A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED)

OBJECTIVES

We investigated whether a Mediterranean-style diet (MedDiet) supplemented with fish oil can improve mental health in adults suffering depression.

METHODS

Adults with self-reported depression were randomized to receive fortnightly food hampers and MedDiet cooking workshops for 3 months and fish oil supplements for 6 months, or attend social groups fortnightly for 3 months. Assessments at baseline, 3 and 6 months included mental health, quality of life (QoL) and dietary questionnaires, and blood samples for erythrocyte fatty acid analysis.

RESULTS

n = 152 eligible adults aged 18-65 were recruited (n = 95 completed 3-month and n = 85 completed 6-month assessments). At 3 months, the MedDiet group had a higher MedDiet score (t = 3.95, P < 0.01), consumed more vegetables (t = 3.95, P < 0.01), fruit (t = 2.10, P = 0.04), nuts (t = 2.29, P = 0.02), legumes (t = 2.41, P = 0.02) wholegrains (t = 2.63, P = 0.01), and vegetable diversity (t = 3.27, P < 0.01); less unhealthy snacks (t = -2.10, P = 0.04) and red meat/chicken (t = -2.13, P = 0.04). The MedDiet group had greater reduction in depression (t = -2.24, P = 0.03) and improved mental health QoL scores (t = 2.10, P = 0.04) at 3 months. Improved diet and mental health were sustained at 6 months. Reduced depression was correlated with an increased MedDiet score (r = -0.298, P = 0.01), nuts (r = -0.264, P = 0.01), and vegetable diversity (r = -0.303, P = 0.01). Other mental health improvements had similar correlations, most notably for increased vegetable diversity and legumes. There were some correlations between increased omega-3, decreased omega-6 and improved mental health.

DISCUSSION

This is one of the first randomized controlled trials to show that healthy dietary changes are achievable and, supplemented with fish oil, can improve mental health in people with depression.

Plasma phospholipid and dietary fatty acids as predictors of type 2 diabetes: interpreting the role of linoleic acid

BACKGROUND

Dietary fatty acids may be associated with diabetes but are difficult to measure accurately.

OBJECTIVE

We aimed to investigate the associations of fatty acids in plasma and diet with diabetes incidence.

DESIGN

This was a prospective case-cohort study of 3737 adults aged 36-72 y. Fatty acid intake (/kJ) and plasma phospholipid fatty acids (%) were measured at baseline, and diabetes incidence was assessed by self-report 4 y later. Logistic regression excluding (model 1) and including (model 2) body mass index and waist-hip ratio was used to calculate odds ratios (ORs) for plasma phospholipid and dietary fatty acids.

RESULTS

In plasma phospholipid, positive associations with diabetes were seen for stearic acid [OR model 1, highest versus lowest quintile: 4.14 (95% CI: 2.65, 6.49), P for trend < 0.0001] and total saturated fatty acids [OR model 1: 3.76 (2.43, 5.81), P for trend < 0.0001], whereas an inverse association was seen for linoleic acid [OR model 1: 0.22 (0.14, 0.36), P for trend < 0.0001]. Dietary linoleic [OR model 1: 1.77 (1.19, 2.64), P for trend = 0.002], palmitic [OR model 1: 1.65 (1.12, 2.43), P for trend = 0.012], and stearic [OR model 1: 1.46 (1.00, 2.14), P for trend = 0.030] acids were positively associated with diabetes incidence before adjustment for body size. Within each quintile of linoleic acid intake, cases had lower baseline plasma phospholipid linoleic acid proportions than did controls.

CONCLUSIONS

Dietary saturated fat intake is inversely associated with diabetes risk. More research is required to determine whether linoleic acid is an appropriate dietary substitute.

