Curcumin side effects you must know (before you start)

The short answer: Is curcumin safe?

For the vast majority of people: yes. The European Food Safety Authority (EFSA) and various US authorities classify curcumin as GRAS – "Generally Recognized As Safe".

In studies, dosages of up to 8,000 mg of curcumin per day are tested over several months without serious toxic effects occurring. By comparison: a good capsule often contains only 500 mg. Your safety buffer is therefore huge [1].

But: safety does not mean tolerability. And it does not mean there are no interactions. While the 30-year-old healthy athlete can eat the stuff like candy, it looks different for you if you perhaps take blood-pressure medication or have a sensitive digestion.

• Frequency: Serious side effects are very rare.
• The classic: When something happens, it is usually mild gastrointestinal problems (bloating, nausea).
• Risk groups: People with gallstones, pregnant women and patients on blood thinners must be careful.
• Quality: Many "side effects" come not from the curcumin itself, but from impurities or additives in cheap powders.

The gastrointestinal tract: when it rumbles

Let's start with the elephant in the room. You take your capsule and two hours later you feel bloated or urgently need the toilet. This is by far the most common complaint readers describe to me in studies, mild gastrointestinal complaints occurred occasionally at 450 to 3,600 mg of curcumin per day, more frequently at high single doses up to 12,000 mg; Hewlings & Kalman, 2017.

Why does this happen?

Curcumin is a spice. And like many spices (think of chili or pepper), it stimulates stomach-acid production and bile flow. This is actually good for digestion – which is why turmeric is in every fatty meal in India.

But if you are sensitive or take a very high dose on an empty stomach, this stimulus can be too much.

The paradox: Many people take curcumin in the context of inflammatory bowel diseases (such as ulcerative colitis), because it was investigated there in studies. But in others it irritates the mucosa.

My tip: Never take curcumin on an empty stomach. Always eat something with it, ideally something with fat (yogurt, avocado, lunch). This buffers the direct contact with the stomach wall and, as a bonus, improves absorption.

Gallstones: the mechanical conflict

This is important, and it is on the fewest packages.

Curcumin has a choleretic effect. In plain terms: it makes the gallbladder contract and pump bile fluid into the gut. This helps fat digestion immensely.

The problem arises if you have gallstones.

Imagine there are small stones in your gallbladder. They usually don't bother you as long as they lie still. If curcumin now stimulates the gallbladder to contract, these stones can be pressed into the bile duct. The result is a gallbladder colic – and that is extremely painful.

The rule: If you know you have gallstones or have ever had a colic, keep your hands off high-dose curcumin preparations until you have talked to your doctor. As a spice in food it is usually okay, but concentrates are too risky here.

Blood thinning: when the blood gets too fluid

Curcumin has mild blood-thinning properties (anticoagulant effect). It slightly inhibits the clumping of platelets. This is actually great for heart health – it acts similarly to a very weak aspirin.

But what if you already take blood thinners?

Marcoumar, aspirin, Plavix or newer anticoagulants have exactly this job. If you now take curcumin on top, the effects add up. "Well-flowing blood" then becomes "blood that no longer stops at a cut".

There are reports of patients whose clotting values (INR) changed after they combined curcumin and warfarin [2].

The kidney and the oxalate problem

You may have heard that turmeric can cause kidney stones. That is true – but you have to differentiate.

The turmeric root (and plain powder) contains relatively a lot of oxalate. Oxalic acid binds to calcium in the body and forms calcium oxalate – the main component of most kidney stones. So if you stir 5 grams of turmeric powder into your smoothie every day and are prone to kidney stones, that is a risk [3].

The good news: High-quality curcumin extracts are usually purified and contain hardly any oxalates. Extraction concentrates the curcumin and removes the fibers and accompanying substances of the root. If you are prone to kidney stones, a pure extract (standardized to 95% curcuminoids) or a micelle formulation is significantly safer than the spice powder from the supermarket.

You can find more on the difference between powder and extract in our comparison: Turmeric extract vs. powder.

Liver values: what studies show

In recent years there have been isolated headlines: "Dietary supplement causes liver damage." This causes massive uncertainty.

