Thursday 20 November 2014


Gluten is a complex natural molecule that gives dough the stretchy, gooey texture that makes great bread. For most of us gluten is harmless, but a few are intolerant, and others believe a gluten-free diet would benefit us all. What’s the truth?

Between 1 and 2 per cent of the population is gluten or wheat intolerant. They get stomach pains, constipation and diarrhoea, most often because they have coeliac disease, a genetic disorder of the small intestine where the immune system gets it wrong and thinks that the gluten is attacking it, causing inflammation. Rather more people claim gluten intolerance than actually have it – for the rest it is a ‘nocebo’, the negative equivalent of a placebo effect, where believing something is bad for you causes pains with no physical cause.

There are simple tests that your GP can perform to check if you do have a genuine gluten intolerance. If this proves to be the case, then it’s a matter of ensuring that the diet is gluten-free, something that is increasingly easy with a wide range of gluten-free products available in the supermarket. In general, food should be fine as long as you avoid wheat, barley and rye. (Oats, while not a problem in themselves, are probably best avoided also as they are often contaminated with gluten from other grains.) Other cereals like maize and rice are fine.

There has been something of a fad diet of avoiding gluten – the kind of diet often endorsed by celebrities rather than experts – in those who don’t have a gluten intolerance, probably on the assumption that people must be intolerant because there is something toxic in the gluten and that avoiding gluten must be ‘good for digestive health’. In fact, it’s the reverse – people who are gluten intolerant have a mutation that makes them react badly to a harmless substance that is a normal part of our diet.

The general argument for a gluten-free diet if gluten doesn’t cause you problems is open to interpretation. Here’s nutritional therapist Deborah Thackery, quoted in the Morrison’s supermar- ket magazine:
Gluten doesn’t need to be in sausages or many other foods in which it is often present. There is growing evidence that gluten is difficult to digest and while we need protein, the right sort of fats and plenty of vitamins and minerals, we don’t need gluten. All of these nutrients can be found in other, non-gluten-containing foods.
This doesn’t make a lot of sense as dietary advice – after all, fibre is hard to digest, but it’s still good for you (see Fibre). All the evidence is that supermarkets are using ‘gluten-free’ rather as they do the ‘organic’ label: as a way to put a considerable mark-up on a product that doesn’t cost them much more to produce. Gluten-free products can be a rip-off. Trials have failed to demonstrate any health benefit to a gluten-free diet for those who aren’t intolerant, and it makes it significantly harder to get the fibre (and some vitamins) we all need. What’s more, many gluten-free products are higher in fat than their normal equivalents, as something has to be used as a substitute to give the textural contribution of gluten. So, a gluten-free diet is best avoided if you don’t have a medical reason to be on one.

A review published in November 2014 highlighted that those who aren't intolerant shouldn't avoid gluten, but should go for products made from whole grain cereals. The report concluded:
There is overwhelming evidence of clear health benefits of a whole grain based diets featuring store cupboard staples such as bread and cereal made from lightly processed wheat.  The benefits are increased where whole grains have undergone relatively little processing... the scientific evidence behind many of the most popular wheat and carbohydrate free diets turns out to be surprisingly thin and selectively used... Whole grain products are undoubtedly good for health and given their multiple beneficial aspects could easily be described as a super food. It might be possible to argue that they are superior to many other fruit and vegetable super foods since they have multiple modes of action and provide both short- and long-term health benefits.
The review was funded by the company that makes Weetabix, however it was undertaken by the University of Warwick, which points out that the 'company had no input into the conclusions of the research'. While clearly such research is beneficial to the manufacturer, there is no reason to suppose that the funding would bias the outcome.

• Fibre
• Placebo effect

Tuesday 18 November 2014

Antibacterial handwash/ cleaners and cancer

A paper in late 2014 suggested a link between triclosan, the antibacterial agent in many hand washes, kitchen and bathroom cleaners, and liver cancer. This inevitably caused a fair amount of excitement in the press. But should we be abandoning these products immediately?

The trial involved mice being fed 3 grams of triclosan a day for six months. The mice suffered liver damage and as a result were more susceptible to cancer produced by other carcinogenic substances. What does this mean for us? It's almost impossible to say. To begin with, it is difficult to make a straight weight for weight comparison with animal trials. Dogs, for instance, are much more sensitive to the theobromine in chocolate than humans, weight for weight. But the best guesses we can make to see what the trial involved is that mice have a rough weight-for-weight comparison with us.

A mouse typically weighs about 20 grams, so they were receiving 3/20ths of their body weight in triclosan daily for six months. The average UK adult woman weighs about 70 kilograms, so the equivalent would be to consume 10.5 kilograms of triclosan a day for six months. A typical surface cleaner contains about 0.3 percent triclosan. So that would mean consuming the equivalent of the triclosan in 6,000 half litre bottles of cleaner every day.

This is not to say that it's a good thing to consume considerable quantities of triclosan - but this research provides no useful evidence on its lack of safety or on safe levels of use.

Let's look at the four main ways that we come across triclosan (and similar antibacterial agents).

  • It is found in antibacterial handwash. There is no evidence this removes bacteria from the hands any better than washing with ordinary soap. This being the case, it is best not to use antibacterial handwash, both because of any risk from the substance and (more likely) in case of the risk of bacteria developing resistance mentioned below.
  • It is found in antibacterial surface sprays. These do have some benefits in reducing bacterial contamination on surfaces and are probably still worth using.
  • It is found in some toothpastes, where it is suggested (with very limited evidence) that it can help with gingivitis and plaque. Best avoided. This can be difficult, as the toothpaste itself doesn't have a contents list - but search for your toothpaste and 'contents' on the web to get the information. The best-known brand containing triclosan at the time of writing is Colgate Total - though bear in mind to get equivalent quantities to the mice you would have to swallow around 12,000 tubes of toothpaste a day.
  • It is found in some cosmetics. There are no benefits other than as a preservative, but it is very difficult to discover which products contain it, and you are unlikely to consume much of your cosmetics, so this is unlikely to be a cause for concern.
Overall we ought to focus the use of antibacterial cleaners where they have the most benefit. There is limited evidence, though it hasn't been fully proven, that too high levels of antibacterial agents in the environment can trigger bacterial resistance to antibacterial agents or even antibiotics. While more evidence is required, it seems worth limiting use to surface cleaners.

You can see the original paper at the Proceedings of the National Academy of Sciences of the USA though you would need a subscription to read more than a summary. It is The commonly used antimicrobial additive triclosan is a liver tumor promoter. Mei-Fei Yueha, Koji Taniguchib, Shujuan Chena, Ronald M. Evansc, Bruce D. Hammockd,1, Michael Karinb, and Robert H. Tukeya, doi: 10.1073/pnas.1419119111

  • Chocolate
  • Hand washing