Curcumin is a well studied and versatile supplement. Nonetheless, most of its purported benefits lack solid research. This post will help you understand when curcumin is likely to be effective and when there are not enough data to say. Read on to discover the science behind curcumin supplementation.
What is Curcumin?
Conditions That May Benefit From Curcumin
- Allergic rhinitis (hay fever)
- Depression
- High blood fats
- Non-alcoholic fatty liver disease
- Osteoarthritis
- Pruritus (itchy skin)
Note that turmeric is not bioavailable. Taking regular curcumin supplements will unlikely provide benefits outside the gut [1, 2]. Some forms of curcumin may be more bioavailable (such as CurcuBrain).
Turmeric (Curcuma Longa), most commonly known as the spice found in curry, is not only known for its flavor, but for its purported health benefits as well.
Curcumin supplements have not been approved by the FDA for medical use. Supplements generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
How much do we know?
According to the National Center for Complementary and Alternative Medicine (NCCIH), there’s a lot of research about turmeric or curcumin, including human studies, for a variety of health conditions [3].
However, strong evidence is lacking to support claims that curcuminoids from turmeric help reduce inflammation [3].
Active Compounds
Turmeric contains several major constituents known as curcuminoids, which typically make up about 3% of its weight in commercially available preparations [4].
Curcumin is known to be the most active phytochemical of the four curcuminoids found in turmeric. It makes up 77% of curcuminoids [5].
The remaining three constituents typically come in at 17% desmethoxycurcumin, 3% bisdemethoxycurcumin, and the remaining, more recently identified curcuminoid, cyclocurcumin [5].
Snapshot
Proponents
- Allegedly reduces inflammation
- May help balance the immune system
- Good for detoxing
- Likely safe
Skeptics
- Poor bioavailability
- Lack of solid data for most uses despite a large body of research
- Has a specific taste some people don’t like
Health Benefits of Curcumin
Possibly Effective for:
1) Osteoarthritis
Research suggests that specific turmeric extracts (Meriva, Indena), alone or in combination with other herbs, may reduce pain and improve function in people with knee osteoarthritis [6].
Three-month supplementation with 200mg/day of a curcumin-phosphatidylcholine complex (Meriva, Indena) decreased pain scores by 58% and increased walking distance by over 400% in osteoarthritis [7].
Curcumin has also been researched for its potential to regenerate cartilage [8].
2) Hay Fever
Some clinical trials suggest that two months of curcumin supplementation (Organika Health Products) at 500 mg/day can reduce hayfever symptoms like sneezing, itching, runny nose, and congestion. The authors proposed that curcumin helps balance the immune response [9].
3) Depression
A recent review of clinical trials suggests that curcumin reduces depression symptoms as an add-on in people already using an antidepressants
The effect of curcumin appears to be greater for middle-aged people compared to older people. Better effects were also seen in people who supplemented for at least 6 weeks and who used at least 1 gram daily [10].
Additionally, various curcumin formulations were used in the included studies. They all had similar effectiveness, although one specific formulation (BCM-95) seemed to offer non-significantly greater benefits to people with depression than the typical curcumin-piperine formulations. Additional studies should look into various curcumin formulations [10].
In older people, curcumin improved sustained attention, working memory, and mood [11].
Scientists are investigating whether curcumin affects the development of new cells and BDNF stores in the hippocampus in chronically stressed rats (a model of depression in animals) [12].
Other active areas of research are looking into the effects of curcumin on blood cortisol levels and cortisol sensitivity (Glucocorticoid Receptor Expression), NMDA and 5HT2C receptor activation, and glutamate activity in the brain [13, 14, 15, 16].
In mice, potential interactions and synergistic effects between curcumin (+piperine) and SSRI and SNRI antidepressants are being researched [17].
4) Nonalcoholic fatty liver disease (NAFLD)
Clinical trials suggest that curcumin can reduce markers of liver injury and liver fat buildup in people non-alcoholic fatty liver disease (NAFLD) [18, 19].
Scientists are exploring curcumin’s NAFLD-related mechanisms in animals and cells. Some hypotheses suggest that curcumin improves NAFLD by raising leptin sensitivity, inhibiting obesity-induced inflammation, and lowering LDL cholesterol and triglycerides. These mechanisms remain to be confirmed in humans [20, 21].
