Many people talk about supplementation, to ensure that dietary matters are okay. Definitely nutrient deficiencies should be looked into. However, there is one matter that is seldom given a thought. That is the adequacy of the basics. Everybody should know and understand the basics.
Adequate hydration is extremely important. Disease follows prolonged dehydration - virtually every disease! Become aware of this subject: read Dr Batmanghelidj's "Water For Health, For Healing, For Life" or "Your Body's Many Cries For Water" especially for what he writes about water, about salt, and about healing. In fact, read the whole book. His comments about salt may be very relevant too: for a salt deficiency impacts on the brain in many "departments". Body functions are critically dependent on water.
Man was designed to live on fresh natural foods. Not cooked. Not processed. You cannot be healthy living on cooked and/or processed foods only. Such "foods" must be only a minor part of one's diet.
We should only consume pure clustered water. Anything else is polluted water that will not be clustered. Pollutants seem to cause the water molecules to clump together in huge (relatively) masses and, further, seem to be very poor at water's vital tasks of distributing nutrients etc to our body cells and very poor at removing wastes and any toxic materials. Water is even less able to fulfill these tasks when the body is dehydrated. A good spring water will likely be mostly clustered water.
Failure to attend to these matters in any "poor health" situation is likely to greatly affect any measures taken just to consume extra supplements. I'm 74, and that has given me time enough to realize and learn that, when you get the basics right, most everything that might be ailing you will come right. Note that my gains, from paying heed to what I "preach", have occurred in the last few years, when I have been having ample good water and ample good salt (plus an improved diet with ample minerals).