The bioavailability of vitamin B₆ in four selected foods (bananas, filberts, soybeans and beef) was determined in five men, aged 22 to 25 years, who were saturated with pyridoxine. The study consisted of a five-day adjustment period followed by a 28-day experimental period. All subjects consumed a constant diet containing 1.34 mg of vitamin B₆ from Monday to Friday of each week, and their self-chosen diets on the weekends. During the experimental period the subjects received 5 mg of pyridoxine each day, including weekends, except on the days when loading doses of crystalline pyridoxine and the selected foods were administered. Doses of 2 mg of crystalline pyridoxine or doses of food containing approximately 2 mg of vitamin B₆ were given. The subjects collected daily 24-hr urine specimens. Vitamin B₆ bioavailability was determined by comparing the yield of 4-pyridoxic acid in response to the test food doses to the yield of 4-pyridoxic acid in response to the 2mg of crystalline pyridoxine. Compared to the 100 percent bioavailability of 2mg crystalline pyridoxine, the mean percent bioavailability of vitamin 65 from banana was 131.4 ± 68.2; from filberts, 88.1 ± 13.9; from soybeans, 58.3 ± 24.3; and from beef, 81.5 ± 28.6. Factors affecting bioavailability of vitamin B₆ from these foods are discussed. / Graduation date: 1983

The influence of riboflavin doses on the urinary excretion of riboflavin and 4-pyridoxic acid was investigated in 6 young men. Doses of crystalline riboflavin and/or pyridoxine were administered on days 10 to 25 using a 6 X 6 Latin square design. The 6 crystalline vitamin doses given were: 0.3 mg and 0.6 mg pyridoxine; 1.2 mg and 2.4 mg riboflavin: 0.3 mg pyridoxine with 1.2 mg riboflavin and 0.6 mg pyridoxine with 2.4 mg riboflavin. On day 28 each subject received 0.06 mg riboflavin. On days 30 to 45, 6 food doses of known riboflavin content were administered to the subjects using a 6 X 6 Latin square design. All crystalline vitamin and food doses were separated by two days. All subjects consumed a constant diet during the experimental period. Twenty-four-hour urine collections were made throughout the study. Urinary riboflavin excretion increased in response to the 1.2 mg and 2.4 mg riboflavin doses but not after the 0.06 mg dose. Urinary riboflavin excretion increased after the milk dose only. Bioavailability of riboflavin in non-fat dry milk, which was estimated by reference to the riboflavin dose response curve, was 61 ± 35 (mean ± S.D.) percent. In 4 of the 6 subjects urinary 4-pyridoxic acid excretion was suppressed when riboflavin was administered with pyridoxine. Additionally, in four subjects the 2.4 mg riboflavin dose depressed urinary 4-pyridoxic acid excretion to a level below that seen with the 1.2 mg riboflavin dose. These results provide additional supporting evidence for a riboflavin/vitamin B-6 interaction. / Graduation date: 1985

