Beginning vitamin supplements: testing needed?

Before starting on recommended supplements such as zinc, magnesium, selenium, etc. would it be unwise to take up to the RDA of each mineral if testing is unavailable / denied / too expensive? I figure that since it's very difficult to overdose from dietary sources for most things you'd have to be going it some to take the RDA in pill / capsule form and get over and above from your diet.

For instance, I'm thinking of taking 10ug zinc, 200mg magnesium citrate and 50ug selenium. I think it's pretty conservative in terms of the quantities but testing is too expensive to see where my levels are prior to supplementation.

Is my thinking completely flawed?

9 Replies

  • hose, try magnesium glycinate instead of the citrate. You get better absorption from a chelated magnesium. Otherwise your idea of supplementing a little bit of the others as a sort of 'insurance policy' should be fine. You would not be overdoing it. I found taking 200 mcg selenium resulted in irritability after a week or so. We need about 64 micrograms per day.

    Check out the list of selenium containing foods (don't go for brazil nuts though) and find out if you are eating any of them and do a rough estimate of what you regularly consume. I recently read that even though fish contains selenium it is not as easily absorbed as selenium from meats.

  • Thanks, gabkad. I take mag cit as it's quite easily absorbed too, and in fact was recommended to me by another forum member. As long as it's not mag ox it should be okay :) Will check things on the selenium front. As I don't like brazil nuts at all (and they're tricky little buggers to shell anyway) I don't think avoiding them will be a problem...

  • The problem with that approach is that if you have a real deficiency, it's not going to help much. Especailly with B12. And you might have Pernicious Aneamia, so really best to test. Then, if it's around 350 or less, you would need about 7000 a day. The RDA often falls woefully short.

    Testing for magnesium is very expensive, and not of very much use, but 200 mg is a very conservative amount. I would have said more like 350. But most people are low on magnesium because the soil is depleted, so they Don't get much in food anymore.

    It really all dépends what you're planning to take. But Don't forget that certain things work together - magnesium and zinc work with vit D3 and vit K2. And then you have to make sure your zinc is balanced with copper at a ratio of 10:1. And the Bs all work together, so if you were taking vit B12, you would also need to a B complex.

    It's not just about deficiencies, it's also about balance.

  • Given that the RDA of magnesium for adult women is 320mg or so, and given that I personally have no absorption problems (that I know of), I don't think 200mg is conservative at all. I should be getting *some* magnesium from my diet and the 200mg should make up for any shortfall.

    I was talking rather more generally about the less tested things like selenium, zinc and magnesium rather than the ones my GP will willingly do like folate (a nice, healthy 12.74, range: over 4.8) and B12. I do take a B complex tablet as I've followed the advice on here. But it struck me that there was little advice out there for people who wanted to supplement but weren't sure whether they needed to. Hence the question of whether it was appropriate to supplement up to the RDA as it shouldn't do any harm.

  • Hose, I think RDA includes the x amount estimated to be obtained from diet.

  • Yes, but if you don't know how much you're actually getting it's probably not going to do much harm if you take a supplement that contains the whole RDA or thereabouts in one tablet / capsule. Unless your diet is seriously unbalanced. It's my understanding that with most vitamins and minerals it's hard to overdose from dietary sources but you need to be careful with oral supplements.

  • Hose, apparently soil depletion means many minerals like magnesium are low in food and, vitC is lacking in fruit and veg which are picked and stored before they are ripe. Supplementation is beneficial to address lack of vits/mins in food.

    I don't advocate supplementing B12, vitD, iron, calcium or iodine without testing first but I'm happy to supplement mag, zinc, and vitC.

  • But the question is, Clutter, how much to supplement? Up to the RDA? Above?

  • Hose, I take 375mg mag and 15mg zinc which are 100% RDA and 1,000mcg vitC which 1,250% of RDA. If I have a cold or virus I up vitC to 3,000mcg for the duration of the illness.

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