Note from Dr. Greger: In short, we found detectable amounts of lead in samples of Frontier, KAL, and Whole Foods brand nutritional yeast, but the lead levels were so low that they all comply with the exceedingly (and justifiably) strict California Prop 65 standards. Still, I advise pregnant women who eat more than a third of a cup a day on a regular basis choose a different brand. No detectable lead levels were found in Bob’s Red Mill, Bragg, Dr. Fuhrman, Red Star, or NOW Foods brand nutritional yeast.
Nutritional yeast has grown in popularity and is being introduced into many new dishes and recipes. It has a nice “cheesy” flavor and texture that can be used in sauces and soups or sprinkled over salads and popcorn. Dr. Greger recently covered how the beta glucan fiber in nutritional yeast can modulate our immune system and help to maintain our body’s defense against pathogens (See Dr. Greger’s video on Nutritional Yeast to Prevent the Common Cold). It seems beta glucans can be found in many foods, including mushrooms, which have been shown to boost immunity as well.
A safety concern arose when Dr. Greger was notified that California’s prop 65 warning stickers were found on packages of nutritional yeast, suggesting there’s something in it exceeding cancer or reproductive safety limits. It turns out the problem was lead. There are many contaminants in the environment and in our food supply, even found in our children, which is probably why California has such strict guidelines on contamination. For example, California considers candies with lead levels in excess of 0.10 parts per million (ppm) to be excessively contaminated. State law requires products that contain more than half of a microgram of lead per daily serving carry a label warning consumers. Could nutritional yeast carry lead levels this high?
We reached out to some of the companies who produce nutritional yeast in hopes to better understand the situation. We asked if they perform lead testing and if they could share any information. The results of Dr. Greger’s inquiries can be found in his video here. He was frustrated by the lack of responsiveness and so decided we should take it upon ourselves to do our own testing. The NutritionFacts Research Fund was created and thanks to generous donor support we tested samples from 8 companies for the presence of lead in hopes to spur them to do their own testing.
We hired an independent lab to conduct our tests for lead. I shipped out 8 samples of nutritional yeast in their original package. The lab used standard practices for lead testing known as Official Methods of Analysis set by AOAC International. Lab technicians determined the lead values based on California Prop 65 standards. Here are the results from the brands we tested:
Bob’s Red Mill – Test report shows no detectable lead (<0.01 ppm).
Bragg – Test report shows no detectable lead (< 0.01 ppm).
Dr. Fuhrman – Test report shows no detectable lead (< 0.01 ppm).
Frontier Coop – Test report shows lead levels at 0.021 ppm. It would take six tablespoons a day (based on the manufacture’s listed density) to exceed the California Office of Environmental Health Hazard Assessment Maximum Allowable Dose Level (MADL) for chemicals causing reproductive toxicity.*
KAL – Test report shows lead levels at 0.011 ppm. It would take seven tablespoons a day to exceed the MADL.*
NOW Foods – Test report shows no detectable lead (< 0.01 ppm).
Red Star – Test report shows no detectable lead (< 0.01 ppm).
Whole Foods – Test report shows lead levels at 0.012 ppm. It would take six tablespoons a day to exceed the MADL.*
So what do all those numbers mean? None of the brands tested exceeded California prop 65 standards. No matter what brand, consuming a typical serving (2 tablespoons) per day is still well within safe limits. I will certainly continue to include the stuff in my diet. Dr. Neal Barnard once said, “It’s not about ALL foods in moderation, it’s about healthy foods in moderation. Broccoli is great, but you don’t want to just eat broccoli. Kids exercising is wonderful, but you don’t want them to exercise all the time.”
-Joseph Gonzales, R.D.
*Note from Dr. Greger: The Maximum Allowable Dose Level for lead as a developmental toxin is 0.5 micrograms a day. How are MADL’s calculated? Basically scientists figure out what the “no observable effect level” is, the level at which no birth defects or reproductive toxicity can be found, and then introduce a 1000-fold safety buffer. So for example, let’s say there’s some chemical that causes birth defects if expectant moms are exposed to two drops of the chemical a day, but there’s no evidence that one drop a day is harmful. Do they set the Maximum Allowable Dose Level at one drop? No, they set it at 1/1000th of a drop to account for scientific uncertainty and to err on the side of caution. So by saying six tablespoons a day of nutritional yeast may exceed the MADL is in effect saying that the level of lead found in 6,000 tablespoons of nutritional yeast may cause birth defects. Like mercury, though, as far as I’m concerned the less lead exposure the better. I hope this will inspire companies to do further testing to see if the levels we found were just flukes.