The effect of protein or carbohydrate breakfasts on subsequent plasma amino acid levels, satiety and nutrient selection in normal males

Trimethylamine N-oxide, β-alanine, tryptophan index, and vitamin B6-related dietary patterns in association with stroke risk

BACKGROUND AND AIMS

The aim of this study was to examine the associations of dietary patterns derived by reduced-rank regression (RRR) model reflecting variation in novel biomarkers (trimethylamine N-oxide, β-alanine, tryptophan index, and vitamin B6) with stroke risk.

METHODS AND RESULTS

We performed analyses based on a community-based cohort study "the Prospective Follow-up Study on Cardiovascular Morbidity and Mortality in China (PFS-CMMC)". Factor loadings were calculated by RRR using 11 food groups collected via a validated food frequency questionnaire and the four response variables based on its nested case-control data (393 cases of stroke vs. 393 matched controls). Dietary pattern scores were derived by applying the factor loadings to the food groups in the entire cohort (n = 15,518). The associations of dietary pattern with the stroke risk were assessed using Cox proportional hazards models. The dietary pattern characterized with higher intakes of red meat and poultry but lower intakes of fresh vegetables, fresh fruits, and fish/seafoods were identified for further analyses. The hazard ratios (HR) for the highest vs. lowest quartile was 1.55 [95 % confidence interval (CI): 1.18-2.03, P trend = 0.001] for total stroke, 2.96 [95 % CI: 1.53-5.71, P trend <0.001] for non-ischemic stroke, after adjustment for sex, age, educational attainment, current smoking, current drinking, body mass index, total energy intake, family history of stroke, hypertension, diabetes, hyperlipidemia, and estimated glomerular filtration rate.

CONCLUSION

Our findings highlight the importance of limited meat intake and increased intakes of fresh vegetables, fruits, and fish/seafoods in the prevention of stroke among Chinese adults.

Association of inflammation biomarkers with food cravings and appetite changes across the menstrual cycle

IMPORTANCE

Premenstrual symptoms, including food cravings, are often a regular complaint among menstruating women. However, existing evidence regarding the biological mechanisms by which these food cravings occur remains unclear. Inflammation may play an essential role in the occurrence of these food cravings before menstruation.

OBJECTIVE

The purpose of the present study was to examine the associations between inflammatory markers and the risk of moderate/severe food cravings while accounting for changes in hormone levels and stress across the menstrual cycle.

DESIGN, SETTING, AND PARTICIPANTS

The BioCycle Study followed women (n = 259) aged 18-44 for two menstrual cycles. Food cravings (via questionnaire) were assessed up to four times per cycle. Each assessment corresponded to menses and mid-follicular, ovulation, and luteal phases of the menstrual cycle. A wide range of cytokine and chemokine levels (hsCRP, GCSF, GMCSF, IL-4, IL-6, RANTES, MIP1B, etc.) were assessed in blood samples collected at up to 8 visits per cycle, with visits timed using fertility monitors.

MAIN OUTCOMES AND MEASURES

Cravings for chocolate, sweets, salty, and other foods, and changes in appetite were determined to estimate the odds of moderate or severe cravings. Associations between inflammatory markers and risk of reporting a moderate/severe craving symptom at each cycle visit was determined using weighted generalized linear models (e.g., marginal structural models). Models were adjusted for age, BMI, and race, as well as time-varying covariates such as estradiol, stress, leptin, and total energy intake, and accounted for repeated measures (i.e., multiple cycles per woman). Both inflammatory markers and reports of cravings were modeled to account for variation at each visit.

RESULTS

An association between higher inflammatory biomarkers such as hsCRP, GCSF, GMCSF, IL-4, IL-6, RANTES, MIP, and increased risk of moderate/severe cravings were identified across the menstrual cycle all risk ratio>1, all CIs range 0.71-2.38. hsCRP retained statistical significance after false discovery rate correction with chocolate, sweet, and salty cravings, while GCSF, GMCSF, IL-6, and RANTES retained significance with chocolate and sweet cravings only.

CONCLUSION

and Relevance: The results suggest a potential role of inflammation in food cravings and appetite changes across the menstrual cycle.

Association of Inflammation Biomarkers with Food Cravings and Appetite Changes Across the Menstrual Cycle

Background

Premenstrual symptoms, including food cravings, are often a regular complaint among menstruating women. However, existing evidence regarding the biological mechanisms by which these food cravings occur remains unclear. Inflammation may play an essential role in the occurence of these food cravings before menstruation.

Purpose

The purpose of the present study was to examine the associations between inflammatory markers and the risk of moderate/severe food cravings while accounting for changes in hormone levels and stress across the menstrual cycle.

Methods

The BioCycle Study followed women (n=259) aged 18-44 for two menstrual cycles. Food cravings (via questionnaire) were assessed up to four times per cycle. Each assessment corresponded to menses and mid-follicular, ovulation, and luteal phases of the menstrual cycle. A wide range of cytokine and chemokine levels (hsCRP, GCSF, GMCSF, IL-4, IL-6, RANTES, MIP1B, etc.) were assessed in blood samples collected at up to 8 visits per cycle, with visits timed using fertility monitors. Cravings for chocolate, sweets, salty, and other foods, and changes in appetite were determined to estimate the odds of moderate or severe cravings. Associations between inflammatory markers and risk of reporting a moderate/severe craving symptom at each cycle visit was determined using weighted generalized linear models (e.g., marginal structural models). Models were adjusted for age, BMI, and race, as well as time-varying covariates such as estradiol, stress, leptin, and total energy intake, and accounted for repeated measures (i.e., multiple cycles per woman). Both inflammatory markers and reports of cravings were modeled to account for variation at each visit.

Results

An association between higher inflammatory biomarkers such as hsCRP, GCSF, GMCSF, IL-4, IL-6, RANTES, MIP1B, and increased risk of moderate/severe cravings were identified across the menstrual cycle |all risk ratio>0.8, all CIs range>0.7-0.9|. hsCRP retained statistical significance after false discovery rate correction with chocolate, sweet, and salty cravings, while GCSF, GMCSF, IL-6, and RANTES retained significance with chocolate and sweet cravings only.

Conclusion

The results suggest a potential role of inflammation in food cravings and appetite changes across the menstrual cycle.

