Course:KIN366/ConceptLibrary/ChildhoodCaffeine

From UBC Wiki
Jump to: navigation, search
Movement Experiences for Children
Wiki.png
KIN 366
Section:
Instructor: Dr. Shannon S.D. Bredin
Email: shannon.bredin@ubc.ca
Office:
Office Hours:
Class Schedule:
Classroom:
Important Course Pages
Syllabus
Lecture Notes
Assignments
Course Discussion


Caffeine is crystalline compound and is a stimulant of the central nervous system (Trask, Motherwell, & Jones, 2005). Caffeine is considered to be the most commonly used drug in the world, as adults frequently consume caffeine on daily basis (most commonly in the form of coffee or tea; Nehlig, Daval, Debry, 1992). However, over the past 30 years there has been a rapid influx of caffeine consumption in children (Harnack, Stang, & Story, 1999). This has been the result of the emergence of energy drinks, soft drinks and other non-traditional sources of caffeine in which caffeine is used as an additive (such as ice cream and gum; Temple, 2009). Various corporations, who produce these caffeine-containing products, have targeted children in their marketing campaigns (Temple, 2009). For example, energy drink companies, such as Red Bull, place various advertisements in sports as well as sponsor elite athletes from all over the world (Red Bull, 2015). Many of these athletes serve as role models for children. As a result of this, a significant amount of child athletes may request that their parent’s purchase energy drinks to help them “improve their performance” in their desired sport. This is a pressing issue, as the effects of caffeine consumption in children have been relatively understudied (Temple, 2009). Therefore, parents/guardians need to have a thorough understanding of how caffeine affects children’s development and movement capabilities. Thus, it is important for Parents/Guardians to understand how to monitor/limit caffeine consumption in children.

Caffeine and its potential effects

Caffeine, as previously mentioned, is classified as a stimulant and is commonly used as a supplement to spark the central nervous system (Temple, 2009). Additionally, caffeine has been widely viewed as a diuretic, which is something that causes an increased flow of urine (Temple, 2009). This may cause one to frequently urinate and may lead to dehydration (Temple, 2009). The effects of caffeine will most likely vary from person to person, as each individual will respond differently to caffeine (Nehlig et al., 1992). The primary short-term effect of caffeine consumption in humans is that has been though to increase arousal levels (Barry et. al, 2005; Flaten & Blumenthal, 1999). Additionally, following consumption of moderate dosages, caffeine has been thought to decrease heart rate and increase blood pressure (Bender et al., 1997; Lane and Williams, 1987; Sung et al., 1994; Waring et al., 2003). Furthermore, when taken in moderate amounts, caffeine has been thought to improve an individual’s well-being, concentration, energy, and intellectual performance (Garrett & Griffiths, 1997; Griffiths et al., 1990). As a result of these effects, humans frequently consume caffeine in order to help them function at an optimal level. However, when caffeine is consumed in excessive amounts, it has been thought to cause feelings of anxiety, nausea, fidgeting, and nervousness (Garrett & Griffiths, 1997). Also, frequent consumption of caffeine may facilitate bone loss in people who have low levels of calcium (Barrett-Conner et al., 1994; Harris & Dawson-Hughes, 1994). Additionally, frequent consumption of caffeine may lead to dependence, however, this has not been scientifically proven (Temple, 2009). Regardless, withdrawal symptoms may present in certain individuals who frequently consume caffeine, as a result of not having consumed caffeine for a period of time (Nehlig et al., 1992). These withdrawal symptoms may cause various symptoms such as headaches, fatigue, and irritability (Nehlig et al., 1992).

Sources of Caffeine for Children

Children consume caffeine through a variety of different sources. Many of these sources of caffeine for children are not surprising. Children commonly obtain caffeine through consuming soft drinks/pop, chocolate, energy drinks, etc. However, caffeine can also be found in products that we would typically not suspect caffeine to be present in. Caffeine has been added to various products such as: candy bars, gum, certain flavours of ice cream, chocolate milk, etc. (Temple, 2009). An overview of the quantity of caffeine present in various products is shown below in table 1.

