VITAMIN REQUIREMENT STUDY TECHNIQUES

Vitamin requirement studies have been conducted for 50 years using gro wth and clinical signs of deficiency for quantitative studies. Histolo gical confirmation of apparent signs confirm and establish subclinical measurements for deficiency. Test. diets for these studies with posit ive experimental control over the test vitamin have been developed usi ng varying degrees of vitamin-free ingredients in the formulations. Ha ematology values and microanatomical changes reflect failures of a met abolic system and provide convincing data for requirements. Quantitati ve studies have used specific test diets plus increasing aliquots of t he test vitamin, coupled with growth response, tissue storage analysis , and :enzyme system activity. Results have been reported for levels w hich support normal growth, enzyme saturation, and maximum liver or ot her tissue stprage levels. Megavitamin intake studies have been correl ated with improved resistance to stress and certain fish diseases. Sta tistical measurement of response to various parameters used become ess ential for quantitative vitamin requirement determinations. Early stud ies using vitamin analysis of feedstuffs mixtures coupled with growth response, absence of deficiency signs, and liver or tissue storage hav e been superseded by diets with more positive control of all nutrients , including the vitamin to be tested. Sparing effects of one vitamin u pon another can be demonstrated. Various vitamer forms may have differ ent activity to supply physiological requirements for the vitamin. Mos t water-soluble vitamins act as co-enzymes in metabolic systems. Some fat-soluble vitamins have molecular functions acting as hormones, free radical traps, intracellular reducing agents, pigments, antioxidants, etc. A guide for vitamin requirements or dietary allowances should be followed when research plans are made to conduct vitamin requirement studies.