5) Itchy Skin (Pruritus)
According to clinical trials, turmeric 500 mg orally three times daily for 8 weeks decreases symptoms of itchy skin (uremic pruritus) in patients with end-stage renal disease [22].
Early clinical findings also suggest that curcumin reduces pruritus severity and improves quality of life in patients with sulfur mustard-induced chronic pruritus after daily use for 4 weeks [23, 24].
Possibly Ineffective for:
High Blood Lipids
The effects of turmeric on cholesterol levels are mixed.
Some studies suggest turmeric lowers the “bad” cholesterol LDL and triglycerides but doesn’t affect total cholesterol or the “good” cholesterol HDL. Another review suggested that curcumin improves HDL but doesn’t affect LDL. Future studies need to clarify the conflicting findings [25, 26].
Additionally, it’s uncertain which curcumin formulations have a meaningful effect. More research is needed [25, 26].
Peptic Ulcers
Based on the available evidence, it’s possible that curcumin has no effect on peptic ulcers [27, 28].
Radiation Dermatitis
Existing studies suggest that curcumin doesn’t improve radiation dermatitis, which is a type of skin damage and irritation caused by radiotherapy [29].
Likely Ineffective for:
Alzheimer’s Disease
The existing evidence does not support the use of turmeric in patients with Alzheimer’s disease.
In a small trial, 1-4 g/day of curcumin for 6 months had no effect on mental and cognitive state in patients with Alzheimer disease [30].
A meta-analysis of studies revealed that the turmeric group may have experienced greater cognitive decline when compared with placebo. Data are limited by small sample sizes and patient variability, but there’s enough evidence to advise against turmeric in people with Alzheimer’s [31].
These findings outline how a compound can have completely different effects in animals than in live human beings. It should serve as a reminder that animal findings should always be interpreted with extreme caution and healthy skepticism.
Prior to the above-mentioned clinical trials, many animal experiments suggested that curcumin can “reverse cognitive decline, memory deficits, and inflammation in animal models of Alzheimer’s disease.” Various mechanisms were proposed (like increasing neurogenesis, BDNF, and CREB). Yet, curcumin was a failure clinically [32, 33, 34, 35, 36].
Insufficient Evidence for:
The following purported benefits are only supported by limited, low-quality clinical studies.
There is insufficient evidence to support the use of curcumin for any of the below-listed uses. Remember to speak with a doctor before taking curcumin supplements. Curcumin should never be used as a replacement for approved medical therapies.
Joint Pain & Arthritis
In patients with rheumatoid arthritis, 500mg curcumin + diclofenac sodium was found to be effective [37].
Crohn’s Disease
Low-quality evidence suggests curcumin may reduce bowel movements, diarrhea, and stomach pain in people with Crohn disease after daily supplementation for a month [38].
Lupus
According to preliminary research, in Lupus patients, short-term turmeric supplementation decreases blood and protein in the urine along with systolic blood pressure [39].
Diabetes
Preliminary data suggests that curcumin improves cardiovascular function and reduces oxidative stress in diabetic patients [40].
A nine-month curcumin intervention significantly lowers the chances that prediabetes develops into Type II diabetes, potentially improving the overall function of pancreatic cells [41].
PMS
Curcumin reduced the severity of PMS in a very small human study [42, 43].
Animal Research (Lacking Evidence)
No clinical evidence supports the use of curcumin for any of the conditions listed in this section.
Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
Gut Health, Autoimmunity & Other
Researchers are investigating the effects of curcumin in animals and cells on:
- Bile release from the gallbladder [44]
- Multiple sclerosis, rheumatoid arthritis, psoriasis [45, 46, 47, 48]
- Inflammatory cytokines such as IL-1beta, IL-6, IL-12, TNF-alpha and IFN-gamma and associated JAK-STAT and NF-kappaB signaling pathways in immune cells [45]
- Viruses such as influenza [49]
- Candida albicans [50, 51, 52, 53]
- Septicemia in mice exposed to the pathogenic bacteria responsible for cholera [54].
