Dear Erik,
I think it is safe to say that vitamin D, as a fat-soluble vitamin, will distribute into the adipose tissue. This is supported by data that indicate that a high BMI is correlated with low plasma 25 OH vitamin D when the data are corrected for intake and life style (sun exposure). Additionally, vitamin D supplementation in high BMI people leads to a lower increase in plasma vitamin D then in low-BMI people (see PMID: 24215874). Thus, If you fast (long enough to decrease your body mass) this will lead to increases in plasma vitamin D. This has actually also been demonstrated before (see PMID: 21613554).
Best wishes
Jürgen
Dear Erik,
I think it is safe to say that vitamin D, as a fat-soluble vitamin, will distribute into the adipose tissue. This is supported by data that indicate that a high BMI is correlated with low plasma 25 OH vitamin D when the data are corrected for intake and life style (sun exposure). Additionally, vitamin D supplementation in high BMI people leads to a lower increase in plasma vitamin D then in low-BMI people (see PMID: 24215874). Thus, If you fast (long enough to decrease your body mass) this will lead to increases in plasma vitamin D. This has actually also been demonstrated before (see PMID: 21613554).
Best wishes
Jürgen
Thanks for the reply, Jürgen, and I agree with your comment. I think also they observe it after bariatric weight loss. If you are interested in the subject, I found this study (PMID 25702786) informative. They also assess regression to the mean.
However, I was actually thinking more in direction of study design and measurement error, i.e. blood pressure measurement. If repeated measurements of 25OHD are taken from the same person, would the concentrations differ if the first sample was taken in the morning (after 8-12 hours of fasting or lets say 24 hours) and the second measurement in the evening or some other time when the person was not fasting?
Hello. Regarding the 2nd question, a considerable circadian rhythm has been reported for 1,25 and 25OHD, the 1alpha-hydroxylase, PTH, FGF23 and the minerals themselves. So it's 2 variables. Both fasting duration and timing of blood sampling will likely influence the 25OH measurement. I'd say, one should rather try to do the follow-up measurement on the following non-fasting day at the exact same time to measure the fasting effect and rule out any circadian effect.
http://www.ncbi.nlm.nih.gov/pubmed/25788054
http://www.ncbi.nlm.nih.gov/pubmed/11980618
http://www.ncbi.nlm.nih.gov/pubmed/7095152
http://www.ncbi.nlm.nih.gov/pubmed/465066
hello
this paper may be useful.
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2265.2005.02288.x/full
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