Diet and Fever

Fever and hyperpyrexia

Fever and hyperthermia represent two different pathological mechanisms, but which both generate pyrexia, a NON-physiological condition characterized "by the anomalous rise in body temperature".

1. The fever is triggered by the chemical damage caused by cytokines (chemical mediators) on the hypothalamic central regulation "thermostat", which in turn generates excessive heating
2. Hyperthermia is generated by the imbalance between thermogenesis (production of body heat) or external heating (such as solar irradiation) and the thermodispersion system (skin vasodilation, sweating, etc.) which is followed by a progressive accumulation of heat.

Therapy

From the above, it can be deduced that the therapeutic approach between the two forms of pyrexia is completely different; in hyperthermia it is essential to rapidly cool the body (for example with cold water) while in fever the antipyretic drugs that act by restoring the hypothalamic "set-point" are useful (but also in this case the usefulness of cooling by conduction is not excluded, for example by sponging with cold water).

NB. Treating fever and reducing pyrexia do not always follow the same treatment pathway; in the event of temperature alteration it is first of all essential to identify (if possible) the aetiopathological agent (ie the cause: inflammation, viral infection, burns etc.) responsible for bodily alteration, then eliminate it. The use of antipyretic drugs (such as paracetamol) is useful for reducing the pyretic symptoms of fever but is NOT an effective cure. Obviously, if it is not possible or essential to intervene on the primary cause of the fever, antipyretics are the only applicable pharmacological intervention.

Fever diet

Fever is an ACTIVE process that deliberately seeks to increase body temperature; this condition is metabolically fundamental to accelerate the enzymatic processes of the whole organism, in order to optimize the immune reaction and speed up healing . For this reason it is essential to reduce fever only if it exceeds the tolerance limit of the subject.

From a metabolic point of view, fever significantly increases measurable energy expenditure through basal oxygen consumption; the estimates made on the general population indicate that for each degree centigrade (° C) above 37, the body needs 13% more oxygen to meet the needs of all physiological and para-physiological processes . This means that, with the same energy introduced with the diet, fever (increasing the energetic oxidative processes) can favor the reduction of the reserve energy substrates (fat and glycogen), consequently also decreasing the body weight; having said that, it might seem obvious that in the presence of fever it is essential to modify the diet by increasing the energy intake to cover the minimum requirement for maintaining body weight; for example:

Assuming that the subject "X" normally has an energy expenditure of 2000kcal, in case of fever at 39 ° C (2 ° C over the 37 ° C threshold) it would need a caloric surplus of 26% (13% multiplied by the 2 ° C), or 520kcal. On balance, the subject "X" should correct their diet by increasing their calorie intake as follows:

• 2000kcal + 520kcal = 2520kcal

NB. It is advisable to maintain a normal protein intake and proportionally increase both lipids and carbohydrates.

In the case where the subject "X" maintains an energy intake of 2000kcal and the fever at 39 ° C is constant for 14 days, the algebraic sum between the calories introduced with the diet and the calories burned in the presence of fever would be NEGATIVE giving rise to at a weight loss:

• [(2000 * 14) - (2520 * 14)] = (28000-35280) = -7280kcal

Moreover, knowing that PHYSIOLOGICALLY to eliminate 1 kg of fat it is necessary to burn about 7000kcal, it is possible to state that the subject "x", during 14 days of fever at 39 ° C in which he did NOT follow a proper diet, could suffer a weight loss of about 1kg.

Obviously, this example does NOT take into account the presence of many variables (FOR EXAMPLE THE REDUCTION OF THE LEVEL OF PHYSICAL ACTIVITY) that contribute to determining the final energy balance, therefore it must be considered as an absolute SIMPLIFICATION.

NB. If the reader is seduced by the possibility of facilitating weight loss by NOT treating the fever or the causative agent that generates it, we would like to remind you that the increase in expenditure associated with lodging or immobilization of the patient results in a NON-selective weight loss that negatively affects both on the tropism of muscle mass and on the consistency of liver and muscle glycogen reserves.

In order to have a more realistic picture of the metabolic impact of fever on the organism, the following key points should also be considered:

