I was looking through USDA data, as I do from time to time, mindlessly scrolling through numbers and names of foods, when a column in a spreadsheet gave me pause. I had opened the government agency's most recent estimates of fruit consumption and realized that grapefruits, for some reason, have become terribly unpopular.

It is not that we have completely abandoned the sometimes sweet, tangy citrus spheres — as of 2013, Americans still ate just over 2.5 pounds of fresh, pulpy grapefruit on average each year. But we are well on our way.

In 1976, at the height of America's love for grapefruit, few fruits were more popular. The average person living in the United States ate almost 25 pounds of grapefruit each year. Since then, however, fresh grapefruit consumption has plunged by 70 percent, and total grapefruit consumption, which includes the processed kind often used for juice, has tumbled by almost 80 percent.

The drop is perhaps most stunning when seen in the form of a chart:

What really struck me about that column in the spreadsheet — and this visual representation above — is that anecdotally I actually would have guessed that just the opposite had happened. Grapefruits, it seems to me, have become a staple of breakfast and brunch menus, whether served sliced over granola or halved with accoutrements sprinkled on top. And the data kind of bear that out: Market research firm Technomic, which has tracked the popularity of various menu items for years, estimates that grapefruit's menu penetration increased by almost 15 percent last year.

Grapefruit, I also would have imagined, has benefited from the growing skepticism about eating carbs — in place of pancakes and french toast, people must, at least sometimes, be choosing big, meaty, reddish pink citrus. And the lore of grapefruits has long been that they contain a fat-burning chemical (however overstated it might be), the perfect characteristic to propel any food into the upper echelon of the food craze world. Indeed, the grapefruit diet has its own Web site, which proclaims, rather loudly, that followers can expect to lose up to an unthinkable 10 pounds in 12 days.

But something is awry. Despite what grapefruits have going for them — have I mentioned that they're delicious? — there are a handful of other much less fortunate trends holding them back.

A dangerous mix

Few things have contributed more to grapefruit's demise than the growing body of research that says eating the citrus could intensify the effects of some medications. The first studies connecting the two appeared decades ago, in the 1970s and 1980s, but more recent research has built on the notion that mixing grapefruits and certain medications can be a lethal combination. The FDA, wary of the danger, went so far as to publish a report last year warning consumers about the risks and delineating the pills that don't pair well with the citrus. Among those medications is Lipitor, which is meant to help lower cholesterol, Nifediac, which is meant to help lower blood pressure, Buspar, which is taken for anxiety, and Allegra, a popular antihistamine.

That alone would be a big problem. But it is made even worse by the fact that some of the people who like grapefruits the most — older people — are also the ones who are most likely to be prescribed one (or several) of the above medications. The USDA's marketing research center noted as much in a report released in 2006.

"While per capita consumption of most citrus products has remained strong or increased in recent years, per capita consumption of grapefruit has weakened," the report said. "Because a large percentage of grapefruit consumers are older and more prone to taking medication, it is thought that this has affected overall consumption."

"Our consumers are in their 50s, 60s and 70s," said Doug Bournique, who is the executive vice president of the Indian River Citrus League, which represents the largest grapefruit region in the world. "I have spoken to many of them who say 'I love grapefruit, but my doctor says I can't eat it.'"

Bournique worries that the pill industry has propped itself up at the expense of the once rotund citrus industry. "It’s kind of sad that people rely on a pill to make everything better," he said.

Squeezed out

Changes happening in the juice aisle aren't helping either. The growth of competition from various other fruits has stymied the popularity of processed grapefruit, which is normally used in drinks. And that's compounded by the fact that people are drinking less juice overall. Juice sales have fallen in five consecutive years, according to market research firm Euromonitor. Americans, a recent report from the group says, are growing more concerned that juices, which typically contain a lot of sugar, aren't as healthy as once believed.

