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

Thursday 30 October 2014

Cocoa and the brain

There is a small possibility an extract of cocoa could help older people be better at certain memory tasks - but the trial done so far is not good enough to show this.

A paper published in October 2014 was reported in the media as showing that cocoa helped put off age-related memory decline. As is often the case, while the actual paper was interesting, and highlighted something worthy of further investigation, what it demonstrates is more complex than the simple headline suggests, and at this stage offers substantive proof of benefits.

In the trial, a group of healthy people aged between 50 and 69 were split into four groups. Two groups spent three months on a diet that was high in cocoa, two on a low cocoa diet. At least, that's how the paper describes it - in reality the 'high cocoa' group took a supplement of 99mg of cocoa flavanols. To get this much naturally you would have to eat 25 individual chocolate bars (not recommended!) - I don't know how much that is in cups of cocoa, but I suspect it's a lot. Each group was also divided into half that were sedentary and half that took regular exercise.

The scientists then looked at two things - how a particular part of the brain responded in an fMRI scanner, and how well the test subjects did at two memory tests. What they found was that those on a high cocoa diet did significantly better at one of the memory tests - the equivalent, it was claimed, of being almost 30 years younger.

This is interesting, but it isn't enough yet to suggest we should all get out and start consuming lots of cocoa flavanols. The test groups were small with only 8 to 11 people in each. This doesn't mean that the results are meaningless, but it does suggest further tests are required. It has also been pointed out that the claim that result is statistically significant is doubtful. The value isn't what most scientists would consider significant - the results could be obtained in error with about 50 per cent probability, which isn't good enough to be considered useful.

What was claimed to be observed is that the cocoa increased blood flow to the dentate gyrus region of the hippocampus in the brain, which is thought to have a role in memory handling. In the trial, the high cocoa group did better at a memory test where they had to remember whether a shape they were shown was one of 40 they had just seen in a sequence. But they didn't do any better in a test where they had to recall words from a list, 60 minutes after three attempts to learn it.

Another oddity of the trial is that no improvement was found in those who performed exercise, even though in a previous trial by the same experimenters had found a benefit. This doesn't rule out the findings, but does emphasise the need to repeat the trial, several times and with bigger groups. Oh, and the authors declared no personal interest, but it wasn't strongly flagged up that the study was funded by the Mars chocolate company.

There seems to be some evidence here that this cocoa-sourced substance might help with the short-term recognition of shapes, which is something we get worse at as we get older. This can't be a bad thing if true. But it isn't a miracle cure for the way that ageing effect our memories, and taken on its own, this trial is not enough even to be sure of that.

You can see the full paper at Nature Neuroscience, though you would need a subscription to read more than a summary. It is Enhancing dentate gyrus function with dietary flavanols improves cognition in older adults - Adam M Brickman, Usman A Khan, Frank A Provenzano, Lok-Kin Yeung, Wendy Suzuki, Hagen Schroeter, Melanie Wall, Richard P Sloan & Scott A Small - Nature Neuroscience (2014) doi:10.1038/nn.3850

Monday 29 September 2014

Could dinosaur DNA provide cures for human diseases?

Despite Jurassic Park, we can't use dinosaur DNA for anything, because we haven't got any, but we could learn something from the way dinosaurs survived injuries.

In July 2014, the Daily Mail carried a headline 'Could dinosaur DNA provide cures for serious human illness? Ancient fossils reveal evidence of powerful immune systems beating diseases such as cancer.' This seems very impressive - and there is an interesting health story here, but the headline is totally misleading.

Researchers examining a 72 million year old dinosaur skeleton had found evidence that it had survived serious injuries that a mammal would not be able to survive, and speculated that it might be that the animals had healing abilities that could be of benefit, if we could discover the mechanisms behind them. The only way this would be possible is if similar effects can be found in modern day relations of dinosaurs. The closest living relations are birds, but it has been suggested that a better model would be alligators and crocodiles, which are much more distantly related, but which do seem to resist infection despite living in bacteria-loaded environments.

