Food and nutrition.pdf

Nutrients 73to nickel compounds have a higher than normal incidence of cancer ofthe respiratory tract, particularly of the nasal cavities and lungs. Nickelreleased from burning tobacco isthought to be responsible for at least partof the carcinogenicity of tobacco smoke. There is no indication of cancerarising from ingestion of the nickel in food.PhosphorusThe precise requirement for phosphorus is unknown, but a 1 to 1 ratioof calcium to phosphorus will provide sufficient phosphorus for most agegroups. The RDA for adults is 1200 milligrams.Phosphorus is an essential component of bone mineral and isnecessary for normal bone and tooth structure. It is involved in almost allphysiological chemical reactions. It aids in growth and can lessen the painof arthritis.The best natural sources are cereal grains, nuts, seeds, meat, poultryand fish.Aluminum hydroxide binds phosphorus, making it unavailable forabsorption. An excess of iron and magnesium have the same effect.Phosphorus deficiency results in bone loss and is characterized byweakness, anorexia and pain.PotassiumPotassium is the principal intercellular cation. There is no RDA but aminimum requirement of 1600 milligrams per day would be adequate.Potassium is of great physiological importance, contributing to thetransmission of nerve impulses, the control of skeletal muscle contractility,and the maintenance of normal blood pressure. Deficiency symptomsinclude weakness, anorexia, nausea, drowsiness and irrational behaviour.Potassium is found in most foods since it is an essential constituentof all living cells. The richest dietary sources are unprocessed beans, nuts,leafy green vegetables and fruit.Low blood sugar levels (hypoglycemia), alcohol or smoking causepotassium loss.Acute intoxication (hyperkalemia) can cause cardiac arrest and provefatal.SeleniumThe RDA is 70 micrograms for male adults, 55 micrograms for females.Selenium plays a role in pancreatic function, in hepatiC hememetabolism, and in the immune response. It has a close metabolicinterrelationship with the antioxidant vitamin E. Deficiency only occurssimu~taneously with a deficiency of vitamin E and can be cured by