Are fungal toxins a significant problem in coffee, and if so, can they be avoided?

Time to apply a bit of healthy skepticism here:

The blog post:

• Is (so far) the first and only one I've ever seen stating mold to be a practical problem in coffee - in the sense of being present in a high enough quantity to matter (mold grows everywhere).
• Uses all kinds of weasel words to describe symptoms ("edgy", "cranky", "useless mentally").
• Describes symptoms that are well in line with plain old caffeine withdrawal.
• Frequently links to other blog posts on the same site, most of which are "top 10 ways" and "top 5 reasons" fluff pieces.
• Manages to cite and thoroughly misuse two studies: one from 1995, and another from 2003. Both are about Ochratoxin A (OA), which isn't even the biggest risk; Aflatoxin is. (More on these later).
• Advertises a fairly expensive product, sold by the same author.

The author:

• Is, according to his LinkedIn profile (which I refuse to link here), the VP of Cloud Security at Trend Micro - a Silicon Valley tech company. I could not find any evidence that he or his his employer has any experience in human biology or nutrition.
• Makes all sorts of unusual claims about himself: "He upgraded his brain by >20 IQ points, lowered his biological age, and lost 100 lbs without using calories or exercise."
• Has an entire page of testimonials, which he frequently cites as "evidence".
• Has an entire site dedicated to product-peddling, including the ubiquitous six-second abs (yes, that's hyperbole) and a $60 "earthing mat".
• Has the following disclaimers on the product site (all in tiny print at the bottom):

  _{The statements made on this website have not been evaluated by the FDA (U.S. Food & Drug Administration). Our products are not intended to diagnose, treat, cure, or prevent any disease.}

  _{The information provided by this website or this company is not a substitute for a face-to-face consultation with your physician, and should not be construed as individual medical advice. The testimonials on this website are individual cases and do not guarantee that you will get the same results.}

• In short, he employs tactics which are commonplace among con artists selling magnetic bracelets. In my opinion, all his claims are technobabble, and I think they are not trustworthy.

• The largest sample tested was just 60 samples of beans, and was tested from only one source (Brazil). This is fine for individual studies, but in the real world there are hundreds (thousands?) of sources from many different countries. It's safe to say that the current studies don't even come close to testing all of the coffee from around the world.
• Both OA studies found an incidence rate of approximately 50% for the OA-producing mold, at wildly different concentrations (minimum 0.2 ppb in one study, maximum 7.8 ppb in another). If this tells me anything at all, it's that you should probably vary your source if you want to minimize your risk.
• Neither the FDA nor the EFSA actually have a legal limit for OA, but the EFSA "suggests" a limit of 8 µg/kg, which means that even the worst samples are below the very conservative legal limit.
• One study actually tested the incidence of OA in brewed coffee, not just the beans, and found a maximum of 7.8 ppb in the brew (that's 7.8 µg per 1 kg of ground coffee).
  • For reference, there's an EFSA directive recommending an intake of no more than 120 ng/kg (body weight) per week, which comes out to 8.4 µg/week for a 150 lb/70 kg individual, or 1.2 µg/day.
  • Based on the worst contamination of brewed coffee (7.8 µg/kg), doing the math, you'd have to consume the brew from 150 g of ground coffee per day. That's about half a standard-sized tin of coffee. Per day. If you drink that much coffee, shame on you.
• The 3rd study (the one rumtscho linked to, not cited by the blogger/con artist) looked at Aflatoxin, not Ochratoxin, which actually is regulated by the FDA at a maximum of 20 ppb. This study also showed approximately a 50% incidence rate after roasting, with the highest concentration of AT being 16 µg/kg for decaf (less with caffeine). So that means with any random cup of coffee you have up to a 50% chance of consuming an amount of AT that's still well below the FDA limit - that's very nearly zero risk.
• None of the studies test the rate of mold growth on beans while in storage under various conditions (temperature, humidity, etc.), so we can't comment on what happens in storage. So I guess if you want to really be on the safe side, only buy as much coffee as you think you can use in a week or two.

