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I love caffeine

Caffeine jitters

The growing popularity of energy drinks — and deaths linked to those products — are fostering new concerns about how much caffeine people can safely consume, according to the a comprehensive article in the current edition of Chemical & Engineering News, the weekly news magazine of the American Chemical Society, the world’s largest scientific society.

The article points out that sales of Red Bull, Monster Energy and other products have grown from virtually nothing a decade ago to almost $10-billion in 2012. Alongside this incredible growth, stories have surfaced with increasing frequency in recent years about deaths and emergency room visits linked to caffeinated energy drinks. Emergency room visits linked to energy drinks, for instance, increased to 20 000 in 2011, up 36 percent from the previous year. The US FDA is investigating, but manufacturers insist their products are safe.

The article focuses on the difficulty in determining safe consumption levels for caffeine. Scientists have found that the toxic dose of caffeine is approximately 10 grams — equivalent to about 130 cups of coffee. But it can vary greatly from person to person. The variation results from differences in how each person’s body processes caffeine, affected by age, weight, gender and other factors, such as use of cigarettes.

For this reason, it’s difficult to set a safe limit of daily consumption on the compound. Physiological differences, as well as differences in the way people consume caffeine, have tied FDA in knots as it has debated how to regulate the substance.

Caffeine has long been prized for its ability to increase a person’s alertness and energy. According to lore, these properties were noted in the 9th century by an Ethiopian goatherd who found his flock frolicking after eating coffee berries from nearby bushes. What is not lore is that caffeine is one of the most frequently ingested pharmacological substances in the world. People proclaim their love of the chemical by displaying its structure on T-shirts, mugs, and jewelry. According to FDA, at least 80% of adults in the US consume caffeine every day.

Scientists know a lot about how the popular stimulant triggers alertness in the body at low doses, says Bertil Fredholm, emeritus professor of pharmacology at the Karolinska Institute, in Sweden. Once the compound gets absorbed into the bloodstream, it moves to the liver, where it is metabolised. There, cytochrome P450 enzymes yank different methyl groups off caffeine to transform it into the primary metabolites paraxanthine, theophylline, and theobromine.

Caffeine and its metabolites subsequently bind to proteins called adenosine receptors located throughout the body. When they bind to two of these receptors—named A1 and A2A—the stimulants block the proteins from interacting with their natural partner, the small molecule adenosine. Normally, adenosine’s interaction with its receptors regulates nerve cell activity as well as the release of neurotransmitters such as dopamine. It also promotes sleepiness.

But when caffeine or its metabolites prevent adenosine from doing its job, dopamine and other neurotransmitter levels increase, leading to a surge in nerve activity in the brain and on the heart. This action then causes a jump in heart rate and blood pressure.

Like other indulgences in life, however, too much of a good thing can be bad. “Whereas low-dose caffeine effects are wakefulness, a little bit of arousal, and slight euphoria,” Fredholm says, “high-dose effects are anxiety, irritation, and general mental discomfort — a completely different kettle of fish.” Those negative high-dose effects are especially worrisome, given that researchers still don’t fully understand their origins.

“High-dose caffeine effects are much more complex,” Fredholm explains. “It’s still unknown precisely what the primary mechanism of action is in the brain and elsewhere.”…..

Chemical & Engineering News: Read the full article here

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