What’s The Excitement About Turmeric?

There have been lots of exciting news stories about turmeric over the last few years: from claims that it might slow Alzheimer’s Disease, to reducing the incidence of leukaemia, or being a potent weapon against several cancers and cystic fibrosis. There are the usual claims that it has general anti-inflammatory effects and modulates the immune system although the mechanisms are presently unclear. There is a good overview about curcumin and some of its principal researchers in a recent Scientific American: Spice Healer.

In his BMJ Rapid Response Holford eulogised the benefits of curcumin (the active ingredient of turmeric that has attracted most interest) and made a plea for a proper sense of perspective.

The most recent review on turmeric, in the January issue of the Journal of Clinical Immunology (5), states: “Traditionally known for its an anti-inflammatory effects, curcumin has been shown in the last two decades to be a potent immunomodulatory agent that can modulate the activation of T cells, B cells, macrophages, neutrophils, natural killer cells, and dendritic cells. Curcumin can also downregulate the expression of various proinflammatory cytokines including TNF, IL-1, IL-2, IL-6, IL-8, IL-12, and chemokines, most likely through inactivation of the transcription factor NF-kappaB. Interestingly, however, curcumin at low doses can also enhance antibody responses. This suggests that curcumin’s reported beneficial effects in arthritis, allergy, asthma, atherosclerosis, heart disease, Alzheimer’s disease, diabetes, and cancer might be due in part to its ability to modulate the immune system. Together, these findings warrant further consideration of curcumin as a therapy for immune disorders.”

The safety data on turmeric is exceedingly good. Even if somewhat premature, is it really such a sin to recommend people in Britain to eat this spice on a regular basis, as done in Asian countries where prostate cancer incidence is exceedingly low?

Should readers feel abashed? Not really. Holford is not merely recommending that people should eat turmeric on a regular basis. He is aware that it isn’t practical for most people to obtain the recommended curcumin intakes by eating “this spice on a regular basis”. Presumably, this encouraged him to develop and promote his own curcumin supplement and advise an intake of up to 4g per day which is around an estimated 20 times the amount consumed in the average indian diet.

Registered Dietitian, Catherine Collins, disputed the practicality of Holford’s recommendations in her own response to him.

Registered Dietitians would disagree with nutritional therapist Patrick Holfords example of curcumin as a potent agent against disease, despite the immunology primer provided as evidence.

Epidemiological and limited clinical evidence support a potential role for phytochemicals as human cancer chemopreventive agents (1). The effects of polyphenols – such as curcumin – are more pronounced in vitro, using high concentrations which are not physiological in vivo (2). Clinical studies confirm the poor bioavailability of curcumin (3)…

A ‘clinical’ dose of 3.6g curcumin is sufficient to achieve in vivo biochemical influence (5). Turmeric powder – a constituent of curry powder – contains 3.1% curcumin by weight (6), so ‘research-to-recipe’ equivalence would require consumption of 110g of turmeric powder daily. Mr Holfords exhortation ‘let the public eat curry’ is thus nutritionally irrelevant in the context of current research… [Emphasis added.]

If the public can not reasonably eat enough curry to reap the purported benefits of curcumin, then it might seem logical to advise them to take a supplement. However, in two interesting posts, researcher Abel Pharmboy discusses some relevant issues:

  1. Curcurmin for Cancer Part 1 asks the question, “Do concentrations of curcumin (or any compound) with anticancer effects in cell culture actually occur in the bloodstream of patients who take dietary supplements containing the compound?”.
  2. Curcurmin for Cancer Part 2 discusses the limited literature on the actual bioavailability of curcumin and explores whether “the [recommended] doses of an herb or dietary supplement may not achieve sufficient concentrations in the body to mimic the seemingly miraculous effects observed in cell culture studies”.

Abel Pharmboy’s scrutiny of the literature leads him to conclude that because of the way that curcumin is absorbed in the body, it would presently be necessary to take a massive dose, every hour (presumably until such time as somebody develops a time-release formulation) along with another agent to boost bioavailability. Even then, increasing a dose does not always increase the concentration in the blood levels. Theoretical calculations based on how much curcumin makes it into the bloodstream from an oral dose plus the theoretical dose necessary for an anti-cancer effect, indicate that you would need an hourly dose of between 40-200 grammes.

