A Classification System for Defining and Estimating Dietary Intake of Live Microbes in US Adults and Children.

BACKGROUND: Consuming live microbes in foods may benefit human health. Live microbe estimates have not previously been associated with individual foods in dietary databases. OBJECTIVES: We aimed to estimate intake of live microbes in US children (aged 2-18 y) and adults (≥19 y) (n = 74,466; 51.2% female). METHODS: Using cross-sectional data from the NHANES (2001-2018), experts assigned foods an estimated level of live microbes per gram [low (Lo), <104 CFU/g; medium (Med), 104-107 CFU/g; or high (Hi), >107 CFU/g]. Probiotic dietary supplements were also assessed. The mean intake of each live microbe category and the percentages of subjects who ate from each live microbe category were determined. Nutrients from foods with live microbes were also determined using the population ratio method. Because the Hi category comprised primarily fermented dairy foods, we also looked at aggregated data for Med or Hi (MedHi), which included an expanded range of live microbe-containing foods, including fruits and vegetables. RESULTS: Our analysis showed that 52%, 20%, and 59% of children/adolescents, and 61%, 26%, and 67% of adults, consumed Med, Hi, or MedHi foods, respectively. Per capita intake of Med, Hi, and MedHi foods was 69, 16, and 85 g/d for children/adolescents, and 106, 21, and 127 g/d for adults, respectively. The proportion of subjects who consumed live microbes and overall per capita intake increased significantly over the 9 cycles/18-y study period (0.9-3.1 g/d per cycle in children across categories and 1.4 g/d per cycle in adults for the Med category). CONCLUSIONS: This study indicated that children, adolescents, and adults in the United States steadily increased their consumption of foods with live microbes between the earliest (2001-2002) and latest (2017-2018) survey cycles. Additional research is needed to determine the relations between exposure to live microbes in foods and specific health outcomes or biomarkers.

Prebiotic Dietary Fiber and Gut Health: Comparing the in Vitro Fermentations of Beta-Glucan, Inulin and Xylooligosaccharide.

Prebiotic dietary fiber supplements are commonly consumed to help meet fiber recommendations and improve gastrointestinal health by stimulating beneficial bacteria and the production of short-chain fatty acids (SCFAs), molecules beneficial to host health. The objective of this research project was to compare potential prebiotic effects and fermentability of five commonly consumed fibers using an in vitro fermentation system measuring changes in fecal microbiota, total gas production and formation of common SCFAs. Fecal donations were collected from three healthy volunteers. Materials analyzed included: pure beta-glucan, Oatwell (commercially available oat-bran containing 22% oat ß-glucan), xylooligosaccharides (XOS), WholeFiber (dried chicory root containing inulin, pectin, and hemi/celluloses), and pure inulin. Oatwell had the highest production of propionate at 12 h (4.76 µmol/mL) compared to inulin, WholeFiber and XOS samples (p < 0.03). Oatwell's effect was similar to those of the pure beta-glucan samples, both samples promoted the highest mean propionate production at 24 h. XOS resulted in a significant increase in the genus Bifidobacterium after 24 h of fermentation (0 h:0.67 OTUs (operational taxonomic unit); 24 h:5.22 OTUs; p = 0.038). Inulin and WholeFiber increased the beneficial genus Collinsella, consistent with findings in clinical studies. All analyzed compounds were fermentable and promoted the formation of beneficial SCFAs.

A review of the characteristics of dietary fibers relevant to appetite and energy intake outcomes in human intervention trials.

