Herbal supplements were supposed to make them healthier. Instead, they got sick

Fernanda Thompson was a healthy 40-year-old when she began taking turmeric in 2020. Online, people were saying the pungent yellow spice could make everyone a little bit healthier. So she began putting half a teaspoon, about 2.5 grams, into her morning smoothie, hoping to reap the benefits of curcumin, the compound responsible for turmeric’s anti-inflammatory, anti-cancer, anti-oxidant halo.

“It was Covid time,” says the Florida resident, who is a stay at home mom, and she wanted to boost her immunity. “I was healthy. And then I guess I tried to be healthier,” she says.

In 2021, a routine blood test revealed Thompson’s white blood cell count was oddly low. She was referred to a hematologist and an ultrasound showed an enlarged liver.

Thompson felt physically fine, but began monitoring her health more closely with both her doctor and a hematologist, getting regular blood tests that showed consistently low white blood cells. She feared with every follow-up that her doctors would make a serious diagnosis, like leukemia.

In 2024, after three years of health anxiety, Thompson came across a blog post by gynecologist Dr Jen Gunter titled “The Trouble with Turmeric.” In it, Gunter challenges the popular belief that turmeric is a completely safe, natural panacea. She points out that some of the most frequently quoted data on turmeric’s benefits are derived from discredited and low-quality studies. When you take turmeric, you are “paying to play the liver injury lotto with no quality data to prove that the product can help you meaningfully”, Gunter writes, citing research showing that to some people, turmeric can be toxic to macrophages, a type of white blood cell, and may contribute to iron deficiency.

Attributions of causality between blood abnormalities or organ damage and supplements or natural medicines are notoriously difficult for general practitioners to provide, due to factors including the variable composition of supplements and their lack of research and regulation. However, there is data linking turmeric to liver injury – as of 2022, at least 10 cases in the US and 18 in Australia, including one fatality.

Thompson immediately stopped taking turmeric.

“Six months later I did my blood test again and my white blood cell count was normal,” says Thompson, who ended up paying $1,275 out of pocket for her tests. Her doctor said they would never know if the cause was turmeric or something else, Thompson remembers, “‘but don’t take it again.’”

Herbal supplements can contain compounds that overwhelm the liver’s normal detoxification, immune and metabolic functions. To experts who have dedicated their careers to studying herbal supplements’ effects on the liver, Thompson’s story is a familiar one – though cases of suspected toxicity from these substances don’t always end so well.

“It’s more common now to see some severe cases of liver injury end up in the hospital, or even some that need to be addressed with a liver transplant,” due to patients taking herbal supplements, says Dr Alisa Likhitsup, a gastroenterology and transplant hepatologist at the University of Michigan, which operates a leading liver research center.

Supplement-related liver injury is not necessarily tied to product dosage or contamination, though both can be contributing factors in liver injury and require further research, says Dr Robert Fontana, a leading global authority on drug-induced liver disease and professor of medicine at the University of Michigan. (For instance, herbal medicines have a well-documented problem with heavy metal contamination.) Yet, purity and quality aside, the herbal compounds themselves can cause issues. These effects can occur even with a small dose of a supplement, though higher doses can elevate the severity and speed of a bad reaction.

And it goes beyond turmeric. In 2024, Likhitsup’s research estimated that 15.6 million Americans take compounds known to be potentially toxic to the liver on a daily basis, some of the most common being turmeric, ashwagandha and green tea extract. In 2023, the Council for Responsible Nutrition estimated that 74% of Americans take dietary supplements. Supplements with the highest volume of advertising, increasingly by wellness influencers online, end up most popular, and most studied, Likhitsup says.

But “there’s something like 100,000 herbal and dietary supplements out there”, says Fontana. “Most of them don’t cause harm that we know of … but none of these things are tested or validated or regulated,” he says. “I don’t see that the current administration is interested in more regulations, either.”

Fontana has been studying herbal toxicity since 2004, when he founded the multi-institutional Drug-Induced Liver Injury Network (DILIN), an NIH-funded research network that studies liver injuries caused by medications and supplements through nationwide patient registries of more than 3,000 people. Doctors refer patients with apparent drug-induced liver injury to Fontana and DILIN, who carefully assess cases to rule out other possible causes such as hereditary liver disease, antibiotics or other medications known to affect liver function, like acetaminophen.