However, the headline itself is pure science fiction. Despite the entertaining possibilities of Jurassic Park, dinosaur DNA simply doesn't exist any more. DNA deteriorates with time, and however it is preserved, it cannot last longer than around 6 to 7 million years. (The oldest sample found to date isn around half a million years old.) As the dinosaurs died out 65 million years ago, dinosaur DNA can't do anything for us at all.

Wednesday 17 September 2014

Why food ingredients can have more than 100 percent

It's always a good idea to take a look at the ingredients lists on processed food, but it won't always make a lot of sense.

If you look at some food packaging, you will see that the manufacturers have something in common with the X-Factor. They believe that it's possible to give 110%.

There are two significant oddities in the ingredients list, for instance, of my cereal. One is the matter of nuts. Because it says that the product contains 10.5% nuts when in fact the true contents is only 0.3% - that's quite a big error. This is because neither peanuts nor coconut are actually nuts. But we'll let them off, because there is probably some sort of convention that allows them to come under this heading. (It can't just because they have 'nut' in their name, as 'Honey Nut Shredded Wheat', the cereal in question, has 'nut' in its name. So if that were the rule, the contents should read '100% nuts'.)

But the more interesting oddity is the maths. You might wonder what the problem is. With 84.1% wheat, 10.5% nuts and 2.8% honey, that still allows 2.6% for the other bits and pieces. But ingredients lists don't work like that. They have to be specified in order of weight - so there is more sugar than there is nuts, the list just doesn't mention how much sugar. With a minimum of 10.6% sugar, that makes a minimum contents of 108%.

We can get some idea of the quantity of sugar from the nutritional information. We are told that 100g of the product contains 15.9g of sugar - but we can't just take this number as the missing figure, as it will also include the sugar in the honey and molasses. So reasonably we can guess that the 'sugar' percentage is in the 10.6-12% range.

So what is going on? Thankfully, Nestlé has been helpful on the subject and told me this:
The basic maths does not add up and unfortunately this situation is replicated across many foods as they try to comply with QUID (Quantitative Ingredient Declaration) legislation. The complication comes from the requirement to list the amount of ingredients as they are added to the formula at each step. It is called the ‘mixing bowl’ rules.
In a simple process, this works well and the ingredients add up to 100%. In a process with many steps, and where moisture is lost in intermediate drying and toasting stages, the maths becomes more complex and illogical, and 100% is hard to achieve.   Each product must be viewed in isolation, and its manufacturing method affects the final result as well as the ingredients used.
We have to comply with 'The Food Labelling Regulations 1996' and its amendments.  There are two amendments which detail how we should declare the quantities of ingredients used, and the key requirement is in the second of these Amending Regulations, which states; 'Where the food has lost moisture as a result of treatment, the indication of quantity of the ingredient or category of ingredients used shall be expressed as a percentage which shall be determined by reference to the finished product”. 
 So there you have it. The percentages can't really be taken as sensible detailed information, just a broad brush guide. This doesn't of course, explain why peanuts and coconuts are nuts (no doubt another regulation), or why there is no percentage against sugar - but it does help us understand what is going on to allow NestlĂ© (and other food manufacturers) to give 110%.

Saturday 30 August 2014

Phone chargers and the environment

A plugged-in phone charger with no phone attached does use electricity - but not very much.

We are often warned of the dangers to the environment of leaving phone chargers plugged into the mains because they are still using current. This can seem a little counter-intuitive. After all, an electrical socket doesn't leak electricity when there's no plug in it, so why should a phone charger, if there is no phone attached?

Unlike the socket, the charger has something at work even if there is no phone present. The charger has to convert the high voltage AC current of your mains down to the low voltage DC used to charge a phone. This involves passing the mains current through a transformer, and transformers have two complete electrical circuits, one for the input and one for the output. This means that the input circuit does use power, even if there is no device to receive the output. (Contrast this with the electrical socket, where the circuit is broken unless something is plugged in.)

