Social, circadian, nutritional, and subjective correlates of the spontaneous pattern of moderate alcohol intake of normal humans

Positive but not negative affect is associated with increased daily drinking likelihood in non-clinical populations: systematic review and meta-analyses

Background: Recent meta-analytical findings indicate that affect regulation plays an important role in alcohol craving, consumption volume, and substance use. However, in view of mixed findings, the affect and drinking likelihood literature remains in need of clarification and consolidation.Objectives: This systematic review with meta-analyses interrogated the results from peer-reviewed studies among non-clinical populations that examined the relationship between daily affective states and intraday likelihood of alcohol consumption.Method: A PRISMA guided search of PsychINFO, PsycARTICLES, Science Direct, Wiley Online Library, PubMed, SCOPUS, and JSTOR databases was conducted. Multilevel meta-analyses yielded 11 eligible negative affect studies (2751 participants, 23 effect sizes) and nine studies on positive affect (2244 participants, 14 effect sizes).Results: The pooled associations between intra-day affect and alcohol consumption likelihood revealed no significant association between negative affective state and drinking likelihood (OR = .90, 95% CI [.73, 1.12]) and that positive affect was associated with increased drinking likelihood (OR = 1.17, 95% CI [1.09, 1.27]). Egger's test, P-curve, fail-safe N, and selection models analyses suggested that the obtained results were unlikely to be the product of publication bias and p-hacking alone.Conclusions: Results converge to suggest that, independent of age, affect measure used, and study design, a significant albeit modest relationship between positive affect and alcohol consumption likelihood exists, which does not appear to be the case for negative affect. In conjunction with other recent meta-analyses, current findings help map out a more nuanced understanding of the affect-alcohol/substance use relationship, with potential implications for interventions.

Towards an affect intensity regulation hypothesis: Systematic review and meta-analyses of the relationship between affective states and alcohol consumption

While self-medication and positive and negative reinforcement models of alcohol use suggest that there is an association between daily affect and alcohol consumption, findings within the academic literature have been inconsistent. This pre-registered systematic review meta-analytically interrogated the results from studies amongst non-clinical populations that examine the relationship between daily affective states and alcohol consumption volume. PRISMA guided searches of PsychINFO, PsycARTICLES, Science Direct, PubMed, SCOPUS, and JSTOR databases were conducted. When both laboratory and field studies were included, meta-analyses with robust variance estimation yielded 53 eligible studies on negative affect (8355 participants, 127 effect sizes) and 35 studies for positive affect (6384 participants, 50 effect sizes). The significant pooled associations between intra-day affect and alcohol consumption were r = .09, [.03, .14] for negative affect, and r = .17, [.04, .30] for positive affect. A small-to-medium sized effect (d = .275, [.11, .44]) of negative affect on daily alcohol consumption volume was found in laboratory studies (14 studies, 1100 participants). While publication bias was suspected, P-curve analyses suggested that the results were unlikely to be the product of publication bias and p-hacking alone, and selection model analysis revealed no significant differences in results when publication bias was accounted for. For negative affect, using number of drinks as the measure of alcohol consumption was associated with lower effect sizes. For positive affect, the results demonstrated a decline of this observed effect over time. Overall, findings point towards the possibility of developing an affect intensity regulation theory of alcohol use. Conceptualizing the mood-alcohol nexus in terms of affect intensity regulation may afford a more parsimonious explanation of alcohol consumption rather than viewing the behavior as being shaped by either positive or negative affective states.

Thirst at Work Implies More Than Just Inadequate Facilities for Breaks

Early signs of dehydration, such as headaches, are not unusual in the working population. Even slight deficiencies of water intake may have negative effects on both health and performance. However, little is known about work-related fluid intake. We expect the daily experience of interruptions to distract from perceived thirst, resulting in reduced daily fluid intake. This effect may be more pronounced when the workload is generally less predictable due to the assignment of tasks that are beyond the definition of the worker's professional role (unreasonable tasks). Data were gathered from 29 female service employees across five workdays. Multilevel analyses revealed daily work interruptions to be negatively associated with fluid intake, especially when there were frequent unreasonable task-assignments. Results suggest that interruptions at work might reduce daily fluid intake. However, adequate allocation of tasks by managers can protect employees against insufficient drinking.