Postprandial glycine as a biomarker of satiety: A dose-rising randomised control trial of whey protein in overweight women

This study aimed to identify biomarkers of appetite response, modelled using a dose-rising whey protein preload intervention. Female participants (n = 24) with body mass index (BMI) between 23 and 40 kg/m² consumed preload beverages (0 g protein water control, WC; 12.5 g low-dose protein, LP; or 50.0 g high-dose protein, HP) after an overnight fast, in a randomised cross over design. Repeated venous blood samples were collected to measure plasma biomarkers of appetite response, including glucose, glucoregulatory peptides, gut peptides, and amino acids (AAs). Appetite was assessed using Visual Analogue Scales (VAS) and ad libitum energy intake (EI). Dose-rising protein beverage significantly changed the postprandial trajectory of almost all biomarkers (treatment*time, p < 0.05), but did not suppress postprandial appetite (treatment*time, p > 0.05) or EI (ANOVA, p = 0.799). Circulating glycine had the strongest association with appetite response. Higher area under the curve (AUC_0-240) glycine was associated with lower EI (p = 0.026, trend). Furthermore, circulating glycine was associated with decreased Hunger in all treatment groups, whereas the associations of glucose, alanine and amylin with appetite were dependent on treatment groups. Multivariate models, incorporating multiple biomarkers, improved the estimation of appetite response (marginal R², range: 0.13-0.43). In conclusion, whilst glycine, both alone and within a multivariate model, can estimate appetite response to both water and whey protein beverage consumption, a large proportion of variance in appetite response remains unexplained. Most biomarkers, when assessed in isolation, are poor predictors of appetite response, and likely of utility only in combination with VAS and EI.

Dietary protein and appetite sensations in individuals with overweight and obesity: a systematic review

PURPOSE

This systematic review aimed to synthesize the available evidence on the effects of a high-protein diet on appetite sensations in individuals with overweight and obesity.

METHODS

Two authors independently conducted literature searches, study selection, design of the method, and quality appraisal. The main inclusion criteria were studies involving protocols that present a protein intake greater than 1.2 g/kg/day or 25% of the total daily energy content compared to a normal protein diet, i.e., 0.8-1.2 g/kg/day or 15%-20% of the total energy content. Studies that evaluated test meals or diet within a period of less than 7 days and participants with diabetes, cancer, or other specific conditions were excluded from this review. The literature search was updated until November 2019 using the main databases available.

RESULTS

Of a total of 4191 records, ten articles met the inclusion criteria and included a total of 1079 subjects. In six studies, participants experienced enhanced fullness or satiety in response to a high-dietary protein intake, of which four studies had an intervention period of 10-12 weeks.

CONCLUSION

Our results suggest that among individuals with overweight or obesity, higher dietary protein intake may influence appetite sensations by enhancing fullness or satiety. The low level of evidence, due to the heterogeneity of the protocols and the high risk of bias, highlights the need for further studies to confirm these results.

Sugar rush or sugar crash? A meta-analysis of carbohydrate effects on mood

The effect of carbohydrate (CHO) consumption on mood is much debated, with researchers reporting both mood improvements and decrements following CHO ingestion. As global consumption of sugar-sweetened products has sharply increased in recent years, examining the validity of claims of an association between CHOs and mood is of high importance. We conducted a systematic review and meta-analysis to evaluate the relationship between acute CHO ingestion and mood. We examined the time-course of CHO-mood interactions and considered the role of moderator variables potentially affecting the CHO-mood relationship. Analysis of 176 effect sizes (31 studies, 1259 participants) revealed no positive effect of CHOs on any aspect of mood at any time-point following their consumption. However, CHO administration was associated with higher levels of fatigue and less alertness compared with placebo within the first hour post-ingestion. These findings challenge the idea that CHOs can improve mood, and might be used to increase the public's awareness that the 'sugar rush' is a myth, inform health policies to decrease sugar consumption, and promote healthier alternatives.

Low-carbohydrate diet induces metabolic depression: a possible mechanism to conserve glycogen

Long-term studies have found that low-carbohydrate diets are more effective for weight loss than calorie-restricted diets in the short term but equally or only marginally more effective in the long term. Low-carbohydrate diets have been linked to reduced glycogen stores and increased feelings of fatigue. We propose that reduced physical activity in response to lowered glycogen explains the diminishing weight loss advantage of low-carbohydrate compared with low-calorie diets over longer time periods. We explored this possibility by feeding adult Drosophila melanogaster a standard or a low-carbohydrate diet for 9 days and measured changes in metabolic rate, glycogen stores, activity, and body mass. We hypothesized that a low-carbohydrate diet would cause a reduction in glycogen stores, which recover over time, a reduction in physical activity, and an increase in resting metabolic rate. The low-carbohydrate diet reduced glycogen stores, which recovered over time. Activity was unaffected by diet, but metabolic rate was reduced, in the low-carbohydrate group. We conclude that metabolic depression could explain the decreased effectiveness of low-carbohydrate diets over time and recommend further investigation of long-term metabolic effects of dietary interventions and a greater focus on physiological plasticity within the study of human nutrition.

L-Tryptophan: Biochemical, nutritional and pharmacological aspects

Tryptophan is important both for protein synthesis and as a precursor of niacin, serotonin and other metabolites. Tryptophan is an unusual amino acid because of the complexity of its metabolism, the variety and importance of its metabolites, the number and diversity of the diseases it is involved in, and because of its use in purified form as a pharmacological agent. This review covers the metabolism of tryptophan, its presence in the diet, the disorders associated with low tryptophan levels due to low dietary intake, malabsorption, or high rates of metabolism, the therapeutic effects of tryptophan and the side effects of tryptophan when it is used as a drug including eosinophilia myalgia syndrome.

Distinct tryptophan catabolism and Th17/Treg balance in HIV progressors and elite controllers

Tryptophan (Trp) catabolism into immunosuppressive kynurenine (Kyn) by indoleamine 2,3-dioxygenase (IDO) was previously linked to Th17/Treg differentiation and immune activation. Here we examined Trp catabolism and its impact on Th17/Treg balance in uninfected healthy subjects (HS) and a large cohort of HIV-infected patients with different clinical outcomes: ART-naïve, Successfully Treated (ST), and elite controllers (EC). In ART-naïve patients, increased IDO activity/expression, together with elevated levels of TNF-α and sCD40L, were associated with Treg expansion and an altered Th17/Treg balance. These alterations were normalized under ART. In contrast, Trp 2,3-dioxegenase (TDO) expression was dramatically lower in EC when compared to all other groups. Interestingly, EC displayed a distinctive Trp metabolism characterized by low Trp plasma levels similar to ART-naïve patients without accumulating immunosuppressive Kyn levels which was accompanied by a preserved Th17/Treg balance. These results suggest a distinctive Trp catabolism and Th17/Treg balance in HIV progressors and EC. Thus, IDO-induced immune-metabolism may be considered as a new inflammation-related marker for HIV-1 disease progression.

