Nutritional yeast is a yeast product grown from the same yeast strain as brewer's yeast but has a nutty, rather than bitter taste. Nutritional yeast is usually available in yellow colored flakes that blend well with food. Given the yeast is very high in Vitamin B it makes a flavorful addition to smoothies.
Purchase nutritional yeast either packaged or in bulk in most health food stores including Whole Foods. You can also purchase it online at Amazon: Bragg's Nutritional Yeast