title: Nutrition of lead.
abstract: At the levels to which human beings are exposed in the workplace as well as in the general environment, lead has been shown to be a toxic element in most of its chemical forms, whether it is inhaled or ingested in water or food. The four main sources of contamination of food are soil, industrial pollution, agricultural technology and food processing. Reasonable quantities of the metal can be stored by humans in a relatively inert form in bone; lead has an affinity for bone and acts by replacing calcium. Gastrointestinal lead absorption and retention, the major pathway of lead intake, has been shown to vary widely depending on the chemical environment of the gastrointestinal lumen, age and iron stores (nutritional status of the subject). Studies in animals have shown that certain substances bind lead and increase its solubility, thus enhancing its absorption. These dietary components consist of sodium citrate, ascorbate, amino acids, vitamin D, protein and fat, and lactose. Data suggest a three-compartmental pool for lead metabolism: (1) blood; (2) soft tissue (hair, nails, sweat, salivary, gastric, pancreatic and biliary secretions); and (3) skeleton. Lead absorption occurs primarily in the duodenum where lead enters the epithelial mucosal cells. The total bodily amount of lead does not affect lead absorption; lead does not have a feedback mechanism which limits absorption. In the adult rat, lead absorption from the intestinal lumen appears to proceed by both active transport and passive diffusion. Bile is an important route of excretion in the gut.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001842:Bone and Bones / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D004041:Dietary Fats / Q000378:metabolism; D002149:Energy Intake; D005260:Female; D006418:Heme / Q000378:metabolism; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007408:Intestinal Absorption; D007501:Iron / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D007854:Lead / Q000378:metabolism*; D007855:Lead Poisoning / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009747:Nutritional Physiological Phenomena; D011247:Pregnancy; D014018:Tissue Distribution; D014810:Vitamin E / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D014810:Vitamin E; D007854:Lead; D006418:Heme; D007501:Iron; D007785:Lactose; D015032:Zinc