If you’re anemic /iron deficient iron supplements definitely make you stronger. Make sure to take with vitamin C (there are combination pills) or orange juice for maximum absorption. However, since bringing up your levels usually takes months (and I personally followed a multi-pronged approach which included doctor administered treatment at first, as well as dietary changes) there wasn’t this “ah-ha” moment that I can attribute to supplements alone.
I also think pro-biotics work so after I eat too much sweets I pop a few to stop symptoms in their tracks. (Don’t want to divulge tmi.) Again I think it works, but both of these issues are more prevalent in women.
And fiber supplements work great for those with issues.