James E. Leklem

Nutrient intake and hormonal status of premenopausal vegetarian seventh‐day adventists and premenopausal nonvegetarians

The relationship between dietary nutrients and plasma estrone, estradiol-17 beta, estriol, dehydroepiandrosterone sulfate, and prolactin levels was investigated in 14 premenopausal Seventh-day Adventist vegetarian (SV) women and 9 premenopausal non-Seventh-day Adventist nonvegetarian (NV) women. The SV subjects consumed less fat, especially saturated fat, and used significantly less fried food than the NV subjects. Plasma levels of estrone and estradiol-17 beta in the SV subjects were significantly lower than in the NV subjects. SV estradiol-17 beta and estriol levels were positively correlated with linoleic acid and protein intake, while NV prolactin levels were significantly correlated with intakes of oleic and linoleic acids and total fat. The data suggest that specific dietary nutrients were related to the hormonal milieu of these SV and NV subjects.

Urinary 4-Pyridoxic Acid, Urinary Vitamin B-6 and Plasma Pyridoxal Phosphate as Measures of Vitamin B-6 Status and Dietary Intake in Adults

As reviewed by Sauberlich (1), a number of studies have been conducted to determine the efficacy of measuring urinary 4-pyridoxic acid and vitamin B-6 excretion levels, as well as plasma pyridoxal phosphate levels, as criteria for assessing vitamin B-6 nutritional status. It has been suggested that urinary vitamin B-6 excretion levels may be reflective only of recent dietary vitamin B-6 intake and may not be indicative of the severity of the deficiency (1).

The effects of a high-carbohydrate low-fat cholesterol-restricted diet on plasma lipid, lipoprotein, and apoprotein concentrations in insulin-dependent (type I) diabetes mellitus☆

Six women with well-defined insulin-dependent diabetes mellitus (IDDM) were studied for 4 weeks during a control diet containing 45% of the calories as carbohydrate, 40% fat (P/S ratio 0.14), 15% protein, and 580 mg of cholesterol, and for 6 weeks during a high-carbohydrate low-fat cholesterol-restricted diet with 65% carbohydrate, 20% fat (P/S ratio 1.40), 15% protein, and 62 mg cholesterol. All subjects completed both dietary periods in a crossover experimental design. Individual menus were subject-selected from a calculated exchange list containing conventional food items consistent with current American dietary patterns. The diets were well-tolerated by all subjects. Total plasma cholesterol decreased from 201 to 156 mg/100 mL (P less than 0.05) during the cholesterol-restricted diet, while total plasma triglyceride (TG) increased from 96 to 115 mg/100 mL (P less than 0.01). During this same period, very low-density lipoprotein cholesterol (VLDL-C) and VLDL-TG increased from 17 to 21 mg/100 mL (P less than 0.05) and from 59 to 76 mg/100 mL (P less than 0.001), respectively, while low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) decreased from 126 to 90 mg/100 mL (P less than 0.05) and from 50 to 39 mg/100 mL (P less than 0.05), respectively. LDL-C/HDL-C and total-C/HDL-C ratios were lower but not significantly different, and LDL-TG and HDL-TG were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Recommendations for Status Assessment of Vitamin B-6

Since the discovery of vitamin B-6 and the subsequent elucidation of the various roles that vitamin B-6 plays in the body, numerous methods for assessing vitamin B-6 status have been developed. The previous paper points out the available methods and future developments in methodology. A number of direct and indirect methods have been utilized. Just as there are a variety of methods available for determining a specific vitamin B-6 metabolite, so there are an equal variety of approaches to assessing vitamin B-6 status. Both the discussions following each of the papers presented at this Workshop and the follow-up indepth discussion of the papers dealing with status assessment pointed out the importance of recognizing that there is not one “best” method for status assessment./Also, as stressed in the discussion session of the Workshop, it is one thing to develop good methodology; its another matter to put them into real practical use. The utilization of the methods for status assessment can be applied to studies of healthy individuals, evaluation of individuals with specific pathological conditions, and population studies. However, the choice of the method to be used must take into account the particular situation being studied. The use of urinary vitamin B-6 metabolite excretion in a large population study may be more advantageous than collection of blood samples.

Increased plasma pyridoxal-5'-phosphate when alkaline phosphatase activity is reduced in moderately zinc-deficient rats

It is generally believed that the zinc metalloenzyme alkaline phosphatase is required to hydrolyze phosphorylated forms of vitamin B-6 prior to their use. To test this hypothesis, rats were fed a liquid diet containing either adequate or moderately low zinc during gestation and lactation. Zinc deficiency was produced in dams evidenced by significant reductions in zinc concentration of plasma (49%), liver (25%), and femur (24%), and plasma alkaline phosphatase activity (48%). Plasma pyridoxal-5′-phosphate (PLP), which significantly increased (61%) in these same rats, was negatively correlated (r=−0.74,P<0.02) with plasma alkaline phosphatase activity. Maternal liver PLP concentration was unaffected by zinc status. The zinc and vitamin B-6 relationship seen in dams was less observable in offspring. Stimulation of erythrocyte alanine aminotransferase activity by exogenously added PLP in vitro tended to be higher in both moderately zinc-deficient mothers and their offspring, but the difference was not significant. Our results support the hypothesis that alkaline phosphatase activity is required for the hydrolysis of plasma PLP. Our results also suggest that zinc status as alkaline phosphatase activity should be defined in an individual if plasma PLP is to be used as an indicator of vitamin B-6 status.