Product Serving Size Amount of Caffeine (mg)
Coca-Cola/Coke Zero 355mL (1 Can) 35
Diet Coke 355mL (1 Can) 47
Dr. Pepper 355mL (1 Can) 41
7up, Sprite, Ginger Ale 355mL (1 Can) 0
MiO Energy ~2.5mL (1 Squirt) 60
Häagen-Dazs Coffee Ice Cream ~119mL 29
5-Hour Energy Drink ~56mL 208
Bang Energy Drink ~473mL 357
Red Bull ~248mL 80
Hersey’s Milk Chocolate Bar ~28g 9
Lindt Dark Chocolate 100g (1 Chocolate Bar) ~ 567(20mg/28g)
Lindt Milk Chocolate 100g (1 Chocolate Bar) ~ 170(6mg/28g)
Kit Kat Bar 46g (1 Chocolate Bar) 5
Jolt Gum 1 Piece 45
Chocolate Ice Cream 50g 2-5
Chocolate Milk 225mL 2-7

(Centre for Science in the Public Interest, 2014; Food and Drug Administration, 2007; Lindt, 2013)

The Potential Effects of Caffeine on Children

It should be mentioned that the size/body weight of children is different compared to that of adults. Thus, it is very important that children are not simply considered small adults, as caffeine will affect children differently compared to adults (Temple, 2009).

Digestion Issues

Following the consumption of caffeine containing products, a small portion of children may develop stomachaches (Kristjansson, Sigfusdottir, Mann, & James, 2014). However, this will vary, as in the majority of cases children do not appear to have any digestion complications (Kristjansson et al., 2014).

Headaches/Migraines

Children, who consume high doses of caffeine, through the consumption of cola drinks, may potentially suffer from daily headaches (Hering-Hanit & Gadoth, 2003). Furthermore, high doses of caffeine may also lead to migraines in children (Hering-Hanit & Gadoth, 2003).

Adverse of affects of energy drinks

Some energy drinks contain almost five times the amount of caffeine that is present in cola drinks (Temple, 2009). In addition to the high amounts of caffeine present in various energy drinks, there also are high amounts of sugar in certain energy drinks (Temple, 2009). While there are high amounts of caffeine and sugar present in some energy drinks, there are additional ingredients present in energy drinks that may be harmful (Seifert, Schaechter, Hershorin, & Lipshultz, 2011). These additional ingredients include taurine, riboflavin, pyridoxine, nicotinamide, other B vitamins, and various herbal derivatives (Aranda & Morlock, 2006). The short and long-term effects of these ingredients in combination with caffeine are not fully known, and thus consumers need to be aware of the risks (Reissig, Strain, & Griffiths, 2009). Furthermore, excessive intakes of energy drinks can lead to serious health issues, including sudden death, especially in children who have heart conditions (Seifert et al., 2011). Finally, frequent and excessive consumption of energy drinks in children may lead to them engaging in various forms of risky behaviour when they are older (i.e. smoking, fighting, drug use, etc.; Miller, 2008). The high amounts of caffeine, that are present in energy drinks, may lead to negative side effects such as nervousness and jitteriness (Garrett & Griffiths, 1997; Griffiths et al. 1990). This may cause a child to become over aroused, and may negatively impact his or her ability to participate in physical activity (Beuter & Duda, 1985).

Limited research on the affects of energy drinks on children

It should be mentioned that there have only been a few studies on the effects of energy drinks on children. Thus future research is required in order to fully understand the affects of energy drinks on children’s health.

Potential benefits/drawbacks toward academic and athletic tasks

Benefits

Children typically consume caffeine as it has been thought of as a way to improve their athletic and academic performance (Temple, 2009). Specifically, caffeine is thought to improve an individual’s sport performance, specifically, improvements in reaction time, as well as perceived exertion and endurance (Temple, 2009). In terms of academic performance, caffeine is thought to improve an individual’s concentration levels (Garrett & Griffiths, 1997).

Drawbacks

High doses of caffeine can potentially cause feelings of nervousness, anxiety, nausea, and jitteriness (Garrett & Griffiths, 1997; Griffiths et al. 1990). These drawbacks can potentially have a negative impact on children’s academic and athletic performance. Additionally, as previously mentioned, caffeine’s diuretic effects may lead to dehydration (Temple, 2009). Thus, this may prove to be detrimental to children’s academic and athletic performance. Furthermore, excessive caffeine consumption may also cause children to become over-aroused, and in turn may cause a decrement in their athletic/academic performance (Beuter & Duda, 1985).

Limited Research on Children

It should be noted that the majority of research on caffeine consumption and athletic/academic performance in children is limited, as the majority of studies have been focused on adults. Thus future research in this area is required in order to have a better understanding of caffeine’s impact on children’s academic and athletic performance.

