Carol S. Johnston

Postprandial Thermogenesis Is Increased 100% on a High-Protein, Low-Fat Diet versus a High-Carbohydrate, Low-Fat Diet in Healthy, Young Women

Objective: The recent literature suggests that high-protein, low-fat diets promote a greater degree of weight loss compared to high-carbohydrate, low-fat diets, but the mechanism of this enhanced weight loss is unclear. This study compared the acute, energy-cost of meal-induced thermogenesis on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet. Methods: Ten healthy, normal weight, non-smoking female volunteers aged 19-22 years were recruited from a campus population. Using a randomized, cross-over design, subjects consumed the high-protein and the high-carbohydrate diets for one day each, and testing was separated by a 28- or 56-day interval. Control diets were consumed for two days prior to each test day. On test day, the resting energy expenditure, the non-protein respiratory quotient and body temperature were measured following a 10-hour fast and at 2.5-hour post breakfast, lunch and dinner. Fasting blood samples were collected test day and the next morning, and complete 24-hour urine samples were collected the day of testing. Results: Postprandial thermogenesis at 2.5 hours post-meal averaged about twofold higher on the high protein diet versus the high carbohydrate diet, and differences were significant after the breakfast and the dinner meals (p < 0.05). Body temperature was slightly higher on the high protein diet (p = 0.08 after the dinner meal). Changes in the respiratory quotient post-meals did not differ by diet, and there was no difference in 24-hour glomerular filtration rates by diet. Nitrogen balance was significantly greater on the high-protein diet compared to the high-carbohydrate diet (7.6 ± 0.9 and −0.4 ± 0.5 gN/day, p < 0.05), and at 24-hour post-intervention, fasting plasma urea nitrogen concentrations were raised on the high protein diet versus the high-carbohydrate diet (13.9 ± 0.9 and 11.2 ± 1.0 mg/dL respectively, p < 0.05). Conclusions: These data indicate an added energy-cost associated with high-protein, low-fat diets and may help explain the efficacy of such diets for weight loss.

Glucose metabolism is altered in the adequately - nourished grand - offspring (F3 generation) of rats malnourished during gestation and perinatal life

To the Editor: A growing number of experimental animal studies have demonstrated the intergenerational effects of foetal/perinatal programming on birth weight, blood pressure and glucose metabolism. Potential explanations for these intergenerational effects include the following: (1) shared genetic attributes of parent and offspring; (2) adverse ‘extrinsic’ environmental conditions that persist across generations; and (3) adverse intrauterine environments that may be propagated across generations [1]. While a large number of animal studies have shown the effects of undernutrition during foetal/perinatal development on the glucose metabolism of exposed animals (F1) in adulthood [2], several studies have shown that glucose metabolism is also altered in the offspring (F2) of foetally malnourished F1 females, even when the F1 females have been well nourished since weaning [3, 4]. Here, we show, for the first time, that the glucose metabolism of the grandoffspring (F3) of female rats malnourished during development is also adversely affected. Sprague–Dawley rats consumed either a nutritionally adequate diet (20% protein; TD 91352; Harlan Teklad, Madison, WI, USA), or an isoenergetic, low-protein diet (8% protein; TD 93033; Harlan Teklad) from day 1 of pregnancy through lactation. Pups that were protein malnourished in utero consumed an adequate unrestricted diet post-weaning. The dams of control pups were adequately nourished throughout pregnancy and their offspring consumed an adequate unrestricted diet postweaning. To conserve animal resources, only one generation of control animals was bred. At ∼70 days of age, control and experimental animals were deprived of food overnight and subjected to an i.p. glucose tolerance test. Animals were killed under CO2 anaesthesia at 0, 30 and 120 min after glucose load (30% w/v; 2 g/kg body weight, i.p.). Blood was collected by cardiac puncture. Four female first-generation (F1) rats, whose mothers were proteinmalnourished both during pregnancy and while nursing, were randomly selected from the experimental group at ∼70 days of age. The selected F1 rats were mated with control breeder males and maintained on the adequate diet throughout gestation and lactation. Their offspring, the F2 generation, also consumed an adequate diet post-weaning. At ∼70 days of age, glucose tolerance tests were conducted on the F2 rats as described above. A final generation of animals (F3) was bred from control breeder males and four randomly selected F2 dams whose mothers (F1) had been protein-malnourished throughout pregnancy and lactation. F3 animals were maintained on the adequate diet and tested as described. This research was approved by the Institutional Animal Care and Use Committee (IACUC) at Arizona State University. Animals were maintained in accordance with the ‘Guide for the Care and Use of Laboratory Animals’ of the National Research Council (7th ed., 1996). As in previous reports [1, 2], the mean (±SEM) birthweight of F1 animals in our study (5.29±0.082 g) was significantly lower (p<0.05) than that of control animals D. C. Benyshek (*) Department of Anthropology, University of Nevada, Las Vegas, NV 89154-5003, USA e-mail: daniel.benyshek@unlv.edu Tel.: +1-702-8952070 Fax: +1-702-8954823