Alcohol's Effects on Pair-Bond Maintenance in Male Prairie Voles

Alcohol abuse can have devastating effects on social relationships. In particular, discrepant patterns of heavy alcohol consumption are associated with increased rates of separation and divorce. Previous studies have attempted to model these effects of alcohol using socially monogamous prairie voles. These studies showed that alcohol consumption can inhibit the formation of pair bonds in this species. While these findings indicated that alcohol's effects on social attachments can involve biological mechanisms, the formation of pair bonds does not properly model long-term human attachments. To overcome this caveat, this study explored whether discordant or concordant alcohol consumption between individuals within established pairs affects maintenance of pair bonds in male prairie voles. Male and female prairie voles were allowed to form a pair bond for 1 week. Following this 1-week cohabitation period, males received access to 10% continuous ethanol; meanwhile, their female partners had access to either alcohol and water or just water. When there was a discrepancy in alcohol consumption, male prairie voles showed a decrease in partner preference (PP). Conversely, when concordant drinking occurred, males showed no inhibition in PP. Further analysis revealed a decrease in oxytocin immunoreactivity in the paraventricular nucleus of alcohol-exposed males that was independent of the drinking status of their female partners. On the other hand, only discordant alcohol consumption resulted in an increase of FosB immunoreactivity in the periaqueductal gray of male voles, a finding suggesting a potential involvement of this brain region in the effects of alcohol on maintenance of pair bonds. Our studies provide the first evidence that alcohol has effects on established pair bonds and that partner drinking status plays a large role in these effects.

Sweetened ethanol drinking during social isolation: enhanced intake, resistance to genetic heterogeneity and the emergence of a distinctive drinking pattern in adolescent mice

With its ease of availability during adolescence, sweetened ethanol ('alcopops') is consumed within many contexts. We asked here whether genetically based differences in social motivation are associated with how the adolescent social environment impacts voluntary ethanol intake. Mice with previously described differences in sociability (BALB/cJ, C57BL/6J, FVB/NJ and MSM/MsJ strains) were weaned into isolation or same-sex pairs (postnatal day, PD, 21), and then given continuous access to two fluids on PDs 34-45: one containing water and the other containing an ascending series of saccharin-sweetened ethanol (3-6-10%). Prior to the introduction of ethanol (PDs 30-33), increased water and food intake was detected in some of the isolation-reared groups, and controls indicated that isolated mice also consumed more 'saccharin-only' solution. Voluntary drinking of 'ethanol-only' was also higher in a subset of the isolated groups on PDs 46-49. However, sweetened ethanol intake was increased in all isolated strain × sex combinations irrespective of genotype. Surprisingly, blood ethanol concentration (BEC) was not different between these isolate and socially housed groups 4 h into the dark phase. Using lickometer-based measures of intake in FVB mice, we identified that a predominance of increased drinking during isolation transpired outside of the typical circadian consumption peak, occurring ≈8.5 h into the dark phase, with an associated difference in BEC. These findings collectively indicate that isolate housing leads to increased consumption of rewarding substances in adolescent mice independent of their genotype, and that for ethanol this may be because of when individuals drink during the circadian cycle.

Peers and Obesity during Childhood and Adolescence: A Review of the Empirical Research on Peers, Eating, and Physical Activity

Obesity during childhood and adolescence is a growing problem in the United States, Canada, and around the world that leads to significant physical, psychological, and social impairment. In recent years, empirical research on factors that contribute to the development and maintenance of obesity has begun to consider peer experiences, such as peer rejection, peer victimization, and friendship. Peer experiences have been theoretically and empirically related to the “Big Two” contributors to the obesity epidemic, eating and physical activity, but there has not been a comprehensive review of the extant empirical literature. In this article, we review and synthesize the emerging theoretical and empirical literatures on peer experiences in relation to: (a) eating (food consumption and food selection); and (b) physical activity, during childhood and adolescence. A number of limitations and issues in the theoretical and empirical literatures are also discussed, along with future research directions. In conclusion, we argue that the involvement of children and adolescents’ peer networks in prevention and intervention efforts may be critical for promoting and maintaining positive behavioral health trajectories.

