I have only been taking a multivitamin plus extra vitamin D until recently. Last week I bought a bottle of magnesium citrate at Costco: https://www.costco.ca/webber-naturals-magnesium-citrate-150-mg---300-capsules.product.100107807.html I did so more on a whim than anything else after recently reading an article on the mineral. The recommendation on the bottle is to take one to three 150mg capsules a day, but I'm only taking one for the time being, since my multivitamin has 125mgs of magnesium oxide. That brings me to 275 mgs all in from supplementation, which is close enough to the UL of 350mgs for typical supplemental consumption as noted in the article I linked. Who knows, though. I might go crazy and take a second capsule, bringing me up to 425mgs of supplemental magnesium, which is 75mgs above the generic UL. I live for danger.
Magnesium Oxide is shit, virtually no benefit. Citrate is better and as TreeFrogg suggested there are better like: ChelatedMagnesiumGlycinate Benefits The benefits of taking a chelatedMagnesiumGlycinate supplement is where Glycine comes in as an excellent pH buffer. When chelating Magnesium with Glycine, the rise in pH at tight junctions is largely reduced. This leads to significantly improved Magnesium absorption. Magnesium Oxide vs Magnesium Citrate Supplements Magnesium oxide contains the highest amount of elemental magnesium (about 60%) of all magnesium supplement types. However, this doesn’t directly translate to more magnesium absorbed in the body. In fact, magnesium oxide is poorly absorbed by the body. It’s though that around 4% of its elemental magnesium is absorbed, equivalent to about 9.5 mg out of a 400 mg tablet (with 60% elemental magnesium) (16). On the other hand, magnesium citrate is much better absorbed by the body than magnesium oxide. It appears to have a bioavailability of 25-30% (17). For this reason magnesium citrate is the most common type of magnesium supplementation and is the recommended choice for most issues and deficiencies. Magnesium Citrate and Oxide: Benefits, Dosage and Side Effects | Diet vs Disease
I don't want to get too much into the weeds here. I figure I may benefit from some magnesium supplementation because I drink a LOT of fluids during the day and may lose some mineral content as a result. I don't need its laxative properties, but I don't want to become inadvertently dependent on magnesium either, if that is one of its effects. Plus, my diet is high in several magnesium-rich foods, so I figure I should be okay with the supplemental dosage I mentioned in my previous post. The Internet is rife with rabbit holes. I figure I should choose wisely and sparingly.
You're right, it's easy to overthink these things, but it's highly unlikely you'll ever get anywhere near over saturation. It's unlikely you or most people are deficient to the degree I was several years ago.
Just to assuage concerns about going above "tolerable" dosages for magnesium, I will add in that one of the factors that keeps magnesium relatively safe is that there is a feedback loop between the serum level or tissue levels and the intestine such that when adequate levels are reached the intestine reduces absorption. It's complicated, the kidneys and bone are involved as well. So in some instances the intestine just shuts down the un-needed absorption so the serum level does not go up. But the body also stores manesium in the bones so the human body also does a scan to see what the bone level is and might reroute some magnesium there without raising serum level. And then take the magnesium back out of the bones when it is needed. People who get into trouble with magnesium are usually elderly people drinking Milk of Magnesia by the barrel-load and it has lots of magnesium in it, lots. Otherwise, magnesium is good stuff and not to be feared at all. It is one of the major electrolytes and so needs to be at good levels, and it is used to make over 500 enzymes in the human body. It increases delta waves in your brain which are needed for deep sleep and growth hormone is created is released in deep sleep. And elderly people need it to increase their brain delta waves to restore their ability to sleep through the night and it therefore saves many people from taking nasty sleep drugs. It's all good. Don't leave home without it.