NEW YORK (TheStreet) -- Coca-Cola (KO) - Get Coca-Cola Company Report has long been a favorite of legendary investor and Berkshire Hathaway (BRK.A) - Get BRK.A Report chairman and CEO Warren Buffett, an affinity that's rewarded him and his shareholders handsomely over the years.  

But with consumer preferences around the world shifting to all-natural food ingredients at fast-food joints and grabbing "better-for-you" snacks at grocery stores, the "Oracle of Omaha's" unmatched investment judgment seems to be getting cloudy when it comes to his beloved Coke.

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"If you're looking for a wonderful business, it's hard to beat Coca-Cola," said Buffett in a surprise appearance at the company's annual meeting on Wednesday. Seeking to counter claims by advocates that Coke's products have too many calories, the folksy Buffett added, "One-quarter of all the calories I've consumed come from Coca-Cola, and I tell you I feel healthy."

Unfortunately for Coke, Buffett's relative health, given his diet, may make him a true outlier. According to the Centers for Disease Control and Prevention, 29.1 million people, or 9.3% of the U.S. population, now have diabetes. More than one-third, or 78.6 million, of U.S. adults are considered obese.

As a result, Buffett's comment in the below video from Coke's annual meeting may be oddly telling as the company's future.  "Of course, I could buy the world of Coke," he said, "but I am not sure if my shareholders would go for that."

Admittedly, knocking Buffett's judgment on Coke is tough. According to Berkshire's 2014 annual letter, the cost basis for its Coke holdings, which the company began accumulating in 1988, is $1.29 billion. The market value for that stake at the time the report was issued in February was a whopping $16.9 billion. The industrial and insurance conglomerate now owns roughly 9.3% of Coke as the soft drink maker has recently plowed billions of dollars to share repurchases. Coca-Cola is considered one of Berkshire's "Big Four" equity holdings, right alongside America Express (AXP) - Get American Express Company Report, IBM (IBM) - Get International Business Machines (IBM) Report and Wells Fargo (WFC) - Get Wells Fargo & Company Report.

An unrealized gain by Berkshire on Coca-Cola of such a magnitude reflects Buffett's foresight on the storied soda brand many years ago. Just a few of the wagers the much younger Buffett made correctly included how Coca-Cola would still hold the dominant cola market share in the U.S. over arch nemesis PepsiCo (PEP) - Get PepsiCo, Inc. Report; how numerous execs brought through Coke's ranks would address new growth areas in packaged water, sports drinks and teas; and how Coke would further penetrate emerging markets as the incomes of their residents expanded.

However, Buffett should consider channeling that old-school foresight he applied years earlier to Coca-Cola and think about what several changes occurring in the world today may mean for Coke 10, 20, 30 years in the future. The stock market may be doing some homework of its own -- over the past two years, Coke's shares have declined 3.6%, Pepsi's have gained 14.9%, and Starbucks (SBUX) - Get Starbucks Corporation Report stock has risen a cool 60.4%.

As of today, Buffett's world of Coke is largely not partaking in the latest trends among consumers. The company has no snacks division. Its trademark Coca-Cola beverages accounted for 45% of the company's U.S. unit case volume in 2014. Its embattled chairman and CEO, Muhtar Kent, has gone on record in support of keeping artificial sweetener aspartame in its drinks, even as consumers shun the ingredient because of health concerns.

An in-depth reassessment by Buffett himself on Coke seems unlikely given his longtime attachment to the brand. So that needed assessment is likely to fall on the shoulders of Buffett's two handpicked successors who are managing Berkshire's equity portfolio -- Todd Combs and Ted Weschler.  The co-managers could decide to pull the trigger on a reduction in the exposure to Coca-Cola's murky future once a deeper, clear-headed analysis is made. TheStreet takes a look at two major reasons why such reassessment is warranted.

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1. Consumer preferences are changing, and calories and ingredients matter more than ever.

People are not only reducing soda intake to watch their waistlines, they are trying to determine the origin of the ingredients inside brown, fizzy colas should they opt to indulge on a weekend. Buffett may be oblivious to these things, but the next crop of investors aren't. 

Better still, execs across the food industry are huddled up in board rooms seeking new ways to improve ingredient quality and the associated marketing. To wit, Coca-Cola has not kept pace with some of the biggest changes now unfolding in the food industry, instead continuing to rely on classic colas with artificial sweeteners, sugary sports drinks, and energy drinks with ingredients that are more lab-grown than local farm-grown.

