Agave Inulin Supplementation Affects the Fecal Microbiota of Healthy Adults Participating in a Randomized, Double-Blind, Placebo-Controlled, Crossover Trial.

BACKGROUND: Prebiotics resist digestion, providing fermentable substrates for select gastrointestinal bacteria associated with health and well-being. Agave inulin differs from other inulin type fibers in chemical structure and botanical origin. Preclinical animal research suggests these differences affect bacterial utilization and physiologic outcomes. Thus, research is needed to determine whether these effects translate to healthy adults. OBJECTIVE: We evaluated agave inulin utilization by the gastrointestinal microbiota by measuring fecal fermentative end products and bacterial taxa. METHODS: A randomized, double-blind, placebo-controlled, 3-period, crossover trial was undertaken in healthy adults (n = 29). Participants consumed 0, 5.0, or 7.5 g agave inulin/d for 21 d with 7-d washouts between periods. Participants recorded daily dietary intake; fecal samples were collected during days 16-20 of each period and were subjected to fermentative end product analysis and 16S Illumina sequencing. RESULTS: Fecal Actinobacteria and Bifidobacterium were enriched (P < 0.001) 3- and 4-fold after 5.0 and 7.5 g agave inulin/d, respectively, compared with control. Desulfovibrio were depleted 40% with agave inulin compared with control. Agave inulin tended (P < 0.07) to reduce fecal 4-methyphenol and pH. Bivariate correlations revealed a positive association between intakes of agave inulin (g/kcal) and Bifidobacterium (r = 0.41, P < 0.001). Total dietary fiber intake (total fiber plus 0, 5.0, or 7.5 g agave inulin/d) per kilocalorie was positively associated with fecal butyrate (r = 0.30, P = 0.005), tended to be positively associated with Bifidobacterium (r = 0.19, P = 0.08), and was negatively correlated with Desulfovibrio abundance (r = -0.31, P = 0.004). CONCLUSIONS: Agave inulin supplementation shifted the gastrointestinal microbiota composition and activity in healthy adults. Further investigation is warranted to determine whether the observed changes translate into health benefits in human populations. This trial was registered at clinicaltrials.gov as NCT01925560.

The effects of whole grain high-amylose maize flour as a source of resistant starch on blood glucose, satiety, and food intake in young men.

The objective of this study was to determine the dose response effect of whole grain high-amylose maize (HAM) flour as a source of resistant starch (RS) on blood glucose, appetite and short-term food intake. In a repeated-measures crossover trial, healthy men (n = 30, 22.9 ± 0.6 y, BMI of 22.6 ± 0.3 kg/m(2)) were randomly assigned to consume 1 of 3 cookies once a week for 3 wk. Cookies were control (100% wheat flour), low-dose (63% wheat flour,37% HAM flour), and high-dose (33% wheat flour, 67% HAM flour) providing 53.5, 43.5, and 36.3 g of available carbohydrate, respectively. Ad libitum food intake was measured 120 min at a pizza meal, blood glucose and subjective appetite were measured after consumption of the cookie (0 to 120 min) and after the pizza meal (140 to 200 min). Blood glucose concentrations were lower at 30 and 45 min after high-dose treatment, and at 120 min after both high- and low-dose treatments compared to control (P < 0.05). Blood glucose AUC before the pizza meal (0 to 120 min) was 44% and 14% lower, and higher by 43% and 41% after the pizza meal (140 to 200 min) compared with control. Yet despite the higher response following the meal, cumulative AUC (0 to 200 min) was still 22% lower after the high-dose treatment (P < 0.05). All treatments equally suppressed subjective appetite and there was no effect on food intake. In conclusion, HAM flour as a source of RS and incorporated into a cookie was associated with better glycemic control in young men.

Gastrointestinal tolerance and utilization of agave inulin by healthy adults.

