All you have to do is turn on the TV or radio or open up a newspaper or magazine, and you'll run smack into terms such as "macronutrients" and "enriched foods." Familiar words, but do you really know what they mean? Here are just a few of the many nutrition definitions worth knowing.

Functional foods: "A nutrient or a food that may provide additional health benefits beyond basic nutrition. For example, yogurt with added bacteria," explains Fran Grossman, a nutritionist at New York City's Mount Sinai Medical Center.

"Nearly all whole foods are 'functional' in some way. A functional food is not necessarily a healthy one, so make sure to read the fine print," advises Amy Joy Lanou, an assistant professor at University of North Carolina-Asheville. "For example, the egg industry describes eggs as a functional food, yet whole eggs are very high in cholesterol and should be limited in a healthy diet."

High-fructose corn syrup (HFCS): HFCS is regular corn syrup that has been treated with an enzyme that converts glucose into fructose (which is sweeter). "The final product is a combination of glucose and fructose, usually either 42 percent fructose or 55 percent fructose, with the rest mostly glucose," says Joanne R. Lupton, a professor of nutrition at Texas A&M University. The 55 percent HFCS is often used to sweeten soft drinks, and the 42 percent HFCS is used in baked goods.

Some experts believe that the higher proportion of fructose to glucose creates harm. "It's easier for fructose to be made into fat than for glucose to be made into fat. Additionally, there is a relatively strong literature showing negative consequences of fructose compared to glucose with respect to raising fatty substances in the blood," Lupton says.

It has also been suggested that the rise in obesity in the United States is related to the rise in HFCS consumption. "However, most evidence suggests that the metabolic effects of sucrose and HFCS are pretty similar. What makes HFCS such a hazard is that corn growth is highly subsidized in the U.S., so HFCS is very inexpensive — and thus a tempting additive to many foods," says David L. Katz, associate professor of public health at Yale University School of Medicine and author of "The Flavor Point Diet" (Rodale, 2006).

Therefore, it has been argued that adding HFCS leads to an increased consumption of foods that are less nutrient dense, leading to greater calorie consumption and eventually weight gain.

Nutrient density: "Nutrient-dense foods provide high amounts of nutrients at a low calorie cost," Lupton says. For a food to be considered nutrient dense, it must provide substantial amounts of vitamins and minerals and relatively fewer calories. Some foods are almost always nutrient dense: whole grains and whole-grain products, fruits, vegetables and legumes.

The opposite of nutrient dense is calorie dense — foods that mainly supply calories with relatively few nutrients. These are often referred to as "empty calories" — calories that provide few or no health benefits, adds Katz.

For instance, a quarter-cup of sunflower seeds has about 200 calories while a can of Sprite has only 140 calories. However the sunflower seeds provide 20 percent of the daily value for folate and vitamin B5 and more than 25 percent for phosphorous, tryptophan, copper, magnesium and manganese. Meanwhile, the 200 calories are only about 11 percent of daily calorie needs. So you're getting twice as many nutrients as calories.

Macronutrients: These are the nutrients we need to consume in relatively large amounts to stay healthy. They also provide the energy we need to survive. They include carbs, fat and protein, the three nutrients that constitute the majority of our diet.

Macronutrients also supply calories, whereas micronutrients do not. The general recommendation for adults (which varies according to weight) is 45 percent to 65 percent of total daily calories from carbs, 20 percent to 35 percent from fat and 10 percent to 35 percent from protein.

Micronutrients: These are the nutrients in foods that are in quantities too small to see. "They include vitamins, which are organic compounds our bodies need to function normally, and minerals, which are inorganic compounds our bodies need to function normally," Katz says.

Fortified foods: Fortification is the process by which nutrients and minerals are added to a food that never had them to begin with. One of the most popular examples is milk fortified with vitamin D. In addition to providing milk drinkers with an extra vitamin, the added ingredient increases the rate at which the body absorbs the calcium naturally found in milk.

Enriched foods: "The generally accepted definition is a food in which nutrients that were lost in processing have been replaced," Lupton says. For instance, when certain foods are refined, they lose many of the nutrients they had in their original form. Once the food has been processed, manufacturers reintroduce (usually at higher levels) the vitamins and minerals that have been leached.

Charles Stuart Platkin is a syndicated health, nutrition and fitness writer.

Reach Charles Stuart Platkin at info@thedietdetective.com.