Effect of resistant starch on fecal bulk and fermentation-dependent events in humans

This study investigated the effect of two diets, which differed in resistant starch (RS) concentration, on fecal bulk and fermentation-dependent events in 11 humans. Amounts of RS consumed were 5.0 +/- 0.4 and 39.0 +/- 3.0 g/d (mean +/- SEM) for the low- and high-RS diets, respectively. The two diets were fed for 3 wk each in a randomized crossover design. Fecal collections were made in the third week of each study period. The high-RS diet produced an increase (P < 0.01) in total fecal output (from 138 +/- 22 to 197 +/- 37 g/d) and lowered fecal pH (6.9 +/- 0.1 to 6.3 +/- 0.1). There were significant increases (P < 0.05) in the fecal concentrations and daily excretion of butyrate (+38% and +100%, respectively) and acetate (+26% and +72%, respectively) during the high-RS period. The fecal excretion (g/d) of nonstarch polysaccharides (NSP) also rose by 50% during the high-RS diet, suggesting that the presence of starch in the colon may affect the fermentation of NSP. Subjects reported an increase in flatulence and easier defecation. These results demonstrate that RS has a significant impact on putative markers of colonic health in humans.

Resistant starch lowers fecal concentrations of ammonia and phenols in humans

We investigated the effect of resistant starch (RS) on markers of colonic protein metabolism. Eleven subjects participated in a randomized crossover study in which they consumed either high-RS (39 +/- 3 g/d, -chi +/- SEM) or low-RS (5 +/- 0.4 g/d) diets for 3 wk. All other macronutrients were kept constant. During the high-RS diet daily excretion of fecal nitrogen increased from 1.84 +/- 0.15 to 2.86 +/- 0.42 g/d (P < 0.01) and excretion of fecal phenols fell from 9.2 +/- 1.4 to 5.3 +/- 0.8 mg/d (P < 0.01). Fecal concentrations of ammonia decreased from 397 +/- 33 to 278 +/- 49 microgram/g (P < 0.01) and phenols decreased from 69 +/- 8 to 39 +/- 10 microgram/g (P < 0.001). Daily output of urinary ammonia, urea, phenols, and total nitrogen did not change significantly, but pH decreased from 6.4 +/- 0.1 to 6.2 +/- 0.1 (P < 0.05) during the high-RS period. These results suggest that RS significantly attenuates the accumulation of potentially harmful byproducts of protein fermentation in the human colon.

Glucose tolerance and insulin sensitivity in ponies and Standardbred horses

The existence of an innate insulin insensitivity in ponies was investigated and compared with the situation in larger breeds of horse. Ponies that were fat or had previously suffered laminitis were found to be far more intolerant to oral glucose loading (1 g/kg bodyweight [bwt]) than normal ponies or Standardbreds. These ponies also exhibited a far greater response in plasma insulin levels after glucose loading. Insulin response tests (0.4 iu/kg bwt insulin intravenously) showed only a minimal and very protracted response in both the fat and laminitic groups. The relevance of these findings in regulation of carbohydrate and lipid metabolism, and their role in the pathogenesis of hyperlipaemia, are discussed.

Marked improvement in carbohydrate and lipid metabolism in diabetic Australian aborigines after temporary reversion to traditional lifestyle

The rationale for the present study was that temporarily reversing the urbanization process in diabetic Aborigines should improve all aspects of their carbohydrate and lipid metabolism that are linked to insulin resistance. Ten full-blood, diabetic Aborigines from the Mowanjum Community (Derby, Western Australia) agreed to be tested before and after living for 7 wk as hunter-gatherers in their traditional country in north-western Australia. They were middle aged (53.9 +/- 1.8 yr) and overweight (81.9 +/- 3.4 kg), and all lost weight steadily over the 7-wk period (average, 8 kg). A detailed analysis of food intake over 2 wk revealed a low-energy intake (1200 kcal/person/day). Despite the high contribution of animal food to the total energy intake (64%), the diet was low in total fat (13%) due to the very low fat content of wild animals. Oral glucose tolerance tests (75 g glucose) were conducted in the urban setting and repeated at the end of 7 wk of traditional lifestyle. The marked improvement in glucose was due to both a fall in fasting glucose (11.6 +/- 1.2 mM before, 6.6 +/- 0.8 mM after) and an improvement in postprandial glucose clearance (incremental area under the glucose curve: 15.0 +/- 1.2 mmol/L/h before, 11.7 +/- 1.2 mmol/L/h after). Fasting plasma insulin concentration fell (23 +/- 2 mU/L before, 12 +/- 1 mU/L after) and the insulin response to glucose improved (incremental area under the insulin curve: 61 +/- 18 mU/L/h before, 104 +/- 21 mU/L/h after). The marked fall in fasting plasma triglycerides (4.0 +/- 0.5 mM before, 1.2 +/- 0.1 mM after) was due largely to the fall in VLDL triglyceride concentration (2.31 +/- 0.31 mM before, 0.20 +/- 0.03 mM after.(ABSTRACT TRUNCATED AT 250 WORDS)

Arabinoxylan fibre improves metabolic control in people with Type II diabetes

OBJECTIVE

To determine whether diet supplementation with arabinoxylan-rich (AX)-fibre from wheat improves glycaemic control in Type II diabetes.

