A low-fat high-carbohydrate diet reduces plasma total adiponectin concentrations compared to a moderate-fat diet with no impact on biomarkers of systemic inflammation in a randomized controlled feeding study.

PURPOSE: We compared the effects of a eucaloric moderate-fat diet (18% protein, 36% fat, and 46% carbohydrate), a eucaloric low-fat high-carbohydrate diet (18% protein, 18% fat, and 64% carbohydrate), and a low-calorie (33% reduced) low-fat high-carbohydrate diet on biomarkers of systemic inflammation. METHODS: We randomly assigned 102 participants (age 21-76 years and BMI 19.2-35.5 kg/m(2)) to the three different diets for 6 weeks in a parallel design intervention trial. All foods were provided. Ninety-three participants completed all study procedures; 92 were included in the analyses. Endpoints included plasma C-reactive protein (CRP), interleukin-6 (IL-6), soluble tumor necrosis factor receptors I and II (sTNFRI and II), and adiponectin. RESULTS: In the unadjusted primary analyses, none of the endpoints were differentially affected by the dietary interventions despite the significantly greater reductions in body weight and fat mass in participants consuming the low-calorie low-fat diet compared to the eucaloric diets (p < 0.001). When including weight change in the model in secondary analysis, adiponectin tended to be increased with weight loss (time × weight change interaction, p = 0.051). Adjusted for weight change, adiponectin was reduced in the groups consuming the low-fat diets relative to the moderate-fat diet (p = 0.008). No effect of the intervention diets or weight loss on CRP, IL-6, or sTNFRI and II was seen in these secondary analyses. CONCLUSIONS: In relatively healthy adults, moderate weight loss had minimal effects on systemic inflammation, and raised plasma adiponectin only modestly. A lower dietary fat and higher carbohydrate content had little impact on measures of systemic inflammation, but reduced adiponectin concentrations compared to a moderate-fat diet. The latter may be of concern given the consistent and strong inverse association of plasma adiponectin with many chronic diseases.

Diet quality in young adults and its association with food-related behaviours.

OBJECTIVE: To determine the diet quality of a group of young adults and explore its associations with two food-related behaviours (involvement in meal preparation and consumption of commercially prepared meals). DESIGN: Cross-sectional study of young adults. Sample characteristics, food-related behaviours and dietary intake were assessed using a self-administered questionnaire including an FFQ. Diet quality was measured using the fifteen-item Dietary Guideline Index (DGI) designed to assess adherence to Australian dietary guidelines. One-way ANOVA, t tests and multiple linear regression analyses were used to explore the relationships between DGI scores, sample characteristics and food-related behaviours. SETTING: University students enrolled in an undergraduate nutrition class, Melbourne, Australia. SUBJECTS: Students (n 309) aged 18-36 years. RESULTS: The DGI score was normally distributed, with a mean score of 93·4 (sd 17·1) points (range 51·9-127·4 points), out of a possible score of 150 points. In multivariate analyses adjusted for age, sex, nationality, BMI and maternal education, cooking meals for oneself was positively associated with DGI score (ß = 0·15; 95 % CI 1·15, 10·03; P = 0·01); frequency of takeaway and frequency of convenience meal consumption were inversely associated with DGI score (ß = -0·21; 95 % CI -9·96, -2·32; P = 0·002 and ß = -0·16; 95 % CI -7·40, -0·97; P < 0·01, respectively). CONCLUSIONS: Cooking meals for oneself was linked to higher diet quality among young adults, while consumption of commercially prepared meals was associated with poorer diet quality. Maintaining education programmes that promote cooking skills within young adults has the potential to improve DGI scores.

Essential fatty acid intake and coronary heart disease risk factors among college students of 3 ethnic groups.

