Sprouts Famers Market produce clerk Brendan Foley stocks oranges. © Andy Cross, The Denver Post via Getty Images

Demand for organic and natural foods has been booming. And there's no end in sight.

Consider that the Department of Agriculture's Economic Research Service reported U.S. organic food sales of $28 billion in 2012, accounting for over 4 percent of total at-home food sales. That's up by double digits from 2011 sales of about $25 billion, and more than 150 percent growth from 2004 sales of $11 billion.

The Wall Street Journal recently reported that widening the scope to include "natural" -- along with organic -- sales pushed the total grocery market to $48 billion in 2012 -- up eight-fold from 1998.

Some of the reasons consumers have embraced the organic revolution include a desire to avoid nasty pesticides on their veggies and concerns about how harsh industrial fertilizers affect the environment.

But the incentives driving investors into organics are much more pragmatic: a desire to be where the money is.

Not only is there clear growth in organic food sales, there also is built-in stability thanks to the consumer-staples status of foodstuffs.

Of course, a lot of growth has already been priced in -- as evidenced by organics poster child Whole Foods Market (WFM). And competition is increasingly fierce, as evidenced by mega-retailer Wal-Mart (WMT) recently deciding to apply its low-price approach to organic produce in a big way, even if it means low margins for itself (and everybody else) as a result.

Still, if you're looking to tap into this fast-growing market, there remains a lot of potential. Look beyond the fashionable leader of Whole Foods and consider these three lesser-known organics players.

United Natural Foods

United Natural Foods (UNFI) is one of the biggest distributors in the space, and has been a major player in organic and natural foods for about two decades. While the ubiquitous Whole Foods is its top client, worth about a third of total sales, UNFI also serves a variety of smaller organic retailers nationwide that provide diversity to revenue.

UNFI has been aggressively growing by acquisition, including four deals in the past two years. As a result of these buyouts and strong growth to its existing business, United Natural Foods has seen revenue soar from about $3.75 billion in fiscal 2010 to a projected $6.75 billion for 2014.

United Natural Foods stock has admittedly softened up in the past several weeks, down about 15 percent from its March high. But even so, UNFI has returned 32 percent in the past 12 months to easily outperform the 18 percent gains by the S&P 500 ($INX) in the same period.

With a more reasonable forward price-to-earnings ratio of around 22 and double-digit growth projected for both sales and profits in its upcoming earnings report, the time may be right to consider taking United Natural Foods to the checkout line.

Hain Celestial

Hain Celestial (HAIN) is behind some of the best-known brands in the organics space, including Celestial Seasonings tea and Earth's Best packaged foods.

And like United Natural Foods, the big potential in the industry has spurred a series of acquisitions over the past few years to ensure continued dominance. Most recently, HAIN acquired rice products company Tilda in January for $357 million as a way to bolster its gluten-free offerings to tap into this fast-growing sub-segment of the organic marketplace. And before Tilda, Hain snapped up Ella's Kitchen Group about a year ago to bolster its line of organic baby foods.

Both moves are great examples of how Hain Celestial is trying to stay ahead of consumer tastes and maintain market share. But both moves also are set to add big revenue over the coming years to keep up the company's track record of sales and earnings growth.

In fiscal 2010, Hain Celestial recorded just $917 million in sales and earnings of about 69 cents a share, according to S&P Capital IQ. For the current fiscal year, revenue will top $2.1 billion and earnings will total about $3.12 a share, an impressive 130 percent sales growth and 450 percent profit expansion.

No wonder HAIN stock is up over 43 percent in the past 12 months and over 430 percent since the 2009 lows to dramatically outperform the market.

Sprouts Farmers Market

Sprouts Farmers Market (SFM) is a specialty retailer of organic food and health-care products.

And while the mid-cap stock has given some investors a bit of indigestion since SFM went public in mid-2013, with modest volatility and an overall return of about negative 11 percent, don't count out this company just yet.

In addition to the tailwind the broader industry enjoys, Sprouts has a -- pardon the pun --  more organic path to growth than Hain or UNFI; the improvement in fundamentals is owed to more shoppers and same-store sales growth rather than acquisitions.

That's why UBS recently upgraded SFM stock from "neutral" to "buy," with a $43 price target -- 20 percent upside from here. Separately, analysts at Guggenheim and BMO also increased their outlook on Sprouts.

While there admittedly isn't a lot of earnings history given the recent IPO of Sprouts and while the company continues to invest in expansion, the sales growth tells a pretty impressive story.

In fiscal 2010, Sprouts recorded about $516 million in revenue but in fiscal 2013 it had tallied almost $2.5 billion in sales. While that period did encompass the 2012 buyout of Sunflower Farmers Market, which operated 38 locations in the southwest, the biggest driver of growth has been continued same-store sales improvement and the rollout of new locations under the Sprouts brand.

In fact, big growth plans are fundamentally why SFM went public to begin with. In its regulatory filings as it approached its IPO, Sprouts projected a double-digit compound annual growth rate until 2020 for the organics business broadly and plans to increase its store count to 1,200, more than seven times the roughly 170 stores Sprouts currently operates.

Time will tell whether SFM can live up to these ambitious expectations. But given the momentum of the organics biz, its currently successful business model and a recent IPO that has armed the company with cash, investors who get in to Sprouts stock now could see big growth over the long term.

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