Nutritional yeast is a deactivated yeast, which means yeast cells are killed during processing and inactive in the final product.

It’s described as having a nutty, cheesy, and savory flavor. It’s a common vegan cheese substitute.

Nutritional yeast comes in the form of powder or flakes. It’s an excellent source of many vitamins and minerals. It also offers a number of potential health benefits.

While nutritional yeast is a valuable addition to many diets, there may be some side effects associated with using it as a dietary supplement.

Here are 4 potential side effects of nutritional yeast.

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1. May Cause Unpleasant Digestive Side Effects If Introduced Too Quickly

Though nutritional yeast is low in calories, it’s packed with fiber.

In fact, just 2 tablespoons (21 grams) of nutritional yeast flakes may provide about 5 grams of dietary fiber. That’s about 20 percent of the recommended intake (1).

A high-fiber diet can promote bowel regularity, but it’s important to increase your fiber consumption gradually (2).

Introducing too much fiber too quickly can lead to abdominal discomfort — such as cramps or even diarrhea — especially if you’re not used to eating high-fiber foods.

Since nutritional yeast packs a lot of fiber in one serving, it’s best to start slow and adjust servings as your body adapts to the higher fiber consumption.

When increasing your fiber intake, it’s always best to make sure you’re consuming adequate fluids as well to maintain proper digestion (3).

SUMMARY Nutritional yeast is an excellent source of dietary fiber. Due to its high fiber content, it’s best to introduce nutritional yeast gradually to avoid abdominal discomfort.

2. May Trigger Headaches or Migraine Attacks

While nutritional yeast is a great source of many vitamins and minerals — such as vitamin B-12 and zinc — some yeast products contain compounds like tyramine, which may trigger migraine attacks in some individuals.

Tyramine

Tyramine is a compound derived from the amino acid tyrosine and found naturally in nutritional yeast and concentrated yeast products like Vegemite (4, 5).

Most individuals can enjoy tyramine-containing foods without experiencing negative side effects.

However, some studies show that tyramine may cause migraine attacks in certain people (6, 7, 8, 9).

Migraine is a condition characterized by recurring — often debilitating — headaches that cause moderate to severe pain.

Researchers are still trying to understand how tyramine triggers migraine attacks.

However, it appears that tyramine may act on the central nervous system. It releases various hormones, which may lead to an increase in blood pressure and cause headaches (5, 10).

SUMMARY Nutritional yeast may contain compounds like tyramine that can trigger headaches in some people. Individuals with migraine may want to avoid nutritional yeast for this reason.

3. May Cause Facial Flushing

Nutritional yeast is an excellent source of niacin.

Just 1 tablespoon (11 grams) of nutritional yeast flakes may provide over 38 mg of niacin. That’s more than double the daily value for both men and women (1, 11).

Niacin — also known as vitamin B-3 — is involved in many vital processes in your body, such as metabolism and enzyme function (12).

Still, consuming large amounts of niacin may cause facial flushing (13).

It’s characterized as a flush of red on the skin, which may be followed by a burning and itching sensation that occurs within 10–20 minutes after ingesting niacin in high doses.

While facial flushing may be uncomfortable, it’s generally not associated with harm and typically subsides within one to two hours (14).

Furthermore, facial flushing generally only occurs after consuming extremely high doses of niacin — such as 500 mg or more — which can usually only be reached in supplement form (15).

Although facial flushing is not dangerous, high doses of niacin can cause other, more dangerous side effects, such as liver failure. However, this is rare (16).

Facial flushing caused by nutritional yeast most likely wouldn’t occur after consuming only a few servings. It’s more typical after ingesting very large doses.

SUMMARY Nutritional yeast is an abundant source of niacin. Although facial flushing is not associated with harm, consuming large doses of niacin can cause other, potentially harmful side effects.

4. Yeast Intolerance and Inflammatory Bowel Disease

Though relatively uncommon, some people may be intolerant of nutritional yeast.

It appears this may be most common in individuals with inflammatory bowel disease (IBD), such as Crohn's disease.

Yeast may trigger an immune response in certain individuals with IBD. Some studies suggest it may worsen symptoms (17, 18, 19).

Nevertheless, the role of dietary yeast in the development of IBD is still unclear. No strong evidence indicates it’s a direct cause of the disease.

SUMMARY Studies indicate that dietary yeast may contribute to symptoms in a proportion of people with inflammatory bowel disease (IBD).

The Bottom Line

Nutritional yeast is a deactivated form of yeast full of vitamins, minerals, and nutrients.

It has a savory, cheesy flavor and can easily be added to a number of different meals and snacks.

Although nutritional yeast is generally safe for most people, it may cause negative reactions in individuals who are sensitive to it.

In large doses, it can cause digestive discomfort or facial flushing due to its high-fiber and niacin content, respectively.

Nutritional yeast may also contain tyramine, which may trigger migraine headaches in some individuals.

It’s best to introduce nutritional yeast slowly into your diet and stick to lower doses of supplements to minimize unwanted side effects.