[T]here is no way to know how much of this curcumin product must be taken to achieve blood concentrations consistent with cancer cell growth arrest or cell killing.

So, yes, curcumin might be a promising anticancer compound but only if you could literally shovel quantities of it into the bloodstream. So, what should be done? Remember, I do this kind of work for a living and am a big proponent of natural products as a source of anticancer drugs… [Emphasis added.]

Abel Pharmboy concludes:

In the meantime, to continue marketing curcumin, even in a highly-bioavailable form, is misleading and gives false hope to patients.

At the very least, it is a tremendous waste of money.

In his Scientific American piece, Gary Stix alludes to the fact that curcumin does not have a wholly positive news flow. There are some questions about interactions with herbs, dietary supplements and drugs. Any substance that has as many possible biological impacts as those ascribed to curcumin may also be capable of unwanted biological actions. Stix points to research that indicates “the possibility that this spice may sometimes actually encourage the survival of cancer cells”.

Much of the present data about curcumin has been obtained from cell studies in laboratory settings or animal studies. Several interesting human trials are in progress that will provide more information and give a fuller picture of the action of curcumin on human physiology or pathology.

Marketing materials that emphasise relevant scientific terms can be very persuasive. The material for Holford’s curcumin supplement contains terms that will be familiar to people with a variety of illnesses, including cancer:

Research supports the wide-ranging beneficial properties of the curcuminoids, and especially curcumin. These include powerful antioxidant properties, modulation of the production of inflammatory signal molecules (prostanoids and leukotrienes), and inhibition of the growth of cells which have not properly differentiated, or whose growth pattern is abnormal. Because curcuminoids act through both intervention and preventative means, they are accordingly considered among the most potent of the known antioxidants.

It should be remembered that in his BMJ Rapid Response, Holford criticised Ben Goldacre because:

he attacks advice to eat turmeric for cancer protection, including that of the prostate…

However, although Holford is willing to disseminate the research news about turmeric with some enthusiasm, he has not commented on the research that questions:

  1. whether curcumin might stimulate the growth of some cancers
  2. the bioavailability of curcumin in supplements
  3. the implausibility of being able to take/afford sufficient curcumin to be clinically effective on a range of disorders

According to Catherine Collins (as quoted above):

The interpretation of clinical nutrition research and its application to prevent, treat or manage disease across individuals and populations should be confined to those capable of the practice.

Currently available supplements do not provide information about their bioavailability and its relationship to therapeutic doses for a number of implied symptoms and conditions (there are some weak advertising regulations that restrict the claims that can be made). If current and future research confirms the potential clinical significance of curcumin, the people who market it will probably need to research derivatives that would have the necessary bioavailability and can be proved to target relevant biological mechanisms that are involved in particular symptoms or illnesses. For now, it seems that there is no scientific basis to support Holford’s advice to take curcumin supplements.

Update July 8 2008: We are working on an update of our overview. Abel Pharmboy is currently working on an update to his posts about curcumin. In the interim he says:

My biggest concern is not so much that curcumin won’t work but rather that it is being formulated with piperine (under the brand name Bioperine here in the States) to increase curcumin bioavailability. This effect could also prolong the action of other drugs the person may be taking, increasing their chances of adverse effects.

…I haven’t yet seen any new data on the bioavailability issue but I am deeply concerned about attempts to modulate endogenous drug metabolism pathways to enhance the action of curcumin.



Filed under bioavailability, cancer, catherine collins, curcumin, Holford, patrick holford, supplements, turmeric

21 responses to “What’s The Excitement About Turmeric?

  1. daedalus2u

    You should look at the recent article in JAMA on supplemental antioxidants increasing mortality.

    I think this very much calls into question whether supplemental antioxidants have any benefit at all.

