Soylent’s new snack bar, packing 12.5 percent of your daily nutrients, supposedly “makes the afternoon slump a thing of the past.” But that may only be true if that “slump” doesn’t involve you over a toilet.

According to a discussion on Soylent’s website and several Reddit threads, customers say that some of the bars caused them gastrointestinal distress, including nausea, vomiting, and diarrhea. On the Soylent thread, user Raylingh has tallied 33 reports since September 7, just two months after the company started making the bars. Generally, customers say that stomach problems arise a few hours after eating a bad bar and pass within a day or two with no other symptoms. These shared illnesses easily meet the description of food poisoning, and many users have ruled out the possibility of food allergies, noting that they had eaten the bars and other Soylent products in the past with no problems.

The reports could become a sticky mess for the bars’ maker, Rosa Labs, which made a splash two years ago with its first Soylent product, a meal-replacement drink. The company quickly tried to minimize the issue, noting the small number of reports. Rosa Labs aggressively defended its quality control after extensive internal testing. In an official statement, the company said: “After these reports, we have retrieved remaining bars from our consumers and have personally consumed many of the remaining bars without adverse effects. We have also sent them for further microbiological testing and all tests have come back negative. Based on this we remain very confident in the safety of the bars.”

A source with knowledge of Soylent’s production said that the company is spending tens of thousands of dollars on testing and has investigated all ingredients for potential contamination. The company’s leading theory thus far is that some customers have a sensitivity or intolerance—rather than an allergy—to an ingredient in the bars. Those elements include algal flour, a sugar from beets called Isomaltooligosaccharide, and vitamins. However, the bars’ soy and the artificial sweetener, sucralose, are most suspect of causing an intolerance.

Unlike an allergy, which is when the immune system misidentifies a component of food as toxic or infectious and mounts a full-scale response, an intolerance is when someone has digestive trouble not involving the immune system. Symptoms of a food intolerance are limited to stomach problems, and these develop slowly (i.e. over a few hours) compared with those of an immediate allergic reaction. Also, unlike an allergy, which can be triggered by trace amounts of a food, an intolerance may only cause noticeable problems after eating a sizable serving.

Sources tell Ars that the soy in the bars is a prime suspect for causing such an intolerance because the bars include soy protein from three different sources and they may not get mixed evenly as the bars are made. Those three soy protein products—two of which aren’t included in other Soylent products—are derived using different processing methods, which could potentially introduce troublesome components. Thus, if a few bars end up with higher levels of one soy protein that contains a sensitizing component, it could be enough to trigger stomach problems for some consumers. The company is said to be looking into the matter.

Soylent sleuths

Still, in the month since users began reporting their illnesses, several other theories have been tossed around online.

Raylingh and others on the Soylent thread have been tracking the batch numbers that included suspect bars. Several have noted problems with boxes labeled 14JUL17 F3 1966, leading some users to wonder if a particular batch or ingredient was bad on a particular production day. If so, a simple recall could put the issue to rest. However, knowledgeable sources say that the reports to the company have implicated several batches across different production days, making a recall unlikely to settle the issue.

Users have also speculated that some bars may have gotten hot and spoiled during distribution and handling. Some reported sticky yellow residue on the inside of packaging. Yet, sources say that heating wouldn’t cause spoilage, and any residue that might appear under various conditions would be harmless.

Soylent reported that it will refund and collect all leftover bars from customers who have gotten sick. But on the forums, a few customers reported that the company wasn’t interested in collecting their bars.

Reporters at BuzzFeed flagged the Food and Drug Administration’s inspection record of the manufacturing facility where the bars are produced, Betty Lou’s, Inc., in McMinnville, Oregon. Soylent says that the facility is inspected annually by the FDA and its own independent food safety inspectors. The latest inspections were in March of this year, the company said. However, BuzzFeed noted that an online database of FDA inspections recorded the last inspection in 2014. Sources speculated to Ars the database may not be up to date. Ars reached out to both Betty Lou’s and the FDA about this discrepancy, but neither has responded. The FDA’s website notes that: “this database does not represent a comprehensive listing of all conducted inspections and should not be used as a source to compile official counts.” The agency may withhold information if enforcement actions are being planned.

Some users plan to report, or have reported, their illness to the FDA, which collects such complaints and feeds them to district branches that make a call on whether to investigate a local manufacturer. For its part, Soylent says it will continue to investigate on its own and will refund and collect questionable bars. So far, the company says that the number of complaints per bars sold is only 0.03 percent. However, the company wouldn't elaborate on just how many complaints they've received.