Carbohydrate supplementation and the immune system

This is the first of three short blogs taken from the latest Exercise and Immunology Review. We will be looking at the effect of the macronutrients on exercise and the immune system. Up first, we have carbohydrate and endurance exercise. 

From the point of view of performance, the benefit of carbohydrate during endurance exercise is well established. During long training sessions and competitions, the recommended amount of carbohydrate is between 30-60g/hr and up to 90g/hr for very long events such as Iron Man. The primary aim of ingesting this amount of carbohydrate is to maintain blood glucose levels but it appears that it also has an indirect effect on the immune system. As we exercise, we increase the level of stress hormones within our body (adrenaline, noradrenaline and cortisol) and these hormones impair immune function. Illness and infections are common among athletes and I am sure we have all experienced the inconvenience of having to cut our training short due to illness. While following an habitually high carbohydrate diet does not seem to have much of an effect on immune function compared to a low carb diet, in other words, they both show similar levels of post-exercise immune depression, supplementing with carbohydrate during exercise does have an effect.

As plasma glucose falls during exercise, plasma cortisol rises. Cortisol stimulates protein catabolism and gluconeogenesis (formation of glucose from non-carbohydrate sources), it also has a potent anti-inflammatory and immune depressive effect. While there is sufficient evidence to show that supplementing with carbohydrate during endurance exercise attenuates the body’s cortisol response through maintaining plasma glucose levels, there are also reports of carbohydrate having a beneficial effect on immune function regardless of plasma cortisol levels. Simply put, carbohydrate supplementation during exercise appears to diminish the post exercise reduction in immune function. However, the catch is that the benefit of carbohydrate supplementation on immune function doesn’t appear to have an effect on the incidence of URTIs otherwise known as a cold.

The practical application

Whilst it appears that supplementing with carbohydrate may not lessen your chances of catching a cold, it does help to keep your immune system functioning when faced with the stress of exercise. This is obviously useful in terms of recovery from URTIs and fighting off other infections. I would also consider the link between carbohydrate and immune function when planning training sessions and would avoid any high intensity work during periods of low-carb or fasted training. I would probably also avoid placing a period of such training immediately after a block of high intensity training.  

Reference

Berman S et al. (2017) Immunonutrition and Exercise Consensus Statement. Exercise and Immunology Review: Vol 23

How Much Carbohydrate Do We Need (For Sports) ?

In sports nutrition, whatever the question is, the answer is usually, “it depends”. While this answer may seem very vague there really is not a one size fits all approach to nutrition and especially to sports nutrition. When it comes to how much or how often you should eat carbohydrate, protein, fat etc. etc. it really does depend on how often you train, the intensity you train at and the type of activities you do. When it comes to planning your nutrition for sport, you must think about the amount of carbohydrate you need.

Carbohydrate is the fat of the 21^st century! All our food woes are the fault of carbs and all our ills will be cured by removing carbs from our diet. Of course I’m (slightly) exaggerating here but carbohydrate has got a pretty bad reputation at the moment.

If your goal is to lose weight, reduce body fat and so on then adopting a low carbohydrate diet is worth considering. However, as covered in our previous post about low-carb diets, if you regularly practice a sport that has periods of high intensity effort then carbs are your friend. 

How much you need depends on several factors including but not limited to:

• Type of exercise you do
• Intensity
• Frequency
• Duration
• Recovery 

Another important point to remember when thinking about carb intake is, where are you in your training programme? We all know the importance of periodisation when it comes to your training, well the same must be taken into account when thinking about your nutrition. Your nutrition needs will not be the same for a leg session in the gym as they would be for a 130km bike ride so it is important to match the nutrition to the exercise.

Below are some tables that are a useful guideline to refer to when thinking about your carbohydrate needs. Of course these are guidelines and not set in stone but they are a good starting point for you when you think about planning your pre/during/post training meals. 
  
Obviously if you are currently going through some fasted training and/or are trying to reduce body fat, increase fat oxidation etc. these tables may not be appropriate. 
They are aimed at people who are currently in or are about to enter into a block of training with medium to high intensity.

The tables have been adapted from the ACSM publication “Nutrition and Athletic Performance” which can be found here

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General Carbohydrate Needs Depending on Intensity of Exercise 

 Fuelling Strategies for Pre-Exercise 

 Carbohydrate Needs During Exercise 

 

Obesidad e inflamación crónica

Cuando el sistema inmunitario está activado nuestro cuerpo se convierte en un campo de batalla entre las células inmunitarias y el invasor. La respuesta inflamatoria es iniciada por nuestro cuerpo y a menudo nos sentimos mal, muy mal.

Normalmente cuando el ofensor ha sido eliminado, ej. un virus, nos encontramos mejor. Sin embargo, hay ocasiones en las que lo que sea que estuviera activando nuestro sistema inmunitario se queda en nuestro cuerpo y se produce un estado de inflamación crónica. En este estado no sólo nos sentimos fatal, sino que además, este estado de inflamación crónica ha sido vinculado con enfermedades cardíacas, renales, cáncer y Alzhéimer. 
 

Hay varias causas de inflamación crónica: a menudo es debido a una infección que ha persistido en el cuerpo y que el sistema inmunitario no ha podido eliminar y sigue luchando contra ella. Heridas que no se han curado también son causas frecuentes: los patógenos pueden entrar a través de una herida abierta por lo que el sistema inmunitario está en un estado de activación continua.  

Sin embargo, hay causas no infecciosas de inflamación crónica, como tumores o enfermedades autoinmunes. Recientemente la obesidad también ha sido vinculada con la inflamación crónica.

