie or argile in french , mabele by lingala in congo , nzu by igbo and ndom by the efik / ibibio of nigeria.[57 ] the major component of c. chalk is aluminum silicate hydroxide from the kaolin clay group , with a possible formula al2si2o2(oh)4 .
this chalk is available in varieties of forms including powder , molded shapes and blocks .
lead concentration in c. chalk has been reported to be approximately 40 mg / kg .
this concentration of lead in the c. chalk is far more than the approved dietary concentration .
other toxic elements including aluminum , silicon , alpha lindane , endrin , and endosulfan 11 have also been reported .
research carried out with the chalk on rats revealed fragmentation of the parenchymal cells , and dilation of sinusoids of the liver due to treatment with the chalk .
another report has it that it alters the normal concentration of hemoglobin , red blood cell counts and erythrocyte sedimentation rate ( esr ) , of female rats . since there are reports that this chalk contains heavy metals and other toxic substances , the deposition of these substances in the bone tissue may result in bone disorders and poor growth .
lead , a constituent of this chalk can be localized in areas of bone mineralization and growth .
it has been reported that lead adversely influences bone development through disruption of mineralization during growth .
as there are no clinical studies , it is important therefore to investigate the effect of c. chalk on the morphometry and mineralization of the bone in experimental animals with the aim of relating the findings to human situation , hence this study was conducted .
fourteen young ( weanling ) wistar rats of both sexes weighing 54 - 72 g , obtained from the animal house , faculty of basic medical sciences , university of uyo , were housed in wooden cages with saw particles as bedding .
the animals were handled in accordance with international regulation governing the use of laboratory animals .
the rats were fed with normal commercial pellet ( vital feed , grand cereal ltd , plateau state , nigeria ) and water was allowed ad libitum throughout the period of the experiment .
the room temperature of the experimental animal house ranged between 26 - 29c , with 12:12 hour light and dark cycle .
the animals were allowed to acclimatize for 7 days before the beginning of the experiment .
group i served as the control group ( cg ) , while group ii served as test group ( tg ) .
non - salted calabash chalk was bought from a local market in ikot omin , calabar , nigeria .
40 g of the chalk powder was dissolved in 1 liter of water to give a suspension which was stirred prior to administration .
animals in cg were treated with 1ml of distilled water , while those in tg were treated with 1ml of c. chalk suspension containing 40 mg / ml of the non - salted c. chalk .
treatment was given in the morning hours of 8 - 9 am and lasted for 28 days . on day 29 , the weight of the animals was noted , and the animals were sacrificed by humane killing using chloroform anesthesia .
the weight of the femur bones was measured using a digital weighing balance to the nearest 0.01 g .
the length was measured from the head to the condyles of the femur , by means of a measuring tape to the nearest 0.1 mm .
the sum of the weight of both the right and left femur were taken as the organ weights , and the organ - somatic index of the femur bones in both groups was computed ( organ somatic index = organ weight / body weight ) .
the femur bones were digested using analytical grade nitric acid ( 3 ml per tissue ) .
acid digest were diluted appropriately with double distilled - deionized water before analysis of the minerals .
bone phosphate ( p ) concentration was determined using the acid - molybdate method , and the absorbance read at 400 nm . the analysis for zinc ( zn )
sodium ( na ) , potassium ( k ) and calcium ( ca ) were carried out using graphite furnace atomic mass spectrophotometer and absorbance read at 589 nm , 766.5 nm and 422.7 nm respectively .
data were statistically analyzed using standard student t - test and the results presented as mean  standard deviation .
data were statistically analyzed using standard student t - test and the results presented as mean  standard deviation .
on day 6 of administration , the fecal boluses of the test group ( tg ) animals were softer in consistency than those of the control group ( cg ) animals . on day 8
, the color of the fecal bolus of the tg was found to be brown to milky color , and this fecal color was maintained till the end of the experiment , unlike the cg that had brownish brown color of fecal bolus .
the mean initial body weights ( g ) of the tg animals were significantly lower ( p < 0.0006 ) compared with the cg , while the mean final body weights of the tg animals were also significantly lower ( p < 0.0008 ) compared with the cg . the mean change in body weight of the animals in the tg and cg were 52.17 g ( 47% ) and 66.29 g ( 48.6% ) , respectively [ table 1 ] .
