Your liver is your main detox hub. It works hard to remove toxins and built-up metabolic waste from your body before they do much harm. Many natural supplements support liver health, but a number of them do the opposite. Read on for a complete list of foods and supplements you should avoid to prevent liver damage.
32 Herbs and Supplements that Are Bad for Your Liver
I’ve already talked about supplements and foods that are good for the liver. In this post, I’ll hone in on the ones you should avoid.
Natural medicine can go a long way in improving liver health, even in people with liver disease. It works even better for prevention, so the sooner you know what to take and what to avoid, the better.
Knowledgeable practitioners know exactly which supplements to avoid prescribing to people at risk of liver problems. But if you’re experimenting on your own, study this list carefully. Some compounds are downright bad for your liver and you should make sure you’re not inadvertently taking them.
According to a study of around 25 patients, this herb can damage the liver, lead to severe injury, and even death .
The processed roots of fo-ti might be less toxic, according to animal studies. But I would still recommend avoiding this herb altogether, especially if you already have liver problems .
2) Cassia Cinnamon
3) Peppermint oil
Chronic treatment with peppermint oil resulted in some degree of liver impairment in animals, although no other parameters of liver function were impaired .
In one study, high doses of peppermint oil increased bile and markers of liver damage (ALT) on rat liver and cultured human liver cells over a long period of time .
Low doses probably won’t do much harm, but it’s still better to stay on the safe side and avoid oral peppermint oil if you have liver problems.
In the US, kava kava is usually sold as pills. These pills may contain various toxic solvents.
Traditional kava kava drinks are prepared differently, after grinding the roots by chewing and spitting them out. Needless to say, this not an option for commercial preparations. It’s possible that enzymes in saliva inactivate kava kava’s liver-toxic compounds – or that something else in the process makes this herb less dangerous.
What’s worse, some people report using kava kava with alcohol, which strays from its traditional uses and can amplify its liver-damaging potential.
The studies that point to liver toxicity after kava kava intake included patients with a history of alcohol consumption. In other cases, kava kava was taken with other prescribed drugs. It still seems unfair to say that this herb is the culprit [9, 10].
Since the early 2000s, 11 cases of kava kava-related liver injuries have been reported, four of which resulted in death. As a result, kava kava was banned in Canada and a number of European countries .
There was one case of acute hepatitis associated with kava-kava in a 14-year-old girl. She recovered after a liver transplant .
All in all, it’s still unknown if kava kava itself causes much liver damage. But until more studies are out, people with liver problems are better off avoiding it.
5) High Doses of some Vitamins
Long term or high doses of niacin (time-release preparations) have led to liver failure or hepatotoxicity. It’s possible that niacin is transformed into NAD, which can damage the liver in excessive amounts [15, 16].
High doses of beta-carotene worsened alcohol-induced liver injury while lower doses were protective .
To sum it up, most vitamins are not harmful in normal doses. Avoid megadoses, especially of niacin and beta-carotene.
Not many studies speak to its liver-damaging effects. Still, there are enough data to recommend against it in people with liver problems.
In one patient, valerian caused acute hepatitis. In others, it caused liver damage. Lastly, high doses of valerian oil had toxic effects on rat liver and cultured hepatoma cells in one lab experiment [19, 12, 20, 6].
7) Saw palmetto
Saw Palmetto (Serenoa repens) preparations have caused cholestatic hepatitis in some patients .
Borage (Borago officinalis) seed oil has complex molecules called pyrrolizidine alkaloids, which are toxic to the liver. Their concentration must be lower than 200 ppt or 0.001% for the safe usage of this oil [24, 25].
9) Black cohosh
According to one study, two women developed acute liver necrosis after taking black cohosh .
In another case study, a 44-year-old female developed liver injury within a month of using black cohosh to resolve her hot flashes .
These cases are uncommon. If you’re taking black cohosh for hormonal problems, talk to your doctor about checking your liver enzymes regularly.
