What It Is
Iron is necessary for producing hemoglobin, the part of red blood cells that carries oxygen through your body. There are two types of dietary iron. Heme iron is found in meat, fish and pork and is absorbed and used more efficiently by the body than the non-heme iron in fruits, enriched cereals and grains.
Why You Need It
When you have iron-deficiency anemia, your cells can't get enough oxygen, which results in fatigue, irritability, low energy levels and difficulty concentrating. This type of anemia is one of the most common nutritional deficiencies in North America. It's most typically a problem for menstruating and pregnant women, people on calorie-restricted diets, teenagers, young children and endurance athletes, who tend to lose iron through sweating.
How Much You Need
Here are the recommended daily allowances (in milligrams):
Premenopausal women, ages 19 to 50: 18
Postmenopausal women: 8
Pregnant women: 27
Breast-feeding women: 9
The tolerable upper intake level from foods and supplements is 45 milligrams per day. Since the body doesn't absorb the kind of iron generally found in some vegetables and grains (non-heme) as efficiently as it does animal sources of iron (heme), vegetarians need to increase these allowances by 1.8 times. For example, a 30-year-old vegetarian woman needs 32 instead of 18 milligrams daily.
Can You Take Too Much?
Consuming too much iron can cause indigestion and constipation and excessive doses – above the upper limit – may increase the risk of chronic disease and can be toxic. Your doctor should confirm an iron-deficiency before you take an iron supplement. Supplements are unlikely to be of much benefit to people who are at low risk for iron deficiency, such as adult men and postmenopausal women, and can be harmful.
Where to Get It
You can get heme iron from red meat, organ meats, pork, eggs and poultry. Non-heme iron is found in enriched cereals, some dark green vegetables, nuts, seeds and dried fruits, such as raisins.
Many factors affect the body's ability to absorb iron. For example, tannins found in tea interfere with this process. And phytates, which are compounds found in some grains and vegetables – such as spinach, wheat, bran and nuts – can attach to iron and inhibit its absorption. However, vitamin C enhances the absorption of non-heme iron, so adding sliced strawberries to a bowl of iron-enriched packaged cereal will boost your iron absorption. As well, cooking vegetables releases some of the iron that is bound to the phytates.
Check out an iron food source chart.