There is currently a fuss

being made because one of those precious "Aussie Rules" football clubs has allegedly been caught injecting what might be a banned substance into their darling over-paid players. A lot of people are shaking their heads and expressing horror. Others, not supporters of that team but other teams, are suggesting that this is how they gained their advantage last season. Still others are saying that "everyone does it these days" - often mentioning Lance Armstrong in the same breath.
I suspect that drug taking in sport is rife. It has to be. There has to be a limit to what humans can do without external assistance. Roger Bannister's breaking of the four minute mile barrier was, I believe, mired in "assistance" controversy - assistance from the wind? I am sure someone can enlighten me. I doubt however that it was from modern performance enhancing drugs.
My sister's area of special interest within her profession is sports injuries. She also believes in the sort of diet supplements and drinks often ingested by sports players. She insisted the Senior Cat needed an exercise machine. He uses it simply because she bullies him into doing so. At ninety he is not going to re-develop the strength and coordination he had at age nine. He was never very coordinated anyway. Our mother always dreaded the dance she had with him at the annual school ball (such things being held in country schools). She complained he had "two left feet". I sympathised with the Senior Cat. 
My sister also insisted that the Senior Cat needed a dietary supplement. She arrived with a large tub of "dietary food". It was a powder, supposedly chocolate flavour, to be mixed with water. It was to be taken in addition to the meals I prepared. I was, I was sternly told, to feed him a lot more protein as well. He needed it.
I believe older people do need to watch their protein intake and that many of them do not eat enough.
We listened humbly. The Senior Cat tried the drink. He would rather eat a piece of chocolate. (We still have chocolate left from Christmas last year. We both like chocolate too much to hurry it.)
Drinking the drink made him feel he did not need a meal. We decided the meals were more important but, dutifully, he spoke to the doctor. 
The doctor listened. The doctor asked questions. The doctor laughed. No, you do not need a dietary supplement if you are eating that well. I wish all people your age ate such a well balanced diet. The Senior Cat came home and told me this. It was nice to know the doctor thought I was feeding him properly. We put the dietary supplement to one side. My sister was not pleased about this but, for once, the Senior Cat did not allow himself to be bullied by her.
We felt guilty because she means well but he does not need a dietary supplement.
I doubt many people, even sportspeople, need a dietary supplement. They do need to eat properly. They need a balanced diet with plenty of fresh fruit and vegetables, protein appropriate to their age and level of activity and carbohydrate which is equally appropriate. It all takes time to consider and prepare. 
I rather suspect that, at least for some people, that dietary supplements are seen as dietary substitutes.