    If supplemental antioxidants worsen disorders associated with oxidative stress, then the state of oxidative stress is not regulated at all
    by antioxidants.

    I suspect that oxidative stress is a “setpoint” issue, and that dietary choice is part of the oxidative stress regulatory pathway. If the “oxidative stress setpoint” is low, then individuals select a diet rich in antioxidants. If the setpoint is high, they select a diet devoid of antioxidants.

    The robust association of a self-selected diet rich in green leafy vegetables with low oxidative stress is thus an effect of a low oxidative stress setpoint, not the cause of low oxidative stress.

  2. Shinga

    I take your point about the JAMA paper, Daedalus – I just chose to concentrate on curcumin here because Holford had explicitly referenced it in his BMJ Rapid Response and because he is regularly quoted as recommending it for its anti-inflammatory properties.

    And, I wanted to demonstrate that it is not possible to obtain what is currently thought to be a therapeutic dose from the diet. Plus, that even more so that with some vitamin or other supplements, there are significant issues concerning the bioavailability of a supplement that he is recommending.

    Regards – Shinga

  3. coracle

    Nice work Shinga, nicely detailed article.

  4. Claire

    Curcumin can bring people out in hives (literal rather than figurative) according to this article featured on Medcape a little while ago – http://www.medscape.com/viewarticle/552009_4 – “Contact urticaria from Curcumin”. It concludes:

    “Curcumin, which is used widely in traditional medicine, is also becoming more used in Western society in products such as nutritional supplements. A few cases of allergic contact dermatitis (type IV hypersensitivity) have been reported. We report two cases of contact urticaria from curcumin that were apparently produced by two completely different mechanisms, one immunologic and the other nonimmunologic. With the increasing use of this spice, we anticipate a rise in the cases of allergy to curcumin.”

  5. Shinga

    It is odd, isn’t it. There is concern in some quarters that we are introducing comparatively novel foodstuffs such as kiwi or sesame and seeing a substantial incidence of allergy to them – yet it is perfectly OK to recommend curcumin salves/supplements etc. to a novel population and not to caveat it with advice about dermatitis/allergy.

    Regards – Shinga

  6. Maria

    As a consumer, a parent of a childhood cancer survivor who passed recently, and wife to someone who may have cancer, we need something we can do to help ourselves and give hope. MD Anderson’s Dr. Aggarwal’s research is based around curcumin, his power point is available online, one slide of which compares all cancer types in the U.S. versus India and Japan. India has 2/3 lower cancer incidences per million across the board (except for mouth and that is attributed to the tradition of chewing betel nut root there), AND even 1/3 less incidence than Japan (so it beats that fish diet!)… India is of course generations into a vegetarian diet and also 10,000 years ahead in using turmeric/curcumin as a food source. BUT there is no way they consume as much turmeric/curcumin in their daily diet as used in western research: they may eat 2 to 4g daily (attainable by using supplements)! AND STILL they beat the U.S. by miles for lower cancer rates! Get with it people! What does it take to convince you? Turmeric/curcumin has been described by some as the poor man’s chemo. Well move over pharmaceuticals, we’re helping ourselves, if only preventatively.

  7. Do you think that, possibly, there is another explanation for the lower cancer rates that lie, sadly, in the mortality statistics? Some people are not surviving for long enough to get the cancers of old age – a sad paradox.

    The average Indian male born in the 1990s can expect to live 58.5 years; women can expect to live only slightly longer (59.6 years), according to 1995 estimates.

    And, it seems that there is a lot of evidence and good taste to support the virtues of the indian-mediterranean diet as it is known.

  8. Maria

    Hey again: I thought I’d include this from Andrew Weil:

    . . . Overall, turmeric appears to have significant anti-inflammatory and cancer-protective effects. These seem most evident at doses well below pharmaceutical strength, which suggests that it would be wise to consume more foods spiced with turmeric. But getting enough in food is not easy for Westerners. We are not familiar with using it, and large amounts taste bitter. Other than supplements, the best way I’ve found to consume turmeric is in the form of a cold, unsweetened tea. This is a popular beverage in Okinawa, the island culture famed for health and longevity. Convenient, tasty, instant forms of turmeric tea are easy to get there.

