Throughout this book you’ll find many nutritional and health terms. Most nutrients are included in the glossary, but these frequently repeated terms are also defined here, for easy reference.

AMINO ACIDS

Amino acids are chemical compounds found in plant and animal proteins. There are 20 different types of amino acids. About half of these the body synthesizes (or creates); they are called nonessential amino acids. The rest—called essential amino acids—must be acquired through diet. The body uses both nonessential and essential amino acids to make new proteins in the body. Proteins are an integral element in repair and growth of body tissue, immune protection, and the transmission of nerve impulses.

ANTIOXIDANTS

Antioxidants help protect the body against free radicals, which are unstable molecules that can damage cells and cause cancer. Many antioxidants are found in food while others are synthesized in the body. Some antioxidants come in the form of vitamins, such as vitamins A, C, and E, while others are phytonutrients, such as lycopene, beta-carotene, lutein, and selenium. Whole foods, such as fruits, vegetables, nuts, and grains, are among the best sources of antioxidants.

CARBOHYDRATES

Along with protein and fats, carbohydrates are one of the main dietary components the body needs in order to function. Carbohydrates come primarily in the form of sugars, starches, and fiber (the latter can’t be digested). Once carbohydrates are consumed, the digestive system converts the sugars and starches into sugar molecules, which enter the bloodstream and provide energy for cells and tissue. Whole, minimally processed foods, such as vegetables, fruits, whole grains, and low-fat dairy, are the best kinds of carbohydrates; the fiber in these foods helps slow sugar absorption, resulting in an even, sustained level of energy. Heavily processed foods—including sugary cereals, white flour, and potato chips—contain little fiber and their starches and sugars rapidly turn into glucose in the body, spiking blood sugar, which can cause energy levels to quickly plummet. Excess glucose—what the body doesn’t need for immediate energy, or for future reserves in the form of glycogen (stored in the liver and muscles)—turns to fat.

CAROTENOIDS

These fat-soluble plant pigments, ranging in color from yellow to orange to red, typically function as antioxidants; the body can even convert a few into vitamin A. The best-known carotenoid is carotene, from which the group gets its name.

CHOLESTEROL

A waxy fat compound, cholesterol is important for making some hormones and forming cell membranes. Cholesterol is found both in animal foods and in the body, which the liver manufactures from fatty foods. Cholesterol is transported through the body by molecules called lipoproteins: low-density lipoprotein (LDL) is known as “bad” cholesterol because it builds up on arterial walls and can lead to atherosclerosis; high-density lipoprotein (HDL) is considered “good” cholesterol because it helps move excess cholesterol from the arteries to the liver for disposal and may protect against heart disease.

FATS

Along with carbohydrates and protein, fats are one of the body’s most basic nutrients. Just as amino acids make up protein molecules, so do fatty acids comprise fat molecules. Fats come in two forms: saturated and unsaturated.

SATURATED FATS Saturated fats are primarily found in animal products. In the diet, saturated fats tend to increase the body’s production of LDL (“bad”) cholesterol and reduce the production of HDL (“good”) cholesterol. They have a higher melting point than similar unsaturated fats, and foods containing saturated fats (like butter) are often solid at room temperature.

UNSATURATED FATS Unsaturated fats are mostly found in plant products, and they tend to lower the body’s production of LDL (“bad”) cholesterol. There are two main types of unsaturated fats:

MONOUNSATURATED FATS Found in olive oil and nuts, monounsaturated fats tend to increase the body’s production of HDL (“good”) cholesterol and reduce the production of LDL (“bad”) cholesterol.

POLYUNSATURATED FATS Polyunsaturated fats tend to reduce the body’s production of cholesterol—both HDL (“good”) cholesterol and LDL (“bad”) cholesterol. Both omega-3 and omega-6 are polyunsaturated fats with myriad health benefits. Omega-3 fatty acids are found in walnuts, flaxseed, and many types of cold-water fish; they are crucial to brain and heart health, and may reduce inflammation and lower risk of some chronic diseases. Omega-6 fatty acids, which are also important to brain development, are plentiful in many types of vegetable oil, such as corn, soybean, and safflower. Unfortunately, many Americans get too many omega-6 fatty acids in their diets, which may promote inflammation.

FIBER (SOLUBLE AND INSOLUBLE)

The indigestible portion of plant foods, fiber passes through the body without being absorbed. There are two main types: insoluble fiber, which does not dissolve in water and helps prevent constipation; and soluble fiber, which forms a gel in water, lowers cholesterol, and slows the body’s absorption of sugar. Fruits, vegetables, whole grains, and legumes contain both types. Adequate consumption of fiber is associated with a lower risk of heart disease and type 2 diabetes.

FLAVONOIDS

A large group of plant-produced compounds (primarily pigments in the yellow and blue to red range), flavonoids may promote antioxidant production and other beneficial responses in the body.

MINERALS

Whereas vitamins are organic (containing carbon) and are produced by plants and animals, minerals are derived from inorganic substances found in the earth and water. Plants absorb these minerals, and the plants are, in turn, eaten by animals. The body needs minerals each day for proper cell growth and overall health. It requires some minerals, such as calcium, in large quantities. Trace minerals, such as chromium, iron, selenium, and zinc, are needed only in small quantities each day.

PHYTONUTRIENTS

Phytonutrients, also called phytochemicals, include a wide range of plant compounds (phyto means “plant”) that promote health. Some groups of phytonutrients currently under research include carotenoids, phytosterols, and limonoids.

PROTEIN

Along with fats and carbohydrates, protein is a main component for fueling the body. Protein compounds are made up of chains of amino acids. “Complete” dietary proteins, such as quinoa, meat, and cheese, contain all the essential amino acids, while “incomplete” proteins, such as grains, legumes, vegetables, and fruits, contain only some of them. The body breaks down the food’s protein into its amino acids and uses them as the building materials for all its cells, as well as for energy.

VITAMINS

Organic compounds made by plants or animals, vitamins are essential for normal growth and they promote a healthy metabolism. There are two varieties of vitamins: fat soluble and water soluble. Fat-soluble vitamins, including A, D, E, and K, are absorbed in fat and can be stored in the body’s fatty tissue—for this reason, the body doesn’t need a daily supply. Water-soluble vitamins, such as C and the B-complex vitamins, can’t be stored: Any excess is carried out of the body, so a fresh supply is needed every day.