News exclusive: White mulberry leaf ID confirmed by Calif. university in fatality

An autopsy report linking the death of U.S. Rep. Tom McClintock’s wife to white mulberry leaf has raised more questions than answers among specialists in the nearly $60 billion-a-year dietary supplement industry.

Natural Products Insider has solved one piece of the puzzle: The identity of the scientific experts who confirmed a leaf fragment taken from the stomach of Loretta (Lori) McClintock matched the herb in question.

“In comparing this leaf fragment to fresh leaves and to our extensive library of pressed specimens, we determine that this leaf fragment is a match to Morus alba, the white mulberry,” Alison Colwell, a curator with The UC Davis Center for Plant Diversity at the University of California, Davis, wrote in a Dec. 29, 2021, letter to the Sacramento County Coroner’s Office. “The sample matches white mulberry specimens in all traits examined: upper and lower leaf surface texture, hairiness, venation pattern, intercostal tissue patterning, the frequency, size and shape of the stomata and the embeddedness of the veins relative to the plane of the leaf.”

Colwell said UC Davis Professor Dan Potter and Emeritus Professor James Doyle assisted her in identifying the white mulberry leaf. Natural Products Insider obtained the botanist report Friday through a public records request with Sacramento County.

The leaf taken from McClintock’s stomach, Colwell wrote, “was likely ingested when fresh.”

White mulberry leaf is generally safe with a long history of use, herbal experts said. Roy Upton, the founder and executive director of the American Herbal Pharmacopoeia, said white mulberry leaf has been shown to have anti-inflammatory activity in the gut, and research has demonstrated it is safe even when taken at high doses.

“White mulberry is not toxic," Colwell wrote in the botanist report to the Sacramento County Coroner's Office. 

It’s doubtful the leaf taken from Mrs. McClintock’s stomach derived from a dietary supplement product, according to industry experts. While it’s possible the plant material derived from a tea, it couldn’t have come from a dietary supplement pill because the herb would be ground up into a powder and unrecognizable, Upton said.

While some teas are sold as herbal supplements, American Botanical Council (ABC) Chief Scientific Officer Stefan Gafner has not identified any mulberry leaf teas sold as supplements in the U.S.

The notion “that a fragment in the stomach could be from ingesting a mulberry leaf supplement does not make sense to me,” he said in an email. Gafner added tea drinkers don’t typically ingest the contents of their tea bag, or if it’s loose tea, the leaf fragments used to prepare the herbal remedy.

It remains unclear how the coroner’s office concluded McClintock’s death was caused by “dehydration due to gastroenteritis due to adverse effects of white mulberry leaf ingestion.”

Sacramento County spokeswoman Kim Nava declined to comment on the investigation.

Asked whether FDA is investigating McClintock’s death, FDA spokesperson Lindsay Haake said her agency does not discuss ongoing or possible investigations other than with the party involved.

FDA has received only two adverse event reports (AERs) associated with white mulberry leaf supplements in its CFSAN Adverse Event Reporting System between January 2004 and March 2022, according to a review by Rick Kingston, co-founder of SafetyCall International, which specializes in product safety and clinical toxicology. One of the cases involved a 77-year-old man who took 31 different products, only one of which was a white mulberry leaf supplement.

“That’s hardly a smoking gun for mulberry, especially for that one particular case,” Kingston said in an interview.

Kingston, who reviews many autopsy reports, was suspicious of the conclusions in McClintock’s autopsy report, saying he couldn’t identify anything in the document to lead to the conclusion that white mulberry leaf caused gastritis.

“You’ve got to have some reasoning behind why you think that’s the case,” he said.

FDA did not provide a direct answer when asked for this article whether the agency had any concerns about white mulberry leaf, based on AERs received and its review of the scientific literature.

“The FDA monitors and carefully reviews information about dietary supplements from a variety of sources, including product complaints, adverse event reports and other information, such as data from the American Association of Poison Control Centers’ National Poison Data System,” Haake said. “The agency is committed to doing everything within its resources and authorities to identify and remove unsafe and illegal products from the market, and we continue to work collaboratively with our stakeholders to help ensure that dietary supplements are safe, well-manufactured and accurately labeled. If the FDA determines that a dietary supplement is unsafe or otherwise violates the law, the agency takes action as appropriate, based on public health priorities and available resources.”

Bill Gurley, principal scientist with the National Center for Natural Products Research at the University of Mississippi’s School of Pharmacy, called the coroner’s report “bizarre.”

“I’ve looked at a lot of botanical toxicology reports over the years, and in the pantheon of those reports, I would say mulberry ranks right up there as among the top three or four safest botanicals that you’d ever run across,” Gurley said in an interview.

“This is probably the one and only adverse event death that’s ever been linked to white mulberry leaf. We’re talking one out of hundreds of years of use,” he added.

Apart from the identification of a partially digested leaf, Gurley further wondered whether the coroner’s office conducted any other tests that directly linked white mulberry leaf to McClintock’s death. He said a toxicological assessment looking for specific phytochemical markers of white mulberry in blood samples could help to get a clearer picture.

Loretta McClintock, 61, died on Dec. 15, 2021, according to public records from the Sacramento County Coroner. Rep. McClintock shared the news a few days later in a Facebook post, writing, “Our family’s darkest day and most terrible nightmare has come. Lori is gone.”

It wasn’t until Aug. 24, 2022, that Kaiser Health News broke the story that Mrs. McClintock passed away after ingesting white mulberry leaf. The revelation was widely reported in national and international media.

Duffy Hayes contributed to this report.