Influence of caffeine on the liking of novel-flavored soda in adolescents

Comparing the number of outdoor sugar-sweetened beverage and caffeinated beverage advertisements near schools by school type and school-level economic advantage

INTRODUCTION

Sugar-sweetened beverage and caffeinated beverage consumption are associated with a variety of health issues among youth. Food and beverage marketing has been shown to affect youth's preferences, purchases, and consumption of marketed products. Previous research suggests that outdoor food and beverage marketing differs by community demographics, with more advertisements in lower-income communities and near schools. The purpose of this study is to examine the density of sugar-sweetened and caffeinated beverage advertisements near schools by school type (middle vs. high school) and by school-level SES.

METHODS

Data are from the Outdoor Measuring and Evaluating the Determinants and Influence of Advertising (MEDIA)study, which documented and described all outdoor food and beverage advertisements near 47 middle and high schools in 2012. Beverage advertisements were categorized as: sugar-sweetened/caffeinated, sugar-sweetened/non-caffeinated, non-sugar-sweetened/caffeinated, or non-sugar-sweetened/non-caffeinated. Schools were categorized by type (middle vs high) and by SES as determined by the percentage of students qualifying for free or reduced-price lunch. Bootstrapped non-parametric Mann-Whitney U tests compared the number of advertisements in each category by school type and school-level SES (higher vs lower).

RESULTS

Compared to schools with higher SES, schools with lower SES had significantly more advertisements for sugar-sweetened/non-caffeinated beverages (Medianlow = 28.5 (IQR 17-69), vs Medianhigh = 10.5 (IQR 4-17) (p = 0.002)., sugar-sweetened non-caffeinated (Medianlow = 46 (IQR 16-99) vs Medianhigh = 13.5 (IQR 6-25), p = 0.002), -sugar-sweetened caffeinated (Medianlow = 12 (IQR 8-19) vs Medianhigh = 6 (IQR 2-8), p = 0.000), and non-sugar-sweetened non-caffeinated (Medianlow = 30 (IQR 13-65) vs Medianhigh = 14 (IQR 4-29), p = 0.045).There were no significant differences by school type.

CONCLUSION

This study adds to the literature demonstrating pervasive marketing of unhealthy products in lower-income communities. Disproportionate exposure to sugar-sweetened and caffeinated beverage advertisements in lower-income communities may contribute to the disparities in associated health outcomes by economic status.

Caffeine-based flavor preference conditioning in the rat

The massive consumption of caffeine-containing beverages has prompted many studies involving human participants that have obtained caffeine-based increases in liking for a flavor. However, few studies have succeeded in obtaining caffeine-based flavor preference learning in rats. The main aim of the present study was to examine the conditions under which such learning can be detected. Three experiments differed mainly in terms of the base solution to which caffeine was added. Using a base of maltodextrin and saccharin, Experiment 1 found modest increases in flavor preferences in both food- and fluid-restricted rats. Experiment 2 found a strong caffeine-based flavor preference when water, but not saccharin, was used as the base. Whereas the first two experiments used a within-subject design, in which one flavor was paired with caffeine and a second flavor was not, Experiment 3 used a between-subject design with fluid-restricted rats given almond-flavored water containing caffeine in the Paired condition but not in the Unpaired condition; caffeine-based flavor preference learning was again found. In Experiments 1 and 2 post-conditioning exposure to the flavor alone produced a decrease in preference. In summary, the main achievements of this study were to extend the conditions under which caffeine-based flavor preferences can be detected in rats and demonstrate that such learned preferences are subject to extinction.

Intravenous and oral caffeine self-administration in rats

Caffeine is widely consumed for its psychoactive effects worldwide. No pre-clinical study has established reliable caffeine self-administration, but we found that caffeine can enhance the reinforcing effects of non-drug rewards. The goal of the present studies was to determine if this effect of caffeine could result in reliable caffeine self-administration. In 2 experiments rats could make an operant response for caffeine delivered in conjunction with an oral 'vehicle' including saccharin (0.2% w/v) as a primary reinforcer. In Experiment 1, intravenous (IV) caffeine infusions were delivered in conjunction with oral saccharin for meeting the schedule of reinforcement. In control conditions, oral saccharin alone or presentations of IV caffeine alone served as the reinforcer. In Experiment 2, access to caffeine was provided in an oral vehicle containing water, decaffeinated instant coffee (0.5% w/v), or decaffeinated coffee and saccharin (0.2%). The concentration of oral caffeine was then manipulated across testing sessions. Oral and IV caffeine robustly increased responding for saccharin in a manner that was repeatable, reliable, and systematically related to unit IV dose. However, the relationship between oral caffeine dose and operant behavior was less systematic; the rats appeared to titrate their caffeine intake by reducing the consummatory response (drinking) rather than the appetitive response (lever pressing). These studies establish reliable volitional caffeine self-administration in rats. The reinforcement enhancing effects of caffeine may help to explain widespread caffeine use by humans, who ingest caffeine in complex vehicles with reinforcing properties.

