Sumo wrestlers consume between 6000-20,000 calories per day.  Imagine planning and purchasing food storage for that group.  

The human diet must provide enough calories to meet daily energy needs, together with carbohydrates, essential amino acids, essential fats, minerals and vitamins for proper metabolism. During short term emergencies you should be focused on food as a fuel.  Don't worry about nutrition.  For emergencies longer than 3 weeks, complete nutrition plays a more important role.

Calories

Calories are the measurement of energy stored in foods.  The human body uses food as its fuel.  Active adult females consume 2400 calories per day, while inactive females will consume approximately 1800 calories per day.  Active males can consume as many as 3000 calories per day and 2400 if inactive.  Older adults and teenagers will consume 200-300 fewer calories than younger adults. Most average this requirement to be 2000 calories per person, per day at a minimum.   In the absence of food, the body uses its reserve fuel (glycogen).  Glycogen is stored as fat in the body.  When fat reserves are low or gone, the body will begin to destroy and consume its own protein (muscle).

Carbohydrates

Carbohydrates are carbon containing compounds such as sugars and simple starches.  These are termed simple carbohydrates.  More complex forms exist and are part of the structure of grains, beans, and vegetables.  Humans can consume these carbohydrates and use them as fuel and as building blocks for substrates the body needs.

Essential amino acids

Amino acids are the building blocks of protein.  When plant or animal protein is consumed, it is broken down into its amino acids.  These can then be used in human metabolism.  An absence of one or more essential amino acids over a period of weeks to months can lead to malnourishment symptoms of apathy, diarrhea, inactivity, failure to grow, flaky skin, fatty liver, and edema of the belly and legs.  Excess amino acids can also be used as fuel for the body (calories).

Essential fats

Three key fatty acids are needed in the diet: linoleic acid, linolenic acid, and arachidonic acid. These are found in grain, vegetable or nut oils.

Minerals

Only small levels of minerals are needed for proper nutrition. These minerals are scavenged from many sources and it is rare for anyone consuming a regular diet to have a deficiency.  In the overall scheme of nutrition, minerals should be the least worry.

Vitamins

Vitamins serve as metabolic assistants in many vital bodily functions.  Vitamins A, B_(1,2,3,12), C, D, E, K, and folic acid are required.  Deficiencies lead to specific diseases such as beriberi and rickets.  During short term emergencies it is not necessary to worry about vitamin content of foods.  It usually takes several weeks to months of deficiency before any symptoms appear.  After an emergency, vitamin deficiency symptoms can rapidly disappear after consuming nutritious foods or supplements.

Effect of storing foods on nutritional content

Foods are complex mixtures of chemicals.  During storage over time, these chemicals can break down or change.  For the most part, the body can still use carbohydrates, amino acids, fats, and minerals that have been chemically changed during storage.  This means food storage, no matter how old, no matter how bad they taste, will still provide fuel (calories) and nutrition.  Vitamins are the only nutrient group that can break down to an unusable state. Therefore, during 3 week or longer emergencies, vitamin deficiency is increasingly important.

Vitamin deterioration

 [i]^,[ii] Oxygen, moisture, high temperature, prolonged cooking and storage time, pH, and light can affect the nutritional content of foods. Control of these factors helps to retain vitamin content of foods. Storage and cooking can be the cause for the loss of up to half of nutrients in food.  

• Vitamin C.[iii]  (Ascorbic acid) Of all the vitamins, vitamin C is the most unstable.  Almost immediately after harvest vitamin C decreases rapidly in foods.  It also decreases during storage, drying, and heating. 
• Vitamin B₁.^ii,iii  (Thiamine)  Vitamin B₁ is damaged by high temperatures and in neutral and alkaline conditions, such as baking soda and baking powder.  Vitamin B₁ also leaches out into cooking water.
• Vitamin B₂.ⁱⁱⁱ (Riboflavin) Vitamin B₂ is sensitive to light at neutral and alkaline conditions (baking soda and baking powder). It is somewhat heat stable when in neutral conditions and sensitive to heat when under alkaline conditions.
• Vitamin B₃.ⁱⁱⁱ (Niacin) Vitamin B₃ is one of the most stable vitamins, but it also leaches into cooking water.
• Folate.ⁱⁱⁱ Folate levels decrease with prolonged storage and heat and is lost in cooking water.
• Vitamin B₆.ⁱⁱⁱ  Vitamin B₆ is heat stable in alkaline as well as acidic conditions.
• Vitamin B₁₂.ⁱⁱⁱ  Vitamin B₁₂ is destroyed by light and high pH levels.
• Vitamin A.ⁱⁱⁱ  Vitamin A is easily destroyed by heat and is oxidized easily.
• Vitamin D.ⁱⁱⁱ  Vitamin D is easily oxidized by heat and light.
• Vitamin E.ⁱⁱⁱ Vitamin E is also easily oxidized.                 

