How Often Do Supplements Contain What They Claim?

Quality Report

We tested 15 competitive supplements for C15:0…

Here at Science Says!, we enjoy sharing the good-science news that keeps landing on C15:0. Which is pretty darn easy, since an average of one new peer-reviewed study has been published per week around C15:0 benefits over the past year. This week, we report the results of our own mini study using a qualified and independent third party to test C15:0 levels in fifteen (non-fatty15) supplements claiming to have between 100 mg to 400 mg of C15:0. While we love being positive, this study had a whole lot of negatives. But don’t worry, Science Says! readers. We end on a very positive note.

Fifteen (non-fatty15) C15:0 supplements

Given the growing science supporting C15:0’s health benefits, it is not surprising that an increasing number of (non-fatty15) C15:0 supplements have entered the market. We purchased fifteen of these supplements online between July 2025 and January 2026 and submitted them immediately to the Eurofins Food Integrity & Innovation team to test their C15:0 levels.

• Four supplements claimed to have 100 mg C15:0 per serving
• One claimed to have 200 mg C15:0 per serving
• Eight claimed to have 300 mg C15:0 per serving
• Two claimed to have 400 mg C15:0 per serving

Importantly, Eurofins is an ISO-17025 accredited laboratory, which means that it meets the highest standards in supplement ingredient testing. It’s also a lab we use to verify fatty15’s C15:0 content.

The results

Of the fifteen (non-fatty15) supplements tested by Eurofins, eight (53%) had no detectable C15:0 and six (40%) had between 3% and 50% of C15:0 claimed on the labels. One had 177 mg (89%) in its product claiming to have 200 mg of C15:0 per serving. Given that most quality studies cut off supplements that aren’t within 10% of claimed amounts, this would mean that none of the 15 tested (non-fatty15) C15:0 supplements met the requirements of adequate C15:0 levels.

In contrast, all fatty15 supplements contained the actual amount of C15:0 that we claim to have on our label.

A disturbing trend for fraudulent supplements

Unfortunately, these results from our mini study are consistent with peer-reviewed studies that similarly tested supplements for other claimed ingredients. Cohen et al. tested 57 sports supplements for specifically claimed botanical ingredients and found that 40% did not contain detectable levels of the labeled ingredient. Among supplements that did have the ingredient, only six (11%) had the ingredient amount within 10% of what the label claimed it to have.

Crawford et al. tested 30 dietary “immune support” supplements for their ingredients and found that 17 (57%) had inaccurate ingredient labels. Of these, 13 had the wrong amounts of claimed ingredients and 9 had added active ingredients that were not claimed in the label. The authors in this study concluded that when it comes to dietary supplements, “the public has a right to know that they are buying what is stated on the label.”

SuppCo, a leading supplement quality testing company, tested 44 best-selling online supplements containing creatine, NAD+, urolithin A, and berberine. Same story… 22 (50%) failed to meet active ingredient label claims. Worse yet, 20 of those 22 failures had 0 to 3% of the ingredient it claimed to contain. This study also found that:

• All foreign-registered products failed testing, almost all of which were from China.
• All products with no brand-owned website failed testing.
• Failing products were 38% cheaper than real products.

Supplement shopping tips

So, when shopping for supplements, beware of:

• Foreign-registered supplements, especially those from China.
• Supplements that don’t have a brand-owned website.
• Supplements that are substantially cheaper than trusted brands.

On the positive side, use trusted third-party testing sources such as SuppCo to see how your supplement stack (current or of interest) stacks up against rigorous, independent testing.