Effects on sleeping patterns

Caffeine consumption in children may be used as a supplement to negate the effects of a poor sleep (Pollak & Bright, 2003). Parents may provide caffeine-containing products to their child (or the child themselves will consume a caffeine-containing product), in order to increase the child’s wakefulness/alertness during the day. Furthermore, this pattern may further exaggerate poor sleeping patterns, causing an increase in caffeine consumption in children (Goldstein & Shapiro, 1987). Additionally, it has been reported that 10-12 year olds who consume cola and energy drinks, have suffered from sleep disturbances (Kristjansson et al., 2014). As a result of these sleeping disturbances, children’s performance in their desired sport may suffer due to their low levels of alertness.

Increased risk of obesity, type II diabetes, dental caries, and other conditions

Caffeine is commonly consumed by children through sugar-sweetened beverages (e.g. cola drinks, energy drinks, etc.), which has been associated with higher incidences of children who are overweight (Johnson & Kennedy, 2000). Children who frequently consume soda drinks are more likely to develop a preference for sweet-tasting products as opposed to consuming healthier choices (i.e. vegetables, fruits, milk, etc.; Marshall et al., 2005: Temple, 2009). As a result of this, children who consume caffeine in high amounts may be at an increased risk of developing dental caries, becoming obese, and developing other diseases such as type II diabetes (Seifert et al., 2011). Thus, poor dieting may result in children not obtaining the appropriate amount of nutrients and minerals that are required for optimal development (Harnack et al., 1999). This may lead to various complications in the future, such as the development of osteoporosis (Harnack et al., 1999). Furthermore, an overdose on caffeine consumption may even lead to pre-mature death in certain children (Kerrigan & Lindsey, 2005).

The development of these various diseases may further complicate children’s ability to participate in sporting events. The various symptoms, such as fatigue, that are associated with the previously mentioned diseases, may serve as a significant barrier to children participating in physical activity.

Effect on Children with Attention Deficit Hyperactivity Disorder(ADHD)

A significant amount of children take various medications (i.e. stimulants) for Attention Deficit Hyperactivity Disorder (ADHD; Seifert et al., 2011). The combination of caffeine with the ADHD medication may compromise a child’s health (e.g. cardiovascular health; Seifert et al., 2011). Thus, this may lead to further complications to children with ADHD’s ability to participant in physical activity.

Impact on Brain Development

A significant amount of brain development occurs during childhood (Giedd, 1999). Thus, consumption of caffeine at an early age may alter the development of the brain (Giedd, 1999). As a result of this, it may be possible that the consumption of caffeine affects the reinforcing properties of certain types of food and beverages that are associated with caffeine (e.g. sweet-tasting foods; Temple, 2009). This may cause a child to display improper eating habits/poor dieting as an adult, as they may choose sweet foods as opposed to more healthier choices. Furthermore, improper eating habits may lead to various nutrient/mineral deficiencies, and can potentially result in greater occurrences of injuries amongst young children who participate in physical activity (Goulding, 2007).

Addiction/Withdrawal

Addiction

Children may become addicted to caffeine as a result of frequently consuming caffeine-containing products (Temple, 2009). This may be attributed to high amounts of sugar that is present in beverages that children typically consume (such as soda drinks; Temple, 2009). Thus, children may develop a taste preference for soda drinks (containing caffeine), which may end up increasing children’s consumption of caffeine-containing products (Temple, 2009).

Withdrawal

Children may display various withdrawal symptoms, as a result of not consuming caffeine for periods of time (Temple, 2009). These symptoms can appear as irritability, nervousness, headaches, anxiety, sleepiness, fatigue etc., and most likely vary from person to person (Reissig et al., 2009). However, it should be noted that not all habitual drinkers of caffeine will experience withdrawal symptoms, and thus not all children will experience withdrawal symptoms (Hughes et al., 1998).

