Overweight among children and adolescents in a Native Canadian community: prevalence and associated factors

BACKGROUND

The prevalence of pediatric obesity in North America is increasing. Native American children are at especially high risk.

OBJECTIVES

The objective was to evaluate the prevalence of pediatric overweight and associated behavioral factors in a Native Canadian community with high rates of adult obesity and type 2 diabetes mellitus.

DESIGN

Height and weight were measured in 445 children and adolescents aged 2-19 y. Fitness level, television viewing, body image concepts, and dietary intake were assessed in 242 subjects aged 10-19 y. Overweight was defined as a body mass index > or =85th percentile value for age- and sex-specific reference data from the third National Health and Nutrition Examination Survey (NHANES III). Multiple logistic regression was used to examine factors associated with overweight, with adjustment for age and sex.

RESULTS

The overall prevalence of overweight in subjects aged 2-19 y was significantly higher than NHANES III reference data [boys: 27. 7% (95% CI: 21.8, 34.5); girls: 33.7% (95% CI: 27.9, 40.1)]. In the subset aged 10-19 y, > or =5 h television viewing/d was associated with a significantly higher risk of overweight than was < or =2 h/d [odds ratio (OR) = 2.52; 95% CI: 1.06, 5.98]. Subjects in the third and fourth quartiles of fitness had a substantially lower risk of overweight than did those in the first quartile [third quartile compared with first quartile: OR = 0.24 (95% CI: 0.09, 0.66); fourth quartile compared with first quartile: OR = 0.13 (95% CI: 0.03, 0. 48)]. Fiber consumption on the previous day was associated with a decreased risk of overweight (OR = 0.69; 95% CI: 0.47, 0.99 for each 0.77 g/MJ increase in fiber intake).

CONCLUSIONS

Pediatric overweight is a harbinger of future diabetes risk and indicates a need for programs targeting primary prevention of obesity in children and adolescents.

Effects of calcium concentration, acetate, and propionate on calcium absorption in the human distal colon

Previous studies have shown that the short-chain fatty acids acetate (Ac) and propionate (Pr) enhance the absorption of calcium (Ca) in the rectum and distal colon of humans, with Pr being more effective than Ac. To investigate the effect of Ac and Pr on the kinetics of Ca absorption from the human rectum and distal colon, six healthy subjects were studied. Solutions containing various concentrations of CaCl2.H2O with 56.3 mmol/L Ac, Pr, or NaCl were rectally infused to each subject. Rectal fluid was sampled at the end of the infusion (0 min), and 30 min later colonic contents were collected. Ca absorption for all treatments increased linearly with Ca concentration. For Ca + NaCl, the slope of regression line was 62 mumol.mmol-1.L Ca. With Ac + Ca, the slope of Ca absorption increased significantly to 113 mumol.mmol-1.L Ca, and with Pr + Ca, the slope increased to 159 mumol.mmol-1.L (P = 0.043 versus Ac + Ca) Ac and Pr absorption were increased by Ca. The data suggest that, over a physiologic range of Ca concentration, in the absence or presence of Ac and Pr, Ca is absorbed in the human rectum and distal colon by a non-saturable diffusion process, and that Ca absorption is enhanced by Ac and Pr. The data also suggest that both Ac and Pr absorption is stimulated by Ca.

Day-to-day consistency in amount and source of carbohydrate intake associated with improved blood glucose control in type 1 diabetes

OBJECTIVE

To determine if a relationship exists between blood glucose control and variability in nutrient intake from day-to-day in subjects with type 1 diabetes.

METHODS

Two three-day diet records and one measurement of glycated hemoglobin (HbA1c) were obtained from 272 subjects with type 1 diabetes treated with a mixture of regular and NPH insulins before breakfast and supper and using a standardized algorithm to adjust insulin dose according to the results of self-monitoring of blood glucose two to four times daily. Day-to-day variation in nutrient intake was expressed as the coefficient of variation (CV = SDx100/mean).

