Current evidence doesn’t suggest coffee contains toxic levels of mold, nor that it causes cancer

Mycotoxins are a collection of toxins produced by molds. These molds can grow during any stage of the production, harvesting, and storage of crops or food products such as coffee beans, especially under warm and humid conditions.

In May 2024, posts circulating on Facebook and TikTok claimed that ochratoxin A (OTA), one type of mycotoxin, can be found in coffee. At the time of publication, the TikTok had more than 400,000 views and 19,000 likes. The posts claimed that OTA causes cancer, and that the reason we feel the need to urinate so quickly after drinking coffee is because the body needs to flush OTA out of our system.

The posts were pulled from an episode of the podcast Heal Squad x Maria Menounos titled “Heal Your Hormones w/Dave Asprey”. The episode was recorded and shared on YouTube on 15 May 2024. In the podcast, television correspondent Maria Menounos interviewed Dave Asprey, a self-proclaimed “biohacker” who claims he has raised his IQ 20 points and predicts he will live to the age of 180.

The International Agency for Research on Cancer (IARC) classified OTA as a Group 2B carcinogen in 1993, meaning there is limited evidence it may cause cancer in humans. For context, other substances classified as Group 2B carcinogens include aloe vera and pickled vegetables.

OTA has been shown to cause adverse health effects related to renal diseases and cancers in animal studies^[1]. Some mycotoxins also present other health risks, including short-term maladies such as food poisoning and longer-term chronic conditions such as immune deficiency and cancer.

However, current evidence doesn’t support an association between the OTA levels in coffee and adverse health effects such as cancer in humans. We explain below.

Current evidence doesn’t suggest coffee contains toxic levels of ochratoxin A (OTA)

A risk assessment conducted by the European Food Safety Authority (EFSA) found no evidence of an association between OTA and bladder or liver cancers in humans^[2].

A published review also looked at studies evaluating the relationship between OTA and coffee, to assess whether levels of OTA in coffee could be harmful to humans^[3]. It determined:

“An adult weighing 70 kg would have to consume over 410,000 servings of coffee, each made with 7 g of coffee containing an OTA level of 4.8 µg/kg (the upper range of OTA occurrence in US coffee), to reach the lowest level associated with lethality of OTA in mammals (0.2 mg/kg in dog).”

That review also highlighted the nuances of OTA’s health risks, insofar that it does present health risks—but that the levels present in coffee don’t suggest cause for concern^[3]. The authors stated:

“OTA presents a unique scenario in food safety, because it is known to be a potential risk; because heating may destroy it, but not completely; and because the hazard profile suggests it is not acutely toxic at the occurrence levels in coffee, although at high exposure levels, it is potentially nephrotoxic and carcinogenic in animal models.”

Finally, in a systematic review of human studies, researchers evaluated published studies to determine if toxic effects of OTA could be found in humans. The authors of the study noted that after they evaluated more than 2,400 studies, only three remained which met their eligibility criteria for review. They found “no statistically significant associations between OTA exposure and any human disease”^[1], but also cautioned that more studies with larger sample sizes and control for potential confounders are needed before OTA can reliably be determined as harmless.

Coffee is a diuretic, which causes increased urine production

In the podcast, Asprey posed to Menounos: “You ever drink coffee and then you have to pee 20 minutes later and your bladder’s not full? Why did you have to pee without a full bladder? Because there’s toxins in your pee and your body’s like, get it out of here!”

This implication—that the body considers OTA a toxin and quickly excretes it through urine—is misleading. According to the EFSA risk assessment, the process by which the body excretes OTA isn’t fast:

“OTA is rapidly absorbed and distributed but slowly eliminated and excreted leading to potential accumulation in the body, which is due mainly to binding to plasma proteins and a low rate of metabolism.”

Moreover, the claim misconstrues the diuretic effect of the chemical caffeine, a natural diuretic, as a mechanism for eliminating OTA. Diuretics increase urine output by filtering excess salt and water through the kidneys, which can make a person urinate more.

In brief, coffee can make people urinate more frequently, but this is due to caffeine, not toxins in the coffee.

“Toxic” coffee claim may be linked to marketing of Bulletproof diet and Danger Coffee brand

Asprey is known for inventing the “Bulletproof” diet, which combines intermittent fasting and principles of ketogenic diets.  For context, Asprey doesn’t have medical or nutritional training, nor a background in biological sciences. According to his LinkedIn page, he received an MBA from Wharton, the University of Pennsylvania’s business school, and a Bachelor of Science in Computer Information Systems from California State University.

Bulletproof coffee, sometimes marketed as “butter coffee”, is part of the Bulletproof diet. It’s been criticized for lacking scientific evidence relative to its efficacy. Reports from numerous outlets show that Asprey cherry-picked scientific literature to support the claim that the Bulletproof diet lowers metabolism and boosts energy levels.

In the Heal Squad x Maria Menounous podcast, Asprey explained that he “invented mold-free coffee” to counter the lack of U.S. government regulations on toxins in coffee. He sells this product under the name “Danger Coffee”.

As a general rule of thumb, the U.S. Food and Drug Administration (FDA) suggests erring on the side of caution when using products marketed as quick or easy solutions for health issues. The FDA elaborates:

“Dietary supplements are regulated by the FDA, but much of our role begins after products enter the marketplace. In fact, in many cases, companies can produce and sell dietary supplements without even notifying the FDA.”

And the FDA further adds:

“If a supplement promises a cure or quick fix for a health problem, it is probably too good to be true.” 

Conclusion

While mycotoxins like ochratoxin A (OTA) can pose health risks, current evidence indicates that the levels of OTA found in coffee are not harmful to humans. Additionally, claims linking the diuretic effect of coffee to the body’s need to flush out OTA are unfounded, as the rapid need to urinate after coffee consumption is due to caffeine’s natural diuretic properties rather than toxin expulsion.

REFERENCES

• 1 – Bui-Klimke and Wu. (2015) Ochratoxin A and human health risk: A review of the evidence. Critical Reviews in Food Science and Nutrition.
• 2 – Schrenk et al. (2020) Risk assessment of ochratoxin A in food. EFSA Journal.
• 3 – Heintz et al. (2021) Assessing the food safety risk of ochratoxin A in coffee: A toxicology-based approach to food safety planning. Journal of Food Science.