Summary of the Effects of Caffeine on Movement Experiences

As previously mentioned, there are a variety of potential side effects with caffeine that may have a negative impact on children’s movement capabilities. Both stomachaches and headaches/migraines can cause children to lose their attentional focus toward physical activity. Additionally, following high doses of caffeine, children may become over-aroused (Garrett & Griffiths, 1997; Griffiths et al. 1990). As a result of children becoming over-aroused, children’s performance in their desired sport may decline, or their ability to engage in physical activity may be reduced (Beuter & Duda, 1985). Another factor that may impact children’s movement capabilities is the influence of caffeine on poor sleeping patterns (Kristjansson et al., 2014). These poor sleeping patterns may reduce children’s alertness and performance in the child’s desired sport. Furthermore, some children may develop various diseases, such as obesity and type II diabetes, as a result of consuming sweetened caffeine-containing beverages (Seifert et al., 2011). This may serve as a significant barrier to children participating in physical activity, as it may be difficult to control the various complications that are associated with these diseases (i.e. altered blood sugar levels, mood fluctuations, fatigue, etc.; Plotnikoff, Trinh, Courneya, Karunamuni, & Sigal, 2008). Also, as previously mentioned, children may develop various nutrient or mineral deficiencies as a result of their preference for sweetened foods (Temple, 2009). Thus, this can potentially result in a high rate of injuries (i.e. fractures) amongst young children who participate in physical activity (Goulding, 2007).

Caffeine can also potentially serve as a performance enhancer for sport. Caffeine is thought to improve an individual’s sport performance, specifically, improvements in reaction time, as well as perceived exertion and endurance (Temple, 2009). Additionally, when consumed in moderate amounts caffeine is thought to increase energy levels and concentration, which may help improve children’s movement capabilities and performance in sport (Garrett & Griffiths, 1997; Griffiths et al., 1990).

Regulations

Both Canada and the United States of America have various regulations in place. These regulations are designed to help ensure that consumers are aware of which products contain caffeine, and how much caffeine is present in these products.

Labeling

Since 2011, all energy drinks sold in Canada, are legally classified as food, and thus must be labeled and regulated as food (Health Canada, 2012). As a result of this, all energy drinks are labeled and regulated by the Canadian Food Inspection Agency (Health Canada, 2012). In Canada, the labeling on caffeine-containing products (with the exception of coffee, tea, and chocolate) shows the amount of caffeine (in milligrams) per serving size (Health Canada, 2010). Additionally, caffeinated soft drinks must have clear labeling on the product indicating that the product contains caffeine (Health Canada, 2010).

The U.S. Food and Drug Administration (FDA)

In the United States of America, the FDA has imposed regulations on the maximum amount of caffeine that can be present in cola drinks. The FDA has limited the amount of caffeine in soft drinks to 0.02% (equivalent to approximately 71mg/355mL; Food and Drug Administration, 2014; Reissig et al., 2009). It should be mentioned that the FDA regulations have not been strictly enforced, as it appears that various companies have been ignoring these regulations (Reissig et al., 2009).

Caffeine Consumption in Children: Recommendations- Tips for Parents/Guardians

Health Canada recommends that caffeine consumption for children under 12 years old should be 2.5mg/kg of body weight (Health Canada, 2011). The following is Health Canada’s (2011) specific recommendations for the amount of caffeine consumption in children:

- Children aged 4-6 years old ~ 45mg of caffeine per day (i.e. one 355mL can of soda)

- Children aged 7-9 years old ~ 62.5mg of caffeine per day (i.e. one and a half 355mL cans of soda)

- Children aged 10-12 years old ~ 85mg of caffeine per day (i.e. two 355 mL cans of soda)

As previously mentioned, the effects of caffeine will vary from child to child, and thus each child will be affected differently following the consumption of caffeine (Nehlig et al., 1992). It is recommended that Parents/Guardians follow the Health Canada recommendations; however, Parents/Guardians should analyze the behaviour of the child in order to determine the child’s sensitivity to caffeine. Parents/Guardians can monitor their child’s caffeine consumption by observing the labeling on caffeine-containing products. Also, Parents/Guardians must be aware of the additive ingredients that are in energy drinks, and their potential side effects. Furthermore, Parents/Guardians should limit the consumption of sweetened caffeinated beverages for their children, as there are various health complications that are associated with frequent consumption (Temple, 2009). All of these factors must be considered before Parents/Guardians allow their children to consume caffeine-containing products.