RESULTS

Nutrient intakes in the study population (mean +/- SD) were energy 8.35+/-2.43 MJ, fat 81+/-30 g, protein 94+/-28 g, carbohydrate 227+/-68 g, starch 126+/-38 g and dietary fiber 20+/-6 g with diet glycemic index being 84.2+/-7.4. Neither energy, nutrient intakes nor insulin dose was significantly related to HbA1c. Day-to-day variation of carbohydrate (p = 0.0097) and starch (p = 0.0016) intakes and diet glycemic index (p = 0.033) was positively related to HbA1c, and the associations remained significant when adjusted for age, sex, duration of diabetes and BMI. Day-to-day variation in energy, protein or fat intakes was not related to HbA1c.

CONCLUSIONS

Consistency in the amount and source of carbohydrate intake from day-to-day is associated with improved blood glucose control in people with type 1 diabetes, a result which supports continued educational efforts to achieve adherence to a diabetes diet plan. This conclusion may not apply to people on intensified insulin therapy who adjust their insulin dose based on their actual carbohydrate intake at each meal.

Effect of glucose, sucrose and fructose on plasma glucose and insulin responses in normal humans: comparison with white bread

OBJECTIVE

To determine the plasma glucose and insulin responses of various doses of glucose, sucrose, fructose and white bread in normal human subjects.

DESIGN

Plasma glucose and insulin were measured before and at various times after 8 subjects ate 13 different test meals in randomized order on separate days after an overnight fast. Test meals consisted of 500 ml of tea or water to which was added either nothing, 25, 50, or 100 g of glucose or sucrose, 25 or 50 g fructose, 50 g glucose plus 50 g fructose, or a 25, 50 or 100 g carbohydrate portion of white bread. The glycaemic (GI) and insulinaemic index (II) values of the sugars were calculated by expressing the incremental areas under the plasma glucose and insulin curves (AUC) after glucose, sucrose and fructose as a percentage of the respective AUC after white bread containing the same amount of carbohydrate.

SETTING

University teaching hospital clinical nutrition centre.

SUBJECTS

Lean, normal subjects (4 male, 4 female) 21-33 y of age.

RESULTS

Plasma insulin responses increased nearly linearly as carbohydrate intake increased from 0 to 100 g, but glycaemic responses increased by only 68% and 38% as carbohydrate intake increased from 25 to 50 g and 50 to 100g, respectively. The GI and II values of glucose, 149+/-16 and 147+/-18, respectively, were significantly greater than those of bread (100; P<0.05), while the values for fructose, 16+/-4 and 22+/-3 were significantly less than those of bread (P<0.001). GI values did not differ significantly from II values.

CONCLUSIONS

It is concluded that, in normal subjects, as carbohydrate intake is increased from 0 to 100 g, plasma insulin responses increase at a greater rate than plasma glucose responses. The insulinaemic responses elicited by glucose, sucrose or fructose are similar to those that would be expected from a starchy food with the same glycaemic index.

No relationship between carbohydrate intake and effect of acarbose on HbA1c or gastrointestinal symptoms in type 2 diabetic subjects consuming 30-60% of energy from carbohydrate

OBJECTIVE

To determine the relationship between carbohydrate intake and the effect of acarbose on HbA1c in subjects with type 2 diabetes treated with acarbose alone, acarbose plus sulfonylurea, acarbose plus metformin, or acarbose plus insulin.

RESEARCH DESIGN AND METHODS

We conducted a double-blind randomized placebo-controlled study in which subjects with diabetes in four treatment strata (77 on diet alone, 83 treated with metformin, 103 treated with sulfonylurea, and 91 treated with insulin) were randomized to treatment with placebo or acarbose for 12 months. Before randomization, and 3, 6, 9, and 12 months after randomization, fasting blood was obtained for HbA1c, and 3-day diet records were collected. Subjects who completed at least 6 months of acarbose therapy and provided at least three 3-day diet records were included.

