Vitamin D is known to be essential to many aspects of  human health  — but a new study suggests that taking a certain form of it can have a negative effect. The more potent and longer-lasting form, vitamin D3 (cholecalciferol) is produced naturally when the body is exposed to sunlight and is also found in  animal products, while vitamin D2 (ergocalciferol)   comes from plant or fungal sources, per the National Institutes of Health. Researchers from the University of Surrey in the UK found that