Requirements for health
To survive, you need water and food. You must also have and apply high personal hygiene standards.
Your body loses water through normal body processes (sweating, urinating, and defecating). During average daily exertion when the atmospheric temperature is 20 degrees Celsius (C) (68 degrees Fahrenheit [F]), the average adult loses and therefore requires 2 to 3 liters of water daily. Other factors, such as heat exposure, cold exposure, intense activity, high altitude, burns, or illness, can cause your body to lose more water. You must replace this water.
Dehydration results from inadequate replacement of lost body fluids. It decreases your efficiency and, if you are injured, it increases your susceptibility to severe shock. Consider the following results of body fluid loss:
- A 5-percent loss results in thirst, irritability, nausea, and weakness.
- A 10-percent loss results in dizziness, headache, inability to walk, and a tingling sensation in the limbs.
- A 15-percent loss results in dim vision, painful urination, swollen tongue, deafness, and a numb feeling in the skin.
- A loss greater than 15 percent may result in death.
The most common signs and symptoms of dehydration are—
- Dark urine with a very strong odor.
- Low urine output.
- Dark, sunken eyes.
- Emotional instability.
- Loss of skin elasticity.
- Delayed capillary refill in fingernail beds.
- Trench line down center of tongue.
- Thirst. (Last on the list because you are already 2-percent dehydrated by the time you crave fluids.)
You should replace the water as you lose it. Trying to make up a deficit is difficult in a survival situation, and thirst is not a sign of how much water you need.
Most people cannot comfortably drink more than 1 liter of water at a time. So, even when not thirsty, drink small amounts of water at regular intervals each hour to prevent dehydration.
If you are under physical and mental stress or subject to severe conditions, increase your water intake. Drink enough liquids to maintain a urine output of at least 0.5 liters every 24 hours.
In any situation where food intake is low, drink 6 to 8 liters of water per day. In an extreme climate, especially an arid one, the average person can lose 2.5 to 3.5 liters of water per hour. In this type of climate, you should drink 8 to 12 ounces of water every 30 minutes. It is better to regulate water loss through work or rest cycles because overhydration can occur if water intake exceed 1 1/2 quarts per hour. Overhydration can cause low serum sodium levels resulting in cerebral and pulmonary edema, which can lead to death.
With the loss of water there is also a loss of electrolytes (body salts). The average diet can usually keep up with these losses but in an extreme situation or illness, additional sources need to be provided. You should maintain an intake of carbohydrates and other necessary electrolytes.
Of all the physical problems encountered in a survival situation, the loss of water is the most preventable. The following are basic guidelines for the prevention of dehydration:
- Always drink water when eating. Water is used and consumed as a part of the digestion process and can lead to dehydration.
- Acclimatize. The body performs more efficiently in extreme conditions when acclimatized.
- Conserve sweat, not water. Limit sweat-producing activities but drink water.
- Ration water. Until you find a suitable source, ration your sweat, not your water. Limit activity and heat gain or loss.
You can estimate fluid loss by several means. A field dressing holds about 0.25 liters (1/4 canteen) of fluid. A soaked T-shirt holds 0.5 to 0.75 liters.
You can also use the pulse and breathing rate to estimate fluid loss. Use the following as a guide:
- With a 0.75-liter loss the wrist pulse rate will be under 100 beats per minute and the breathing rate 12 to 20 breaths per minute.
- With a 0.75- to 1.5-liter loss the pulse rate will be 100 to 120 beats per minute and 20 to 30 breaths per minute.
- With a 1.5- to 2-liter loss the pulse rate will be 120 to 140 beats per minute and 30 to 40 breaths per minute. Vital signs above these rates require more advanced care.
Although you can live several weeks without food, you need an adequate amount to stay healthy. Without food your mental and physical capabilities will deteriorate rapidly and you will become weak. Food provides energy and replenishes the substances that your body burns. Food provides vitamins, minerals, salts, and other elements essential to good health. Possibly more important, it helps morale.
The three basic sources of food are plants, animals (including fish), and issued rations. In varying degrees, both provide the calories, carbohydrates, fats, and proteins needed for normal daily body functions. You should use rations to augment plant and animal foods, which will extend and help maintain a balanced diet.
Calories are a measure of heat and potential energy. The average person needs 2,000 calories per day to function at a minimum level. An adequate amount of carbohydrates, fats, and proteins without an adequate caloric intake will lead to starvation and cannibalism of the body’s own tissue for energy.
Plant foods provide carbohydrates—the main source of energy. Many plants provide enough protein to keep the body at normal efficiency. Although plants may not provide a balanced diet, they will sustain you even in the arctic, where meat’s heat-producing qualities are normally essential. Many plant foods such as nuts and seeds will give you enough protein and oils for normal efficiency. Roots, green vegetables, and plant foods containing natural sugar will provide calories and carbohydrates that give the body natural energy.
The food value of plants becomes more and more important if you are eluding the enemy or if you are in an area where wildlife is scarce. For instance—
- You can dry plants by wind, air, sun, or fire. This retards spoilage so that you can store or carry the plant food with you to use when needed.
- You can obtain plants more easily and more quietly than meat. This is extremely important when the enemy is near.
Meat is more nourishing than plant food. In fact, it may even be more readily available in some places. However, to get meat, you need to know the habits of and how to capture the various wildlife.
To satisfy your immediate food needs, first seek the more abundant and more easily obtained wildlife, such as insects, crustaceans, mollusks, fish, and reptiles. These can satisfy your immediate hunger while you are preparing traps and snares for larger game.