The study reported in this thesis is part of an investigation designed to determine the metabolism of thiamine and riboflavin in human subjects who were maintained on controlled diets. Part of this investigation was made during a 30-day experimental period in 1950 and the other part, during a 30-day experimental period in 1951. In the studies of both years, the subjects were maintained on a diet which was adequate in all nutrients except thiamine and riboflavin. With respect to thiamine, each of the 30-day studies was divided into two experimental periods of 15 days each. During the first 15-day period, the National Research Council's recommended allowance of 500 mcg. thiamine per 1000 calories per person per day was tested and in the second period, each subject received 300 mcg. thiamine per 1000 calories daily in the diet. The daily intake (about 1.2 mg.) of riboflavin was constant throughout the whole study. This thesis is a report of the riboflavin phase of the study only. Four women were selected as subjects for each year's 30-day experiment. In general, they were healthy throughout the entire period of the study. Daily micro determinations of the concentration of free (+FMN) and total riboflavin in the serum and daily macro determinations of riboflavin excreted in 24-hour collections of urine were made. Based on the results of the studies of both years, the mean concentration of free (+FMN) serum riboflavin for seven subjects (data for one subject were omitted) was 1.43 and ranged between 0.47 to 3.5 mcg. percent regardless of the different levels of thiamine intake; the mean concentration of total serum riboflavin was 3.22 and ranged from 2.36 to 5.30 mcg. percent. The mean concentration of free (+FMN) riboflavin in the serum was slightly, but not significantly lower on the period of restricted thiamine intake. The mean concentration of total riboflavin increased 0.43 mcg. percent in the period of restricted thiamine intake; this increase was statistically significant. This phenomenon may have been due to the effect of thiamine on the utilization of riboflavin in metabolism; i.e., a decrease in thiamine intake reduces the requirement for riboflavin and is reflected in an increased concentration of riboflavin in the serum. The statistical analysis indicated that the variation among individuals in serum riboflavin concentration is statistically significant. There was no significant day-to-day variation in the riboflavin value in serum during the period of study. The mean daily urinary excretion of riboflavin of three subjects (data for one subject were omitted) in the 1950 study was 382 mcg. per day, and that of four subjects in the 1951 study, 376 mcg. per day. The riboflavin output was about 32 percent of the ingested vitamin in both years' studies. The riboflavin excretion per gram of creatinine ranged from 248 to 474 mcg. / Graduation date: 1951

Plasma vitamin B₁₂ concentrations of 16 elderly women were measured using the growth response of the microorganism, Ochromonas malhamensis. The method required major modifications which are described in detail. All women had plasma concentrations of vitamin B₁₂ above the normal minimum of 200 pg/ml despite the fact that the diets of nine women failed to meet the RDA of 3 μg/day. The mean dietary B₁₂ of 11 women who took no supplemental B₁₂ was 2.90 μg/day; their mean plasma concentration was 415 pg/ml. The group of five women who took B₁₂ preparations had an average total intake of 13.89 μg/day and a significantly higher plasma concentration (628 pg/ml). Supplemental intakes of ascorbic acid in the range of 200-1100 mg/day had no destructive effect on vitamin B₁₂ in plasma. / Graduation date: 1976

