Food and nutrition.pdf

122 Function of Fooddigestive tracts. However, fermented vegetable products may providevitamin B12 in human diets .•Human RequirementsThe human daily requirement of this vitamin is ~uite small, probablyaround 3flg for adults. Diets containing smaller amounts do not seem tolead to disease.DeficiencyPernicious anaemia is not caused by a dietary deficiency of vitaminB12 but by an inability of the subject to utilize the vitamin B12 in the dietbecause of a lack of an intrinsic factor in gastric secretions. It may be thatan autoimmune reaction limits absorption of vitamin B12 In perniciousanaemia the red blood cells are macrocytic (larger than normal) and thebone marrow contains many abnormal cells called megaloblasts. Thismacrocytic or megaloblastic anaemia is accompanied by a lack ofhydrochloric acid in the stomach (achlorhydria). Later, serious changestake place in the spinal cord, leading to progressive neurologicalsymptoms. If left untreated, the patient dies.Treatment consists of injection of large doses of vitamin B12 Whenthe blood characteristics have returned to normal, the patient can usuallybe maintained in good health if given one injection of 250 mg of vitaminB12 every two to four weeks.Vitamin B12 will also cure the anaemia ac~ompanying the diseasesprue. This is a tropical condition in which the absorption of vitamin B 12,folic acid and other nutrients is impaired.The tapeworm Diphyllobothrium latum, acquired from eating raw orundercooked fish, lives in the intestines and has a propensity for removingvitamin B12 from the food of its host. This results in the development inhumans of a megaloblastic anaemia which can be cured by injection ofvitamin B12 and treatment to rid the patient of the tapeworm.Some medicines interfere with absorption of vitamin B 12.Except in the deficiency of vitamin B12 is likely to occur only in thoseon a vegetarian diet. Deficiency causes macrocytic anaemia and mayproduce neurological symptoms; however, even though strict vegetariansget very little vitamin B12 in their diet, it appears that macrocytic anaemiadue to vitamin B12 deficiency is not prevalent and is not a major publichealth problem.Folic Acid or FolatesIn 1929 Lucy Wills first described a macrocytic anaemia (an anaemiain which the red cells are abnormally large) commonly found among