And people, though they are drinking less orange juice, are increasingly choosing it over its tangier counterpart. "Processed grapefruit competes directly with processed oranges," the Food and Agriculture Organization noted in 2010. Consumers, it added, "continue to move towards orange juice and away from grapefruit juice."

Grapefruit juice consumption fell by almost 60 percent between 2000 and 2007 alone, according to Florida Citrus.

Grapefruits, some in the industry sigh, are likely falling victim to the growing demand for convenience in the United States, too. Americans want foods that are fast and easy, fruits that can be eaten with a single hand.

"It's not a convenient fruit," Rusty Banack, a Florida grapefruit farmer, told the New York Times last year. "Nowadays people want to grab a banana, an apple, and head out the door."

USDA data show that this is, in many ways, true. Americans eat almost 40 percent more fresh fruit that they did some 40 years ago. Bananas, in particular, have grown in popularity over the years — consumption is more than 60 percent greater per person than it was in the 1970s.

"That shift has been going on for almost 30 years," Bournique said. "The convenience factor, I can’t overstate it enough."

You can't eat what you can't grow

Nothing, however, has been more detrimental to America's ability to enjoy grapefruits over the years than an insect-borne disease called citrus greening, which has ravaged production. The disease, which first crept into Florida, where some three-quarters of all grapefruits are grown in the country, in the early 2000s, has turned grapefruit farming into a nightmare.

"This disease has been a game changer," Bournique said. "It's not like other, older historical diseases that wipe out a small portion of your crop. This disease could decimate the entire citrus industry."

In some ways, it already has. Trees are dying off as a result — the amount of land used for grapefruit trees is roughly a quarter of what it was in the late 1990s —and becoming less productive — grapefruits are falling too early from the trees, and are often too small to meet the standard size sold in the United States. In all, Florida grapefruit production is down more than 60 percent since the turn of the century, according to data from the USDA. Nationally, production is down by roughly the same.

Naturally, grapefruits, which are typically among the cheapest citrus, have gotten more expensive over the years. And higher prices have meant even lower demand.

The industry insists that a revival is just around the bend. Earlier this year, Ocean Spray, the agricultural cooperative owned, in part, by more than 100 grapefruit growers in the United States, issued a press release promising the troubled fruit's comeback. "It's time to get reacquainted with the naturally invigorating taste, goodness and versatility of grapefruit," the release said. Production, the cooperative blushed, is expected to rise for the first time in years.

Others expect output to remain pinched, but insist they are similarly optimistic. "While the quality of this year's crop is shaping up nicely, we expect that volume will be down again this year," David Steele, the director of public relations for the Florida Department of Citrus, said in an e-mail. "It's not clear when our growers will 'turn the corner.'"

"Based on history, though, we know that eventually they will," Steele added. "Whether the challenge has been pests, disease, hurricanes or freezes, our industry has always found a way to rebound."

It's hard to sugarcoat the fate of the increasingly underappreciated fruit here in the United States. The rush to figure out how to stop the spread of citrus greening has proved both unfruitful and extremely costly. Grapefruit ads were once a staple on television and in print, but the industry, realizing the severity of the disease, has had to shift virtually all of the money it once spent on marketing to research.

"We used to have some really nice TV commercials that highlighted how great grapefruit was," Bournique said. "We’ve had to mothball all of that just because of the need to keep trees alive. We can’t promote our product like we’d like to because we have to spend all our money keeping it alive."

At the moment, production forecasts aren't exactly favorable going forward: A 2012 report by Florida Citrus suggests that in the best-case scenario supply will remain flat over the next decade (in the worst, the industry will see "severe production declines"). The various cultural and societal trends — the villainization of juice, prioritization of convenience, etc. — as well as the unfortunate reality that grapefruits interact poorly with popular medications, aren't going away either.

Neither will grapefruits. Nor, it seems, will Americans be able to love them like they once did, many years ago. Things, sadly, simply aren't looking quite as rosy for the oversized citrus as trendy breakfasts in Brooklyn might make it seem.