When temperatures are very low, water in canteens and bulk water containers may freeze, restricting water availability. All melted snow and ice, as well as water from streams, should be considered contaminated. This amounts to an additional minute for every 1000-foot gain in altitude. For example, at 14,000 feet, water needs to be boiled for 24 minutes to be purified. Gastrointestinal Complaints 1.
Constipation is a common complaint during any field exercise.
It is especially prevalent at altitude where decreased oxygen slows down the function of the intestines and excessive fluid losses rob water from the colon. Emphasis on adequate fluid intake is the best preventative. Many soldiers complain of intestinal gas at high altitudes. Responses to particular foods are highly individual and, therefore, difficult to predict. Dehydrated foods high in carbohydrate tend to cause gas production and should be tried in small quantities until tolerance is established.