Background: Many intervention studies have tested the effect of dietary fibers (DFs) on appetite-related outcomes, with inconsistent results. However, DFs comprise a wide range of compounds with diverse properties, and the specific contribution of these to appetite control is not well characterized.Objective: The influence of specific DF characteristics [i.e., viscosity, gel-forming capacity, fermentability, or molecular weight (MW)] on appetite-related outcomes was assessed in healthy humans.Design: Controlled human intervention trials that tested the effects of well-characterized DFs on appetite ratings or energy intake were identified from a systematic search of literature. Studies were included only if they reported 1) DF name and origin and 2) data on viscosity, gelling properties, fermentability, or MW of the DF materials or DF-containing matrixes.Results: A high proportion of the potentially relevant literature was excluded because of lack of adequate DF characterization. In total, 49 articles that met these criteria were identified, which reported 90 comparisons of various DFs in foods, beverages, or supplements in acute or sustained-exposure trials. In 51 of the 90 comparisons, the DF-containing material of interest was efficacious for ≥1 appetite-related outcome. Reported differences in material viscosity, MW, or fermentability did not clearly correspond to differences in efficacy, whereas gel-forming DF sources were consistently efficacious (but with very few comparisons).Conclusions: The overall inconsistent relations of DF properties with respect to efficacy may reflect variation in measurement methodology, nature of the DF preparation and matrix, and study designs. Methods of DF characterization, incorporation, and study design are too inconsistent to allow generalized conclusions about the effects of DF properties on appetite and preclude the development of reliable, predictive, structure-function relations. Improved standards for characterization and reporting of DF sources and DF-containing materials are strongly recommended for future studies on the effects of DF on human physiology. This trial was registered at http://www.crd.york.ac.uk/PROSPERO as CRD42015015336.

Carbohydrates, dietary fiber, and resistant starch in white vegetables: links to health outcomes.

Vegetables are universally promoted as healthy. Dietary Guidelines for Americans 2010 recommend that you make half of your plate fruits and vegetables. Vegetables are diverse plants that vary greatly in energy content and nutrients. Vegetables supply carbohydrates, dietary fiber, and resistant starch in the diet, all of which have been linked to positive health outcomes. Fiber lowers the incidence of cardiovascular disease and obesity. In this paper, the important role of white vegetables in the human diet is described, with a focus on the dietary fiber and resistant starch content of white vegetables. Misguided efforts to reduce consumption of white vegetables will lower intakes of dietary fiber and resistant starch, nutrients already in short supply in our diets.

White potatoes, human health, and dietary guidance.

The white potato is a concentrated source of carbohydrate, dietary fiber, and resistant starch and continues to be the staple food of choice for many cultures. The white potato is also a concentrated source of vitamin C and potassium. Two of the nutrients in white potatoes, dietary fiber and potassium, have been designated as nutrients of concern in the 2010 Dietary Guidelines for Americans. Potatoes are often maligned in nutrition circles because of their suspected link to obesity, and popular potato foods often contain more fat calories than carbohydrate calories. Some food guides do not include potatoes in the vegetable group because of their association with high-fat diets. However, potatoes should be included in the vegetable group because they contribute critical nutrients. All white vegetables, including white potatoes, provide nutrients needed in the diet and deserve a prominent position in food guides.

Effects of short-chain fructooligosaccharides on satiety responses in healthy men and women.

In view of a dramatic increase in the incidence of obesity, the present study examined the appetite effects of a functional fiber as a potential dietary intervention. Fiber may increase satiety. Satiety effects also may be linked to colonic fermentation. Short-chain fructooligosaccharide (scFOS) are fermentable fibers that can be added to foods to influence these actions. The primary objective of this study was to determine if scFOS affects satiety and hunger and has an additive effect on food intake. Using a double-blind crossover design, 20 healthy subjects were assigned to consume two separate doses of 0 g, 5 g, or 8 g of scFOS. The first dose was mixed into a hot cocoa beverage and served with a breakfast meal of a bagel and cream cheese. A beverage was used in the test meal due to the ease with which scFOS can be added to this medium. Satiety was assessed with visual analogue scales (VASs) at 0, 15, 30, 45, 60, 90, 120, 180, and 240 min. Ad libitum food intake was measured at a lunch meal provided at the test site at 240 min. Subjects then recorded their food intake over the remainder of the 24-h study day. The second dose of scFOS was consumed in the form of 3 solid, chocolate-flavored chews (51-67 total kcal) without additional food or drink, 2h prior to the subject's dinner meal. Breath hydrogen measures were collected prior to the breakfast test meal (0 min) and the ad libitum lunch (240 min). Gastrointestinal tolerance was evaluated over the course of the 24-h study day using VAS. All treatments were well tolerated. No differences in subjective satiety over the morning, or food intake at lunch, were found. Over the remainder of the day, the high dose of scFOS reduced food intake in women, but increased food intake in men, suggesting a gender difference in the longer-term response. Breath hydrogen, used as a marker of fermentation, increased in a dose-dependent manner. These results indicate that scFOS undergoes fermentation within 240 min; however, acceptable amounts of scFOS did not enhance acute satiety or hunger.

