Turmeric is a yellow-orange spice originating in southern Asia. It’s a popular ingredient in many Indian and Middle Eastern dishes.
It’s also consumed for its health benefits. Supplements containing turmeric or curcumin — its main active ingredient — are becoming increasingly common.
However, some people are concerned about the possible side effects of high-dose turmeric and curcumin supplements. This review looks into the evidence.
What is turmeric?
Turmeric, also known by the scientific name Curcuma longa, is an ancient Indian spice, medicinal herb, and food dye in the ginger family.
It is an essential ingredient in Indian curries, with a taste that is often described as bitter and peppery. Nearly all of the world’s turmeric is grown and consumed in India.
Turmeric’s root stalks, called rhizomes, are bright yellow or orange. They’re usually dried and ground into powder.
Turmeric mainly consists of carbs, mostly starch and fiber. However, like all spices, turmeric contains numerous plant compounds and nutrients.
The root stalks are also rich in plant compounds called curcuminoids. These curcuminoids are the main active compounds in turmeric. They are responsible for turmeric’s orange-yellow color and most of its health benefits.
The most widely studied curcuminoid is curcumin, which may account for around 4% of turmeric.
Commercial turmeric or curcumin powders also usually contain additives. These include silicon dioxide, an anti-caking agent that prevents clumping.
Some cheap turmeric powders may also contain illegal additives not listed on the labels. This is called turmeric adulteration, which is discussed in more detail below.
Summary: Turmeric is a popular yellow-orange spice. It is also used as a food dye and dietary supplement. The compound curcumin is responsible for most of its health benefits.
Why do people eat turmeric?
Turmeric is used as a spice and food dye, adding flavor and color to food. It has also been consumed for its health benefits. Most of these have been attributed to curcumin, its main active ingredient.
Curcumin supplements offer the following benefits, to name a few:
- Reduced inflammation. Chronic inflammation is associated with many diseases. Studies show that curcumin supplements may reduce levels of inflammatory markers and help treat or reduce symptoms of inflammatory health conditions, like inflammatory bowel disease, arthritis, psoriasis, depression, and atherosclerosis.
- Improved antioxidant status. Curcumin and other curcuminoids are powerful antioxidants that may improve your antioxidant status. Antioxidants protect against cellular damage from free radicals associated with health conditions like diabetes, heart disease, and cancer.
- Improved blood vessel function. Studies suggest that curcumin supplements may promote the dilation (widening) of blood vessels, increasing blood flow and reducing blood pressure.
- Reduced heart attack risk. They may also lower the risk of heart attacks, possibly through their anti-inflammatory effects, by improving endothelial function or cholesterol levels.
- Anticancer properties. Curcumin may help slow cancer cell growth and promote cancer cell death. Current research is investigating curcumin’s potential as a treatment for various cancers, including breast, prostate, pancreatic, colorectal, and lung cancers.
- Support neurological health. Curcumin supplements may improve symptoms of neurodegenerative diseases, like Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and dementia.
Summary: In addition to using turmeric as a spice and food dye, people eat it for its health benefits, which have been extensively studied.
Adverse effects of turmeric and curcumin
Both turmeric and its main active ingredient, curcumin, are generally considered safe and without serious side effects.
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However, some people may experience side effects when they take them in large doses as supplements.
Turmeric contains around 2% oxalate. At high doses, this may contribute to kidney stones in predisposed individuals.
Additionally, not all commercial turmeric powders are pure. Some are adulterated. This means cheaper and potentially toxic ingredients have been added and are not listed on the label.
Studies have revealed that commercial turmeric powders may contain fillers such as cassava starch, barley, wheat, or rye flour.
Eating turmeric that contains wheat, barley, or rye flour can cause adverse symptoms in people with gluten intolerance or celiac disease.
Some turmeric powders may also contain questionable food colorants, which are added to improve color when the powder is diluted with flour.
One food colorant frequently used in India is metanil yellow, also called acid yellow 36. Animal studies show that metanil yellow may cause cancer and neurological damage when consumed in high amounts.
While the toxic effects of metanil yellow have not been investigated in humans, it’s unlawful to use it in the United States and Europe.
Some turmeric powders may also be high in lead, a heavy metal that is seriously toxic to the nervous system.
Dietary turmeric does not significantly influence how your body processes medications.
However, turmeric’s effects may increase or interfere with the actions of some of the medications you are taking.
For example, turmeric has an anticoagulation effect, which can interfere with blood clotting. Taking curcumin with anticoagulant drugs or blood thinners such as aspirin, clopidogrel (Plavix), or warfarin (Jantoven) can increase their effects and may lead to excessive bleeding.
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Turmeric can also lower blood sugar and may enhance the effects of antidiabetic drugs or insulin.
Since turmeric can lower blood pressure, it may have additive effects with antihypertensive drugs.
Turmeric can aid digestion by increasing stomach acid levels, which may inhibit the effectiveness of antacids.
If you’re considering taking a new supplement, always talk with your doctor first to make sure they are aware and can point you toward any possible interactions with medications you’re already taking.
