In my opinion that 100 mg x 3 daily is not much....your body just never really get 300mg ,not even close.
Typical magnesium absorption involves:
40% of magnesium intake absorbed in the small intestine
5% absorbed in the large intestine
55% leaving the body as waste
Depending on the type of magnesium ingested and the magnesium status of the individual, these figures can be higher or lower. Studies have shown overall absorption of magnesium in some individuals as low as 20%.3 6
And certain forms of magnesium supplements, such as magnesium oxide, may have an absorbable magnesium potency as low as 4%.7 8
Try to switch to magnesium oil to see how if can effect, i am not saying you are magnesium deficient, but the possibility that you might be is real.
There is a major problem with the world we now live and magnesium, as in ancient times soil have had more magnesium than now,specially when all that fertilizers come to business it started to make the soil less nutrient. Then enter, sugar, alcohol, coffee,too much calcium, medicins etc ....and the fact that humans have higher natural requirement to magnesium than we now got becouse the evolution, it is written in our code to work better with higher amounts of magnesium..
And the problem is also that when you reach to a point where you have a real defiency of magnesium it is not easy or fast to correct it if take only orally magnesium, as it seems like humans gut are not build to work that it could absorb big " therapeutic amounts" of magnesium when using suplements.....it just dont work...try to take 800-1000mg orally and soon you end up with diarrhea even when your body would really badly need magnesium....so the gut is not made for this kind of operation at all.
so there you have it, world has change, but we have not..
Thats why magnesium oil, as it will pass the gut problem and becouse it is fast, can also use several grams dayly doses...i have used 3-4 grams/day when i put it .