Dietary Supplement. Nature's Best Perfect L-Glutamine powder is formulated with your health in mind. All Nature's Best products are manufactured from the highest quality raw materials, under strict supervision and in accordance with Good Manufacturing Practices. Extensive quality control procedures ensure proper purity, dissolution and potency. Satisfaction guaranteed or your money promptly refunded. Nature's Best products are specially packaged to protect nutrients from the effects of moisture, light and air. Keep tightly closed in a dry place, do not expose to excessive heat.