Will Vitamin D supplements protect me against colds and flu?

Vitamin D supplements are often combined with
calcium as a treatment for osteoporosis

No one likes getting respiratory tract infections such as colds. There is interesting news that a wide-ranging study shows that vitamin D supplements can reduce the risk of getting colds and flu, particularly in those with severe vitamin D deficiency.

This is encouraging, especially as it isn't based on a single small trial. However, it is worth repeating once piece of the report: '... 33 people would need to take vitamin D supplements to prevent one acute respiratory tract infection.' That's for ordinary folk - for those with severe deficiencies, it's only four people taking the supplement to get one prevention.

So there does seem to be an effect, particularly if you are in that deficient group. As we get most of our vitamin D from sunlight, that's most likely to be people who avoid exposure to the sun, or who live in countries with low levels of sunlight in winter.

Even so, it's best not to get too excited. Assuming your vitamin D levels are average, rather than extremely low, bear in mind that the chances are high that taking the supplement would not prevent you getting an acute infection. (The study doesn't not cover non-acute infections.) But this is one of the few examples suggesting that people who are generally healthy might benefit from vitamin supplements.

The study is published in the BMJ.

Crispy roasties and burnt toast

There's been an outbreak of news stories about cancer risk from over-cooked starchy foods because of the production of substances called acrylamides. If your roasties, chips and toast, for instance, are too dark, we are told that they could increase your risk of cancer. This is not news - it's an idea that has been around for a long time and was covered in Science for Life. All that's new is that the Foods Standards Agency (FSA) has launched a campaign called Go for Gold encouraging us not to cook these starchy products too harshly and to leave them golden coloured. Bizarrely they are using that well known food science expert, Olympic medallist Denise Lewis to publicise the campaign (see what they've done - go for gold?), and the FSA wants us to cut back.

As mentioned in Science for Life, some studies do show a small potential increased risk of a handful of cancers, so there's no harm in avoiding really dark fried or grilled starchy foods, which is what I recommended. However, these studies are not definitive - in fact at the moment the general view is that there is no strong evidence of risk from acrylamides - and even if the risk does exist, it is small enough to happily still enjoy the crunchy bits of roast potatoes.

To put it into context, lots of things we eat may well produce a very small increase in risk of cancer. Things like, for instance, those killer foods orange juice and celery. We know for certain that alcohol has the biggest influence on cancer risk of anything we eat or drink, and coffee certainly has some small risk attached. But it the grand scheme of things, worrying about these small risks is like worrying about being struck by lightning or being in a fatal train crash. It can happen. It will happen to some people. And you don't want to stand on a high hill holding a metal pole in the air when there's thunder nearby. But life's too short to worry excessively.

You can read more on the statistical aspect here.

Can a garlic soup conquer colds and flu?

I was fascinated to see a post on Facebook relaying a claim that a soup made with 52 cloves of garlic can 'defeat colds, flu and even norovirus.' Leaving aside the possibility that this is because anyone consuming that much garlic will never get close enough to anyone else to catch anything, it seemed a claim that was worth putting under the Science for Life spotlight.

The claim is from a two-year-old article on a website called Complete Health and Happiness, which as a source, I admit, did rather get my dubiousness sensors tingling. However, I decided to take it at face value and see what the claim was based on.

The website gives as its source a 'recent and significant finding from Washington State University' and helpfully provides a link - but this takes the reader to another so-so looking site called PreventDisease. However, this at least appears to have a link to the research - but it turns out the link just goes to the home page of the respectable Journal of Microbial Chemotherapy. While I struggled to find the precise article, a search on Washington and garlic did throw up a number of papers such as this one which reports the impact of an active chemical from garlic on Scedosporium prolificans in vitro. Most of the work on garlic seems to be in vitro - effectively in a test tube - which makes it impossible to draw any conclusions from it for consuming garlic soup. Lots of substances destroy disease-causing microbes in a test tube (washing up liquid, for example), but that doesn't mean that they will help if you swallow them.

Other papers did cover experiments with mice and humans, though as yet these were very limited and not providing sufficient information to be practical. However, what all the papers have in common is that (like the antibiotics the original website refers to) they are dealing with bacteria. There is nothing whatever in them about viruses. And so, I'm afraid, that there is no evidence that this soup will defeat colds, flu and even norovirus.

Don't get me wrong - garlic is good for you and almost all of us could do to have more vegetables in our diet. But don't think that eating a soup will protect you from infection.

Is Manuka Honey great for the immune system?

