The human body breaks down protein, classified as a macronutrient, into the individual amino acids and then uses them to build the thousands of proteins, including hemoglobin, necessary to support bodily functions. Hemoglobin, the protein found in red blood cells, also requires a molecule of iron, an essential mineral. Failing to consume adequate amounts of protein, such as in situations of malnutrition, or iron results in deficiencies with a variety of symptoms.

Muscle Wasting

The foods you eat provide your body with the proteins it needs to function. The National Institute of Medicine Food and Nutrition Board recommends that adults consume 0.8 g of protein for every 1 kg of body weight, which averages to about 15 percent of their total calories, according to the Harvard School of Public Health. Those who follow a strict vegetarian diet or those with limited access to food due to poverty are at an increased risk for protein deficiency. When you do not intake enough dietary protein you body will compensate by breaking down protein found in your muscles, leading to a condition known as muscle wasting or muscle atrophy.

Fatigue

The body needs protein and iron to produce hemoglobin – the iron-rich protein responsible for carrying oxygen throughout the body. In fact approximately two-thirds of all the iron in your body can be found in hemoglobin, according to the National Institutes of Health Office of Dietary Supplements. A deficiency in either iron or protein can lead to a decrease in hemoglobin production, which causes a reduction in the number of functioning red blood cells, a condition known as anemia. A decrease in functioning red blood cells reduces the amount of oxygen circulating to the cells throughout the body. This results fatigue, the most common symptoms of anemia. Fatigue is the feeling of extreme tiredness that fails to resolve with rest.

Weakness

Along with fatigue, many with anemia experience shortness of breath and dizziness, especially when standing, according to the National Heart Lung and Blood Institute. The combination of symptoms that can occur as a result of a protein deficiency and iron deficiency can leave you feeling weak. To combat these symptoms, eat foods rich in both protein and iron. Animal-based foods, including red meat, poultry and fish, serve as the richest source of complete protein and provide iron in the form most effectively absorbed.