There is no one answer to your question.

There are times when nutritional supplements can be beneficial and there are other times where they may not be advisable. It would depend on your specific situation and the purpose behind you using them.

Typically, nutrients should be ingested through food. Supplements are used to fill any gaps that may arise in your nutritional plan.

Hope that helps.

Dev Chengkalath
http://devchengkalath.com

As Mr Chengkalath said, supplements are to supplement your diet if you can't get what you need from food. The only one who can really tell you if you need them is your doctor. They are not going to make you stronger or faster. Only training will do that. Also, there is nothing that suppliments give you (at least according to the labels) that you can't get from food. E.g. if you want to increase you protien, eat more egg whites...
Also they are not controlled or tested by any agency, so they may contain things not on the label. I know of at least one swimmer who missed out on his Olympic chance becaue he took a doctor reccomended multivitamin. It just happened to be manufactured in a plant where other drugs were made and was contaminated with a banned substance.

David Warren
From the Pacific Northwest
Where swimming is an indoor sport