DESIGN

Randomized, crossover intervention trial.

SETTING

Monash Medical Centre.

SUBJECTS

A total of 15 subjects with Type II diabetes.

INTERVENTIONS

Over two 5-week periods, subjects supplemented their usual diet with control bread and muffins (50% whole wheat, 50% white flour) (control diet) or with AX-bread and muffins (50% whole wheat, 36% white flour, 14% AX fibre) (AX diet). Subjects completed a 7-day food diary. At 0 and 5 weeks, venous blood was collected for determination of fasting and 2 h glucose, insulin, fructosamine and blood lipids. Blood pressure, body weight and body fat were also determined. A 24 h faecal sample, from 12 subjects, was weighed and analysed for faecal polysaccharide as a marker for dietary compliance.

RESULTS

Control and AX diets were similar except the AX diet supplied an additional 15.1 (12.0-18.5) (mean (95% confidence intervals)) g/day dietary fibre (P=0.000). Consumption of the AX diet increased faecal output by 61.5 (0.2-122.8) g/day (P=0.05) on a wet weight basis and significantly lowered fasting and 2 h plasma glucose, 2 h insulin and serum fructosamine (P=0.002, 0.000, 0.015, and 0.02, respectively). Blood lipids, body weight, fat mass and blood pressure remained unchanged.

CONCLUSION

A supplement of 15 g/day of AX-rich fibre can significantly improve glycaemic control in people with Type II diabetes.

Factors affecting the rate of hydrolysis of starch in food

After accurate determination of the content of available carbohydrate in a wide variety of cereals, as in vitro method was used to study factors that influence hydrolysis rates of starch in foods. Fiber, physical form, cooking, and the possible presence of a natural amylase inhibitor were all shown to affect hydrolysis rates of starch. Fiber only exerted an inhibiting effect on the rate of hydrolysis when it formed a physical barrier to limit access of the hydrolytic enzymes to the starch (as in whole brown rice, for example). Particle size played an important role in determining the rate of hydrolysis. Cooking made the starch much more readily available for enzymic hydrolysis presumably by gelatinizing it. Stoneground wholemeal flour was hydrolyzed more slowly than white flour. This is consistent with the presence of a natural amylase inhibitor that has been isolated from wheat germ in the whole grain. Our results suggest that such amylase inhibitor activity is destroyed by passage through the roller mill, since the starch in wheat germ and standard wholemeal flour (i.e., not stoneground but reconstituted after passage through the roller mill) was hydrolyzed at a rate identical to white flour.

Arabinoxylan fiber, a byproduct of wheat flour processing, reduces the postprandial glucose response in normoglycemic subjects

BACKGROUND

Arabinoxylan (AX) is the major component of dietary fiber in the cereal grains that make up a large proportion of our diet. However, the physiologic effect of AX is unknown.

OBJECTIVE

The objective of this study was to determine whether AX improves postprandial glucose and insulin responses in healthy humans.

DESIGN

AX-rich fiber was extracted from the byproduct of wheat-flour processing. Three isoenergic breakfasts, comprising bread, margarine, and jam, had 75 g available carbohydrate, 10 g protein, and 14 g fat and contained 0, 6, and 12 g AX-rich fiber, respectively. Fourteen healthy subjects consumed the 3 breakfast meals in random order on 3 mornings >/=3 d apart after an overnight fast. Blood was taken from the subjects at regular intervals over 2 h and was analyzed for glucose and insulin. The palatability of bread containing AX-rich fiber was compared with that of a control bread.

