Diet diary: The curious case of declining immune function in athletes

Mumbai, April 16
Change is key to human evolution but while it may sound contradictory, high levels of high-intensity physical activity among athletes has been found to increase health risks. Elite athletes have been found to be at risk of developing immune system-related disorders like auto-immune disorders, and gastrointestinal disturbances like bloating, cramping, nausea, and vomiting. Not many realise that strenuous exercise and physical activity can compromise immunity. Research indicates that athletes are at an increased risk of upper respiratory tract infection, especially during periods of heavy training. This increased risk is most likely due to changes in the intestinal permeability, also called ‘Leaky Gut’.
Exercise alters healthy gut flora, allowing toxins to enter the bloodstream and increase inflammation. Altered gut flora and intestinal permeability also poses the risk of malabsorption, putting athletes at risk for developing multiple nutritional deficiencies, especially vitamins and minerals. Common ones include Vitamin B12, Iron, Vitamin D, and Magnesium.
Reduced intestinal blood flow as well as increased core temperature can damage the intestinal lining (mucosa), disrupting the tightly regulated intestinal barrier and lead to a systemic inflammatory response.
Another mechanism suggests immuno-suppressive actions of stress hormones such as adrenaline and cortisol. Other factors that affect are intensity, duration and mode of exercise and inadequate food and supplement intake.
A balanced diet with adequate intake of macro (proteins, carbohydrates and fats) and micro (vitamins and minerals) nutrients is essential for good performance and to prevent immuno-suppression. Inadequate protein has been found to impair immunity and increase incidence of infection. Individuals at-risk of inadequate protein intake include vegetarians and those involved in weight restricted sports (wrestling, boxing, rowing, horse racing), aesthetic related sports (gymnastics, figure skating, diving, dancers) and endurance athletes.
On the flip side, excess animal protein can also pose a health risk. Quality and quantity of fat intake is equally important in maintaining good nutritional status and effective performance. Essential fats especially the n-3 fats (omega-3 fats found in fish) have anti-inflammatory properties. A low carbohydrate intake with low fibre is also thought to contribute to immuno-suppression by increased production of stress hormones and depletion of glucose, a key substrate for immune cells. Research indicates that consuming adequate carbohydrate days before strenuous exercise helps prevent suppression in immune function that occurs
Adequate carbohydrate intake to meet daily fuel requirements is a key strategy to protect immune function following prolonged strenuous exercise. Good fibre intake in periods of non-exercise helps to build up healthy gut flora owing to its prebiotic effects.
Hydration is critical during and after the exercise sessions. Dehydration has been known to induce stress on the body as well as increase neuro-endocrine hormones which can result in depression of the immune system.
In a nutshell, factors for the maintenance of optimum immune function include an adequate dietary intake of fibre, carbohydrates, proteins and specific micronutrients including vitamins A, C, E, B6 and B12, and iron, zinc, copper and selenium; prebiotic and probiotic supplements. Current opinion is that athletes should invest in nutrient-rich foods and fluids that provide energy, a wide range of vitamins, minerals and other important substances, such as phyto-chemicals, found naturally in foods. Along with this, current strategies focus on gut health to restore gut flora, and support the leaky gut.
Do’s for athletes:
* Maintain a healthy diet providing adequate fuel for training and recovery, with a good mix of essential nutrients including carbohydrates, proteins and essential fats.
* Support digestive health
* Address nutritional deficiencies before, during and post training.
* Include nutritional supplements, only under the supervision of a qualified physician.
* Take proper rest following training and performance. Manage training loads and daily physical activity associated with work and other routine activities.
* Limit high intensity exercise bouts.
* Ensure adequate (quality) sleep.
* Prevent illnesses and minimize exposure to germs and bugs by practicing good hygiene.
* Manage psychological stress including stress associated with work, family, training and

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