OBJECTIVES: Few studies address gender and ethnic variations in essential fatty acid (EFA) intake and risk factors for coronary heart disease (CHD). The purpose of this study was to estimate EFA intake among college students of 3 ethnic groups and compare the relationship between EFA intake and CHD risk factors. METHODS: Using a cross-sectional design, 300 subjects from 3 ethnic groups--one-third (n = 100) non-Hispanic white, one-third Hispanic, and one-third non-Hispanic black-completed the Cardiovascular Risk Assessment Instruments and a Food Frequency Questionnaire to determine fatty acid intake. Measured CHD risk factors were quantified as CHD Risk Point Standards (CHDRPS). RESULTS: Results showed that Hispanic females had a significantly higher mean percent intake of arachidonic acid and ratio of linoleic acid to alpha-linolenic acid than non-Hispanic white females, and Hispanic males had significantly higher mean percent intake of EPA and [EPA plus docosahexaenoic acid (DHA)] than non-Hispanic white males. An inverse correlation was found between CHDRPS and DHA among non-Hispanic blacks. A significant positive correlation was found between CHDRPS and linoleic acid among non-Hispanic white females, as well as serum homocysteine (tHcy) concentrations and the ratio of linoleic acid to alpha-linolenic acid intake among non-Hispanic black females. CONCLUSION: Gender and ethnic differences play a role in adherence to dietary guidelines, demonstrating relevance for future research in this area.

Cruciferous vegetable feeding alters UGT1A1 activity: diet- and genotype-dependent changes in serum bilirubin in a controlled feeding trial.

Chemoprevention by isothiocyanates from cruciferous vegetables occurs partly through up-regulation of phase II conjugating enzymes, such as UDP-glucuronosyltransferases (UGT). UGT1A1 glucuronidates bilirubin, estrogens, and several dietary carcinogens. The UGT1A1*28 polymorphism reduces transcription compared with the wild-type, resulting in decreased enzyme activity. Isothiocyanates are metabolized by glutathione S-transferases (GST); variants may alter isothiocyanate clearance such that response to crucifers may vary by genotype. We evaluated, in a randomized, controlled, crossover feeding trial in humans (n = 70), three test diets (single- and double-"dose" cruciferous and cruciferous plus apiaceous) compared with a fruit and vegetable-free basal diet. We measured serum bilirubin concentrations on days 0, 7, 11, and 14 of each 2-week feeding period to monitor UGT1A1 activity and determined effects of UGT1A1*28 and GSTM1/GSTT1-null variants on response. Aggregate bilirubin response to all vegetable-containing diets was statistically significantly lower compared with the basal diet (P < 0.03 for all). Within each UGT1A1 genotype, lower bilirubin concentrations were seen in *1/*1 in both single- and double-dose cruciferous diets compared with basal (P < 0.03 for both); *1/*28 in double-dose cruciferous and cruciferous plus apiaceous compared with basal, and cruciferous plus apiaceous compared with single-dose cruciferous (P < 0.02 for all); and *28/*28 in all vegetable-containing diets compared with basal (P < 0.02 for all). Evaluation of the effects of diet stratified by GST genotype revealed some statistically significant genotypic differences; however, the magnitude was similar and not statistically significant between genotypes. These results may have implications for altering carcinogen metabolism through dietary intervention, particularly among UGT1A1*28/*28 individuals.

Saw palmetto supplement use and prostate cancer risk.

Saw palmetto is an herb used to treat the symptoms of benign prostatic hyperplasia. In vitro studies have found that saw palmetto inhibits growth of prostatic cancer cells and may induce apoptosis. To evaluate whether saw palmetto supplements are associated with a reduced risk of prostate cancer, we conducted a prospective cohort study of 35,171 men aged 50-76 yr in western Washington state. Subjects completed questionnaires between 2000 and 2002 on frequency of use of saw palmetto supplements and saw palmetto-containing multivitamins over the previous 10 yr in addition to other information on supplement intake, medical history, and demographics. Men were followed through December 2003 (mean of 2.3 yr of follow-up) via the western Washington Surveillance, Epidemiology, and End Results cancer registry, during which time 580 developed prostate cancer. Ten percent of the cohort used saw palmetto at least once per week for a year in the 10 yr before baseline. No association was found between this level of use of saw palmetto and risk of prostate cancer development [hazard ratio (HR) = 0.95; 95% confidence interval = 0.74-1.23] or with increasing frequency or duration of use. In this free-living population, use of commercial saw palmetto, which varies widely in dose and constituent ratios, was not associated with prostate cancer risk.

Effect of a low-fat diet on fatty acid composition in red cells, plasma phospholipids, and cholesterol esters: investigation of a biomarker of total fat intake.