RESULTS

Compared with the control meal containing 0 g AX-rich fiber, the peak postprandial glucose concentration after meals containing 6 and 12 g AX-rich fiber was significantly lower (6. 3 +/- 1.3 compared with 7.2 +/- 1.0 mmol/L, P < 0.01; 5.9 +/- 0.9 compared with 7.2 +/- 1.0 mmol/L, P < 0.001, respectively). The incremental area under the curve (IAUC) for glucose was 20.2% (95% CI: 5.8%, 34.7%; P < 0.01) and 41.4% (25.9%, 56.8%; P < 0.001) lower, whereas IAUC for insulin was 17.0% (2.0%, 32.1%; P < 0.05) and 32. 7% (18.8%, 46.6%; P < 0.001) lower, respectively. Bread containing AX-rich fiber was as pala as 50% whole-wheat bread when evaluated with sensory analysis by 30 volunteers.

CONCLUSIONS

Postprandial glucose and insulin responses were improved by ingestion of AX-rich fiber. Further research is required to determine whether AX-rich fiber is of benefit to people with type 2 diabetes.

Effectiveness of a community-directed 'healthy lifestyle' program in a remote Australian aboriginal community

OBJECTIVE

To assess the sustainability and effectiveness of a community-directed program for primary and secondary prevention of obesity, diabetes and cardiovascular disease in an Aboriginal community in north-west Western Australia.

METHOD

Evaluation of health outcomes (body mass index, glucose tolerance, and plasma insulin and triglyceride concentrations) in a cohort of high-risk individuals (n = 49, followed over two years) and cross-sectional community samples (n = 200 at baseline, 185 at two-year and 132 at four-year follow-ups), process (interventions and their implementation) and impact (diet and exercise behaviour).

RESULTS

For the high-risk cohort, involvement in diet and/or exercise strategies was associated with protection from increases in plasma glucose and triglycerides seen in a comparison group; however, sustained weight loss was not achieved. At the community level, significant reductions were observed in fasting insulin concentration but no change in prevalence of diabetes, overweight or obesity. Weight gain remained a problem among younger people. Sustainable improvements were observed for dietary intake and level of physical activity. These changes were related to supportive policies implemented by the community council and store management.

CONCLUSIONS

Community control and ownership enabled embedding and sustainability of program, in association with social environmental policy changes and long-term improvements in important risk factors for chronic disease.

IMPLICATIONS

Developmental initiatives facilitating planning, implementation and ownership of interventions by community members and organisations can be a feasible and effective way to achieve sustainable improvements in health behaviours and selected health outcomes among Aboriginal people.

Determinants of restenosis and lack of effect of dietary supplementation with eicosapentaenoic acid on the incidence of coronary artery restenosis after angioplasty

The effect of an eicosapentaenoic acid-rich encapsulated preparation of fish oil on the incidence of early restenosis after coronary angioplasty was assessed by a randomized double-blind placebo-controlled study. A total of 108 patients received either 10 capsules of fish oil (1.8 g eicosapentaenoic acid, 1.2 g docosahexaenoic acid) or 10 control capsules (50% olive oil, 50% corn oil), commencing the day before angioplasty and continuing for 4 months after angioplasty, in addition to treatment with aspirin and verapamil. In 101 (94%) of the 108 patients, follow-up angiographic or postmortem result was evaluated at a mean (+/- SD) of 100 (+/- 22) days. Angiographic restenosis was observed in 34% of patients (29% of lesions) in the fish oil-treated group and 33% of patients (31% of lesions) in the control group (no significant difference). The overall incidence of angiographic restenosis was significantly higher in patients with 1) recurrent angina pectoris, 2) a positive exercise test at follow-up after angioplasty, 3) residual stenosis greater than 30% immediately after angioplasty, and 4) dilation of the left anterior descending or right coronary artery. Biochemical investigations showed a greater decrease in the serum triglyceride levels in the fish oil-treated group versus the control group (p less than 0.05) but no differences between the two groups in cholesterol levels or platelet counts over the 4 month period. In conclusion, in this study, the administration of fish oil at a dose of 10 capsules/day did not reduce the incidence of early restenosis after coronary angioplasty.

