Dark chocolate may be good for you. (Image credit: Getty Images/Flickr RF)

Today could be the healthiest Valentine's Day on record, with more Americans than ever reaching for dark chocolate over milk chocolate, experts say.

Heightened public awareness about the health benefits of dark chocolate has turned what used to be seen as a guilty indulgence into a must-have staple. The dark stuff contains a higher level of cocoa flavonoids, which recent scientific studies have found combat bad cholesterol and lower blood pressure.

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A devotion to dark is obvious from farmers markets to supermarkets, where shoppers are bombarded by dark chocolate bars containing 70, 80, and 90 percent cocoa solids.

Fast-food shops are even getting in on the trend. Krispy Kreme unveiled a dark chocolate donut this month and Dunkin' Donuts is peddling "dark hot chocolate."

"It's growing and it's growing and it's growing," Katrina Markoff, owner of Vosges Haut Chocolate, an edgy chocolatier based in Chicago, told ABCNews.com. The company's dark chocolate bacon bar outsells its milk chocolate cousin by a lot, she said.

"We sell millions of those," said Markoff.

Milk chocolate still reigns, with 29 percent of Americans over age 45 preferring dark chocolate and 15 percent of Americans age 18-44 reaching for the less sweet, healthier option, according to a survey by the National Confectioners Association.

But the dark trend is on an undeniable upward swing, said Susan Smith, an association spokeswoman.

A nutrition researcher at Harvard's School of Public Health said the potential of dark chocolate is exciting scientists, but some consumers are getting the wrong message.

"We're in the middle of a scientific revolution in the understanding of cocoa flavonoids," Eric Ding told ABCNews.com.

So far the only proven positive effects of dark chocolate come from research that studied a daily consumption of 400-600 mg of cocoa flavonoids - about 10 chocolate bars. Scientists have extrapolated that there are some benefits, though smaller, for, say, just one bar a day, he said.

Shoppers should balance calories and sugar with dark chocolate's benefits, he said.

"It's not an all-you-can-eat blank check to eat chocolate," he said. Markoff gets her low-calorie cocoa flavonoid kick by making cocoa smoothies at home with almond milk, cocoa powder and Stevia, an artificial sweetener, she said.

Aside from health benefits, some love the intense, bitter taste of dark chocolate. Even kids, who typically have a sweeter palate than adults, now reach for dark, a local homemade chocolatier said.

"I'm finding more and more kids who are dark chocolate fans," said Erin Andrews, founder of Indi Chocolate, which sells dark chocolate only, in Seattle's Pike Place Market. "It's very surprising to me. It seems to be a rising trend of kids going directly to dark."

Candy bar companies are taking note, angling to win more of the U.S. chocolate candy market, expected to hit $21.8 billion this year, up 3.7 percent compared with last year, according to Packaged Facts. Brands including Snickers and Kit-Kat now come in the dark variety.

And then there's emotion. For some, dark is more romantic.

"When I'm frustrated, I like milk chocolate," Markoff said. "When I'm in love, I like dark chocolate."