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Chapter 3 Nutrition 73
No single plant source contains all of the essential amino ac-
ids. You must eat multiple types of protein-rich plants to obtain
all of the amino acids. For this reason, vegetarians must ensure
they are including complementary proteins in their diet. Comple-
mentary proteins are two or more incomplete protein sources that
together provide adequate amounts of all the essential amino
acids.
For example, rice contains low amounts of certain essential
amino acids; however, these same essential amino acids are found
in greater amounts in dry beans. Similarly, dry beans contain
lower amounts of other essential amino acids that are found in
larger amounts in rice. Together, rice and beans provide adequate
amounts of all the essential amino acids (Figure 3.4).
In the past, it was thought that complementary proteins
needed to be eaten at the same meal for the body to use them
together. Now studies show that the body can combine com-
plementary proteins that are eaten at different times during the
day, as long as they are eaten within the same day.
Fats
Fats are a type of nutrient that is largely made up of fatty acids, which
provide a valuable source of energy. Fatty acids are a particularly impor-
tant source of energy for muscles. Common fats in the diet include satu-
rated fats, unsaturated fats, trans fats, and cholesterol.
Saturated Fats
Saturated fats are found primarily in animal-based foods, such as meat
and dairy products. These are called saturated fats because the carbon at-
oms in these fats have all the hydrogen atoms they can hold. Saturated fats
are typically solid at room temperature.
Unsaturated Fats
Unsaturated fats are found in plant-based foods such as vegetable
oils, some peanut butters and margarines, olives, salad dressing, nuts, and
seeds (Figure 3.5 on the next page). As you might guess, unsaturated fats
do not have all the hydrogen atoms they could hold. They have at least one
double bond to which an additional hydrogen atom can be added. Unsatu-
rated fats are liquid at room temperature.
Trans Fats
Trans fats are created by a process known as hydrogenation, which bom-
bards an unsaturated fat with hydrogen atoms and changes double bonds to
single bonds. This makes the fat more saturated and, therefore, more solid. This
Eating enough of the right
complementary proteins can
provide your body with all
nine essential amino acids in
a day. What are some meals
you eat that might combine
complementary proteins?
Figure 3.4
fat
a type of nutrient, composed
of fatty acids, that is a
valuable source of energy,
especially for muscles
saturated fat
a type of fat found primarily
in animal-based foods that is
solid at room temperature
unsaturated fat
a type of fat that is liquid
at room temperature and is
found in plant-based foods
trans fat
a type of fat that is created
by hydrogenation; poses
health risks acknowledged
by the FDA