Wheat dextrin, psyllium, and inulin produce distinct fermentation patterns, gas volumes, and short-chain fatty acid profiles in vitro.

Dietary fiber fermentation decreases luminal pH by the production of short-chain fatty acids (SCFAs). Additional proposed physiological benefits of fiber fermentation include decreased growth of pathogenic bacteria, increased mineral absorption, and serving as an energy source for the colon epithelium. This study examined three common fiber supplements--wheat dextrin (WD) (Benefiber, Novartis Consumer Health Inc., Parsippany, NJ, USA), psyllium (PS) (Metamucil, Procter & Gamble, Cincinnati, OH, USA), and inulin (Fiber Sure, Procter & Gamble)--for pH, SCFAs, and gas production. An established in vitro fermentation model was used to simulate colonic fermentation at 0, 4, 8, 12, and 24 hours. At 24 hours, WD and inulin significantly decreased pH compared to PS. Inulin produced significantly more hydrogen and total gas. All treatments produced similar total SCFA concentrations at 24 hours; however, the rate of production was different. PS had a declining rate of SCFA production from 12 to 24 hours, whereas WD and inulin had a higher rate during that period. Fast-fermenting substrates may not provide as much SCFAs to the distal colon as slow-fermenting substrates. Differences in fermentation rate, gas production, and SCFA production observed for WD, PS, and inulin may affect their gastrointestinal tolerance and require further study.

Effect of fenugreek fiber on satiety, blood glucose and insulin response and energy intake in obese subjects.

Eighteen healthy obese subjects participated in a single blind, randomized, crossover study of three test breakfasts, containing 0 g (control), 4 g or 8 g of isolated fenugreek fiber. Subjects recorded ratings of hunger, satiety, fullness and prospective food consumption using visual analog scales (VAS) every 30 min for 3.5 h. Postprandial blood glucose and insulin responses were measured. Energy intake from an ad libitum lunch buffet and for the remainder of the day was assessed. The 8 g dose of fenugreek fiber significantly increased mean ratings of satiety and fullness, and reduced ratings of hunger and prospective food consumption (P < 0.05). Palatability was significantly reduced with increasing doses of fenugreek fiber (P < 0.05). No differences were observed for area under the curve (AUC) for blood glucose among treatments. An increase in insulin AUC was found with 8 g fenugreek fiber. Energy intake at an ad libitum lunch buffet was significantly lower for 8 g than 4 g fenugreek fiber, but not significantly different from control, although there was a trend towards a lower intake (p = 0.11). No differences were observed for energy intake for the remainder of the day. Fenugreek fiber (8 g) significantly increased satiety and reduced energy intake at lunch, suggesting it may have short-term beneficial effects in obese subjects. Satiety results were not related to postprandial blood glucose.

Assessment of dietary fiber fermentation: effect of Lactobacillus reuteri and reproducibility of short-chain fatty acid concentrations.

This investigation had two aims: (i) to determine the reproducibility of SCFA production of two fibers: wheat dextrin and inulin, in two separate in vitro batch fermentation systems, and (ii) to determine if the addition Lactobacillus reuteri, a probiotic bacterium, enhanced the fermentation of wheat dextrin, inulin, and psyllium using in vitro batch fermentation. Samples were removed at 0, 4, 8, 12, and 24 h. SCFAs were measured by GC. L. reuteri improved inulin's fermentation profile by reducing the total SCFA peak at 4 h and enhancing fermentation at 8 and 12 h. Wheat dextrin and psyllium were largely unaffected. Wheat dextrin's total SCFA and propionate production curves were steady and replicable, but concentration values varied between fermentations. Partially hydrolyzed guar gum (PHGG) and wheat dextrin had similar fermentation patterns from 0-8 h, but PHGG plateaued at 8 h for all measures. Psyllium produced peak SCFA concentrations at 8 h, similar to inulin. L. reuteri could be combined with inulin for enhancing fermentation, but it does not improve wheat dextrin or psyllium fermentation. Wheat dextrin will likely produce similar physiological within a group of individuals due to the reproducibility of fermentation.

Physiological effects of concentrated barley beta-glucan in mildly hypercholesterolemic adults.

