Science-Based Nutrition Helps Combat Stress and Tension Dietary Supplement Non-GMO / Gluten Free / Soy Free / Vegan Doctor's Best Calm with Zembrin helps combat stress, tension, and occasional anxiety. It helps increase attention, focus motivation, and concentration. Zembrin is a patented standardized extract a Sceletium tortuosum; its use has been documented for more than 300 years. It has been clinically shown to enhance cognitive function and is cultivated in an environmentally stable process. Helps enhance executive function. Helps enhance processing speed.