How do our training and nutrition affect our immune system?

In 2012, a study was released “Exercise-Induced Immunodepression in Endurance Athletes and Nutritional Intervention with Carbohydrate, Protein, and Fat—What Is Possible, What Is Not?” Where the authors looked at 150 studies to see what macronutrients were needed and how prolonged endurance exercise and high-intensity interval training can affect our immune system. The study began by saying “multiple factors influence the athlete’s resistance to illness, and the immune system can become functionally depressed. Examples of such factors include genetically predisposed immune competency, inadequate nutrition, physical, psychological, and environmental stresses and alterations in normal sleep schedule.”

To save you some time from reading whole article I have sighted bullet points from each section below.

And to save you more time the results from this study showed:

  • Nutrient availability influences immune function in direct and indirect ways and it can be concluded that a poor nutrition state affects almost all aspects of the immune system. Exercising in a CHO depleted state may result in higher levels of stress hormones and an impaired immune function. This is an important issue to consider in view of new training strategies that involve training with low glycogen of CHO availability.
  • Cyclists and runners desire low body fat and leanness for optimal performance and therefore often follow energy- and/or fat-restricted diets. Training on a very low-fat diet (15% dietary fat) may be detrimental to exercise performance and leads to an overall compromised immune function due to a negative energy balance and micronutrient deficiency. High-fat diets (>39% dietary fat) have also been suggested to be detrimental to the immune system.
  • An overall adequate nutrient availability provided by a well-balanced diet and sufficient fluid delivery may help to maintain immunocompetence in athletes since inadequate nutrition affects almost all aspects of the immune system. In the expanding field of exercise immunology much has been done, but there is still a great deal more to learn.

 

Endurance Exercise and Upper Respiratory Tract Infection (URTI):

The study went on to say that “the relationship between exercise intensity/volume and susceptibility to Upper Respiratory Tract Infections (URTI) has been modeled in the form of a J-curve. The model suggests that moderate exercise may lower the risk of URTI compared to sedentary individuals – it appears to be beneficial to a certain point.”

           

 

So what are the effects of Heavy Exercise on the Cellular Immune Function?

  • Numerous studies have shown that exercise has either a positive or negative effect on immunity. These effects depend on the nature, intensity, and duration of exercise, as well as subject fitness and age and therefore outcomes, are highly variable. In general post-exercise immune function impairment is highest when the exercise is continuous, prolonged (>1.5hr), of moderate to high intensity (50-77% of VO2 max) and performed without food intake.

What’s the influence of Nutrition State on Pre-Exercise Immune Function?

  • Scientific research has long shown that inadequate nutrition may contribute to impaired immunity and makes the individual more susceptible to infection. Energy restricted diets are common in sports, where low body fat is desired, such as running and cycling and could be accompanied by macro- and micronutrient deficiencies. Excesses in specific nutrients, such as carbohydrates (CHO) at expense of the protein, training in a dehydrated state and excessive use of nutritional supplements may also lead to direct and indirect negative effects on the immune function in athletes and may be partly responsible for higher infection risk. Maintaining the normal function of immune cells requires an adequate amount of water, glucose, proteins, and electrolytes. As a logical consequence, meeting nutritional demands helps to maintain an effective immune system.

Carbohydrate, Exercise and Immune Function:

  • It is clear that an adequate amount of CHO availability is a key factor for the maintenance of heavy training schedules and successful athletic performance. Glucose is an important fuel substrate for lymphocytes, neutrophils, and macrophages because metabolic rates of immune cells are extremely high. A low level of blood glucose concentration during prolonged exertion results in higher levels of cortisol, epinephrine and growth hormone. The underlying rationale is that CHO availability and stable blood glucose concentration may limit stress hormone responses (ie: cortisol), provide glucose as an energy substrate for immune cells, and help to maintain immunity.

Dietary Protein, Amino Acids, and Exercise Immune Function

  • It is well accepted that protein deficiency impairs immune function and leads to an increased susceptibility to infection, because the production of some important immune variables, such as cytokines, immunoglobins, and acute-phase proteins, depends on adequate protein availability. The severity of protein deficiency influences the magnitude of immune system impairment, and protein-energy malnutrition may affect all forms of immunity. Therefore, the availability of adequate amounts of all amino acids is required for a maintained immuno-competence.

The Results from this study:

  • Nutrient availability influences immune function in direct and indirect ways and it can be concluded that a poor nutrition state affects almost all aspects of the immune system. Exercising in a CHO depleted state may result in higher levels of stress hormones and an impaired immune function. This is an important issue to consider in view of new training strategies that involve training with low glycogen of CHO availability.
  • Cyclists and runners desire low body fat and leanness for optimal performance and therefore often follow evergy- and/or fat-restricted diets. Training on a very low-fat diet (15% dietary fat) may be detrimental to exercise performance and leads to an overall compromised immune function due to a negative energy balance and micronutrient deficiency. High-fat diets (>39% dietary fat) have also been suggested to be detrimental to the immune system.
  • An overall adequate nutrient availability provided by a well-balanced diet and sufficient fluid delivery may help to maintain immunocompetence in athletes since inadequate nutrition affects almost all aspects of the immune system. In the expanding field of exercise immunology much has been done, but there is still a great deal more to learn.