OBJECTIVE: Barley fiber rich in beta-glucans lowers serum lipids, but is difficult to incorporate into products acceptable to consumers. We investigated the physiological effects of two concentrated barley beta-glucans on cardiovascular disease (CVD) endpoints and body weight in human subjects. METHODS: Hypercholesterolemic men and women (n = 90) were randomly assigned to one of two treatments: low molecular weight (low-MW) or high molecular weight (high-MW) concentrated barley beta-glucan consumed as a daily supplement containing 6 grams beta-glucan/day. Fasting blood samples were collected at baseline and week 6 and analyzed for total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, glucose, insulin, homocysteine and C-reactive protein (CRP). Dietary intakes, body weights, blood pressure, hunger ratings, and gastrointestinal symptoms were measured at baseline and 6 weeks. RESULTS: The only difference between treatments in lipid outcomes at week 6 was a reduction of the cholesterol/HDL ratio in the low-MW group and a small increase in the high-MW group. No changes were found in blood pressure, glucose, insulin, and gastrointestinal symptoms. Body weight decreased from baseline to 6 weeks in the high-MW group while body weight increased in the low-MW group. Levels of hunger decreased slightly in the low-MW group and decreased significantly in the high-MW group (P = 0.02) CONCLUSION: Overall, supplementation with isolated barley beta-glucans of different molecular weights had small effects on cardiovascular disease markers. Molecular weight of the barley fiber did alter effects on body weight with the high-MW fiber significantly decreasing body weight.

Comparison of different fibers for in vitro production of short chain fatty acids by intestinal microflora.

The fermentation of dietary fiber in the large intestine and the by-products of this fermentation are thought to protect against colonic diseases. As it is difficult to measure the fermentation of dietary fiber in an intact animal, in vitro techniques have been developed to compare the fermentability of various dietary fibers. The objective of this project was to compare short chain fatty acid (SCFA) production with different fibers in an in vitro fermentation model. A wide range of commercially available dietary fiber sources was compared for SCFA production. Fibers were fermented with a fecal innoculum for 0, 2, 4, 8, 12, and 24 hours. SCFAs were measured by gas chromatography. SCFA production varied among the fiber sources. Hydrolyzed guar gum and galactomannan produced the greatest amounts of total SCFAs. Butyrate production was higher with the fiber sources than the glucose control. Acetate production was less for psyllium than the other fibers. Thus, different dietary fiber sources are more readily fermented by fecal microflora. These differences most likely affect the physiological differences seen among dietary fiber sources.

No long-term benefits of supplementation with arabinogalactan on serum lipids and glucose.

We conducted a 6-month randomized, double-blind, parallel trial in which subjects consumed their usual diet plus arabinogalactan, a functional fiber isolated from either larch or tamarack. Healthy human subjects (28 men, 26 women) ages 18 to 55 years old consumed 8.4 g/day larch arabinogalactan (n=18), tamarack arabinogalactan (n=19), or a placebo of rice starch (n=17). Serum cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, apolipoprotein B, apolipoprotein A-I, glucose, and insulin were measured monthly. Three-day food records, body weight, blood pressure, and gastrointestinal symptom surveys were obtained monthly. Serum lipids seemed to decrease at month 2, but there were no statistically significant differences among diets for any measured endpoint. Arabinogalactan is a recognized soluble fiber and is currently being used in products because it is not viscous, is easily incorporated into foods and beverages, and is well accepted by consumers.

Effect of flaxseed and wheat bran on serum hormones and lignan excretion in premenopausal women.

OBJECTIVE: To examine the effects of flaxseed consumption (a lignan-rich plant food) alone and in combination with wheat bran on serum hormones and urinary lignan excretion in premenopausal women. METHODS: Sixteen subjects were studied for four feeding treatments lasting two menstrual cycles each in a randomized, crossover design. During each treatment, subjects consumed their habitual diets supplemented with baked goods containing no flaxseed or wheat bran, 10 g of flaxseed, 28 g of wheat bran, or 10 g of flaxseed plus 28 g of wheat bran/day. Serum samples collected during the mid-luteal phase of the second menstrual cycle of each diet treatment were analyzed for serum hormones and sex hormone binding globulin. Urine samples collected during the same time period were analyzed for urinary lignan excretion. RESULTS: There were no changes in serum hormone concentrations or sex hormone binding globulin on any of the treatments. Urinary lignan excretion significantly increased on diet treatments that included flaxseed, but inclusion of wheat bran did not significantly alter lignan excretion. CONCLUSIONS: Urinary lignan excretion increased with flaxseed consumption, but serum hormones did not change in this group of premenopausal women. Consumption of wheat bran with flaxseed did not alter urinary lignan excretion associated with flaxseed consumption.