BACKGROUND: The utility of fatty acids (FAs) as biomarkers of total fat intake is unknown. OBJECTIVE: We compared FA changes in red cells (RCs), plasma phospholipids (PLs), and cholesterol esters (CEs) in response to a low-fat diet (LFD) and a moderate-fat diet (MFD) and assessed whether individual or combination of FAs predict LFD. DESIGN: Postmenopausal women (n = 66) were randomly assigned to receive an LFD (17% of energy from fat) or an MFD (34% of energy from fat) for 6 wk. All foods were provided. FAs in diets and blood were determined by gas-liquid chromatography. FA changes between baseline and end of study were compared across diets by using t tests. FA predictors of an LFD were selected by logistic regression. RESULTS: Many FAs in RCs, PLs, and CEs responded differently to the 2 diets. Changes from baseline with an LFD for palmitic acid (16:0) (3-11% increase), behenic (22:0) and lignoceric (24:0) acids (3-20% decrease, in RCs and PLs only), cis-monounsaturated FA (MUFA) (25-35% increase), linoleic acid (18:2n-6) (11-13% decrease), trans octadecanoic acids (trans 18:1) (7-20% decrease), and n-6 highly unsaturated FA (HUFA) (2-8% increase) were significantly different from changes with an MFD. Individually, 18:2n-6 and trans 18:1 were strong predictors of an LFD [receiver operating characteristic (ROC) curves: 0.92-0.80). A logistic regression model with trans 18:1, 18:2n-6, and vaccenic acid (18:1n-7) predicted an LFD with high specificity and sensitivity (ROC curves: 0.99). CONCLUSIONS: Saturated FA, cisMUFA, n-6 HUFA, and exogenous FAs greatly differed in their response to the LFD and MFD. Parallel responses were observed in RCs, PLs, and CEs. A model with a combination of FAs almost perfectly differentiated the consumption of 34% fat from that of 17% fat.

Dietary fiber, potassium, magnesium and calcium in relation to the risk of preeclampsia.

OBJECTIVE: To explore the relation between preeclampsia risk and maternal intake of dietary fiber, potassium, magnesium and calcium. STUDY DESIGN: We conducted a case-control study of 172 preeclamptics and 339 normotensive controls. Maternal dietary intake was assessed using a food frequency questionnaire. Logistic regression procedures were used to estimate the association between each dietary factor and preeclampsia risk. RESULTS: Fiber intake was inversely associated with the risk of preeclampsia. When extreme quartiles of total fiber intake were compared, the odds ratio (OR) for preeclampsia was 0.46 (95% confidence interval [CI] 0.23-0.92). The multivariate OR for preeclampsia for women in the top quartile of potassium intake (> 4.1 g/d) versus the lowest quartile (< 2.4 g/d) was 0.49 (95% CI 0.24-0.99). There was some evidence ofa reduced risk of preeclampsia with a high intake of magnesium and calcium, though these results were not statistically significant. Intake offruits and vegetables, low-fat dairy products, total cereal and dark bread were each associated with a reduced risk of preeclampsia. CONCLUSION: Our results support previous reports that suggest that diets high in fiber and potassium are associated with a reduced risk of hypertension. Maternal intake of recommended amounts of foods rich in fiber, potassium and other nutrients may reduce the risk of preeclampsia.

Maternal plasma ascorbic Acid (vitamin C) and risk of gestational diabetes mellitus.

BACKGROUND: Antioxidants, particularly vitamin C (ascorbic acid), have the capacity to influence glucose tolerance. Modification of diet could reduce the likelihood of developing gestational diabetes mellitus. METHODS: In a prospective cohort study of pregnant women, we studied the association of maternal plasma ascorbic acid concentrations, measured at an average of 13 weeks' gestation, with subsequent risk of gestational diabetes. Maternal plasma ascorbic acid concentrations were determined using automated enzymatic procedures. Dietary vitamin C intake during the periconceptional period and early pregnancy was ascertained using a semiquantitative food frequency questionnaire. We fitted generalized linear models to derive estimates of relative risks and 95% confidence intervals (CIs). RESULTS: Approximately 4% (n = 33) of 755 women who completed pregnancy developed gestational diabetes mellitus. Plasma ascorbic acid concentrations were inversely associated with the risk of gestational diabetes (P for trend = 0.023). After adjusting for maternal age, race, prepregnancy adiposity, parity, family history of type 2 diabetes, and household income, women with plasma ascorbic acid <55.9 micromol/L (lowest quartile) experienced a 3.1-fold increased risk of gestational diabetes (95% CI = 1.0 - 9.7) compared with women whose concentrations were > or = 74.6 micromol/L (upper quartile). Women who consumed <70 mg vitamin C daily experienced a 1.8-fold increased risk of gestational diabetes compared with women who consumed higher amounts (95% CI = 0.8 - 4.4). CONCLUSIONS: If confirmed, our results raise the possibility that current efforts to encourage populations to consume diets rich in antioxidants, including vitamin C, could reduce the occurrence of gestational diabetes mellitus.