“When we look at it over time, the proportion of cases [of liver injury] attributed to herbal and dietary supplements is definitely going up,” says Fontana. Herbal supplements are a factor in 20% of the cases DILIN, with some research suggesting that number could be as high as 43%. A 2022 study found that, over the last 25 years in the United States, cases of drug-induced liver failure requiring waitlisting for liver transplantation due to herbal dietary supplements have increased eightfold.

Only a small fraction of those who take supplements experience liver issues as a result – there are no concrete numbers, but one in several thousand is “a best guess”, according to Dr Marwan Ghabril, a professor and hepatologist at the Indiana University School of Medicine, and lead author of the study. But among those, about 10% go through “worst case scenario” outcomes, meaning they need a life-saving liver transplant or die.

Herbal supplements are only becoming more popular, reflecting trends like health consciousness and the perceived safety of natural products compared with pharmaceuticals. Market research estimates dietary supplements were a $74.3bn global industry in 2024, expected to reach $170bn by 2034. “When you magnify [herbal supplement use] up by the whole US population, it’s quite alarming,” says Fontana.

“You should always consult a doctor before taking supplements,” says Dr Qianzhi Jiang, a registered dietitian based near Boston. Most supplements are unnecessary; proper nutrition is best achieved through diet, with exceptions for people who are pregnant or have vitamin deficiencies and require specific supplementation.

“What works for another person may not work for you … The mentality of relying on supplements to achieve a better and longer life is unscientific,” says Jiang.

But why do some people get sick from taking supplements that others may find harmless or even beneficial?

Fontana’s prevailing theory is that genetics are mostly to blame for unpredictable adverse reactions to supplements; researchers call them “idiosyncratic” liver injuries. It seems that when you take a herbal supplement, you’re playing Russian roulette with your genetic ability to tolerate it, he says.

“We do find unique genetic susceptibility factors among people who get liver injury,” says Fontana. Depending on their genetic makeup, someone may tolerate green tea extract without issue, but even a small amount of turmeric could trigger harm, and vice versa. The risks vary from person to person.

In mild cases of herbal supplement-related toxicity, people “may not necessarily register” that anything is affecting their health, notes Ghabril. But in more problematic cases, abdominal pain, fevers, fatigue and jaundice can result. Nausea and itching may also be a problem if the person’s bile acids become elevated, he says.

In severe cases of injury, symptoms can quickly escalate. Earlier this year, two unrelated cases – Robert Grafton and Katie Mohan, both New Jersey residents in their 50s – were hospitalized with drug-induced liver injury linked to turmeric supplements, drawing increased attention to potential harm.

Naveen Kathuria, 46, a former lawyer and health tech CEO based in New York City, had no known health issues when he began taking daily 150mg ashwagandha supplements purchased from Amazon in June 2024.

Kathuria was influenced by what he calls a “subculture of optimization and longevity” in the tech industry; he was hoping the pills would help him with “sleep, stress, and workouts”. Meta-analyses show ashwagandha may be beneficial for reducing stress, though higher-quality studies are scarce.

By September, Kathuria began to feel uncharacteristically lethargic. A blood test showed his liver enzymes were so elevated that his doctor ordered a repeat test to rule out error. He stopped taking the supplements immediately, but by the end of the month he was jaundiced, rapidly losing weight, vomiting, itching and unable to sleep. His doctor – who Kathuria says was weighing plasma transfusions and a liver biopsy – advised against travel, but Kathuria chose to return to Michigan to be with family who could help care for him.

There, he connected with Fontana, who confirmed the severity of his condition. “There’s very few physicians out there that are well-educated on drug-induced liver injury and the harmful impact of supplements,” says Kathuria.

Fontana recommended time, rest and no further supplements, rather than invasive procedures. Kathuria says he has since made a “full recovery” and returned to work.

Both Kathuria and Thompson emerged from their health scares wishing more people knew that herbal supplements, however benign they seem, can carry substantial risks. “The fact that it’s a plant doesn’t mean it’s effective or safe,” Thompson says.

Kathuria says he has always been careful about the food he eats. “But I never really thought through how supplements can impact your body,” he says. He doesn’t take supplements anymore.