Vitamin D3 (cholecalciferol) is found in products of animal origin, whereas vitamin D2 (ergocalciferol) is found in products of plant origin. Evidence suggests that vitamin D3 is more effective at raising plasma concentrations of 25-hydroxyvitamin D [25(OH)D] when compared to vitamin D2. Plasma 25(OH)D is the accepted marker and biologically active form of vitamin D. A recent meta-analysis published in the American Journal of clinical Nutrition1 investigated the effectiveness of cholecalciferol and ergocalciferol at raising plasma levels of 25(OH)D in humans. Data taken from randomised controlled trials suggested that cholecalciferol had a significant positive effect at raising plasma concentrations of 25(OH)D, when compared to ergocalciferol. Therefore vitamin D3 remains the supplement of choice with respect to raising plasma levels of 25(OH)D. Some supplement companies and the medical industry continue to use ergocalciferol as the form of vitamin in tablets, suggesting they have not read the literature.
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