the lengths of the femur bones in the tg were slightly shorter in both the right and the left sides compared to the cg .
there was also an insignificant decrease in the weight of both the right and left femur bones of the tg when compared to the cg [ table 2 ] .
weight of animals of the control and test groups weight and length of femur bones of the control and test groups the organ - somatic index in the tg and cg was 0.0025  0.008 and 0.0033  0.004 respectively , with a statistically significant difference ( p < 0.0126 ) .
the mean femur bone concentration ( mg / l ) of zn , p , ca , na , and k were significantly lower ( p < 0.05 ) in the tg compared to the cg [ table 3 ] .
calabash chalk has been reported to contain lead , arsenic and persistent organic pollutants among other substances . the mean concentration of lead as reported by dean et al .
was approximately 40 mg / kg which far exceeded the european union recommended safety level for dietary lead by 40 fold .
this and other heavy metals present in this chalk are likely to interfere with the normal process of bone formation . in this study , we investigated the effect of the chalk on bone mineralization and other morphological changes in experimental wistar rats .
there was 1.6% decrease in body weight change of the test group ( tg ) .
this may result from disruption in nutrient absorption by the chalk , as kaolin , its major constituent , has been reported to coat the lining of the gastrointestinal tract . as a result of this
, the coating may have prevented the absorption of beneficial nutrients leading to poor nutrition , which ultimately resulted in a limited body weight gain reported in this study . beside this , poor nutrition can also increase the risk to other adverse health effects .
as one of the poisonous substance found in the chalk , lead may have played a significant role in the body weight reduction observed in this investigation .
there were no significant change in the length and weight of each of the right and left femur bones of tg compared to cg , and no significant change between the right and left femur bones in all the parameter measures in both groups .
this may be due to the significant change in body weight observed in this study .
furthermore , the results of our investigation showed a significant decrease in the bone minerals content in tg , which may be due to the combined effects of lead and other toxic elements present in the c. chalk . also , the developing skeleton is much more sensitive to toxicity than that of the adult .
lead accumulates and substitutes calcium in bone tissues and the resultant effect is that of disruption of mineralization , alteration of compositional properties and bone formation mechanisms , as well as the gradual depletion of bone minerals.[2123 ] lead has also been implicated in reduction of bone strength , oxidative stress , reduced zn , na , copper ( cu ) and iron ( fe ) in rat bone . and impaired bone mineral density and content .
the reduction in bone mineralization could lead to an increase in bone fragility and osteoporosis .
our study is at variance to a report by jamieson et al . according to this report , femoral
, the effect of calabash chalk on femur bone morphometry and mineralization of young wistar rats showed that c chalk may alter growth rate , and cause de - mineralization in the femur bone , and hence it may be detrimental to bone growth .
as this is a case in rats , a clinical trial could be carried out on humans to determine its effects .
 background : calabash chalk , a popularly consumed geophagic material in nigeria has been reported to contain lead , arsenic , alpha lindane , endrin , and endosulfan 11 among other pollutants.aim:the continuous exposure of young children to this chalk necessitated this study on the bone morphometry and mineralization in young wistar rats.materials and methods : fourteen young ( weanling ) wistar rats of both sexes weighing 54 - 72 g were assigned into two groups of seven animals each . 
 group i served as control , while group ii was the test group ( tg ) . 
 40 mg / ml of c. chalk was administered as suspension to the test animals in group ii . 
 animals in the control group were orally treated with 1ml of distilled water . 
 administration of the c. chalk in the animals lasted for 28 days , and the animals were sacrificed on day 29 , using chloroform anaesthesia . 
 the femur bones were dissected out , cleaned of flesh and sun - dried . 
 the lengths and weights of the femur bones were measured using graphite furnace atomic mass spectrophotometer.results:results showed 1.6% decrease in body weight change in the tg , insignificant decreases in the weights and lengths of both the right and left femur bones , and significant decreased ( p < 0.0126 ) organ - somatic index , and femur bones concentrations ( mg / l ) of zinc , phosphate , carbonate , calcium , sodium , and potassium ( p < 0.05).conclusion : in conclusion , this study showed that c. chalk may alter growth rate , and cause de - mineralization in the femur bone , hence , it may be detrimental to bone growth . 