Does Nutritional Yeast Break a Fast?

In most cases, you shouldn’t use nutritional yeast during your intermittent fast. Here’s what you need to know.

Does Nutritional Yeast Break a Fast?

Whether or not something breaks a fast depends on your goal with Intermittent Fasting. If you’re looking for the gut health perks of Intermittent Fasting, then anything other than water and electrolytes will likely break a fast. However, if you’re looking to achieve a weight loss goal, then anything that causes insulin (the storing hormone) to spike will break a fast. This means if an ingredient contains protein or carbs in certain amounts, then it’s best to keep it during your eating window.

Nutritional yeast (specifically the fortified variety) is packed with B vitamins such as B2, B3, B6, Folate and B12. In fact, it’s due to this high B vitamin level that most individuals add nutritional yeast to their food (other than for the cheesy flavor).

Vitamins on their own won’t break a fast, but the protein and carbohydrates in it will. One teaspoon of nutritional yeast has around 10 calories, 1.5 grams of protein and 1 gram of carbohydrates (however, about 2/3 of the carbs are actually fiber).

If you’re following a “clean” fast, then any amount of nutritional yeast will break a fast. However, technically if you’re following a “dirty” fast (or fasting mimicking), you should be okay with 1/2 tsp. nutritional yeast or less.

This is because the amount of carbohydrates and protein in 1/2 tsp. of nutritional yeast isn’t likely enough to raise insulin and therefore break a fast.

However, most people will take around 1-2 tsp. (or more) of nutritional yeast when using it for flavor or as a supplement. With this in mind, you likely might be better off keeping your nutritional yeast to your eating window.