10) Red clover
In one study, oral administration of 60 mg of Red Clover (Trifolium pratense) in men increased liver transaminases by >30%, possibly due to high amounts of isoflavones .
According to another study, red clover might interact with Non-steroidal anti-inflammatory drugs, particularly aspirin, and cause adverse reactions. Such adverse events are common in herbal supplements that contain coumarin .
11) Gotu Kola
According to one study, three women (61, 52 and 49 years old) developed jaundice after taking Gotu Kola. All of them improved after stopping this supplement. Gotu kola also induced liver toxicity in one child [31, 32].
Hepatitis and cirrhosis have also been reported. Avoid this herb or use it with extreme caution .
12) Aloe vera
Liver injury associated with oral administration of Aloe vera was first reported in 2005. An injury typically arises between 3 and 24 weeks of starting oral aloe vera and is rare .
According to one report, three women (aged 55, 57 and 65) suffered acute hepatitis after taking aloe preparations for months. Liver enzymes returned to normal upon discontinuation of the oral aloe preparations .
Chaparral is a shrub that grows in California and Mexico. Clinical and animal studies reveal it’s toxic to the liver .
In one review reported 18 cases of illness after ingesting chaparral, with jaundice as the main sign of liver disease .
It’s probably ok in tiny amounts, as a spice, but avoid using too much of it.
Pennyroyal (Mentha pulegium) oil is also called spraw mint. It is said to be highly toxic, and studies have reported its toxicity to the liver – possibly due to the presence of pulegone, a highly poisonous compound .
Coltsfoot is a plant of the daisy family commonly used in folk medicine for lung problems. One baby developed reversible liver disease after being given coltsfoot tea , possibly due to its pyrrolizidine alkaloids.
Based on animal studies, coltsfoot is likely safe in adults at typical doses. Exercise some caution if using it .
17) Greater celandine
One person developed acute hepatitis after consuming a herbal preparation of Greater celandine .
More research is needed, but this herb is probably not that good for the liver.
In 1992, the germander powder containing capsules were banned from the French market after an epidemic of 30 cases of hepatitis .
19) Usnic acid
Daily oral intake of 300 – 1,350 mg of Usnic acid over a period of weeks has led to severe hepatotoxicity in a number of persons .
Usnic acid can induce oxidative stress and inhibit mitochondrial function in liver cells which may contribute to its hepatotoxicity .
Sassafras (Sassafras albidum) oil has been classified as a liver carcinogen of low grade .
22) Coleus forskohlii root extract
Forskolin is amazing at increasing energy levels and waking you up, but it may cause liver damage. In a study, Coleus forskohlii root extract with 10% forskolin caused liver injury in mice, increasing markers of liver damage .
A clinical study published in 2000 in the Public Health Nutrition journal found that the herb Comfrey (Symphytum spp) posed a “substantial health hazard” to the liver. It caused various levels of damage, potentially leading to liver failure, possibly due to its pyrrolizidine alkaloids .
A 37-year-old male suffered from acute cholestatic hepatitis induced by Corydalis (Corydalis speciosa Max). He complained of jaundice and a mild abdominal discomfort .
25) Pau D’arco
The Pau d’arco tree is indigenous to the Amazonian rainforest and has a long history of traditional use. However, it might also be toxic to the liver, though the evidence is sparse. A 28-year-old developed jaundice after taking Pau d’arco and skullcap for 6 months for multiple sclerosis. His condition progressed to liver failure .
27) Bitter melon
Bitter melon (Momordica charantia) extracts increases markers of liver damage in mice (ALP) but didn’t lead to any other liver changes .
28) Yerba Mate
29) Clove oil
Ingestion of clove oil in one case study resulted in coma, fits and acute liver damage .
30) Olive leaf extract
In South Africa Impila (Callilepis laureola) has been associated with some cases of hepatitis and kidney damage. In one case, a mother who consumed Impila died of liver necrosis. It’s hard to pinpoint the exact cause, but it would be best to avoid this herb due to the lack of safety data .
