Water
A big concern on long backpacking treks is the water supply. The average human in basically sedentary conditions requires at least half a gallon of water a day. A trekker should count on needing as much as twice that amount. A gallon of water weights 8 1/3 pounds, making carrying any sizable amount of water plus food and equipment impossible. A trekker must count on being able to draw water from local sources, and very often that means relying on questionable sources. The best way to handle that is to purify your water in two stages. The first is to kill the microorganisms by either boiling the water or using iodine tablets. The second is to carbon filter the water, a consideration if there is any question of pollutants in the water. There are many specialized filters for campers, but the cheapest way to do this is to use an ordinary Brita pitcher filter. Pack the empty pitcher with stores while it is being carried in the backpack, and it will occupy almost no space at all.
Bring Some Kool-Aid or Tang
Tang, the trekker's friend
Many trekkers do not want to be bothered with having to boil water every time they need to refill their canteens, nor do they want to have to carry around 1 to 2 gallons of water through the day. These are understandable concerns, which is why many cross-country trekkers use iodine tablets. However, there is a problem with iodine: It tastes terrible. A good way to eliminate that problem, get some quick sugar and vary the flavors of the trail diet a bit is to bring along fruit-flavored drink packs. They don't weigh very much, and go a long way toward taking that nasty iodine taste out of the water supply.
Lightweight Foods
The same reasons trekkers cannot carry around several gallons of potable water limit their food choices. Backpacker food must be of the sort that won't rot, but also won't weigh much. The main concern is the calorie-to-weight ratio. This rules out most canned goods automatically, as the can weighs too much and the contents are rarely calorie rich enough to justify it. The best contenders among the preserved foods in the calorie-to-weight ratio category are nuts, dried fruits and beef jerky. The former two are why "trail mix" has its name. After all, trail mix is based on nuts and dried fruits, and on the trail, a backpacker can't do much better for packing lots of calories into a small package.
Freeze-Dried Packets and MREs
Chili MRE
The problem with beef jerky and trail mix is that its not a very appetizing diet for more than a day. The way to add some variety is to use prepackaged freeze-dried meals. These are available from most backpacking retailers. Another good source for variety foods is the U.S. military's MRE ration system, each of which contains a complete meal of between 1,200 and 1,300 calories per lightweight package.
