Mark D. Haub

Effects of Dietary Fiber and Its Components on Metabolic Health

Dietary fiber and whole grains contain a unique blend of bioactive components including resistant starches, vitamins, minerals, phytochemicals and antioxidants. As a result, research regarding their potential health benefits has received considerable attention in the last several decades. Epidemiological and clinical studies demonstrate that intake of dietary fiber and whole grain is inversely related to obesity, type two diabetes, cancer and cardiovascular disease (CVD). Defining dietary fiber is a divergent process and is dependent on both nutrition and analytical concepts. The most common and accepted definition is based on nutritional physiology. Generally speaking, dietary fiber is the edible parts of plants, or similar carbohydrates, that are resistant to digestion and absorption in the small intestine. Dietary fiber can be separated into many different fractions. Recent research has begun to isolate these components and determine if increasing their levels in a diet is beneficial to human health. These fractions include arabinoxylan, inulin, pectin, bran, cellulose, β-glucan and resistant starch. The study of these components may give us a better understanding of how and why dietary fiber may decrease the risk for certain diseases. The mechanisms behind the reported effects of dietary fiber on metabolic health are not well established. It is speculated to be a result of changes in intestinal viscosity, nutrient absorption, rate of passage, production of short chain fatty acids and production of gut hormones. Given the inconsistencies reported between studies this review will examine the most up to date data concerning dietary fiber and its effects on metabolic health.

Gut microbiome composition is linked to whole grain-induced immunological improvements.

The involvement of the gut microbiota in metabolic disorders, and the ability of whole grains to affect both host metabolism and gut microbial ecology, suggest that some benefits of whole grains are mediated through their effects on the gut microbiome. Nutritional studies that assess the effect of whole grains on both the gut microbiome and human physiology are needed. We conducted a randomized cross-over trial with four-week treatments in which 28 healthy humans consumed a daily dose of 60 g of whole-grain barley (WGB), brown rice (BR), or an equal mixture of the two (BR+WGB), and characterized their impact on fecal microbial ecology and blood markers of inflammation, glucose and lipid metabolism. All treatments increased microbial diversity, the Firmicutes/Bacteroidetes ratio, and the abundance of the genus Blautia in fecal samples. The inclusion of WGB enriched the genera Roseburia, Bifidobacterium and Dialister, and the species Eubacterium rectale, Roseburia faecis and Roseburia intestinalis. Whole grains, and especially the BR+WGB treatment, reduced plasma interleukin-6 (IL-6) and peak postprandial glucose. Shifts in the abundance of Eubacterium rectale were associated with changes in the glucose and insulin postprandial response. Interestingly, subjects with greater improvements in IL-6 levels harbored significantly higher proportions of Dialister and lower abundance of Coriobacteriaceae. In conclusion, this study revealed that a short-term intake of whole grains induced compositional alterations of the gut microbiota that coincided with improvements in host physiological measures related to metabolic dysfunctions in humans.

Consumption of cross-linked resistant starch (RS4XL) on glucose and insulin responses in humans.

Objective. The objective was to compare the postprandial glycemic and insulinemic responses to nutrition bars containing either cross-linked RS type 4 (RS4XL) or standard wheat starch in normoglycemic adults (n = 13; age = 27 ± 5 years; BMI = 25 ± 3 kg/m2). Methods. Volunteers completed three trials during which they consumed a glucose beverage (GLU), a puffed wheat control bar (PWB), and a bar containing cross-linked RS4 (RS4XL) matched for available carbohydrate content. Serial blood samples were collected over two hours and glucose and insulin concentrations were determined and the incremental area under the curve (iAUC) was calculated. Results. The RS4XL peak glucose and insulin concentrations were lower than the GLU and PWB (P < .05). The iAUC for glucose and insulin were lower following ingestion of RS4 compared with the GLU and PWB trials. Conclusions. These data illustrate, for the first time, that directly substituting standard starch with RS4XL, while matched for available carbohydrates, attenuated postprandial glucose and insulin levels in humans. It remains to be determined whether this response was due to the dietary fiber and/or resistant starch aspects of the RS4XL bar.

