A New (Old) Problem With Avocado Oil

By Wayne Persky

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When a label says avocado oil but the bottle contains soybean oil, microscopic colitis (MC) patients pay a price that goes well beyond the extra money spent at the checkout.

Many of us with MC have switched to avocado oil products in recent years, drawn by the promise of a clean, gut-friendly fat that avoids the seed oils we've learned to be cautious about. We pay more for chips, mayonnaise, and salad dressings labeled "made with avocado oil." We read the ingredient list, see avocado oil listed as the only oil, and feel confident we're making a safe choice.

A new study from the University of California, Davis suggests that confidence is very likely misplaced, and for MC patients sensitive to soy, the consequences can be more than financial.

What the research found:

Researchers at UC Davis purchased 54 packaged food products that listed avocado oil as the only oil ingredient — chips, mayonnaise, and salad dressings, and subjected them to chemical analysis. The results were stark. 89% of the products showed signs of adulteration with cheaper oils, most commonly soybean oil. One sample appeared to contain essentially no avocado oil at all (Godoy, 2026, July 21).1

The findings broke down by product category in a way that should concern anyone relying on these labels. Among chips labeled as made with avocado oil, 93% were adulterated. Among mayonnaises, 71% failed — and when U.S.-made products were examined separately, that figure climbed to 100%. Every single salad dressing product tested was adulterated (Quinton, 2026, July 15).2

Critically, price offered no protection. Products at the higher end of the price range were no more likely to be authentic than cheaper ones. Consumers paying a premium for what they believed was a cleaner oil were being misled just as thoroughly as anyone else.

For comparison, the same researchers tested 20 packaged food products made with olive oil. Only one showed signs of adulteration. As lead researcher Selina Wang, a professor of food science at UC Davis, put it: "So this is largely an avocado oil product problem."

Why this isn't a new problem:

This latest study is actually the third time in six years that UC Davis researchers have documented serious authenticity problems in the avocado oil market. A 2020 study found that 82% of commercially bottled avocado oils were either rancid or adulterated with other oils. A follow-up found similar problems with private-label products. What the new 2026 research confirms is that the fraud didn't clean itself up as the market grew — it expanded right alongside it, moving from bottled oils into the rapidly growing category of packaged foods that trade on the avocado oil label.

The economics make the incentive obvious. Pure avocado oil costs roughly $4 to $5 per pound. Soybean oil costs $0.50 to $1.50. The label premium that consumers pay for avocado oil products is real. The oil itself often isn't.

Investigators haven't been able to pinpoint exactly where in the supply chain the substitution typically occurs, whether at the level of the oil supplier, the ingredient processor, or the food manufacturer. What's clear is that the problem is systemic and that it doesn't leave a detectable trace on the label.

Why MC patients face a specific risk:

For the general public, buying adulterated avocado oil is primarily a consumer fraud issue — paying premium prices for an inferior product. For MC patients, it can be something considerably more serious.

Soy sensitivity is one of the most common food intolerances in the MC community. According to data shared by members of the Microscopic Colitis Foundation discussion forum, more than half of us are sensitive to soy proteins and related compounds. This figure is consistent with the broader pattern of MC-associated food sensitivities, which also include gluten and casein, and which appear to arise from the increased intestinal permeability (commonly called "leaky gut"), that accompanies the disease. Once the gut barrier is compromised, food proteins that would ordinarily be processed normally can cross into the intestinal wall and trigger an immune response.

Soybean oil presents a somewhat different issue than soy protein. Highly refined soybean oil theoretically contains very little soy protein and is sometimes considered safe for people with soy allergies. However, research on this point is not fully settled, and MC patients react to soy through immune pathways that may not follow the same rules as classic IgE-mediated soy allergy. Interestingly, there is now direct research evidence that soybean oil itself, independent of its protein content, may promote intestinal inflammation through a separate mechanism.