Little clinical research exists on agave inulin as a fiber source. Due to differences in botanical origin and chemical structure compared to other inulin-type fibers, research is needed to assess gastrointestinal (GI) tolerance following consumption. This study aimed to evaluate GI tolerance and utilization of 5.0 and 7.5 g per day of agave inulin in healthy adults (n = 29) using a randomized, double-blind, placebo-controlled crossover trial consisting of three 21 day periods with 1 week washouts among periods. GI tolerance was assessed via daily and weekly questionnaires, three fecal samples were collected on days 16-20 of each period, and breath hydrogen testing was completed on the final day of each treatment period. Survey data were compared using a generalized linear mixed model. All other outcomes were analyzed using a mixed linear model with a repeated measures procedure. Composite GI intolerance scores for 5.0 and 7.5 g treatments were both greater (P < 0.05) than control, however, scores were low, with means of 0.4, 1.9, and 2.3 on a 0-12 point composite scale for 0, 5.0, and 7.5 g treatments, respectively. There were slight increases (P < 0.05) in bloating, flatulence, and rumbling frequency with 5.0 and 7.5 g agave inulin. Abdominal pain and rumbling intensity were marginally greater (P < 0.05) with 7.5 g. Bloating and flatulence intensity increased (P < 0.05) with 5.0 g and 7.5 g. Agave inulin did not affect diarrhea (P > 0.05). Number of bowel movements per day increased, stools were softer, and stool dry matter percentage was lower with 7.5 g (P < 0.05). Breath hydrogen concentrations increased (P < 0.001) from 5-8 hour postprandial when participants consumed agave inulin compared to control. These data demonstrate that doses up to 7.5 g per day of agave inulin led to minimal GI upset, do not increase diarrhea, and improve laxation in healthy young adults.

Resistant starch from high-amylose maize increases insulin sensitivity in overweight and obese men.

This study evaluated the effects of 2 levels of intake of high-amylose maize type 2 resistant starch (HAM-RS2) on insulin sensitivity (S(I)) in participants with waist circumference ≥89 (women) or ≥102 cm (men). Participants received 0 (control starch), 15, or 30 g/d (double-blind) of HAM-RS2 in random order for 4-wk periods separated by 3-wk washouts. Minimal model S(I) was assessed at the end of each period using the insulin-modified i.v. glucose tolerance test. The efficacy evaluable sample included 11 men and 22 women (mean ± SEM) age 49.5 ± 1.6 y, with a BMI of 30.6 ± 0.5 kg/m2 and waist circumference 105.3 ± 1.3 cm. A treatment main effect (P = 0.018) and a treatment × sex interaction (P = 0.033) were present. In men, least squares geometric mean analysis for S(I) did not differ after intake of 15 g/d HAM-RS2 (6.90 × 10⁻5 pmol⁻¹ · L⁻¹ × min⁻¹) and 30 g/d HAM-RS2 (7.13 × 10⁻5 pmol⁻¹ · L⁻¹ × min⁻¹), but both were higher than after the control treatment (4.66 × 10⁻5 pmol⁻¹ · L⁻¹ × min⁻¹) (P < 0.05). In women, there was no difference among the treatments (overall least squares ln-transformed mean ± pooled SEM = 1.80 ± 0.08; geometric mean = 6.05 × 10⁻5 pmol⁻¹ · L⁻¹ × min⁻¹). These results suggest that consumption of 15-30 g/d of HAM-RS2 improves S(I) in men. Additional research is needed to understand the mechanisms that might account for the treatment × sex interaction observed.

Effects of moderate (MF) versus lower fat (LF) diets on lipids and lipoproteins: a meta-analysis of clinical trials in subjects with and without diabetes.