Caffeine release and absorption from caffeinated gums

The objectives of this study were to estimate the impact of chewing time on caffeine release from gum and to understand caffeine pharmacokinetics. Caffeine release increased with chewing time (2 min < 5 min < 10 min). Furthermore, two plasma caffeine concentration peaks were observed suggesting that caffeine absorption occurs both through the oral mucosa and gastrointestinal tract. This is of practical relevance to maximise caffeine doses and to synchronise effort with peak caffeine concentration.

Review: Trends, Safety, and Recommendations for Caffeine Use in Children and Adolescents

OBJECTIVE

Caffeine use is common in children and adolescents, but the recommendations for safe consumption are based on decades-old data collected exclusively in adults. Increased availability of caffeine-containing products and a concerted marketing effort aimed at children and adolescents, has increased interest in understanding the physiological, behavioral, and psychological effects of caffeine within this population. This manuscript provides a review of the literature concerning trends and safety of ingested caffeine in children and adolescents.

METHOD

A search of the National Library of Medicine database was conducted using the terms caffeine, children, adolescents, and safety, in addition to tailored searches on specific topics using combinations of search terms such as energy drinks, cardiovascular, mood, cognitive, mental health, sleep, and regulations.

RESULTS

The majority of the literature reviewed here suggests that typical, moderate caffeine consumption in children and adolescents is relatively safe, but that higher doses of caffeine consumption (>400 mg) can cause physiological, psychological, and behavioral harm, in particular in subgroups of children, such as those with psychiatric or cardiac conditions. More attention is being paid to the potential adverse effects of both acute and chronic caffeine use, and additional regulations surrounding the sale and marketing of highly caffeinated beverages are now being considered.

CONCLUSION

More research is needed to fill in gaps in our knowledge, including understanding the relationship between caffeine use and initiation of other substances, such as cigarettes, alcohol, or marijuana, identifying individuals at risk for caffeine toxicity, and developing harm-reduction strategies.

Reinforcing Value of Caffeinated and Noncaffeinated Beverages After Acute Exposure in Children and Adolescents

Background: When caffeine is added to beverages, it increases beverage liking and the relative reinforcing value (RRV) of these beverages after repeated exposure. The purpose of this study was to test the hypothesis that a single acute exposure to caffeine increases liking and motivation to consume sugar-sweetened beverages (SSBs) relative to placebo. Methods: Participants were children ages 8-9 years (n = 36) and adolescents ages 15-17 years (n = 41) with an approximately equal number of boys and girls. A double-blind, placebo-controlled crossover study was conducted where participants sampled a SSB containing caffeine (1 and 2 mg/kg) on one visit and placebo (quinine 0.01 and 0.02 mg/kg) on a second visit day and then, on a third visit, played a computer game to earn points for the beverages and rated liking and taste sensations. They returned to the laboratory after a 1-week washout and had the alternate dose combination. Results: Acute exposure to the higher dose of caffeine increased the RRV of the SSB relative to placebo, but only when that dose was presented in the first week and only in female participants. The liking of the caffeine-containing SSB at the higher dose was lower than the placebo at all time points. Conclusions: These data suggest that a single exposure to a caffeinated SSB can impact its RRV and liking, but only under certain conditions and only in females. This supports previous work suggesting that caffeine can increase desire to consume SSB.

The Taste of Caffeine

Many people avidly consume foods and drinks containing caffeine, despite its bitter taste. Here, we review what is known about caffeine as a bitter taste stimulus. Topics include caffeine's action on the canonical bitter taste receptor pathway and caffeine's action on noncanonical receptor-dependent and -independent pathways in taste cells. Two conclusions are that (1) caffeine is a poor prototypical bitter taste stimulus because it acts on bitter taste receptor-independent pathways, and (2) caffeinated products most likely stimulate "taste" receptors in nongustatory cells. This review is relevant for taste researchers, manufacturers of caffeinated products, and caffeine consumers.

