Yes - big research needs. We know from trials that supplements do not lower your risk of dementia, cardiovascular disease or death - testing whether they make you feel better, better skin, hair,... would need to be tested in placebo-controlled randomized trials.
Recent meta-analysis 2017 in JAMA. "In this meta-analysis of randomized clinical trials, the use of supplements that included calcium, vitamin D, or both compared with placebo or no treatment was not associated with a lower risk of fractures among community-dwelling older adults"
Agree - eat less, move more, and rely on healthy food choices for disease prevention. If taking a multivitamin is a way to remember this every day, then probably ok to take - but don't count on the supplement to confer health benefits
Large randomized placebo controlled trials (where confounders are equally distributed in both arm) -best way to determine health benefits. Putting those trials together in meta-analyses have found no evidence to support antioxidant supplements for disease prevention #vitaminchat