Conclusion:

Don't believe everything that people tell you - especially people with something to sell. Unless you're drinking gallons of coffee a day, brewed coffee is perfectly safe.

My university has access to the study @w00t linked in a comment here, so I thought I'll provide a summary of their findings.

1. Do green coffee beans contain aflatoxins? They found that yes, coffee beans naturally grow molds which produce aflatoxins. Molds and toxins were isolated from 17 out of 30 samples of green coffee beans they purchased from local markets.

2. Do roasted coffee beans contain aflatoxins? Yes, 22 out of 30 samples had molds and aflatoxins. The levels were lower than in green beans (about 30% less).

3. Does roasting reduce aflatoxins? They tried three types of roasting (oven, microwave and traditional). All methods roughly halved the aflatoxins, with traditional roasting resulting in the highest reduction (55.9%). The difference between methods was very small, ranging from ~45% to ~55%.

4. Does caffeine affect aflatoxin growth? They put caffeine and aflatoxin-producing molds in a mixture of sugar, yeast, and water, and waited. The molds grew with only half the speed of molds in the same mixture without caffeine added. They couldn't detect any aflatoxins in the mixture itself, but say this could be because they started with small amounts of mold. (Their measurement method is sensitive enough to detect tenths of micrograms per liter).

Conclusion: You can't get rid of mold and their byproducts (aflatoxins) in your coffee, but you can reduce them somewhat. If you insist on that, use freshly roasted coffee, no decaf. Be aware that the study doesn't give an answer if brewing coffee with moldy beans results in aflatoxins in your coffee. So you can't use it to arrive at a recommendation for safe coffee-drinking habits. Change them if you want to, but be aware that it will be a speculation. The question whether the alpha toxins are dangerous to human health, or which concentrations can be considered absolutely safe, is not researched in this study. Also, they found that while changing the roasting method does have an effect on the mold present in the beans, the difference was very small - so even if it has negative effects, I doubt that you can avoid them by changing the roasting method.

Perhaps we should re-direct this conversation to be closer with the OP's intent. The OP's question is:

"if this is a real problem and if there are ways to avoid it besides buying from them"

The first question can be paraphrased as "Do mycotoxins present in brewed coffee affect mental and physical performance enough that I should spend extra money to buy mycotoxin-free beans?".

First off, the question is highly subjective - is a potential increase in mental performance worth the extra money to the OP?

There are no studies on is whether the level of mycotoxins present in coffee has any measurable effect on a person's mental and physical performance. Asprey has a theory based upon personal experience, therefore they may be worth something, but should also be taken with a grain of salt. The lack of studies on this does not mean Asprey is a fraud or a con-artist, only that his assertions should be taken for what they are - personal experience. His opinions should not be dismissed out-of-hand.

We therefore have to break the question down. Does mold exposure impact mental performance?

As far as I know, there are no easy answers here, but this study does imply a link between mold exposure and mental performance:

https://www.atlanticlegal.org/pdfs/baldo.pdf

Second, does the level of mold / mycotoxins present in coffee affect mental performance? There are no studies about this, so your only source will have to be the personal experience of people trying this for themselves (aka Asprey and his readers).

Separately, the moderators and other contributors have made it clear that the mycotoxins present in coffee (beans or brewed) fall under the FDA's limits. However, Asprey's blog and assertions are about maximizing mental & physical performance. There may very well be a different threshold between what the FDA considers a "safe" level of mycotoxins, and the level of mycotoxins capable of affecting your mental performance. It would be illogical to conclude that the two thresholds are the same. Keep in mind that the degree of change Asprey is likely talking about may be the difference between getting an A+ vs. an A on whatever measure you consider to be relevant.

In short, there are no hard & fast answers to the OP's question because no relevant studies exist. We can safely say that yes, mycotoxins are present in coffee. Do said mycotoxins affect mental performance? Unknown, but it is supported / suggested by anecdotal evidence. Is anecdotal evidence sufficient for the OP to spend extra money on coffee beans? This is the real question.