Urinary riboflavin excretion after a load test in rural China as a measure of possible riboflavin deficiency.

Urinary excretion of riboflavin was measured in 3318 adults 4 h after an oral dose of riboflavin. Male and female subjects aged 35-64 years were selected from 65 mostly rural counties located in 24 provinces of China. Counties were selected to represent a range of seven of the most prevalent cancer mortality rates in China and within counties households were selected at random. Urinary riboflavin excretion levels after a load test, erythrocyte glutathione reductase activity coefficients (EGR-AC), dietary riboflavin intakes, and a large number of other biochemical, dietary, and environmental parameters were measured. Mean dietary intake of riboflavin was 75 per cent of the Chinese recommended dietary allowances (CRDA). Mean meat intake per reference man was very low (26.4 +/- 23.7 g/d) in comparison to Western standards and milk was not consumed at all in most counties. Mean EGR activity coefficients measured on 'blood pools' for both males (1.47 +/- 0.14) and females (1.48 +/- 0.16) indicated that more than two-thirds of the population surveyed was in the medium or high risk category of riboflavin deficiency. Using current reference standards of less than 1.4 mg for 4-h urinary excretion of riboflavin after a 5 mg load, more than 70 per cent of the individuals examined exhibited low levels usually associated with high risk of riboflavin deficiency. In view of the lack of specificity for clinical indications of riboflavin deficiency and the tentative validity of the present CRDA, the interpretation of the data is problematic. We suggest that the present CRDA for this vitamin is set too high and requires critical review and possibly some revision.

Effect of energy restriction on riboflavin retention in normal and deficient tissues of the rat.

We investigated the effects of energy restriction on tissue riboflavin depletion and subsequent repletion of deficient tissues. Groups of male Sprague Dawley rats with average body weights between 268 and 275g were placed on energy-restricted diets consisting of 8g (31kcal or 130kJ) per day of a basal diet adequate in all other nutrients and either 12mg of riboflavin/kg or no added riboflavin. The ad libitum controls received additional energy as a mixture of sucrose, starch, and corn oil (10:3:1 by wt). No significant difference in the degree of riboflavin deficiency was detected between energy-restricted and ad libitum-fed rats as assessed by riboflavin concentrations in the liver and gastrocnemius and soleus muscles and by the erythrocyte glutathione reductase activity coefficient (EGRAC). Additional energy-restricted riboflavin-deficient rats were subsequently repleted by feeding either the supplemented basal diet with no additional energy or with ad libitum energy. Repletion of liver riboflavin concentration and reduction of the EGRAC values to control levels occurred regardless of energy intake. Muscle riboflavin concentrations were normal in the ad libitum-fed group but decreased in the energy-restricted rats despite 4 weeks of supplementation. The latter group had muscle riboflavin levels similar to those in the rats fed the riboflavin-deficient diet for 8 weeks. The results suggest that energy restriction impairs flavo-protein synthesis in muscle but not in the liver.

[Assessment of vitamin B2, B6, and PP supply from data on excretion of vitamins and their metabolites in alimentary iron and riboflavin deficiency]. / K otsenke obespecehnnosti organizma vitaminami B2, B6, i PP po dannym ékskretsii vitaminov i ikh metabolitov pri alimentarnom defitsite zheleza i riboflavina.

Alimentary deficiency in riboflavin and/or iron in rats involved distinct decrease in excretion of 4-pyridoxylic acid and 1-N-methyl nicotinamide--the metabolites considered as the indices of vitamins B6 and PP consumption. The effect observed appears to occur due to a decrease in activity of some iron- and flavin-containing enzymes participating in the metabolism of pyridoxine and niacin. Addition to the diet of the deficient component normalized these patterns. Use of the data on excretion of 4-pyridoxylic acid and 1-N-methyl nicotinamide as criteria of consumption of pyridoxine and niacin is discussed.

[Methylmalonic acid excretion in experimental B2-avitaminosis in rats]. / Ekskretsiia metilmalonovoi kisloty pri éksperimental'nom B2-avitaminoze u krys

Providing of rats with a diet, deficient in vitamin B2 within 2 and 5 weeks, was not shown to be accompanied by an increase in excretion of methylmalonic acid. In the animals some tendency to the increased excretion of methylmalonic acid was observed within 8 weeks of the diet. The data obtained suggest that the test for excretion of methylmalonic acid was the highly specific as a pattern of supply with vitamin B12. The possible role of vitamin B2 and flavoproteins in biosynthesis of coenzyme forms of vitamin B12 is discussed.