Vitamin C Deficiency and Depletion in the United States: The Third National Health and Nutrition Examination Survey, 1988 to 1994

OBJECTIVES We sought to determine prevalence rates of vitamin C deficiency and depletion in the United States. METHODS We used data from the Third National Health and Nutrition Examination Survey to assess intake of dietary, supplemental, and serum vitamin C. RESULTS Mean intakes and serum levels of vitamin C were normal; however, vitamin C deficiency and depletion were common (occurring among 5%-17% and 13%-23% of respondents, respectively). Smokers, those who did not use supplements, and non-Hispanic Black males had elevated risks of vitamin C deficiency, while Mexican Americans had lower risks. CONCLUSIONS Health professionals should recommend consumption of vegetables and fruits rich in vitamin C and should recommend supplementation for individuals at risk of vitamin C deficiency.

A reconsideration of the origins of the type 2 diabetes epidemic among native Americans and the implications for intervention policy

Type 2 diabetes has reached epidemic proportions in many Native American communities in North America. The overwhelming majority of physicians, biomedical researchers, and medical ecologists continue to explain the astoundingly high prevalence rates of diabetes among Native Americans and other high prevalence populations in terms of yet‐to‐be‐identified genetic factors. Recent experimental and epidemiological research, however, has brought to light an etiological alternative to the genetic‐predisposition model. This body of research suggests that type 2 diabetes may result initially from fetal malnutrition and, in subsequent generations, be propagated via perturbations in the intrauterine environment. Native American populations at greatest risk for diabetes today are the ones most likely to have endured severe nutritional stress in their recent histories, thus experiencing the conditions that are most conducive to the diabetic developmental sequence. If further substantiated, the implications of the fetal‐origin model of diabetes for diabetes intervention programs are profound.

Vitamin C status of an outpatient population

OBJECTIVE To determined the prevalence of vitamin C deficiency (plasma vitamin C concentrations less than 11.4 mumol/L) and vitamin C depletion (plasma vitamin C concentrations from 11.4 to less than 28.4 mumol/L) in an outpatient population. SUBJECTS AND METHODS A consecutive sample of patients presenting at a health maintenance organization laboratory for outpatient procedures was utilized. Plasma vitamin C concentrations were determined in 350 females and 144 males, aged 6 to 92 years (mean +/- SD: 46.7 +/- 18.7 years). RESULTS The mean plasma vitamin C concentration for all subjects was 32.4 +/- 13.6 mumol/L. Mean plasma vitamin C did not vary by sex, race, or fasted state. Diabetics had a significantly lower mean plasma vitamin C concentration (25.6 +/- 10.8 mumol/L) compared to patients presenting for general check-up/gynecological exams (33.5 +/- 14.8 mumol/L) or pregnancy exams (32.4 +/- 9.7 mumol/L). Six percent of subjects had plasma vitamin C concentrations indicative of vitamin C deficiency (n = 31), and 30.4% of the sample were vitamin C depleted (n = 150). The prevalence of vitamin C deficiency or vitamin C depletion did not differ by race or visit category. CONCLUSIONS Surprisingly high rates of vitamin C deficiency and vitamin C depletion were evident among generally healthy, middle class patients visiting a health care facility for routine health exams, gynecological exams, and pregnancy exams.