References

Aranda, M., Morlock, G. (2006). Simultaneous determination of riboflavin, pyridoxine, nicotinamide, caffeine and taurine in energy drinks by planar chromatography-multiple detection with confirmation by electrospray ionization mass spectrometry. Journal of Chromatography A, 1131(1), 253–260. doi:10.1016/j.chroma.2006.07.018

Barrett-Conner, E., Chang, J.C., & Edelstein, S.L. (1994). Coffee-associated osteoporosis offset by daily milk consumption: The ranch bernado study. Journal of the American Medical Association, 271(4), 280–283. doi:10.1001/jama.1994.03510280042030

Barry, R.J., Rushby, J.A., Wallace, M.J., Clarke, A.R., Johnstone, S.J., & Zlojutro, I. (2005). Caffeine effects on resting-state arousal. Clinical. Neurophysiology, 116(11), 2693–2700. doi:10.1016/j.clinph.2005.08.008

Bender, A.M., Donnerstein, R.L., Samson, R.A., Zhu, D., & Goldberg, S.J. (1997). Hemodynamic effects of acute caffeine ingestion in young adults. American Journal of Cardiology, 79 (5), 696–699. doi:10.1016/S0002-9149(96)00848-X

Beuter, A., & Duda, J. L. (1985). Analysis of the arousal/motor performance relationship in children using movement kinematics. Journal of Sport Psychology, 7(3), 229-243.

Centre for Science in the Public Interest. (2014). Caffeine Content of Food & Drugs. Retrieved from http://www.cspinet.org/new/cafchart.htm#table_frozen_desserts

Flaten, M.A., & Blumenthal, T.D. (1999). Caffeine-associated stimuli elicit conditioned responses: An experimental model of the placebo effect. Psychopharmacology, 145(1), 105–112. doi:10.1007/978-3-662-44519-8

Food and Drug Administration. (2007). Medicines in my Home: Caffeine and Your Body. Retrieved from http://www.fda.gov/downloads/UCM200805.pdf

Food and Drug Administration. (2014) CFR - Code of federal regulations title 21. Retrieved from http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?FR=182.1180

Garrett, B.E., & Griffiths, R.R. (1997). The role of dopamine in the behavioral effects of caffeine in animals and humans. Pharmacology Biochemistry & Behavior, 57(3), 533–541. doi:10.1016/S0091-3057(96)00435-2

Giedd, J. (1999). Brain development. IX: Human brain growth. The American Journal of Psychiatry 156(1), 4. doi:10.1176/ajp.156.1.4

Goldstein, I.B., Shapiro, D. (1987). The effects of stress and caffeine on hypertensives. Psychosomatic Medicine, 49 (3), 226–235. doi: 10.1097/00006842-198705000-00002

Goulding, A. (2007). Risk factors for fractures in normally active children and adolescents. Medicine and Sport Science, 51, 102-120. doi:10.1159/000103007

Griffiths, R.R., Evans, S.M., Heishman, S.J., Preston, K.L., Sannerud, C.A., Wolf, B., Woodson, P.P. (1990). Low-dose caffeine discrimination in humans. Journal of Pharmacology and Experimental Therapeutics, 252(3), 970–978. doi:http://jpet.aspetjournals.org.ezproxy.library.ubc.ca/content/252/3/970.full.pdf

Harnack, L., Stang, J., & Story, M. (1999). Soft drink consumption among US children and adolescents: Nutritional consequences. Journal of the American Diabetic Association, 99(4), 436-441. doi:http://dx.doi.org/10.1016/S0002-8223(99)00106-6

Harris, S.S., & Dawson-Hughes, B. (1994). Caffeine and bone loss in healthy postmenopausal women. American Journal of Clinical Nutrition, 60(4), 573–578. doi:http://ajcn.nutrition.org/content/60/4/573

Health Canada. (2010). Preliminary guidance for industry on the labelling of caffeine content in prepackaged foods (March 2010). Retrieved from http://www.hc-sc.gc.ca/fn an/legislation/guide-ld/etiquetage-caf-labelling-eng.php

Health Canada. (2011). Information for Parents on Caffeine in Energy Drinks. Retrieved from http://www.hc-sc.gc.ca/ahc-asc/media/nr-cp/_2011/2011-132bk-eng.php

Health Canada. (2012). Caffeine in foods. Retrieved from http://www.hc-sc.gc.ca/fn an/securit/addit/caf/index-eng.php

Hering-Hanit, R., & Gadoth, N. (2003). Caffeine-induced headache in children and adolescents. Cephalalgia, 23(5), 332-335. doi:10.1046/j.1468-2982.2003.00576.x

Hughes, J.R., Oliveto, A.H., Liguori, A., Carpenter, J., Howard, T. (1998). Endorsement of DSM-IV dependence criteria among caffeine users. Drug and Alcohol Dependence, 52(2), 99–107. doi:10.1016/S0376-8716(98)00083-0

