Protein is a macronutrient composed of amino acids that serves as the foundation for all cells and tissues in the body. When a person is sick, the body’s metabolic demands increase as it mobilizes resources to fight the infection and repair damage. Protein, normally needed for maintenance, becomes even more important for recovery. Adequate protein provides the necessary building blocks to support the immune system and counteract the body’s tendency to break down its own tissues for fuel.
Protein’s Role in Immune System Function
The immune system relies heavily on protein for its structure and communication network. Proteins are the core components used to build new immune cells, such as white blood cells, which are the body’s primary defenders against pathogens. These cells are constantly being produced and deployed during an active infection, demanding a steady supply of amino acids.
Protein is also the sole building material for antibodies, also known as immunoglobulins. Antibodies are Y-shaped proteins that bind specifically to invaders like viruses and bacteria, tagging them for destruction by other immune cells. Without sufficient protein intake, the body’s ability to manufacture these targeted defense molecules is compromised.
The immune system uses signaling proteins called cytokines to coordinate its response. Cytokines act as chemical messengers, telling immune cells where to go and what actions to take, such as regulating inflammation. The production of these messenger proteins requires amino acids, directly influencing the speed and effectiveness of the body’s defense strategy.
A conditionally essential amino acid called glutamine, derived from protein, serves as a primary energy source for many immune cells. When the body is under the stress of illness, its demand for glutamine increases dramatically, and the body may not be able to produce enough on its own. Ensuring adequate protein intake helps supply this fuel, keeping the immune system energized.
Counteracting Muscle Wasting During Illness
Illness, especially with fever or systemic inflammation, puts the body into a catabolic state where tissues are broken down faster than they are built up. This process is driven by the stress response and hormones like cortisol. The body prioritizes immune function, often turning to skeletal muscle tissue as a reserve of amino acids to fuel the intense immune response. This breakdown results in negative nitrogen balance, where nitrogen excretion exceeds consumption.
Losing muscle mass leads to generalized weakness and slower recovery. Consuming extra protein mitigates this muscle degradation by supplying necessary amino acids externally. This slows the rate at which the body must break down its own lean mass.
Maintaining muscle strength is important for mobility and physical function during and after recovery. Protein consumption supports muscle protein synthesis, helping preserve strength and accelerate the return to normal activity levels. Supplying protein minimizes muscle wasting and supports tissue repair once the infection subsides.
Determining Protein Needs and Best Sources While Sick
The body’s protein requirements are elevated during illness due to immune function demands and the catabolic state. A healthy adult needs around 0.8 grams of protein per kilogram of body weight daily, but the needs of an ill person increase significantly. Depending on illness severity, recommendations range from 1.2 to 2.0 grams of protein per kilogram of body weight per day.
A major challenge when sick is a poor appetite, making it difficult to consume large portions of food. Focus on easily digestible, nutrient-dense protein sources that are gentle on the stomach:
- Soft-cooked eggs, such as scrambled or poached, are easily broken down.
- Broths, particularly chicken or bone broth, offer protein and hydration in a soothing liquid form.
- Dairy products like plain yogurt and cottage cheese provide high-quality protein and often contain probiotics.
- When solid foods are tolerable, lean, ground meats or soft fish like salmon provide complete proteins without being too heavy.
- Protein shakes or liquid nutritional supplements are a simple, calorie-dense way to meet elevated protein needs when appetite is severely limited.