25 Feb 2022 --- Vitamin D2 has a questionable role on human health, while vitamin D3 may help with fighting viral infections, a collaborative UK study by the Universities of Surrey and Brighton has revealed.“The main implication of this study is that dietary intake of vitamin D2 should not substitute for vitamin D3. Although this may sound controversial, it is possible that vitamin D2 could harm health by interfering with the physiological roles of vitamin D3,” Colin Smith, lead author of the study and professor at the University of Surrey, tells NutritionInsight.