Large neutral amino acids: dietary effects on brain neurochemistry and function

The ingestion of large neutral amino acids (LNAA), notably tryptophan, tyrosine and the branched-chain amino acids (BCAA), modifies tryptophan and tyrosine uptake into brain and their conversion to serotonin and catecholamines, respectively. The particular effect reflects the competitive nature of the transporter for LNAA at the blood-brain barrier. For example, raising blood tryptophan or tyrosine levels raises their uptake into brain, while raising blood BCAA levels lowers tryptophan and tyrosine uptake; serotonin and catecholamine synthesis in brain parallel the tryptophan and tyrosine changes. By changing blood LNAA levels, the ingestion of particular proteins causes surprisingly large variations in brain tryptophan uptake and serotonin synthesis, with minimal effects on tyrosine uptake and catecholamine synthesis. Such variations elicit predictable effects on mood, cognition and hormone secretion (prolactin, cortisol). The ingestion of mixtures of LNAA, particularly BCAA, lowers brain tryptophan uptake and serotonin synthesis. Though argued to improve physical performance by reducing serotonin function, such effects are generally considered modest at best. However, BCAA ingestion also lowers tyrosine uptake, and dopamine synthesis in brain. Increasing dopamine function in brain improves performance, suggesting that BCAA may fail to increase performance because dopamine is reduced. Conceivably, BCAA administered with tyrosine could prevent the decline in dopamine, while still eliciting a drop in serotonin. Such an LNAA mixture might thus prove an effective enhancer of physical performance. The thoughtful development and application of dietary proteins and LNAA mixtures may thus produce treatments with predictable and useful functional effects.

Eating breakfast enhances the efficiency of neural networks engaged during mental arithmetic in school-aged children

To determine the influence of a morning meal on complex mental functions in children (8-11 y), time-frequency analyses were applied to electroencephalographic (EEG) activity recorded while children solved simple addition problems after an overnight fast and again after having either eaten or skipped breakfast. Power of low frequency EEG activity [2 Hertz (Hz) bands in the 2-12 Hz range] was determined from recordings over frontal and parietal brain regions associated with mathematical thinking during mental calculation of correctly answered problems. Analyses were adjusted for background variables known to influence or reflect the development of mathematical skills, i.e., age and measures of math competence and math fluency. Relative to fed children, those who continued to fast showed greater power increases in upper theta (6-8 Hz) and both alpha bands (8-10 Hz; 10-12 Hz) across sites. Increased theta suggests greater demands on working memory. Increased alpha may facilitate task-essential activity by suppressing non-task-essential activity. Fasting children also had greater delta (2-4 Hz) and greater lower-theta (4-6 Hz) power in left frontal recordings-indicating a region-specific emphasis on both working memory for mental calculation (theta) and activation of processes that suppress interfering activity (delta). Fed children also showed a significant increase in correct responses while children who continued to fast did not. Taken together the findings suggest that neural network activity involved in processing numerical information is functionally enhanced and performance is improved in children who have eaten breakfast, whereas greater mental effort is required for this mathematical thinking in children who skip breakfast.

Fiber, protein, and lupin-enriched foods: role for improving cardiovascular health

Cardiovascular diseases (CVD) are the leading cause of death globally (World Health Organisation, 2011). Many of the risk factors for CVD are modifiable, including overweight and obesity. Numerous strategies have been proposed to fight CVD, with a special focus being placed on dietary interventions for weight management. The literature suggests that two nutrients, fiber and protein, may play significant roles in weight control and hence cardiovascular health. Increasing both protein and fiber in the diet can be difficult because popular low-carbohydrate and high-protein diets tend to have considerably low-fiber intakes (Slavin, 2005). One approach to obtain both is to develop functional foods using unique ingredients. Lupin flour is a novel food ingredient derived from the endosperm of lupin. It contains 40-45% protein, 25-30% fiber, and negligible sugar and starch (Petterson and Crosbie, 1990). Research conducted to date reveals that lupin-enriched foods, which are naturally high in protein and fiber, may have a significant effect on CVD risk factors. This review explores whether there is a role for fiber-, protein-, and lupin-enriched foods in improving cardiovascular health.

Mechanism of acute tryptophan depletion: is it only serotonin?

The method of acute tryptophan depletion (ATD), which reduces the availability of the essential amino acid tryptophan (TRP), the dietary serotonin (5-hydroxytryptamine (5-HT)) precursor, has been applied in many experimental studies. ATD application leads to decreased availability of TRP in the brain and its synthesis into 5-HT. It is therefore assumed that a decrease in 5-HT release and subsequent blunted neurotransmission is the underlying mechanism for the behavioural effects of ATD. However, direct evidence that ATD decreases extracellular 5-HT concentrations is lacking. Furthermore, several studies provide support for alternative underlying mechanisms of ATD. This may question the utility of the method as a selective serotonergic challenge tool. As ATD is extensively used for investigating the role of 5-HT in cognitive functions and psychiatric disorders, the potential of alternative mechanisms and possible confounding factors should be taken into account. It is suggested that caution is required when interpreting ATD effects in terms of a selective serotonergic effect.

Long-term effects of provided low and high glycemic load low energy diets on mood and cognition

Energy-restricted low glycemic load diets are being used increasingly for weight loss. However, the long-term effects of such regimens on mood and cognitive performance are not known. We assessed the effects of low glycemic load (LG) and high glycemic load (HG) energy-restricted diets on mood and cognitive performance during 6 months of a randomized controlled trial when all food was provided. Subjects were 42 healthy overweight adults (age 35+/-5 years; BMI 27.8+/-1.6 kg/m(2)) with a mean weight loss of 8.7+/-5.0% that did not differ significantly by diet randomization. Mood was assessed by using the Profile of Mood States (POMS) questionnaire. Cognitive performance was assessed by using computerized tests of simple reaction time, vigilance, learning, short-term memory and attention, and language-based logical reasoning. Worsening mood outcome over time was observed in the HG diet group compared to the LG for the depression subscale of POMS (p=0.009 after including hunger as a covariate). There was no significant change over time in any cognitive performance values. These findings suggest a negative effect of an HG weight loss diet on sub-clinical depression but, in contrast to a previous suggestion, provide no support for differential effects of LG versus HD diets on cognitive performance.

Neuropharmacology of human appetite expression

The regulation of appetite relies on the integration of numerous episodic (meal) and tonic (energy storage) generated signals in energy regulatory centres within the central nervous system (CNS). These centers provide the pharmacological potential to modify human appetite (hunger and satiety) to increase or decrease caloric intake, or to normalize aberrant eating behavior. With regard to obesity, the satiety enhancing anti-obesity drug sibutramine has proved effective at reducing body weight. Additionally, the endocannabinoid CB(1) antagonist rimonabant has recently been approved for use in Europe (but not in the US). A 5-HT(2C) agonist lorcaserin is also currently undergoing large-scale clinical trials, but the effect of the drug on human appetite is unknown as yet. Appetite enhancing drugs such as magestrol acetate and dronabiol are currently used to promote weight gain. Finally, sibutramine, selective serotonergic reuptake inhibitors such as fluoxetine and some anti-epileptic drugs have all been used to normalise aberrant eating behaviour. All these drugs act by modifying the expression of human appetite. An assessment of a drug's effects on caloric intake and feelings of hunger and satiety is necessary before they can be considered for clinical use.

Carbohydrate craving: a double-blind, placebo-controlled test of the self-medication hypothesis

Carbohydrate craving, the overwhelming desire to consume carbohydrate-rich foods in an attempt to improve mood, remains a scientifically controversial construct. We tested whether carbohydrate preference and mood enhancement could be demonstrated in a double-blind, placebo-controlled self-administration trial. Overweight females who met strict operational criteria for carbohydrate craving participated in two 3-day discrete choice trials over a 2-week period. Participants reported their mood before and at several time points after undergoing a dysphoric mood induction and ingesting, either a carbohydrate beverage or a taste and calorie-matched protein-rich balanced nutrient beverage. Every third testing day, participants were asked to self-administer the beverage they preferred based on its previous mood effect. Results showed that, when rendered mildly dysphoric, carbohydrate cravers chose the carbohydrate beverage significantly more often than the protein-rich beverage and reported that carbohydrate produced greater mood improvement. The carbohydrate beverage was perceived as being more palatable by the carbohydrate cravers, although not by independent taste testers who performed the pre-trial taste matching. This study, performed under rigorous study conditions, supports the existence of a carbohydrate craving syndrome in which carbohydrate self-administration improves mildly dysphoric mood.

Egg breakfast enhances weight loss

OBJECTIVE

To test the hypotheses that an egg breakfast, in contrast to a bagel breakfast matched for energy density and total energy, would enhance weight loss in overweight and obese participants while on a reduced-calorie weight loss diet.

SUBJECTS

Men and women (n=152), age 25-60 years, body mass index (BMI) >or=25 and <or=50 kg m(-2).

DESIGN

Otherwise healthy overweight or obese participants were assigned to Egg (E), Egg Diet (ED), Bagel (B) or Bagel Diet (BD) groups, based on the prescription of either an egg breakfast containing two eggs (340 kcal) or a breakfast containing bagels matched for energy density and total energy, for at least 5 days per week, respectively. The ED and BD groups were suggested a 1000 kcal energy-deficit low-fat diet, whereas the B and E groups were asked not to change their energy intake.

RESULTS

After 8 weeks, in comparison to the BD group, the ED group showed a 61% greater reduction in BMI (-0.95+/-0.82 vs -0.59+/-0.85, P<0.05), a 65% greater weight loss (-2.63+/-2.33 vs -1.59+/-2.38 kg, P<0.05), a 34% greater reduction in waist circumference (P<0.06) and a 16% greater reduction in percent body fat (P=not significant). No significant differences between the E and B groups on the aforementioned variables were obtained. Further, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and triglycerides, did not differ between the groups.

CONCLUSIONS

The egg breakfast enhances weight loss, when combined with an energy-deficit diet, but does not induce weight loss in a free-living condition. The inclusion of eggs in a weight management program may offer a nutritious supplement to enhance weight loss.

Lifestyle-related factors in predementia and dementia syndromes

Cognitive decline and dementia have a deep impact on the health and quality of life of older subjects and their caregivers. Since the therapeutic options currently available have demonstrated limited efficacy, the search for preventive strategies for cognitive decline and dementia are mandatory. A possible role of lifestyle-related factors was recently proposed for age-related changes of cognitive function, predementia syndromes and the cognitive decline of degenerative (Alzheimer's disease [AD]) or vascular origin. At present, cumulative evidence suggests that vascular risk factors may be important in the development of mild cognitive impairment (MCI), dementia and AD. Moderate alcohol drinking has been proposed as a protective factor against MCI and dementia in several longitudinal studies, but contrasting findings also exist. The Mediterranean diet could therefore be an interesting model with which to further study the association between dietary patterns and cognitive functioning, given the suggested role of many components of this diet (monounsaturated fatty acids, polyunsaturated fatty acids, cereals and red wine) in contrasting cognitive impairment and dementia. The association between low education and predementia and dementia syndromes is supported by the majority of studies, but very few studies have investigated whether this association may be attributed with lifestyle factors that covary with education. Studies in the literature seem to identify in physical exercise one promising strategy in decreasing cognitive decline, but some of the limitations of these studies do not allow us to draw definite conclusions. At present, in older subjects, healthy diets, antioxidant supplements, the prevention of nutritional deficiencies, and moderate physical activity could be considered the first line of defense against the development and progression of predementia and dementia syndromes. However, in most cases, these were only observational studies, and results are awaited from large multicenter randomized clinical trials in older persons that may clarify the possible synergy, for example, between moderate exercise, physical activity and healthy Mediterranean diet on cognition in the elderly.