RESULTS

In the 114 subjects included in this analysis, carbohydrate intake varied from approximately 30-60% of energy There was no significant relationship between carbohydrate intake and change in HbA1c in any of the four treatment strata (diet: n=26, r=0.35, P=0.076; metformin: n=27, r=0.26, P=0.19; sulfonylurea: n=35, r=0.24, P=0.16; insulin: n=25, r=-0.27, P=0.19). In the 80 subjects consuming <50% of energy from carbohydrate, the fall in HbA1c (7.83 +/-0.17% at baseline to 6.72+/-0.13% on acarbose, P < 0.001) was no different from that of the 34 subjects consuming >50% of energy from carbohydrate (7.55+/-0.25% at baseline to 6.66+/-0.23% on acarbose, P < 0.001). There was no difference in carbohydrate intake between those who dropped out of the study because of gastrointestinal side effects and those who did not, and there was no relationship between severity of symptoms and the composition of the diet.

CONCLUSIONS

In subjects with type 2 diabetes consuming 30-60% of energy from carbohydrate, the effect of acarbose on HbA1c and gastrointestinal symptoms was not related to carbohydrate intake. Because most people consume at least 30% of energy from carbohydrate, we conclude that no special diet is needed for acarbose to be effective in improving blood glucose control in the treatment of type 2 diabetes.

Aberrant crypt focus promotion and glucose intolerance: correlation in the rat across diets differing in fat, n-3 fatty acids and energy

McKeown-Eyssen (Cancer Epidemiol. Biomarkers Prevent., 3, 687-695, 1994) and Giovannucci (Cancer Causes Control, 6, 164-179, 1995), noting the striking similarity in lifestyle risk factors for colorectal cancer and insulin resistance, proposed that the hyperinsulinemia, glycemia and hypertriglyceridemia associated with insulin resistance promotes colon cancer. To compare the effect of diet on colon cancer promotion and insulin resistance in the F344 rat, we assessed the effect of fat, n-3 fatty acids and energy in pairwise comparisons on average size of aberrant crypt foci (ACF) and on glucose intolerance in the same animals in a single experiment. Diets high in fat and energy increased and diets with increased n-3 fatty acids and calorie restriction decreased both ACF growth and glucose intolerance compared with control diets. The measures of promotion of colon cancer and insulin resistance were strongly correlated (n = 98, r = 0.67, P < 0.001). In addition, both were highly correlated with daily energy intake (r = 0.62 and 0.66) and were also correlated with basal (post-prandial) insulin, glucose and triglycerides (r = 0.31-0.53, P < 0.01). We concluded that ACF growth and glucose intolerance are correlated for a wide range of diets and that increased circulating energy (glucose and triglycerides) may lead to both colon cancer promotion and insulin resistance.

Increased serum cholesterol in healthy human methane producers is confounded by age

It has been theorized that colonic production and absorption of short-chain fatty acids (SCFA) is different in methane producers (MP) compared with nonproducers (MNP). Because colonic SCFA may influence systemic lipid metabolism, blood lipids may differ in MP and MNP. To compare serum lipids and SCFA in fasting MP and MNP, we measured breath gases, serum lipids and SCFA in 167 healthy subjects and excluded subjects with abnormal blood lipids. The 66 MP were significantly older than the 63 MNP (49.5 +/- 16.0 vs. 39.6 +/- 17.0 y, P = 0.0009), and breath methane concentrations were weakly correlated with age in MP (r = 0.268, P = 0.03). Mean serum cholesterol was significantly higher in MP compared with MNP, but the differences were not significant after adjusting for age. No significant differences were observed in serum SCFA between the two groups. This study has shown that breath methane increases with age, which may be due to age-related increases in transit time and carbohydrate malabsorption. These results provide no conclusive link between colonic events and serum lipids in MP because, with age, methane production increased as did serum cholesterol. More research is required before any definite conclusions can be drawn.

