Dan Benardot, PhD, RD, FACSM |
Cold weather and high-altitude sports have certainly been in the news recently. Have you ever wondered if these environments influence nutritional requirements and, therefore, may also have an impact on athletic performance? There is an increasing body of research suggesting that there are many nutritional issues related to cold and high-altitude environments that, if not appropriately dealt with, may seriously impact performance even in the most highly conditioned athlete. It is also important to consider that warm high-altitude environments (think Mexico City, altitude 7,382 feet; 2,250 meters), may also impart a performance advantage because of lower air resistance that an athlete must overcome, provided the athlete is sufficiently adapted to the altitude and is not suffering from one of several forms of altitude sickness.
What are the Potential Nutritional Issues?
Athletes who suddenly find themselves at an altitude exceeding 2000 meters are likely to experience nausea and loss of appetite, both symptoms of acute mountain sickness. This may sound like a minor issue, but failure to eat and drink enough increases the potential for poor muscle glycogen storage, which is needed for high intensity activity. It has been found that food and fluid intake is often 10-50 percent lower in cold/high-altitude environments than amounts consumed near sea level. This problem is intensified because carbohydrates are used at a faster rate at high-altitude—dramatically increasing the risk of early fatigue. Consumption of more carbohydrate than usual may be needed in cold environments because a primary system of sustaining core body temperature in the cold is an involuntary central nervous system-induced event called ‘shivering’, which dramatically increases muscle glycogen usage.
Failure to consume sufficient fluids is also a significant issue, due to higher urine production at higher altitude, with higher risk of dehydration and an associated early fatigue. In fact, trying to maintain a good hydration state in cold and high-altitude environments is just as difficult as maintaining fluid balance in hot and humid environments because of the increased urine production and the voluntary failure to drink sufficient fluids. There may even be an increased risk of dehydration from high levels of water loss if the clothing worn is particularly heat retaining or heavy sporting equipment is being carried (i.e., skis, poles, helmet, etc.).
What Can Physically Active People Do To Satisfy Nutritional Needs?
There is no substitute for adapting to the cold and high-altitude environment. Athletes competing in this environment should try to spend at least four days in this environment prior to competition. This allows the body to make appropriate adaptations to resolve acute mountain sickness. The high-altitude environment is lower in oxygen, so assuring good iron status with no sign of iron deficiency or anemia is important. If performing endurance activity in this environment, spending even more time at high-altitude is important to improve red-cell concentration and oxygen-carrying capacity. Of course, increasing red-cell concentration increases the requirement for selected nutrients, mandating a diet rich in high-iron, high-vitamin B12 foods (red meats, etc.), high vitamin C and folic acid (fresh fruits and vegetables), or a physician monitored intake of nutrient supplementation.
Frequent eating at planned timed intervals, with a focus on high carbohydrate foods is important because carbohydrate requires less oxygen to metabolize for energy than either protein or fat. Insufficient energy intake reduces both strength and endurance, both critical factors in athletic performance. Frequent eating requires advanced planning to make certain there are planned eating times during the day (about every three hours) and available foods that can be easily accessed. Because of the nausea commonly experienced at the beginning of the adaptation process, eating smaller amounts with greater frequency may be a useful strategy to help assure adequate intakes.
Taking weight before and after exercise, and/or at the beginning and end of the day is a good indirect measure of the amount of body water that was lost but not replaced (1 lb = 16 ounces; 1 kg=1 liter). Athletes should monitor how much fluid was consumed and add an amount needed to sustain body weight. If the athlete cannot carry fluid with them, there should be known and available hydration stations that the athlete can access with ease and in high frequency.
It is important to focus on the consumption of high carbohydrate foods to help optimize glycogen stores, which are used at a higher rate in cold and high-altitude environments. Having frequent carbohydrate consumption will also help to sustain blood sugar and, therefore, mental function (the brain is a high consumer of blood sugar). It will also provide a source of fuel to working muscles that does not require oxygen to metabolize.
The Bottom Line:
Plan so that the athlete never gets hungry or thirsty and has enough available energy to compensate for the extra that must be used at high-altitude.
Dan Benardot is a Fellow of the American College of Sports Medicine, a Registered/Licensed Dietitian, and Professor of Nutrition, emeritus, at Georgia State University, where for many years he directed the Laboratory for Elite Athlete Performance. Dr. Benardot has served as nutritionist for several Olympic teams, and for the Atlanta Falcons football team. He co-authored ACSM’s 1993 position paper on ‘Nutrition and Athletic Performance’, and served as a reviewer for the 2009 and 2016 position papers. He has also authored/co-author of several chapters in ACSM publications, several published books, and numerous articles in scientific journals.
For Additional Reading:
Bartsch P, Bailey DM, Berger MM, Knauth M, and Baumgartner RW. Acute mountain sickness: Controversies and advances. High Altitude Medicine and Biology 2004; 5(2): 110-124.
Beidleman BA, Muza SR, Fulco CS, Cymerman A, Ditzler D, Stulz D, Staab JE, Skrinar GS, Lewis SF, and Sawka MN. Intermittent altitude exposures reduce acute mountain sickness at 4300 m. Clinical Science 2004; 106(3): 321-328.
Cheuvront SN, Ely BR, and Wilber RL. Environment and Exercise. In: Maughan RJ (ED): Sports Nutrition: The Encyclopaedia of Sports Medicine: An IOC Medical Commission Publication, Volume 19. Wiley Blackwell: London © 2013, pp 425-438.
Cheuvront SN, and Keneflick RW. Dehydration: Physiology, assessment, and performance effects. Comprehensive Physiology 2014: DOI: 10.1002/cphy.c130017
Paulin S, Roberts J, Roberts M, and Davis I. A case study evaluation of competitors undertaking an Antarctic ultra-endurance event: nutrition, hydration and body composition variables. Extreme Physiology & Medicine2015; 4(3): https://doi.org/10.1186/s13728-015-0022-0
Sawka MN, Cheuvront SN, and Kenefick RW. Hypohydration and human performance: Impact of environment and physiological mechanisms. Sports Medicine. 2015; 45(1): 51-60.