By Cynthia Sass
May 17, 2011
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If you regularly tune into nutrition news you probably hear and see words like antioxidant and glycemic index often, but do you really know what they mean? Here's a crash course in some of today's top nutrition terms:

Free Radicals

I think of free radicals as nasty little bullies. They are generated in our bodies every day and we build up even more when we're under stress or are exposed to pollutants, like smog and cigarette smoke, and even when we exercise. They are basically oxygen molecules that have become unstable, like a chair with 3 legs. In an attempt to stabilize, they attack healthy cells to steal their electrons - this damages the cell and can lead to premature aging and disease. This process is called oxidation or oxidative stress and the oxidation of "bad" LDL cholesterol creates a domino effect that can lead to heart disease and stroke, which is why you hear so much about free radicals in relation to heart health. You can't totally eliminate free radicals, but antioxidants can help fight them.


Antioxidants are like little bodyguards that protect your cells from free radicals. They essentially donate electrons to those nasty bullies to stabilize them and render them harmless. There are dozens of antioxidants, like beta-carotene found in carrots and flavanols in dark chocolate. A common example of antioxidants in action is how lemon juice protects apples – if you slice a fresh apple, the wedges turn brown from oxidation, but tossing the wedges with lemon juice, which contains vitamin C, an antioxidant, fights oxidation and prevents the browning.


A phytochemical is a natural substance in a plant food that is associated with the color, aroma or flavor. They're not vitamins or minerals but they are associated with preventing disease and keeping us looking and feeling well. Most phytochemicals have antioxidant activity, which is why you often hear these words used interchangeably. Examples of phytochemicals we tend to hear a lot about are lycopene in tomatoes and resveratrol in grapes and wine.

Glycemic Index

In a nutshell the glycemic index essentially measures how quickly a food will raise your blood sugar. Foods are assigned a score on the index – the higher the score, the faster your blood sugar will rise and vice versa. High is considered a rating of 70 and above and low is 55 or below. Sugary cereals rank over 100 and beans are about 40. But there's a catch – the index was created using 50 gram portions of single foods. When you eat foods together they do interact, so a low glycemic food can blunt the effects of a high glycemic food if eaten together. And it's important to note that not all high glycemic foods are unhealthy and not all low glycemic foods are healthy. For example, some fruits are very high and ice cream is low. The most important goal is still quality, overall nutritional value and healthy, balanced combinations.

Energy Density

Energy density essentially means how many calories a food packs per bite. Low energy dense foods have fewer calories and high energy dense foods have more calories. For example, 1 cup of veggies only packs about 25 calories, but a mere tbsp of oil packs 120. Generally the more water, fiber and air in a food, the lower the energy density. But again, it's important to note that not all low energy dense foods are healthy and not all high energy dense foods are unhealthy. That's why it's also important to think about nutrient density, which looks at the amount of overall nutrition per calorie.

Daily Value

You'll see Daily Value on food labels. Each line tells you the amount of a nutrient one serving of the food contains compared to either the minimum or maximum target for the average adult. For example, 15 percent of the Daily Value for fiber means one serving provides 15 percent of the amount of fiber you need daily. It's especially helpful for quickly comparing two similar foods, like two types of cereal for their fiber values or two types of soup for their sodium values. But in my opinion the ingredient list of a packaged food provides the most important information – while a product may be a good source of something you want more of (like protein) or offer none of a nutrient you're trying to avoid (like sodium or sugar), it could still be loaded with artificial additives and preservatives. My motto: ingredients lists should read like recipes you could easily recreate in your own kitchen.

Cynthia Sass is a registered dietitian with master's degrees in both nutrition science and public health. Frequently seen on national TV she's a SHAPE contributing editor and nutrition consultant to the New York Rangers and Tampa Bay Rays. Her latest New York Times best seller is Cinch! Conquer Cravings, Drop Pounds and Lose Inches.