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Iron can be found in both plant and animal-based foods, but most experts agree that humans absorb iron best from meat. Animal tissues contain what is known as “heme” iron, a name that derives from the blood hemoglobin that carries and creates the mineral in the first place. Iron can also be found in plant materials, particularly in nuts, seeds, and leafy greens like spinach. This sort of iron is “non-heme,” since it is not related to blood and is usually harder for humans to absorb.
So-called “red” meat, which is usually understood to be beef and other game that looks red when raw, is one of the best sources of heme iron. Muscular tissues are generally rich in red blood cells, which contain naturally high iron levels. Humans can usually absorb the mineral relatively easily, as the body breaks it down and processes it directly into the bloodstream. Animal livers are usually considered good sources, as well. One of the liver’s main functions is creating proteins, and it typically has very rich stores of readily-absorbable iron.
Poultry and Eggs
Heme iron can also be found in most poultry, including chicken, turkey, and duck. Birds do not typically have as much iron as mammals, but its quality is usually the same. People can also get the mineral from eggs, particularly egg yolks.
Shellfish and Seafood
Clams, oysters, and shrimp are typically good sources of iron, as are most other shellfish and crustaceans. Many fish also contain this important mineral, though the concentration can vary tremendously based on species and their diet. Wild-caught salmon, cod, and tuna are among the best sources. Farm-raised fish tend to still have some iron in their systems, but those that were fed more regimented diets made up primarily of grains and carbohydrates typically don’t have quite as much as animals that ate other small fish or iron-rich sea plants.
Iron also occurs naturally in many plants, and leafy greens like spinach and kale are among the best sources, along with seaweeds and some kelp species. The concentrations are in most cases far lower than in meats, since the mineral is not stored in or created by blood but rather occurs in ordinary fibrous cells. Iron is essential for plant life just as it is for animal life, but how it is created and stored is usually very different.
In most cases, raw leaves have the highest concentrations; cooking or otherwise exposing them to heat can cause many vitamins and minerals to leach out. Freezing for short durations doesn’t usually have the same effect, but over time — usually after about six months — some nutrient loss is common. Heme sources don’t usually face these issues of loss or reduction, since, in meats, the iron is permanently fixed in the tissues. It’s a lot easier to break it down in plants.
Fruits and Vegetables
Most fruits and vegetables also contain some iron, though the best sources tend to be those with the darkest flesh. Broccoli, asparagus, purple grapes, and plums are good examples. As with leafy greens, the best way for people to access these foods’ minerals is to eat them raw or just lightly cooked. Dried fruits usually contain the same amount of iron as their fresh counterparts, though, which can be a good option for people on the go.
Sugar beets are not normally considered high in iron, but blackstrap molasses, which is created by boiling and refining the beets, normally is. Blackstrap molasses is a very dense syrup-like substance that is commonly used in baking.
Nuts, Beans, and Seeds
Iron is typically available in every plant tissue, including seeds. Sunflower seeds and squash seeds, particularly pumpkin, are usually easy to find in most places. Tree nuts like almonds and cashews are also good sources of non-heme iron, and nearly every type of bean can also provide a rich supply. Black and kidney beans tend to have the highest concentrations, but lima beans and soybeans also rank near the top of the list. Soy products, particularly tofu and soymilk, are usually iron-rich, too.
Whole Grains and Fortified Foods
Similarly, most whole grains, like wheat and oats, also tend to be good sources. Baked goods made with whole grains usually have high concentrations of iron, though a lot depends on how the foods were processed. In general, the purer the grain, the more vitamins and minerals it contains, as a good deal be lost during refining.
Many food manufacturers will actually add non-heme iron to a number of so-called “staple” foods, like breads and cereal. In this way, foods that would not necessarily be good sources of iron on their own actually come to contain high concentrations. The best way for people to determine whether a particular product has been fortified is to read the label and look carefully at the ingredient list.
Heme iron can typically be directly absorbed into the human body no matter how it is consumed or what it is consumed with. The same is not always true for non-heme foods, however. Caffeine, calcium, and fiber can all make it harder for the body to absorb plant-based iron, and most health experts recommend limiting these things in meals rich in iron-containing plants.
Many experts say that people can help their bodies absorb non-heme iron by eating it alongside foods that are rich in vitamin C, particularly citrus fruits. Eating heme and non-heme foods together can also make a difference, and many people recommend cooking with a cast iron skillet in order to enhance the absorbability of iron. Whether or not this technique works is open for some debate, but it is popular in many places.
Importance of an Iron-Rich Diet
Iron is essential for human life, and though the body does create some on its own, it's not usually enough. People need to eat iron in their diets in order to stay healthy. A deficiency of this important mineral is known medically as anemia, and it often causes fatigue and muscle weakness.
Most governments around the world set recommended levels of iron intake that can serve as a guideline for meal planning and usually also help standardize food labeling. A manufacturer of iron-rich beans, for instance, might include both how much iron is in the food as well as what percentage of a person’s recommended amount a single serving contains. These recommendations vary from country to country, and also tend to change based on age and gender. Women who are pregnant, for instance, typically need more iron than middle-aged men, and elderly people and children are usually advised to consume more than teenagers and young adults.