Turmeric is said to be the latest "blockbuster nutrient", helpful for "everything from heart disease to Alzheimers, asthma to arthritis." But is there any scientific evidence behind this claim, or is it just another example of the tendency to get hyped-up about certain food components, which may be doing more harm than good?
Food picture from Shutterstock
Turmeric is the yellow spice that gives curry its familiar colour. It has been used as a traditional medicine in much of Asia for thousands of years. As for "blockbuster nutrient", I'm going to assume the term implies a nutrient or food component that's especially powerful at preventing or curing disease.
There's good evidence that curcumin -- the primary active component of turmeric -- has many potentially beneficial biological properties, including anti-inflammatory, antioxidant, anti-proliferative and anti-microbial activities.
It shows promise in the treatment of a wide range of diseases, including Alzheimers, Parkinson's, cardiovascular disease and cancer. But the authors of this paper also note that much of the evidence for its efficacy comes from laboratory studies that usually didn't involve humans, so the evidence is actually for potential therapeutic effectiveness.
Curcumin clearly shows promise as a drug-like agent to treat disease (that is, it's extracted from turmeric, concentrated and then taken either through the mouth or by injection). But this doesn't necessarily mean that turmeric – the food that contains curcumin – is health-promoting.
We still need to work out whether eating the stuff is the right way to make it have a therapeutic effect, and look into the possibility that it may have some untoward side effects. For example, there's some evidence that it may promote cancer under some circumstances.
Picture: Steven Jackson
So the jury is still out on whether turmeric truly qualifies as a blockbuster nutrient. Continue to enjoy the occasional curry by all means, but it may be premature to start consuming large quantities of turmeric (or curcumin) on a daily basis just yet.
The claim that turmeric has some special health-promoting properties (so people should eat large quantities each day) aligns neatly with the concept of "nutritionism".
This term was coined by Australian sociologist Gyorgi Scrinis to describe an undue emphasis on individual nutrients rather than on the diet as a whole. Nutritionism is therefore a kind of "reductionism", that is, the simplification of a complex idea until it's distorted.
It is based on the false premise that we know enough about nutritional science to accurately predict how intake of individual nutrients will impact on human health and well-being. Scrinis also points out that excessive concern over the health effects of specific foods or food components can lead to adoption of potentially harmful fad diets.
He identifies three eras of nutritionism over the past century or so. These are the quantifying era, the good-and-bad era, and the functional era.
The quantifying era took off with the discovery of vitamins about 100 years ago. This quickly led to claims these essential factors were deficient in the general diet, so they had to be taken as supplements.
Many people today take supplementary vitamins, despite a scarcity of evidence that they help anyone other than those suffering vitamin deficiencies to the point of being ill because of them. In fact, evidence suggests taking supplementary vitamins may even lead to earlier death in some circumstances.
And one recent study found US children are actually in danger of toxic effects from over-consumption of vitamins even without supplementation. This is the unintended consequence of fortification of a wide range of foods with vitamins, just in case the normal diet doesn't provide enough.
It involves a certain level of irony -- being overly concerned about possible inadequate vitamin consumption may have inadvertently led to excessive vitamin consumption!
Fear and marketing
More recently, in the era of good-and-bad nutritionism, fear of excessive intake of particular nutrients has been added to the fear of nutritional deficiencies. Perhaps paradoxically, two of the major forms -- fat-phobia (fear of fat) and carbophobia (fear of carbohydrates) -- have co-existed quite happily for much of the past decade or so.
According to this branch of nutritionism, fat is bad and carbohydrate is good (or vice versa depending on your stand). Again, evidence is not conclusive that either fat or carbohydrate is bad as such. Rather, a moderate intake of each (as opposed to an extremely high intake of either) is likely to be most appropriate for good health.
A recent refinement of carbophobia is the conclusion by some writers (who usually have no qualifications or experience in nutritional science) that sugar is killing us all. This is a throwback to British physiologist and nutritionist John Yudkin's 1972 depiction of sugar as Pure, White and Deadly.
This concept temporarily disappeared under pressure from the fat-is-killing-us-all brigade, but is now making a strong comeback. The main difference is that the current sugar phobia is predominantly about fructose, which is one of sugar's two components, alongside glucose.
In the pop science literature, fructose has been accused of being the sole cause of obesity, heart disease and type 2 diabetes, and of being a toxin at any dose.
Picture: Kurtis Garbutt
Finally, Scrinis identifies the "functional food" era of nutritionism, which began about 20 years ago with the development of foods modified to provide specific health benefits.
Foods fortified with either long-chain omega-3 fatty acids (fish oils), plant sterols, probiotics or some other supposed health-giving component are becoming increasingly common in supermarkets. In essence, we're now being trained to worry about not getting enough functional components unless we buy specially fortified, and in many cases, more expensive versions of normal foods.
There are specific instances where food fortification is entirely appropriate; the addition of folate to a range of foods, for instance, appears to have reduced the risk of neural tube defects in newborn babies.
But unless there's a demonstrated public health benefit, or a diagnosis by an appropriate professional, it's best to ignore the latest nutritionism fad and follow this simple but elegant recommendation by Michael Pollan:
Eat food. Not too much. Mostly plants.
Chris Forbes-Ewan is Senior Nutritionist at Defence Science and Technology Organisation. He receives funding from the NHMRC.