Dear Straight Dope:
So ... I'm on a diet and can have unlimited vegetables, but absolutely NO vegetable oil! If vegetables don't have oil ... where does vegetable oil come from? Please explain.
Uh, Fitz … Cecil answered this in THE STRAIGHT DOPE TELLS ALL. Been a while since you saw the inside of a bookstore, I take it?
To see what other authors say, I looked in On Food and Cooking (The Science and Lore of the Kitchen) by Harold McGee. Here’s McGee’s take on why veggies don’t have much oil …
First of all, oil is basically used by plants as a store of energy, just as in animals. But so are various sugars and starches (carbohydrates) – and they tend to be used in more ways than just for fuel (for example, plant cellulose is a form of carbohydrate). So generally fats aren’t needed in plants, they can get by with carbos.
Fats and oils hold more energy than a given amount of carbohydrates – about double the energy. In plants weight doesn’t matter much except in the seed – it takes a lot of energy to grow the seed and space (and weight) in a seed is at a premium, so oil is the most efficient storage. That’s why oils are usually made from vegetable seeds … excepting a few anomalous plants like the avocado, which stores oils instead of sugar or starch in the fruit.
Animals use oils and fats for the same reason. They have to move – and the space and weight saved by using fat and oils instead of carbohydrates is significant (a 125 lb. woman would weigh 150 or so if she didn’t use fat storage). So if your SO says you’re getting a little chubby, tell him (or her), “Don’t think of it as fat, hon. Think of it as efficient energy storage.” Then make the creep sleep on the couch.
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