The Implications of Caffeine Consumption on Stress and Appetite

by Christine Gary

“There’s too much blood in my caffeine system.” It’s the mantra of most graduate students come finals period. Caffeine becomes students’ comrade in arms as they face off against a semester’s worth of lectures. Energy drinks, coffee, and tea intake spike to fuel marathon study sessions that, fingers crossed, consequently spike grades. But is caffeine really helpful? What are the physiological implications of guzzling that venti chai latte?

Many diet pills contain caffeine, fostering the misconception that it is an appetite suppressant. Initially, caffeine does decrease hunger because it acts as a stimulant. It elicits the Central Nervous System’s “flight-or-fight” response. The adrenal glands release stress hormones, epinephrine (adrenaline) and norepinephrine, to ensure “your muscles tense, your blood sugar elevates for extra energy, your pulse and respiration rates speed up, and your state of alertness increases” (Whitaker, page 261). This response is helpful…when you need to spear a saber-toothed tiger. But when you’re just sitting in the library, that brief rush will have no release, and may manifest in mental, physical, and emotional stress. (Robertson et al, 1978) (Lane et al, 1990) (Kerr et al, 1993) (Lane et al, 2002). Cue mood swings and adverse health effects (shakiness, dizziness, irritability).

Shortly thereafter, caffeine-triggered release of cortisol can actually stimulate appetite (Takeda et al, 2004) (Epel et al, 2001). Study munchies anyone? Feelings of hunger can be compounded by caffeine-induced hypoglycemia (the ensuing crash in blood sugar following its initial spike) (Kerr et al, 1993). In response to hypoglycemia, people often crave higher fat food and sugars (Castonquay, 1991) (Bjorntorp, 2001). If this cycle’s habitual, it could interfere with an individual’s weight management (Strachan et al, 2004) (Dewan et al, 2004). Regular coffee drinkers can find themselves in a state of chronic stress, predisposing them to seek comfort in emotional eating. The anxiety brought on by stress hormones has been shown to trigger binges and overeating (Krahn et al,1991). Consistently elevated levels of cortisol are associated with increased abdominal fat. Deposition of excess mid-section flub consequently perpetuates the release of more stress hormones (Dallman et al, 2004) and increased caloric intake.

To kick you while you’re down, caffeine doesn’t just raise stress hormones, it also interferes with calming neurotransmitters like serotonin (Simontacchi, page 191) and GABA (Gamma-aminobutyric acid). The brain, nervous system, and heart all produce GABA to aid stress management. It fosters a person’s sense of well-being. Caffeine prevents GABA from binding to GABA receptors, which hinders its calming effect (Roca et al, 1988).

“Ok, no prob,” you say, “I’ll switch to decaf, and sidestep that slew of physiological stress indicators.” Not to be a buzzkill, but there are other ingredients in coffee associated with stress factors, so decaffeinated coffee isn’t entirely benign (Quinlan et al, 2000).

“Well geez, what a doomsday scenario. Surely plenty of college students guzzle caffeine with impunity and it can’t be THAT bad.” True, there is a range of caffeine sensitivity and dependence. Certain individuals are more prone to symptoms than others. Some are affected after one cup of coffee, while others need three to feel anything. In a cohort of healthy men, the usually consumed amount of caffeinated coffee increased circulating cortisol, but otherwise did not “have short-term effects on appetite, energy intake, glucose metabolism, and inflammatory markers” (Gavrieli et al, 2011). Moderation is key.

But why risk the rollercoaster ride of elevated blood sugar and stress hormones when there are safer alternatives? Ginseng tea can provide a caffeine-free energy boost. It’s made from the ginseng root, not tea leaves, hence no caffeine (Mindell, page 388).

Green tea can be a good transition step out of caffeine addiction. While coffee and green tea are both brimming with health-boosting antioxidants, green tea delivers about half the caffeine content of coffee (Jones, 2011). Green tea also contains catechins, “particularly epigallocatechin gallate (EGCG), which in concentrated supplement form has been shown to increase fat oxidation (Auvichayapat et al, 2008)(Dulloo et al, 1999)(Venables et al, 2008), reduce body fat (Nagao et al, 2007), and increase weight loss (Auvichayapat et al, 2008)” (Dennis et al, 2009). You’d have to drink several cups of green tea to get the catechin levels found in concentrated forms, but hey, the test is tomorrow morning, you have all night! Not to mention, it’s calorie-free. So it beats drinking multiple cups of lattes, espressos, café mochas, and cappuccinos. High consumers of these drinks average a daily energy intake that is 206 kcal higher than nonconsumers (Shields et al, 2004).

While the science is conflictive at times, the majority expert consensus would seem to be that caffeine does more harm than good (Veracity, 2005) – an opinion backed by organizations like the Mayo Clinic (Zeratsky, 2009). Maybe it’s time to boot the lurking Judas from camp. Ditch caffeine and switch to getting nutrients from a balanced diet. You’ll end up stabilizing blood pressure, balancing hormone levels, and decreasing your stress. After all, finals are stressful enough without any added jitters.

References (in alphabetical order)

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Christine Gary is completing a Masters Degree in Nutrition Communication at the Tufts Friedman School of Nutrition. She’s an international marathon runner devoted to raising funds for charity: http://www.christinegary.com

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