Resistance training preserves fat-free mass without impacting changes in protein metabolism after weight loss in older women.

This study assessed the effects of resistance training (RT) on energy restriction–induced changes in body composition, protein metabolism, and the fractional synthesis rate of mixed muscle proteins (FSRm) in postmenopausal, overweight women. Sixteen women (age 68 ± 1 years, BMI 29 ± 1 kg/m2, mean ± s.e.m.) completed a 16‐week controlled diet study. Each woman consumed 1.0 g protein/kg/day. At baseline (weeks B1–B3) and poststudy (weeks RT12–RT13), energy intake matched each subjects need and during weeks RT1–RT11 was hypoenergetic by 2,092 kJ/day (500 kcal/day). From weeks RT1 to RT13, eight women performed RT 3 day/week (RT group) and eight women remained sedentary (SED group). RT did not influence the energy restriction–induced decrease in body mass (SED −5.8 ± 0.6 kg; RT −5.0 ± 0.2 kg) and fat mass (SED −4.1 ± 0.9 kg; RT −4.7 ± 0.5 kg). Fat free mass (FFM) and total body water decreased in SED (−1.6 ± 0.4 and −2.1 ± 0.5 kg) and were unchanged in RT (−0.3 ± 0.4 and −0.4 ± 0.7 kg) (group‐by‐time, P ≤ 0.05 and P = 0.07, respectively). Protein–mineral mass did not change in either group (SED 0.4 ± 0.2 kg; RT 0.1 ± 0.4 kg). Nitrogen balance, positive at baseline (2.2 ± 0.3 g N/day), was unchanged poststudy. After body mass loss, postabsorptive (PA) and postprandial (PP) leucine turnover, synthesis, and breakdown decreased. Leucine oxidation and balance were not changed. PA and total (PA + PP) FSRm in the vastus lateralis were higher after weight loss. RT did not influence these protein metabolism responses. In summary, RT helps older women preserve FFM during body mass loss. The comparable whole‐body nitrogen retentions, leucine kinetics, and FSRm between groups are consistent with the lack of differential protein–mineral mass change.

Different Types of Resistant Starch Elicit Different Glucose Reponses in Humans

The purpose of this study was to determine whether different types of resistant starch (RS) elicited different glycemic responses. Eleven healthy subjects consumed solutions containing 30 g of either dextrose (DEX), resistant starch type 2 (RS2), or cross-linked resistant wheat starch type 4 (RS4XL) on three separate occasions, which were assigned randomly. Finger stick blood samples were collected before and over the following two hours and measured for glucose. The incremental area under the curve (iAUC) for the glucose response was calculated for all trials. The two types of resistant starch significantly (P < .05) decreased iAUC compared with DEX. The response with RS4XL was significantly decreased compared with the RS2 trial. These data demonstrate that different types of resistant starch elicit significantly different glycemic responses.

A preliminary investigation on exercise intensities of gardening tasks in older adults.

Heart rate (HR) was measured continuously while men (n = 6) and women (n = 2) ages 71 to 85 years (M = 77.4, SD = 4.1) completed nine gardening tasks. HR and VO2 from a submaximal graded exercise test were used to estimate gardening VO2, energy expenditure, % HRmax, and metabolic equivalents (METs). Tasks were low to moderate intensity physical activity (1.6–3.6 METs); those which worked the upper and lower body were moderate intensity physical activity while those that worked primarily the upper body were low intensity physical activity.