Social partners prevent alcohol relapse behavior in prairie voles

There is robust evidence for a protective role of interpersonal factors such as social support on alcohol relapse, but research on the mechanisms that social factors may be acting on to effectively protect individuals against relapse is lacking. Prairie voles are highly social, monogamous rodents that freely self-administer ethanol in high amounts, and are a useful model for understanding social influences on alcohol drinking. Here we investigated whether prairie voles can be used to model social influences on relapse using the alcohol deprivation effect, in which animals show a transient increase in ethanol drinking following deprivation. In Experiment I, subjects were housed alone during four weeks of 24-h access to 10% ethanol in a two-bottle choice test. Ethanol was then removed from the cage for 72 h. Animals remained in isolation or were then housed with a familiar same-sex social partner, and ethanol access was resumed. Animals that remained isolated showed an increase in ethanol intake relative to pre-deprivation baseline, indicative of relapse-like behavior. However, animals that were socially housed did not show an increase in ethanol intake, and this was independent of whether the social partner also had access to ethanol. Experiment II replicated the alcohol deprivation effect in a separate cohort of isolated animals. These findings demonstrate that prairie voles display an alcohol deprivation effect and suggest a 'social buffering' effect of relapse-like behavior in the prairie vole. This behavioral paradigm provides a novel approach for investigating the behavioral and neurobiological underpinnings of social influences on alcohol relapse.

The role of familiarity on modeling of eating and food consumption in children

This study investigates the effects of peer and sibling influence on the cookie intake of normal-weight children. A total of 44 children (24 girls and 20 boys) aged 5-11 participated in this study. Children played a sorting task while being exposed to a large amount of cookies. Children were tested alone or with an unfamiliar peer or with a sibling. Results indicated that the social condition was related to the participants' energy intake. Children eating with their siblings ate more cookies than did children eating with strangers and also consumed more cookies than did children eating alone. This pattern of results is consistent with previous research in adults indicating that familiarity between co-eaters influence how much one choose to eat. Furthermore, the degree of intake matching was extremely high among strangers, but low and not statistically significant in dyads of siblings. We conclude that matching effect is not ubiquitous and that familiarity affects the level of matching of eating in children.

Time of day alters long-term sensitization to cocaine in rats

To test the hypothesis that time of day influences the locomotor effects of cocaine in rats, we measured short- and long-term sensitization to cocaine at five different Zeitgeber times (ZT). Short-term sensitization was expressed equally at all ZTs tested. Long-term sensitization was expressed only at dark onset, suggesting a possible influence of melatonin. Exogenous melatonin given immediately before cocaine challenge slightly enhanced long-term sensitization. Taken together, the present results support a time-of-day influence on locomotor sensitization to cocaine.

Exploring psychological benefits associated with moderate alcohol use: a necessary corrective to assessments of drinking outcomes?

The aim of this paper is to identify positive psychological concomitants of moderate alcohol consumption. Current research and public-health perspectives on alcohol emphasize harms disproportionately relative to benefits. The major exception is research establishing beneficial effects of moderate drinking on cardiovascular health and overall mortality. In addition, much observational and experiential data suggest the widespread prevalence of positive drinking experiences. This paper is one of the first attempts since 1985 to codify such benefits in epidemiological terms. Methodological difficulties in accomplishing this include defining moderate drinking, controlling for confounding variables, and establishing causality. Nonetheless, evidence of psychological benefits has been found in experimental, observational, interview, self-report, correlational, and some prospective research. These positive findings are in the areas of subjective health, mood enhancement, stress reduction, sociability, social integration, mental health, long-term cognitive functioning, and work income/disability. Problem drinkers and alcoholics also seek mood and other benefits from alcohol, but are more likely to drink to counteract negative feelings and to support their egos than are social drinkers. It is as yet impossible to determine to what extent moderate alcohol consumption causes positive psychological outcomes and to what extent it is part of a complex pattern of mutually reinforcing variables.

Characterization of cocaine self-administration and pharmacokinetics as a function of time of day in the rat

Two experiments examined the influence of time of day on the intravenous self-administration of cocaine and its associated pharmacokinetic profile in male Sprague-Dawley rats. In both experiments, individual rats were randomly assigned to experimental groups (n = 6/group) according to four selected times of day, 0100, 0700, 1300, and 1900 h, during which experimental procedures were conducted. In both experiments, rats were maintained under a 12 L:12 D ambient lighting cycle, with lights on at 0600 h. Training and testing was thus conducted either 1 (0700, 1900) or 7 (1300, 0100 h) hours into the light and dark phases. In Experiment 1, characteristics of cocaine self-administration across a behaviorally active dose range were assessed. Statistically significant differences were observed in the rates and patterns of self-administration across the four experimental groups, most notably characterized by an apparent shift in the dose of cocaine, which engendered peak rates of responding. Specifically, groups tested at 0100 and 1300 h appeared to exhibit enhanced sensitivity to the reinforcing properties of low-dose cocaine relative to groups tested at 0700 and 1900 h. The observed differences in apparent sensitivity of experimental subjects to low-dose cocaine were not related in any simple way to ongoing patterns of general locomotor activity, and were not accompanied by corresponding variance in the pharmacokinetic profiles of cocaine when assessed over 1 h following an intravenous infusion (1.8 mg/kg) at each of the four sampling periods noted above.

