Just one of losts of studies:
For creatine:
http://www.sncsalvador.com.br/artigos/efeitos-da-suplementacao-de-creatina-na-performance-e-treino.pdf
this extract about protien is good too:
[/i]Is more better?
Eating more than the recommended protein intake offers no benefits. Apart from being costly, a protein-based diet commonly displaces important carbs from the diet. That is, if you have an omelet and a protein shake for breakfast instead of cereal with banana, you'll consume fewer carbs to fuel your muscles properly.
Carbs are the primary fuel for athletes who do muscle-building resistance exercise. Once your muscles become carb-depleted, fatigue sets in and your workout is over. Your diet should provide extra carbs, not extra protein.
If you consume too much protein from supplements, you may also fail to invest in optimal health. For example, I had one client who daily ate five protein shakes and four protein bars to the exclusion of standard food. Displacing natural foods with engineered foods (such as protein supplements) limits your intake of the vegetables, fruits, grains, fiber, phytochemicals, natural vitamins and other health-protective nutrients that Nature puts in whole foods.
Pre- and post-exercise protein
Q. I've heard I should eat a protein bar for a pre-exercise snack?
A. Protein has typically been consumed at meals, away from the time of exercise. New research suggests eating protein before you work out can optimize muscle development. Pre-exercise protein digests into amino acids that are then ready and waiting to be taken up by the muscles after a strength workout.
This does not mean you'll evolve into Charles Atlas; you'll simply optimize your body's ability to build and repair muscle at that moment.
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