- Lung inflammation in Pneumoniae [55]
- Brain cell death [56]
- Glutathione levels, insulin receptor protein levels, and oxidative stress [57]
- GSK3b [58]
Human data on these effects are lacking.
We’ve already discussed how curcumin inhibits biofilms and quorum sensing and how it is being researched for activating the vitamin D receptor, which might be important for combating infections.
Brain DHA
One of the interesting things scientists are investigating about curcumin is its potential effect on brain DHA levels [59].
In cells, curcumin elevates levels of enzymes involved in the synthesis of DHA from ALA in both liver and brain tissues [59].
This may turn out to have significance since Fish oil/DHA supplements sometimes don’t increase DHA in the brain. However, curcumin may turn out not to affect brain DHA levels in humans at all. We simply don’t know yet.
Metal Toxicity
The effects of curcumin on metal toxicity in humans are unknown.
Curcumin decreases inflammatory markers in copper-overloaded rats and reduces aluminum-induced inflammatory responses in rat brains [60, 61].
Cell studies are investigating its effects on DNA damage from arsenic, mercury, fluoride, and excess selenium [62, 63, 64, 65].
In mercury-exposed rats, curcumin reduces oxidative stress [63].
In iron-overloaded rats, curcumin decreased iron accumulation in the liver and spleen and restored antioxidant levels [66].
Obesity, Diabetes, Libido, Cataracts and Muscle Tissue
None of the following effects have been researched in humans.
Curcumin enhances erectile function in diabetic male rats [67].
Curcumin lowers blood sugar, improves insulin sensitivity, reduces urine sugar and in diabetic mice [68, 68].
In animals, scientists are studying if curcumin can lower blood sugar by stimulating insulin secretion from pancreatic cells [69], affects pancreatic regeneration, affect muscular insulin resistance, or obesity [70, 71, 72].
Bioavailable Curcumin delays cataract development in diabetic rats [73].
It alleviates diabetic cardiomyopathy in diabetic rats [74].
Studies are investigating whether curcumin lessens diabetic complications in rat brains, slowing mitochondrial dysfunction [75].
In cells, scientists are studying if curcumin activates AMPK in muscle leading to increased glucose uptake [76] and inhibiting new growth and formation of fat cells [77, 78].
Other researchers are looking into its effects on muscle tissue generation and healing after injury [79].
Antioxidant and an Anti-inflammatory
Some researchers consider curcumin to be an oxygen radical scavenger. According to one hypothesis, it acts as an antioxidant by increasing glutathione levels, and as an anti-inflammatory agent through inhibition of IL-8 (in lung cells). These effects have not been confirmed in humans [80].
Scientists are exploring its effects on the following pathways in animals or cells
- Lipid peroxidation and levels of glutathione, superoxide dismutase (SOD), and catalase [63]
- Levels of vitamins C & E and DNA damage [81]
- Gene expression and enzyme interactions (HDACs, HATs, DNMT I and miRNAs) [82]
- Blood inflammatory markers (IL-8, IL-10, and TNF-α) [83]
- Chronic fatigue and prostate inflammation [84, 85]
- IL-18 [86], PAI-1 [87, 88] and mTOR [89, 90]
- Tregs [91, 92, 93]
- Mast cells [94], DAO, and histamine [95]
- Cholinergic activity and nicotine binds to (alpha 7-nACh) receptors [96, 97]
Cancer Research
Neither turmeric nor its active compound curcumin have been shown to treat or prevent cancer.
Only a few small-scale studies suggest that it may have biological effects on some cancer patients, but more data are needed to verify its safety and effectiveness.
In early phase clinical studies, a combination of curcumin and docetaxel (a chemotherapy drug) was shown to be safe in 14 advanced and metastatic breast cancer patients [98].
Curcuma extract appeared to be safe in a small trial of patients with colorectal cancer. Given to colorectal cancer patients during the pre-surgery waiting period, curcumin improved muscle wasting and general health. Preliminary data suggest it might reduce numbers of precancerous rectal aberrant crypt foci in people at high risk of colorectal cancer. Large-scale studies are lacking [99, 100, 101].
Curcumin has mostly been researched in cancer cells.
