"The process starts with glucose, which is the sugar both humans and yeast use to power their bodies. Like humans, yeast cells prefer to burn their glucose with oxygen to produce energy. But yeast cells sometimes find themselves in situations where oxygen is scarce - for instance, when they are trapped in the bottom of huge vats of grape juice. [...]

The details of that process are interesting in their own right, but all we're really concerned with here are those two shards remaining after the glucose is finally split. Those shards are molecules of ethanol.

The birth of alcohol via this inefficient splitting of glucose has one very salient consequence for humans: most of the chemical energy of the original glucose molecule remains bound up in the ethanol fragments. That energy equals calorics: about seven per gram - which works out to about a hundred calories in a standard drink from the alcohol alone.

Alcohol, in other words, is no diet drink.

Alcohol's origins also explain some facts about the alcohol content of some common drinks. Yeast cells struggling to survive under suffocating conditions quickly excrete the ethanol fragments because they are basically poisonous. Ethanol interferes with many of the reactions vital to the life of a cell. As a result, yeasts excrete ethanol, which slowly builds up in the surrounding liquid - exactly where the brewer or vintner wants it. Given an adequate amount of glucose, the ethanol content of a fermenting liquid rises until it reaches about 12 percent. At this point, it starts to back up inside the yeast cells because it can no longer diffuse across the cell wall. Unable to dispose of the poisonous waste, the yeasts shut down and become dormant.

All activity stops, including the production of new ethanol. This is the reason that most table wines have roughly a 12 percent alcohol content: that's as high as it can go before the yeasts throw in the towel. Some wines can achieve slightly higher values if they are unusually rich in glucose, but the only way to get significantly higher ethanol levels is by distillation."

"With all this evidence suggesting that moderate consumption of wine - and probably other forms of alcohol as well - confers protection against heart disease, why isn't everyone reaching for their favorite bottle of cabernet? There are several reasons.

The French, while enjoying their much reduced rates of heart disease, develop liver disease at a rate that is roughly twice that of Americans (Dolnick 1990). In addition to taxing the liver, moderate drinking has been associated with a slightly increased risk of breast cancer and cancer of the bowel. And, of course, even a single shot of liquor consumed quickly can produce transient blood alcohol levels high enough to reduce reaction times and impair coordination, thus increasing the risk of accidents.

Second, advising abstainers to begin drinking could lead to increased alcoholism because it is not yet possible to predict who will succumb to alcohol's addictive potential. Other methods, such as losing weight and exercising, offer even greater benefits and have fewer associated risks."

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