Nutrition Intervention for Acute Illness

While most people are aware of some of the necessary steps to aid in the recovery from illness, there are certain nutritional interventions that can have a significant impact on recovery. Using research from pathophysiology, we will dig into some of the intricacies of acute illness (common cold, flu, etc.) and what we can do, from a nutritional point of view, to mitigate the damage and speed recovery. In this article, we will discuss why the body needs nutrients to fight illness, nutrient recommendations, and efficient dosing to speed recovery optimally.

Innate and Adaptive Immune Response

While the immune system is, in many respects, a comprehensive system, it is still broken into two “lines of defense”. These two lines of defense are called the “innate” and “adaptive” immune responses [1].

Innate Immune Response

The innate immune system is the first line of defense and is broken up between various subsections including physical barriers (skin, hair, etc.), chemical barriers (pH, stomach acid, etc.), and physiological barriers (phagocytes, cytokines, etc.) [1]. This system is a general line of defense and does not deal with individual bacteria and viruses with individualized stress. However, it does make the overall environment of the body far less hospitable for invasive microorganisms.

The positives of this system are numerous and offer a great initial hit to an invading body; however, there is residual damage to healthy tissue from this system (which, we will discuss in the next section).

What are cytokines?

Cytokines are proteins released by a variety of cells (mainly T-Cells) to fulfill a variety of functions from telling the body about specific inflammation patters, mediating length and intensity of immune response, and activating certain cells with specific cytokine sites to attach [12][13].

What are phagocytes?

Phagocytes are immune cells that engulf or “eat” invading pathogens to then bombard them with stress until they die [14].


Adaptive Immune Response

This is the immune response responsible for “memorizing” pathogen (bacteria and virus) patterns and make up. This system takes days to weeks to fully form, but once it does, it is highly specific and deadly at destroying that particular pathogen [1]. This immune response is made up, primarily, of various forms of specialized pathogen fighting cells [1].

What is a pathogen?

An infectious, biological agent (virus or bacterial) that causes illness to a host (our body, for example) [15].


Why does the body need more nutrients during illness?

There are multiple reasons for the body’s need for more nutrients during illness, here are several of those reasons:


The body increases temperature to create an inhospitable environment for invading pathogens [2]. That said, the increase in temperature must come from an energy source, and that leads to a speeding of metabolism as converting food to energy creates heat [3][4]. Metabolism runs faster as temperature rises, and to attenuate that, the body needs more nutrients.

Fever leads to increase in basal metabolic rate.

The body releases white blood cells, as well as other phagocytes, in an attempt to deal with invading pathogens, yet one of the techniques these phagocytes use is to release reactive oxygen species to destroy the pathogen [5]. The issue with reactive oxygen species is that they are difficult to control and also do damage to healthy tissue [5]. This, in turn, leads to inflammation of the healthy tissue as a marker for future repair. This repair, then, costs nutrients.

What are Reactive Oxygen Species?

This term is used to describe a free radical molecule (molecule missing an electron) that is created within the body for a variety of reasons, but in this case to damage and destroy pathogens during phagocytosis (engulfing pathogens) [16].

Immune Cell Activity

An increase in immune cell synthesis from white blood cells, to lymphocytes, cytokines, and other phagocytes requires nutrients (think of it like resources to build a house) to build these immune cells.

Immune cells like lymphocytes, cytokines, white blood cells, etc cost nutrients to synthesize [6].

Metabolic Changes

Not only do all of the above requirements increase the demand for nutrients, but they also lead to change in metabolic pathway by oxidizing (using) more fatty acids (stored fat, in this instance) to be converted to glucose via gluconeogenesis [7][8]. Also, the body has a tendency to dump amino acids into the blood stream by degrading muscle [7]. As cortisol increases, catabolism takes hold; metabolism favors quick energy through glucose, as well as catabolism of proteins by down regulating protein synthesis, increasing free amino acids to make nutrients available for immune cell and immune specific protein formation [7].

Nutrient Recommendations?

This is a tricky section, because it seems that nutrition does have an impact on overall health and does play a role in recovery, but there is little that nutrition can do during the height of illness. The reasons why? The body basically runs on “low power” mode, in a manner of speaking. Digestive processes, absorption, growth via protein synthesis, among other regular processes are dramatically cut back in an attempt to conserve nutrients to start synthesizing a multitude of immune cells and tagging cells to help fight infection [7][11].

This means, that nutrient intake during the height of infection, especially during a fever, will offer little benefit. However, obviously taking care of one’s nutrition prior to becoming ill can have a possible impact on recovery. Also, since even acute illness is not completely eradicated after the height of its symptoms, nutrition after this initial high stress (high symptom) phase can also help replenish lost nutrients taken from the body during the height of infection as the body begins to normalize back to its pre-infection state [7][8].

