Well if you really don't mind perhaps I could comment on Mary Jo's post
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2008 Vit. D levels were 32. she took 4000 i.u.' reached 62 and lives in Sheboygan,
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This is a fairly typical response and 62 is a reasonable level for someone with a chronic condition or a previous BC diagnosis to aim for.
Sheboygan, is around latitude 43 and will have a vitamin D3 low winter so while 4000iu is fine for summer maybe Mary Jo could think about raising intake to 6000iu from Oct through to the end of Feb.
I mentioned Vieth's new paper a couple of posts back and he raises the idea that fluctuations in Vitamin D status may allow periods for an imbalance to occur
When 25(OH)D declines, the ratio of 1-hydroxylase/24-hydroxylase [CYP24] must increase to maintain tissue 1,25(OH)2D at its set-point level. The mechanisms that regulate this paracrine metabolism are poorly understood. I propose that delay in cellular adaptation, or lag time, in response to fluctuating 25(OH)D concentrations can explain why higher 25(OH)D in regions at high latitude or with low environmental ultraviolet light can be associated with the greater risks reported for prostate and pancreatic cancers.
What happens in prostate cancer also often occurs in BC and We see here
Vitamin D-24-hydroxylase[CYP24] in benign and malignant breast tissue and cell lines.
Nothing is ever simple and there that other factors are also concerned in the regulation of CYP24
Human CYP24 catalyzing the inactivation of calcitriol is post-transcriptionally regulated by miR-125b.
So bear in mind this is very recent information, Vieth's work is only at the HYPOTHESIS stage, but most here don't have the luxury of waiting xx years for it to be confirmed.
If Vieth is right that falling levels of 25(OH)D can lead to a temporary excess of CYP24 the simple answer is to keep 25(OH)D levels high and stable. There isn't a great deal of cost involved nor is there any risk as we know 10,000iu/daily is safe even where ample sun exposure is also present.
However Dr Davis working in Wisconsin find his female patients generally require 5000iu/daily to stay around the 60ng level so if Mary Jo took 4000iu summer and 6000iu winter she would average 5000iu/d over the year and has a greater chance of preventing the winter 25(OH)D dip which you see is typical for UK adults.
This new information should encourage people to take moderate (equivalent to daily full body sun exposure) amounts of Vitamin D DAILY rather than larger amounts monthly or even larger amounts 2/3 monthly.
The graph Dr Davis reproduces here shows using Vitamin D2 produces a greater swing in 25(OH)D (deeper falls in level) so to achieve a steady state ONLY CHOLECALCIFEROL Vitamin D3 should ever be used, even if you can get D2 prescribed from your doctor it's not worth using it.
Rembering that to prevent an excess of CYP24 the aim is to prevent sudden changes in 25(OH)d those booking a winter holiday in the tropics may want to to plan ahead. Consider possibly increasing vitamin D3 (+2000iu) intake over a couple of the weeks prior to departure, NOT taking D3 while you are in the tropics sunbathing on the beach, BUT restarting D3 supplementation before the flight home and also using an effective amount (5000~8000iu) in the weeks after your winter break.
Fish oil was mentioned earlier and although fish oil works synergisticly with D3 it's only cod liver oil that comes with SOME (usually just 200~400iu) vitamin d3. Cod liver oil also contains vitamin A and a little NATURAL vitamin A works in conjunction with D3 but too much synthetic vitamin A is antagonistic to the action of D3 so you have to be certain that the Vit A in your CLO hasn't been standardised.
UK readers may need reminding we live 600miles further North than Mary Jo. Our UK/EU milk is NOT vitamin d fortified, Most of our breakfast cereals are NOT vit d fortified. So because we don't have the same background level from UVB or even from diet our daily intakes need to be higher to achieve the same response that Mary Jo has achieved also the additional amount required to prevent levels dipping overwinter will need to be started September and go through to March rather than Oct~Feb.
Only regular
25(OH)D testing though will provide the certainty that you have got your 25(OH)D around 60ng 150nmol/l and understand what your summer/winter intakes need to be to keep steady around that level.