Pinto Bean Consumption Reduces Biomarkers for Heart Disease Risk

Objective: To determine effects of daily intake of 1/2 cup pinto beans, black-eyed peas or carrots (placebo) on risk factors for coronary heart disease (CHD) and diabetes mellitus (DM) in free-living, mildly insulin resistant adults over an 8 week period. Methods: Randomized, crossover 3×3 block design. Sixteen participants (7 men, 9 women) received each treatment for eight-weeks with two-week washouts. Fasting blood samples collected at beginning and end of periods were analyzed for total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol, triacylglycerols, high-sensitivity C-reactive protein, insulin, glucose, and hemoglobin A1c. Results: A significant treatment-by-time effect impacted serum TC (p = 0.026) and LDL (p = 0.033) after eight weeks. Paired t-tests indicated that pinto beans were responsible for this effect (p = 0.003; p = 0.008). Mean change of serum TC for pinto bean, black-eyed pea and placebo were −19 ± 5, 2.5 ± 6, and 1 ± 5 mg/dL, respectively (p = 0.011). Mean change of serum LDL-C for pinto bean, black-eyed pea and placebo were −14 ± 4, 4 ± 5, and 1 ± 4 mg/dL, in that order (p = 0.013). Pinto beans differed significantly from placebo (p = 0.021). No significant differences were seen with other blood concentrations across the 3 treatment periods. Conclusions: Pinto bean intake should be encouraged to lower serum TC and LDL-C, thereby reducing risk for CHD.

Vegetarian diets are associated with healthy mood states: a cross-sectional study in Seventh Day Adventist adults

BackgroundThe physical health status of vegetarians has been extensively reported, but there is limited research regarding the mental health status of vegetarians, particularly with regard to mood. Vegetarian diets exclude fish, the major dietary source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), critical regulators of brain cell structure and function. Omnivorous diets low in EPA and DHA are linked to impaired mood states in observational and experimental studies.MethodsWe examined associations between mood state and polyunsaturated fatty acid intake as a result of adherence to a vegetarian or omnivorous diet in a cross-sectional study of 138 healthy Seventh Day Adventist men and women residing in the Southwest. Participants completed a quantitative food frequency questionnaire, Depression Anxiety Stress Scale (DASS), and Profile of Mood States (POMS) questionnaires.ResultsVegetarians (VEG:n = 60) reported significantly less negative emotion than omnivores (OMN:n = 78) as measured by both mean total DASS and POMS scores (8.32 ± 0.88 vs 17.51 ± 1.88, p = .000 and 0.10 ± 1.99 vs 15.33 ± 3.10, p = .007, respectively). VEG reported significantly lower mean intakes of EPA (p < .001), DHA (p < .001), as well as the omega-6 fatty acid, arachidonic acid (AA; p < .001), and reported higher mean intakes of shorter-chain α-linolenic acid (p < .001) and linoleic acid (p < .001) than OMN. Mean total DASS and POMS scores were positively related to mean intakes of EPA (p < 0.05), DHA (p < 0.05), and AA (p < 0.05), and inversely related to intakes of ALA (p < 0.05), and LA (p < 0.05), indicating that participants with low intakes of EPA, DHA, and AA and high intakes of ALA and LA had better mood.ConclusionsThe vegetarian diet profile does not appear to adversely affect mood despite low intake of long-chain omega-3 fatty acids.

Stability of ascorbic acid in commercially available orange juices

OBJECTIVE To compare the vitamin C content of reconstituted frozen orange juice concentrates at preparation to that of ready-to-drink orange juices purchased 4 to 5 weeks from expiration. DESIGN Juices were unsealed and analyzed for reduced and oxidized vitamin C content at the time of purchase and reanalyzed 3 times weekly for 4 to 5 weeks. Same-lot samples of the ready-to-drink juices remained sealed after purchase and were opened for analyses at 3, 2, 1, or 0 weeks before expiration. SAMPLES/SETTING: Orange juices were reconstituted frozen concentrates, ready-to-drink juice packaged in resealable, screw-top containers, or ready-to-drink juice packaged in nonresealable containers. Juices were obtained from local retailers and stored at 4 degrees C in their original containers when appropriate. STATISTICAL ANALYSES PERFORMED The reduced vitamin C content of juices analyzed repeatedly, 3 times weekly for 4 weeks, were compared using repeated measures analysis of variance. Linear regression lines were computed for reduced vitamin C in each juice over time, and differences between slopes were analyzed by oneway analysis of variance. RESULTS The orange juices from frozen concentrates contained 86 mg reduced vitamin C per fluid cup at initial preparation and 39 to 46 mg/c after 4 weeks of storage. Ready-to-drink juices averaged significantly lower reduced vitamin C: 27 to 65 mg/c at opening and 0 to 25 mg/c at expiration 4 weeks later. Ready-to-drink orange juices had twofold to threefold higher concentrations of oxidized vitamin C vs the orange juices reconstituted from frozen, and the decomposition rate of reduced vitamin C was similar for all juices, about 2% per day once opened. APPLICATIONS Ready-to-drink orange juices should be purchased 3 to 4 weeks before expiration date and consumed within 1 week of opening.