Vitamin B-6 status of children undergoing continous ambulatory peritoneal dialysis

Abstract The purpose of this study was to evaluate the vitamin B-6 status of children undergoing continuous ambulatory peritoneal dialysis (CAPD) and to determine the renal and peritoneal clearance of vitamin B-6 in these children. Eight children, mean age 12 years, were included in the first study. Urine, dialysate and plasma were analyzed for total vitamin B-6 and pyridoxal 5′-phosphate (PLP). Dialysate total protein and serum alkaline phosphatase were also measured and a three day dietary record was obtained. Plasma PLP was measured in six subjects one year following the first study after they had been receiving daily pyridoxine supplements for one year. Mean plasma total vitamin B-6 and PLP were 304 and 25.5 nM, respectively, in the first study. The mean ratio of plasma PLP/total vitamin B-6 was 0.146. Mean plasma PLP in supplemented subjects was 60.4nM. Renal and dialysate clearance of vitamin B-6 was 0.41 and 0.90 mls/min, respectively. Mean dietary intake of vitamin B-6 was 59% of the RDA. CAPD treated children appear to be deficient in vitamin B-6 although dialysate losses are minimal. Pyridoxine supplements of at least 2mg/day are necessary to increase plasma PLP to normal concentrations in these children.

Effect of vitamin B-6 supplementation on fuels, catecholamines, and amino acids during exercise in men.

PURPOSE In two separate but identical studies, the effect of vitamin B-6 supplementation was examined on plasma energy substrates, catecholamines, and 13 amino acid concentrations during exercise. METHODS Eleven trained men performed two separate exhaustive exercise tests at 71.0+/-4.6% VO2max during two separate 9-d controlled diet periods. Exercise test 1 (T1C) occurred following a control diet, and test 2 (T2B6) occurred following a vitamin B-6 supplemented diet (20 mg PN.d(-1)). Blood was drawn pre, during (60 min), post, and post-60 min of exercise, and plasma was analyzed for glucose, lactate, glycerol, free fatty acids (FFA), catecholamines (N = 5), and amino acids (N = 5). RESULTS Mean FFA concentrations changed over time in both tests (P < 0.001) and were lower in T2B6 compared to T1C at pre (P = 0.03), during (P = 0.05), and post-60 min (P = 0.04) of exercise. Mean lactate, glycerol, and catecholamine concentrations only changed over time (P < 0.0001). The only significant changes in amino acid concentrations were for lower tyrosine (P = 0.007) and methionine (P = 0.03) concentrations in T2B6 relative to TIC at post-60 min of exercise and postexercise, respectively. No differences were observed in exercise times to exhaustion between TIC (108+32.6 min) and T2B6 (109+51.2 min). CONCLUSIONS These results indicate that vitamin B-6 supplementation can alter plasma FFA and amino acid concentrations during exhaustive endurance exercise without affecting endurance.

Effect of carbohydrate and vitamin B-6 on QTc intervals in women during exercise

Abstract Vitamin B-6 (B6), as pyridoxal 5′phosphate, is essential for glycogenolysis and gluconeogenesis. Changes in B6 status may alter fuels available for the heart and muscles during exercise (EX). We investigated whether dietary carbohydrate (CHO) and B6 could alter QT intervals in 5 young/trained, 5 young/untrained and 5 postmenopausal/untrained women fed a moderate CHO diet for 2 wk, a high CHO diet for 1 wk, a moderate CHO+B6 diet for 2 wk and a high CHO+B6 diet for 1 wk. EX testing included 20 min on a cycle ergometer at 80% V02max at the end of each dietary treatment. ECG tracings were monitored and QT corrected (QTc) was measured at rest and 80% maximal heart rate (MHR). There were significantly longer QTc intervals when the moderate CHO diet was fed as compared to when the other diets were fed. For all diets, QTc increased from rest to 80% MHR in all but the young/untrained group. The magnitude of change in QTc intervals from rest to 80% MHR was significantly different between the groups. QTc intervals measured occurred while subjects were in adequate B6 metabolism as indicated by plasma pyridoxal 5′-phosphate concentrations within normal range. This research supports the finding that diet (B6 and/or CHO) can alter QT intervals in women during exercise.

Food Intake Measurement: University Dining Halls As An Extension Of The Laboratory

Measurement of dietary intake is complicated by various factors which make accuracy measurement difficult when the usual dietary intake is maintained. A method used recently by the authors to measure food intakes of subjects in a university residence hall dining room is described. The time costs of this method are shown to be similar to those of metabolic laboratory studies. The advantages of using the dining hall method are reduced financial costs and minimal disrup tion of subjects food habits. The need for an accurate but valid measure of food intake as a dependent variable in an experimental situation was met by the dining hall method.