Satiating effects of protein but not carbohydrate consumed in a between-meal beverage context

Previous research has suggested that protein is the most satiating macronutrient; however some experiments have found no difference in satiating efficiency of protein and carbohydrate during short intervals after consumption. There is also evidence that the satiating effects of carbohydrate are minimal when in a beverage rather than solid context. To evaluate whether protein-based satiety was evident in a drink context, and clarify further effects of preload time on satiety, the present study compared iso-energetic dairy fruit drink preloads ( approximately 1250 kJ), differing in macronutrient composition and consumed at two time intervals in the morning. Using a counterbalanced within-subjects design, 18 unrestrained lean male volunteers consumed 300 ml of carbohydrate-enriched (CHO), protein-enriched and low-energy control (327 kJ) dairy fruit drinks, 120 min and 30 min before an ad libitum lunch. Significantly less energy was consumed at lunch after the protein (3234 kJ) compared to the control (3468 kJ, p<0.05) and CHO preloads (3588 kJ, p<0.05). However, this was not sufficient to show complete energy compensation. Preload time of consumption did not impact upon any measures. Only satiety ratings at the beginning of lunch varied significantly by preload type, reflecting differences in test meal intake. These findings are consistent with previous research that protein is more satiating than carbohydrate. The roles of sensory and hedonic characteristics are discussed.

Effects of alpha-lactalbumin on emotional processing in healthy women

The synthesis of serotonin (5-HT) in the central nervous system is dependent on the availability to the brain of its precursor amino acid, tryptophan (TRP). Recent studies suggest that alpha-lactalbumin, a whey-derived protein with a relatively high TRP content, increases plasma TRP and produces endocrine and cognitive changes consistent with facilitation of brain 5-HT function. In the present study we assessed the biochemical and cognitive effects of alpha-lactalbumin (40 g) in 28 healthy female subjects in a parallel group, placebo-controlled design. Relative to a casein-derived control protein, alpha-lactalbumin increased plasma TRP and the ratio of TRP to neutral amino acids. However, there was no effect on salivary cortisol secretion or tasks of emotional processing shown previously to be sensitive to pharmacological manipulation of 5-HT in healthy volunteers. The results suggest that alpha-lactalbumin produces a relatively modest increase in TRP availability which may not be sufficient to produce the changes in emotional processing seen with administration of pure TRP in healthy subjects. Further studies in subjects more vulnerable to stress are needed to assess the potential therapeutic effects of alpha-lactalbumin in clinical populations.

Does a high-protein diet improve weight loss in overweight and obese children?

OBJECTIVE

To evaluate the effect of a high-protein diet on anthropometry, body composition, subjective appetite, and mood sensations in overweight and obese children attending a residential weight-loss camp.

RESEARCH METHODS AND PROCEDURES

Children (120; BMI, 33.1 +/- 5.5 kg/m(2); age, 14.2 +/- 1.9 years) were randomly assigned to either a standard or high-protein diet group (15% vs. 22.5% protein, respectively). All children were assessed at baseline and at the end of the camp for anthropometry, body composition, blood pressure, biochemical variables (n = 27), and subjective appetite and mood sensations (n = 50).

RESULTS

Attendance at the weight-loss camp resulted in significant improvements in most measures. Campers lost 5.5 +/- 2.9 kg in body weight (p < 0.001) and 3.8 +/- 5.4 kg in fat mass (p < 0.001) and reduced their BMI standard deviation score by 0.27 +/- 0.1 (p < 0.001) and their waist circumference by 6.6 +/- 2.8 cm (p < 0.001). Subjective sensations of hunger increased significantly over the camp duration, but no other changes in appetite or mood were observed. There were no significant differences between the two diets on any physical or subjective measures.

DISCUSSION

Weight-loss camps are effective in assisting children to lose weight and improve on a range of health outcomes, independently of the protein content of the diet. The implications of an increase in hunger associated with weight loss needs to be considered. Further work is warranted to investigate whether higher levels of dietary protein are feasible or effective in longer-term weight-loss interventions of this type.

Changes in plasma amino Acid levels do not predict satiety and weight loss on diets with modified macronutrient composition

OBJECTIVE

Serotonin mediates satiety in the central nervous system. Brain serotonin content depends on the plasma ratio of tryptophan (Trp) to large neutral amino acids (LNAA) and may be affected by diet composition. We examined whether high-carbohydrate or high-protein diets induce satiety and weight loss by altering plasma concentrations of these amino acids.

METHODS

In study 1 (n = 16, BMI = 27.0 +/- 2.3), we compared plasma Trp and LNAA concentrations averaged over 24 h after 2 weeks of consuming isocaloric diets containing either 45 or 65% of total energy as carbohydrate. In study 2 (n = 19, BMI = 26.2 +/- 2.1), we made the same measurements following diets containing either 15 or 30% of total energy as protein. To assess satiety in both studies, we recorded caloric intake and weight changes during a subsequent 12-week period of ad libitum consumption of the experimental diets.

RESULTS

Ad libitum caloric intake fell by 222 +/- 81 kcal/day with a 3.7 +/- 0.6 kg weight loss at 12 weeks in study 1. Ad libitum caloric intake fell by 441 +/- 63 kcal/ day with a 4.9 +/- 0.5 kg weight loss at 12 weeks in study 2. The 24-hour averaged plasma concentration of Trp and the Trp:LNAA ratio were unaffected by the isocaloric increase in carbohydrate or protein consumption that preceded the ad libitum administration of the 2 diets.

CONCLUSION

An increase in either carbohydrate or protein intake increases satiety and leads to significant weight loss, however, these effects are not mediated by an increase in plasma concentration of Trp or the Trp:LNAA ratio.

The effects of sucrose and maize oil on subsequent food intake and mood

The effects of sucrose and oil preloads were explicitly compared in a single-blind controlled trial using a between-subjects design. Eighty adult subjects (forty-three male, thirty-seven female) aged 18–50 years received at 11.00 hours one of four yoghurt preloads. All were 80 g low-fat, unsweetened yoghurt (188 kJ), containing additionally (1) saccharin (control, 23 kJ), or (2) 40 g sucrose (859 kJ), (3) 40 g maize oil (1569 kJ), (4) 20 g sucrose, 20 g maize oil (1213 kJ). Subjects were normal eaters and of normal weight (male mean weight: 68·8 (sd 3·2) kg, BMI 21·8 (sd 1·6) kg/m2; female mean weight: 53·7 (sd 5·1) kg, BMI 20·4 (sd 1·2) kg/m2). Food intake was measured with a food diary and mood with ten single Likert scales. ANOVA was conducted using preload type (saccharin, sucrose, oil, sucrose + oil), sex (male, female) and early v. late breakfast times as factors. Mood was analysed using the same design, with time of rating (immediate, 60 min, 120 min) as an additional factor. Men ate more after the saccharin preload than after the other preloads, but did not vary the time of their next solid food. Women increased the intermeal interval only after the oil preload, which also had the highest energy content value, but did not vary the energy content of their next solid food. The saccharin preload decreased rated tiredness at 2 h compared with the sucrose preload, possibly due to its lower energy content. The preloads containing sucrose or sucrose + oil increased calmness between 1 and 2 h afterwards, compared with the saccharin preload. It is concluded that both sucrose and oil increase the intermeal interval in men, but that women are less sensitive to preloading. The mood effects suggest that tiredness after carbohydrate at 2 h may in part be a decrease in rated energy compared with the increased rated energy found after a preload with low energy content. Carbohydrate may genuinely increase calmness. These effects apply to non-restrained eaters of normal weight.