1. Dehydration : fever generates an increase in body temperature that often requires greater heat dispersion, thus leading to an increase in sweating; therefore, if the diet does not contain sufficient water intake, the reduction in body weight could indicate more general dehydration than depletion of energy reserves. It can be deduced that the fever diet MUST first guarantee the basal water requirement, compensate for sweating and facilitate renal drainage of any pharmacological catabolites
2. The increase of the basic enegetic expenditure is compensated by the physical inactivity of the subject : it is appropriate to consider that (usually) the fever does NOT allow the carrying out of the common working, recreational and sporting activities; whereas the energy expenditure of a person who is stationary in bed is almost superimposable to his basal metabolism (MB, ) while the Physical Activity Level (LAF) fluctuates between + 33% and 110% more than the same basal metabolic rate, it is possible to affirm that normally the diet for the fever of A GUIDED OR SLEEPER should bring an energy quantity LOWER than the one normally introduced with the feeding NOTICE the fever generates a basal increase of 13% every 1 ° C. For example , for the subject "Y" which has a basal metabolism of 1300kcal and a Level of Physical Activity that increases energy expenditure by 55%, FOR A TOTAL OF 2015KCAL, stay in bed with 2 ° C of fever (+ 26% of calories) would mean having a total expenditure of 1638kcal ... BEN 377kcal less than normal!
3. Vomiting and malabsorption linked to the morbid condition : in the case in which the etiological agent is a pathogen (virus, bacteria, protozoa or other parasites), or intoxication with ethyl alcohol or other nerves, and the fever is accompanied by vomiting and diarrhea, the diet must undergo drastic changes. First of all we remember that vomiting and diarrhea cause an accelerated dehydration, therefore, the reduction of body weight correlates above all to the volume deficit (of volume) of the blood plasma; secondly, the inability to retain food in the stomach or decreased intestinal absorption (sometimes severely) reduces the amount of energy and essential elements introduced with the diet. Therefore, in addition to a state of transient general malnutrition, there is a degradation of the reserve energy substrates as well as of muscle tissue (favored by the immobility of the patient) found in the indiscriminate weight loss (both lean mass and fat mass). In this case, the fever diet should promote gastric passage without inducing vomiting and providing for proper digestion and absorption; in this regard, it is very useful to make use of moderately protein foods with a higher content of carbohydrates and vegetable oils (semolina enriched with legumes and seasoned with extra virgin olive oil and a little grated cheese), easily digestible (simple and not prolonged cooking), favor semi-liquid foods (NOT totally liquid, because the digestive tract can react to the sense of fullness with the impulse of vomiting), with moderate and rather frequent portions; moreover, it would be better to AVOID foods that contain nutrients that are difficult to tolerate such as lactose.
4. Transient anorexia : from a behavioral point of view, patients suffering from fever do not feel the need (or physiological stimulus) to eat and drink. If the fever diet is not drawn up and followed carefully, in addition to the risk of malnutrition, reducing the water supply worsens both the heat dispersion potential and the renal filtration capacity; on the latter, on the contrary, it should be encouraged thus facilitating the elimination of endogenous and pharmacological catabolites.

The fever diet must take into account all these factors in order to optimize the healing process and avoid any side effects related to malnutrition; it is advisable to pay particular attention to the water, saline and vitamin content but not to neglect (if possible) the intake of foods containing the other essential molecules (omega 3 fatty acids and amino acids deriving from high biological value proteins).

Fever diet: practical advice

• In the presence of fever, especially if associated with vomiting and / or diarrhea, the first concern is to ensure proper hydration. Generally, in adults, water - drunk in small, frequent sips - is sufficient, while specific rehydrating formulations are recommended in children (eg Pedialyte). In the event of prolonged fasting, it is possible to use specific rehydrating and alkalizing formulations based on sodium and / or potassium citrate (eg biochetases). In case of prolonged vomiting rehydration can also occur intravenously.
• In case of nausea and vomiting, solid oral feeding must be restored gradually as soon as possible, and pursued according to the patient's tolerability: water and rehydrating liquids → jams and fruit jellies → vegetable purée → pasta or rice in broth → meat of veal, chicken and fish, possibly chopped to make it more digestible
• Associated with rest, the diet must be light, therefore containing easily digestible foods without cooking fat. Lipids will be limited to the addition of raw oil and butter as a condiment to dishes.
• The fever diet prefers lean carbohydrates and proteins. Carbohydrates, easy to digest, allow you to save muscle proteins from the catabolic phenomena induced by caloric and carbohydrate depletion; moreover, they allow to avoid ketosis due to hyperactivation of lipid metabolism, typical of prolonged fasting conditions.
• Partially skimmed milk, recommended by some doctors in the presence of fever, should be avoided by lactose intolerant individuals. The text "Reasoned medical therapy" by Aldo Zangara suggests that "the feeding of the patient with a febrile infectious disease is initially based on the consumption of milk - which is introduced as the main food in the average quantity of a liter and a half per day (950 KCal and 46g of protein) - eggs, meat homogenized dissolved in soups, pasta, rice, semolina, biscuits, white bread, cooked and sweetened fruit, drinks, etc. (meat broths have a low caloric value). " Protein sources that are richer in fat and connective (such as muscular bundles, rind, bones) should therefore be avoided, preferring softer and more easily digestible cuts.
• The fever diet foresees the consumption of numerous small rations, to avoid an excessive weighting of the digestive functions.
• Special warnings in certain situations naturally impose that the last word, on the adequacy of a particular diet in case of fever, is the responsibility of the doctor; for example:
  • in the case of prolonged therapy with corticosteroids it is necessary to limit the sodium intake with the diet and increase that of potassium, since these drugs cause sodium retention and increase the excretion of potassium
  • in case of fever associated with diarrhea, dairy products and sugary foods (sweets, jams) should be avoided, as they could aggravate the condition due to osmotic issues. Among the fruit juices - foods known to be useful for water and vitamin rebalancing - those without added sugar, or better still those prepared at home, will be privileged, since sweeteners with a marked laxative effect are sometimes added instead of sugar in industrial products (to example the polyols: sorbitol, mannitol, xylitol and others).
  • dairy products should be taken at least 3-4 hours after oral administration of tetracycline, as they could inactivate the drug by precipitation in the intestine
  • in case of fever associated with severe hepatitis, the diet should be hypoproteic

Bibliography:

• Clinical treatment and surgical therapy . Volume 1 - F. Mazzeo - Piccin - page 54:57