Inheritance of premeal stomach content influences on food intake in free living humans

The heritability of the before-meal stomach content effects on food intake was investigated with 110 identical and 102 fraternal same-sex and 53 fraternal mixed-gender adult twin pairs who were paid to maintain 7-day food intake diaries. From the diary reports, the total and meal intakes of food energy and the amounts of the macronutrients ingested were estimated. A simple computer model of stomach emptying was used to estimate the contents of the stomach at the beginning and end of the meals. Linear structural modeling was applied to investigate the nature and degree of genetic and environmental influences and revealed significant genetic influences on the amount of food energy and macronutrients estimated to be present in the stomach at the beginning and end of meals. However, these influences were found to be secondary to genetic influences on overall intake and meal size such that when these were considered in the model the heritabilities for stomach contents vanished. The genes were also found to affect the magnitude of the negative correlations between the before meal stomach contents and the amounts of nutrients ingested, and the magnitude of the negative slope of the best-fitting regression line between before meal stomach contents and meal size. These results suggest that although the amount in the stomach found at meal time is only affected indirectly by the genes, the impact of the content of the stomach on the amount ingested is to some extent inherited. This suggests that responses to internal stimuli are influenced by the genes and become part of the total package of genetically determined physiological and psychological processes that regulate energy balance.

Social facilitation of food intake is mediated by meal duration

The effect of the number of others present on the amount of food eaten was investigated in the Netherlands by studying spontaneous meal size in 50 free-living young males and females. Subjects recorded food consumption, number of others present, hunger, taste of the food, food availability, and atmosphere at each eating or drinking moment for four (n = 30) or seven consecutive days (n = 20). The results of the study with four and the study with seven recording days were comparable. The mean Pearson within-person correlation coefficient between the number of other present and meal size was 0.24 (n = 50, p < 0.05). This correlation was significant for breakfast (0.40, p < 0.05) and snacks (0.18, p < 0.05), but not for lunch (r = 0.19, p > 0.05) and dinner (r = 0.15, p > 0.05). A path analysis showed no direct effect of the number of others on meal size, but revealed that social facilitation of spontaneous meal size was mediated by meal duration.

Lunar rhythms of the meal and alcohol intake of humans

Lunar variations in the nutrient intakes and the meal patterns of humans were investigated by reanalyzing the data previously collected by paying 694 adult humans to maintain a 7-day diary of everything they ate, when they ate it, and their subjective state of hunger. A small but significant lunar rhythm of nutrient intake was observed with an 8% increase in meal size and a 26% decrease in alcohol intake at the time of the full moon relative to the new moon. This effect was present for meals ingested either during the daytime or the evening, indicating that nocturnal illumination level was not the critical variable. The results suggest that there is a true internal lunar rhythm which influences nutrient intakes of normal humans free-living in their natural environments.

Alcohol and the brain: setting the benefit/risk balance

This article reviews the literature and presents some unpublished data on the CNS effects of alcohol at doses not producing tolerance and dependence. The available evidence indicates that the effect of low doses of ethanol may qualitatively differ from those produced in animal models mimicking alcoholism. For example, rats exposed for two months to alcohol in drinking water at a concentration (3%) not inducing tolerance or dependence, as assessed by lack of withdrawal signs upon treatment suspension, appear to be less stressed in the two-way avoidance-learning tests. Accordingly, the treated rats perform better and learn faster than sucrose-fed controls, while this behavior is disrupted by high levels of ethanol intake. These initial observations suggest that discontinuity may exist between the effects of low and high doses of this substance and underscore the need to expand research on the effects of alcohol on the CNS to include the bottom end of the dose-response curve.

Aversive attributes of ethanol can be attenuated by dyadic social interaction in the rat

Forty-eight male Sprague-Dawley rats were conditioned with either water or 4 g/kg ethanol in a standard drug place-learning task. In addition to the drug treatment, the opportunity for social interaction with either a sober or intoxicated conspecific was varied across groups (N = 8 rats/group). Ethanol produced a robust conditioned place aversion. The opportunity for dyadic social interaction with either a sober or intoxicated cohort attenuated the aversive attributes of ethanol. However, the initial preference scores did not significantly shift in water-conditioned rats in isolation or given access to either a sober or intoxicated cohort. These data are similar to clinical reports and suggest that social factors can influence the aversive affective properties of ethanol.

