Turmeric is a popular yellow spice originating from South Asia. It is an essential ingredient in many Indian dishes.
It is also consumed for its health benefits. Supplements of turmeric or curcumin - the main active ingredient - are becoming increasingly popular.
However, some people are concerned about the potential side effects of high doses of turmeric and curcumin supplements.
This content is evidence.
Adverse effects of turmeric and curcumin
Both turmeric and curcumin, with curcumin being the main active ingredient, are generally considered safe and without any serious side effects (s, s).
However, some people may experience side effects when taken in large doses as supplements.
1. Adverse effects of turmeric
Turmeric contains about 2% oxalate. In high doses, this may contribute to the formation of kidney stones in susceptible individuals (s).
Not all commercial turmeric powders are pure. Some are adulterated with cheaper and potentially toxic ingredients not listed on the label.
Studies have revealed that commercial turmeric powders may contain fillers such as cassava starch, barley, wheat or rye flour (s).
Eating turmeric containing wheat, barley, or rye (rye) flour causes negative symptoms in people with gluten intolerance or celiac disease.
Some turmeric powders may also contain questionable food colorings, which are added to improve color when turmeric powders are diluted with flour.
One of the most frequently used food dyes in India is methanol yellow, also called acid yellow 36.
Animal studies show that methanol yellow may cause cancer and neurological damage when taken in large amounts (s, s, s).
While the toxic effects of methanol yellow have not been investigated in humans, it is illegal to use it in the United States and Europe.
Some turmeric powders may also contain a high percentage of lead, a heavy metal that is particularly toxic to the nervous system (s, s).
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 colorings.
See: 8 Difference Between Turmeric and Curcumin and Common Benefits
2. Adverse effects of curcumin
Curcumin is a substance extracted from turmeric. 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 are considered safe and no harmful side effects have been reported at low doses.
One study in 10 adults found that taking 490 mg of curcumin daily for a week caused no side effects (s).
Other studies showed that taking doses of 1200-2100 mg of curcumin daily for 2-6 weeks did not lead to any obvious adverse effects (s, s).
However, a small percentage of people may experience some mild side effects at higher doses. These may include:
- Digestive problems: People may experience mild digestive issues such as bloating, acid reflux, flatulence, and diarrhea at daily doses of over 1,000 mg (s, s).
- Headache and nausea: Doses of 450 mg or more may cause headache and nausea in a small number of people (s, s).
- Skin rash: People have reported developing a rash after taking a dose of 8000 mg of curcumin or more, but this appears to be very rare (s).
Extremely high doses of 1,170 mg per pound (2,600 mg/kg) of body weight daily for 13 weeks, or up to two years, may cause some serious side effects in mice.
These included an increase in liver size, colored fur, stomach ulcers, infections and an increased risk of bowel or liver cancer (s).
However, the dose makes the poison. There is currently no evidence that low amounts of curcumin cause serious side effects in humans when taken for short periods, although there are no human studies on long-term effects.