The Complete Guide to Recommended Daily Nutritional Requirements and Dietary Assessment.

Daily Nutritional Requirements

Nutrients are substances that are not synthesized in sufficient amounts
in the body and therefore must be supplied by the diet.Nutritional
requirements for groups of healthy persons have been determined
experimentally.

The absence of essential nutrients leads to growth
impairment, organ dysfunction, and failure to maintain nitrogen bal-
ance or adequate status of protein and other nutrients. For good health,
we require energy-providing nutrients (protein, fat, and carbohydrate),
vitamins, minerals, and water.

Requirements for organic nutrients
include 9 essential amino acids, several fatty acids, glucose, 4 fat-
soluble vitamins, 10 water-soluble vitamins, dietary fiber, and choline.
Several inorganic substances, including 4 minerals, 7 trace minerals, 3
electrolytes, and the ultratrace elements, must also be supplied by diet.

ESSENTIAL NUTRIENT REQUIREMENTS
Energy For weight to remain stable, energy intake must match
energy output.

The major components of energy output are resting
energy expenditure (REE) and physical activity; minor components
include the energy cost of metabolizing food (thermic effect of food,
or specific dynamic action) and shivering thermogenesis (e.g., cold-
induced thermogenesis).

The average energy intake is ~2600 kcal/d
for American men and ~1800 kcal/d for American women, although
these estimates vary with body size and activity level.

Protein Dietary protein consists of both essential and nonessential
amino acids that are required for protein synthesis.

The nine essential
amino acids are histidine, isoleucine, leucine, lysine, methionine/
cystine, phenylalanine/tyrosine, threonine, tryptophan, and valine.
Certain amino acids, such as alanine, can also be used for energy and
gluconeogenesis. When energy intake is inadequate, protein intake
must be increased, because ingested amino acids are diverted into
pathways of glucose synthesis and oxidation..

Fat and Carbohydrate Fats are a concentrated source of energy
and constitute, on average, 34% of calories in U.S. diets. However, for
optimal health, fat intake should total no more than 30% of calories.
Saturated fat and trans fat should be limited to <10% of calories and
polyunsaturated fats to <10% of calories, with monounsaturated fats
accounting for the remainder of fat intake.

At least 45–55% of total
calories should be derived from carbohydrates. The brain requires
~100 g of glucose per day for fuel; other tissues use about 50 g/d..

Fat and Carbohydrate Fats are a concentrated source of energy
and constitute, on average, 34% of calories in U.S. diets.

However, for
optimal health, fat intake should total no more than 30% of calories.
Saturated fat and trans fat should be limited to <10% of calories and
polyunsaturated fats to <10% of calories, with monounsaturated fats
accounting for the remainder of fat intake.

At least 45–55% of total
calories should be derived from carbohydrates. The brain requires
~100 g of glucose per day for fuel; other tissues use about 50 g/d. Some
tissues…

Water For adults, 1–1.5 mL of water per kilocalorie of energy expen-
diture is sufficient under usual
conditions to allow for normal varia-
tions in physical activity, sweating, and solute load of the diet. Water
losses include 50–100 mL/d in the feces;

500–1000 mL/d by evapo-
ration or exhalation; and, depending on the renal solute load, ≥1000
mL/d in the urine. If external losses increase, intakes must increase
accordingly to avoid underhydration. Fever increases water losses by
~200 mL/d per °C; diarrheal losses vary but may be as great as 5 L/d
in severe diarrhea.

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