That said, taking into consideration that every 2-3 degrees Fahrenheit (1 degree Celsius) increase in body temperature from fever leads to a 7-15% increase in basal metabolic rate (which accounts for 70% of total metabolism), there is a use to increase energy intake for that reason alone. Not only that, increasing caloric intake, but failing to increase protein intake leads to a continuous loss of amino acids as they will continue to be broken down from muscle to attenuate immunological need [7][8][10]. As a result, recommendations are specific to circumstance.

Nutrition recommendations prior to illness are to meet all RDA values for macronutrient and micronutrients, this seems clear enough. As for during the worst time periods of illness where symptoms are severe, nutrition is limited to what you can tolerate – your discretion in amount, type, and dependent on illness type. Finally, after symptoms have begun to dissipate, the body needs nutrients to replenish lost amino and energy reserves; so, it is recommended to consume maintenance calories for energy, as well as .55 - .68 g/lb/day (1.2 – 1.5 g/kg/day) to attenuate protein turn over (this is a high upper limit, so a noticeably lower amount would likely cover any mild illnesses) [11]. In terms of other nutrients, it is always recommended to still reach the RDA in each micronutrient, as well as making sure to reach recommended values of essential fatty acids to help in energy production, as well as cell creation for repair and proper immune function [1].

Finally, if illness brings with it a fever, recommendations stay largely the same pre and during the height of the illness, but as the fever begins to wane, an increase of total caloric intake should be increased by 5-10% (likely 150-300 calories) for the remaining week or two [7][10]. This increase is a general increase to attenuate extra energy loss during the height of the fever, and as metabolism is incredibly hard to calculate during a fever as heat production changes constantly; this is a rough estimate knowing fever increases basal metabolic rate per few degrees of body heat increase [9].

Obviously, these recommendations are still incredibly general and they do not take into consideration several other factors (specificity of illness, medicine interactions, etc.), but as I have seen few articles discuss some ball park method for understanding and applying nutrition to a general infection like a cold, the flu, or other relatively minor, acute illnesses, it was opportune and high time we have some resource. Admittedly, most of the research looks into more chronic and egregious insult to the body (surgery, heavy burns, etc.) so it is difficult to extrapolate from that information as it is far more extreme than acute issues – however, hopefully this will still offer a platform to see some slight improvement in education and recovery. 


Sadly, recommendations for acute illness are hard to come by considering the research tends to focus on more pressing, debilitating illness; however, with the little information we have on immune function, metabolism, and physiology, we can make some calls on improving our recovery from illnesses like the common cold, influenza, and the like. Fever and illness leading to immune response, without a doubt, increases metabolic rate, but normal physiological function from digestion and absorption are disrupted and diminished, so feeding during the height of illness will have diminished effect. However, as fever breaks and a person begins to recover, the recovery process can take from days to weeks (even after symptoms dissipate) and nutrition intervention can be of use during this time. To attenuate metabolic increase, consuming 5-10% more calories, as well as attenuating immune nutrient need, consuming at least .55 - .68 g/lb/day (1.2 – 1.5 g/kg/day) of protein will aid in recovery from acute illness.

Writer: Nicolas Verhoeven


[1] Drake, V. J. (2010, August). Immunity | Linus Pauling Institute | Oregon State University. Retrieved from

[2] What causes a fever? - Scientific American. (2005, November 21). Retrieved from

[3] Baracos, V. E., Whitmore, W. T., & Gale, R. (1987). The metabolic cost of fever. Can. J. Physiol. Pharmacol, 65(6), 1248-1254. Retrieved from

[4] Del Bene, V. E. (1990). Temperature. In Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition (3rd ed.). Retrieved from

[5] Drake, V. J. (2010, August). Immunity | Linus Pauling Institute | Oregon State University. Retrieved from

[6] Rauw, W. M. (2012). Immune response from a resource allocation perspective. Front. Gene, 3. Retrieved from

[7] Wallace, J. C. (n.d.). Gluconeogenesis. Retrieved from

[8] Rayfield, E. J., Curnow, R. T., George, D. T., & Beisel, W. R. (1973). Impaired Carbohydrate Metabolism during a Mild Viral Illness. New England Journal of Medicine, 289(12), 618-621. Retrieved from

[9] Walker, R. N. (2009). Predictive Equations for Energy Needs for the Critically Ill. Respiratory Care, 54(4). Retrieved from


[11] Genton, & Pichard. (2011). Protein Catabolism and Requirements in Severe Illness.International Journal for Vitamin and Nutrition Research, 81(23), 143-152. Retrieved from

[12] Zhang, J., & An, J. (2007). Cytokines, Inflammation, and Pain. International Anesthesiology Clinics, 45(2), 27-37. Retrieved from

[13] Chapter 13: Cytokines [Powerpoint]. (n.d.). Retrieved from

[14] Aderem, A. (2003). Phagocytosis and the Inflammatory Response. The Journal of Infectious Diseases, 187(s2), S340-S345. Retrieved from

[15] Pathogen. (n.d.). Retrieved from


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