We are constantly being bombarded with the latest celebrity fad, so I'm grateful to an email from Chelsea asking if Manuka honey is great for the immune system.

The quick answer - no.

This is a honey produced by bees exposed to pollen from the Manuka tree, mostly in New Zealand and Australia. It sold at incredibly high prices for honey - as much as £50 or more for a small jar.

Unfortunately, this is a classic case of assuming something that has a topical benefit - if you use it externally - will have a benefit if consumed. And as is usually the case, there is no link.

Honey in general has a mild anti-bacterial action (as do many substances - washing up liquid, for instance) - and there is reasonable evidence that Manuka honey is amongst the best at this. So applied appropriately to a wound (and I'm not recommending just slapping honey on), it can in principle have a positive effect (though there are many other, cheaper and more effective anti-bacterial agents).

When you eat it, though, it has no impact on your immune system. As discussed in Science for Life:

Your immune system is not a single part of your body but rather a vast network comprising physical barriers like your skin, white blood cells, various different organs and a whole range of complex chemicals with literally thousands of different roles. ‘Boosting’ it by simply eating something is a bit like hoping to redecorate your house by throwing a capsule of paint at the wall.

And in this case there is no evidence that the honey will be anything more than an incredibly expensive sweetener, adding unnecessary sugar to your diet. See the Cochrane report for details on use of honey in treating wounds.

Acupuncture update

Science for Life has over two pages on acupuncture, concluding that it is primarily a placebo-based treatment with no other benefit, but with some evidence that it was effective in the treatment of lower back pain, a view that was, at the time, supported by a Cochrane review and the UK's NICE body, which authorises medical treatments.

However, the evidence has now been through a more thorough analysis, and NICE has changed its guidance to say that acupuncture should not be offered for that remaining area, lower back pain. It seems that the original NICE guidance was subject to a number of flaws and influenced by those with a reason to want acupuncture to be recognised by the NHS.

The weight of evidence now appears to be clear that the benefits of acupuncture, like many other alternative treatments, are solely those to be gained from the placebo effect. See this post by David Colquhoun for details of the problems with the earlier assessment and the new ruling.

What is A2 milk?

In Science for Life, there's a chance to see the pros and cons of milk in terms of fat, sugar and calcium content. But some years ago there was a case made that a substance in milk called A1 beta casein could be a risk factor for diabetes and coronary heart disease. What made this interesting was that there was a variant of the protein, imaginatively called A2 beta casein, that didn't have the negative risk - and it was possible to produce milk that only had this variant of the protein, called 'A2 milk', which would be healthier for consumers.

Unfortunately, a detailed review by leading science journal Nature found that the diabetes study could not be duplicated with larger, better experiments, while the heart disease study was 'small, short, in an unsuitable animal model and had other design weaknesses' - which is pretty damning even before it fails to be backed up with better experiments. As is often the case with this kind of finding, all too often irresponsibly splashed across the newspapers, the original studies were too small, used bad statistics and simply don't tell us anything useful.

The Nature review calls the A1/A2 hypothesis 'ingenious' - and if it had been backed up it would have resulted in a major transformation of the milk industry. Unfortunately, however, the idea had no credible evidence to support it. Single, small trials are just not enough to do anything more than point out a direction for more in-depth work. In this case, the in-depth work - the stuff we need to listen to - showed that the A2 phenomenon to be unsupported.

Thanks to Professor Etienne van der Poel for bringing this to my attention.

Are taller people more at risk of cancer?

Most of the newspapers have reported on a study from Sweden showing that taller people are more likely to get cancer. This follows an earlier study in 2011 which came up with similar results.

As a piece of news it isn't particularly helpful - if you are tall, there's not a lot you can do about it. But also it seems reasonably logical.

It's normal, in this kind of study, to factor out other potential contributory factors, such as being under/over weight, so effectively we are comparing like with like. If two people have the same body mass index and one is taller than the other, then the taller person will have more cells in their body. As cancer is, given similar environmental and genetic background, essentially a statistical disease, the more cells available, the more likely it is that there will be a cancerous cell or cells forming. So it doesn't seem entirely surprising as a result.

The figures show a relatively small difference, and like all such studies it is very difficult to be sure that everything else has been adequately controlled for. There does indeed seem to be a small increase in risk, but we are all subject to a whole host of risks that make us different to other people (diet, hereditary, environment, exercise, smoking etc.) so to worry about a small factor we have no control over seems unnecessary.

Retin-A and Retinol

There are two types of cosmetic 'science': magic and pharmaceutical.

The magic kind is where you take a substance that has value inside the body and use it in a way that can't deliver the same benefit. A good example is hyaluronic acid. This was original discovered as part of the gunk that fills eyeballs, and later was shown to be an important part of the matrix that supports cells in the body. The way it is generally sold is that it somehow replenishes this support function, plumping up skin. But this is a bit like saying that food gives you energy, so if you plaster food on your skin you should feel energised.

The good news about hyaluronic acid is that is a genuine humectant - it grabs water, so acts as a reasonable moisturiser - but no better than much cheaper substances like vaseline.

Products with a pharmaceutical background, on the other hand, certainly have an effect, but we have to recognize that all pharma comes with side effects, some of which can be worse than the condition treated. And they need to be used with care. Often the cosmetic industry gets round this by putting so little of an active substance in a product that it doesn't risk side effects, but equally produces very little in the way of results.

So we come to our topic, Retin-A, Retinol and various other names applied to chemical variants on Vitamin A. Retin-A is a brand name for tretinoin, aka retinoic acid, the carboxylic acid derivative of Vitamin A and has been a topical treatment for acne since the 1960s. In the 1980s it was accidentally discovered that it seemed to reduce the appearance of skin wrinkling. Since the original anecdotal benefits there has been some research suggesting positive results. It has since been sold as a skin treatment in the US, though is not widely available in this form elsewhere because of its pharmaceutical nature.

Weaker and more dilute forms turn up in commercial skin creams, often based on retinol, one of the animal forms of Vitamin A. In these cases there may be a small effect, but it certainly will be limited as the dosage is restricted to avoid the side effects. In the more concentrated form (Retin-A, Renova etc.) it can have make a more noticeable change, but can result in a number of side effects, most notably skin irritation and burning, dryness and increased sensitivity to sunlight. For some users this fades over time, for others it will come back each time the cream is used - and the product is only effective while in regular use.

Overall this seems a borderline product. It does have a genuine effect, but it is a pharmaceutical product with known side-effects being applied outside its intended use. As such, the negative aspects may outweigh the positive, and I have not been able to find any research on long-term impact, which may be another concern.

Links

• Hyaluronic acid - page 386

Can drinking tequila help you lose weight?

If I had £1 for every new story where [insert your favourite alcoholic drink] is shown to have some positive effect, I could retire immediately. And, surprise, surprise - this is yet another such story that has no basis whatsoever as far as the headline goes. But it does have one interesting possibility for an alternative to sugar.

All the press coverage comes up with statements like 'You won't believe why drinking tequila might actually help you lose weight,' or 'You won't feel so guilty after that extra shot.' To be clear. Tequila will definitely not help you lose weight, and even if the implied benefit were true, which it isn't, the dangerous impact of alcohol would far outweigh the benefit. In fact the research specifically points out that the beneficial substance this report is based on, of which more in a moment, is not found in tequila.

Hidden beneath the 'drink your way to weight loss' stories is a much more interesting possibility. The actual research, reported at an American Chemical Society meeting, showed that the agave plant, which happens to be the plant tequila is produced from, contains some very interesting sugars called agavins. Instead of the usual fruit sugar fructose, these sugars are fructans, which are effectively fructose polymers. The result of this different structure is that the sugars can't be used by the body and so don't have the negative impact of sugar. They even appear to somewhat reduce blood sugar levels - and they still give a sweet taste. Admittedly not as sweet as a conventional sugar, but still offering the hope of a sweetener that has few potential side effects (some people are intolerant to agavins) and no negative impact on blood sugar levels.

It should be noted that this was a trial on mice, and was funded by a food company and a company making agave products - but that doesn't necessarily mean that the research is dubious.

A really interesting story - but almost entirely hidden by the baloney about tequila being 'good for you.'

Links

• Artificial sweetners - page 9
• High fructose corn syrup
• Sugar - page 102

Balancing hormones

Thanks to reader Yuka for pointing out the wide range of products that are advertised to 'balance the hormones', particularly targeted at women consumers.

There are some parallels here with attempts to 'boost the immune system' (see page 301 in the book). We aren't talking about a simple system or individual entity that can somehow be put back in balance by taking a supplement.

Hormones comprise a vast range of signalling chemicals produced by various glands in the body to control different functions from digestion to sleep and the reproductive system. Various illnesses result in unusual hormone levels, and require proper medical treatment. But the idea that you can 'balance your hormones' by eating something seems more oriented to the ancient and baseless idea of your body having four humours that need to be kept in balance. There is no good scientific evidence for taking supplements to balance your hormones, nor any clear mechanism by which many recommended supplements could even have an influence on hormone levels.

There are many hormones and many products said to 'balance' them, but this article gives an example of some specific products claiming to be 'bioidentical hormones', recommended by their vendors as alternatives to hormone replacement therapy, and also said to improve quality of life. As the article makes clear (with proper testing to back it up) these products have serious potential problems.

Overall, then, if you suspect you have a hormonal problem, the last thing you want to do is self medicate. See your GP.

Vitamin B17, aka laetrile or amygdalin

Flipping through Facebook today I saw someone had shared a post titled 'Vitamin B17: the greatest cover-up in the history of cancer.' There's certainly a cover-up here, but not in the way that was intended by the author. Substances labelled 'Vitamin B17', 'laetrile' or 'amygdalin' (technically a slightly different compound) are sold as cancer cures that the pharmacological industry doesn't want you to know about. But they aren't anything of the sort.

Amygdalin is found in apricot pits, while laetrile is a synthetic compound which is similar in structure. Despite the 'vitamin B17' label it is frequently given, this is not a vitamin in any way, shape or form. Amygdalin, which enzymes can break down to give off the deadly hydrogen cyanide, was tested as a cancer treatment over 100 years ago and found both not to work and to be extremely toxic. Neither of these problems seem to have got in the way of those promoting it as a cure.

One of the reasons that laetrile continues to be rediscovered as a supposed cure is that it was heavily marketed by a self-styled doctor, Ernst Krebs who claimed that cancer was caused by a deficiency of 'vitamin B17.' For decades there have been attempts to make money from those suffering from cancer by promoting this unsubstantiated substance as a cure.

A thorough review of studies of the use of laetrile in the treatment of cancer made in 2011 concluded: The claims that laetrile or amygdalin have beneficial effects for cancer patients are not currently supported by sound clinical data. There is a considerable risk of serious adverse effects from cyanide poisoning after laetrile or amygdalin, especially after oral ingestion. The risk-benefit balance of laetrile or amygdalin as a treatment for cancer is therefore unambiguously negative.

Copper bracelets for health

It's easy to find shops selling copper bracelets and other copper-based things to wear that it is claimed will help reduce chronic pain and swelling, reduce the impact of arthritis and more. But does it work?

Copper is a relatively common element that we need to consume in trace quantities for a number of functions of the body, but we get plenty of copper in our diet and an excess can result in liver damage and brain deterioration, so it's not something to take as a supplement without medical advice. But how about wearing it?

The immediate scientific response is to wonder how wearing a copper bracelet, say, could have any impact on pains in other parts of the body. One claim, for instance, is that the body can draw metal out of the bracelet to help with cartilage replacement. There is no mechanism by which this could happen - and even if copper was absorbed, it would do more harm than good. This seems little more than an appeal to magic.

A study was carried out in the UK in 2013 which reported that wearing copper bracelets had no impact on these problems, and that any perceived benefit from wearing copper was simply a placebo effect.

On a separate claim, it is just possible that copper compounds, appropriately applied, could have some antibacterial benefits - but it isn't enough to wear a piece of metallic copper, and there is no evidence as yet of a wearable product containing copper or copper compounds have such a benefit.

So by all means wear a copper bracelet if you think it looks nice - but don't expect it to make you healthier.

Herbal medicine

Herbs have been used in all cultures as medicines and some have real medical benefits. but care has to be taken with herbal cures as they are poorly regulated.

In historical times, herbs played a major part in our medical treatment, though as early as the 17th century, when herbalist Nicholas Culpeper published his Complete Herbal, there was a debate between the proponents of herbal and chemical medicine. With a modern understanding of the active ingredients in herbs we can see that the distinction is artificial. Herbs are an effective source of chemicals that have an active effect on the human body, though often this effect is improved if the chemical agent is refined and modified.

So, for instance, willow bark, containing a chemical called salicylic acid, has been used to help reduce pains and fevers for at least 4,000 years. Unfortunately salicylic acid causes sharp stomach pains and can cause internal bleeding – so that relief came with a price. At the end of the 19th century, the German pharmaceutical company Bayer produced a painkiller called aspirin, which modified the active ingredient to the much less aggressive acetylsalicylic acid. The active ingredient of medical herbs has been repeatedly isolated and improved. Quinine for malaria, atropine and digitalis for the heart, for instance, all originated with herbal cures, but are much better and safer in their pure chemical form.

Herbal medicine has a strong presence in China, and there are herbal medicine stores on many of our high streets. Unfortunately, current herbal medicine still uses theories with no basis (such as employing a herb with the same shape as an organ of the body to treat that organ) and has rarely advanced. There are also well-documented dangers in taking herbal medicines at the same time as other medications. It is always worth checking with your doctor first.

