Stout has always been shrouded in secrecy, the beer style's name alone a synonym for defiance. 

Mysteriously deep ruby red to inky jet black in color and filled with toasty-malt flavor, it’s the only dark beer that survives and thrives in an otherwise golden-beer world.

But stout is suddenly having a moment, far beyond the annual St. Patrick’s Day boost. 

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"Stout is at this all-time high in terms of popularity," beer-industry analyst Bump Williams told Fox News Digital.

Former UFC champion Conor McGregor launched Forged Irish Stout in the United Kingdom, United States and his home nation of Ireland last year. 

Guinness of Dublin, Ireland, the world’s most famous stout brand, is booming. 

Sales rose 20% in North America last year, according to industry data. That's an almost unfathomable rise for a mature brand with deep distribution. 

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The hugely successful recent rollout of Guinness 0.0, its new non-alcoholic stout, has fueled the growth, said Williams, of Bump Williams Consulting in Connecticut.

Female drinkers have shown a sharp rise in stout consumption, too, as the dark brew reveals profound enlightenment.

"Of all the beer styles, stout is the healthiest when consumed in moderation," national beverage expert and certified cicerone (beer sommelier) Meagen Anderson of Michigan told Fox News Digital. 

Stout, she notes, is made with deep-roasted unmalted barley in the mash. The toasty barley gives stout its dark color and coffee-like flavors. 

But it does not have the fermentable sugars found in barley malt. 

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As a result, traditional Irish stouts have less alcohol and fewer calories and carbohydrates than mainstream golden lagers.

Stout is also rich in antioxidants, calcium, iron and B vitamins compared with lighter beers — just more examples of the style’s defiance.

"The dark color and coffee-like flavors throw people off," said Anderson, global sales director for Sustainable Beverage Technologies. 

She also recently founded the AFicioNAdo Certification Program. 

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It’s the world’s first initiative to teach beverage industry professionals about alcohol-free beer, wine and spirits. 

The non-alcoholic stout category is booming, she said, beyond just new Guinness 0.0.

Anderson suggested Athletic Brewing All Out Extra Dark, Gruvi Brewing Mocha Nitro Stout and Leader Brewing Night Strike for non-alcoholic stouts.

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