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One of Coke's main health-oriented innovations in the past year came with its "Life" cola. Released nationwide last fall, the drink boasts 60 calories per eight-ounce glass bottle and is sweetened with real cane sugar.

However, a host of companies in the food business are moving even more quickly to address shifts in consumer tastes.

On April 24, Pepsi announced that beginning in August, Diet Pepsi, Caffeine-Free Diet Pepsi and Wild Cherry Diet Pepsi in the U.S. will stop using controversial ingredient aspartame and instead be sweetened with a blend of sucralose and acesulfame potassium. Aspartame has been linked to cancer in lab mice, among other potential health risks. According to Beverage Digest, Diet Pepsi sales fell 5% last year, whereas Diet Coke dropped 6.6%.

In an interview on CNBC the day of Pepsi's splashy announcement, Muhtar Kent reiterated that he felt aspartame was safe. Coke did not respond to a request for comment for this story.

Chipotle (CMG) - Get Chipotle Mexican Grill, Inc. Report, which serves classic Coca-Cola, Diet Coke and the company's Minute Maid line from fountain machines, could force changes on its beverage partner to make its menu even healthier. As of this past Monday, all of Chipotle's over 1,700 U.S. restaurants, as well as its Asian fare concept ShopHouse, which counts 10 locations, began serving GMO-free food following a two-year long effort by the company to completely remove them from the menu.

The widespread use of GMOs has spawned concerns on the part of health groups and consumers who argue that non genetically modified foods are healthier to ingest.

Even McDonald's (MCD) - Get McDonald's Corporation (MCD) Report, another partner with Coca-Cola, has gotten involved in enhancing its ingredients.

On March 4, McDonald's announced that it plans to start sourcing chicken raised without antibiotics important to human medicine as well as milk from cows that are not treated with the artificial growth hormone rbST. The Golden Arches will phase in the new chicken over the next two years, and will start to introduce the new milk later this year.

Coca-Coke has acknowledged changes in consumer preferences are a risk to earnings. "Consumer preferences are evolving rapidly as a result of, among other things, health and nutrition considerations," pointed out the company in its 2014 annual report. "If we do not successfully anticipate these changing consumer preferences or fail to address them by timely developing new products or product extensions through innovation, our share of sales, volume growth and overall financial results could be negatively affected," 

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2. Coke needs more non-Coke revenue.

Total U.S. carbonated soft-drink sales volume fell 0.9% last year, the tenth-straight year of decline, according to Beverage Digest. Within that category, Coke posted a 1.1% decline in volume, while Pepsi realized a 1.4% decline. 

The focus by Coca-Cola execs on smaller package sizes for its regular soda to boost profits, and new low-carb "Life" to placate health conscious consumers, has still left the company overly exposed to waning carbonated soft-drink sales and competitive pricing in the United States. Coke has chosen to invest its vast riches into more ventures in the competitive beverage industry, as opposed to building a complementary snacks business. 

In effect, Coke is not acting to widen its economic moat. An economic moat, an important concept often mentioned by Buffett, represents the competitive advantages a business has in place to protect its profits and market share.   

For its part, Coke has amassed a 16% stake in coffee brewing system maker Keurig Green Mountain (GMCR) . The coffee company will exclusively make Coca-Cola-branded, single-serve pods for its upcoming Keurig Cold at-home beverage system. In August last year, Coke announced it was taking a 16.7% stake in energy drink maker Monster Beverage (MNST) - Get Monster Beverage Corporation (MNST) Report for $2.15 billion.

On the other hand, while Pepsi's sales of carbonated soft drinks continue to be pressured, at least the company has built a formidable food business to support its profits. And that business' latest innovations, from clever new chip flavors to three-minute-prep Quaker Oats cereal, is helping to offset sluggish sales of soda.

"Frito Lay clearly ticked up another notch," said PepsiCo Executive Vice President and CFO Hugh Johnston in an April 23 interview with TheStreet. Volume for the Frito Lay North America and Quaker Foods North America divisions rose a solid 3% and 2%, respectively in the first quarter. Frito Lay's performance was related to the larger economy as well as to improved pricing and a host of new products.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.