Francisco Rosero, endocrinologist: Avoid eating bread in the morning, it’s the “worst way to break your fast”

There are few foods more universal than bread, whose countless varieties are, in many ways, a portrait of the planet itself. That much isn’t up for debate. What is increasingly questioned, however, is bread’s place as a healthy staple. Many people kick off a new diet by cutting out bread altogether or swapping it for whole‑grain or sourdough options. The problem, according to endocrinology specialist and science communicator Francisco Rosero, is that even these alternatives aren’t exactly nutritional nirvana.

Rosero explains that, nutritionally, all of these styles of bread are more similar than most people think: foods made largely of carbohydrates with limited overall nutritional value. “The popular sourdough bread is still bread - still a carbohydrate with very poor nutritional value. It contains about 55 grams of carbohydrates, the same as white bread. The difference is minimal. Its glycemic index is around 60; white bread is about 70. Practically the same,” he says.

“Sourdough bread is still made from wheat gluten”

Rosero notes that “the fiber content is roughly 4 grams, compared with white bread’s 2 grams,” a gap he describes as “insignificant”. Meanwhile, the caloric content is “exactly the same as white bread”. All these numbers point to one conclusion: sourdough’s supposed advantages over the traditional white loaf are modest at best.

And the difference doesn’t begin in the bakery, either. Natural fermentation doesn’t eliminate gluten. “Let’s not forget that sourdough bread is still made from wheat gluten,” he says. “Our intestines don’t tolerate gluten particularly well. Remember, gluten entered the human diet only about 400 years ago - we’re not fully equipped to metabolize it.” He adds that “gluten increases intestinal permeability and triggers inflammation system‑wide”. Some argue that fermentation reduces gluten content, but Rosero insists that “the reduction is minimal”.

Given all of this, he stresses that “so far, there is no scientific evidence that sourdough bread is a healthy product”. He concedes that “it might be slightly better than white bread”, but underscores that “it’s still bread”. And timing matters, too. “The problem with bread is when we usually eat it - first thing in the morning to break a fast - and that’s the worst way to break a fast,” he argues.

He explains: “If your insulin is high, if your blood sugar is elevated, if you have diabetes, if you’re overweight, if you have fatty liver disease, you should not break your fast with bread.” That applies to both white bread and sourdough alike. He wraps up his point in unmistakable terms: “Avoid bread - it’s pure carbohydrate with very little nutritional benefit.”

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