[Effect of l-carnitine on the expression of glycine conjugates in rats in experimental B2-hypovitaminosis]. / Vliianie l-karnitina na ékspretsiiu glitsinovykh kon"ugatov u krys pri éksperimental'nom B2-gipovitaminoze.

The dynamic of glycine conjugates excretion in riboflavin deficient (RFD) rats was studied. The excretion of isovaleryl-, n-butyryl-, isobutyryl-,2-Me-butyryl- and hexanoylglycines by the RFD rats considerably increased from 1 week of the experiment and reached a plateau after 5 week. Under L-carnitine supplementation the acylglycines (isobutyryl- and isovaleryl) as well as some organic acids excretion was diminished.

[The vitamins and minerals provision of children living in different ecological-biogeochemical zones in Chuvashia]. / Obespechennost' vitaminami i mineral'nymi veshchestvami detei, prozhivaiushchikh v razlichnykh ékologo-biogeokhimicheskikh zonakh Chuvashskoi respubliki.

The results of investigation about providing 96 children at the age of 11-12 with vitamins in different ecological-biogeochemical zones of Chuvashia are presented in this article. The actual nutrition of children was estimated, by questionnaire-weight Pokrovsky's method and the level of excretion of vitamins B1, B2 and ascorbic acid with urine was studied by fluorescent method. The deficiency of riboflavin (66% in girls and 97% in boys) and ascorbic acid deficiency (30% in children) was revealed in the daily ration, the quantity of thiamin was sufficient. The providing the organism of children with investigated vitamins is low in Chuvashia. There is the link between ecological-biogeochemical characteristics of Chuvashia and providing with vitamins B1, B2 and C, their quantity in food being the same.

Evaluation of riboflavin intakes and status of 20-64-year-old adults in South Korea.

A recent Korea National Health and Nutrition Survey indicated inadequate riboflavin intake in Koreans, but there is limited research regarding riboflavin status in South Korea. The purpose of this study was to determine riboflavin intake and status of Korean adults. Three consecutive 24-h food recalls were collected from 412 (145 men and 267 women) healthy adults, aged 20-64 years, living in South Korea and urine samples were collected from 149 subjects of all subjects. The dietary and total (dietary plus supplemental) riboflavin intake was 1.33 ± 0.34 and 2.87 ± 6.29 mg/day, respectively. Approximately 28% of the subjects consumed total riboflavin less than the Estimated Average Requirement. Urinary riboflavin excretion was 205.1 ± 190.1 µg/g creatinine. Total riboflavin intake was significantly positively correlated to the urinary riboflavin excretion. (r = 0.17171, p = 0.0363). About 11% of the Korean adults had urinary riboflavin <27 µg/g creatinine indicating a riboflavin deficiency and 21% had low status of riboflavin (27 µg/g creatinine ≤ urinary riboflavin < 80 µg/g creatinine). Thus, one-third of Korean adults in this study had inadequate riboflavin status. In some adults in Korea, consumption of riboflavin-rich food sources should be encouraged.

Thiamin, riboflavin and vitamin B6: impact of restricted intake on physical performance in man.

OBJECTIVE: A combined marginally deficient status of thiamin, riboflavin, vitamin B6 and vitamin C may affect physical performance, but the relative contribution of each vitamin can only be speculated. In a previous study we did not find any effect of restricted intake of vitamin C individually. Therefore, the functional effect of restriction of thiamin, riboflavin or vitamin B6, individually or in conjunction, was investigated. METHODS: A double-blind, 2 x 2 x 2 complete factorial experiment on the effects of thiamin, riboflavin and vitamin B6 restriction on physical performance was executed with 24 healthy men. During 11 weeks of low vitamin intake, the subjects were given a daily diet of regular food products providing no more than 55% of the Dutch Recommended Dietary Allowances (RDA) for thiamin, riboflavin and vitamin B6. Other vitamins were supplemented at twice the RDA level. RESULTS: In vitamin-restricted subjects, blood vitamin levels, erythrocytic enzyme activities and urinary vitamin excretion decreased and in vitro erythrocytic enzyme stimulation increased. Short-time vitamin restriction had no harmful effects on health. A significant overall decrease was observed in aerobic power (VO2-max; 11.6%), onset of blood lactate accumulation (OBLA; 7.0%) and oxygen consumption at this power output (VO2-OBLA; 12.0%), peak power (9.3%), mean power (6.9%) and related variables (p < 0.01). However, the observed performance decrements could not be attributed to marginal deficiency for any of the vitamins studied. CONCLUSION: The absence of vitamin-specific effects on performance decrements due to thiamin, riboflavin and vitamin B6 restriction suggests quantitatively similar but non-additive effects of these B-vitamins on mitochondrial metabolism.