We see and hear these nutrition catch phrases all the time, yet we rarely know exactly what they mean. Here are the definitions of a few common terms to guide you along the highway to health.

Daily values: You can find these on the nutrition panel of a food label. They are intended to be a quick reference for the consumer to determine how much of a particular nutrient is included relative to what the U.S. Food and Drug Administration has determined to be the average needs of the "typical" consumer for a single serving size, for example, a daily value of 10 percent for fat means that one serving provides 10 percent of the daily requirement of fat for that day.

So, for example, if the recommended daily intake of sodium is 2,400 milligrams, and a serving of cereal provides 240 milligrams of sodium, the cereal's daily value for sodium would be 10 percent. The daily values of 10 mandatory food components and 22 optional food components appear on food labels.

Essential nutrients: These substances must be obtained from diet because the body either can't make them or can't make adequate amounts of them. "It refers to vitamins and minerals, along with amino acids and certain fats that must be consumed in the diet to support normal metabolism and maintain health. These nutrients are 'essential' because unless they are regularly provided from foods, the body is vulnerable to deficiency," says Dr. David L. Katz, professor of public health at Yale University School of Medicine and author of "The Flavor Point Diet" (Rodale, 2005).

If you've heard this term before, it was probably in regard to omega-3 fatty acids, compounds found in certain fish and nuts that provide necessary nutrients. There is some ambiguity about the best way to introduce these essential nutrients into the body. Nutrients work synergistically, so it is still unclear whether taking supplements is as effective as consuming essential nutrients through a diet of naturally nutrient-rich foods.

Essential minerals: Minerals are inorganic substances meaning they have been mined and do not come from any plant or animal. There are 92 naturally occurring elements, of which 15 or so have proved to be essential to human health, including calcium, chlorine, copper, fluorine, iodine, iron, magnesium, phosphorus, potassium, selenium, sodium and zinc. They help in the production and maintenance of bones, teeth, hair, blood, nerves, skin, enzymes and hormones. They are critical for the healthy functioning of the nervous system, blood circulation and energy production. The body doesn't produce these minerals, but they are found in foods such as fruits, vegetables, meats, nuts, beans and dairy products.

Bioavailability: The bioavailability of a nutrient in a certain food is the amount that our bodies are capable of absorbing. In other words, it's how much of a nutrient you actually receive. "Nutrients can be bound by proteins or can interfere with each other, so the level ingested and the level available can be quite different," says Katz. For example, if you take a calcium supplement such as calcium carbonate, you will only absorb 40 percent, says Fran Grossman, a nutritionist at Mount Sinai Medical Center in New York City. Often the amount available is much less than the amount of nutrient in the food itself, which means learning about the bioavailability of foods in your diet is necessary for determining how much of the vitamins and minerals you eat are actually taken in by your body.

Consider the calcium in a half-cup of cooked spinach (120 mg) and a half-cup of milk (150 mg). It seems eating spinach should provide just slightly less calcium than milk. But it doesn't come close. Our bodies absorb 32 percent of the calcium in milk, but only 5 percent of the calcium in spinach. Bioavailability also varies by individual. For instance, someone who is iron-deficient will absorb more iron than someone who has adequate iron stores.

Metabolic Syndrome (aka Syndrome X): This syndrome describes a combination of increased risk factors for heart disease, stroke and type 2 diabetes, including abdominal obesity, blood-fat disorders that cause plaque buildup in the artery walls, high blood pressure and insulin resistance, which refers to the body's inability to properly process sugar.

At least three of the following measurements must be present for a diagnosis of metabolic syndrome: