Verdict: Most people should aim for no more than 1 tablespoon to 1/4 cup of nutritional yeast per day (15-60 mL).
Summary:
- This serving size is based on the upper tolerable limits of vitamin and minerals, set by the NIH. In particular, some people are prone to a flushing side effect caused by niacin.
- Some people can tolerate larger servings with no issues.
- It is possible to have a sensitivity or allergy to nutritional yeast; consult a doctor if you suspect you have one.
Nutritional yeast is a great way for vegans to get that “cheesy” flavor, and since it’s fortified with several nutrients, it’s a healthy addition to most diets.
However, it is possible to overdo it.
You’ve likely noticed that it contains well over 100% of some vitamins on the nutritional label, and reasonably wondered if it was safe to eat in large amounts.
So let’s find out.
Table of Contents
Potential Side Effects of Nutritional Yeast
The main negative side effects of eating nutritional yeast are:
- Allergic reactions – It is possible to be allergic to yeasts, including nutritional yeast.
- Overconsumption of vitamins and minerals – Nutritional yeast is typically fortified with a significant amount of nutrients.
Note that I’ve seen some people claim that nutritional yeast is high in purines, but have not been able to find any research that shows this (source).
Nutritional Yeast Nutritional Content
As far macro content goes, nutritional yeast consists of nearly all protein and fiber.
The potential side effects come from the added vitamins and minerals. While generally healthy, too much can be a bad thing.
Most of these vitamins are water soluble, meaning that you’ll simply urinate out the rest, so there’s no concerns of overdoing it. However, some do have a tolerable upper limit set based on extensive research that you want to be mindful of.
Using the nutritional data from Bob’s Red Mill nutritional yeast, I’ve created a table to help answer the question at hand. It may differ by brand, but should be close.
The tolerable upper limits in the table are from NIH datasheets.
| Nutrient | Amount in Nutritional Yeast (1/4 cup) | Tolerable Upper Limit | Servings to Exceed Limit |
|---|---|---|---|
| Calcium | 6 mg | 2,500 mg | 416 |
| Iron | 1 mg | 45 mg | 45 |
| Potassium | 264 mg | Not established | N/A |
| Thiamin | 11.8 mg | Not established | N/A |
| Riboflavin | 9.7 mg | Not established | N/A |
| Niacin | 46 mg | 35 mg | 0.76 |
| Vitamin B6 | 5.9 mg | 100 mg | 17 |
| Folate | 1828 mcg | 1,000 mcg | 0.55 |
| Vitamin B12 | 17.6 mcg | Not established | N/A |
Four of the nutrients have no tolerable upper limit, so we don’t need to be worried about them at all.
Of the others ones, 3 require 17 servings (of 1/4 each), or 4.25 cups of nutritional yeast before being concerning. I don’t know anyone who could eat that much.
But two vitamins do look a bit worrying: Niacin and folate. Nutritional yeast is by far the best source of folate for vegans (although it’s not particularly hard to get).
If you have more than 1/8 of a cup of nutritional yeast, you will surpass the safe tolerable upper limit for adults.
The question is how big of a deal is this?
What Happens When You Have Too Much Niacin?
Even just a tablespoon of nutritional yeast gives some people enough niacin to cause skin flushing (turning red), and sometimes even becoming dizzy.
If you’re affected by that, limit yourself to a tablespoon of nutritional yeast per day.
Most people won’t have serious side effects unless they regularly take more than 2,000 mg of niacin per day, according to the Mayo Clinic, which could lead to:
- Rapid heartbeat
- Itching
- Nausea and vomiting
- Abdominal pain
- Diarrhea
- Gout
- Liver damage (from sustained high levels of niacin)
- Diabetes
To put this in context, it would take 20 servings, or 5 cups of nutritional yeast, to hit 2,000 mg of niacin in a day.
And you’d have to do that fairly regularly to cause serious damage (assuming you’re healthy and don’t have any adverse reactions to niacin).
If you’re sensitive to niacin and experience flushing symptoms, limit your daily intake of nutritional yeast to approximately 1 tablespoon. See a doctor if you experience any serious symptoms listed above.
What Happens When You Have Too Much Folate?
Folate is controversial.
The upper limit is set really low, and it’s set specifically for folate from supplements, not food intake.
Furthermore, a very recent study (January 2018) from Queen Mary University of London, has basically said there’s no need for an upper folate limit.
They argue (strongly) that the upper limit was set incorrectly in the first place.
The upper limit on folate is controversial. It’s possible that getting too much folate from nutritional yeast may cause health problems, but some researchers also say that there’s really no cap needed on folate intake.
Summary: How Much Nutritional Yeast Can You Eat in a Day?
The data is a bit conflicting, but let’s try to sum things up:
- The only real concerning vitamins that you can overdo are niacin and folate.
- If you have a reaction to niacin (skin flushing), you should probably only have a tablespoon or so of nutritional yeast per day.
- If you don’t have a reaction to niacin, and are otherwise healthy, it’s very difficult to cause serious harm to your body by ingesting too much niacin from nutritional yeast.
- Folate is controversial, and recent research suggests there should be no upper limit on its intake from food.
What all that means (and keep in mind this is not medical advice!), is that if you want to be on the safe side, keep your nutrition yeast intake to 1 tbsp per day.
In general, most people should aim for 1 tablespoon to 1/4 cup of nutritional yeast per day if eating it for health benefits. There’s typically no rush to consume it, since it takes a long time for nutritional yeast to go bad.