Curcumin supplements are safe, and no adverse side effects have been reported at low doses.
One older study in 10 adults found that taking 490 mg of curcumin daily for a week caused no side effects.
A new review from 2021 also found that taking doses of around 1,000 mg of curcumin per day did not lead to any apparent adverse effects.
Yet, a small proportion of people may experience some mild side effects at higher doses. These may include:
- Digestive issues. People may experience mild digestive issues such as bloating, acid reflux, flatulence, and diarrhea at daily doses exceeding 1,000 mg.
- Headache and nausea. Doses of 450 mg or higher may cause headache and nausea in a small number of people.
- Skin rash. People have reported a skin rash after taking a dose of 8,000 mg of curcumin or more, but this seems very rare.
Extremely high doses of 1,170 mg per pound (2,600 mg/kg) of body weight daily for 13 weeks, or up to 2 years, may cause severe side effects in rats. These include increased liver size, stained fur, stomach ulcers, inflammation, and increased intestinal or liver cancer risk.
However, the dose makes the poison. There is currently no evidence that lower amounts of curcumin cause serious side effects in humans when taken over short periods. However, human studies on the long-term effects are lacking.
While curcumin has a very good safety profile, some research suggests it may affect how your body processes certain medications, including:
- cardiovascular drugs
- chemotherapeutic agents
One study suggests that curcumin supplements may induce a gene that can cause decreased levels of certain antidepressant and antipsychotic medications.
In one animal study, curcumin enhanced the antidepressant effects of fluoxetine.
It may also increase sulfasalazine (Azulfidine) levels. Sulfasalazine is a disease-modifying antirheumatic drug (DMARD), which may be prescribed to treat ulcerative colitis or rheumatoid arthritis.
Curcumin may inhibit the anticancer activity of drugs used for chemotherapy, so those undergoing chemotherapy should consult their doctor before taking curcumin.
Like turmeric, curcumin’s effects on the body may augment or interfere with the actions of some of the medications you are taking.
Curcumin’s anticoagulation effect may lead to excessive bleeding if taken along with anticoagulant drugs or blood thinners such as aspirin, clopidogrel (Plavix), or warfarin (Jantoven)).
Curcumin can also lower blood sugar and may enhance the effects of anti-diabetic drugs or insulin.
Since curcumin can lower blood pressure, it may have additive effects with antihypertensive drugs.
Curcumin can increase stomach acid levels, inhibiting antacids’ effectiveness.
That said, research on possible drug interactions with curcumin is limited and doesn’t provide enough evidence to confirm whether taking curcumin supplements interacts with other medications you may be taking.
If you are taking other medications, consult your physician or another qualified health professional before taking curcumin supplements.
Summary: Pure turmeric is considered safe for most people. However, turmeric powders may sometimes be adulterated with cheap fillers, such as wheat starch and questionable food colorants. They may even contain lead. High doses of curcumin may cause mild side effects in some people, but it is generally considered safe. The long-term effects of taking curcumin in humans are unknown. Curcumin supplements may interact with other medications you are taking. If you are taking other medications, consult your physician before taking curcumin supplements.
How much turmeric is too much?
There are no official recommendations for the intake of turmeric, and the maximum tolerable intake level has not been identified.
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However, as a general rule, you should not exceed the dosage recommendations you find on supplement labels.
On the other hand, there are some official guidelines for the intake of curcumin.
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) set the acceptable dietary intake as 1.4 mg per pound (3 mg/kg) of body weight per day.
For a 178-pound (81-kg) man, this would translate into 239 mg per day.
However, one older review concluded that doses of 3,600–8,000 mg daily do not cause serious side effects. Another study showed that single doses of 12,000 mg were well tolerated.
As always, talk with a doctor before deciding how much of a supplement you should start taking a day.
Summary: There are no official guidelines for the intake of turmeric, but the acceptable intake level for curcumin is 1.4 mg per pound (3 mg/kg) of body weight.
How to ensure turmeric quality
Some turmeric powders contain cheap fillers not mentioned on the labels.
These adulterated powders are difficult to identify without a chemical analysis. Your best bet is to choose turmeric certified by a reputable agency.
For instance, you could look for organic turmeric certified by the U.S. Department of Agriculture (USDA).
If you are taking turmeric or curcumin supplements, select supplements that have a quality certification by a third party. Several companies provide quality certifications for supplement manufacturers.
These include NSF International, Informed Choice, and the US Pharmacopeial Convention (USP). Look for their seal on the packaging of products, or go to their websites to see what supplements they’ve certified.
Summary: Buy your turmeric and curcumin supplements from trustworthy suppliers and choose products certified by a reputable third party.
Turmeric and curcumin supplements do not seem to have any severe side effects.
However, at high doses, some people may be prone to mild discomforts, such as headaches or diarrhea.
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Keep in mind that low-quality turmeric may be adulterated with cheap fillers, such as wheat starch, which will cause adverse symptoms in people with gluten intolerance.
Curcumin supplements may interact with other medications you are taking. Consult your physician before taking curcumin supplements if you currently take other medications, like blood thinners, insulin, or antihypertensive drugs.