19 January 2018
Cancer is a complex disorder and although it’s understandable why simple dietary measures to prevent or cure cancer are so appealing in this very challenging condition, the reality is that simple narratives heralded in the media should be treated with scepticism. Yet they are common – earlier this month a case study was reported where one woman claimed that turmeric supplements cured her myeloma (a form of blood cancer).
Turmeric, the spice that gives curry its yellow-orange hue claimed by some as a ‘superfood’, is popping up as ‘golden turmeric lattes’ and ‘turmeric tonics’ on the high street and in new supermarket products.
But what do we know about turmeric and cancer prevention?
Curcumin, a polyphenol, is the principal active component of turmeric – although this only accounts for about 3% of the spice composition. Research from animal and in vitro (like cell cultures in a dish) has shown that curcumin, typically in extremely high doses, may have anti-inflammatory and antioxidant properties, and suggests it has some potential to inhibit the development of several types of cancer cells.
These results have attracted much attention and although this data may help to increase our understanding of how polyphenols may contribute to anticancer mechanisms, whether turmeric in the diet has therapeutic effects in humans cannot be extrapolated from these types of studies. Besides all the talk and attention there is a striking lack of well-designed large double-blind, placebo controlled clinical trials which are needed to demonstrate a clinical benefit, and of the few human studies undertaken high doses are used which would be difficult to replicate in the diet.
For example, a non-blinded and non-controlled trial in smokers with aberrant crypt foci (ACF) [precursors for colon cancer] suggested that 4 g/day of curcumin significantly decreased ACF formation. However, 4 g of curcumin a day would equate to well over 100 g of turmeric powder daily, when a typical curry recipe uses 1 tsp (around 3 g) for 4 people.
Furthermore studies consistently show that even with high oral doses systemic bioavailability of curcumin, the degree and rate at which it is absorbed by the body's circulatory system, is poor. So it is questionable whether curcumin taken orally in concentrations that have shown in vitro activity will be effective.
Should we all be consuming turmeric to prevent cancer?
The bottom line is while there is no reason why turmeric can’t be enjoyed in everyday cuisine as part of a healthy, balanced diet caution should be taken in thinking that turmeric is the magic bullet for cancer prevention or cancer treatment or indeed other diseases because these health benefits are currently unsupported by science. No single food or ingredient is going to transform the nation’s cancer risk. Healthy dietary patterns and other lifestyle factors are likely to be far more important than turmeric on its own.