Variation of postprandial plasma glucose, palatability, and symptoms associated with a standardized mixed test meal versus 75 g oral glucose

OBJECTIVE

To compare within-subject variability of plasma glucose measured 2 h after a glucose tolerance test (GTT) with that of plasma glucose measured 2 h after administration of a standardized test meal (diabetes screening product [DSP], Ceapro, Edmonton, Alberta, Canada) and to determine the relationship between the two sets of plasma glucose measurements.

RESEARCH DESIGN AND METHODS

Plasma glucose and insulin responses of 36 overnight-fasted subjects (10 lean normal, 9 obese normal, 9 with impaired glucose tolerance [IGT], and 8 with mild diabetes) were studied on eight different mornings after they consumed 75 g oral glucose or 50 g carbohydrate from the DSP. Each test meal was repeated four times by each subject. Within-subject coefficients of variation (CVs) (CV = 100 x SD/mean) of plasma glucose concentrations 2 h after administration of the GTT and DSP were compared by repeated measures ANOVA and linear regression analysis.

RESULTS

Mean plasma glucose 2 h after administration of the DSP (D) was linearly related to that 2 h after the GTT (G): G = 1.5 x D - 1.6 (r = 0.97, P < 0.0001). The CV of 2-h plasma glucose was significantly lower after administration of the DSP, 10.5 +/- 1.0%, than after the GTT, 12.7 +/- 1.18% (P = 0.025). The effect of test meal on CV differed in different groups of subjects (P = 0.018), with the largest difference found in IGT subjects, in whom the CV after DSP administration was 47% less than after the GTT (P = 0.0005). The DSP was significantly more palatable and produced fewer adverse symptoms than the GTT.

CONCLUSIONS

Plasma glucose concentrations measured 2 h after DSP administration are closely related to those measured 2 h after the GTT but are more consistent than the 2-h post-GTT concentrations within the critical IGT range. This finding suggests that measurement of plasma glucose 2 h after administration of the DSP may allow more precise discrimination among normal glucose levels, IGT, and diabetes than measurement of plasma glucose 2 h after the GTT.

Specific patterns of food consumption and preparation are associated with diabetes and obesity in a Native Canadian community

We examined the relationship between usual patterns of food intake, fattiness of food preparation and consumption, and diabetes and obesity status in a Native Canadian reserve in northwestern Ontario. Patterns of intake were estimated using a 34-item food frequency instrument. Scales and scores were developed using factor analysis procedures and were tested for reliability using coefficient alpha. Impaired glucose tolerance (IGT) and diabetes status was determined by administering a 75-g glucose tolerance test. A number of the food groups appear to have a protective effect in regard to IGT and diabetes, including vegetables [odds ratio (OR) = 0.41, confidence interval (CI) = 0.18-0.91], breakfast foods (OR = 0.41, CI = 0.18-0. 93) and hot meal foods (OR = 0.29, CI = 0.11-0.78). Most of these foods are relatively high in fiber and low in fat. High consumption of junk foods and the bread and butter group was associated with substantial increases in risk for diabetes (OR = 2.40, CI = 1.13-5. 10; OR = 2.22, CI = 1.22-4.41, respectively). These foods tend to be high in simple sugars, low in fiber and high in fat. More fatty methods of food preparation are also associated with increased risk for diabetes in this population (OR = 2.58, CI = 1.11-6.02). This information has been incorporated into an ongoing community-based diabetes prevention program in the community.

Insulin resistance and promotion of aberrant crypt foci in the colons of rats on a high-fat diet