Effects of acute and chronic caffeine on risk-taking behavior in children and adolescents

Consumption of caffeinated beverages is associated with increased risk-taking behavior. The purpose of this study was to determine if acute caffeine administration influences risk-taking behavior in a dose-dependent manner. Participants were pre- (ages 8-9) and post-pubertal (ages 15-17) children who visited the laboratory three times and consumed a beverage containing 0, 1, or 2 mg/kg of caffeine. Thirty minutes later, participants completed the balloon analogue risk task (BART), the Iowa gambling task (IGT), and a delay discounting task. The number of balloons exploded on the BART task was significantly increased after 2 mg/kg of caffeine in moderate caffeine consumers, but was decreased after 2 mg/kg of caffeine in high caffeine consumers. There were no main effects of caffeine dose on the delay discounting task or on the IGT. Post-pubertal participants showed reduced delay discounting compared with pre-pubertal participants. Finally, average daily caffeine use was significantly, positively correlated with scores on a risk-taking questionnaire. These data suggest that caffeine dose-dependently influences decision making and risk taking. More research is needed to determine the mechanism of this difference as well as the extent to which sex and pubertal phase influence these relationships.

Desire to Drink Alcohol is Enhanced with High Caffeine Energy Drink Mixers

BACKGROUND

Consumption of alcohol mixed with energy drinks (AmED) has been associated with a variety of risks beyond that observed with alcohol alone. Consumers of AmED beverages are more likely to engage in heavy episodic (binge) drinking. This study was to investigate whether the consumption of high caffeine energy drink mixers with alcohol would increase the desire to drink alcohol compared to the same amount of alcohol alone using a double-blind, within-subjects, placebo-controlled study design.

METHODS

Participants (n = 26) of equal gender who were social drinkers attended 6 double-blind dose administration sessions that involved consumption of alcohol and energy drinks, alone and in combination. On each test day, participants received 1 of 6 possible doses: (i) 1.21 ml/kg vodka + 3.63 ml/kg decaffeinated soft drink, (ii) 1.21 ml/kg vodka + 3.63 ml/kg energy drink, (iii) 1.21 ml/kg vodka + 6.05 ml/kg energy drink, (iv) 3.63 ml/kg decaffeinated soft drink, (v) 3.63 ml/kg energy drink, and (vi) 6.05 ml/kg energy drink. Following dose administration, participants repeatedly completed self-reported ratings on the Desire-for-Drug questionnaire and provided breath alcohol readings.

RESULTS

Alcohol alone increased the subjective ratings of "desire for more alcohol" compared to placebo doses. Energy drink mixers with the alcohol increased desire for more alcohol ratings beyond that observed with alcohol alone.

CONCLUSIONS

This study provides laboratory evidence that AmED beverages lead to greater desire to drink alcohol versus the same amount of alcohol consumed alone. The findings are consistent with results from animal studies indicating that caffeine increases the rewarding and reinforcing properties of alcohol.

Subjective Responses to Caffeine Are Influenced by Caffeine Dose, Sex, and Pubertal Stage

Background: Our previous work has shown that there are sex differences in subjective responses to acute caffeine administration in adolescents. The purpose of this study was to determine if these sex differences are dependent on pubertal development. Materials and Methods: We examined subjective responses before and after administration of 0, 1, and 2 mg/kg of caffeine in pre- and postpubertal boys and girls (n = 112). In addition, we examined differences in subjective responses to acute caffeine in both the luteal and follicular phases of the menstrual cycle in postpubertal girls. Results: Caffeine at both doses resulted in greater changes in responses on the Addiction Research Center Inventory and the Brief Assessment of Mood States compared with placebo. Girls reported greater increases from baseline to peak in feeling different and liking the feeling than boys after 2 mg/kg of caffeine regardless of pubertal stage. Postpubertal girls also had a greater decrease from baseline in reports of feeling high and greater increases from baseline in reports of wanting more than postpubertal males. Finally, girls had greater changes (both increases and decreases) in responses on the Brief Mood Questionnaire when in the follicular phase compared with the luteal phase. This was also true for reports of feeling high and feeling different on the Drug Effects Questionnaire. None of these effects varied as a function of usual caffeine use, suggesting that differences are not the result of tolerance or sensitization. Conclusions: These results suggest that subjective responses to caffeine emerge before puberty, but sex differences may be strengthened after pubertal development.

