Thiamin and Pyrimidine Studies on Older Subjects.

Abstract

Most of the studies on human vitamin requirements have been conducted on young adults or children. Very little is known regarding the vitamiii requirements with advancing age. The favorable reports of the clinical application of vitamins, particularly thiamin, in geriatrics raise the question as to why such deficiencies exist. IS it reduced intake, inability to utilize, or an increased need? As a first step toward understanding this problem, a study of daily urinary excretion of thiamin in reasonably healthy older subjects was undertaken.In this study, 4 men and 4 women were used as experimental subjects. In order to determine the state of health of the individuals, a physician$ examined each one before and after the experimental period. All members of the group were ambulatory and in the seventh or eighth decade of life.It was impossible to control the type or amount of food eaten by the subjects, but complete dietary records were kept during the period of the experiment. The thiamin content of the daily diets was calculated, using the tables of Munselll and Booher.2The experimental period o f approximately 3 weeks was divided into 3 parts : A preliminary period on the usual diet, a second period during which the diet was supplemented with 2 mg of thiamin daily, and a final period during which the supplement was 4 mg of thiamin daily. The thiamin was given orally in the form of one milligram tablets at mealtime. Complete 24-hour urine samples were collected daily and analyzed for their thiamin and pyrimidine content by the fermentation method of Schultz, Atkin, and F r e~.~ Experimental Results and Discussion. The data concerning the experiment are summarized in Tables I and 11.

Studies of Thiamine Metabolism in Man. I. Thiamine Balance. The Normal Requirement of Vitamin B1 and the Rôle of Fecal Thiamine in Human Nutrition 1

“…daily, it is probable that the PAYF arising from thiamine will continue to decrease as the intake of the vitamin is progressively curtailed, since the available data (16,17) indicate that the urinary PAYF is lowest in those subjects whose dietary thiamine is small. Under such circumstances the urinary PAYF may arise from food PAYF rather than from thiamine cleavage in the body, for it has been shown (15) that a related compound, 2-methyl-6-amino-5-ethoxymethyl pyrimidine, when fed to rats, is rapidly and quantitatively excreted in the urine.…”

“…Supplementing the intake of thiamine by oral (17) or parenteral (16,23) administration results in substantial increases in both urinary PAYF and thiamine; the pyrimidine which arises from thiamine is proportional to the thiamine intake within certain limits (1.3 to 20 mgni.) (23).…”

Thiamine-Pyramin Assay, Factors Influencing Yeast Fermentation Methods for Thiamine and Pyramin

“…natural and synthetic substances which yield this residual or sulfite blank activity. Of the synthetic pyrimidines that are able to increase the rate of yeast fermentation, 2-methyl-4-amino-5ethoxymethylpvrimidine, an intermediate in the commercial synthesis of thiamine, is readily available in pure crystalline form and has been most widely used (3, 4, 6-8, 12,14,15). Several other synthetic pyrimidines have been reported to have approximately the same activity (8).…”

Studies of Thiamine Metabolism in Man. Ii. Thiamine and Pyrimidine Excretion With Special Reference to the Relationship Between Injected and Excreted Thiamine in Normal and Abnormal Subjects 1

“…Furthermore, administration of B, supplements over a prolonged period should saturate the tissues. Yet even under such conditions (14,15) urinary thiamine accounts for only a fraction of the total. B, administered.…”

“…The urinary concentration of this substance, as well as of thiamine, increases after the oral or parenteral administration of thiamine supplements (14,15,17). Little is known regarding the factors which influence the conversion of the I This investigation was aided by a grant from the Josiah Macy, Jr. Foundation. vitamin to this substance, and the excretion of the latter in relation to thiamine intake also requires elucidation.…”