Like all fats, those of the polyunsaturated variety are chains of carbon atoms that have hydrogen atoms attached along their sides, like legs on a centipede. Unlike saturated fats, which have all their legs, and monounsaturated fats, which are missing one leg, a polyunsaturated fat lacks two or more legs. Most polyunsaturates are liquid at room temperature. Most also come from vegetables. You know them as corn oil, safflower oil, and the like.
Because polyunsaturates reduce blood-cholesterol levels, they are much preferred over saturated fats. Numerous studies have shown that replacing saturated fat with polyunsaturated cuts the risk of heart disease. The same appears to be true for diabetes. Studies do not show a clear link between polyunsaturates and the risk of breast, colorectal, or prostate cancer, however.
Your Daily Allowance
The Food and Nutrition Board (FNB) has not yet issued a Recommended Dietary Allowance (RDA) for this type of fat. In September 2002 the Board released Adequate Intakes for a few subtypes, but Diet Power does not monitor these because shortages are virtually unknown in the United States.
For simplicity's sake, Diet Power makes your Personal Daily Allowance (PDA) of polyunsaturated fat the same as your PDA of monounsaturated fat: the number of grams required to make up 7½ percent of your PDA of calories. When added to the 10 percent of calories allowed for saturated fat, these two figures complete the 25 percent allowed for total fat.
The FNB has not established a Tolerable Upper Intake Level (UL) for polyunsaturated fat.
Revising Your Allowance
You can change your PDA to whatever your doctor advises. See Personal Daily Allowances, Editing Your.
Color Coding of This Nutrient
The polyunsaturated-fat bar in your Nutrient History is:
· blue for "good" if you've logged 50 to 100 percent of your PDA
· red for "bad" if you've logged more than 100 percent of your PDA
· yellow for "caution" if you've logged less than 50 percent of your PDA
· missing if you've logged no polyunsaturated fat.
In the nutrient profile of a food or recipe, the polyunsaturated-fat bar is:
· green for "good" if getting your entire PDA of calories from this item would give you less than 50 percent of your PDA of polyunsaturated fat
· magenta for "bad" if getting all your calories from the item would give you more than 150 percent of your PDA of polyunsaturated fat
· blue for "neutral" otherwise
· missing if the amount of polyunsaturated fat is either zero or (when the abbreviation Polyunsat. is grayed out) unknown.
How Complete Are Diet Power's Polyunsaturated-Fat Readings?
For the 8500 generic items in the Food Dictionary: fairly complete. Only 12 percent list their polyunsaturated-fat content as "unknown."
For the 2500 chain-restaurant items: totally incomplete. All list polyunsaturated fat as "unknown."
For all 11,000 items combined: not terribly complete. About 30 percent list polyunsaturated fat as "unknown."
These figures mean that if you frequently log chain-restaurant foods (or user-added foods with missing polyunsaturated-fat readings), your Nutrient History may underreport your intake of polyunsaturated fat by a few points.
To see whether a particular food has a polyunsaturated-fat reading, open the Food Dictionary and check the food's nutrient profile. If you find a question mark beside "Fat, polyunsaturated," it means the amount is unknown. (To see all foods with unknown polyunsaturated-fat readings, click the dictionary's PowerFoods tab and sort the foods by polyunsaturated-fat power; then scroll toward the bottom of the list until you see foods with question marks in the "Power Rating" column.)
Polyunsaturated Fats on Food Labels
Nutrition labels are not required to report how much of a food's fat is polyunsaturated, but many do. Since there is no official Daily Value (DV) for this nutrient, the amount is always listed in grams. (The Diet Power Daily Value is 22.5 grams.)
For more on label regulations, see Labels, Food.