BACKGROUND: Dyslipidemia increases coronary heart disease (CHD) risk and often presents in diabetes, which amplifies risk of CHD. Lower fat (LF) diets increase triglyceride (TG) and decrease high-density lipoprotein cholesterol (HDL-C); moderate fat (MF) diets decrease TG and lower HDL-C less. OBJECTIVE: To quantify the magnitude of lipid and lipoprotein responses to MF versus LF cholesterol-lowering weight maintenance diets in subjects with and without diabetes. METHODS: A meta-analysis of 30 controlled-feeding studies (n = 1213 subjects) was conducted to evaluate LF versus MF diets on lipids and lipoproteins in subjects with and without diabetes. RESULTS: In all subjects, MF and LF diets decreased low-density lipoprotein cholesterol (LDL-C) similarly. MF diets decreased HDL-C less versus LF diets. The estimated increase in HDL-C after MF diets versus LF diets was 2.28 mg/dL (95% confidence interval 1.66 to 2.90 mg/dL, P < .0001). MF diets decreased TG, whereas LF diets increased TG. The decrease in TG was -9.36 mg/dL (-12.16 to -6.08 mg/dL, P < .00001) for MF versus LF diets. In subjects with diabetes, there was a similar increase in HDL-C (2.28 mg/dL) versus subjects without diabetes; however, there was a greater reduction in TG (-24.79 mg/dL, P < .05) on the MF diet. Subjects with diabetes had greater reductions in the total cholesterol (TC) to HDL-C ratio (TC:HDL-C) (-0.62, P < .0001) and non-HDL-C (-5.39 %, P < .06) after MF versus LF diets. CONCLUSIONS: Both men and women had greater estimated reductions (6.37% and 9.34%, respectively) in predicted CHD risk after MF diets compared to LF diets. Moreover, based on greater reductions in TG, the TC:HDL-C ratio and non-HDL-C in subjects with diabetes, the CHD risk reduction would be greater for a MF versus a LF weight maintenance, cholesterol-lowering diet.

Effects of L-phenylalanine on energy intake in overweight and obese women: interactions with dietary restraint status.

L-Phenylalanine (Phe), is a potent releaser of the satiety hormone, cholecystokinin (CCK) and previous studies, conducted primarily in men, show that ingestion of Phe reduces energy intake. The objective of the current study was to test the effects of Phe on energy intake in overweight and obese women. Subjects (n=32) received three treatments (high-dose (10 g Phe), low-dose (5 g Phe and 5 g glucose) or control (10 g glucose)) 20 min before an ad libitum lunch and dinner meal in a within-subjects', counterbalanced, double-blind study. No effect of Phe was found, however, interactions with dietary restraint status were detected in post-hoc analyses. Energy intake over the day was 11% lower following high-dose Phe versus control for women classified in the lower tertile of rigid restraint, a subscale of the dietary restraint scale, whereas no effects were noted for women in the middle and upper tertiles. High-dose Phe increased ratings of nausea, however, reduced energy intake in the high-dose condition was noted only for subjects with low nausea ratings. These results suggest that the satiety response to Phe is modulated by rigid restraint status and that reductions in food intake occur independently of Phe's effects on nausea.

Dietary restraint and menstrual cycle phase modulated L-phenylalanine-induced satiety.

l-phenylalanine (Phe) has been shown to elicit release of the gut hormone cholecystokinin (CCK) and reduce energy intake. Furthermore, studies in some animal models demonstrate potentiation of CCK-induced satiety by estradiol (E(2)). As E(2) is elevated in the follicular phase, we expected greater satiety effects than in the luteal phase when the effects may be antagonized by concomitant elevations in progesterone (P). Women with low dietary restraint were tested over two cycles and received encapsulated Phe or dextrose (control) during both phases within each cycle. Data from 20 women and 32 menstrual cycles were analyzed. Daily energy intake was suppressed by 9% for Phe compared to control and 8% in the follicular versus luteal phase of the menstrual cycle. Significant three-way interactions showed that the effects of condition and phase differed as a function of status on the rigid dietary restraint subscale. Phe suppressed daily energy intake by 15% relative to control in the follicular phase for women in the lower 50th percentile of rigid restraint, whereas for women in the higher 50th percentile group, Phe reduced energy intake by 15% in the luteal phase. The results replicate previous findings showing effects of cycle phase and Phe on food intake. The interaction between variables suggests that rigid restraint status modulates the satiety response to Phe, possibly through effects of reproductive hormones. Further studies are needed to replicate these findings and examine other aspects of satiety that may be altered by rigid restraint status.

A high-glycemic meal pattern elicited increased subjective appetite sensations in overweight and obese women.

