Nutritional yeast

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.

Where To Buy Nutritional Yeast

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

If you don't have nutritional yeast you can substitute per tablespoon:
2-3 teaspoons Brewer's yeast (slightly bitter)
OR >2-3 teaspoons Yeast extract
OR>1 tablespoon grated Parmesan cheese (to add a cheesy flavor).