Partially hydrolyzed guar gum: clinical nutrition uses.

OBJECTIVE: This paper provides a review of research on partially hydrolyzed guar gum that is relevant to clinical nutrition practice. METHODS: All relevant papers published on partially hydrolyzed guar gum were reviewed and the results summarized. RESULTS: Partially hydrolyzed guar gum (PHGG) is a water-soluble dietary fiber with a wide range of uses in clinical nutrition. Its low viscosity allows its use in enteral products and beverages. PHGG can be added to enteral formulas and food products as a dietary fiber source. PHGG provides the benefits associated with dietary fiber ingestion. Addition of PHGG to the diet reduced laxative dependence in a nursing home population. PHGG also reduced the incidence of diarrhea in septic patients receiving total enteral nutrition and reduced symptoms of irritable bowel syndrome. PHGG also increased production of Bifidobacterium in the gut. CONCLUSION: The ease of use of PHGG and its clinical effectiveness make it a good choice in clinical nutrition practice.

Types of dietary fat and soy minimally affect hormones and biomarkers associated with breast cancer risk in premenopausal women.

Fourteen premenopausal women participated in a randomized, crossover controlled feeding study of three diets, each two menstrual cycles long. We compared a high saturated fat Western diet (control diet) with two other diets: the control diet plus soy protein (soy diet) and the control diet with polyunsaturated fat (PUFA diet) replacing most of the saturated fat. We measured reproductive and serum hormones, urinary estrogen metabolites and isoflavonoids, and menstrual cycle length. In the follicular phase, prolactin concentrations significantly decreased by 3.6 micrograms/dl (P = 0.047), follicle-stimulating hormone concentrations slightly increased by 0.1 IU/l (P = 0.076), and cortisol concentrations slightly decreased by 81.8 nmol/l (P = 0.088) with the PUFA diet vs. the control diet. The soy diet slightly increased menstrual cycle length by 1.8 +/- 0.7 days (P = 0.088) and significantly increased (P < 0.0001) urinary isoflavonoid excretion. These well-controlled diets did not affect serum estrogens or urinary estrogen metabolites, suggesting that type of fat or consumption of soy with a high saturated fat diet may not alter breast cancer risk by these mechanisms.

Position of the American Dietetic Association: health implications of dietary fiber.

Dietary fiber consists of the structural and storage polysaccharides and lignin in plants that are not digested in the human stomach and small intestine. A wealth of information supports the American Dietetic Association position that the public should consume adequate amounts of dietary fiber from a variety of plant foods. Recommended intakes, 20-35 g/day for healthy adults and age plus 5 g/day for children, are not being met, because intakes of good sources of dietary fiber, fruits, vegetables, whole and high-fiber grain products, and legumes are low. Consumption of dietary fibers that are viscous lowers blood cholesterol levels and helps to normalize blood glucose and insulin levels, making these kinds of fibers part of the dietary plans to treat cardiovascular disease and type 2 diabetes. Fibers that are incompletely or slowly fermented by microflora in the large intestine promote normal laxation and are integral components of diet plans to treat constipation and prevent the development of diverticulosis and diverticulitis. A diet adequate in fiber-containing foods is also usually rich in micronutrients and nonnutritive ingredients that have additional health benefits. It is unclear why several recently published clinical trials with dietary fiber intervention failed to show a reduction in colon polyps. Nonetheless, a fiber-rich diet is associated with a lower risk of colon cancer. A fiber-rich meal is processed more slowly, which promotes earlier satiety, and is frequently less calorically dense and lower in fat and added sugars. All of these characteristics are features of a dietary pattern to treat and prevent obesity. Appropriate kinds and amounts of dietary fiber for the critically ill and the very old have not been clearly delineated; both may need nonfood sources of fiber. Many factors confound observations of gastrointestinal function in the critically ill, and the kinds of fiber that would promote normal small and large intestinal function are usually not in a form suitable for the critically ill. Maintenance of body weight in the inactive older adult is accomplished in part by decreasing food intake. Even with a fiber-rich diet, a supplement may be needed to bring fiber intakes into a range adequate to prevent constipation. By increasing variety in the daily food pattern, the dietetics professional can help most healthy children and adults achieve adequate dietary fiber intakes.