The linoleic acid problem:

Soybean oil is composed of up to 60% linoleic acid, an omega-6 fatty acid. A research team at UC Riverside found that mice fed a diet high in soybean oil were significantly more susceptible to developing colitis. The mechanism involves linoleic acid's effect on the intestinal endocannabinoid system — it reduces levels of beneficial endocannabinoids in the gut, weakens the intestinal barrier, decreases beneficial bacteria, and promotes colonizing by-invasive E. coli, a strain of bacteria that has been linked to IBD in humans (Pittalwala, 2023, July 3; Deol, et al., 2023).3, 4

Americans already derive far more of their daily energy from linoleic acid than their bodies need — as much as 10%, against a requirement of just 1 to 2%. For MC patients who are already dealing with a compromised intestinal barrier, adding a hidden source of high-linoleic-acid oil through products that are supposed to be free of soybean-oil, compounds a risk that most of us aren't even aware we're taking.

Avocado oil, by contrast, is composed primarily of oleic acid, a monounsaturated omega-9 fat with a very different biological profile. It doesn't carry the same pro-inflammatory omega-6 overdose that makes soybean oil a concern for gut-sensitive individuals. When we choose avocado oil products, that difference is part of what we're paying for. The adulteration findings suggest we're usually not getting it.

What can we do about it?

The honest answer is that there's no easy solution. Short of having the oil in every product we buy independently tested, which isn't practical, we can't verify authenticity from a label alone, regardless of how confidently the packaging states "made with 100% avocado oil."

That said, a few approaches can reduce our exposure:

Bottled avocado oil from brands with documented third-party testing and supply chain transparency is more likely to be authentic than unverified packaged food products. If we're cooking at home with avocado oil, sourcing from a reputable bottled brand and preparing our own chips, dressings, and sauces gives us considerably more control than trusting a commercial product.

Among packaged foods, the adulteration problem appears worse in some categories than others. The UC Davis study found that salad dressings were uniformly adulterated and chips were nearly so. If we choose to buy these products at all, rotating brands and staying alert to any symptom changes after introducing a new product is a reasonable precaution.

For those of us who react to soy, the safest position, although frustrating, is to treat most commercially packaged "avocado oil" products with the same caution we'd apply to a product with soy listed on the label, at least until the industry develops and enforces meaningful authenticity standards.

Is the industry likely to correct the problem?

The Avocado Oil Manufacturers Association, founded in 2025, has acknowledged the authenticity problem and expressed intent to address it, pointing to the olive oil industry as a model. It took years of published research, public pressure, and eventually, coordinated industry standards, before olive oil adulteration rates dropped to the relatively low levels seen today. The avocado oil industry appears to be at an early stage of that same process.

In the meantime, the burden falls on consumers, as it usually does, to navigate a marketplace where the label and the contents of the package don't reliably match. For MC patients who are already working hard to identify and eliminate foods that trigger symptoms, discovering that a product we trusted has been silently adulterated with one of our most problematic intolerances is a legitimate health concern, not just a shopping inconvenience.

References:

1. Godoy, M. (2026, July 21). Is that food really made with 100% avocado oil? Likely not. MPR, Retrieved from https://www.npr.org/2026/07/21/nx-s1-5902084/avocado-oil-health-fraud-study

2. Quinton, A. (2026, July 15). That Avocado Oil Chip You’re Eating May Not Be Made With Pure Avocado Oil. University of California, Davis, Retrieved from https://www.ucdavis.edu/food/news/avocado-oil-chip-youre-eating-may-not-be-made-pure-avocado-oil

3. Pittalwala, I. (2023, July 3). Widely consumed vegetable oil leads to an unhealthy gut. University of California at Riverside, Retreived from https://news.ucr.edu/articles/2023/07/03/widely-consumed-vegetable-oil-leads-unhealthy-gut

4. Deol, P., Ruegger. P., Logan, G.D., Shawki, A., Li, J., Mitchell, J. D., . . . Sladek, F. M. (2023). Diet high in linoleic acid dysregulates the intestinal endocannabinoid system and increases susceptibility to colitis in Mice. Gut Microbes, 15(1). 2229945. Retrieved from https://pubmed.ncbi.nlm.nih.gov/37400966/