A Few Fat Facts

The language of science is precise; just ask any scientist. Usually I'm willing to go along with this claim, but once in a while I have some problems with the professionals concise but still obscure language.

Consider: what exactly is it that saturates a saturated fat? You'd think, given the fuss about avoiding saturated fats in one's diet, that it was elixir of undiluted evil. Hah! It turns out that what does the saturating is hydrogen.

This is the story, as I got it from Co-Op Food Facts, a pleasantly straightforward publication from a consumer cooperative centered in the Midwest. The first thing I learned is that fats are mostly composed of fatty acids--about 95 percent of every edible fat or oil consists of fatty acids.

Fatty acids all are based on carbon chains---carbon atoms linked together one after another in a single molecule. Different fatty acids are defined as saturated, monounsaturated, or polyunsaturated depending on how effectively hydrogen atoms have linked onto those carbon chains. That is, if every space a hydrogen atom could occupy, by the rules of chemistry, is filled with a hydrogen atom, then the fatty acid is saturated. If there's space for one more hydrogen atom somewhere along the chain, it's a monounsaturated fatty acid. A polyunsaturated fatty acid has many spaces (comparatively speaking) into which hydrogen atoms could fit.

Fats and oils earn their labels by the proportion of the different kinds of fatty acids they contain. A saturated fat has mostly saturated fatty acids, a polyunsaturated fat is predominantly made up of polyunsaturated fatty acids, and monounsaturated fats consist mostly of monounsaturated fatty acids.

The last two kinds of fats we'd probably usually think of as oils, because the more saturated a fat is, the more likely it is to be solid at room temperature. Animal and dairy fats illustrate this well---think of butter or beef suet. Unsaturated fats are naturally liquid.

There are exceptions to this convenient rule of thumb, of course. Coconut oil, pressed from the boiled meat of fresh or dried coconuts, has more saturated fat---about 9l percent by weight---than do butter or lard. The fruit of another kind of palm tree produces palm oil, which also has more saturated fat than butter does---about 85 percent to butter's 80. (Dieters may be dismayed to learn that one popular use for these tropical oils is in so-called nondairy creamers or coffee whiteners; another product commonly employing them is whipped topping---the butterfat-free replacement for whipped cream.)

Another apparent exception would seem to be solids made from unsaturated fats, such as shortenings for baking that---according to the label---are mostly cottonseed or soybean oils, both high in polyunsaturated fatty acids. However, the label also states that shortening is hydrogenated. That means hydrogen gas has been bubbled through the oils. The process provides the hydrogen to fill in all those spaces in the carbon chains; the polyunsaturated oil becomes a spreadable, useful, rancidity-resistant, but saturated fat. Once again, it's all in the hydrogen. It's filled the spaces available along the carbon chains, this time with the help of technology rather than nature.

By the way, if you've wondered about another term that nutrition scientists usually couple with "fats" when they're speaking of diets, a gram is about what a common paper clip weighs. So if a recipe analysis claims something has three grams of fat, think of it as three paper clips by weight. In those terrns, a tablespoon of butter is worth eleven and a half paper clips of fat, but only a bit over six of them are saturated fat.