En principio parece muy raro, ¿cómo puede activar al sistema inmunitario la grasa de nuestro cuerpo? La realidad es que han descubierto que la grasa que rodea los órganos (los adipocitos viscerales) también puede secretar citoquinas proinflamatorias como TNF-α e IL-6. Las citoquinas son proteínas que funcionan como mensajeros entre las células. Cuando tienes una infección, las células inmunitarias secretan las citoquinas proinflamatorias que arrancan la respuesta inflamatoria. Pero ahora parece que no sólo las células inmunitarias pueden activar esta respuesta. 

No está claro por qué esas células arrancan la respuesta inflamatoria, pero ha sido sugerido que el aumento de los ácidos grasos libres y lípidos que son vinculados con la obesidad provocan una respuesta de estrés que quizá sea la responsable. 

Sin embargo, este estado de inflamación crónica nos da una explicación sobre el enlace entre la obesidad y diabetes tipo II. Las citoquinas TNF-α y IL-6 inician una cascada en la que al final inhiben la función de los receptores de la insulina, lo que produce resistencia a la insulina y finalmente diabetes tipo II. 

Ya sabemos que las consecuencias de la obesidad son muy graves, pero ahora es posible que las consecuencias sean más graves de que pensábamos. En el mundo desarrollado la obesidad ya es el mayor problema de salud pública y no podemos malgastar más tiempo en luchar contra ella.  

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Reference 

 Owen J, Punt J, Stranford S, Jones P. Kuby Immunology. Seventh ed: MacMillan Higher Education; 2013.

Obesity and Chronic Inflammation

When the immune system is activated our bodies become a battle ground between our immune cells and the unwelcome invader. Our bodies initiate what is called the inflammatory response and we usually feel pretty rotten. Normally, once the offender is removed be it bacteria, virus or allergen, we start to feel better. However, there are occasions when whatever was stimulating the immune system remains within the body and a state of chronic inflammation occurs. Being in a state of chronic inflammation not only feels pretty awful it also has been linked to conditions such as heart disease, kidney disease, Alzheimer’s and cancer.

There are numerous causes to chronic inflammation, usually an infection has persisted within the body somewhere and the immune system has not been able to clear it properly and so is continuing to fight it. Wounds that have not healed properly are a common cause, the open wound is allowing access to pathogens and so the immune system is in a continued state of activation.

However, there are non-infectious causes to chronic inflammation, tumours or autoimmune diseases for example, what is more worrying though, is that recently obesity has been linked to chronic inflammation.

At first glance it seems rather strange, how can body fat have anything to do with the immune system and therefore inflammation? Well as it turns out the fat cells that surround the organs (visceral adipocytes) also secrete pro-inflammatory cytokines such as TNFα and IL-6. Cytokines are protein molecules that act as messengers between cells, when you have an infection your immune cells will release pro-inflammatory cytokines to kick start the immune response. But it now appears that the immune cells aren’t the only cells that can initiate this signalling.

What initially causes these cells to begin an inflammatory response is not clear but it has been suggested that a stress response due to excessive lipid build up and an increased amount of free fatty acids that are both associated with obesity may be involved. This state of chronic inflammation does however provide an explanation to the link between obesity and type II diabetes, TNFα and IL-6 initiate a chain of events that ultimately inhibit the function of the insulin receptor, this leads to insulin resistance which eventually leads to type II diabetes.  

As mentioned before, chronic inflammation is also linked to other diseases and with obesity becoming THE health problem of the developed world we cannot afford to waste any more time in tackling it.

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Reference 

 Owen J, Punt J, Stranford S, Jones P. Kuby Immunology. Seventh ed: MacMillan Higher Education; 2013.

Cantidad de proteina necesaria para una buena dosis de leucina

En nuestro post sobre proteína después del ejercicio te hablamos sobre la importancia del amino ácido leucina. Este amino ácido es un componente clave para la síntesis de músculo. La evidencia científica más actual nos asegura que con cantidades de leucina de 20-45mg por kg de peso corporal, la síntesis de músculo está optimizada^1,2. 

Pero no caigas en la trampa de “más es mejor” y pienses que más leucina te va convertir en Arnold Schwarzenegger!. Parece que hay un límite de ingesta-síntesis de proteína con lo que cantidades de leucina de más de 45mg/kg no son beneficiosas³.

Aquí abajo está la tabla³ utilizada en el estudio de Moore et al. ¹ y Pasiakos et al. ² que nos ofrece consejos prácticos de cantidades de proteína que necesitamos para obtener 45mg de leucina por kg de peso corporal. 

Utiliza esta tabla como una guía cuando planifiques tu comida después del ejercicio para conseguir una dosis óptima de leucina.

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References 
1.Moore, D. R., M. J. Robinson, J. L. Fry, J. E. Tang, E. I. Glover, S. B. Wilkinson, T. Prior, M. A. Tarnop-olsky, and S. M. Phillips. 2009. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. American Journal of Clinical Nutrition 89 (1): 161–168.

2.Pasiakos, S. M., H. L. McClung, J. P. McClung, L. M. Margolis, N. E. Andersen, G. J. Cloutier, M. A. Pikosky, J. C. Rood, R. A. Fielding, and A. J. Young. 2011. Leucine-enriched essen­tial amino acid supplementation during moderate steady state exercise enhances postex­ercise muscle protein synthesis. American Journal of Clinical Nutrition 94 (3): 809–818.

3.B.I Campbell 2014, Sports Nutrition: Enhancing exercise performance. CRC Press