PROTEIN
Protein is a necessary component for building, maintenance, and repair of many body
systems and processes, including:
•Production of collagen and keratin, which are the structural components of bones, teeth,
hair, and the outer layer of skin; they help maintain the structure of blood vessels
•Manufacture of hormones, such as insulin and thyroid hormone
•Production of enzymes that control chemical reactions in the body
•Proper immune function—production of antibodies, white blood cells, and other
immune factors
•Transportation of oxygen, vitamins, and minerals to target cells throughout the body
MACRONUTRIENTS8 | Chapter 1
•Source of energy—the liver can use protein to make glucose when there is not enough
carbohydrate available, such as when you skip a meal or follow a low-carb diet.
Food Sources
Protein is found in animal products, nuts, legumes, and, to a lesser extent, in fruits
and vegetables. When we eat protein the body breaks it down into amino acids, some
of which are called essential because they must be provided by the food we eat.
Others that can be produced by the body are called non-essential.
Protein from animal sources contains all of the essential amino acids. Therefore,
your best sources of lean protein are chicken, turkey, fi sh, and eggs. Choose free-
range and organic wherever possible to reduce ingesting harmful hormones and
chemicals.
Plant proteins do not contain all the essential amino acids and are considered
incomplete proteins. It is possible, though, to combine various plant proteins to get all
the essential amino acids. For example, eating oats, lentils, and sunfl ower seeds either
together or separately throughout the day provides all the essential amino acids. You
could also combine whole-wheat pasta with white kidney beans or tofu with brown
rice to get all the necessary amino acids. It just requires careful meal planning.
There are certain advantages of eating plant over animal proteins—they pro-
vide fi bre and phytochemicals (antioxidants), do not contain saturated fat, and
may play a role in disease prevention. Soy protein, for example, has been shown to
signifi cantly lower cholesterol and triglyceride levels, and protect against bone loss.
A number of studies have found lower risk of chronic disease in those who eat a
plant-based diet.
The Institute of Medicine recommends ranges for macronutrient intake that are
associated with a reduced risk of chronic disease while providing adequate intake
of essential nutrients. They suggest that adults get 45–65 percent of calories from
carbohydrates, 20–35 percent from fat, and 10–35 percent from protein. Ranges for
children are similar, except that infants and younger children need a slightly higher
proportion of fat (25–40 percent).
Tags: animal proteins, animal sources, careful meal, diet food, essential amino acids, fruits and vegetables, immune factors, incomplete proteins, lean protein, low carb diet, manufacture of hormones, outer layer of skin, plant proteins, proper immune function, thyroid hormone production, vitamins and minerals, white blood cells, white kidney beans, whole wheat pasta