However, the power usage of such a charger when not in use is tiny - around 0.1 watts. Compare that with a traditional bright light bulb at 100 watts - it's 1/1000th the amount. So by all means unplug your phone charger when not in use, but don't think it's going to make a big difference. You can do far, far more by switching to LED light bulbs, fitting double glazing, turning the heating down by 1 degree, insulating your house better and all the other ways that are traditionally recommended for saving energy.

Monday 25 August 2014

What happens to fingernails and hair after death

I have included this slightly gruesome story under 'fun' rather than 'health' as it isn't a matter of practical concern, just curiosity.

It's often said that human fingernails and hair continue to grow after death, allowing artists who specialise in the grotesque to envisage strangely hairy and long-nailed corpses. In a sense 'grow' is the wrong word for these extremeties made up of a tough, structural protein called keratin (skin, hooves, horns and beaks are also made of different assemblies of keratin). This is because they aren't alive, so can't strictly grow, but rather are constructed by specialist cells in the body.

If we get past the word, though, the idea itself has no basis. The processes that produce hair and nails require a living body to provide the raw materials and to power the production with glucose. Although there aren't any detailed scientific studies testing for this, there is no reason to think that hair and nails would continue to grow, as there is no mechanism to 'power' their production once the body has died. It's a myth.

It has been suggested that the myth originated because skin contracts as it dries and may seem to make hair and nails a little longer a little while after death. According to the British Medical Journal, the myth has certainly been around since the late 1920s, when it was mentioned in the novel All Quiet on the Western Front.

Saturday 2 August 2014

Does water go off?

There is often amusement caused by seeing bottled water with a 'best before' or 'use by' date. Surely water doesn't go off? 

It's a neat paradox that pure water doesn't go off - but water still should only be consumed relatively soon after obtaining it.

This goes both for tap water, once poured, and bottled water, once opened. In both cases it is best kept in the fridge and should be consumed within a couple of days. It's not that water itself can degrade. It's a very simple chemical compound, H2O - surely about the best known there is - with one oxygen atom and two hydrogen atoms. And the water itself will be exactly the same after a year. The trouble is that lots of living things need water, and like water as an environment in which to live. There are plenty of airborne bacteria, fungus spores and more that are floating around all the time. Once water is exposed to air it will start to accumulate these and, over time, you will get yourself a nice colony, some of which is likely to be bad for you.

If you have no choice but to drink water that has been kept for more than a couple of days (of course, unopened bottled water is fine up to its best before date), boil it for several minutes first.

Sunday 6 July 2014


Yet another important natural compound that has roles to play in the skin in the body, but that is highly unlikely to have significant benefits when taken as a supplement.

It sometimes seems there's a new wonder chemical, touted by an American MD via his or website every 10 minutes that is claimed to have anti-aging or skin restoring properties. Look up phytoceramides online and you will find plenty of capsules containing this wonder material which, it is claimed, will 'fake a facelift'.

Ceramides play an important role in the skin, along with other long molecules like cholesterol, helping retain moisture and keep the skin firm. But as we have found so often, simply eating a substance does not mean that it will be magically transported to the appropriate parts of the body to support the naturally occurring versions. As far as your digestive system is concerned, ceramides are just another kind of fat to be broken down.

Applied to the skin, ceramides can help retain moisture - but no better than vaseline or any cheap and cheerful moisturiser. And taken as a supplement, there are no scientific trials demonstrating any benefit.

Friday 4 July 2014


For most of us chocolate is a wonderful treat – and as long as it’s consumed in moderation, it’s not a bad thing, either.

There is something very special about chocolate – and as long as we remember it is mostly fat, and treat it appropriately, it’s a confection that most of us can enjoy.

