Although there may be some nutritional supplements, when used sparingly, that can augment an athlete's diet, the only fuel that a growing kid needs is a well balanced diet and maybe a daily multi-vitamin. Nothing replaces lean meats, fruits, vegetables and grains as a source of energy to support performance.
It is important for parents to understand that the neutraceutical industry is ENTIRELY UNREGULATED in the US. There is no FDA or other agency to routinely check up on the GNC's of the world to see if what they say they're putting in their potions is what's really there. Companies can manufacture whatever "health product" or "performance enhancement" supplement they want, make fantastical claims about their powers, and no one will ever double check to see if they're telling the truth. Recently, a disturbing story broke about an investigation by the New York AG into the contents of herbal supplements sold by major retailers. The results were quite alarming and I believe that this is only the tip of the proverbial iceberg. More and more of these stories will come to light. These products are dangerous and should be avoided.
Likewise, avoiding a diet of processed foods, fast food, high sugar beverages, heavily caffeinated "energy drinks" and other chemical-laden foods and drinks is critical to the health and performance of your child. There's a saying..."garbage in, garbage out." That's a saying for a reason. What your child puts into his body is all his body has to build muscle and bone, it's all she gets to support the oxygen carrying capacity of her blood, it's the only source of energy he has. No fortress can be built on bricks of sand and dust. Make sure the nutritional building blocks your goalie eats are solid ones!
Linked below is a video series by Maria Mountain of Revolution Conditioning in London, ON and sports nutrition specialist Lisa Cianfrini of NutraGeneRD. They discuss some important points about nutrition for young athletes. It is worth the watch!