Anybody knows of any other projects out there quantifying the sun effect on the body?
The marketing is misleading: The Violet does not “measure sun-generated vitamin D”; it measures UV exposure, and then makes a guess based on your skin type etc. There are several comparable products that are either shipping already (e.g. the Netatmo June) or close to shipping (e.g. the SunSprite), so I’m not sure why I’d want to back this project.
Isn’t that what all trackers do anyway? Even activity ones like Fitbit and Misfit and sleep ones. They all measure indirectly things. The June does not estimate vitamin D. Violet does not track mood and Sunsprite is very abstract to me. They use “GoodLux” units. I need units I can understand. I guess I need a combination of several of these trackers.
Sure, but there is a difference in the level of indirection, and in the the amount of assumptions made. Estimating vitamin D levels from sun exposure is like inferring your body weight from your step count…
Real units make it possible to compare data across devices or with “gold standard” measurements, but aren’t strictly necessary in order to correlate data.
ejain,
It’s just science. And apparently it has already been studied and is in the public domain: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256341. There are not very many assumptions made, only body characteristics and Geo-locations taken into account. Inferring Vitamin D generated by the skin from UV dose does not seem to be really different from converting steps to calories. Actually, in my case, I have to adjust the calories number because I have a very fast metabolism and my Fitbit and Misfit numbers do not make sense. All these trackers are based on an average human body anyway.
And
Right: Converting steps to calories doesn’t make much sense, either 
If you want to track calories, you should use a BodyMedia FIT, not a Fitbit… Likewise, blood tests are still the only way to check your vitamin D levels. As a Quantified Selfer, I don’t care how much vitamin D an “average” person would have produced on a given day–I want to know how my vitamin D levels changed!
I agree. Thanks for the feedback!
How would consumed vitamin d be accounted for?
Beware that exposure to sunlight doesn’t guarantee Vitamin D absorption.
This study on 93 Hawaiians around 24yo exposed to sunlight for 29h/week shows that,
Using a cutpoint of 30 ng/ml, 51% of this population had low vitamin D status.