This metal is a vital constituent of many enzymes, of the blood protein hemoglobin, and of the muscle protein myoglobin. It is essential to the body's exchange of oxygen and carbon dioxide in the cells.
There are two kinds of iron sources: heme iron (iron from meat and other animal products) and nonheme iron (iron from plant foods). The human body absorbs heme iron more readily than nonheme iron.
The best sources of heme iron are liver (especially pork liver), kidney, and other red meats, as well as egg yolks. The best nonheme sources are leafy green vegetables, dried fruits, dried peas and beans, potatoes, whole-grain and enriched cereals, and blackstrap molasses.
A deficiency of iron leads to anemia (low hemoglobin levels or red-cell counts in the blood), which makes a person feel tired or run-down because the body can't use oxygen as efficiently as it should. Pregnant women, teenagers, and young female adults are especially prone.
Thanks in part to heavy promotion of iron supplements in decades past, many people have the impression that the more iron they get, the better. In fact, a chronic excess can cause liver damage and heart failure¾and a short-term megadose may trigger fatal shock. One symptom of overdose is stomach distress.
(To avoid iron overdose, it's important not to get too much vitamin C. See Vitamin C.)
Your Daily Allowance
Diet Power sets your Personal Daily Allowance (PDA) of iron at the Food and Nutrition Board's (FNB's) Recommended Dietary Allowance (RDA). The RDA was revised in January 2001. For males, it decreased; for females, it rose for ages 19 to 50 and dropped for ages 51 and up, as well as for those who are pregnant or lactating. The new RDA for males of age 14* to 18 is 11 milligrams; for males 19 and older it's 8 milligrams. For females from 14* to 18 it's 15 milligrams; for those 19 to 50 it's 18 milligrams; and for those 51 and older it's 8 milligrams. The figure for pregnancy is 27 milligrams regardless of age. For lactation it's 10 milligrams for ages 18 and under, 9 milligrams for ages 19 and up.
Iron and Vegetarians
The RDAs that we've just cited assume that three-quarters of your intake is heme iron. If you're on a vegetarian diet, says the FNB, "it has been suggested that the iron requirement is approximately two-fold greater."
Notice, however, that the FNB does not urge such a doubling itself, and that it uses the word suggested instead of recommended. The implication is that, at least to some extent, vegetarians are on their own when it comes to deciding their iron intake. Ask your doctor for advice.
Also in January 2001, the FNB announced a Tolerable Upper Intake Level (UL) for iron. The UL for people aged 14* and older is 45 milligrams per day, regardless of age, sex, or reproductive state.
* Please remember that Diet Power is not designed for people under 15.
Revising Your Allowance
Diet Power automatically sets your Personal Daily Allowance of iron when you enroll in the program, but you can change your PDA to reflect your physician's recommendation. See Personal Daily Allowances, Editing Your.
Color Coding of This Nutrient
The iron bar in your personal Nutrient History is:
· blue for "good" if you've logged 100 to 150 percent of your PDA
· red for "bad" if you've logged less than 100 percent of your PDA or more than the Tolerable Upper Intake Level (UL)
· yellow for "caution" if you've logged more than 150 percent of your PDA
· missing if you've logged no iron.
In the nutrient profile of a food or recipe, the iron bar is:
· green for "good" if getting your entire PDA of calories from this item would give you more than 150 percent of your PDA of iron
· magenta for "bad" if getting all your calories from the item would give you less than 50 percent of your PDA of iron
· blue for "neutral" otherwise
· missing if the amount of iron is either zero or (when the word Iron is grayed out) unknown.
How Complete Are Diet Power's Iron Readings?
For the 8500 generic items in the Food Dictionary: very complete. Only 0.4 percent list their iron content as "unknown."
For the 2500 chain-restaurant items: not terribly complete. About 28 percent list iron as "unknown."
For all 11,000 items combined: fairly complete. About 6 percent list iron as "unknown."
(The percentage of unknowns will be higher, of course, if most of the foods that you've added to the dictionary lack iron figures.)
To see whether a particular food has an iron reading, open the Food Dictionary and check the food's nutrient profile. If you find a question mark beside "Iron," it means the amount is unknown. (To see all foods with unknown iron readings, click the dictionary's PowerFoods tab and sort the foods by iron power; then scroll toward the bottom of the list until you see foods with question marks in the "Power Rating" column.)
Iron on Food Labels
Almost all labels are required to report iron content. It is usually cited as a percentage of the Daily Value (DV), 18 milligrams. (The Daily Value is not necessarily right for you¾it's a rough estimate meant to accommodate most of the U.S. population.)
For more on label regulations, see Labels, Food.