We examined the effects of variations in postprandial glycemia and insulinemia on subjective satiety in overweight and obese women. We altered the ingestion rate of a glucose beverage to model the postprandial effects of high- and low-glycemic meals. Fourteen women were tested in a within-subjects' design with two conditions: (1) Rapid, with a large glucose beverage consumed with breakfast and lunch and (2) Slow, with the same volume of glucose beverage consumed in eight portions (one with each meal, and the remaining seven at 20-min intervals after each meal). Meals were identical in the two conditions. Subjective appetitive sensations were measured with visual analog scales before and after meals, and hourly after each meal until 5 pm. Serum glucose and insulin were measured at similar time points. Subjects reported higher ratings of hunger and prospective consumption in the Rapid versus Slow condition at 4h after breakfast and several hours after lunch. Serum glucose was more strongly correlated with the appetitive ratings in the Rapid than the Slow condition, and explained more of the variance (20-31%) than insulin (2-4%). The results of this study support the glucostatic theory linking dynamic changes in blood glucose with appetitive sensations.

Novel calcium-gelled, alginate-pectin beverage reduced energy intake in nondieting overweight and obese women: interactions with dietary restraint status.

BACKGROUND: Foods containing strong-gelling fibers may provide a safe and efficacious strategy for reducing food intake by stimulating endogenous satiety signaling. OBJECTIVE: A novel, 2-part beverage, consisting of alginate-pectin and calcium components, that forms a stable, fibrous gel in the stomach was tested to determine its effects on subjective satiety and food intake in overweight and obese women. DESIGN: The investigation was a within-subjects, double-blind, placebo-controlled study. Subjects (n = 29) ingested a 2-part beverage twice per day (once before breakfast and once midafternoon) for 7 d. Three alginate-pectin formulations were tested: 1.0 g, 2.8 g, and control (no fiber). Subjective satiety and ad libitum food intake were measured on days 1 and 7 of each 1-wk treatment period with a 1-wk washout between testings. RESULTS: A significant reduction in food intake was observed at dinner for both formulations compared with the control formulation. The effects of the gel beverage differed as a function of rigid dietary restraint status. Women in the lower 50th percentile of rigid restraint consumed 12% less energy during the day and 22% less for the evening snack in the 2.8-g condition compared with the control condition. No effect was found for women in the upper 50th percentile of rigid restraint. CONCLUSIONS: Consumption of a postingestion, calcium-gelled fiber beverage twice daily reduced energy intake in overweight and obese women with low rigid restraint scores. Use of foods designed to enhance satiety may be an effective adjunctive therapy for weight loss; however, more research is needed to determine how dietary restraint alters this response.

A reliable, valid questionnaire indicates that preference for dietary fat declines when following a reduced-fat diet.

This study establishes the reliability and validity of the Fat Preference Questionnaire, a self-administered instrument to assess preference for dietary fat. Respondents select the food which tastes better and is eaten more frequently from 19 sets of food. Each set is comprised of related foods differing in fat content. The questionnaire was administered to women in laboratory-based (n=63), cross-sectional (n=150), and weight-loss (n=71) studies. The percentage of food sets in which high-fat foods were reported to "taste better" (TASTE score) and to be "eaten more often" (FREQ score) was determined. A measure of dietary fat restriction (DIFF) was created by subtracting TASTE from FREQ. Food intake was assessed by direct measure, 24-h recall, or food diary. Additionally, participants completed a standard survey assessing dietary restraint. Test-retest correlations were high (r=0.75-0.94). TASTE and FREQ scores were positively correlated with total fat intake (r=0.22-0.63). DIFF scores positively correlated with dietary restraint (r=0.39-0.52). Participants in the weight-loss trial experienced declines in fat consumption, TASTE and FREQ scores, and BMI values, and an increase in DIFF scores. Weight loss correlated with declines in FREQ (r=0.36) scores and increases in DIFF scores (r=-0.35). These data suggest that preference for dietary fat declines when following a reduced-fat diet and an increase in restraint for intake of dietary fat is important for weight loss. The Fat Preference Questionnaire is a stable, easily-administered instrument that can be used in research and clinical settings.

