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Show HN: I built a daily sunlight tracker

(www.lumehealth.io)
45 points vickipow | 1 comments | 26 Jun 25 23:28 UTC | HN request time: 0.217s | source

I kept trying to explain how important outdoor light is and how most people aren’t getting enough. Eventually I figured that showing is more effective than telling.

So we built a free app that uses your Apple Watch or iPhone to automatically track your light exposure throughout the day.

It tells you if you’re getting enough, shows you how consistent you are, and rewards habits that support hormone balance.

It's in beta on TestFlight, let me know what you think!

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Fraaaank ◴[30 Jun 25 13:04 UTC] No.44422805[source]▶
>how most people aren’t getting enough

What are you basing this on? What counts as 'enough'? And how are you tracking light exposure?

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snarf21 ◴[30 Jun 25 13:15 UTC] No.44422907[source]▶
There are countless studies that billions of people are Vitamin D deficient. Our bodies are designed to get most of that from the sun. Lots of people never even leave their house on a given day.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3068797/

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Fraaaank ◴[30 Jun 25 13:43 UTC] No.44423182[source]▶
I should've been more specific. The study you link states that 'To prevent vitamin D deficiency, one should spend 15 to 20 minutes daily in the sunshine with 40% of the skin surface exposed.'. The screenshot on lume health shows a goal of 120 minutes.

Moreover, sun exposure is not by definition 'healthy'. Spending two hours in the sun at noon in the middle of summer does more harm than good.

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1. adolph ◴[30 Jun 25 17:37 UTC] No.44425923[source]▶
> The study you link states that 'To prevent vitamin D deficiency, one should spend 15 to 20 minutes daily in the sunshine with 40% of the skin surface exposed.'. The screenshot on lume health shows a goal of 120 minutes.

Linearly it follows that if one wears clothes that cover more than 40% of lit skin, then the duration would be adjusted to match the total skin-area/time.

If one start with 1.85 m^2 body surface area, 40% of that is .72 m^2. If clothing covers 50% of a human and the human's shape and hair occludes half of that remaining, you have .46 m^2 available for sunlight. .72 m^2 * 20 is 14.4 m^2/min. divided by .46 m^2 it seems that 31.3 min would be the daily amount.

This seems much less than lume health's goal of 120 min. Otoh, given there is less opportunity for get to 14.4 m^2/min daily (I'm looking outside at a nice rainstorm), maybe the 120 min has some catchup factor?