Long-term dietary compensation for added sugar: effects of supplementary sucrose drinks over a 4-week period

The long-term physiological effects of refined carbohydrates on appetite and mood remain unclear. Reported effects when subjects are not blind may be due to expectations and have rarely been studied for more than 24 h. The present study compared the effects of supplementary soft drinks added to the diet over 4 weeks on dietary intake, mood and BMI in normal-weight women (n 133). Subjects were categorised as 'watchers' or 'non-watchers' of what they ate then received sucrose or artificially sweetened drinks (4 x 250 ml per d). Expectancies were varied by labelling drinks 'sugar' or 'diet' in a counter-balanced design. Sucrose supplements provided 1800 kJ per d and sweetener supplements provided 67 kJ per d. Food intake was measured with a 7 d diary and mood with ten single Likert scales. By 4 weeks, sucrose supplements significantly reduced total carbohydrate intake (F(1,129) = 53.81; P<0.001), fat (F(2,250) = 33.33; P<0.001) and protein intake (F(2,250) = 28.04; P<0-001) compared with sweetener supplements. Mean daily energy intake increased by just under 1000 kJ compared with baseline (t (67 df) = 3.82; P< 0.001) and was associated with a non-significant trend for those receiving sucrose to gain weight. There were no effects on appetite or mood. Neither dietary restraint status as measured by the Dutch Eating Behaviour Questionnaire nor the expectancy procedure had effects. Expectancies influenced mood only during baseline week. It is concluded that sucrose satiates, rather than stimulates, appetite or negative mood in normal-weight subjects.

Changing food preference as a function of mood

The authors investigated the effect of mood on food selection. Participants (N = 98) indicated the likelihood of general eating and the likelihood of eating specific foods after reading and projecting themselves onto the events and emotions described in a sad and a happy vignette. Both men and women believed they were more likely to consume food following a happy versus a sad event, and men believed they were significantly more likely to eat than did women. However, the type of food men and women believed they would consume interacted with the type of event experienced. Vegetarian snack foods were more likely to be consumed following a happy versus a sad event, with men more likely to eat snack foods. Men did not significantly change in likelihood of consuming sweet foods as their mood changed. However, women believed they were more likely to consume sweet foods following a sad event. The authors discuss the results in terms of a self-medication hypothesis and the effect of carbohydrates on central serotonin and endogenous opioids. Overall, results demonstrated that mood influences belief in the likelihood of food selection.

Isocaloric meal and snack foods differentially affect eating behavior

The present study tested whether foods categorized as meals reduce subsequent intake more than isocaloric foods categorized as snacks. The study was repeated three times with variations. In each variation we manipulated whether subjects received meal or snack foods in an isocaloric load. In Variation 1, subjects consumed less following a load of meal foods than snacks. Variation 2 found this effect to be short-term, affecting food choice 20 min following a load but not 3 h later. Variation 3 demonstrated: (1) this effect occurs independent of the effects of the weights of foods, and (2) this effect varies specifically with subject perceptions of foods (i.e. whether they are part of a meal or snack). These results are discussed in terms of how cognitive representations of preload foods can influence subsequent consumption.

Short-Term Effect of Eggs on Satiety in Overweight and Obese Subjects

OBJECTIVE

To test the hypotheses that among overweight and obese participants, a breakfast consisting of eggs, in comparison to an isocaloric equal-weight bagel-based breakfast, would induce greater satiety, reduce perceived cravings, and reduce subsequent short-term energy intake.

SUBJECTS

Thirty women with BMI's of at least 25 kg/M2 between the ages of 25 to 60 y were recruited to participate in a randomized crossover design study in an outpatient clinic setting.

DESIGN

Following an overnight fast, subjects consumed either an egg or bagel-based breakfast followed by lunch 3.5 h later, in random order two weeks apart. Food intake was weighed at breakfast and lunch and recorded via dietary recall up to 36 h post breakfast. Satiety was assessed using the Fullness Questionnaire and the State-Trait Food Cravings Questionnaire, state version.

RESULTS

During the pre-lunch period, participants had greater feelings of satiety after the egg breakfast, and consumed significantly less energy (kJ; 2405.6 +/- 550.0 vs 3091.3 +/- 445.5, Egg vs Bagel breakfasts, p < 0.0001), grams of protein (16.8 +/- 4.2 vs 22.3 +/- 3.4, Egg vs Bagel breakfasts, p < 0.0001), carbohydrate 83.1 +/- 20.2 vs 110.9 +/- 18.7, Egg vs Bagel breakfasts, p < 0.0001), and fat 19.4 +/- 5.1 vs 22.8 +/- 3.2, Egg vs Bagel breakfasts, p < 0.0001) for lunch. Energy intake following the egg breakfast remained lower for the entire day (p < 0.05) as well as for the next 36 hours (p < 0.001).

CONCLUSIONS

Compared to an isocaloric, equal weight bagel-based breakfast, the egg-breakfast induced greater satiety and significantly reduced short-term food intake. The potential role of a routine egg breakfast in producing a sustained caloric deficit and consequent weight loss, should be determined.

Memory function in women with premenstrual complaints and the effect of serotonergic stimulation by acute administration of an alpha-lactalbumin protein

Serotonergic hypofunction may underlie at least part of the symptoms that are experienced by women with premenstrual complaints, including memory deficits. In the current study we investigated changes in memory functions in the premenstrual phase compared to the early postmenstrual phase in 16 women with premenstrual complaints. In addition, the effect of an acute serotonergic stimulation by administration of an alpha-lactalbumin protein on premenstrual memory performance was assessed using a double-blind placebo-controlled crossover design. It was found that both short-term and long-term memory for words (30-word learning task) and abstract figures (abstract visual learning task) were mildly impaired in the premenstrual phase. Administration of alpha-lactalbumin during the premenstrual phase could only partially attenuate the memory performance decrements that are seen in the premenstrual phase. Specifically, alphalactalbumin improved long-term memory for abstract figures, but not for words. There were no effects of menstrual phase or alpha-lactalbumin on planning functions (computerized Tower of London). The data suggest that serotonergic hypofunction may play a role in premenstrual memory decline, but serotonergic mechanisms cannot fully account for observed cognitive changes in the premenstrual phase.

