They can be, but the oral absorption pathways are complicated. You need to be sufficient in other vitamins, I can’t remember which, in order to absorb vitamin D from your food.

Generally it’s recommended that sun > supplements, for a few reasons. But if you can’t get some sunlight supplements are not a bad choice at all.

> sun > supplements This is interesting, a recent article/study mentioned this, it appears that there is a link between sunlight and lower blood pressure in dialysis patients among other benefits. It would also explain why death rates/severe covid-19 in warmer climates is lower than colder climates.

https://www.outsideonline.com/2410015/sun-exposure-blood-pre...

Ecuador (literally on the equator) being the catastrophic and tragic exception.

Sunlight involves going outside, which we know is good for your health (barring pollution, of course).

Also, and probably the direct mechanism of action, sun exposure doesn’t just produce vitamin d. It also increases nitric oxide levels which should reduce BP

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People are taking more walks and runs in my neighborhood than ever before. Social distancing != hiding indoors.

Patios and yards exist, you know.

Mine doesn't.

For many people diet/sunlight is insufficient - there's a host of cofactors and things that probably play a role in this. I'm not too sure on just how effective supplements are but I've personally used them to raise my serum D levels with success.