I want to tell the whole story of how I figured this out, but I will just cut to the data. Here is a graph of the amount of deep sleep. Its almost a year of data (Jul 30, 2011-Jul 8 2012).
You'll notice that the first night I had 54 minutes of deep sleep which is the highest amount of deep sleep in the time period. There was one other 50+ night and 9 40+ nights of deep sleep and they were all before Aug 27 2011 (the red line).
For perspective, according to Zeo, the average amount of deep sleep for males aged 30-39 is 59 minutes.
After the red line, my deep sleep cratered. It hovered in the 10-20 minute range. Except for one period from the middle of January to February, it stayed that way for almost a year.
I have done all kinds of tests in the year trying to improve my deep sleep and haven't experienced much success. So what was the red line? It was when I switched from 4000IU to 5000IU Vitamin D every day.
There has been research suggesting that a Vitamin D deficiency can cause sleep issues. In March of 2011 (before I switched to 5000IU) I was tested at 44ng/mL...so no reason to think I was deficient at any point in the sleep tracking.
In the alternative health blog world, there is a lot of discussion that Vitamin D timing can affect sleep quality. In most of 2011, I took it at night. Most of 2012, I took it in the morning. You can see from the graph it didn't make much of a difference.
I haven't seen anything before that suggests too much Vitamin D (at any time) can cause sleep issues. Also, to be clear, I had my Vitamin D level tested in December (after 4 months of 5000IU). It was 89.5 ng/mL - well under the level considered excessive (100 ng/mL).
But I still think too much Vitamin D is what caused the decrease in deep sleep.
I made this determination on July 8 (the other red line). I stopped taking any Vitamin D and put on suntan lotion when I went outside. The halflife of Vitamin D in the body is a month. So what happened a month after I stopped?
My deep sleep went way up. That's what happened. I have had multiple nights of 50+ minutes of deep sleep and my first ever 60+ minutes of deep sleep. I have gotten more deep sleep in the past 11 nights than the last 33 nights while I was taking Vitamin D. Pretty awesome.
I went and had my blood tested the first time my sleep broke 50 minutes. It was 55.5 ng/mL.
I'd love to hear any comments/questions. I think a lot of people in the paleo/alternative health world are taking a lot of Vitamin D so I think it would be great
EDIT: I updated the post to go into a little more detail about what time of day I took Vitamin D.