The purposes of the research presented in this thesis were: (1) to determine the precision with which it is possible to measure changes in vitamin B6 compounds in the blood and urine following oral doses of levels of vitamin B6 (as pyridoxine) which are in the range of the normal daily intake of this vitamin; (2) to compare the effect of three free forms of vitamin B6 (PL, PM, PN) at these same levels using the same assays; and (3) to compare the response of guinea pigs to that of humans when the animals are given three free forms of vitamin B6 at physiological levels. The effect of small incremental doses of pyridoxine (PN) (0.5 - 10 mg) and of equimolar doses of PN, pyridoxamine (PM) and pyridoxal (PL) were studied in five healthy young men. On the day before and during the day of the dose, the subjects were on a controlled diet that supplied 1.6 mg of vitamin B6 each day. During other days of the week, the subjects were on self-selected diets. Timed blood and urine samples were obtained on the day each dose was administered. The parameters measured were: plasma vitamin B6 (PB6), plasma pyridoxal phosphate (PLP), urinary vitamin B6 (UB6) and urinary 4-pyridoxic acid (4PA). Variables reflecting the response to each dose for each of these parameters were calculated in two ways; (1) the percent increase of the maximal post-response value over the pre-response value; and (2) the area under the curve bounded by the values obtained and the times of the samples. For all eight of the variables so calculated, the relationship to the PN doses given were linear in the 0.5 to 10 mg range. Maximal levels of plasma PLP and PB6 were reached at 1/2 hr after the dose for the 0.5, 1, 2, and 4 mg levels of PN. At the 10 mg level, plasma B6 peaked at 1/2 hr for 3 subjects and at 1 hr for 2 subjects. Plasma PLP peaked at 1 hr following the 10 mg PN dose. PB6 was much more responsive to the loading doses than was PLP. The PB6:PLP ratio was maximal at 1/2 hr following the doses. Maximal values of urinary 4PA and UB6 were found in the first 3 hr after the dose. The ratio 4PA:UB6 decreased with increasing PN dose levels and varied for each collection period following the dose. The same variables were calculated for the study of a comparison of 19.44 μmole doses of PN, PM and PL. The PB6 peaks occurred at 1/2 hr for PL and PN, and at 1 hr for PM. The PLP peaks occurred at the following times: PN, 1/2 hr; PM, 3 hr; and PL, 1 hr. Maximal levels of UB6 and 4PA were reached in the first three hr after the dose for all three forms. The percent increase and area variables were able to distinguish between nearly all the responses to the three forms of vitamin B6 administered at the 19.44 μmole level. The PB6 response was largest following the PL dose, but the PLP levels were lower after PL than after either PM or PN. The 4PA values were highest following the PL dose, indicating that the PL dose was metabolized to 4PA rather than converted to plasma PLP. Some of the nutrient contents of the self-selected diets were found to be significantly correlated with some response variables. There was no relationship found between either body weight and 4PA excretion on the day before the dose, or between ascorbic acid intake on the self-selected diets and 4PA excretion on the day before the dose. Strenuous exercise was found to significantly affect plasma PLP levels in subjects who had received the loading doses of PN. In another study, three groups of guinea pigs were each given their Recommended Dietary Allowance of vitamin B6 as PM, PL or PN. The same parameters were measured as for the humans. There were no significant differences between the groups of animals in body weight, organ weights (spleen, liver, kidney, brain), plasma B6 or PLP, or in formed elements of the blood (hemoglobin, hematocrit, white blood cells, red blood cells). Urinary 4PA and UB6 were significantly higher in animals receiving PN. / Graduation date: 1978

Bioavailability (BA) of vitamin B6 (B-6) from foods may be limited. The knowledge of the BA of B6 from food is important in that this would help to understand if the B6 present in the diet of individuals will meet the requirements for this vitamin. The purpose of this study was a) to develop a method to measure the level of glycosylated vitamin B6 (GB6) in the foods; b) to investigate the relative vitamin B6 bioavailability from tuna (T), whole wheat bread (WW), and peanut butter (PB) in humans; c) to follow the excretion pattern of GB6 and relate this to the occurrence of the GB6 in foods. To measure the level of GB6 in foods, the B6 content was determined microbiologically before and after treatment of the foods with β-glycosidase as well as after acid hydrolysis. Animal products contained no measurable amount of GB6, but grain and legumes had 6-75% of total B6 present as GB6. Of the fruits and vegetables analyzed, orange juice (47%) and raw carrots (51%) had the highest GB6 levels. Relative BA of B6 from T, WW, and PB was investigated in eight healthy men in a 52-day study (10-day adjustment and three 14-day experimental periods). B5 intake was set at 1.6 mg/day, with 50% coming from one experimental food and 50% from a basal diet. Urine was analyzed for 4-pyridoxic acid (4PA) and B6; feces for B6; and plasma for pyridoxal-5'-phosphate (PLP). Of these four indices used to assess B6 bioavailability, 4PA and urinary B6 were significantly (p < 0.01) higher in T than in either WW or PB periods. When T was fed, fecal B6 excretion was significantly (p < 0.01) lower than when PB was fed. The B6 in WW and PB was 75% and 63% as available as that from T, respectively. The urine from the last day of each period for five subjects and the last fecal composite for each period was analyzed for the nonconjugated B6 and GB6. The majority of B6 in the feces was in the non-conjugated form. No GB6 was detected in the feces during either the T or PB periods. Only 4% of total B6 in the feces was in the GB6 form when WW was fed. GB6 was found in the urine in all periods. The level of GB6 in the food was inversely related to B6 bioavailability in foods fed to humans in our study and in three other human studies. It appears that the level of GB6 in foods could be used as an index of B6 bioavailability in foods. / Graduation date: 1984

