A deficiency of which vitamin was originally called mal del sol?

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Niacin deficiency was originally called mal del sol, which means "sickness of the sun" in Spanish. This is because the deficiency was associated with people living in areas with high sunlight exposure, as sunlight destroys niacin in food sources. Niacin deficiency can cause a condition called pellagra, which is characterized by dermatitis, diarrhea, dementia, and eventually death if left untreated.

A Deficiency of Which Vitamin Was Originally Called Mal Del