The influence of the type of dietary fat on postprandial fat oxidation rates: monounsaturated (olive oil) vs saturated fat (cream)

OBJECTIVE

To compare postprandial whole-body fat oxidation rates in humans, following high-fat (43% of total energy) mixed breakfast meals, of fixed energy and macronutrient composition, rich in either monounsaturated fat (MUFA) from extra virgin olive oil or saturated fat (SFA) from cream.

DESIGN

Paired comparison of resting metabolic rate (RMR), thermic effect of a meal and substrate oxidation rates following consumption of isocaloric breakfast meals, differing only in the type of fat, administered in random order 1-2 weeks apart.

SUBJECTS

Fourteen male volunteers, body mass index (BMI) in the range 20-32 kg/m(2), aged 24-49 y and resident in Melbourne, Australia, were recruited by advertisement in the local media or by personal contact.

MEASUREMENTS

Body size and composition was determined by anthropometry and dual energy X-ray absorptiometry (DEXA). Indirect calorimetry was used to measure RMR, thermic effect of a meal, post-meal total energy expenditure and substrate oxidation rate. Blood pressure and pulse rates were measured with an automated oscillometric system. Fasting and 2 h postprandial glucose and insulin concentrations and the fasting lipid profile were also determined.

RESULTS

In the 5 h following the MUFA breakfast, there was a significantly greater postprandial fat oxidation rate (3.08+/-4.58 g/5 h, P=0.017), and lower postprandial carbohydrate oxidation rate (P=0.025), than after the SFA breakfast. Thermic effect of a meal was significantly higher (55 kJ/5 h, P=0.034) after the MUFA breakfast, in subjects with a high waist circumference (HWC > or = 99 cm) than those with a low waist circumference (LWC<99 cm). This difference was not detected following the SFA breakfast (P=0.910).

CONCLUSION

If postprandial fat oxidation rates are higher after high MUFA, rather than SFA meals, then a simple change to the type of dietary fat consumed might have beneficial effects in curbing weight gain in men consuming a relatively high-fat diet. This may be particularly evident in men with a large waist circumference.

Noradrenaline turnover during under- and over-eating in normal weight subjects

Adjustments to sympathetic nervous system activity may regulate constant body weight despite wide variations in energy intake. To test this six normal weight subjects were studied at three different energy intakes (low, weight maintaining and high). Noradrenaline turnover was measured on the tenth day of each diet. Both noradrenaline appearance rate and noradrenaline clearance increased significantly with increasing energy intake and were a more sensitive indices than the plasma noradrenaline concentrations which rose, but not significantly. Fasting triiodothyronine (T3) rose and reverse T3 fell with increasing energy intake, while thyroxine (T4) concentrations did not change. Systolic blood pressure also rose significantly. Underfeeding resulted in reductions in noradrenaline appearance and clearance rates and in the T3 level. These results demonstrate that sympathetic nervous system activity, as determined by noradrenaline turnover in plasma, varies in response to short-term changes in energy intake in normal weight subjects. These changes may partly explain why some individuals maintain body weight constant despite large differences in food intake. The present findings may also be relevant to the variability in susceptibility to become obese.

Substitution of saturated with monounsaturated fat in a 4-week diet affects body weight and composition of overweight and obese men

A randomised crossover study of eight overweight or obese men (aged 24-49 years, BMI 25.5-31.3 kg/m(2)), who followed two diets for 4 weeks each, was performed to determine whether substitution of saturated fat with monounsaturated fat affects body weight and composition. Subjects were provided with all food and beverages as modules (selected ad libitum) of constant macronutrient composition, but differing energy content. The % total energy from saturated fat, monounsaturated fat and polyunsaturated fat was 24, 13 and 3 % respectively on the saturated fatty acid (SFA)-rich diet and 11, 22 and 7 % respectively on the monounsaturated fatty acid (MUFA)-rich diet. MUFA accounted for about 80 % of the unsaturated fats consumed on both diets. Body composition, blood pressure, energy expenditure (resting and postprandial metabolic rates, substrate oxidation rate, physical activity), serum lipids, the fatty acid profile of serum cholesteryl esters and plasma glucose and insulin concentrations were measured before and after each diet period. Significant (P< or =0.05) differences in total cholesterol and the fatty acid composition of serum cholesteryl esters provided evidence of dietary adherence. The men had a lower weight (-2.1 (SE 0.4) kg, P=0.0015) and fat mass (-2.6 (SE 0.6) kg, P=0.0034) at the end of the MUFA-rich diet as compared with values at the end of the SFA-rich diet. No significant differences were detected in energy or fat intake, energy expenditure, substrate oxidation rates or self-reported physical activity. Substituting dietary saturated with unsaturated fat, predominantly MUFA, can induce a small but significant loss of body weight and fat mass without a significant change in total energy or fat intake.

