Calcium & magnesium supplement


I’m about to start with DIY Soylent, but I have some concerns in regards to calcium and magnesium.

I see that many of the high rated recipes use Now Foods 1000mg calcium and 500mg magnesium tablets. Now Foods states that the magnesium is 80% derived from oxide. My understanding is that magnesium oxide is rubbish and your body will only absorb perhaps 4% of it, meaning that 500mg of oxide would leave you with a massive deficiency.

It’s not clear to me whether the 500mg that Now Foods claims is how much your body will actually absorb, or the weight of the oxide in the tablet. I tend to think it’s the latter as it’s better for marketting, but this is just a guess.

Does anyone have any insight?


It’s magnesium citrate, not magnesium oxide. (Unless they make a second cal/mag supplement I’m unaware of.) As I understand it, magnesium citrate has a very high absorption rate.


This is the one I’m talking about:

Magnesium (from 80% Oxide, 10% Citrate, 10% Amino Acid Chelate) 500 mg 125%


Yeah, maybe switch to the powder?

I hadn’t seen anyone using the pills before.


There is no significant difference between the two, certainly not 4% absorption. You just need stomach acid to absorb the magnesium oxide. I really enjoyed your question and I wish I had a better answer but I’m under the impression that the DV and thereof rmg listed are what your body will absorb. (At least, what the USDA thinks it will because there are of course variables around vitamin absorption including above mentioned stomach acid and eating with foods)



I contacted the manufacturer and this is their response:

Yes, what your body absorbs are the listed values as these amounts are listed in its elemental amount.

So I guess I’ll just take their word for it and hope the tablets are suitable. Can’t be any worse than my current diet anyway even if they are wrong.


That’s great seanneko, thanks for your response, I was wondering about that great to hear a confirmation!