Combined alcohol and energy drink use: hedonistic motives, adenosine, and alcohol dependence

Consumption of alcohol mixed with energy drinks (AmED) has been associated with both short- and long-term risks beyond those observed with alcohol alone. AmED use has been associated with heavy episodic (binge) drinking, risky behaviors, and risk of alcohol dependence. Laboratory research has demonstrated that AmED beverages lead to greater motivation to drink versus the same amount of alcohol consumed alone. However, the reason consumers find AmED beverages particularly appealing has been unclear. A recent report by Droste and colleagues (Alcohol Clin Exp Res 2014; 38:2087-2095) is the first study to investigate motivations related to AmED consumption and to determine which motives predict AmED consumption patterns, experience of drinking-related harms, and risk of alcohol dependence. The findings of this study significantly enhance our understanding of why AmED consumption is related to the risk of alcohol dependence and change our understanding of why consumers choose AmED beverages. The authors report that hedonistic motives strongly predicted AmED use and the harms associated with use. While intoxication-reduction motives predicted self-reported accidents and injuries, these motives did not predict AmED consumption patterns and risk of dependence. The risk of alcohol dependence may arise from repeated experiences when drinking alcohol is more pleasurable when energy drinks are consumed with the alcohol. This commentary will focus on why energy drinks might increase the rewarding properties of alcohol in social drinkers. In addition, discussion is provided explaining why more research on the neurotransmitter, adenosine, may actually inform us about the mechanisms contributing to the development of alcohol dependence.

Caffeine increases sugar-sweetened beverage consumption in a free-living population: a randomised controlled trial

Excessive sugar-sweetened beverage (SSB) consumption has been associated with overweight and obesity. Caffeine is a common additive to SSB, and through dependence effects, it has the potential to promote the consumption of caffeine-containing foods. The objective of the present study was to assess the influence that caffeine has on the consumption of SSB. Participants (n 99) were blindly assigned to either a caffeinated SSB (C-SSB) or a non-caffeinated SSB (NC-SSB) group. Following randomisation, all participants completed a 9 d flavour-conditioning paradigm. They then completed a 28 d ad libitum intake intervention where they consumed as much or as little of C-SSB or NC-SSB as desired. The amount consumed (ml) was recorded daily, 4 d diet diaries were collected and liking of SSB was assessed at the start and end of the intervention. Participants (n 50) consuming the C-SSB had a daily SSB intake of 419 (sd 298) ml (785 (sd 559) kJ/d) over the 28 d intervention, significantly more than participants (n 49) consuming the NC-SSB (273 (sd 278) ml/d, 512 (sd 521) kJ/d) (P< 0·001). A trained flavour panel (n 30) found no difference in flavour between the C-SSB and NC-SSB (P>0·05). However, participants who consumed the C-SSB liked the SSB more than those who consumed the NC-SSB (6·3 v. 6·0 on a nine-point hedonic scale, P= 0·022). The addition of low concentrations of caffeine to the SSB significantly increases the consumption of the SSB. Regulating caffeine as a food additive may be an effective strategy to decrease the consumption of nutrient-poor high-energy foods and beverages.

Can energy drinks increase the desire for more alcohol?

Energy drinks, the fastest growing segment in the beverage market, have become popular mixers with alcohol. The emerging research examining the use of alcohol mixed with energy drinks (AmEDs) indicates that the combination of caffeine-containing energy drinks with alcohol may be riskier than the use of alcohol alone. The public health concerns arising from AmED use are documented in different research domains. Epidemiologic studies reveal that the consumption of AmEDs is frequent among young and underage drinkers, demographic groups that are more likely to experience the harms and hazards associated with alcohol use. In addition, for all consumers, elevated rates of binge drinking and risk of alcohol dependence have been associated with AmED use when compared to alcohol alone. Results from laboratory studies help explain why AmED use is associated with excessive intake of alcohol. When an energy drink (or caffeine) is combined with alcohol, the desire (or urge) to drink more alcohol is more pronounced in both humans and animals than with the same dose of alcohol alone. The experience of drinking alcohol appears to be more rewarding when combined with energy drinks. Given that caffeine in other foods and beverages increases preference for those products, further research on AmEDs may elucidate the underlying mechanisms that contribute to alcohol dependence.

Factors that influence the reinforcing value of foods and beverages

Behavioral economic principles state that as the cost of a product increases, purchasing or consumption of that product will decrease. To understand the impact of behavioral economics on ingestive behavior, our laboratory utilizes an operant behavior paradigm to measure how much work an individual will engage in to get access to foods and beverages. This task provides an objective measure of the reinforcing value. We have shown that consumption of the same high fat snack food every day for two weeks reduces its reinforcing value in lean individuals, but increases its reinforcing value in a subset of obese individuals. This increase in the reinforcing value of food predicts future weight gain. Similarly, we have shown that repeated intake of caffeinated soda increases its reinforcing value in boys, but not in girls. This increase in reinforcing value is not related to usual caffeine consumption, but may be associated with positive, subjective effects of caffeine that are more likely to be reported by boys than by girls. Because food and beverage reinforcement relates to real-world consumption, it is important to determine factors that increase or decrease the reinforcing value and determine the consequences of these responses. We are especially interested in determining ways to shift the behavioral economic curve in order to develop novel strategies to decrease the reinforcing value of less healthy snack foods and beverages, such as soda, potato chips and candy and to increase the reinforcing value of healthier foods and beverages, such as water, fruits, and vegetables.