Rate of starch hydrolysis in vitro as a predictor of metabolic responses to complex carbohydrate in vivo

This study was designed to determine whether the rate of hydrolysis of different starches by pancreatic amylase in vitro was proportional to the postprandial glucose and insulin response to those starches after oral ingestion. Lean young men consumed four test meals of rice containing 75 g starch: white rice, unpolished (brown) rice, ground white rice, and ground brown rice. Postprandial glucose and insulin responses were measured over 4 h and showed the following pattern: ground white rice congruent to ground brown rice greater than white rice greater than brown rice. The maximum increases in blood glucose after the four meals were brown rice 0.9 mM, white rice 1.5 mM, ground brown rice 3.3 mM, and ground white rice 3.6 mM. Samples of the cooked rices were incubated in vitro with pancreatic amylase for 30 min and the percentage starch hydrolysis determine. The relative rates of starch hydrolysis correlated very closely with the peak glucose responses: brown rice 17.6%, white rice 30.8%, ground brown rice 68.2% and ground white rice 71.8%. These results indicated that the rate of intestinal hydrolysis of starch is an extremely important determinant of the metabolic responses to a particular starch. The rate of starch hydrolysis can be determine simply by an in vitro method and should assist the design of diets for the treatment of diabetes.

Can the Mediterranean diet lower HbA1c in type 2 diabetes? Results from a randomized cross-over study

BACKGROUND AND AIMS

To investigate the impact of a diet modeled on the traditional Cretan Mediterranean diet on metabolic control and vascular risk in type 2 diabetes.

METHODS AND RESULTS

Twenty-seven subjects (47-77 yrs) with type 2 diabetes were randomly assigned to consume either the intervention diet ad libitum or their usual diet for 12 weeks and then cross over to the alternate diet. Most of the meals and staple foods for the intervention diet were provided. Lipids, glycemic variables, blood pressure, homocysteine, C-reactive protein, plasma carotenoids and body composition (anthropometry and dual energy X-ray absorptiometry) were assessed at baseline, and at the end of both diet periods. Dietary adherence was monitored using plasma carotenoid and fatty acid (FA) analysis, complemented by diet diaries. Compared with usual diet, on the ad libitum Mediterranean intervention diet glycosylated haemoglobin fell from 7.1% (95% CI: 6.5-7.7) to 6.8% (95% CI: 6.3-7.3) (p=0.012) and diet quality improved significantly [plant:animal (g/day) food ratio increased from 1.3 (95% CI: 1.1-1.5) to 5.4 (95% CI: 4.3-6.6) (p<0.001)], plasma lycopene and lutein/zeaxanthin increased (36% and 25%, respectively), plasma saturated and trans FAs decreased, and monounsaturated FAs increased.

CONCLUSION

A traditional moderate-fat Mediterranean diet improves glycemic control and diet quality in men and women with well-controlled type 2 diabetes, without adverse effects on weight.

Is there evidence for an age-related reduction in metabolic rate?

To determine whether the age-related reduction in basal metabolic rate (BMR) is explained by a quantitative and/or qualitative change in the components of lean tissue, we conducted a cross-sectional study in groups of young (n = 38, 18-35 yr) and older (n = 24, 50-77 yr) healthy individuals. BMR was measured by indirect calorimetry. Body composition was obtained by using dual-energy X-ray absorptiometry (DEXA), which permitted four compartments to be quantified [bone mineral mass, fat mass (FM), appendicular lean tissue mass (ALTM), and nonappendicular lean tissue mass (NALTM)]. Absolute BMR and ALTM were lower, whereas FM was significantly higher in the older, compared with young, subjects. BMR, adjusted for differences in FM, ALTM, and NALTM, was significantly lower in the older subjects by 644 kJ/day. In separate regression analyses of BMR on body compartments, older subjects had significantly lower regression coefficients for ALTM and NALTM, compared with young subjects. Hence, the age-related decline in BMR is partly explained by a reduction in the quantity, as well as the metabolic activity, of DEXA-derived lean tissue components.

