Occasionally I'll check reviews of vitamins and supplements that claim to use testing by independent labs. Most seem to be within acceptable limits. And I'll check the PubMed site for NCBI/NIH studies for any supplement or alternative "medicine".
I've tried various supplements given to me by well meaning family and friends -- glucosamine, chondroitin, etc. -- mostly for chronic joint pain after a previous car wreck busted up my back and neck. Can't tell that they helped so I didn't buy them myself after the initial 30-90 day supply. If I don't see a difference in how I feel or lab work after 90 days there isn't much point to wasting money on supplements for which there's no definitive medical evidence.**
For years I took a multivitamin. Most of our nutrients come from a good diet. The multivitamin was just a little insurance for the days when I didn't eat well or my immune system seemed stressed. I have a long running auto-immune disorder that finally destroyed my thyroid, confirmed by a biopsy this past week. It's just a non-functioning mass of calcified dead tissue, swollen enough to distort and constrict my esophagus and trachea. Doesn't look that bad from an exterior view, not a grotesquely swollen goiter, but was enlarged much more than we'd realized inside.
So this year as my health deteriorated I began taking more individual supplements -- particularly iron since I was borderline anemic despite a good diet and exercise.
Do I believe it will help? Frankly, nope.
Many folks in my family were very health conscious, eating well, taking lots of vitamins and supplements, keeping their weight reasonably close to the optimal upper limit -- still a bit overweight but not obese. Others were exactly the opposite, gorging on junk food, ballooning in weight to grotesque proportions, along with the usual complications -- mostly diabetes. They'd like to believe it's due to metabolism but I've spent enough time around them to know it's just their diet, mostly eating enormous amounts of sugary junk food and simple carb snacks, and rarely doing any physical activity.
Did these differences in diet seem to make any difference in longevity? Frankly, nope.
My family members who ate a healthy diet and got at least a little exercise seemed to enjoy a better quality of life, while it lasted. They seemed both physically and emotionally healthier. Most lived to anywhere from their mid-70s to upper 80s. My dad was probably the most health conscious of the lot, always keeping his weight close to optimal, eating well, staying active although over time he dropped tennis and switched to golf. He developed prostate cancer in his late 60s and died in his mid-70s, relatively young by our standards. Even my dad's father lived longer, and my granddad was usually overweight, had COPD and congestive heart failure from years of smoking. But granddad had been pretty active with gardening and puttering around their rural home, so he wasn't indolent. Only during his last couple of years had he finally become unable to do much more than walk indoors.
The side of the family with culturally ingrained obesity due to bad habits had lots of nagging health problems, were unhappier, bickered a lot, were angry about everything all the time and had lots of substance abuse problems with consequent legal problems. But lifespans were about the same, roughly age 70 to mid-80s.
So, now at age 60, I don't expect my diet, exercise and supplements to prolong my life. The best I can hope for is a good quality of life while I'm still around. I'm hoping that surgery to remove the junked thyroid and get on appropriate supplements will restore some energy and minimize some nagging problems with exhaustion and chronic pain. I still have some pretty good days, use my indoor trainer a few times a week and get an outdoor ride once a week or so (I'm also recovery from a broken and dislocated shoulder from being hit by a car in May, which has limited my outdoor rides to 20-30 miles about once a week).
**I have made some exceptions recently. Chronic pain from the more recent shoulder injury and nausea from the thyroid condition motivated me to try some alternatives to conventional meds. The doctors wouldn't authorize refills of Tramadol or hydrocodone, even though I used those very seldom (my "10 day" supply lasted me 6 weeks). Ibuprofen wasn't touching the pain -- it's good only up to pain level 5 on the scale of 10. My chronic neck and shoulder pain have been around 6-8 every day for months. And I was experiencing nausea from the thyroid disorder, but the prescription ondansetron was giving me headaches and wasn't helping much. Between the pain and nausea I was losing weight and recently lost 10 lbs in less than two weeks -- and at 5'11" and 160 lbs, I didn't have 10 lbs of excess body fat. I was losing muscle mass too, but couldn't choke down much solid food. I've mostly been getting by on smoothies with protein and supplements, oatmeal, yogurt, etc.
So based on recommendations from friends I tried CBD, the non-psychoactive cannabidiol derivative from cannabis. While it didn't help with my pain, it did help with the nausea. For that use alone it's worthwhile, and there are studies on PubMed confirming the efficacy of CBD for controlling nausea and vomiting. The sublingual oils from droppers seemed to be the most effective for that. I've also tried capsules up to 50-60mg per day, and vaping (reluctantly, since I quit smoking 20+ years ago). I can't tell any effect from the capsules or vaping, including for nausea. It appears the stronger CBD oils taken sublingually and swallowed act more directly to reduce the gagging and nausea. So while I'm not completely on board with the hype claiming cannabis is a miracle cure, it certainly helped with one specific problem.
Since CBD didn't help with the pain, the manager at a health food shop where I bought the CBD suggested kratom from the mitragyna speciosa plant, a relative of the coffee bean plant. It works remarkably well on pain, much more effectively than ibuprofen, and roughly comparable to a low strength prescription med like Tramadol (which used to be considered the safest and least addictive opiate derivative before the current anti-opiate hysteria that's most due to abuse of black market fentanyl coming from China). For now kratom is legal in most states and I hope it remains that way. The FDA is considering regulating or banning it but granted a stay for now while the plant is being researched to determine efficacy. The FDA's official position is that mitragyna speciosa has no medicinal value, but they're definitely wrong about that. There are also some claims that it has some mood enhancement properties but I haven't noticed that, although I've use it relatively seldom and as little as possible only for the worst pain. Reportedly petitions from military veterans helped to delay any regulations or bans, as many injured vets with chronic pain have encountered the same challenge -- either they want to avoid addiction to opiates, or their health care providers have refused to authorize refills of opiates.
Anyway, after dropping to 150 lbs last week I've put on a few pounds and hover around 154 right now. I'll credit these unconventional "meds" for relieving the pain and nausea enough to help me rest and eat.