We don’t know. Since you asked, here’s the comment from one of the more recent meta-analyses to discuss dose in connection with all-cause mortality, Autier 2014:
Results of meta-analyses and pooled analyses consistently showed that supplementation could significantly reduce the risk of all-cause mortality, with relative risks ranging from 0·93 to 0·96 (table 4). Most trials included elderly women and a sizeable proportion of individuals were living in institutions. Decreases in risks of death were not associated with trial duration and baseline 25(OH)D concentration.^13^ Mortality reductions in trials that used doses of 10–20 μg per day of vitamin D seemed greater than were reductions noted with higher doses.^13,14^
13. Bjelakovic G, Gluud LL, Nikolova D, et al. “Vitamin D supplementation for prevention of mortality in adults”. Cochrane Database Syst Rev 2011; 7: CD007470. [2014 update]
1μg=40IU, so 10μg=400IU, 20μg=800IU, and 1250μg=5000IU.
Personally, I’m not sure I agree. The mechanistic theory and correlations do not predict that 400IU is ideal, it doesn’t seem enough to get blood serum levels of 25(OH)D to what seems optimal, and I don’t even read Rejnmark the same way: look at the Figure 3 forest plot. To me, this looks like after correcting for Smith’s use of D2 rather than D3 (D2 usually performs worse), that there are too few studies using higher doses to make any kind of claim (Table 1; almost all the daily studies use <=20μg), and the studies which we do have tend to point to higher being better within this restricted range of dosages.
That said, I cannot prove that 5k IU is equally or more effective, so if anyone is feeling risk-averse or dubious on that score, they should stick with 800IU doses.
People in the studies presumably don’t take it all in the morning. Do you have an estimate of how that affects the total effect? How much bigger would you estimate the effect to be when people take it in the morning?
I take it in the morning just because I found that taking it late at night harmed my sleep. I have no idea how much people taking it later in the day might reduce benefits by damaging sleep; I would guess that the elderly people usually enrolled in these trials would be taking it as part of their breakfast regimen of pills/prescriptions and so the underestimate of benefits is not that serious.
D is a fat-soluble vitamin that the body can store. It’s not like, say, the B vitamins which get washed out of your body pretty quickly. I don’t think when you take it makes any difference (though you might want to take it together with food that contains fat for better absorption).
What I meant is that blood levels of vitamin D are fairly stable and for the purposes of reduction in mortality it shouldn’t matter when in the day do you take it. However side-effects, e.g. affecting sleep, are possible and may be a good reason to take it at particular times.
I don’t think it’s clear at all the the purpose of the reduction of mortality is different than the purpose of sleep quality.
Vitamin D does do different things but I would estimate that a lot of the reduction of mortality is due to having a better immune system. Sleeping badly means a worse immune system.
I’ve gotten around to doing a cost-benefit analysis for vitamin D: http://www.gwern.net/Longevity#vitamin-d
Is it 5000IU per day?
We don’t know. Since you asked, here’s the comment from one of the more recent meta-analyses to discuss dose in connection with all-cause mortality, Autier 2014:
1μg=40IU, so 10μg=400IU, 20μg=800IU, and 1250μg=5000IU.
Personally, I’m not sure I agree. The mechanistic theory and correlations do not predict that 400IU is ideal, it doesn’t seem enough to get blood serum levels of 25(OH)D to what seems optimal, and I don’t even read Rejnmark the same way: look at the Figure 3 forest plot. To me, this looks like after correcting for Smith’s use of D2 rather than D3 (D2 usually performs worse), that there are too few studies using higher doses to make any kind of claim (Table 1; almost all the daily studies use <=20μg), and the studies which we do have tend to point to higher being better within this restricted range of dosages.
That said, I cannot prove that 5k IU is equally or more effective, so if anyone is feeling risk-averse or dubious on that score, they should stick with 800IU doses.
People in the studies presumably don’t take it all in the morning. Do you have an estimate of how that affects the total effect? How much bigger would you estimate the effect to be when people take it in the morning?
I take it in the morning just because I found that taking it late at night harmed my sleep. I have no idea how much people taking it later in the day might reduce benefits by damaging sleep; I would guess that the elderly people usually enrolled in these trials would be taking it as part of their breakfast regimen of pills/prescriptions and so the underestimate of benefits is not that serious.
D is a fat-soluble vitamin that the body can store. It’s not like, say, the B vitamins which get washed out of your body pretty quickly. I don’t think when you take it makes any difference (though you might want to take it together with food that contains fat for better absorption).
Multiple people such as gwern and Seth Roberts found that the timing makes a difference for them.
That’s true.
What I meant is that blood levels of vitamin D are fairly stable and for the purposes of reduction in mortality it shouldn’t matter when in the day do you take it. However side-effects, e.g. affecting sleep, are possible and may be a good reason to take it at particular times.
I don’t think it’s clear at all the the purpose of the reduction of mortality is different than the purpose of sleep quality.
Vitamin D does do different things but I would estimate that a lot of the reduction of mortality is due to having a better immune system. Sleeping badly means a worse immune system.
Thanks for posting that!
The key stats: expected life extension: 4 months; optimal starting age: 24.