Got to have that morning rush, whether it is from coffee, tea, chocolate, a soft drink, energy drink or some other form of caffeine?

You are not alone. In North America 90 percent of adults use caffeine. It is the most widely consumed psychoactive drug, yet it is legal and largely unregulated.

Caffeine acts on the brain through several metabolic mechanisms. Most important is to counteract adenosine, a neurotransmitter that suppresses activity in the central nervous system. Because caffeine blocks adenosine receptors, it also affects most of the other major neurotransmitters, including dopamine, acetylcholine, serotonin and, in high doses, norepinephrine and gabapentin. To a small extent it affects epinephrine, glutamate and cortisol.

There are both positive and negative aspects to caffeine. It stimulates the brain’s pleasure centers, but it is mildly addictive. It may lead to complications in pregnancy when consumed in large amounts, but it may provide protection against Parkinson’s and some cancers.

The relatively small amounts consumed by most people have low health risks even with long-term usage. Every individual responds differently to caffeine, which makes it difficult to make general statements about health risks.

A growing caffeine food industry has caused the Food and Drug Administration to scrutinize the amount of caffeine in food products. As of July it restricted beverages to containing less than .02 percent caffeine. FDA officials say that less than 400 milligrams per day does not generally have dangerous negative effects, and they consider 1,000 mg the borderline for toxicity.

This recent regulation arose because manufacturers are putting large doses in larger serving sizes and the FDA is concerned about the cumulative effects of intake throughout the day, which the agency fears could lead to strong dependency. Furthermore, consumption by children may be linked to neurological and cardiovascular problems.

There have been at least seven deaths from caffeine since 2009. Compared with other substances such acetaminophen (the active ingredient in Tylenol), the death rate is small, but the fact that it has caused deaths raises a red flag.

In October a man in the United Kingdom died after eating a tin of 12 chocolate mints, each one of which contained 80 mg of caffeine, as much as a can of Red Bull. A warning on the package cautioned against eating more than five mints in a 24-hour period.

Coffee contains the highest amount of caffeine of any natural beverage. A 20-ounce cup of Starbucks contains more than 400 mg, equivalent to two shots of 5-Hour Energy or slightly less than two Red Bulls.

There is growing concern among health professionals that manufacturers are spiking their products with high concentrations of caffeine to rely on its addictive qualities in children’s drinks to recruit long-term users of their products.

Caffeine is not the only player in the energy drink business. Other additives such as taurine, niacin, L-carnitine and pyridoxine have been implicated in deaths from energy drinks. In concert with alcohol or heart disease, the lethal amount is reduced for anyone.

This is far from the complete story of caffeine. It has been extensively studied, and because it is so ubiquitous the studies continue.

———

Richard Brill is a professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.