Why Does Psyllium Husk Have a Cancer Warning? An RD Explains

Why Does Psyllium Husk Have a Cancer Warning? An RD Explains

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Disclaimer: None of the information in this article constitutes medical advice, and is just the opinion of the writer(s). We recommend that individuals follow their doctor’s guidance in regard to psyllium husk supplementation.

Psyllium husk is one of the most popular categories of fiber supplement. It’s cheap, widely available, and psyllium husk brands often claim that it has potential benefits to cholesterol levels and digestion.

But why do some psyllium husk products carry a cancer warning? Does psyllium have any research-backed benefits? Are there risks to using psyllium husk beyond the cancer warning? And which psyllium husk brand is the cleanest?

In this article we’ll answer all of these questions and more as we explain why some psyllium husk supplements carry a cancer warning and why it may not matter as much as one would think.

We’ll also review research-backed health benefits of psyllium husk fiber and share our take on whether it’s superior to other forms of supplemental dietary fiber.

We’ll feature a YouTube video highlighting one of the unique risks of psyllium husk, and give our recommendation for the cleanest psyllium husk brand.

Why Do Some Psyllium Husk Brands Have a Cancer Warning?

California has a law called Proposition 65, commonly referred to as “Prop 65,” which requires companies to disclose if their product(s) contain contaminant levels above certain thresholds.

If a psyllium husk brand contains levels of a heavy metal toxin (like lead or arsenic) above Prop 65 limits, the brand is required to publish a cancer warning on its physical product label.

However, it’s important to make a few distinctions to contextualize this information.

     1) Nearly every plant grown outdoors contains trace levels of heavy metals due to environmental pollution

We haven’t come across any clinical evidence that psyllium husk is uniquely susceptible to high heavy metal levels. Everything from rice to fruit can contain heavy metals due to absorption from the soil.

What matters is the actual level of the heavy metal, and unfortunately most food product manufacturers fail to publicly share this information.

     2) We haven’t seen any evidence in research studies that psyllium husk directly causes cancer

Psyllium is a popular type of food that has been studied in many clinical trials. An animal study published in the Nutrition and Cancer journal found that psyllium supplementation actually reduced colon cancer rates.

A 1996 clinical trial found that fiber supplementation generally may decrease breast cancer rates.

Overall, psyllium seems likely to reduce cancer rather than to cause cancer, because the beneficial effects of the compound are likely to outweigh any negative effects from heavy metal contamination. 

However, it’s still important to reduce heavy metal consumption as much as possible. So which psyllium brands were the most and least contaminated based on third-party testing? We’ll review in the next section.

Which Psyllium Brands are Cleanest?

ConsumerLab is an independent, third-party company that tests supplements off-the-shelf (which means they don’t accept samples from brands which can increase bias). 

ConsumerLab reports on not only the label accuracy (does this supplement actually contain what its label claims?) but also the contaminant levels of popular supplements, and they published an entire review of psyllium fiber supplements.

Yerba Prima Psyllium Whole Husks contained the least lead per 5 grams (g) whole psyllium product, at only 0.4 micrograms (mcg) of lead.

Interested consumers can check out Yerba Prima Psyllium Whole Husks at this link to the brand’s official Amazon listing.

NOW Psyllium Husk Caps contained the least lead per 5 grams (g) capsule psyllium product, at 1.3 mcg.

Interested consumers can check out NOW Psyllium Husk Caps at this link to the brand’s official Amazon listing.

The product with the most lead (by far) based on ConsumerLab testing was Kate Naturals Organic Psyllium Husk Powder, which contained 11 mcg per 5 g product serving, or 27.5 times the amount in Yerba Prima.

But are there risks to using psyllium powder that don’t exist for other types of fiber powder? We’ll review in the next section.

Can You Overdose on Psyllium?

A popular YouTube creator named “Chubbyemu,” who’s a doctor, has a video documenting what can happen if you take far too much psyllium husk fiber in one sitting. It’s an interesting and engaging video (even though it’s not a real risk for most users) and has over 6 million views:

Does Psyllium Have Proven Health Benefits?

As stated throughout this article, psyllium has been studied in hundreds if not thousands of clinical trials, and has some well-documented health benefits.

Weight loss was reported in overweight patients supplementing with 10 g of psyllium daily, according to a clinical trial published in the Complementary Therapies in Medicine journal.

After 12 weeks of psyllium husk supplementation, participants lost an average of 4.41 pounds.

Constipation relief is another clinically shown benefit of psyllium, and whole psyllium husk is a much natural and healthier option than commercial laxatives in our opinion, which often contain a number of questionable additive ingredients like artificial sweeteners.

Improved gut health is another research-backed benefit of psyllium supplementation, as we documented in our analysis of Colon Broom ingredients. The effective daily dose for gut health support was reported as 21 g in the meta-review we cited.

Clearly psyllium husk has a number of health benefits, as does fiber supplementation generally (either from whole foods or supplements).

Americans fail to consume nearly enough fiber for optimal health, according to a 2017 medical review, and this can have effects on everything from blood sugar levels to weight to proper bowel function.

We urge consumers to be wary of any websites claiming that psyllium husk is dangerous or causes cancer, because the overwhelming clinical evidence suggests to us that it has more benefits than downsides.

Our Clean Gut Health Picks

MBG Organic Fiber Potency+ is our top fiber pick.

MBG Organic Fiber Potency+ contains 100% soluble fiber, which was described as "one of the most important nutrients for the gut microbiota" in a clinical review published in the Molecules journal.

Ritual Synbiotic+ is our top value probiotic pick.

It contains prebiotics, probiotics and postbiotics, and costs under $1.50 per serving at the time of updating this article.

Probiotics "can improve in the immune, gastrointestinal...health systems in healthy adults" according to a 2019 medical review.

VSL#3 is our top premium probiotic pick.

This probiotic supplement has been studied in 25 clinical trials, and a 2020 meta-study on VSL#3 concluded the following:

"...many studies demonstrated that VSL#3 has a beneficial effect on obesity and diabetes, allergic diseases, nervous systemic diseases, AS, bone diseases, and female reproductive systemic diseases."

All of the products recommended in this section are entirely free of ingredients that we consider to be unhealthy.

Stay up-to-date on our research reviews


Psyllium husk may contain a cancer warning based on a California ruling, but this type of warning is not unique to psyllium husk. Any food or supplement containing contaminants like lead may have this warning on their label, and we haven’t come across any clinical evidence that psyllium is higher in environmental contaminants like heavy metals than any other food product or supplement.

Based on our review of clinical studies, the health benefits of psyllium husk supplementation (like reduced body weight in overweight individuals and gut and colon health support) seem to vastly outweigh any potential downsides.

ConsumerLab tested psyllium supplements and found that a brand called Yerba Prima contained the lowest levels of lead. We linked to the Yerba Prima Amazon listing in this article.

NOW Foods contained the lowest levels of lead for a capsule formulation.

We hope that in the future, legislation on cancer warnings is based on actual test results for contaminants, rather than potential for contamination based on product category, because this would be much more useful (and less confusing) to consumers.