Successful training is a key factor in an athlete’s performance. It can help to improve the skills and fitness required for upper levels of physical activity. Unfortunately, many athletes do not pay adequate attention to a foe aside from their obvious competitors – their own immune system. Illness can mean the athlete loses training time and may be unable to train at an adequate level. It also can affect motivation and mental toughness often required by upper-level athletes. Bouts of illness or even just not feeling their best can interfere with the rhythm and habitual nature of ongoing training. Moderate levels of exercise actually reduce the risk of illness or infection and can be anti-inflammatory. As training increases, however, there is evidence of reduced immune system strength. Longer and more intense bouts of exercise can lower resistance to illness.
Numerous factors Numerous factors can contribute to this change in immunity. Lifestyle issues such as impaired sleep duration or quality, over-training with inadequate recovery, improper diet, weight loss, dehydration or chronic emotional stress can lower immune protection. Environmental factors may also play a role – exercising at higher elevations, exposure to air pollution or extensive traveling, for example – in challenged immunity and increased illness risk. Some of the physical post-exercise changes in the immune system appear to be because of the production of stress hormones and biochemical changes in the body. Acute and chronic physical activity can affect the number and function of the immune system “army” in the body. Chronic emotional stress also increases the release of substances like cortisol that negatively affect the immune system.
Dietary concerns With regard to dietary factors, inadequate intake of carbohydrates, protein and a number of micronutrients (vitamins, minerals) and phytonutrients can all compromise the immune system. Athletes looking for a competitive edge sometimes turn to high intakes of supplemental nutrients with the idea that “more is better.” For some nutrients, high doses can actually impair performance and in some cases, lead to toxicity. Also, research suggests excessive doses do not improve performance any more than adequate intakes. The exception would be athletes testing low in iron or vitamin D who may need higher amounts. Protein intake: Balance is important for protein intake. as well. Athletes should strive to consume adequate, but not excessive, amounts. Vegetarians and athletes in aesthetic or weight-sensitive sports such as gymnastics, dance, ice skating and endurance running who may be limiting their food intake are often at higher risk for inadequate protein intake. Carb intake: Although carbs have gotten a bad reputation from popular weight-loss diets, low carb intake can lower immediate and stored energy. This can trigger a stress response that can negatively affect the immune system if it continues over an extended period of time. Sources of carbs should be consumed before, during and after extended bouts of activity. Nutrients: Nutrients specifically known to be related to immune system function include iron, zinc, vitamins A, E, B6, B12 and possibly vitamin D. As athletes increase their calorie intake with more strenuous activity, the implication is their total nutrient intake increases to potentially cover any increase in need. Insufficient calories or a nutrient-poor diet can lead to deficiencies. To consume a wide range of nutrients needed for optimal performance, a healthy diet containing a variety of foods is recommended, with possibly a basic multiple vitamin instead of megavitamins. Athletes should focus on nutrient-rich foods – fruit, vegetables, whole grains, lean proteins, beans, nuts, seeds, some healthy fats and calcium sources – rather than food/beverages containing “empty calories.” This is especially important for athletes who are still growing and developing. A healthy diet also supports a better balance of intestinal microbes that can assist with immune function. Fluid intake Inadequate fluid intake can counter immune function, too. Exercising in cold or dry environments affects mucous membranes that otherwise assist with keeping out microbes. During a training season is not the best time for weight loss. As noted above, inadequate amounts of calories, macro- and micro-nutrients will work against training efforts, make recovery more difficult and increase physical stress – all of which can lead to increased risk of illness. Reducing exposure to microbes is helpful, as well. This means attention to personal hygiene, limiting exposure to people who are ill and trying to limit time spent in group settings (especially difficult for team athletes).
Over-training Over-training is another cause for lowered immunity. Cumulative over-training is especially problematic. Recovery is extremely important. This means sufficient time for the body to repair itself, for energy stores to be replaced and for replacement of depleted nutrient stores. Athletes noticing any reduction in energy levels, extreme fatigue, moodiness, poor concentration, more frequent bouts of illness or reduced performance should play detective as to why. By getting to the root of the problem and making any necessary lifestyle changes, these symptoms can often be reduced. A better goal would be to prevent a potential downward spiral of performance by maintaining positive lifestyle habits as an integral part of training.
• Pam Stuppy, MS, RD, CSSD, LD, is a registered, licensed dietitian with nutrition counseling offices in York, Maine and Portsmouth, Ore. She is also the nutritionist for Phillips Exeter Academy and is board certified as a specialist in sports dietetics. Visit www.pamstuppynutrition.com for nutrition information, some healthy cooking tips and recipe ideas.