Tobacco abstinence, smoking cues, and the reinforcing value of smoking

One definition of the reinforcing value of a drug is the degree to which an organism will work to obtain it. Male and female smokers (n = 8 each) engaged in a task involving concurrent schedules of reinforcement for responding to receive cigarette puffs versus money on four occasions, following overnight abstinence versus no abstinence and in the presence of a lit cigarette (smoking "cue") or with no cigarette (2 x 2 design). Reinforcement schedule for puffs ranged from variable ratio 4 (VR4) to VR32, with schedule order during the first five trials (VR4 first, VR32 first) counterbalanced and repeated in reverse sequence during the second five trials. Schedule for money remained at VR4 during all trials. Results indicated significantly greater responding for puffs after overnight abstinence and in the presence of the smoking cue, although effect of the cue was specific to the "leaner" VR schedules (VR16, VR32). Unexpectedly, not only was reinforcement schedule for puffs a significant determinant of responding, but the order of these schedules (i.e., VR4 first vs. VR32 first) produced a significant overall difference in responding for puffs, especially in the presence of the cue. There was no difference in responding between males and females. These findings indicate that the reinforcing value of smoking is increased by overnight abstinence, the presence of a lit cigarette under lean reinforcement conditions, and the order in which reinforcement schedules are presented.

A twin study of genetic and environmental influences on the intake of fluids and beverages

The heritability of fluid and beverage intake was investigated with 109 identical and 86 fraternal adult twin pairs who were paid to maintain 7-day diaries of everything they either ate or drank. Both classical analysis of heritability and linear structural modeling revealed that the amount of fluids ingested daily or in bouts is strongly influenced by heredity in males and by familial environment in females. This was true for the total amount of water ingested, regardless of source, the amount of fluid ingested in excess of digestive requirements, and the amount ingested in the form of drinks. Linear structural modeling revealed that these influences act primarily on the overall total intake of fluids and affect drink fluid intake only indirectly. Significant influences of the genes and the environment were also found on the ingestion of particular beverages, independent of the effects of age and the total intake of fluids. In particular, significant genetic influences were identified on the intake of alcohol, sugared soda, coffee, and milk, and significant familial environmental influences on the intake of diet soda and fruit juice. These results suggest that both the amounts and the types of fluids ingested are complexly influenced by heredity and the environment, depending upon the gender of the individual and the type of beverage investigated.

The caloric demand of lactation does not alter spontaneous meal patterns, nutrient intakes, or moods of women

The regulation of food and fluid intake in lactating women was examined by comparing maternal intake during lactation, 6 weeks postpartum, to intake in two groups of nonpregnant, nonlactating women. All subjects completed a questionnaire and then filled out a food-intake diary for seven consecutive days. Lactating women did not differ from body weight-matched, nonlactating controls in their total daily intakes or their meal patterns. However, they consumed a significantly smaller percentage of the recommended dietary allowances (RDA) per day than did their nonlactating counterparts. Lactating women were also significantly more calm both pre- and postmeal than were either of the control groups. These results indicate that the lactating women, at 6 weeks postpartum, did not increase their intake to compensate for the caloric demands of lactation. This may indicate that the lactating women catabolize weight gained during pregnancy faster than accounted for in the RDA, or that lactating women increase their metabolic efficiency.

The effects of the spontaneous ingestion of particular foods or beverages on the meal pattern and overall nutrient intake of humans

The influence of the ingestion of particular beverages and foods on the overall nutrient intakes and meal patterns of humans was investigated by paying 323 adults to maintain 7-day diaries of everything they ingested, time of ingestion, and subjective and social conditions. Ingestion of noncaloric beverages, diet sodas, and coffee or tea, were associated with low overall intakes but were not found to influence the amount eaten over the course of the day or in individual meals. Fifteen different caloric containing drink or food types were found, in general, to add to the total calories ingested in meals or over the day without displacing calories ingested in other forms. The results indicate that individual foods or beverages are ingested independent of other constituents and that intake within meals or over the entire day is elastic and readily influenced by nonregulatory factors.

