Are they necessary for proper nutrition while training?

We would say that they are complementary, but not the base of our diet. They can make up 10% and should only be used when necessary.

There's a huge variety of sports products and we're going to talk about some examples:

• Omega-3, Omega 3, 6, 9: if you eat fish two or three times a week, mainly salmon, sardines or tuna, you shouldn't need any supplements. If you take them because you don't eat much fish, make sure to take omega-3 or a good quality Krill oil, high in EPA and DHA, which are the essential fatty acids we need. 
• Creatine: there is a lot of controversy over this product, because some experts defend it and others do not. This is because creatine is found naturally in our diet but is mostly lost as we cook foods, meaning we don't get enough of it. If you're going to take creatine, it is best that it be monohydrated, which helps you use stored energy and will mean less muscle fatigue while training.
• Caffeine: it has been proven to help boost performance and delay fatigue. The problem is that if we take it daily before training this effect is diminished after a few days. So, we only recommend taking caffeine pills when very fatigued. Having an espresso before training is okay but doesn't normally give you the levels necessary to feel a difference.
• Tribulus terrestris: This product has been proven to boost libido, but it's power to increase testosterone levels has not been scientifically proven, meaning it doesn't work. It is a placebo.
• Glutamine: is the most common amino acid in our muscles, helping repair muscle fibres damaged in training. It is an amino acid that doesn't need to be supplemented, as it is commonly found in our diet.
• Protein powders: these work in the same way as eating a chicken breast, steak or fish fillet… So, taking protein supplements can help us reach the protein levels we need to regenerate muscle after a hard training session, but this can also be done through diet.