A comparison of the effects of beef, chicken and fish protein on satiety and amino acid profiles in lean male subjects

We compared postprandial satiety and plasma amino acid, insulin, and glucose concentrations in six lean male subjects after the ingestion of three types of protein (beef, chicken and fish). Satiety was greater after the fish meal (P less than 0.01). The observed difference in satiety could be correlated with two of the putative satiety signals measured in this study: 1) serotoninergic activity, due to differences observed in the postprandial tryptophan to large neutral amino acid ratio; and 2) digestibility, reflected in the significantly (P less than 0.05) longer time it took for the plasma amino acid concentrations to peak after the fish meal. Correlations between dietary and plasma amino acid concentrations were determined and good correlations (r = 0.90) were observed for essential amino acids other than lysine and tryptophan. There were no differences in insulin or glucose concentrations in subjects after consuming each of the three meals. Whether other differences that we observed, such as increased concentrations of taurine and methionine following the fish meal, had any effect on satiety or were of biological significance is not known.

The effect of coingestion of fat on the glucose, insulin, and gastric inhibitory polypeptide responses to carbohydrate and protein

In the present study we examined the effect of coingestion of 50 g fat (butter) on the postprandial glucose, insulin, and gastric inhibitory polypeptide responses to 50 g carbohydrate (potato) or 50 g protein (low fat veal) in eight normal subjects. The coingestion of fat with either carbohydrate or protein resulted in greatly increased gastric inhibitory polypeptide responses, the effect being more pronounced with carbohydrate. The addition of fat to a carbohydrate meal also reduced the postprandial glucose response. This could have been due to several factors including a delayed glucose absorption, secondary to a fat-induced inhibition of gastric emptying. However, despite the lower blood glucose levels in the presence of fat the insulin response was not reduced, suggesting a potentiation of insulin secretion in the presence of fat. Thus, despite the apparent improvement in glucose tolerance when carbohydrate is ingested together with fat, the accompanying potentiation of insulin secretion could form the basis of long-term changes in insulin sensitivity which accompany alterations in dietary fat intake.

Plasma phospholipid fatty acid composition as a biomarker of habitual dietary fat intake in an ethnically diverse cohort

BACKGROUND AND AIM

As an evaluation of fatty acid intake measurement, our aim was to examine associations between diet and plasma phospholipid (PL) fatty acids, and whether these were modified by age, sex, country of birth, fasting status, use of cholesterol-lowering medication, body size, chronic disease and other lifestyle factors.

METHODS AND RESULTS

Cross-sectional analysis of plasma PL fatty acid composition and dietary fatty acid intake over 12 months from a 121-item food frequency questionnaire (FFQ) in 4439 men and women aged 40-69 years, born in Australia, Greece or Italy. Crude correlation coefficients ranged from 0.18 to 0.40; and corrected correlation coefficients from 0.38 to 0.78 for total monounsaturated, polyunsaturated, n-6, n-3 fatty acids, oleic acid, linoleic acid, EPA and DHA. Weaker associations were observed for other fatty acids. The associations did not vary significantly by fasting status, use of lipid lowering medication or alcohol intake, but for some fatty acids did vary by sex, age, body mass index, country of birth, smoking and previous heart attack or diabetes.

CONCLUSIONS

The FFQ provides useful information on intakes of mono- and polyunsaturated fatty acids. Correlations did not differ by fasting status, or use of lipid-lowering medication.

Westernisation, insulin resistance and diabetes in Australian aborigines

OBJECTIVE

To examine the published data on the impact of westernisation on obesity, non-insulin dependent diabetes mellitus (NIDDM), and coronary heart disease (CHD) in Australian Aborigines.

DATA SOURCES

Fifty-five articles from Australian and international sources (primarily peer-reviewed journals) are cited.

