For years I took no supplements, not even a multivitamin. I just ate a good healthy diet.
Then I ended up with Hashimoto's, an auto immune disorder that ended up with thyroid cancer on one lobe (surgically removed, no chemo so far) and left the remaining lobe barely functional. The docs plan to leave it intact as long as it doesn't also become cancerous, just in case it still contributes a little something to my metabolism and bone health.
Meanwhile I suddenly had zero energy, could hardly get out of bed other than to pee, bone density loss, and a bunch of other problems. I used to heal very quickly from any injury and rarely scarred. But for awhile I wasn't healing. I was also hit by a car in 2018 and it seemed to take forever for the shoulder to heal. Bone scans showed I had a bunch of minor fractures that I wasn't aware of.
Worst of all, I couldn't seem to metabolism alcohol anymore. I loved beer but it doesn't love me anymore. For awhile I tried cutting back to just one, once in awhile, but still felt sick within an hour or so. Not worth the hassle. Haven't had a beer or other alcohol since December. Saves a lot of money. I really enjoyed local craft beer, which is pricey stuff.
My doc prescribed large doses of vitamin D and calcium. I started taking a bunch of other supplements. In addition to a regular diet (now leaning more toward full carnivore, less sugary fruit, some veggies, fewer carbs), I use whey and legume protein powders -- mostly to mask the flavor of the other supplements, some of which are bitter. Various amino acids, depending on my workout/ride schedule, extra niacin pre-ride/workout. Concentrated spinach powder and beta-ecdysterone from various sources. Creatine, especially on days when I don't eat red meat. I eat a lot of liver.
Seems to help. I went from pretty good shape for age 60 before the thyroid thing to being unable to do much more than walk for months. Now I'm a bit stronger and faster than I was three years ago.
There's no single supplement that's a magic bullet, although creatine and niacin seem to have a fairly quick and noticeable effect. The others, particularly the beta-ecdysterone, are more medium term and take a few days to notice, including when I discontinue them for awhile.
And a bunch of steroid inhalers for chronic upper respiratory inflammation. I've had elevated monocytes for months. PITA but I'm doing okay all things considered.
I may be making mostly expensive pee, but I'm still spending less money that I did on craft beer.
I've lost a lot of body fat, down from 175 lbs when I resumed cycling in 2015, and down from 160 before the thyroid cancer to between 145-150 now, close to my optimum weight in my 20s.
I don't sunburn anymore, which is weird. I used to burn easily, even when I used sunscreen. Now I don't use sunscreen at all and just get brown -- although I've got that old dude uneven mottled tan from uneven melanin, vitiligo from the Hashimoto's. And more freckles. I don't care. I'm just curious to see whether it helps with my vitamin D and bone density during my next scan.
I'm not advocating this mess for anyone else. Just seems to work okay for me.