Vitamin D3 Shown to Be Twice as Effective as Vit D2 in Cystic Fibrosis Patients (Both Work Great to Raise Vit D Levels)
In the study, “A randomized controlled trial of vitamin D replacement strategies in pediatric CF patients,” patients with cystic fibrosis (CF) were randomized to receive 50,000 IU of vitamin D2 twice a week or 50,000 IU of vitamin D3 once a week. The improvements after 2 months were from an average level of 23 ng/ml to an average of 34 ng/ml, with no significant difference between the two groups.
The authors used 30 ng/dl as the goal which is generally considered the lowest level of sufficiency for vitamin D. For optimal protection from vitamin D, I encourage you to aim for a level of 50-80 ng/ml. This study showed that taking D2 (which requires a prescription) is about half as effective as taking D3 that you can purchase over the counter. For D2 to be active, our bodies must convert it to D3. Why not just take the D3 that our body needs?
This also demonstrates that the dose of 50,000 D3 a week is about right to get your levels up. This is just over 7,000 IU Vitamin D3 a day. I tend to recommend 5000 IU a day. This study confirms previous work that would suggest a large weekly dose of vitamin D3 is effective and not excessive. I would recommend that most adults take 5,000 IU a day or 50,000 IU a week for about 6 months and then get your levels retested. If your vitamin D level is over 100 ng/dl stop your supplements for a month and restart at a dose perhaps half of what you were taking. Do not take more than 10,000 a day vitamin D3 unless you are closely monitoring your vitamin D levels at least monthly.
While this study was in children with CF, I suspect these findings can be generalized to all children and adults. In young children weighing less than 20 Kg (44 pounds) I would likely have used half the dose chosen in this study.
You can read the study by clicking here…