A randomized trial of the effects of two types of short-term hypocaloric diets on weight loss in women with polycystic ovary syndrome.

OBJECTIVE: We performed this study as a pilot experiment to investigate the short term effects of two diets of varying composition on weight loss as the primary outcome in obese women with polycystic ovary syndrome (PCOS) seeking fertility. DESIGN: Randomized clinical trial. SETTING: Academic medical center. PATIENT(S): Thirty-five obese women with PCOS. INTERVENTION(S): We examined the effects of a 1-month dietary intervention on the PCOS phenotype. Participants were randomized to one of two energy-restricted diets; high protein (HP: 30% protein, 40% carbohydrate, and 30% fat) or high carbohydrate (HC: 15% protein, 55% carbohydrate, and 30% fat). The fat content was held constant in both diets. MAIN OUTCOME MEASURE(S): Primary - change in body weight; Secondary - biometric, hormonal, lipid and lipoprotein, and markers of glucose homeostasis and energy metabolism. RESULT(S): Twenty-six women completed the study. Both the HP (-3.7 +/- 1.9 kg) and HC (-4.4 +/- 1.5 kg) diets resulted in significant weight loss, but there was no significant difference in mean weight loss between the two groups. There were also no differences between diets on a variety of measures including circulating androgens, measures of glucose metabolism, and leptin. However, the effects of a hypocaloric diet per se on improving metabolic and reproductive abnormalities in a group of PCOS women were marked by a decline in circulating androgens (P=.03), fasting and area under the curve (AUC) insulins (P<.05) on a 3-hour oral glucose tolerance test (OGTT), and fasting and AUC leptin levels (P<.0001). There was a high prevalence of menstrual bleeding during the trial (14 out of 26 patients). CONCLUSION(S): Those who completed the short-term hypocaloric diet had a significant weight loss and a significant improvement in their reproductive and metabolic abnormalities. There was no increased benefit to a high-protein diet. Future diet studies evaluating the ideal composition of a hypocaloric diet in women with PCOS will require a large study population, and will most likely require a multicenter trial.

Effects of moderate-fat (from monounsaturated fat) and low-fat weight-loss diets on the serum lipid profile in overweight and obese men and women.

BACKGROUND: Little evidence of the effects of moderate-fat (from monounsaturated fat) weight-loss diets on risk factors for cardiovascular disease exists because low-fat diets are typically recommended. Previous studies in weight-stable persons showed that a moderate-fat diet results in a more favorable lipid and lipoprotein profile (ie, lower serum triacylglycerol and higher HDL cholesterol) than does a low-fat diet. OBJECTIVE: We evaluated the effects of energy-controlled, low-fat and moderate-fat diets on changes in lipids and lipoproteins during weight loss and subsequent weight maintenance. DESIGN: We conducted a parallel-arm study design in overweight and obese [body mass index (in kg/m(2)): 29.8 +/- 2.4] healthy men and women (n = 53) assigned to consume a low-fat (18% of energy) or moderate-fat (33% of energy) diet for 6 wk to achieve weight loss, which was followed by 4 wk of weight maintenance. All foods were provided and body weight was monitored to ensure equal weight loss between groups. RESULTS: The moderate-fat diet elicited favorable changes in the lipoprotein profile. Compared with baseline, HDL cholesterol was unchanged, whereas triacylglycerol and the ratios of total and non-HDL cholesterol to HDL cholesterol were lower at the end of the weight-maintenance period in the moderate-fat diet group. Despite similar weight loss, triacylglycerol rebounded, HDL cholesterol decreased, and the ratios of total and non-HDL cholesterol to HDL cholesterol did not change during the 10-wk interval in the low-fat diet group. CONCLUSIONS: A moderate-fat weight-loss and weight-maintenance diet improves the cardiovascular disease risk profile on the basis of favorable changes in lipids and lipoproteins. There is merit in recommending a moderate-fat weight-loss diet.