McKeown-Eyssen and Giovannucci recently proposed that the etiology of insulin resistance (IR) and colorectal cancer (CRC) are related. They suggested that diets high in fat and energy and low in complex carbohydrates and a sedentary life-style lead to IR and that the associated hyperinsulinemia, hypertriglyceridemia, and glycemia lead to increased CRC risk through the growth-promoting effect of insulin or the increased availability of energy. We reasoned that if diet affects colon carcinogenesis through its effect on IR, evidence of colon cancer promotion would be preceded by evidence of IR. To test this expectation, we compared the effects of a high-fat (HF, 59% energy) diet and a low-fat (LF, 11% energy) diet on indirect measures of IR and promotion in azoxymethane-initiated F344 rats. Promotion was assessed as growth of aberrant crypt foci (ACF) at 100 days after initiation. The HF diet increased ACF size 1.4 times (95% confidence interval = 1.30-1.58) that of the LF diet. The HF diet also led to impaired oral glucose tolerance tests measured at 4, 32, 60, and 88 days and characterized by an average increased glucose concentration of 0.78 +/- 0.17 mmol/l (p < 0.001). It also resulted in an impaired intravenous glucose tolerance test and elevated levels of serum insulin after a glucose gavage. We concluded that with this model a high-fat diet leads to evidence of IR before it is possible to demonstrate CRC promotion, thus providing support, necessary but not sufficient, for the causal hypothesis linking IR and CRC. Possible mechanisms linking diet, IR, and promotion are considered.

Low dietary fiber and high protein intakes associated with newly diagnosed diabetes in a remote aboriginal community

The high prevalence of diabetes mellitus in North American aboriginal populations may be due to recent changes in lifestyle, including the adoption of a high-fat, low-fiber diet. To determine whether fat or fiber intakes were associated with new cases of diabetes, we studied 72% (728/1018) of residents aged > 9 y from a remote aboriginal community in northern Ontario using the 75-g oral-glucose-tolerance test and 24-h dietary recall. The mean fat intake of this population (36% of energy) was typical for North America, but fiber intake (1.2 g/MJ) was very low. Logistic-regression analysis, adjusted for age, sex, and body mass index, showed that a 1-SD increase in fiber intake reduced the risk of having diabetes by 39% (P = 0.026) whereas the same increase in protein intake increased the risk by 38% (P = 0.027). There was no significant effect of energy, fat, starch, or simple sugars. These data support Trowell's original dietary-fiber hypothesis that "... dietary fiber depleted starchy foods are conducive to the development of diabetes mellitus in susceptible human genotypes."

What is a high fiber diet?

There is no recognized definition of what constitutes a high fiber diet. Intakes of dietary fiber in different populations internationally vary widely from less than 20 g to more than 80 g per day. The types of foods contributing fiber also vary; in some countries cereals contribute the most fiber, in others leafy or root vegetables predominate. Vegetables have the highest fiber content per Kcal, and in most populations with fiber intakes over 50 g, vegetables contribute over 50% of total fiber intake. In rural Uganda, where the fiber hypothesis was first developed by Burkitt and Trowell, vegetables contribute over 90% of fiber intake. An experimental diet, the "Simian" diet, has been developed to mimic as closely as possible using human foods, the diet consumed by our simian ancestors the great apes. It is also similar to the Ugandan diet in containing large amounts of vegetables and 50 g fiber/1000 Kcal. Though nutritionally adequate, this diet is very bulky and not a suitable model for general recommendations. Dietary guidelines are that fat intake should be < 30% of energy, with a fiber intake of 20-35 g/d. These recommendations are inconsistent with a high fiber diet because, for people consuming more than about 2400 Kcal, low fiber choices for fruits and grains must be selected to keep dietary fiber intake within the range of 20-35 g. In a 30% fat, 1800 Kcal omnivorous diet, selection of wholemeal bread and whole fruit, results in a fiber intake over 35 g/d, and for and 1800 Kcal vegetarian diet, with substitution of modest amounts of peanut butter and beans for meats, dietary fiber intake goes up to 45 g/d. Thus, if it is desirable to promote the use of unrefined foods, the recommended dietary fiber intake should be a minimum of 15-20 g/1000 Kcal.

