Great question - thank you for asking. If I might offer my personal story in an effort to assist you and others.
As a certified personal trainer, I literally skipped the nutrition section because I did not believe in supplements (I excelled at the other sections and passed first time irrespective of the lack of my knowledge on nutrition and vitamins!). Then as I got older and the doctor tested me and found vitamin deficiencies - first B12 (a genetic trait), then vitamin D, I did a 360-degree turn.
I have tried several supplements and not all supplements work for me. However, remember, I have a body that will not retain B12 so I am not the best case scenario.
I have started taking Omega to combat RA. My mother was crippled with RA, my grandmother swore by cod liver oil. I have tried several Omegas and have had outstanding results with Procaps Omega 3 Fish Oil. As a side benefit beyond my joints, my hair has changed to a point where my hairdresser has even noticed!
In my exuberance for fitness and strength, I have overdone protein so I caution you and our fellow Hubbers to learn from my mistakes, take special note of your body's needs, but most importantly, consult your physician.
Metabolism is complex because it is customized - your body type, your genetics, your exercise, and of course, your nutrition are all important components. Building muscle demands proper nutrition including protein. Often metabolism can change more rapidly if you train the larger muscles - the heart and the legs - therefore, the cardio.
My number one recommendation is to talk with your physician. Your physician can run blood tests and customize your care.