Calcium-fortified beverage supplementation on body composition in postmenopausal women

BackgroundWe investigated the effects of a calcium-fortified beverage supplemented over 12 months on body composition in postmenopausal women (n = 37, age = 48–75 y).MethodsBody composition (total-body percent fat, %FatTB; abdominal percent fat, %FatAB) was measured with dual energy x-ray absorptiometry. After baseline assessments, subjects were randomly assigned to a free-living control group (CTL) or the supplement group (1,125 mg Ca++/d, CAL). Dietary intake was assessed with 3-day diet records taken at baseline and 12 months (POST). Physical activity was measured using the Yale Physical Activity Survey.ResultsAt 12 months, the dietary calcium to protein ratio in the CAL group (32.3 ± 15.6 mg/g) was greater than the CTL group (15.2 ± 7.5 mg/g). There were no differences from baseline to POST between groups for changes in body weight (CAL = 0.1 ± 3.0 kg; CTL = 0.0 ± 2.9 kg), %FatTB (CAL = 0.0 ± 2.4%; CTL = 0.5 ± 5.4%), %FatAB (CAL = -0.4 ± 8.7%; CTL = 0.6 ± 8.7%), or fat mass (CAL = 1.3 ± 2.6 kg; CTL = 1.3 ± 2.7 kg).ConclusionThese results indicate that increasing the calcium to protein ratio over two-fold by consuming a calcium-fortified beverage for 12 months did not decrease body weight, body fat, or abdominal fat composition in postmenopausal women.

Rice-Shaped Extruded Kernels: Physical, Sensory, and Nutritional Properties

Rice-shaped kernels were produced from micronutrient-fortified blends of corn and wheat flours, sorghum and wheat flours, or rice flour alone using a pilot-scale twin screw extruder. The color of extruded kernels from rice flour was similar to that of natural rice grain, but other treatments had significant color differences. Sorghum/wheat kernels had the highest cooking loss (13.4%) and water uptake (137.8%), and were also significantly different from other treatments with regard to instrumental texture profile and descriptive analysis. Vitamin C retention in extruded kernels was the lowest, ranging from 4.3 to 27.6%, whereas iron and folic acid had high stability.

Postprandial lipemic and inflammatory responses to high-fat meals: a review of the roles of acute and chronic exercise

Postprandial lipemia is an independent risk factor for development of cardiovascular disease. Postprandial inflammation following the prolonged elevation of triglycerides occurring subsequent to ingestion of high-fat meals, provides a likely explanation for increased disease risk. Substantial evidence has shown that acute exercise is an effective modality for attenuation of postprandial lipemia following a high-fat meal. However, much of the evidence pertaining to exercise intensity, duration, and overall energy expenditure for reducing postprandial lipemia is inconsistent. The effects of these different exercise variables on postprandial inflammation is largely unknown. Long-term, frequent exercise, however, appears to effectively reduce systemic inflammation, especially in at-risk or diseased individuals. With regard to an acute postprandial response, without a recent bout of exercise, high levels of chronic exercise do not appear to reduce postprandial lipemia. This review summarizes the current literature on postprandial and inflammatory responses to high-fat meals, and the roles that both acute and chronic exercise play. This review may be valuable for health professionals who wish to provide evidence-based, pragmatic advice for reducing postprandial lipemia and cardiovascular disease risk for their patients. A brief review of proposed mechanisms explaining how high-fat meals may result in pro-inflammatory and pro-atherosclerotic environments is also included.

Novel Resistant Potato Starches on Glycemia and Satiety in Humans

This study was designed to determine the efficacy of two novel type-four resistant starches (RS4) on postprandial glycemia and ratings of fullness. Volunteers (n = 10) completed completed five interventions designed to determine the glycemic and satiety (fullness) effects of the starches (38 g,) alone and when added on top of available carbohydrate. The dose of the starches provided 30 g of resistant starch per treatment. The treatments were: commercial resistant starch added to water (PF−), noncommercial resistant starch added to water (PR−), dextrose solution (DEX, 50 g), and DEX with PenFibe starch (PF+), and DEX with the non-commercial starch added (PR+). Blood glucose was measured in the fasted state and following the randomly assigned treatments at 30, 45, 60, 90, and 120 minutes post-consumption. A visual analog scale was used to determine fullness at each time point. There were no differences in the glucose incremental areas under the curve (iAUC) for PF+ and PR+ compared with DEX. The PF− and PR− treatments had decreased (P < 0.05) iAUCs for glucose compared with DEX, PF+, and PR+. There were no treatment differences for RoF. The dose (38 g) of starches did not to alter glucose responses when added on top of 50 g of dextrose.