Genetic influences on daily intake and meal patterns of humans

The heritability of nutrient intake was investigated with 109 identical and 86 fraternal adult twin pairs who were paid to maintain 7-day food intake diaries. Both classical analysis of heritability and linear structural modeling revealed significant additive genetic influences on body size, height and weight, and body fatness (body-mass index). Significant heritabilities were also found for the amount of food energy ingested daily, as well as its macronutrient, alcohol, and water content. Linear structural modeling analysis showed that 65% of the variance in energy intake was attributable to heredity. In addition, the pattern of intake, meal frequency, size, and meal macronutrient, alcohol, and water composition, were also found to have strong heritabilities. Linear structural modeling indicated that 44% of the variance in meal frequency and 65% of the variance in meal size was attributable to heredity. However, shared, familial environment had no significant impact on the levels or pattern of intake in adulthood. These results indicate that not only body size but also the pattern and amounts of nutrients ingested by humans in natural environments are strongly influenced by the immediate environment and heredity, but not at all by the familial environment.

Effects of alcohol abstinence on spontaneous feeding patterns in moderate alcohol consuming humans

It has previously been found through observational techniques that moderate alcohol consumers tend to add alcohol calories to their diets without displacing macronutrient calories. The present investigation was an active manipulation of alcohol consumption to test for causation by instructing subjects to refrain from alcohol for five days. Twenty-five moderate alcohol consumers, identified with the Michigan Alcoholism Screening Test, were asked to complete a food intake diary for ten consecutive days during which they refrained from drinking any alcoholic beverages for either the first five days or the last five days. The subjects recorded in a diary everything they either ate or drank, the time at which the meal began and ended, their subjective state before and after the meal, and the number of other people present. Subjects' overall intake of food energy during the alcohol week was significantly higher than during the no alcohol week (2205 vs. 1829 kcal) and meals eaten during the alcohol week contained significantly more food energy than did meals eaten during the no alcohol week (649 vs. 541 kcal). Alcohol added additional calories to the diets without altering any other macronutrient intake. These results could have both health and weight loss implications.

Weekly rhythms of spontaneous nutrient intake and meal pattern of humans

Weekly variations in the nutrient intakes and the meal patterns of humans were investigated by paying 323 adult humans to maintain a 7-day diary of everything they ate, when they ate it, and their subjective states of hunger, depression, and anxiety. A marked weekly rhythm of nutrient intake was observed, with a greater total caloric intake and larger meal sizes on weekends associated with an increase in the duration of the meals and the number of other people present. The number of other people present had both significantly larger univariate correlations with meal size and multivariate Beta coefficients predicting meal size on weekends than on weekdays. The results support a hypothesis that the heightened intake on weekends results from increased social facilitation of intake resultant from a greater number of other people present at weekend meals and a greater flexibility to extend the duration of the meals on weekends.

Seasonal rhythms of human nutrient intake and meal pattern

Seasonal variations in the nutrient intakes and the meal patterns of humans were investigated by paying 315 adult humans to maintain a 7-day diary of everything they ate, when they ate it, and their subjective state of hunger. A marked seasonal rhythm of nutrient intake was observed with increased total caloric intake, especially of carbohydrate, in the fall, associated with an increase in meal size and a greater rate of eating. The subjects rated themselves hungrier at the end of the meal in the fall even though the larger meals resulted in a greater estimated amount of food in the stomach. In the winter and spring there was a strong negative relationship between the amount eaten in the meal and self-rated hunger at the end of the meal. This correlation was absent during the fall. The results suggest that even with modern heating and lighting seasonal rhythmicity of food intake persists in humans and is a major influence on eating that may act by suppressing satiety mechanisms.

The relationship of spontaneous macronutrient and sodium intake with fluid ingestion and thirst in humans

The amount of solid food eaten by humans in spontaneously ingested bouts is the most important determinant of the amount and timing of fluid ingestion. In order to investigate whether this relationship occurred as a result of the osmotic and volumetric effects of the ingested nutrients, analyses were performed on the data obtained from 219 adult humans. They were paid to maintain diaries for 7 days of everything they ingested, the timing and conditions present at the bout, and pre- and postbout self-ratings of subjective thirst. Carbohydrate and protein intake were found to be the dietary constituents that were most highly related to fluid intake and subjective thirst while sodium and fat were found to be either not at all or only weakly related. Carbohydrate and protein intake were found to be positively related to the amount ingested of total fluid, fluid in excess of digestive requirements, and fluid in the form of "drinks," for the amounts ingested in individual bouts, over the entire day, and over the entire week. In addition, carbohydrate and protein intakes were found to be positively related to the reduction in the subjective state of thirst, while negatively related to the level of thirst self-reported at the end of the bout. The results indicate that fluid intake and subjective thirst are influenced by the repleting characteristics of ingested nutrients and not by their depleting effects, suggesting that fluid intake occurs in response to and as an adjunct of food intake, not fluid homeostasis.