According to the National Coffee Association, seven in ten Americans drink coffee at least once a week and 62 percent daily. If you’re one of them, you may rush to the coffee maker in the morning to get the boost of energy you need to get your day started.
While you might expect coffee to provide an energy boost, this is not always the case. For some, coffee can induce sleepiness.
“At first, the caffeine gives you a boost,” explains registered dietitian Keith-Thomas Ayoob, EdD, RD, FAND. “Then, as the caffeine wears off and your blood sugar levels drop, there is frequently a dip in energy.”
If you notice a decrease in energy levels following coffee consumption, here’s why and what to do about it.
1. Sweeteners Can Increase and Decrease Blood Sugar
According to the USDA, a cup of black coffee contains only two calories and no fat, carbs, or protein. While coffee is naturally sugar-free, many people enjoy sweetening it with a variety of sweeteners to offset the bitterness. The sugar content of these sweeteners accumulates quickly and may contribute to the drowsiness associated with coffee consumption.
“Depending on what people add to their coffee, their sweetener of choice may or may not send their blood sugar on a roller coaster,” says Jenna Volpe, RDN, CLT, a registered dietitian and clinical herbalist. “This frequently manifests as a brief burst of energy followed by a midday slump.”
According to the Cleveland Clinic, the sugar in coffee also affects your insulin levels, leaving you feeling exhausted when your blood sugar levels plummet.
“Excess sugar in coffee stimulates the release of excess insulin, and insulin’s role is to lower blood glucose levels,” explains registered dietitian-nutritionist Mehak Naem, RDN. “When glucose levels fall, you will experience fatigue and sleepiness.”
2. It Allows the Amino Acid to Be Released Adenosine
According to a February 2010 review in the Journal of Alzheimer’s Disease, coffee’s stimulating effects are largely due to the way it binds to adenosine receptors. Adenosine is a necessary amino acid for sleep.
“While most people experience an initial burst of energy after drinking caffeinated coffee, if they notice that drinking coffee immediately makes them tired, they are likely experiencing adenosine release in the brain,” Volpe says.
“Adenosine is an amino acid that plays a role in sleep-wake cycles. Caffeine initially inhibits adenosine receptors, resulting in a brief surge of energy and alertness. When caffeine is metabolised, some individuals may experience an abrupt surge of adenosine.”