Vitamin and Mineral Needs

In addition to increased energy requirements, increased intakes of many of the vitamins and minerals may be useful for maintaining performance when working for prolonged periods in the cold. Vitamin and mineral recommendations have been developed to account for possible increased requirements based on intake data from field studies, urinary excretion of nutrients, and other measures of "nutrient status". Table 12-2 presents the suggested additional amount of some nutrients that may be needed when working in the cold. See Chapter 2, Table 2-2 and Table 2-3 for a list of food sources for these nutrients. In most cases, if you meet your energy requirements by eating all ration components, you should be meeting your vitamin and mineral needs.

Table 12-2. Suggested Additional Intakes of Micronutrients During Cold Weather Training

Nutrient

Suggested Increase*

Nutrient

Suggested Increase

Vitamin B₁ (Thiamin) 3 mg

Vitamin B₂ (Riboflavin) 2 mg

Vitamin B₃ (Niacin) 5 mg

Pantothenic Acid 5 mg

Folic Acid 200 µg
Vitamin B₁₂ 1 µg

Magnesium 200 mg

Zinc 5 mg

Adapted from Reynolds RD. (1995) Effects of Cold and Altitude on Vitamin and Mineral Requirements. In: Marriot BM (Ed). Nutrient Requirements for Work in Cold and High Altitude Environments. Washington, DC: National Academy Press. *Amounts in addition to the RDA (see Chapter 2).

Tips for Maintaining Performance in a Cold Environment

♦ Check weather conditions, dress appropriately, and avoid profuse
sweating.

♦ Allow for a longer warm-up.

♦ Replenish CHO and electrolyte losses.

♦ Drink plenty of fluids and try to avoid substances that cause
dehydration (see page 93 and Table 12-1).

♦ Be aware of the signs of cold injury (see Chapter 13).

♦ Eat snow only after melting and purifying it.

Altitude

Ascent to altitude can cause a variety of physiologic disturbances due to the drops in temperature and humidity, and the lack of oxygen. Some major concerns are weight loss, disturbances in digestion, and vitamin, mineral and fluid needs.

Physical performance can suffer dramatically with changes in altitude. The lower oxygen concentrations at altitude can reduce aerobic capacity by 1-2% every 100 meters (328 feet) above 1,500 meters (4,918 feet). Many adaptations occur during extended exposure to high altitudes including:

♦ Increased number of oxygen-carrying proteins in the blood
(hemoglobin) and muscle.

♦ Increased density of blood vessels to and within the muscle.

♦ Increased rate of respiration.

Adequate nutrition can play a crucial role in maintaining performance.

Energy Needs

Energy requirements are 15-50% greater than at sea level

Virtually all persons who go to altitude experience weight loss and loss of lean body mass. At altitudes below 5,000 m weight loss can be prevented by increased caloric intake; whereas above 5,000 m, a 5-10% weight loss is inevitable. Some reasons for weight loss at high-altitude are:

♦ Energy requirements are 15-50% greater than at sea level.

♦ Decreased appetite and sense of taste.

♦ Loss of body water from increased breathing rate and dry air.

♦ Impaired absorption of nutrients.

♦ Acute Mountain Sickness (AMS) - symptoms include headache,
nausea, vomiting, fatigue and poor appetite.

Worksheet 12-3. Calculate Your Energy Requirements at Altitude

Your Estimated Energy Requirement (EER) =____________ kcal/day

(see Chapter 1)

A 50% increase in energy requirements equals:

_________ EER x 0.50 =__________ kcal/day

Your total energy requirement equals:

__________ EER +________ 50% increase=________ kcal/day

У

A high-CHO diet (60% of total daily kcals) is preferred at altitude because it restores glycogen, requires less oxygen to metabolize than a high-fat diet, and can blunt or delay the severity of AMS symptoms.

Vitamin and Mineral Needs

Vitamin and mineral needs are likely to increase at altitude. In particular, the increased metabolic rate and the lack of oxygen can increase the production of harmful free radicals. These free radicals can slow blood circulation and impair physical performance. Preliminary findings in men indicate that taking 400 IU per day of vitamin E, an antioxidant, at high altitude reduces free radical production and maintains aerobic energy production. Increased amounts of many other nutrients should be considered, especially since food intake usually decreases (see Table 12-2).

Tips for Maintaining Performance at Altitudes

♦ Plan on decreased physical performance the first few weeks.

♦ Drink plenty of fluids. Fluid requirements may be as high as 4.25
quarts, or more, each day.

♦ Listen to your body, be aware of any warning signs of illness or
symptoms of AMS and seek medical attention.

♦ Try to avoid substances that cause dehydration (Table 12-1).

As noted throughout this chapter, meeting energy and fluid requirements are vital for maintaining physical performance in adverse environmental conditions. Being physically fit and eating a healthy diet prior to deployment will greatly improve your acclimation and adaptation to the new environment.