This would have to be one of the questions that i get asked the most and probably one which is the hardest to answer. There are so many areas to this question and there is not a definite yes or no answer. And also one of the reasons why consultations with Nutritionists can take an hour as you need to get in depth as to what is going on in your body and all aspects of your health to be able to answer this question. But I will try to point you in the right direction in this blog post.
If you google supplements, there are floods of articles trying to persuade you to "buy this one" or "this one promises to make you superman". When a supplement has a claim like that, that is my queue to run for the hills. If a supplement actually works, like actually does what it claims its supposed too, then the results should speak for themselves and the word of mouth would be enough to sell it and they wouldn't need to market and have these huge claims on there and would also be backed by scientific evidence.
Now, I firmly believe in fixing the diet first and then supplementation second. Supplements as the name suggests are there to do exactly that, add on to an already nutrient dense diet and should not be prescribed forever. They are there to help boost your nutrients back up to a certain level when you have a deficiency and you then stop taking them or gradually reduce the amount until you can stop taking them. Or they may not be working so you might need to stop them and change the supplement. There would only be very few circumstances where you should have to be on a supplement long term.
You need to ask yourself, why do you think you need supplements? is it because you are at the gym and everyone else says that they are taking something so you feel the need to get on board the BCAA train. Or, is it because you are noticing that you are getting fatigued, your muscles are aching or your bone mineral density is declining and food just isn't helping.
If someone outside of a consultation asks me .. should I take (insert supplement name here). I ask them, what do you think they do and why do you think you need them? And unless they can answer this I say no. You need to understand what supplements are going in your body and the reason that you're taking it, not "just because". It's the same as you wouldn't just pop an ecstasy pill, you need to be aware of what the supplements you are taking are supposed to be helping with so you can monitor their progress and adjust if they are not working.
If you do find that you are having some health issues, then yes, supplementation can probably help. I would advise having a thorough review of your diet with a health practitioner to investigate what is going on and the reasons why. More than likely in times like this that making a few tweaks and fixing up your diet will be enough to help you and you will not have to go on any supplements. But if you find after a few weeks that diet alone has not shown any significant improvement then short terms supplementation use can be very successful.