For the nutritionally conscious food shopper, a stroll down the supermarket aisle has become the visual equivalent of a frenetic day at the carnival: With each visit, new nutritional claims leap from boxes and packaging to hawk their products' healthful attributes, a cacophony of urgent and eye-catching messages.

"Sensible Solution!" cry the packages of cookies, lunch meats and mac 'n' cheese. "Approved bestlife!" calls the reduced-fat mayonnaise. "3-a-Day!" sings the tub of yogurt. "Whole Grain," declares a yellow stamp bearing the image of a bountiful sheaf of wheat. Even the venerable American Heart Association is contributing to the din, its distinctive "Heart Check Mark" calling out from the labels of breakfast bars, canned soups and frozen chicken nuggets.

The number of such appeals grows yearly. The "Med Mark," a new label due to appear on packaging this summer, is expected to tout products that would be part of the Mediterranean diet, thought to be the key to longer life and lower heart disease and cancer rates among populations that live along the Mediterranean Sea.

Now some nutrition researchers and advocates are crying: Enough!

They're calling for the jumble of private icons, graphics and categories to be replaced with a single, FDA-sanctioned certification program. The result would be a simple, recognizable standard, such as red/yellow/green lights, that would give consumers an authoritative assessment of whether a food product should be a regular feature of a healthful diet.

The proliferation of nutritional programs, symbols and registries is "well-meaning" but has become a formula for confusion even for nutrition-savvy consumers, says Michael Jacobson, executive director of the Washington-based Center for Science in the Public Interest and the author of the new proposal.

The proposal is endorsed by the chairman of the Senate Agriculture Committee as well as by seven leading nutrition researchers. One is Dr. Walter Willett, professor of epidemiology and nutrition at Harvard University's School of Public Health, who should know his way around a "Nutrition Facts" panel: He spearheaded the recent requirement that food labels list trans-fat content.

Yet even he is sometimes led astray by packaging labels that accentuate a product's positive attributes without owning up to its nutritional shortfalls, he says. An example: He recently took home a loaf of whole-wheat bread with an official-looking symbol, only to find it packed with sodium. "It's challenging, even for someone who is well aware of the issues and who cares lots about them," he says. "You can be misled."

In the next few months, Senate Agriculture Committee Chairman Tom Harkin, D-Iowa, expects to introduce legislation that would ask the FDA to take the first steps in devising a single system of classifying the healthfulness of foods for product labels.

"Only with reliable, consistent and easy-to-understand information can consumers take charge of their own health," Harkin says. "Common-sense food labeling is good for Americans' health."

The FDA has long had a system designed to regulate the "health claims" that product labels are allowed to bear. But as consumer interest in nutrition has grown, marketers and manufacturers of food have scrambled to design symbols and icons that would guide nutrition-minded consumers to their products — while avoiding specific health claims that are FDA-regulated. Food manufacturers, grocery stores and organizations dedicated to lifestyles, environmental causes or the prevention of specific diseases all have different criteria for lending their stamp of approval to a product, and many have an array of icons to attach to foods.

Most — including organizations such as the American Heart Association and Oldways, the nonprofit nutrition group that plans to launch the "Med Mark" symbol — have a financial stake in doing so, as well. The American Heart Association charges manufacturers a fee to use its "Heart Check" and promises that the symbol will boost sales. "Ninety-two percent of consumers think the heart-check mark is 'important' or 'very important' in choosing and buying foods," the Heart Association's guide for manufacturers states.

As a result of this jumble of competing and often inconsistent schemes, products that are very high in, say, sugar, might easily display the American Heart Association's "Heart Check"; some salty snack foods are stamped with PepsiCo's "Smart Spot" label; and cheese and dairy products, including those with high levels of saturated fat, get to brandish the National Dairy Council's "3-a-Day" emblem.

Willett suggests that manufacturers' freedom to focus on a product's best attribute — paired with Americans' propensity to look for just one or two nutrients rather than at a whole nutritional package — makes it inevitable that marketing icons will promote dietary mistakes.

"Of course a lot of people are not fully informed, and some are oriented to look at one thing," he says. "You should make your choice not just on one factor or nutrient but a balance of all of them."

A single standard would help consumers do that, he says.

In the case of Med Mark, products that are culturally and nutritionally part of a traditional Mediterranean diet would likely get Oldways' nod — for a fee. But the organization is careful to avoid the suggestion that the prominent M that will be its talisman will bring better health.