Honestly you don't even need to know the recommended number. In many countries you can get tested for free, and if that's not the case for you, getting tested usually costs in the ballpark of a box vitamin D supplements. Measure and only then supplement, then measure again later. You don't need to fly blind.
A year's worth of daily 5000 IU (125 mcg) Vitamin D supplements costs approximately $15, so you could also just supplement.
Strangely the protective effects of vitamin d for heart disease appear NOT to be achieved through supplements. (Though the protective effects for cancer ARE)
I’m going to go out on a limb and guess that people who get outside a lot protect their health through both natural vitamin D from UV light exposure and cardiovascular exercise.
This approach doesn't make much sense to me. Why supplement something when you don't even know that you need it? You could make the same argument about any and every supplement and eat the whole alphabet soup every day, but that's just putting extra strain on your body.
Well, if a study finds that nearly everyone of your skin color at your latitude is deficient, you can make an educated guess.
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