STUDY SELECTION

Twenty-eight reports providing data on the diet, lifestyle, health and "lifestyle diseases" of Australian Aborigines before and after westernisation are included in this review. A further 27 articles on obesity, NIDDM, CHD, insulin resistance, and the impact of diet and exercise were used to help interpret the Aboriginal data.

DATA EXTRACTION

Information on dietary composition, anthropometry, disease and risk factor prevalence, and relevant biochemical measurements were used for comparative and interpretive purposes.

DATA SYNTHESIS

The traditional hunter-gatherer lifestyle of Australian Aborigines, characterised by high physical activity and a diet of low energy density (low fat, high fibre), promoted the maintenance of a very lean body weight and minimised insulin resistance. In contrast, for most Aborigines a Western lifestyle is characterised by reduced physical activity and an energy-dense diet (high in refined carbohydrate and fat) which promotes obesity and maximises insulin resistance. When they make the transition from their traditional hunter-gatherer lifestyle to a westernised lifestyle, Aborigines develop high prevalence rates for obesity (with an android pattern of fat distribution), non-insulin dependent diabetes, impaired glucose tolerance, hypertriglyceridaemia, hypertension and hyperinsulinaemia. The striking improvements in carbohydrate and lipid metabolism in diabetic and non-diabetic Aborigines after a temporary reversion to a traditional hunter-gatherer lifestyle highlight the potentially reversible nature of the detrimental effects of lifestyle change, particularly in young people who have not yet developed diabetes.

CONCLUSION

It is suggested that insulin resistance was important to the survival of Aborigines as hunter-gatherers, but is also the underlying metabolic characteristic predisposing them to obesity, NIDDM and CHD after westernisation. Intervention strategies to prevent chronic diseases related to insulin resistance should be directed at lifestyle modification. To be effective such programmes will have to be developed and implemented at the community level.

Effect of co-ingestion of fat on the metabolic responses to slowly and rapidly absorbed carbohydrates

The present study examined the acute effects of co-ingestion of fat (37.5 g) on the post-prandial metabolic responses to 75 g of carbohydrate which was either slowly absorbed (lentils) or rapidly absorbed (potatoes). Co-ingestion of fat resulted in a significant flattening of the post-prandial glucose curves, the effect being more pronounced for the rapidly absorbed potatoes. This was probably due to delayed gastric emptying. However, the post-prandial insulin responses to either carbohydrate were not significantly reduced by fat, suggesting that the insulin response to a given glucose concentration was potentiated in the presence of fat. The gastric inhibitory polypeptide (GIP) responses to both carbohydrates were greatly increased in the presence of fat. To investigate further the possible roles of GIP in the entero-insular axis, a 5-g bolus of glucose was injected intravenously 1 h after lentils +/- fat. This was sufficient to raise the glucose levels above the threshold reported for GIP to potentiate insulin secretion. However, despite the large differences in circulating GIP levels, the insulin response to glucose was not affected by the presence of fat. These results suggest that (1) the rate of absorption of carbohydrate is a major determinant of post-prandial metabolic responses even in the presence of fat, (2) fat-stimulated GIP secretion does not potentiate glucose-induced insulin secretion, and (3) the potentiation of the insulin response to glucose when carbohydrate is co-ingested with fat is consistent with the well-documented insulin resistance associated with high fat diets.

Measurement of resistant starch: factors affecting the amount of starch escaping digestion in vitro

We developed an in vitro assay system that mimics the physiological conditions for starch digestion. In this system all undigested starch was termed resistant starch (RS). The richest sources of RS were firm bananas and roasted chickpeas. Different food-processing techniques produced different amounts of RS. RS in uncooked oats (0.161 g/g dry wt) and firm bananas (0.247 g/g dry wt) was reduced by cooking to 0.028 and 0.032 g/g dry wt, respectively. Cooling boiled potato overnight at 4 degrees C produced a 2.8-fold increase in the amounts of RS. Whole rice contained more RS than did ground rice whereas grinding did not affect amounts of RS in roasted chickpeas. Amounts of RS in food decreased with increased chewing, indicating that chewing can also affect the amount of starch escaping digestion. This assay may be useful in predicting which foods and processing techniques result in high amounts of starch escaping digestion in the small intestine.