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Energy drinks may affect blood vessel function even when routine vital signs show little change. The finding has implications for nurses assessing patients who consume these popular caffeinated beverages.
In research led by John Higgins, MD, MBA, MPHIL, professor and cardiologist at McGovern Medical School at UTHealth Houston, researchers measured endothelial function in 11 healthy young adults before and 90 minutes after they consumed a 24-ounce energy drink.
Peak flow-mediated dilation, a measure of how well an artery relaxes and expands, fell from 5.9% to 1.9%. Meanwhile, heart rate and blood pressure did not change significantly.
John Higgins, MD, MBA, MPHIL, professor and cardiologist at McGovern Medical School at UTHealth Houston. Photo credit: Credit: UTHealth Houston
“In other words, your blood vessels can take a hit before your vitals even seem to notice,” Higgins said.
For nurses, energy drink consumption may be worth considering when patients report palpitations, chest pain, headaches, anxiety, insomnia, or other symptoms associated with stimulant use.
What Happens After an Energy Drink?
Caffeine is one of the primary stimulants in energy drinks. It blocks adenosine, a brain chemical involved in signaling the need for rest, increasing alertness while potentially increasing heart rate, constricting blood vessels, and raising blood pressure.
Its effects can begin within 30 to 120 minutes and may persist for hours, depending on factors including genetics, caffeine tolerance, and the amount consumed.
Research cited by Higgins has found that energy drinks increase systolic blood pressure by an average of about 4.4 mmHg, with greater increases associated with beverages containing higher amounts of caffeine.
But caffeine may not explain the entire cardiovascular response. In one trial, an energy drink produced greater changes in the heart’s electrical activity than caffeine alone, suggesting that the combination of ingredients may also play a role.
Energy drinks can contain taurine, guarana, ginseng, B vitamins, and other compounds. Guarana and yerba mate can provide additional sources of caffeine, while stimulants such as yohimbine can affect anxiety, blood pressure, and heart rhythm.
Some products also contain proprietary blends that disclose the total amount of a mixture without specifying how much of each ingredient is included.
Energy Drinks Are Not Sports Drinks
Energy drinks can sometimes be confused with sports drinks, but the two serve different purposes.
Sports drinks are designed to replace fluids and electrolytes. Energy drinks contain stimulants and should not be used as a hydration tool, according to Higgins.
Beyond the distinction between hydration and stimulation, caffeine levels in energy drinks can vary considerably, ranging from about 80 mg to 400 mg or more. Some products may also contain 50 grams or more of sugar per can.
Higgins recommends that healthy adults keep total daily caffeine intake from energy drinks, coffee, tea, soda, and supplements below 400 mg and avoid combining multiple stimulant sources, including coffee, pre-workout supplements, energy drinks, and diet pills.
He recommends that children and teenagers avoid energy drinks entirely. People who are pregnant or breastfeeding and those with heart conditions, high blood pressure, or caffeine sensitivity should also avoid them.
Energy drinks should not be combined with alcohol because stimulants do not reverse alcohol intoxication and may make a person feel more alert without reducing impairment.
When Energy Drink Symptoms Need Attention
Serious cardiovascular reactions are uncommon, but irregular heart rhythms, chest pain, and cardiac arrest have been documented in connection with heavy or rapid energy drink consumption, particularly among people with underlying heart conditions.
More common effects include jitteriness, headaches, insomnia, nausea, and palpitations. In one survey cited by Higgins, more than half of young energy drink users reported at least one adverse reaction.
People who experience chest pain, fainting, a racing or irregular heartbeat, severe shortness of breath, confusion, or seizures following heavy caffeine consumption should stop consuming the product and seek medical help, Higgins said.
For nurses conducting medication reconciliation or assessing unexplained cardiovascular, neurologic, or sleep-related symptoms, asking about energy drinks and other caffeine sources may uncover information that is not captured on a traditional medication list.
The larger message for patients is that stimulants can temporarily mask fatigue without addressing its underlying cause.
“The best source of sustainable energy isn’t found in a can,” Higgins said. “It comes from sleep, hydration, food, and exercise. Energy drinks might mask fatigue for a bit, but they won’t actually fix it. Your body’s not asking to fly. It’s asking for a power nap.”
