Food pyramids are comprised of building blocks for grown-ups. Instead of letters in the alphabet, these blocks represent food groups that you can put together to create a picture of a healthful diet. The essential message of all good guides to healthful food choices is that no one food is either good or bad — how much and how often you eat a food is what counts.

With that in mind, a food pyramid delivers three important messages:

• Variety: The fact that the pyramid contains several blocks tells you that no single food gives you all the nutrients you need.

• Moderation: Having blocks smaller than others tells you that although every food is valuable, some — such as fats and sweets — are best consumed in small amounts.

• Balance: You can’t build a pyramid with a set of identical blocks. Blocks of different sizes show that a healthful diet is balanced: the right amount from each food group.

Clearly, the virtue of a food pyramid is that using it enables you to eat practically everything you like — as long as you follow the recommendations on how much and how frequently (or infrequently) to eat it.

The first food pyramid was created by the U.S. Department of Agriculture (USDA) in 1992 in response to criticism that the previous government guide to food choices — the Four Food Group Plan (vegetables and fruits, breads and cereals, milk and milk products, meat and meat alternatives) — was too heavily weighted toward high-fat, high-cholesterol foods from animals. Figure below depicts the original USDA Food Guide Pyramid.

As you can see, this pyramid is based on daily food choices, showing you which foods are in what groups. Unlike the Four Food Group Plan, the pyramid separates fruits and vegetables into two distinct groups and lists the number of servings from each food group that you should have each day.

The number of servings is provided in ranges. The lower end is for people who consume about 1,600 calories a day, and the upper end is for people whose daily dietary intake nears 3,000 calories.

One useful aspect of the original USDA Food Guide Pyramid is its recommendation of different numbers of daily servings for people consuming different amounts of calories each day. For example, consider how the recommended number of servings from the bread group varies at different levels of calorie consumption.

By the time USDA/HHS got around to revising the Dietary Guidelines for 2005, it was pretty clear that the original food pyramid hadn’t done its proposed job of teaching most Americans how to choose foods that provide sufficient nutrients without piling on the pounds.

Like the original Food Guide Pyramid, this new version is made up of sections representing the foods in your daily diet — from left to right, grains, vegetables, fruit, oils, milk, and meat/beans. Like the building blocks on the original Food Guide Pyramid, the six bands on this one say “pick lots of different kinds of foods to build a better diet.”

The different sizes of the sections suggest that you should consume more of some foods than others. The steps going up the side of the pyramid say, “Physical activity matters, so get moving!” And the MyPyramid slogan, “Steps to a Healthier You,” tells you that you don’t have to leap tall buildings in a single bound like Superman (or woman) to improve your nutrition.

Even small steps can make a big difference. But the big deal about MyPyramid is that you can personalize the diagram to meet your own special needs. For more information, visit www.mypyramid.gov. Okay, warm up your typing finger(s) and run this one over your keyboard: www.mypyramid.gov.

This gets you to a Homepage with lots of special info buttons on the left side. Click on the one labeled My Pyramid Plan, and up pops a set of boxes into which you type your age, gender, and activity level to get back a personalized plan for your very own body and lifestyle.

The other buttons on the page are interesting, too. My Pyramid Tracker enables you to compare your current diet and level of physical activity with the newest recommendations from the nutrition guides.

Inside the Pyramid tells everything you ever wanted to know — maybe more — about the different food groups, including recommended daily amounts. For Professionals includes a downloadable worksheet that helps you track what you’re really eating — as opposed to what you sorta remember you ate the day before yesterday.