Vitamin D & Myopia - Associational or Causal in myopia prevention?

This was a simple question I had the other day.
As there is alot of talk about getting outside and the importance of getting outside.
But why? Why is getting outside the best thing for myopia prevention and reversal.
Obv. using distance vision.
Obv. getting natural light.
But what are the elements / factors outside that cause myopia to reduce or reverse.

So firstly. The associational evidence of going outside and myopia prevention is CLEAR. Go outside!
Thats what all the literature says.
What I can’t find, I have to say I didn’t look very hard, is research showing what causes preention and reversal.

My first attempt. Look at Vitamin D. There’s alot of talk atm in other threads about the benefits of Vitamin D. Its awesome. Cures everything etc.

My question: Is vitamin D causal in myopia reversal?
The answer atm: Maybe. At the moment No.

Below are the papers I had a skim through with quick notes. I’ve separated them into causal and associational research.


Taken as a whole, these observations suggest the human eye may be profoundly dependent upon adequate vitamin D availability for many critical optical, structural, and physiologic properties.

Associational with little to no causal

Increased UVB exposure was associated with reduced myopia…We found no convincing evidence for a direct role of vitamin D in myopia risk

Total vitamin D and D3 were biomarkers for time spent outdoors, however there was no evidence they were independently associated with future myopia

Lower 25(OH)D concentration in serum was associated with longer AL and a higher risk of myopia in these young children. This effect appeared independent of outdoor exposure and may suggest a more direct role for 25(OH)D in myopia pathogenesis

Myopia is associated with lower vitamin D status in young adults

The hypothesis that time outdoors might create differences in vitamin D could not be evaluated fully…though myopes appear to have lower average blood levels of vitamin D than non-myopes.

Lower 25(OH)D is associated with increased risk of myopia; the lack of a genetic association suggests that 25(OH)D level may be acting as a proxy for time outdoors.

I have thought about this as well. My outdoor time has not changed in the past 30 years (a lot of it) but my vit D levels when I first tested 5 years ago were pretty low. So in my case vit D was not a biomarker for outdoor time. This was probably on account of age and obesity. I had not yet discovered EM, so was not measuring eyesight, so cannot tell if my eyesight improved as a result of higher vit D levels during the past 5 years. I can’t even tell if it improved as a result of more outdoor time compared to when I lived in the dreary Netherlands the 5 years before my 30 years in France. These were also the 5 years when I had to earn my living at a screen. When I lived in southern Africa I had lots of outdoor time and exposure to sun, and as a teacher and later a lecturer, did not spend whole working days glued to a screen. It is a pity that I knew so little about myopia that I did not pay attention to my diopters, although I did not go for regular eye checks and rarely changed my glasses…

In a similar bent, Dr. Ken Berry (the plain man’s guide to keto/carnivore diets) has reported many of his patients improving eyesight on a ketogenic diet. I had always assumed this was on account of lower insulin levels. But it could also be because a carnivore diet increases the level of vit D from food. There were 3 times when I had to reduce my supplement levels - when I doubled my magnesium intake, when I had been on the carnivore diet for a year and lost 10kg of surplus fat (two factors in play), and now because I have overdosed this summer as a precaution against covid. I have now halved the dose, but will check again in April.

Vit D3 (actually a hormone) plays so many critical roles in the body that I would not be surprised at all if it plays a role in eyesight as well. But it would be foolish to discount the benefits of sunlight quite apart from the D3 aspect.

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yeh. I think you’re right.
I also watched that COVID Vit D video you posted.
I was overwhelmed by how important it is and how its is important for so many of the body’s processes.
Even if it isn’t causal in eye development theres more than enough other reasons to get outside and get some D!

Interesting about keto and vitamin D. Didn’t think of that connection. I’m doing keto atm. C’mon eye improvement!

This depends on what kind of keto. Vegetarian or vegan keto (if that is even possible) is unlikely to increase vitamin D intake from food. I have nothing against vegetarians or vegans, but would recommend they consider vit D supplements in winter.

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Oh that was crazy in the COVID vitamin D video.
They mentioned that the average american spends 7% of their time outdoors each day! How crazy is that!!! Thats about 1.5 hours!

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Honestly this sounds high for the vast majority of people I know. I try to get out as much as possible (though winter is much harder) and that isn’t even a new thing since starting EM. But most people I know rarely get much more time outdoors than it takes to walk to and from their cars… Summer is a bit better but still that 1.5 hours is like once a week in many cases, and because the lawn needs mowing…

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:joy: Australian’s are probably not too far off! Well at least Aussies in the city.

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I don’t think this 7% is what EM calls outdoor time.
I think the American 7% means “outside of buildings” (home or office), so the time spent commuting and shopping are included. No?
Aussies must be different with the beach bbq time :smiley:

There are so many studies showing correlation between low vit D levels and illnesses. Still I suspect the correlation is more from the fact that ill / sick people will sooner stay indoors…
So I think low vit D with myopia is also related to increased screen time indoors.

For me the EM need for outdoor is definitely related to distance vision. Some people live their lives in a way that they never have to look further than 20 meters (and I’ve been generous here!), not even in their full prescription. They order food on a screen (not reading from a board, or take a screenshot and zoom in), when it comes to departure times they walk closer to anything that is outside of clear vision or look it up online, navigating is by GPS and not by reading street names, they don’t read presentations on a big screen in a meeting room, but follow them on their laptop screens, etc.
Latest below -1.0D one realises that the house is not big enough for a real blur challenge anymore.

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Great points.

In regards to the time spent outdoors it was mentioned in this video that Ursa linked. I’m not sure how the time was cut up exactly.

Outdoor distance vision is obviously a causal factor for any EMer. No clinical studies to back this claim up, only associational studies.

There is a good animal model study testing violet light as a causal factor. Results are promising. I’ve included the study in the EM Wiki.

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