  9. Curcumin, the main active ingredient of turmeric, is not taken up very well from the GI tract. So taking lots of it in any form, including as a tea, is not going to get all that much more into your system. Thus the levels of curcumin that produce biological effects in CELLS (including in one of my own papers) are never going to be achievable dietarily. It’s that simple.

    And if you take Dr Weil as an authority on matter nutritional… well, caveat emptor.

    For a less than complimentary view of Dr Weil from a Harvard Professor of Medicine and ex-editor of the New England Journal of Medicine, see here.

  10. Sangya

    Can eating turmeric daily cause cancer as stated above

  11. Sangya, I don’t think anyone’s claiming that eating turmeric *causes* cancer – just that there isn’t good evidence that turmeric can be used to prevent or treat cancer.

    I’m not aware of any evidence that those of us who enjoy eating turmeric need to worry about it causing cancer. Very tasty stuff :) but, sadly, I wouldn’t expect it to cure or prevent cancer…

    • Anil


      I agree that eating turmeric will not prevent cancer . A proper diet that is high in fruits, vegetables and less in fatty foods can lead to reduced cancer . there is no magical bullet for cancer or any other deadly disease . Indians eat more of vegetables , fruits and less of meat and thus have lesser cancer incidence than US .

  12. Bob

    The bioavailability questions may be unfounded as it appears that the metabolites of curcumin, not included in the bioavailability criterion are potentially more effective than curcumin.
    Therefore, effective doses may be achievable, despite limited absorption as curcumin.

  13. Bob, it will be interesting to see if that study is replicated in other mouse or animal models and what the implications are for therapeutic dosages. Similarly, if it is effective for something more than oxidative stress relating to a single dose of a substance.

    There is a study in ageing mice that indicates that curcumin might be rather more effective than a derivative for some conditions.

    For the time being, it still looks like it holds that the commercial preparations that are currently available do not necessarily do what it says on the packaging.

  14. Claire

    from the current edition of FACT, a reference to a report on lead contamination of tumeric supplements:


  15. Claire

    The FACT link is not correct – here is the link to the Consumer Lab report:


    “WHITE PLAINS, NEW YORK — FEBRUARY 6, 2008 — Turmeric supplements have become popular in recent years but ConsumerLab.com warned today that some products contain high amounts of lead. Recent tests found a popular brand to contain 18.7 mcg of lead in a daily serving — the highest amount ever reported by ConsumerLab.com. A daily serving of another brand was contaminated with 8.3 mcg of lead. These amounts are well above those to which people are normally exposed and should be avoided. The State of California, for example, requires supplements with more than 0.5 mcg of lead to carry a warning label. Lead-contaminated products should be particularly avoided by children — who can experience lead toxicity with only 6 mcg per day — and pregnant women. …”

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  18. Rita

    I have been looking about for some information about turmeric since it has become a hot topic on a horse forum (don’t ask) I frequent. CAM treatments of any sort are highly appreciated in the “alternative” horse community and those of us who ask awkward questions of such credulousness receive very unsatisfactory replies. Recently a flood of turmeric advice, for both humans and horses has appeared – pages and pages of references to studies -“studies”? from all over. Although loath to believe that curcumin (or any other substance) is a panacea, I do wonder if there could be anything in the frequently made point that, since there can be no patent (can there?) on turmeric, Big Pharma could somehow quash useful lines of study? We know we’re not talking knights in shining armour on either side here…………………Any thoughts?

    • There are plenty of options to make money from turmeric-related patents – for example, I think there may already be a patent or two related to increasing bioavailability… Big pharma is much more likely to try to research and profit from turmeric (sometimes in ethically problematic ways) than to make futile efforts to quash research. Some in the pharma industry are also already making money from selling nutritional supplements without a good evidence base (including turmeric-related pills).

      I’ve got no brief to defend big pharma – but to critically engage with the industry it is important to understand how it does and does not work.

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