Psyllium-enriched cereals lower blood total cholesterol and LDL cholesterol, but not HDL cholesterol, in hypercholesterolemic adults: results of a meta-analysis

We conducted a meta-analysis to determine the effect of consumption of psyllium-enriched cereal products on blood total cholesterol (TC), LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C) levels and to estimate the magnitude of the effect among 404 adults with mild to moderate hypercholesterolemia (TC of 5.17-7.8 mmol/L) who consumed a low fat diet. Studies of psyllium cereals were identified by a computerized search of MEDLINE and Current Contents and by contacting United States-based food companies involved in psyllium research. Published and unpublished studies were reviewed by one author and considered eligible for inclusion in the meta-analysis if they were conducted in humans, were randomized, controlled experiments, and included a control group that ate cereal providing </=3 g soluble fiber/d. Eight published and four unpublished studies, conducted in four countries, met the criteria. Analysis of a linear model was performed, controlling for sex and age. Female subjects were divided into two groups to provide a rough estimate of the effect of menopausal status (premenopausal = <50 y, postmenopausal = >/=50 y) on blood lipids. The meta-analysis showed that subjects who consumed a psyllium cereal had lower TC and LDL-C concentrations [differences of 0.31 mmol/L (5%) and 0.35 mmol/L (9%), respectively] than subjects who ate a control cereal; HDL-C concentrations were unaffected in subjects eating psyllium cereal. There was no effect of sex, age or menopausal status on blood lipids. Results indicate that consuming a psyllium-enriched cereal as part of a low fat diet improves the blood lipid profile of hypercholesterolemic adults over that which can be achieved with a low fat diet alone.

Intestinal fatty acid-binding protein variation associated with variation in the response of plasma lipoproteins to dietary fibre

Increased dietary fibre intake is a component of prudent dietary advice, although the mechanism of its beneficial effect is unclear. Furthermore, plasma lipoprotein response to dietary fibre seems to vary both between individuals and according to the type of fibre consumed. Two common genetic variants, A54 and T54, of the intestinal fatty acid-binding protein gene (FABP2) have different in vitro binding affinities for long-chain fatty acids. We have hypothesized that variation in FABP2 would be associated with interindividual variation in the response of plasma lipoproteins to either dietary soluble or insoluble fibre. We studied 43 subjects who participated in a year-long cross-over study of the effect of insoluble and soluble fibre on plasma lipoproteins. We tested for associations between FABP2 genotypes and the response of plasma lipoproteins to dietary fibre. When compared with subjects homozygous for FABP2 A54, we found that subjects with FABP2 T54 had significantly greater decreases in plasma total and low-density lipoprotein (LDL)-cholesterol and apoB during the period when the diet was high in soluble fibre than during the period when the diet was high in insoluble fibre. Furthermore, compared with subjects with the FABP2 A54 allele, subjects with the FABP2 T54 allele had significantly lower secretion of total fecal bile acids, but this did not increase with dietary soluble fibre. Genetic variation in FABP2 may thus contribute to interindividual variation in the response of plasma lipoproteins to different dietary fibres, but the mechanism does not appear to be related to increases in fecal bile acid secretion.

Apolipoprotein E R112; R251G: a carboxy-terminal variant found in patients with hyperlipidemia and coronary heart disease

A 49 year-old hypercholesterolemic male with marked electrocardiographic ST segment depression on exercise testing was found to have an apo E E3/3 phenotype by isoelectric focusing, but an APOE E4/3 genotype using HhaI restriction isotyping. DNA sequence analysis of the proband's APOE gene found a G-->C point mutation at codon 251. This predicted a change in the amino acid encoded by codon 251, from arginine to glycine. The mutation occurred on an allele that encoded arginine at position 112 and this variant was named APOE R112; R251G. The R251G change altered a recognition site for the endonuclease StuI and was the basis for a restriction isotyping method to rapidly screen for this mutation. In relatives of the proband, APOE R112; R251G was consistently found in subjects with both hyperlipidemia and atherosclerosis. Apo E R112; R251G-containing very low density lipoproteins bound normally to macrophages in vitro. However, the proband had an abnormal post-prandial lipoprotein response to a dietary fat challenge. The association of APOE R112; R251G with abnormal phenotypes suggests that the amino acid change in the carboxy-terminal, perhaps in combination with the common amino acid polymorphism at codon 112, has a functional impact upon lipoprotein metabolism in members of this family.

