(1) The geophagy of less than 20% of the children accounted for greater than 60% of the total soil ingested.
(2) Clays employed historically in the consumption of astringent acorns plus seven edible clays from Africa were examined in relation to the functional significance of human geophagy.
(3) We suggest that the physiological significance of geophagy made it important in the evolution of human dietary behavior.
(4) The most common form of pica, geophagy, has direct adverse nutritional effects and also exposes children to soil-borne infection.
(5) Existing methods for assessing geophagy are either inappropriate for field use (radiology) or unreliable (reporting).
(6) Faecal levels of dietary silica (less than 2% dry wt stool) can be distinguished from levels due to geophagy (up to 25% dry wt stool).