"Cod fish only contains vitamin D3. There is no vitamin D2 in either cod fish or cod liver oil." - Dr. Jacob Exler, Nutritionist, USDA Nutrient Data Laboratory
Rosita EVCLO contains exactly what you would find present in the liver of a "living" wild codfish - nothing more and nothing less. Though vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) are available in a fish's diet, vitamin D2 is almost absent in fish and fish liver oils.
The Mystery Why Fish Liver Oils Only Contain Vitamin D3
What remains a mystery to scientists and marine experts is why the only form of vitamin D that has been identified in fish oils is vitamin D3. You would expect vitamin D2 would be present especially if vitamin D2 produced in phytoplankton was concentrated in the food chain. The main explanations for this observation include:
1. Fish have the ability to discriminate between vitamin D2 and vitamin D3 and therefore only concentrate vitamin D3 in their visceral oils.
2. Alternatively, fish or zooplanktons that consume phytoplankton have a similar capacity as Paramecium to convert the side chain of vitamin D2 into the side chain of vitamin D3.
3. There is also a possibility the bioavailability of vitamin D2 is lower than for D3 in fish.
This article applies: Rosita Extra-Virgin Cod Liver Oil (EVCLO)