Dealing with even the most basic supplements like multivitamins can be frustrating, because it is difficult to find scientific basis for what you should and shouldn’t be taking. And useful consumer analyses are hard to find, and often disappointingly simplistic when you find them.
This raises the obvious question of if you should even bother with supplements at all. I would say yes, but for most people the list of worthwhile supplements is very short.
Number one at the top of the list is an Omega-3 EPA/DHA supplement, typically in the form of fish oil capsules. The great thing about this is that there is a ton of hard science research on the subject, and it is all overwhelmingly positive for reducing the risk of a wide variety of health issues. A complete rundown of the benefits, recommended doses, and so forth are listed here:
You may also find supplements that are a mix of Omega-3, 6 and 9 fatty acids. While there is nothing wrong with these per se, most diets in the developed world already have plenty of Omega-6 and Omega-9 fatty acids, so supplementing those is probably not going to do much good. In general, you are better off taking a stronger Omega-3 supplement, and letting the others take care of themselves.
Next on the list are multivitamins. Although much more popular than Omega-3 supplements, the science behind them is actually much sketchier. Studies of individual vitamins exist, of course, but they tend to be studies of vitamin X in isolation, and even the most primitive multivitamin product usually has a couple dozen active ingredients. More to the point, as a consumer you need to know the actual efficacy of a specific product, not the theoretical performance of the individual ingredients in isolation.
So should you even bother with taking one? Probably. Most people do not have a sufficiently varied diet to get all of the nutrients their body needs for optimum health. In fact, most people’s diets are bad enough that they are probably outright deficient in some nutrients. Anecdotally, many people find themselves getting sick much less frequently once they start taking a multivitamin. Multivitamins are not a substitute for trying to eat as well as you can, but are a sensible way to try to make up for any inadvertent nutritional gaps in your diet.
The starting point for most people when judging nutritional content is the US Food & Drug Administration’s Recommended Daily Allowance (RDA). This is because vitamin and food labels showing a “% daily value” are using numbers based on the RDA. However, the RDA has some real limitations. The most important one is that it is not an optimal value, but rather a minimum value to prevent short-term malnutrition. RDAs also tend to lag behind current research. For instance, many new nutrients that appear to have major health benefits (such as lycopene) aren’t included in the RDA.
Most over-the-counter multivitamins are going to give you a flat 100% RDA of all the major vitamins and minerals. For most people this is probably fine, although there are some points to consider:
1) Women will want supplements with more folic acid and iron. Folic acid prevents birth defects, and women need 50% more iron than men, on average. Women are also much more prone to iron deficiency anemia than men.
2) Men will want supplements without iron. Men need less iron than women generally, and excess iron intake is associated with health problems in men.
3) As noted, 100% of the RDA is not really an optimum value.
The flipside to the “RDA is not enough” argument is that there is no convenient alternative to it, just a series of arguments over what the optimum amount should be, making it hard to decide what you should and shouldn’t take. So while it is hard to hurt yourself by taking even large doses of most vitamins (only vitamin D and the retinol form of vitamin A have significant toxicity), it is also hard to know if you’re doing yourself much good, either.
So what do I recommend? It depends. Most people probably just want to make sure they don’t have any obvious dietary deficiencies, and so would be well served by simply taking a basic multivitamin like Centrum. Pick your brands based on the ones that pass www.consumerlab.com testing for content & purity and leave it at that (their test result summaries are free, or you can pay a fee to see their complete test write-ups).
For people who want optimal nutrition and are willing to pay for it to the tune of about $38/month, I’d suggest looking into AOR's Ortho-Core.
AOR seems to be alone among the premium multivitamin makers in that it actually makes a credible attempt to back up its formulation scientifically. They don’t include a lot of unproven herbal ingredients, and keep their doses of retinol and D well below the FDA’s tolerable upper intake levels (UL) for safety. It is iron-free, so women will probably want to add a separate iron supplement, but it already contains a good amount of folic acid (more than the RDA, but well below the UL).
You should take the above article with a grain of salt, just like any other manufacturer’s statements, but AOR seems to do a much better job backing its formulation decisions than any other vitamin maker that I know of. In particular, I appreciate the fact that they cite real scientific studies from credible outside sources. If you’re interested in Ortho-Core, the best price I’ve found for it online for US customers is agoodvitamin.com (order 2 bottles and you get free shipping).
I don't have kind of interest in AOR or agoodvitamin.com, incidentally; I'm just a consumer who likes what they have to offer.