Let's look at the facts. Curcumin is investigated in numerous studies in connection with the liver (keyword hepatoprotection). Whether a benefit for humans can be derived from this is not proven – there is no approved health claim for curcumin.

So how do the liver damages fit in?

In the few documented cases (we are talking about a handful of cases per million users), there were usually two causes:

1. Impurities: Cheap products that were cut with heavy metals or dyes.
2. Interactions: The combination with medications that were no longer broken down due to curcumin (or piperine) and accumulated in the liver.
3. Idiosyncrasy: An extremely rare, genetically determined intolerance that cannot be tested for beforehand. Just as some people react allergically to peanuts.

A comprehensive analysis from Italy concluded that curcumin is safe as long as there are no specific pre-existing liver conditions and the products are clean [4]. Nevertheless: if your skin or eyes turn yellow or the urine becomes dark (signs of jaundice) – stop immediately and see a doctor.

Interactions: the "bouncer" effect

This is the most technical part, but the most important for you if you take medications.

Many curcumin products contain piperine (black pepper) to improve absorption. Piperine does this by blocking enzymes in the liver that break down foreign substances. It sends the bouncer on a break so the curcumin can slip through.

The problem: the bouncer then also lets through medications that were supposed to be broken down. As a result, the effect of your tablets (e.g. beta-blockers, antidepressants) can rise uncontrollably. The risk of side effects of your medications increases.

If you take medications daily, I rather advise against piperine products. There are safer alternatives such as micelles or cyclomaltooctaose (a ring-shaped sugar molecule) that increase bioavailability without paralyzing the liver enzymes.

You can read all the details here: Piperine + turmeric: understanding the risks.

Who should avoid it entirely?

In summary, there are groups for whom the risk outweighs the benefit, or who should at least keep in close consultation:

1. Pregnant & breastfeeding women: In India, women eat turmeric in curry even during pregnancy. But high-dose capsules are taboo. Curcumin can theoretically stimulate the uterus. Don't take any risk.
2. People with gallstones: As explained above – the stone could start rolling.
3. Before operations: Because of the risk of bleeding.
4. Underweight people: Curcumin can curb the appetite in some people and slightly stimulate the metabolism.

Our recommendation: safety first

Don't let yourself be driven crazy. In studies, curcumin at usual doses is considered well tolerated in healthy adults. The reports of serious side effects are rare exceptions.

But: respect the biological power of this substance.

This is how you do it right:

• Start low, go slow: Don't start with the maximum dose right away. First take one capsule a day and see what your stomach says.
• Quality over quantity: Buy products that are tested for contaminants. Your body is not a trash can for cheap extracts.
• Listen to your body: If you don't feel well after taking it, leave it out. It's that simple.

If you are unsure how best to integrate curcumin into your everyday life, take a look at our guide: How to take turmeric correctly.

Read more

Want to know how to minimize the risks and maximize the benefits? Continue here:

• Is piperine dangerous? Why the "turbo" can cause problems
• The safest way to take it: how to boost the effect without risks
• What for, actually? The 7 proven effects of curcumin

Sources:

• [1] Soleimani, V. et al. (2018). Turmeric (Curcuma longa) and its major constituent (curcumin) as nontoxic and safe substances: Review. Phytotherapy Research. DOI: 10.1002/ptr.6054
• [2] Heck, A.M. et al. (2000). Potential interactions between alternative therapies and warfarin. American Journal of Health-System Pharmacy. DOI: 10.1093/ajhp/57.13.1221
• [3] Tang, M. et al. (2008). Effect of cinnamon and turmeric on urinary oxalate excretion, plasma lipids, and plasma glucose in healthy subjects. American Journal of Clinical Nutrition. DOI: 10.1093/ajcn/87.5.1262
• [4] Menniti-Ippolito, F. et al. (2020). Turmeric (Curcuma longa L.) food supplements and hepatotoxicity: an integrated evaluation of notifications in Italy. Annals of the Istituto Superiore di Sanità. DOI: 10.4415/ANN_20_03_07

Note: Dietary supplements should not be used as a substitute for a balanced and varied diet. Do not exceed the recommended daily dose. Store out of the reach of young children.