The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review

For years, proponents of some fad diets have claimed that higher amounts of protein facilitate weight loss. Only in recent years have studies begun to examine the effects of high protein diets on energy expenditure, subsequent energy intake and weight loss as compared to lower protein diets. In this study, we conducted a systematic review of randomized investigations on the effects of high protein diets on dietary thermogenesis, satiety, body weight and fat loss. There is convincing evidence that a higher protein intake increases thermogenesis and satiety compared to diets of lower protein content. The weight of evidence also suggests that high protein meals lead to a reduced subsequent energy intake. Some evidence suggests that diets higher in protein result in an increased weight loss and fat loss as compared to diets lower in protein, but findings have not been consistent. In dietary practice, it may be beneficial to partially replace refined carbohydrate with protein sources that are low in saturated fat. Although recent evidence supports potential benefit, rigorous longer-term studies are needed to investigate the effects of high protein diets on weight loss and weight maintenance.

Islet cell response in the neonatal rat after exposure to a high-fat diet during pregnancy

Although pancreatic beta-cells are capable of adapting their mass in response to insulin requirements, evidence has shown that a dietary insult could compromise this ability. Fetal malnutrition has been linked to low birth weight and the development of type 2 diabetes later in life, while reduced beta-cell mass has been reported in adult rats fed a high-fat diet (HFD). Reported here are the effects of exposure to a HFD, during different periods of gestation, on neonatal rat weight and beta- and alpha-cell development. The experimental groups were composed of neonatal offspring obtained from Wistar rats fed a high-fat (40% as energy) diet for either the first (HF1), second (HF2), or third (HF3) week, or all three (HF1-3) weeks of gestation. Neonatal weights and circulating glucose and insulin concentrations were measured on postnatal day 1, after which the pancreata were excised and processed for histological immunocytochemical examination and image analysis. HF1 and HF2 neonates were hypoglycemic, whereas HF1-3 neonates were hyperglycemic. Low birth weights were observed only in HF1 neonates. No significant differences were detected in the circulating insulin concentrations in the neonates, although beta-cell volume and numbers were reduced in HF1-3 neonates. beta-cell numbers also declined in HF1 and HF3 neonates. alpha-cell volume, number and size were, however, increased in HF1-3 neonates. alpha-cell size was also increased in HF1 and HF3 neonates. In neonates, exposure to a maternal HFD throughout gestation was found to have the most adverse effect on beta-cell development and resulted in hyperglycemia.

Effects of a novel method of acute tryptophan depletion on plasma tryptophan and cognitive performance in healthy volunteers

RATIONALE

Disorders associated with low levels of serotonin (5-HT) are characterized by mood and cognitive disturbances. Acute tryptophan depletion (ATD) is an established method for lowering 5-HT levels and an important tool to study the effects of reduced 5-HT on mood and cognition in human subjects. The traditional ATD method, i.e., administration of separate amino acids (AAs), has several disadvantages. The AA mixture is costly, unpalatable and associated with gastrointestinal discomfort.

OBJECTIVES

The University of Maastricht developed a new and inexpensive method for ATD: a natural collagen protein (CP) mixture with low tryptophan (TRP) content. The reductions in plasma TRP after taking this CP mixture were compared with the reductions achieved taking the traditional AA mixture, and effects on memory and reversal learning were studied.

METHODS

Fifteen healthy young volunteers participated in a double-blind, counterbalanced within-subject study. Reversal learning, verbal memory and pattern recognition were assessed at baseline and 3-4 h after taking the CP mixture.

RESULTS

The new ATD method significantly reduced plasma TRP by 74% and the ratio between TRP and the other large AAs (TRP/LNAA) by 82%. The placebo mixture did not change these measures. Delayed recognition reaction time on the verbal learning task was increased following ATD. No other cognitive effects were found.

CONCLUSIONS

The CP mixture was shown to be an efficient tool for lowering plasma TRP in humans. The validity of this method with regard to behavioral changes remains to be established in healthy, vulnerable and clinical populations.

Is there a timing synergy during multi-finger production of quick force pulses?

We studied whether characteristics of individual finger force profiles covaried across repetitions of a quick force pulse production task to stabilize the required magnitude and timing of the peak force. Subjects produced series of quick force pulses by pressing with all four fingers of the right hand on force sensors under the instruction to keep the magnitude of the peak of total force at 15 N and reach the force peaks at prescribed times. Individual finger force pulses were then reshuffled across trials to create a surrogate data set. The surrogate data set showed a lower average peak force with a larger dispersion. This finding has been interpreted as pointing at predominantly negative covariation among finger force pulses in the actual data that stabilized the required magnitude of the total force, a force synergy. The difference between the actual and surrogate data sets was significant early into the pulse time, starting about 40 ms after the pulse initiation. This finding points at a central nature of the negative covariation without a major role played by visual or proprioceptive feedback. In contrast,the surrogate data set showed smaller dispersion of the timing of the total peak force, suggesting positive covariation of the timings of individual finger force pulses in the actual data interpreted as the lack of a timing synergy. These results have been confirmed with principal component (PC) analysis. The first PC for the timing of the individual finger peak forces accounted for over 90% of the total variance for the actual data set and for under 40% of the total variance for the surrogate data set. The fourth PC for the magnitudes of the finger forces accounted for under 4% of the total variance for the actual data set and for over 15% of the variance for the surrogate data set. The data are interpreted within the uncontrolled manifold hypothesis; they support the hierarchical control scheme suggested by Schöner.

