Iron is a nutrient needed for oxygen transport in the body. It can be obtained in plant sources as non-heme iron or animals as heme iron. Non-heme iron is less bioavailable, meaning it is more difficult for the body to absorb compared to heme iron. Protein is essential for building muscle, producing enzymes needed for digestion and metabolism and for making immune system cells.
Dietary Recommendations
The National Academy of Sciences reports the Dietary Reference Intake for iron as 8 mg per day for most children, men, pre-menstrual girls and post-menopausal women. The recommendation for menstruating women is 18 mg per day. Protein needs also vary based on age, disease states and activity level. The average healthy adult should consume 0.8 g of protein per kilogram body weight. Individuals that are very active may require 1.0 g of protein per kilogram with endurance athletes needing as much as 1.8 g per kilogram. Body weight in kilograms is determined by taking weight in pounds and dividing by 2.2. Then, take body weight in kilograms and multiply by 0.8. For a man who is 180 lbs., his protein requirement would be about 66 to 82 g of protein a day.
Plant Sources of Iron and Protein
Soybeans are one of the highest plant sources of iron. One serving, about one half cup contains 4.4 mg of iron, 14 g of protein and only 150 calories. Beans, lentils, nuts and seeds also contain comparable quantities of iron and protein. A half cup serving of lentils or beans contains about 3.5 mg of iron and 8 g of protein on average. Most cereals and many other packaged foods are also fortified with iron. Vitamin C is required to facilitate the absorption of non-heme iron. Pair non-heme iron sources with a high vitamin C food such as broccoli, peas, tomatoes or citrus to maximize absorption.
Animal Sources of Iron and Protein
Beef provides the highest amount of iron per ounce compared to pork or poultry. A 3-oz. serving of beef, about the size of a deck of cards, provides between 3 and 4 mg of iron and 21 g of protein. The same amount of chicken, turkey or pork provides half the amount of iron, but the same amount of protein. Liver contains the highest amount of iron, 8 to 12 mg of iron, but is not palatable for most individuals. While heme iron is more absorbable and better utilized in the body, meats also contain saturated fat and cholesterol, both of which are linked to heart disease when consumed in large amounts. A balance of heme and non-heme iron sources will meet requirements of iron, protein and other essential vitamins and minerals.
Foods That Impair Iron Absorption
Other nutrients, such as calcium, compete with iron for absorption. Dairy foods, which are high in calcium, should be avoided in the same meal as iron-rich foods. Coffee, tea and fiber-rich foods can also impair iron absorption. Consume these foods at least an hour before or after an iron-rich meal.
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