Not every category here carries the same weight of established research. Unbox Health tests what is inside every product for label accuracy, safety and nutrition, not its efficacy. Whey Protein, Protein Powders and Creatine rank among the most studied protein supplements for muscle gain. Electrolytes have an established role in hydration. Protein Bars, Milkshakes and Peanut Butters are food sources of protein: evidence concerns content and quality, not performance. Multivitamins vary by formulation.