Olestra is a fat substitute developed by Procter and Gamble. Ordinary fats are built out of a molecular structure known as a triglyceride: it's a microscopic tree, with a trunk made of glycerol and three branches made of fatty acids. Our bodies can't absorb triglycerides, but the enzymes in our digestive system are able to break the branches off so they may be absorbed separately. With Olestra, the glycerol trunk of a fat is replaced with a sugar, which allows not three but eight fatty acids. And our enzymes are unable to break down a fat tree with eight branches--so the Olestra molecule can't be absorbed by the body at all.

The FDA has required all Olestra products to carry a somewhat daunting label saying that they may cause "cramping and loose stools." As a result, sales have been disappointing. Most of this concern, however, appears to be overstated. Procter and Gamble has done randomized, double blind studies--one of which involved more than three thousand people over six weeks--and found that people eating typical amounts of Olestra-based chips don't have significantly more gastrointestinal problems than people eating normal chips.

Perhaps the best way to put the Olestra controversy into perspective is to compare it to fibre. Fibre is vegetable matter that goes right through you: it's not absorbed by the gastrointestinal tract. Nutritionists tell us to eat it because it helps us lose weight and it lowers cholesterol-even though if you eat too many baked beans or too many bowls of oat bran you will suffer the consequences. Do we put warning labels on boxes of oat bran? No, because the benefits of fibre clearly outweigh its drawbacks. Research has suggested that Olestra, like fibre, helps people lose weight and lowers cholesterol; too much Olestra, like too much fibre, may cause problems.

"Olestra" is as much a process as a compound: you can create an "Olestra" version of any given fat.

Much of this information was gleaned from a New Yorker article by Malcolm Gladwell, published March 5, 2001

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