A 55-year-old woman developed acute liver failure after drinking a tea containing Senna (Cassia augustifolia). The liver-toxic effects of Senna are ascribed to its major constituents, sennosides .
5 Compounds in Foods/Supplements that are Bad for Your Liver
Coumarin is a natural substance found in many plants. It is moderately toxic to the liver and kidneys with a lethal dose (LD50) of 275 mg/kg – this is extremely high, of course. At high doses, coumarin causes liver damage in rats and mice .
This compound is only somewhat dangerous to people at moderate doses and safe at low doses.
European health agencies have warned against high consumption of cassia cinnamon bark due to its high coumarin content .
Coumarin is found naturally in various other edible plants like strawberries, black currants, apricots, and cherries. Its levels in these fruits are mostly negligible, though .
According to one study, coumarins might also damage the brain. They can cause mild neurological dysfunction in children after prenatal exposure. The content of coumarin in foods is regulated in Europe .
Eugenol is a pale yellow oily liquid extracted from certain essential oils like clove leaf oil (80 – 88%), nutmeg , cinnamon, sweet basil , African basil , Japanese star anise  and bay leaf . It is toxic to the liver and may cause liver damage [76, 77].
35) Pyrrolizidine alkaloids
Pyrrolizidine alkaloids are produced by plants as secondary metabolites. There are more than 600 PAs and PA N-oxides identified in over 6,000 plants – and more than half of them are toxic to the liver .
Herbal remedies containing PAs can damage the liver. There is an ongoing controversy over whether the use of such herbs for short periods of time is safe. Their negative effects certainly accumulate over time, and long-term use should be avoided .
Fortunately, some companies, such as Herb Pharm, now make pyrrolizidine-free comfrey. Such products can be used safely and confidently for longer periods of time.
Whole valerian contains liver-toxic substances called valepotriates; however, valepotriates are thought to be absent from most commercial valerian products. Case reports suggest that even high doses of valerian do not harm the liver .
Furano-diterpenoids which are toxic to the liver and may cause hepatitis and even liver damage are found in certain herbs like germander .
A Note About Alcohol
Alcohol consumption is directly associated with liver disease .
In advanced countries, mortality due to liver diseases is directly proportional to alcohol consumption (30g of pure alcohol per day is regarded as a “safe dose”). Serious alcoholic hepatitis has a mortality record of up to 50% .
Fatty liver develops in 90% of individuals who drink more than 16g of alcohol/day but resolves once they stop drinking .
Many reports have claimed that the liver toxicity of paracetamol (acetaminophen) is increased in chronic alcoholics. People not only carry an increased risk of severe and fatal liver damage after acute overdoses, but similar serious liver damage may occur at “therapeutic” doses as well .
This all goes to say that you should avoid alcohol if you want to take care of your liver. An occasional drink is probably fine if you’re healthy, but both binge drinking and alcoholism will damage your liver faster than anything else.
Plus, many of the supplements listed above become dangerous only when combined with either alcohol or drugs.
Herbs and Supplements to Use Only With Caution
As you can see, many natural products have the capacity to harm the liver.
Plus, some herbal products on the market don’t go through adequate quality control. Some may contain heavy metals, toxic solvents, and additives, or other contaminants – even if the actual herbs listed on the label are safe.
Herbal products are sometimes adulterated with other toxic herbs of similar appearance (for example, germander found in skullcap products).
Blue-green algae species such as spirulina may be contaminated with liver-toxic substances called microcystins, for which no highest safe level is known.
Some articles claim echinacea is potentially toxic to the liver, which isn’t true. Echinacea contains substances in the pyrrolizidine alkaloid family. However, its pyrrolizidine alkaloids in echinacea are harmless.
If you have liver disease, you need to be particularly careful about what you’re taking. Ask for quality certificates, monitor your liver enzymes, and talk to your doctor about all the supplements you’re taking to avoid drug interactions.
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