It goes without saying that the best source of nutrients is food. Whole food contains the correct combination of elements in ideal ratios for optimal absorption and utilization by the body. With that said, poor diets and depleted topsoil by modern farming practices have made it nearly impossible to get all the micronutrients we need from food alone.
The prevalence of micronutrient deficiencies was demonstrated by a study published in the Journal of the International Society of Sports Nutrition. In the study, the researcher analyzed four popular diet plans to determine whether or not they met the RDI (Recommended Daily Intake) of 27 essential micronutrients. The findings showed that even the most nutrient dense diet required 18,000 calories a day to achieve sufficiency in all 27 micronutrients. Additionally, it was found that on average amongst all four diet plans that whole food alone would only provide 12 of the 27 essential micronutrients, resulting in an average deficiency of 56%. The researcher goes on to say - "It was found that 100% sufficiency was possible for all 27 essential micronutrients only when daily calorie intake requirement averaged 27,575 calories. This extreme calorie intake requirement is, in the opinion of this researcher, impossible and/or medically unwise to obtain and/or sustain." The takeaway - unless you're eating approximately 20,000 calories a day (or supplementing), you're likely deficient in several micronutrients.
"Looking at all the evidence, the potential health benefits of taking a standard daily multivitamin seem to outweigh the potential risks for most people."
- Harvard School of Public Health
In the past year I've come to greatly respect a number of prominent health "bloggers" such as Chris Kresser, Paul Jaminet and Dave Asprey. Taking their advice has done more to improve my health than all of the doctors I've seen combined. Surprisingly, almost all of them recommend not taking a multivitamin. Their two main reasons - 1) multivitamins typically contain low quality ingredients and 2) they contain too much of some nutrients and not enough of others. While these are certainly valid criticisms, the evidence still shows that the average person can benefit from taking a high quality multivitamin. Just remember - a multivitamin should never be used as the primary source of micronutrients, instead, it should only be used to fill in nutritional gaps.
If you have decided to begin taking a multivitamin or if you already take one, be sure it's of high quality. The easiest way I have found to determine the quality of a multivitamin is by looking at the forms provided of vitamin B12 and B9 (folate). High quality multivitamins will contain the methylcobalamin form of B12 and ideally will contain folate (or 5-MTHF / l-methylfolate) instead of folic acid.
Below is the best overall multivitamin I have found so far. I recommend taking 3 capsules a day (one with each meal) vs the recommended 6. This brings the monthly cost down while still providing enough nutrients to achieve micronutrient sufficiency for most people.