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comes almost all at the expense of cultivated and percentage of protein in the given food that the body can absorb. Biologi-
grazing land. Better urban planning could save cal value represents the percentage of the absorbed protein that the body
much of this land. Further expansion of land for can actually put to work building cells for growth and maintenance. If
cultivation in some countries is being carried out we multiply digestibility and biological value, we get a measuring index
but this may be at the expense of the environ- known by nutritionists as net Protein Utilization (nPU), which stands for
ment. Countries such as India, China or the U.S. the total percentage of the protein that the body can actually use. Without
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are unlikely to convert land back to cultivation, exception, animal proteins have a higher nPU than vegetable proteins. See
so planning now may be the key to prevent this Figure 17.
land from being turned into cities and removed net protein utilization tells us, among other things, that when we
from its potential in creating edible products. include animal protein in our diet, we can satisfy our daily protein require-
ments with smaller amounts of food than if we rely on vegetable products
USaBIlIty oF the ProteIn We eat alone. remember that even if you got your nPU from dried peas or navy
nearly equal in importance to the complete- beans, you would still be getting an incomplete, low-quality protein, defi-
ness or quality of the protein we eat is how ef- cient in the essential amino acids the body needs. In terms of quality and
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ficiently and completely the body can use it. Not accessibility to the body, the animal protein in meat, milk and especially
only do we need all the eight (nine for children) eggs goes further in meeting our needs than protein from plants.
essential amino acids in our diet, we also need
them in our body in just the right proportions and BalanCe oF ProteIn anD CalorIeS
at the same time. It does little good taking in a Proteins need to be consumed in the right proportion to fats. Stud-
few essential amino acids one day and getting the ies with chickens tell us more about proteins, fat and cholesterol. In one
others later in the week. the body simply cannot study, we varied the fat-to-protein ratio in the diet. When the amount of
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make effective use of them unless it has them all protein in the diet was increased compared to the amount of fat in the diet,
together at one time. Missing one of the essential the cholesterol level in the chicken’s blood dropped, and they had less fat
amino acids is almost like trying to read a novel on their bodies. the type of fat consumed made no difference. a “hard”
in which every ninth page is missing, except that fat such as beef tallow gave results similar to a “soft” fat such as corn
our imaginations can fill in the plot line whereas oil. 22,23 translating this to people means that if you’re going to eat lots of
our bodies cannot fill in the missing amino acid. fat of any kind, make sure you eat enough protein to lessen the increase
Moreover, even if all the essential amino acids in cholesterol and weight gain.
are present, too little of one can limit the body’s one way of monitoring the level of protein-to-fat is through the e/P
effective use of the others. ratio (energy/protein) of a food item or diet. energy here is measured in
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the usability of various protein foods can calories, which are really units representing the energy-producing poten-
be expressed in terms of digestibility and bio- tial of a food. the e/P ratio is calculated by dividing the total calories in
logical value. Digestibility simply refers to the the food item or diet by its protein content. For example, white bread has
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FIGURE 17: The Biological Value: The Net Protein FIGURE 18: Comparison of Energy-Protein Ratio of Various Foods. 21
Utilization of Food. 4
FOOD NPU Amount needed daily if FOOD E/P Ratio FOOD E/P Ratio
a single food source Shrimp 5 Cheddar Cheese 16
Cottage Cheese 5 Whole Milk 20
Eggs 94% 6 1/2 eggs Halibut 6 High Protein Bread 21
Milk 86% 5 1/2 cups Lean Beef 10 Oatmeal 28
Cheese, Swiss Skim Milk 10 White Bread 32
or Cheddar 82% 5 ounces Whole Eggs 12 Candy Bar (with nuts) 54
Beefsteak 75% 6.6 ounces Broccoli 13 Doughnuts 65
Soybeans 66% 2 cups Wheat Germ 15 Cookies 73
Peanuts 56% 2 cups Fresh Peas 15 Pie Crust 92
Whole wheat 53% 36 slices whole
wheat bread Energy Protein ratio = total calories in 100 g/percent protein
Dried beans
and peas 34% 7.2 cups beans
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