Iron deficiency could be making millions of Americans tired. 5 foods high in iron, from meat to produce, could help fix it.

• Iron deficiency is one of the most common deficiencies in the US.
• Too little iron can lead to issues like fatigue and anemia if left untreated.

If you constantly feel groggy but are getting enough sleep at night, you may be missing out on a key nutrient: iron.

Iron is essential for the production of blood, yet approximately 10 million Americans don't get enough of it. If left untreated, an iron deficiency can progress into iron-deficiency anemia, which can cause dizziness, weakness, heart palpitations, and fatigue.

Pregnant people, people who menstruate, and people who follow a plant-based diet are particularly vulnerable to iron-deficiency anemia, according to the American Society of Hematology.

Eating foods rich in iron can help prevent iron-deficiency anemia and help treat existing deficiencies. Here are some of the best dietary sources of iron.

Oysters

Iron comes in two different forms: heme iron and nonheme iron. Animal products contain heme iron, which comes from hemoglobin — a protein responsible for transporting oxygen in blood. Roughly 25 to 30 percent of heme iron is absorbed by your body, according to a 2019 study.

Oysters are a great source of heme iron. One 3-ounce serving of oysters contains 8 mg of iron, 44% of the daily value of 18 mg, which is recommended for adults and children ages 4 and older, according to the National Institutes of Health.

Oysters are also an excellent source of zinc and vitamin B12. And they're full of healthy fats, including omega-3 fatty acids, which can promote heart health, and protein.

Beef

Like oysters, beef is a good source of heme iron. Beef liver is a particularly good source: A 3-ounce serving of pan-fried beef liver contains 5 mg of iron, 28% of daily value for adults and children ages 4 and older. Braised bottom round beef contains 2 mg, or 11% of the daily value.

In addition to iron, beef is also a solid source of protein, zinc, and B12. But don't overdo it — eating beef too often isn't good for heart health.

Fortified cereals

Many fruits, vegetables, legumes, and cereals contain substantial amounts of iron. However, these foods contain nonheme iron — a type of iron that is not as readily absorbed by the body.

Fortified cereals are a robust source of nonheme iron, coming in at about 18 mg per serving.

Fortified cereals also provide lots of other nutrients that vegans and vegetarians might lack — like vitamin B12, a nutrient critical for forming red blood cells that's naturally found in animal products. Plus, fortified cereals can boost fiber intake.

White beans

White beans are a good source of nonheme iron: A 1-cup serving of canned white beans contains 8 mg of nonheme iron.

White beans are also an excellent source of plant-based protein, as well as fiber — a necessary nutrient for gut health. One cup contains 12.6 grams of fiber — roughly the same amount the average American eats per day.

Spinach

Spinach is another good vegetable source of nonheme iron. One cup of boiled and drained spinach contains 6 mg of iron. Spinach is naturally rich in oxalate — a compound which can prevent iron absorption. Boiling spinach breaks down oxalate and can help maximize iron absorption, according to Consumer Reports.

Plus, spinach contains other important nutrients like folate, which helps with tissue growth, and calcium, which is necessary for bone health.

When eating iron-rich foods, it's also a good idea to eat foods that contain vitamin C. That's because eating foods rich in vitamin C in the same meal could boost iron absorption of nonheme iron.

Some vitamin C-rich options include tomatoes, bell peppers, and broccoli.