Small weight loss on long-term acarbose therapy with no change in dietary pattern or nutrient intake of individuals with non-insulin-dependent diabetes

OBJECTIVES

To see if the long-term treatment of non-insulin dependent diabetes (NIDDM) with the alpha-glucosidase inhibitor acarbose affects food intake and body weight.

DESIGN

Randomized, double-blind, placebo-controlled, parallel design clinical trial of 12 months duration.

SUBJECTS

Subjects with NIDDM in four treatment strata: 77 on diet alone, 83 also treated with metformin, 103 also treated with sulfonylurea and 91 also treated with insulin.

MEASUREMENTS

Two 3 day diet records were obtained before randomization to acarbose or placebo therapy, and additional 3 day diet records were obtained at 3, 6, 9 and 12 months after randomization. Body weight was also measured at these times.

RESULTS

Of the 354 subjects randomized, 279 (79%) completed at least 9 months of therapy and, of these, 263 (94%) provided at least one diet record during the baseline period and two diet records during the treatment period. After one year, subjects on acarbose had lost 0.46 +/- 0.28 kg, which differed significantly from the 0.33 +/- 0.25 kg weight gain on placebo (P = 0.027). The difference in weight change between acarbose and placebo did not differ significantly in the different treatment strata. Being in the study had significant effects on diet, including a reduction in energy intake from 1760-1700 Kcal/d (P < 0.05), a reduction in simple sugars intake from 18.5-17.4% of energy (P < 0.001), and reductions in the number of different foods consumed (33-30, P < 0.001) and the number of meals eaten per day (4.7-4.3, P < 0.001). However, compared to placebo treatment, acarbose had no effect on energy intake, nutrient intakes, or dietary patterns.

CONCLUSIONS

In subjects with NIDDM on weight-maintaining diets, long-term acarbose therapy results in a small weight loss, but has no effect on energy or nutrient intakes. The weight loss induced by acarbose may be due partly to reduced doses of concomitant oral agents and insulin and partly to energy loss due to increased colonic fermentation.

Long-term effect of soluble-fiber foods on postprandial fat metabolism in dyslipidemic subjects with apo E3 and apo E4 genotypes

To determine the long-term effect of soluble fiber on postprandial fat metabolism, we studied 33 dyslipidemic subjects, 16 with apolipoprotein (apo) E3/3 (E3) and 17 with E3/4 or E4/4 (E4) genotypes. They ate preweighed low-fat (20% of energy), high-fiber (> 5.7 g/MJ) diets for two 4-mo periods separated by a 2-mo washout period according to a randomized, crossover design. One diet contained foods rich in insoluble fiber and the other foods rich in soluble fiber. On 1 d during the last 2 wk of each diet, subjects ingested a standard, fiber-free, fatty liquid meal containing retinyl palmitate as a marker of intestinally derived lipoproteins. Plasma samples were obtained at hourly intervals for 10 h. Compared with the insoluble-fiber diet, soluble fiber reduced fasting plasma total cholesterol in both E3 (6.6 +/- 2.1%, P = 0.007)and E4 subjects (5.6 +/- 2.1%, P = 0.017). Soluble fiber increased fecal total bile acid output in both E3 (76 +/- 18%, P < 0.001) and E4 subjects (85 +/- 19%, P < 0.001). The incremental area under the chylomicron triacylglycerol response curve was significantly greater after soluble fiber than after insoluble fiber in E3 (3.56 +/- 0.56 compared with 2.87 +/- 0.38 mmol x h/L, respectively, P = 0.046) but not in E4 subjects (5.19 +/- 0.78 compared with 4.92 +/- 0.81 mmol x h/L). Kinetic analysis suggested an increase in retinyl palmitate absorption in E3 subjects after soluble fiber, but no difference in E4 subjects. These results suggest that a long-term increase in dietary soluble fiber has no effect on postprandial fat metabolism in subjects with an apo E3/4 or E4/4 genotype. However, soluble fiber enhances apparent fat absorption in E3 subjects, which could be due to an increased bile acid pool and increased micelle formation.

