Optimum Nutrition is part of Glanbia, a cheese and nutritional manufacturer. It offers nutritional products in every category, including protein powders, nutrition bars and vitamin supplements, according to the Optimum Nutrition website. While many of these products are gluten-free, including most of the 100 Percent Gold Standard protein powder flavors, the manufacturing plant is not a gluten-free facility. If you require a gluten-free diet, use caution when considering the 100 Percent Gold Standard Protein powder from Optimum Nutrition.