Strategies for Healthy Weight Loss: From Vitamin C to the Glycemic Response

Abstract America is experiencing a major obesity epidemic. The ramifications of this epidemic are immense since obesity is associated with chronic metabolic abnormalities such as insulin resistance, dyslipidemia, and heart disease. Reduced physical activity and/or increased energy intakes are important factors in this epidemic. Additionally, a genetic susceptibility to obesity is associated with gene polymorphisms affecting biochemical pathways that regulate fat oxidation, energy expenditure, or energy intake. However, these pathways are also impacted by specific foods and nutrients. Vitamin C status is inversely related to body mass. Individuals with adequate vitamin C status oxidize 30% more fat during a moderate exercise bout than individuals with low vitamin C status; thus, vitamin C depleted individuals may be more resistant to fat mass loss. Food choices can impact post-meal satiety and hunger. High-protein foods promote postprandial thermogenesis and greater satiety as compared to high-carbohydrate, low-fat foods; thus, diet regimens high in protein foods may improve diet compliance and diet effectiveness. Vinegar and peanut ingestion can reduce the glycemic effect of a meal, a phenomenon that has been related to satiety and reduced food consumption. Thus, the effectiveness of regular exercise and a prudent diet for weight loss may be enhanced by attention to specific diet details.

Intakes of vitamin C, vegetables and fruits: Which schoolchildren are at risk?

OBJECTIVE The purpose of this study was to determine vitamin C intakes among American schoolchildren. We investigated the leading sources of vitamin C in childrens diets, the leading vegetables and fruits consumed by children and differences in dietary intake associated with vitamin C consumption. METHODS Data from 1,350 7- to 12-year-old and 908 13- to 18-year-old schoolchildren were obtained from the 1994-1996 Continuing Survey of Food Intakes by Individuals (CSFII). The children were stratified by age and gender and then split into three vitamin C consumption groups based upon two 24-hour recalls: low (0 to 30.0 mg), marginal (30.1 to 59.9 mg), and desirable (>60.0 mg). Data were analyzed by tabulation and by ANOVA followed by post hoc Scheffes test. Outcome measures included food groups and energy-adjusted intakes of micro- and macronutrients. RESULTS Among the 7- to 12-year-olds, 12% of boys and 13% of girls had mean vitamin C intakes that were less than 30 mg/day, and, among 13- to 18-year-olds, 14% of boys and 20% of girls had low vitamin C intakes. In addition to consuming significantly more vitamin C, children with desirable vitamin C intakes also consumed significantly more (p <0.001) energy-adjusted folate and vitamin B6; children with low vitamin C intakes tended to have significantly greater (p <0.001) energy-adjusted intakes of fat and saturated fat. Children with desirable vitamin C intakes consumed significantly more (p <0.006) high-vitamin C fruit juice, low-vitamin C vegetables and whole milk. Children with low vitamin C intakes on average consumed two daily servings of vegetables and fruits, of which less than 1/5 of a serving was citrus, while children with desirable vitamin C intakes consumed an average of one daily serving of citrus. CONCLUSIONS A considerable number of children drastically under-consumed vitamin C and total vegetables and fruits. Overall, children with desirable vitamin C intakes had healthier diets, including more milk and vegetables, than did their peers with low vitamin C intakes. Health care professionals should continue to promote at least five daily servings of vegetables and fruits and should advise parents that at least one of these should be rich in vitamin C.