Time of day and glucose tolerance status affect serum short-chain fatty acid concentrations in humans

Short-chain fatty acids (SCFA) are derived from endogenous (metabolism of fat, carbohydrate, and amino acids) and exogenous (colonic fermentation) sources. To see how time of day and glucose tolerance status influenced serum SCFA concentrations, we determined serum SCFA throughout the day in 22 subjects with impaired glucose tolerance (IGT) and 10 young and eight middle-aged normal controls. On 1 day, insulin sensitivity was assessed as the steady-state plasma glucose (SSPG) level achieved during intravenous infusion of glucose insulin, and somatostatin. On another day, plasma glucose and insulin and serum SCFA levels were measured 12 times over 12 hours with subjects eating a standard diet. SSPG in young controls (5.5 +/- 1.1 mmol/L) was less than in middle-aged controls (9.3 +/- 1.6 mmol/L), which in turn was less than in IGT subjects (13.7 +/- 0.6 mmol/L; P < .01). Mean plasma glucose in IGT subjects was greater than in normal controls, and mean plasma insulin in IGT subjects was higher than in young controls but similar to the levels in middle-aged controls. Mean 12-hour serum acetate in young controls (143 +/- 13 mumol/L) was greater than in middle-aged controls (104 +/- 11 mumol/L) and IGT subjects (113 +/- 5 mumol/L; P < .05). Mean 12-hour serum propionate in young controls (3.8 +/- 0.5 mumol/L) was less than in IGT subjects (5.4 +/- 0.3 mumol/L; P < .01), with middle-aged controls being intermediate (4.6 +/- 0.3 mumol/L). Both young (1.6 +/- 0.3 mumol/L) and middle-aged (1.0 +/- 0.2) controls had lower mean butyrate than IGT subjects (3.1 +/- 0.4 mumol/L; P < .05). Levels of all three SCFA varied significantly during the day, tending to decrease after breakfast and increase transiently after lunch and dinner. It is concluded that both time of day and glucose tolerance status affect serum SCFA levels in nondiabetic humans. The results suggest that serum acetate is derived primarily from colonic fermentation, serum butyrate primarily from endogenous fatty acid metabolism, and serum propionate from both exogenous and endogenous sources.

Effect of a diet high in vegetables, fruit, and nuts on serum lipids

We assessed the effect of a diet high in leafy and green vegetables, fruit, and nuts on serum lipid risk factors for cardiovascular disease. Ten healthy volunteers (seven men and three women aged 33 +/- 4 years [mean +/- SEM]; body mass index, 23 +/- 1 kg/m2) consumed their habitual diet (control diet, 29% +/- 2% fat calories) and a diet consisting largely of leafy and other low-calorie vegetables, fruit, and nuts (vegetable diet, 25% +/- 3% fat calories) for two 2-week periods in a randomized crossover design. After 2 weeks on the vegetable diet, lipid risk factors for cardiovascular disease were significantly reduced by comparison with the control diet (low-density lipoprotein [LDL] cholesterol, 33% +/- 4%, P < .001; ratio of total to high-density lipoprotein [HDL] cholesterol, 21% +/- 4%, P < .001; apolipoprotein [apo] B:A-I, 23% +/- 2%, P < .001; and lipoprotein (a) [Lp(a)], 24% +/- 9%, P = .031). The reduction in apo B was related to increased intakes of soluble fiber (r = .84, P = .003) and vegetable protein (r = -.65, P = .041). On the vegetable compared with the control diet, the reduction in total serum cholesterol was 34% to 49% greater than would be predicted by differences in dietary fat and cholesterol. A diet consisting largely of low-calorie vegetables and fruit and nuts markedly reduced lipid risk factors for cardiovascular disease. Several aspects of such diets, which may have been consumed early in human evolution, have implications for cardiovascular disease prevention.