I remember the first time I heard someone talk about clean eating. I smiled and nodded the way most of us do when we're stuck at that point between not understanding and sneaking away to search on the smartphone. But eventually I got it -- mostly -- and I found out that "clean eating" doesn't specifically involve extra work with the potato brush. The gist of this highly discussed but loosely defined dietary movement is to select foods with basic ingredients -- stuff that your great-grandma could have gathered down on the farm. It also warns us away from many traditional brands.

Eating clean has been discussed since the '90s, but it's become a significant movement in recent years, moving to prominence alongside its kin, the Paleo diet, urging us to "eat close to the ground." In the quest for wellness, fitness, and weight loss, these healthy-eating approaches ask us to avoid ingredients with chemical-sounding names. They also send a clear message to shun processed foods. According to Eating Clean for Dummies: "Processed foods are any food that has a label. A label means that more than one ingredient was used to make that food." Got it? No more Fruit Roll-Ups for the kids.

How prominent is clean eating? Real data are hard to come by, in large part because of the lack of specific definitions around "eating clean." Ask five clean eaters how they do it, and you'll probably get five different answers. One thing is clear, though: Clean eating has become its own industry. If inspiring a "for Dummies" book isn't evidence enough of popular appeal, check your favorite search engine. Millions of results turn up for "clean eating," running the gamut from magazines to blogs, books, and recipe sites.

"Seventy-two percent of consumers said they prefer products with ingredients they recognize and would use at home," according to Food Business News. While this isn't clean eating per se, it is evidence that the trend is catching the attention of consumers, and it's a clear call to action for food manufacturers.

Spicy Salad Crunch Mix

Sprouts. Source: WholeFoodsMarket.com Blog

Clean eating and the food industry
If you happen to be Whole Foods (NASDAQ:WFM), all this interest in basic ingredients is good news. As purveyors of lots of "one-ingredient" foods and packaged products that scream "green," Whole Foods and its ilk can pretty much be considered genuine resources for clean eaters.

But what about those pillars of the food chain that have long made a living out of sourcing from the Corn Belt and beyond, pumping out "processed foods" to shelves around the world? You can be sure that food manufacturers such as General Mills (NYSE:GIS) and PepsiCo (NYSE:PEP) have felt the pinch as consumers increasingly scrutinize labels. How can these big guys stay relevant when the realities of the mass-market supply and distribution chains seemingly demand more complex food processing? How do you persuade consumers to put your goods in the cart, even if they're interested in eating clean?

What is a clean label, anyway?
Food manufacturers can't simply label their products as "clean." After all, food labeling demands adherence to specific definitions, and "clean eating" is not specifically defined. Their tactics have instead included implying clean eating with words such as "natural" and "whole grains," as well as more difficult-to-attain labels such as "organic." They've also embraced the "-free" movement by advertising, for example, "GMO-free," "gluten-free," and "additive-free" when possible. Yet it seems savvy consumers have seen through many of these tactics, prompting the food manufacturers to step up their games yet again. How does a product from a traditional processed-foods manufacturer present itself as viable to a clean eater?

Reader's Digest, an unlikely participant in this discussion, instructs shoppers: "How can you be sure a particular packaged food is good for you? One thing to look for is a short ingredient list." It lists a number of single-ingredient products, including Pepsi products Quaker Oatmeal and Tropicana Pure Premium Juice, which are specifically not branded with the cola maker's label.

Smucker (NYSE:SJM) has taken up the challenge with its Fruit-Fulls line of blended fruit in a pouch. In addition to its claims of "pure" and "all natural," it posts its short ingredients list front and center on the box: "Apples. Strawberries. That's it." The company has announced an upcoming launch of its Fruit and Honey line of preserves -- another two-ingredient product.

Food giant General Mills, long synonymous with processed foods, has been struggling to gain market share and improve earnings. The company has a number of labeling and reformulating initiatives targeted toward bringing clean eaters back to the fold, but this is a daunting brand-image problem. The company's pending acquisition of natural-foods brand Annie's, for instance, has raised a firestorm of concern over whether product purity will be compromised.

Cheerios

Credit: General Mills.

In January, General Mills will roll out a dramatic reformulation in the form of a product called Cheerios + Ancient Grains. Without question, "ancient grains" makes me think of hearty, fiber-filled, natural stuff, but I checked a definition just the same. After all, would we know if a grain was older than, say, wheat or oats? Does it matter? Does "ancient" suggest the opposite of "genetically modified"? It turns out that the grains in this soon-to-be-released breakfast-bowl filler are many of the mainstays of health-food aisles -- quinoa and wheat varieties spelt and kamut. The new Cheerios will also still contain oats and sugar.

The battle for bellies and bucks
Eating under the "healthy" umbrella is expensive. The new Cheerios are priced to roll out at $4.39 for a 12-ounce box, compared with $3.99 for 14 ounces of traditional Cheerios. Many of the healthful-eating practices promoted by clean eating require both a robust food budget and access, two ingredients that are simply not available to everyone. In many respects, efforts to drive consumers away from mainstream packaged foods and toward the health-food store are most easily fulfilled by shoppers with more disposable income and a way to purchase fresh food. For the food manufacturers, the lost consumers are also probably the biggest spenders. Finding formulations and labels that will appeal to these key shoppers is a high-stakes business. Whether or not this group will believe the message and buy remains to be seen.

John Mackey, co-CEO of Whole Foods Market, is a member of The Motley Fool’s board of directors. Beth Nichols has no position in any stocks mentioned. The Motley Fool recommends PepsiCo and Whole Foods Market. The Motley Fool owns shares of PepsiCo and Whole Foods Market. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.