Alpha-lactalbumin combined with a regular diet increases plasma Trp-LNAA ratio

Brain serotonin influences food intake and mood. It is synthesised from tryptophan (Trp) of which uptake in the brain is dependent on plasma ratio of tryptophan to the sum of other large neutral amino acids (Trp-LNAA). A carbohydrate-rich diet increases this ratio, whereas a protein-rich diet decreases it. Yet, if the protein source is alpha-lactalbumin the ratio increases. It is, however, unknown whether this also happens in the context of a regular diet (15% protein). We studied the effect of an alpha-lactalbumin supplement combined with regular diet on plasma Trp-LNAA ratio, serum prolactin (marker of serotonin synthesis), food intake, appetite, macronutrient preference and mood. Eighteen healthy males participated in a double-blind, randomised, placebo-controlled, crossover study. One hour after breakfast they received a drink containing alpha-lactalbumin and carbohydrates (AS) or carbohydrates (PS) only. Plasma Trp-LNAA ratio, serum prolactin, food intake, appetite, macronutrient preference and mood were assessed before and 90 min after consumption of the supplement. Changes of plasma Trp-LNAA ratio differed (P<.001) between both supplements, increasing by 16% after AS and decreasing by 17% after PS. Decrease of serum prolactin was slightly smaller after AS than after PS (P=.083). Appetite, food intake, macronutrient preference or mood did not differ between supplements. We conclude that an alpha-lactalbumin-enriched supplement combined with a regular diet increases plasma Trp-LNAA ratio and may influence serum prolactin, but we could not demonstrate effects on appetite, food intake, macronutrient preference and mood.

Insulin sensitivity and premenstrual syndrome

Maintaining normal blood glucose levels is a constant challenge for women with diabetes. Anecdotal reports reveal that many women question if menstrual cycle phases may affect their blood glucose levels. However, results from studies investigating the effect of the menstrual cycle on insulin sensitivity in diabetic women have been conflicting. One variable that may account for the conflicting results is the presence or absence of premenstrual syndrome (PMS), which may exacerbate menstrual cycle-related effects on insulin sensitivity. Treatment of PMS with serotonin reuptake inhibitors may alleviate the symptoms of PMS, as well as improve insulin sensitivity and help regulate blood glucose levels.

Difficulties in establishing reference intervals for special fluids: the example of 5-hydroxyindoleacetic acid and homovanillic acid in cerebrospinal fluids

Biochemical measurements in “special fluids” are complicated with the problem of reference intervals. Reference intervals are difficult to establish for these types of samples since they are usually only collected in patients with clinical suspicion of disease. Determination of neurotransmitter metabolites in cerebrospinal fluid illustrates this difficulty. This paper will review the factors and circumstances that have been identified or are suspected to modifythe concentration of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in cerebrospinal fluid. In addition to obvious parameters such as age-related variation that can affect the concentration of 5-HIAA and HVA in cerebrospinal fluid, a varietyof other factors can explain the wide range of “control” group sizes reported in the literature. Reference intervals must take into account the purpose of cerebrospinal fluid examinations, whether they be prospective studies to explore physio-pathologic relationships or for diagnostic purposes. In the latter case, certain neurological disorders cannot be excluded if a single measured value is within the reference interval.

Similar effects of foods high in protein, carbohydrate and fat on subsequent spontaneous food intake in healthy individuals

Pre-loads high in protein, as compared to carbohydrate and fat, produce greater satiety and reduce food intake after a fixed time interval. This study investigated the effect of macronutrient composition on spontaneous eating behaviour. On four separate occasions, 16 fasted, healthy, non-obese men, blinded to the true purpose of the study, consumed iso-energetic ( approximately 3MJ) yoghurt-based pre-loads of equivalent weight ( approximately 0.5 kg), high in fat (40%) [HF], carbohydrate (60%) [HC] or protein (29%) [HP], and no pre-load in a randomized, single-blind fashion. Subjects ate at will from a selection of food items for the remainder of the day (7 h) with the time of food requests (h) and energy content (kJ) and macronutrient distribution (%) of food eaten recorded. The three pre-loads delayed the first spontaneous request for food by 1.5-1.8 h relative to no pre-load. Total spontaneous food intake was suppressed 29% [HP], 20% [HF] and 17% [HC] by the pre-loads. Neither the amount of food eaten per spontaneous eating episode, nor the spontaneous eating frequency differed statistically following ingestion of the different pre-loads or no pre-load. In this study, in subjects who were free to choose when as well as how much they ate, a high-protein pre-load exerted similar effects on satiety as did iso-energetic high-fat and high-carbohydrate pre-loads.

Functional foods: psychological and behavioural functions

It is easier to demonstrate the consistent effects of foods on satiety than on cognitive performance. This is understandable since the satiety system incorporates physiological signalling systems that mediate the effects of foods on function. Specific manipulations of proteins, carbohydrates and fats have the potential to act as functional foods for appetite control. Because of the importance of the optimal functioning of cognitions for survival, these functions are quite strongly protected against short-term dietary and physiological perturbances. Therefore, food manipulations may be better detected through the degree of effort exerted to maintain performance rather than via changes in the actual performance itself. This procedure has not been widely used hitherto. The concept of biomarkers may have to be interpreted differently from research on physiological systems or clinical endpoints. For satiety, adjustments in the profile of hunger could serve as a biomarker or surrogate endpoint. For cognitions, correlated physiological variables may be more difficult to measure than the functional endpoint itself. Changes related to unitary functions (such as tracking) could serve as biomarkers for more complex, integrated skills (such as car driving). Since food manipulations may affect multiple functions, the challenge is to design foods with good satiety control that do not impair mental performance; or alternatively to engineer foods that optimise cognitive performance without compromising satiety. This rapidly developing field has great potential for close collaboration between academia and industry in the production of commercially successful products that show clear improvements in human functioning with the capacity to protect against disease or impairment.

Carbohydrate ingestion, blood glucose and mood

A series of studies have reported that a high carbohydrate meal, or diets high in carbohydrate, were associated with feeling less energetic. However, after a drink containing pure sugar most studies report no effect. Meals almost exclusively carbohydrate increase the availability of tryptophan and hence serotonin synthesis in the brain, however, a small amount of protein blocks this mechanism making it an uncommon response. In many individuals, poor mood stimulates the eating of palatable high carbohydrate/high fat foods that stimulate the release of endorphins. There is a tendency for those with lower blood glucose, when performing cognitively demanding tasks, to report poorer mood. In a range of situations an association between a tendency for blood glucose levels to fall rapidly, and irritability, has been found. Differences in the ability to control blood glucose levels influence the association between carbohydrate intake and mood. There is a need in future research to contrast the impact of carbohydrate on mood in those distinguished because of their pre-existing psychological and physiological functioning.