Some chocolatiers will tell you that the reason chocolate is so appealing is because of the tactile sensation of consuming it. Because it melts at the temperature of your mouth, the solid turns into a sensuous liquid on your tongue. And there is an element of truth in this. It is also the case that there are a range of active chemicals in chocolate that could influence our brains, and sugar has to be part of the attraction of the modern treat. But there seems little doubt that we also get a kick from a substance called theobromine.

This is a bitter tasting alkaloid, a term we often associate with drugs like morphine and natural poisons. Caffeine, nicotine, quinine and cocaine are all part of the alkaloid family, but none has the appeal of theobromine. A clue might come from the Greek origins of the name which approximate to ‘food of the gods.’ Theobromine is the compound that makes chocolate special. The main source in our diet is the cocoa tree. The seeds of this tree (misleadingly called cocoa beans) contain the fatty substance cocoa butter that is the main ingredient of chocolate.

Chocolate has been enjoyed as a drink in Central and South America for at least three thousand years, and has been popular in Europe since the seventeenth century. In its original form, the drink was bitter (it often had chillies added to give it more bite) – it was a European twist to add sugar and milk to make something closer to modern drinking chocolate. The familiar solid form didn’t arrive until the nineteenth century, which was also when theobromine was first discovered. The substance has similar effects on the brain to caffeine, which is probably why you will occasionally see it said (incorrectly) that chocolate contains caffeine. Theobromine can reduce sleepiness and in large quantities produces a jittery sensation. On the positive side it is a cough suppressant and can help reduce asthma symptoms.

Most of us have heard that chocolate is not good for dogs – and it is theobromine that is to blame. The darker the chocolate, the higher the concentration of theobromine, and the more dangerous it is. A small dog could be killed by as little as 50g of strong dark chocolate. Smaller doses will cause vomiting. This isn’t a problem limited to dogs, poisoning all mammals to some degree, though the speed at which theobromine is disposed of by the system differs from species to species. Cats are particularly sensitive to theobromine, but rarely eat chocolate because they don’t have sweet taste receptors and so don’t get the kick from sweets that humans (and dogs) do.

Theobromine is also poisonous to humans, though not to same the degree as dogs and shouldn’t cause concern. Almost everything is poisonous in a large enough dose (even water, for example) and toxicity is all about dosage. In the case of theobromine, humans have about three times the resistance per kilogram of bodyweight as does a dog, and are significantly heavier, so we are much less likely to be damaged by our treats. A dangerous dose for an adult human would involve eating more than 5kg of milk chocolate.

A number of health benefits have been claimed for chocolate, including reducing blood pressure, reducing stress, reducing diabetes risk and giving limited protection against bowel cancer. None of the trials that have come up with these results have been big enough or repeated sufficiently to be sure of the outcome. The effect on blood pressure was slight, the cancer results are only laboratory based and the stress test was poorly designed (and sponsored by a chocolate manufacturer). The diabetes results were based on compounds in chocolate called flavonoids, but the trial could not show if the flavonoids caused the benefits – and chocolate is not the best source of flavonoids (the study focussed mainly on berries and wine). Plus we know that excess sugar consumption, a major content of most chocolate products, makes diabetes more likely.

[NEW] A recent addition to the chocolate family is 'raw chocolate' which is being promoted as yet another superfood. What this means is that the cacao beans are not roasted as usual, but left outside in the sun to dry. It is claimed that this means there is less loss of nutrients and keeps more antioxidants. As we've seen elsewhere superfood claims are very dubious, and consuming excessive antioxidants seems to be bad for you - so given it has been suggested the raw process could increase the risk of bacterial contamination, there seems little reason to prefer raw chocolate. Eating chocolate for health doesn't make a lot of sense. A good balanced diet is the health part - chocolate is a fun excess.

Bearing in mind the high fat levels in chocolate, the balance of evidence is that that we can’t think of it as a healthy food, but rather one to enjoy in moderation.


This is the blog to accompany Brian Clegg's book Science for Life.

More information soon.