Johnson, R.K., & Kennedy, E. (2000). The 2000 dietary guidelines for Americans: what are the changes and why were they made? The dietary guidelines advisory committee. Journal of the American Dietetic Association, 100(7), 769–774. doi:10.1016/S0002-8223(00)00225-X

Kerrigan, S., & Lindsey, T. (2005). Fatal caffeine overdose: two case reports. Forensic Science International, 153(1), 67–69. doi:10.1016/j.forsciint.2005.04.016

Kristjansson, A., Sigfusdottir, I., Mann, M., & James, J. (2014). Caffeinated sugar-sweetened beverages and common physical complaints in Icelandic children aged 10–12 years. Preventive Medicine, 58, 40-44. doi: http://dx.doi.org/10.1016/j.ypmed.2013.10.011

Lane, J.D., & Williams Jr., R.B. (1987). Cardiovascular effects of caffeine and stress in regular coffee drinkers. Psychophysiology, 24 (2), 157–164. doi:10.1111/j.1469-8986.1987.tb00271.x

Lindt. (2013). Lindt Frequently Asked Questions. Retrieved from http://www.lindtusa.com/shop/lindt frequently-asked-questions

Marshall, T.A., Broffitt, B., Eichenberger-Gilmore, J., Warren, J.J., Cunningham, M.A., & Levy, S.M. (2005). The roles of meal, snack, and daily total food and beverage exposures on caries experience in young children. Journal of Public Health Dentistry, 65(3), 166–173. doi:10.1111/j.1752-7325.2005.tb02807.x

Miller, K.E., 2008. Energy drinks, race, and problem behaviors among college students. Journal of Adolescent Health 43(5), 490–497. doi:10.1016/j.jadohealth.2008.03.003

Nehlig, A., Daval, J., & Debry, G. (1992). Caffeine and the central nervous system: Mechanisms of action, biochemical, metabolic and psychostimulant effects. Brain Research Reviews, 17, 139- 170. doi:10.1016/0165-0173(92)90012-B

Plotnikoff, R. C., Trinh, L., Courneya, K. S., Karunamuni, N., & Sigal, R. J. (2008). Predictors of aerobic physical activity and resistance training among Canadian adults with type 2 diabetes: An application of the Protection Motivation Theory. Psychology of Sport and Exercise, 10(3), 320-328. doi:10.1016/j.psychsport.2008.10.002

Pollak, C.P., & Bright, D. (2003). Caffeine consumption and weekly sleep patterns in US seventh-, eighth-, and ninth-graders. Pediatrics, 111(1), 42–46. doi: 10.1542/peds.111.1.42

Red Bull. (2015). Athletes. Retrieved from http://www.redbull.com/ca/en/browse-all-athletes

Reissig, C., Strain, E., & Griffiths, R. (2009). Caffeinated energy drinks - A growing problem. Drug and Alcohol Dependence, 99, 1-10. doi:10.1016/j.drugalcdep.2008.08.001

Seifert, S., Schaechter, J., Hershorin, E., & Lipshultz, S. (2011). Health effects of energy drinks on children, adolescents, and young adults. Pediatrics, 127(3), 511-528. doi:10.1542/peds.2009 3592

Sung, B.H., Whitsett, T.L., Lovallo, W.R., al’Absi, M., Pincomb, G.A., & Wilson, M.F. (1994). Prolonged increase in blood pressure by a single oral dose of caffeine in mildly hypertensive men. American Journal of Hypertension, 7 (8), 755–758. doi:10.1093/ajh/7.8.755

Temple, J. (2009). Caffeine use in children: What we know, what we have left to learn, and why we should worry. Neuroscience & Biobehavioral Reviews, 33, 793-806. doi:10.1016/j.neubiorev.2009.01.001

Trask, A. V., Motherwell, W. S., & Jones, W. (2005). Pharmaceutical cocrystallization: Engineering a remedy for caffeine hydration. Crystal Growth & Design, 5(3), 1013-1021. doi:10.1021/cg0496540

Waring, W.S., Goudsmit, J., Marwick, J., Webb, D.J., & Maxwell, S.R. (2003). Acute caffeine intake influences central more than peripheral blood pressure in young adults. American Journal of Hypertension, 16 (11), 919–924. doi:10.1016/S0895-7061(03)01014-8