A couple of earlier studies showed the D2 didn't cause the levels in the Blood to be maintained as long, however they used 50000 IU. That's a massive dose. A recient study shows that 1000IU of D2 taken daily, instead of 50000 once a week (50 x as much), was just as effective as D3. Show your Dr this study:
file:///C:/Documents%20and%20Settings/Dell/My%20Documents/Health%20&%20Medicine/Nutrition/Vitamins/Vitamin%20D2%20Is%20as%20Effective%20as%20Vitamin%20D3%20in%20Maintaining%20Circulating%20Concentrations%20of%2025-Hydroxyvitamin%20D.htm
D2, ergocalciferol is plant derived and does the same thing as D3, Calecalciferol. Both have to coverted in the liver, to produce 25, dihyoxycalciferol and that is coverted in the kidneys to produce the active form, 1,25, dihyoxycalciferol. If there is any problems with the liver or kidneys it will not happen properly.
If D2 does not maintain D levels in the blood, why. Is it because the body is using more, or can it get rid of any excess more better? I think these are questions to be answered.
Ian Ridgeway ND
www.alnaturalhealth.com