Effect of Caffeinated Soft Drinks on Salivary Flow

BACKGROUND

Soft drinks containing caffeine have been associated with more aggressive forms of dental decay. Cariogenicity of caffeinated soft drinks may be attributed to the effect of caffeine on salivary flow. This study assessed whether caffeinated soft drinks produced short-term oral dryness in healthy adults.

METHODS

The authors collected saliva on two separate days from 35 participants before and one hour after drinking a soft drink. On one of the days the soft drink was caffeinated and on the other day it was not. Saliva collection involved 15 minutes unstimulated whole saliva, 5 minutes paraffin-stimulated whole saliva, and 10 seconds labial minor salivary gland output.

RESULTS

Unstimulated and stimulated flow rates slightly increased and minor gland output slightly decreased one hour after the soft drink consumption regardless of caffeine content. These changes were not statistically significant (two-period two-treatment crossover trial using two-stage Grizzle model, p>0.05). A linear mixed model statistic did not show the caffeine effect on salivary flow rate.

CONCLUSIONS

Caffeinated soft drink consumption had no significant effect on salivary flow rate after one hour by any of the three measures employed in this study. Caffeine's contribution to the cariogenicity of soft drinks is likely by centrally-mediated effects on consumption patterns.

Caffeine increases liking and consumption of novel-flavored yogurt

RATIONALE

Caffeine has been shown to increase preference for beverages with which it is paired; however, it is not known if caffeine alters liking for foods with which it is paired indirectly.

OBJECTIVES

The purpose of the current experiment was to test the hypothesis that a caffeinated beverage paired with a novel-flavored yogurt will increase preference for that yogurt compared to one paired with placebo. We also tested the hypothesis that liking would increase more when caffeine was paired with high energy density yogurt.

METHODS

Men and women (n = 62) were randomized to receive a beverage containing placebo (PLA) or caffeine (CAF) and to consume a low (LED) or high energy density (HED), novel-flavored yogurt. Participants rated, ranked, and consumed seven novel-flavored yogurts and then had a target yogurt paired with either PLA or CAF over four consecutive days.

RESULTS

In general, yogurt liking increased over time, the HED yogurt was liked more than the LED yogurt, and yogurt paired with caffeine was liked more than yogurt paired with placebo. Participants showed a significant increase in liking of LED yogurt paired with caffeine compared to those with LED yogurt paired with placebo.

CONCLUSIONS

Caffeine administration may increase liking and consumption of novel-flavored foods, particularly if the food is not highly liked at baseline. This suggests that caffeine pairing may be a way to increase liking of LED foods, such as vegetables and fruit.

Acute and chronic caffeine administration increases physical activity in sedentary adults

Caffeine is a commonly used stimulant thought to have ergogenic properties. Most studies on the ergogenic effects of caffeine have been conducted in athletes. The purpose of this study was to test the hypothesis that caffeine reduces ratings of perceived exertion and increases liking of physical activity in sedentary adults. Participants completed treadmill walking at 60% to 70% of their maximal heart rate at baseline and for 6 subsequent visits, during which half of the participants were given caffeine (3 mg/kg) and half given placebo in a sports drink vehicle. To investigate the potential synergistic effects of acute and chronic caffeine on self-determined exercise duration, participants were rerandomized to either the same or different condition for the last visit, creating 4 chronic/acute treatment groups (placebo/placebo, placebo/caffeine, caffeine/placebo, caffeine/caffeine). Participants rated how much they liked the activity and perceived exertion at each visit. There was a main effect of time on liking of physical activity, with liking increasing over time and an interaction of sex and caffeine treatment on liking, with liking of activity increasing in female participants treated with caffeine, but not with placebo. There was no effect of caffeine on ratings of perceived exertion. Individuals who received caffeine on the final test day exercised for significantly longer than those who received placebo. These data suggest that repeated exposure to physical activity significantly increases liking of exercise and reduces ratings of perceived exertion and that caffeine does little to further modify these effects.