Remember that many substances have anti-cancer effects in cells, including toxic chemicals like bleach. This doesn’t mean that they have any medical value. On the contrary, most substances (natural or synthetic) that are first researched in cancer cells fail to pass further animal studies or clinical trials due to a lack of safety or efficacy.
With this in mind, scientists have explored the effects of curcumin on the following pathways or types of cancer cells in dishes or animals:
- Brain cancer (glioblastoma) cells and oral cancer cells [102]
- T-cell lymphoma cells [103], bone [104], brain [105], and melanoma cancer cells [106]
- Cancer cell mitochondria[107]
- Breast cancer [108]
- Colon cancer
- Activity in combination with EGCG in lymphocytic leukemia cells [109]
- Lung cancer cells (inhibition of IL-8 ) [80]
- Prostate cancer cells [110, 111]
- Pancreatic cancer cells [112]
- Activating the nuclear vitamin D receptor, with theoretical implications against intestinal cancers [113]
None of these mechanisms have been explored in humans.
Liver & Kidney Health
In animals with alcohol-induced oxidative stress, curcumin was researched for reducing inflammation, lipid peroxidation, and liver damage. It was also studied in rats with kidney injury or Tylenol-induced kidney damage. However, the effects of curcumin on liver or kidney disease in humans remain unknown [114, 115, 114, 114, 116, 117, 118].
Supplementing With Curcumin
Dosages
The following dosages were used in clinical trials:
- Osteoarthritis: Turmeric extract 500 mg orally two to four times daily for 1-3 months (the following products were used, which may be important for bioavailability reasons: Turmacin by Natural Remedies Pvt. Ltd., Meriva by Indena, and CuraMed by EuroPharma USA)
- Allergic rhinitis (hay fever): Organika Health Products curcumin 500 mg daily for 2 months
- Crohn disease: Curcumin 1.08 grams daily for one month then 1.44 grams daily for a second month
- Type 2 diabetes prevention in people with prediabetes: curcumin 750 mg twice daily for 9 months
- Depression: Curcumin, 500 mg twice daily for 6-8 weeks(alone or as an add on to the antidepressant fluoxetine)
- Nonalcoholic fatty liver disease (NAFLD): 70 mg of curcumin daily for 8 weeks (in 500 mg of a dispersion formulation)
- Pruritus: turmeric 500 mg orally three times daily for 8 weeks or turmeric extract (C3 Complex, Sami Labs LTD) standardized to 1 g of curcumin with an extract from black pepper or long pepper (Bioperine) daily for 4 weeks
Potential Risks and Side Effects
General
Turmeric is generally well tolerated.
Common side effects include constipation, indigestion (dyspepsia), diarrhea, distension, gastroesophageal reflux (acid reflux), nausea, vomiting, and other gut issues.
Very rarely, curcumin can cause pruritus or pitting edema.
Applied on the skin, turmeric may cause allergic contact dermatitis.
In High Dose In-Vitro Models, Curcumin Can Cause Cytotoxicity and DNA Damage
At high doses it is suggested that curcumin may actually induce ROS, leading to DNA damage [119].
Many of the concerns regarding curcumin toxicity are addressed in this letter titled “More research is needed to establish the benefit-risk profile of curcumin” [120].
As a quick summation of the article, although worth the read, the first issue addressed is that many of these studies are done in-vitro. Meaning done in a test tube, outside of a living breathing organism.
Fertility
Cellular and animal research suggests that curcumin can decrease sperm motility and density. Curcumin may inhibit enzymes involved in the final step of testosterone synthesis. Its effects on fertility in humans are unknown [121].
The same study states that because humans can consume up to 8 grams of turmeric per day without apparent side effects, consuming curcumin orally may not increase curcumin levels in the blood enough to inhibit testosterone synthesis.
Parkinson’s Disease
In vitro, curcumin increases LRRK2 mRNA and protein. LRRK2 is a gene whose expression has been positively associated with Parkinson’s disease. This could, in theory, lead to an increased risk of Parkinson’s disease. However, the effects of curcumin of Parkinson’s disease in humans remain unknown [122].
Synergies
Adding piperine (from black pepper) likely increases the absorption of curcumin into the blood — in fact, researchers have estimated that it may increase the bioavailability of curcumin by as much as 2,000% [123].