Vitamin C and the risk of gestational diabetes mellitus: a case-control study.

OBJECTIVE: To examine whether low maternal dietary intake of vitamin C and low maternal plasma ascorbic acid (AA) concentrations are associated with an increased risk of gestational diabetes mellitus (GDM). METHODS: Cases were 67 women with GDM meeting National Diabetes Data Group criteria. Controls were 260 women without such a diagnosis. Maternal dietary vitamin C consumption during the periconceptional period and during pregnancy was assessed using a 121-item, semiquantitative food frequency questionnaire. Maternal plasma AA concentrations were determined using automated enzymatic procedures on specimens collected during the intrapartum period. RESULTS: Mean maternal daily consumption of vitamin C and plasma AA concentrations were 10% and 31% lower, respectively, among GDM cases as compared with controls (130.7 +/- 10.2 vs. 145 +/- 4.9 mg/d, P = .190; 36 +/- 2.0 vs. 53 +/- 1.0 micromol/L, P <.001). After controlling for maternal age, race, prepregnancy adiposity, family history of type 2 diabetes, energy intake and income, women reporting low daily vitamin C intake (< 70 mg/d), as compared with the other women, experienced a 3.7-fold increased risk of GDM (odds ratio [OR] = 3.7, 95% confidence interval [CI] 1.7-8.2). There was a linear relation in risk of GDM with decreasing concentrations of plasma AA (P for linear trend <.001). After adjusting for confounders, women in the lowest quartile (< 42.6 micromol/L), as compared with women in the highest quartile (> 63.3 micromol/L), experienced > 12-fold increased risk of GDM (OR = 12.8, 95% CI 3.5-46.2). CONCLUSION: Low maternal dietary vitamin C intake and low plasma AA concentrations are associated with an increased risk of GDM. Large, prospective, cohort studies are needed to further evaluate the potential beneficial role of vitamin C and other antioxidants in the prevention of impaired glucose tolerance in pregnancy.

Dietary risk factors for invasive and in-situ cervical carcinomas in Bangkok, Thailand.

OBJECTIVE: Although human papillomavirus (HPV) may be a necessary cause of cervical cancer, most women with HPV infections do not develop this disease. This study was conducted to evaluate the possible effects of specific dietary factors on cervical carcinogenesis. METHODS: Fifty hospitalized in-situ cases and 125 controls were identified from family planning or gynecologic clinics associated with Siriraj hospital in Bangkok, Thailand, and 134 hospitalized invasive cases and 384 hospitalized controls from the public wards of Siriraj Hospital were administered a food-frequency questionnaire and tested for HPV DNA in exfoliated cervical cells. Odds ratios in relation to intake of foods high in vitamin C, folate, vitamin E, vitamin A, beta-carotene, retinol, and cruciferous vegetables were estimated using logistic regression in case-control comparisons and in case-case comparisons adjusted for HPV status. RESULTS: High intake of foods rich in vitamin A, and particularly high-retinol foods, were associated with a reduced risk of in-situ disease and less strongly also with a reduced risk of invasive as compared to in-situ disease. No association was found between intake of cruciferous vegetables, foods high in vitamin C, folate, vitamin E, and beta-carotene and risk of either in-situ or invasive cervical cancer. CONCLUSIONS: Increasing intake of foods rich in total vitamin A, and particularly high-retinol foods, may reduce risk of in-situ cervical cancer, and at the highest level of intake may inhibit progression to invasion. If others confirm these results they suggest means of reducing the risk of cervical cancer that are amenable to public health action.