THIS WEEK IN PRO CYCLING
Nutrition advice for athletes: Keeping your immune system strong for winter training
Cold and flu season are still lingering and with your training programswitching into higher gear for the 2005 racing season, nutrition strategiesfor staying healthy remain a top priority. You don’t want a viral infectionto slow down your workouts and hamper your fitness, so that you can berace ready for this season. This column focuses on some nutritionalstrategies that you can practice in both your daily diet and nutrient supplementation,and specifically around training sessions in order to give your immunesystem a good boost.From a nutritional perspective, it is key to prevent deficiencies andconsume optimal amounts of nutrients that play an essential in maintaininga healthy immune system. Periods of heavy training are also associatedwith a depressed immune function and compromised immune function can befurther aggravated by inadequate nutrition. The body’s susceptibility toa respiratory infection can be elevated for 24 hours after a tough workout,and a demanding race can impair your immune function for one to two weeks.Combining training with school and/or work can overtax an endurance athlete’sresources, stress your body and compromise your ability to fight infection.You are also likely to be exposed to individuals with a cold or the fluover the next few months. A strong immune system should result in fewercolds or viruses, and if you do get sick, recovery should be quicker.Your Daily Diet and Supplementation
Because increased oxygen utilization during exercise can increase theproduction of free radicals (unstable molecules that can cause tissue damageat the cellular level), increased food intake and supplementation withantioxidants may enhance immune-system performance. One of the nutrientsmost commonly associated with preventing colds is vitamin C, which hasa widespread reputation as an immune system booster. While a multivitaminmineral supplement easily provides the Daily Value of vitamin C, don’tunderestimate the importance of consuming good food sources of this vitamin.Endurance athletes can consume over three servings of fresh fruit dailyand up to two cups of cooked vegetables daily for ample amounts of dietaryvitamin C. Most research measuring the effects of high doses of vitaminC through supplementation have not shown additional protection to the immunesystem, though many athletes swear by their vitamin C supplements. Whatwe do know is that a daily dose of 250 mg is adequate to your saturatebody stores with vitamin C. Excellent sources of vitamin C include sweetpeppers, citrus fruits and juices, strawberries, cantaloupe, kiwi fruitand broccoli.Two South African studies have produced encouraging results regardingvitamin C supplementation. One study had athletes supplement 600 milligramsof vitamin C for three weeks before a 90 km ultramarathon. The supplementedrunners experienced fewer upper-respiratory infections in the two weeksfollowing the race. A following up study confirmed these results, thougha recent study is not as encouraging. Athletes supplemented with 1500 milligramsof vitamin C for seven days before a 90 km ultramarathon did not demonstrateenhanced immune function or decreased oxidative stress. While there islimited data on the adverse affects of high levels of vitamin C supplementation,doses in excess of 1000 milligrams could result in some gastrointestinalside effects.Regardless of your level of supplementation, sticking with a high intakeof fruits and vegetables should pay off immune wise. They contain hundredsof phytochemicals that provide many preventative health benefits, and arealso excellent sources of carotenoids that boost the activity of whiteblood cells called lymphocytes. Beta-carotene can also be converted tovitamin A in your body, an important nutrient for the immune system.Other nutrients essential for a strong immune system include adequateintakes of zinc, iron, and vitamins B6 and B12. A good daily multivitaminand mineral supplement providing 100-percent of the Daily Values ensuresadequate intake of these nutrients on top of a well-balanced diet. Megadosingwith vitamins and minerals can often compromise the immune system, especiallywith excessive intakes of iron, is not advised as this couldimpair immune function and increase susceptibility to infection. Whileiron is an important mineral for endurance athletes, iron supplements shouldbe taken as required with regular monitoring or iron status. Excess ironcan increase inflammation in the body. Research on zinc supplementationand the common cold is split down the middle in regards to effectiveness.While there is limited evidence that zinc supplementation can reduce theseverity or duration of a cold, it appears that zinc must be taken within24 hours of the onset of symptoms to provide any benefit.Vitamin E is also a popular antioxidant nutrient, but one recently publishedstudy has suggested that large supplemented doses may produce negativeeffects in athletes. Triathletes took an 800 IU dose of vitamin E for twomonths before competing in an Ironman. When compared to a placebo, thevitamin-E supplemented group experienced more oxidative stress and a greaterinflammatory response. It is important to keep in mind that very high dosesof antioxidants can produce a harmful pro-oxidant effect and potentiallyimpair your body’s immune-system response. Right now many experts considera dose of 200 IU to be safe. Strict dieting and chronic inadequate calorieintake can also compromise your immune system.Calorie balance and essential fatty acids
Rapid weight loss of greater than 2 pounds per week (an amount oftenrecommended by many diet programs) can have negative immune effects. Consumingadequate calories is of course also beneficial for an athlete’s recoveryand energy levels. Poorly planned and low calorie diets can also be lowin protein, which also compromises your immune system. Diets too low inenergy can also result in inadequate intake of immune boosting vitaminsand minerals.Having the proper balance of fat in your diet, and choosing good fatscan also give your immune system a boost. While a very high fat diet cancompromise immune function, a very low fat diet does not provide adequateamounts of essential fat acids. Polyunsaturated oils that provide omega-6and omega-3 fatty acids are good for the immune system. However, most NorthAmericans consume enough of the omega-6 fats (if not an excess) and needto increase intake of the omega-3s. Walnuts, fatty fish, and flax, soy and canola oils are good sources of this healthy fat.Nutritional strategies around training
Besides consuming a healthy diet and supplementing wisely, specificnutrition strategies around training are also beneficial. When your immunesystem is compromised from training, this effect is related to elevatedconcentrations of stress hormones. Nutritional strategies to boost theimmune system around training sessions focused on reducing the stress hormoneresponse, less disturbance in blood immune cell counts, and lower oxidativeactivity. Some of the most important nutritional strategies center aroundcarbohydrate intake before, during, and after training- a familiar practicefor endurance athletes.So training with optimal stores of carbohydrate not only provide fuelfor your workouts, but supports a strong immune system. Endurance athleteswho train in the carbohydrate depleted state experience greater increasesin the stress hormones that increase during exercise. Consuming carbohydratebefore, during, and after endurance exercise seems to diminish some ofthe immunosuppressive effects of intense training. Carbohydrate intakebefore, during, and after training results in lower cortisol levels, fewerchanges in blood immune cell counts, lower oxidative activity, and a diminishedinflammatory response.Overall, good dietary carbohydrate replacement in your daily diet thatmatches your training session (based on intensity and volume) supportsyour immune system. When you train for longer periods, the carbohydratethat you consume (usually in the form of a sports drink), also decreasessome of the immunosuppressive effects of endurance training. Afterhard training, give your fuel stores a nutritional boost by consuming 50to 75 g of carbohydrate afterwards, along with 10-15 g of quality proteinto start the recovery process. This is especially important, as there isa window of at least several hours of depressed immune function after hardexercise. Try to stay away from individuals who have colds after hard training.Of course managing life stress, getting adequate amounts of sleep alsosupport a healthy immune system.
Monique Ryan, MS, RD, is author of "Complete Guide to Sports Nutrition,"and "SportsNutrition for Endurance Athletes," from VeloPress, and the upcoming
