There have been studies done on mutlivitamins. The data is relatively conclusive: They don’t work as well as when they come from whole food. Most multi-vitamins are made cheaply, and have poorly absorbing versions of the vitamins (because they’re cheaper…) in them and you’re just going to poop or pee it out. You want to buy versions of your micronutrients that have been designed to be more bioavailable (potassium gluconate, ferrous gluconate, etc.). I don’t recommend just popping a multi-vit and with your sugar/whey/oil mix and calling it a day People survive on McDonald’s though, so you probably won’t die, it’s just that you could probably be healthier.
It does take some work to figure out what you need. I used excel, this site: http://fnic.nal.usda.gov/fnic/interactiveDRI/ and the google(finding most bioavailable options, how much is in my juice concoction, etc) to figure out exactly what I need for my micronutrients. It took me the better part of an afternoon. The good news is that you only have to do it once and it’s done. I supplement daily with a trace mineral pill, D3, magnesium bis-glycinate, tahini(which has phosphorous), salt, a sublingual liquid b-vitamin complex (which doesn’t have the absorption problems of more traditional vitamin supplements,) choline, ferrous gluconate, potassium gluconate, fish oil, flax seed, and finally a fresh juice (juicers are baller) made from celery, kale, cucumber, red cabbage, and an orange. I’m 97.3% sure that everything is covered and in the correct amounts. Anectdotally, I’ve been soylenting for 8 days and although I’m doing a 500 calorie deficit, I have way more energy than when I was eating regular food.