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A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Medicine in the branch of Internal Medicine Johannesburg, 2014 / Background: Hypovitaminosis D is endemic worldwide. With the discovery of extra skeletal receptors for 1,25-dihydroxyvitamin D, the influence of vitamin D (25(OH)D3) deficiency has been investigated in metabolic diseases. In South Africa, little is known about 25(OH)D3 status. Aim: To investigate the 25(OH)D3 status in patients in Johannesburg, and to assess for any correlation between 25(OH)D3 , metabolic diseases and patient demographics and seasonal variation. Methods: A retrospective study of 1000 patients attending a northern suburb practice in Johannesburg was performed. Serum 25(OH)D3 levels, demographics and metabolic data were collected. Results: The mean 25(OH)D3 level was 24.45ng/ml and 74.3% were vitamin D deficient. There was no difference in mean 25(OH)D3 levels between age or gender groups. The lowest mean 25(OH)D3 was in the Indian race (p=0.001), HOMA-IR >2 (p=0.001), fasting glucose >7 (p=0.016) and highest was measured during the summer (p=0.001). There was a significant correlation between 25(OH)D3 level and cholesterol (p=0.001), however no correlation was found with hypertension or diabetes. Conclusion: This study reports a high incidence of hypovitaminosis D especially among Indians. In this study there was no correlation between hypovitaminosis D and metabolic factors except for a negative correlation with the cholesterol level.

A dissertation submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg for the Degree of Masters of Science. December 1992. / Rouesettus aegyptiacus, the fruit bat is a crepuscular frugivore with no obvious access to either exogenous or endogenous sources of vitamin D. Therefore this animal's vitamin D status and endocrine system was investigated. Both captive and wild populations of fruit bats appear to be naturally in a vitamin D impoverished state. The serum concentration of the principle circulatory, metabolite [25(OH)D] is undetectable (< 4 ng/ml), Fruit bats possess the full compliment of enzymes associated with the vitamin D endocrine system. This was shown when labelled more polar metabolites were produced after the administration of 3H vitamin D3 and 3H 2S(OH)D3' Furthermore, a specific vitamin D binding protein (DBP) is present. After partial purification, it was revealed that this molecule is slightly larger in molecular mass than that of humans and baboons. The intraperitoneal administration of 25(OH)D3 revealed enhanced 1a-hydroxylase activity such that 1.7 times more 1,25(OH)2Ds was produced than 24,25(OH)2D3' The ratio of these di-hydroxylated metabolites conform with the ratio of these 2 metabolites in states of vitamin D deficiency and thus confirm the impoverished vitamin D status. Undetectable serum concentrations of 25(OH)D3 might therefore be explained by a limited exogenous vitamin D substrate (rotting fruit peels and fungi). Given the elevated 1a hydroxylase activity 1 the small amount'S of 25(OH)D produced would be rapidly converted to the active metabolite. The low concentration of active hormone appear adequate for the maintenance of mineral homeostasis as indicated by tightly controlled serum calcium (2.26 ± 0.17 mrnol/l), magnesium 01.16 + 0.24 mmol/l) and inorganic phosphorus (2.93 ± 1.01 mmol/I). Both vitamin D2 and vitamin D3 metabolites were detected in bat serum albeit in very small amounts, suggesting that fruit bats exploit both exogenous plant sources (skins of fruit - vitamin 1)2; fungi - vitamin D:3)and might indeed receive some U. V. light during their crepuscular forays to endogenously produce small amounts of vitamin D3 In conclusion, fruit bats appear to belong to a small group of animals that naturally have limited access to Vitamin D, yet the vitamin D endocrine system in these animals is no different to that of other mammals. These animals have adapted their vitamin D endocrine system to function well at the low hormone concentrations and they exhibit no pathological problems associated with relative vitamin D depletion. / AC2017