One important negative effect of Vit D supplementation is that it reduces magnesium absorption (due to increasing calcium absorption, which is a magnesium antagonist).
It’s no big deal if you have sufficient magnesium, but for people who have low magnesium (which is common) it can make the problem worse.
This may explain the fatigue/lethargy at least one commenter here reported after taking fairly high-dose Vit. D supplements.
IMO this doesn’t mean you shouldn’t take them, but they should be taken with caution and ideally with clinical nutritional profile testing so magnesium or any other deficiencies can be addressed.
It’s no big deal if you have sufficient magnesium, but for people who have low magnesium (which is common) it can make the problem worse.
This may explain the fatigue/lethargy at least one commenter here reported after taking fairly high-dose Vit. D supplements.
IMO this doesn’t mean you shouldn’t take them, but they should be taken with caution and ideally with clinical nutritional profile testing so magnesium or any other deficiencies can be addressed.