I started taking multivitamins somewhat recently to get additional iron, vitamin B12, and vitamin D (I'm vegan).
In men iron more iron is generally associated with worse health outcomes, so why would you do that? (see Tim Ferriss The Four Hour body for more discussion where he recommends blood donations to reduce the iron content of the blood).
Taking these supplements was partially informed by this post, though I have been taking creatine on and off for quite a while.
The post doesn't mention iron at all, so why?
Generally, we find that in people who eat a normal diet (some poor people don't count in that category) multivitamin supplement don't improve health outcomes. While there's a case for vegan's supplementing B12 (and for everyone who doesn't spend multiple hours outside every day with a lot of uncovered skin surface to take Vitamin D), there's no evidence that broader multivitamins are useful.
Aside from that multivitamins usually don't contain Vitamin D in amounts that the people who recommend Vitamin D usually recommend.
If we assume that some of the vitamins are indeed healthy to supplement that leads to the hypothesis that others are harmful.
One key post that layed out the thesis of chromium/manganese being unhealthy was Most multivitamins have these 2 toxic minerals in them and there's a good chance that's the source for Eliezer believing that those things are unhealthy.
I'm so surprised by the complaint about iodine in that link that it makes it hard to take the rest seriously. Is this guy not a crank?
The post doesn't mention iron at all, so why?
Iron deficiency is more common without animal sources. Given my diet, I think being iron deficient is considerably more likely than having too much iron. I haven't done a blood test. I also don't have any strong intuition if it is better to have too much or too little iron (my prior would be that too little is worse).
A related question, should manganese rich foods also be avoided? For example, just a few slices of whole wheat bread have a similar manganese content to a typical supplement (100% daily value or ...
Too much calcium can be harmful, although that one doesn't have much. Harm from calcium can probably be avoided by getting enough vitamin K2 from fermented foods or a supplement. You're probably not getting K2 from the multivitamin.
Potassium deficiencies are common (but likely less so in vegans). Supplements aren't allowed to have much potassium, but it's easy to get potassium chloride and use that in place of salt.
In Inadequate Equilibria Eliezer mentions that multivitamins may cause harm via excess manganese
I started taking multivitamins somewhat recently to get additional iron, vitamin B12, and vitamin D (I'm vegan). Specifically I am taking this multivitamin. I also take creatine. Taking these supplements was partially informed by this post, though I have been taking creatine on and off for quite a while.
I picked multivitamins instead of individual supplements because it was cheaper and more convenient. I also thought that covering additional vitamin/minerals would almost certainly be either neutral or slightly positive. However I now place somewhat more probability in the these additional vitamins/minerals being harmful in net (via excess vitamin A, manganese, or similar). How concerned should I be?
At the moment, I think the additional manganese I am getting from this multivitamin (2.3 mg or 100% DV) is probably not harmful. Precisely, I estimate that the probability of taking the supplement causing modest negative health effects (for instance, reducing expected IQ by >0.5 points or reducing expected life span by >1 month) is 20%. This is primarily based on noting that many common foods have high manganese content and not seeing any arguments against this dosage of manganese after briefly googling. I have seen arguments against higher dosages of manganese in supplements; this may be what Eliezer is discussing.
More generally beyond just manganese, how should the expected value of the 'unknown unknowns' of taking a multivitamin be estimated? It isn't immediately clear to me what the sign would be. I am currently leaning toward slightly negative expected value due to general principles about side effects.
Additionally, are there any other supplement I should be taking? I think my diet is generally healthy; however, I may get too little protein occasionally.
(edit: used to be 'less than 20%', but this wasn't what I meant)