By James Penland
Those of us who live in the Upper Midwest know that soldiers, athletes and arctic explorers are not the only ones who must survive and function in extremely cold temperatures. Extreme temperatures, hot and cold, affect not only level of comfort, but also health and ability to perform physical and mental work, and mood. Many studies have documented declines in physical performance and in cognitive skills, such as attention, memory and problem solving, when volunteers are exposed to cold temperatures, even for relatively brief periods of time.
When the heat produced by the body doesn't meet its need, hypothermia results. Shivering is one mechanism the body uses to produce heat during cold exposure. Shivering occurs when the temperature of the blood falls causing the hypothalamus in the brain to stimulate motor activity in the form of rhythmic contractions.
When it's cold outside, the body must work harder to maintain its internal temperature (stay warm) and that requires more fuel or energy in the form of food. When we do physically demanding work, like shoveling snow, in cold environments we may use 50% more energy than we would if that work were done in moderate environmental conditions. Wearing heavy clothing and walking in snow or trying to navigate ice-covered areas also increases the demand for energy.
It is critical to consume enough food and liquid to meet these increased demands. The primary sources of energy in foods are the macronutrients, carbohydrates, fats and proteins. Foods also contain critically important micronutrients, vitamins and minerals.
What role does nutrition play in thermoregulation (the ability to maintain core body temperature in the presence of ever-changing environmental temperatures)? Do other nutrients, such as vitamins and minerals, also play an important role in our ability to thermoregulate and, perhaps, in our ability to maintain physical and mental performance in the presence of cold weather? The answers to these questions are not complete but research has provided some useful information.
Most of the research on nutritional needs in cold weather has been done by the military to determine operational requirements for soldiers. Soldiers of course face many stressors, including threats to life and limb, unfamiliar and often confusing circumstances, and sleep deprivation.
In garrison, the typical male soldier burns 3,200 calories a day and the typical female soldier burns 2,400. When participating in cold weather field training, requirements increase to 4,500 calories a day for males and 3,500 for females.
There have been few controlled studies of the importance of individual vitamins and minerals for temperature regulation. These few studies have shown that chronic deficiencies in iron, copper or zinc can impair thermoregulation. For example, studies at Pennsylvania State University and the Grand Forks Human Nutrition Research Center have shown that people who are iron deficient are unable to maintain their body temperature when exposed to cold water and air, compared to people with normal iron status and equivalent body composition. Iron supplementation improved their ability to maintain body temperature in the cold, clearly showing the importance of iron for thermoregulation. Deficiencies in the vitamins pyridoxine and thiamin may also impair the muscle activity involved in shivering.
In addition to clothing and shelter, a well-balanced diet, including plenty of fluids, is the best protection against hypothermia and maintenance of thermoregulation. Often people are less thirsty in cold weather. And the less they drink, the less they eat.
Future research needs to further investigate the role of specific nutrients in thermoregulation and maintaining physical and mental performance while living and working in cold environments, and whether chronic exposure to the cold increases the demand for certain nutrients.
Here are a few cold weather nutrition tips, based on the guidelines established by the military for soldiers in cold environments.
- Drink plenty of water;
- Increase energy intake 25-50% in the form of a well-balanced diet containing a variety of foods;
- Eat regular meals and consume snacks throughout the day;
- Eat hot, palatable food when possible;
- Moderate coffee and caffeine consumption;
- What would guidelines be without a few Don'ts? Don't drink excessive alcohol when you'll be outside in the cold for extended periods of time. It's a myth that alcohol warms you up; in fact, it increases heat loss.
You likely will not need vitamin or mineral supplements if adequate energy to maintain body weight is consumed from a variety of foods. However, supplements may advisable if you restrict your energy intake by severe dieting, avoid whole food groups, or consume high-carbohydrate diets with a low micronutrient density.
Stay warm this winter, but when you must be out in the cold (especially for long periods), remember to eat a balanced diet and avoid excessive alcohol! Maybe it won't be so scary the next time "the weather outside is frightful".