Summary

Nutrient loss during food storage is limited only to vitamins.  All remaining nutrition will remain including carbohydrates, essential amino acids, essential fats, and minerals.  Older stored foods should not be discarded for fear of nutrition loss. Instead, keep these items until they are replaced.  An old (safe) commercially canned food with all vitamins deteriorated has more nutrition that nothing at all.  To compensate for vitamin loss during long term emergencies consider storing multi-vitamins or some sort of fresh food will be required to meet vitamin needs.  One may sprout wheat looking for vitamins.  But, sad-to-say, wheat grass tastes and is equally nutritious as Kentucky blue, burmuda, or zoysia grass.  Its a personal choice.

References.

[i] Bastin, S. (last edited date). Vegetable Preparation for the Family. University of Kentucky Cooperative Extension Service. Retrieved September 2, 2011, from http://www.ca.uky.edu/agc/pubs/fcs3/fcs3106/fcs3106.pdf.

[ii] Park, L.M.A. (1987). Nutrition Retention and Sensory Quality in Low-Moisture Foods Stored 42 to 60 months: Effect of Storage Temperature, Time and Oxygen Level.  Brigham Young University Department of Food Science and Nutrition.

[iii] Morris, A., Barnett, A. Burrows, O. (2004). Effect of Processing on Nutrient Content of Foods. CAJANUS 37 (3): pp.160-164.

[iv] Berrett, D.M., Bruhn, C. M., Rickman, J.C. Nutritional Comparison of fresh, frozen, and canned fruits and vegetables. University of California.

[v] Fraser, A. (2008). Describe the different ways that food spoils. South Carolina: Clemson University. Available at: http://www.foodsafetysite.com/educators/competencies/general/microbiology/mic6.html.

[vi] Baird, B. Shelf-life of Meat. Texas A & M University. Available at: http://meat.tamu.edu/topics/techtopicBridget.pdf

[vii] Sethi, S. (2007). Principles of Food Processing. Horticulture: Post Harvest Technology. Available at: http://www.docstoc.com/docs/21672981/History-of-Food-processing

[viii] University of Minnesota Extension. The Findings: Nutritional Content of Fresh Fruits and Vegetables Compared with Canned. Available at: http://www.pickyourown.org/nutritionalvalueoffresfhversuscannedfoods.php

[ix] NDSU Extension Service. (1989). How Long Are Canned Foods Safe? North Dakota State University. Available at: http://www.ext.nodak.edu/extnews/askext/canning/4577.htm

[x] Davila, R. (1985). Nutrient Retention with BHA After Storage in Food Systems Heat-Processed in Cans and Pouches. A thesis from the Department of Food Science and Nutrition at Brigham Young University. Available at: http://ndfs.byu.edu/Portals/9/docs/research/long/Roberto%20Davila.pdf.

[xi]  Front Range Healthy Lifestyles Issues Team. (2011). Food Safety and Storage for Emergency Preparedness. Colorado State University Extension.

[xii] USDA Fact Sheets. (2010). Freezing and Food Safety. USDA Food Safety and Inspection Service. Available at: http://www.fsis.usda.gov/factsheets/focus_on_freezing/index.asp#5

[xiii] USDA. (2000). Building Blocks for Fun and Healthy Meals. USDA Food and Nutrition Service. Available at: http://www.fns.usda.gov/tn/resources/blocksintro.pdf

[xiv] Family Food Education Program. (2009). Food Storage for Emergencies. Oregon State University Extension Service. Available at: http://extension.oregonstate.edu/gilliam/sites/default/files/food_storage_emergencies_osu.pdf

[xv] Raab, C. (2007). What Counts? Nutrients in Fresh and Preserved Fruits and Vegetables. Oregon State University. Available at:  http://extension.oregonstate.edu/nep/Reports/fruit_veg_summit/what_counts_fact_sheet.pdf