The popular herbal treatment St John’s Wort, for instance, which has proved effective in helping with mild depression, has as many possible side effects as any prescription drug, from gastrointestinal pain to dizziness. It can cause serious problems with anti-HIV, anti-cancer drugs and contraceptive pills; plus it generally reduces the effectiveness of the transport mechanism carrying drugs into the bloodstream. Because of this it has been banned in France. You can’t assume that because a treatment is herbal it is safe in all circumstances.

Another significant problem with herbal treatments is that a herb rarely contains only one active ingredient – and it is almost impossible to give a well-controlled dose, as the amount of the chemical in a herb will vary from plant to plant. Where a prescription medicine will have isolated the useful chemical, in a herb you could be exposing yourself to a whole range of potentially unpleasant substances to get the beneficial one. But more worrying still is the reality that there is very little regulation of the quality of herbal medicines.

A major US study in 2013 analysed 44 processed herbal prod- ucts and 50 medicinal herbs from a range of suppliers. The results were shocking. Less than half of the products actually contained the labelled main ingredient. Nearly 60 per cent contained herbal species that weren’t listed on the ingredients. A third also contained fillers and contaminants that weren’t on the label. In three of the companies tested, none of the products contained what they said they did. In other studies, herbal medicines have been found to be contaminated with dangerous heavy metals and other extremely poisonous substances.

*UPDATE* In February 2015 the New York State attorney general's office accused four major US retailers of selling herbal supplements that were fraudulent and in some cases were contaminated with unlisted ingredients. These weren't backstreet herbalists, but Walmart, Walgreens, Target an GNC. Approximately four out of five products didn't contain any of the herbs on their labels. Many contained little more than rice and houseplants.

The products with non of the herb in included Gingko Biloba, St. John's Wort, Ginseng, Echinacea and Valerian Root. Typical fillers were rice, asparagus, wheat or grass and garlic, though oddly many of the samples actually claiming to be garlic had none in. This really emphasises how much you are at risk of getting anything but what you expect when buying herbal remedies.

So, while there are certainly benefits to some herbal remedies, the lack of a proper regulation and of a testing regime paralleling that used on conventional medication means that there will always be significant risks attached.

E-cigarettes

Electronic cigarettes, or e-cigarettes have become commonplace as a safer substitute for the real thing. But are they safe to use?

One important consideration is that at the moment e-cigarettes are not regulated in many countries, including the UK. This means, like all unregulated products that have a potential health risk, you don't know that what you are using contains only what is supposed to contain. There is no magic wand for this, apart from buying from legitimate brands, ideally through a known major retailer, who will hopefully have done some checks for you.

The liquid you put in an e-cigarette (assuming it's a legitimate one) has nicotine, extracted from tobacco, flavourings and suspension fluids that work well with the vaporising process, typically propylene glycol and glycerol which in themselves are both pretty much harmless.

When you inhale this stuff, either actively or as a passive recipient of someone else's vapour, you are taking an aerosol - fine droplets of liquid - into your lungs. This can happen perfectly naturally, for instance with some strong-smelling natural substances. But having unwanted material in the lungs always has the potential for risk, specifically for causing cancer.

The biggest concern here is not the original chemical constituents, but rather than the heating process that sends the vapour out can break down some of the suspension fluid into formaldehyde. In small quantities this isn't a problem - our bodies deal with formaldehyde all the time - but in larger quantities formaldehyde is a carcinogen, particularly around the respiratory system.

At this stage there hasn't been enough research to confirm the early findings, but if the data available so far is correct, heavy users of e-cigarettes could have a significant cancer risk - possibly as high a risk as from smoking in the first place. In the balance, cigarettes have a whole range of negative impacts, not just lung cancer, so this isn't an argument for going back to smoking cigarettes. And if an e-cigarette is used as a vehicle to fairly quickly stop smoking altogether, on balance it may be worth using (though patches, gum and other sources of nicotine don't carry this potential risk).

However, what this does suggest is that no one should use e-cigarettes just for the sake of it, and should only consider using them in a tapering off programme to quit smoking if options like patches and gum aren't working. And it also means we ought to see e-cigarettes banned from all the locations we ban conventional cigarettes - as the risk from passive inhalation is certainly present.

For the future there are a number of steps that should be taken. E-cigarettes should be regulated and licensed as vehicles for drug dispensing. There needs to be significantly more research into the production of formaldehyde and any other potentially dangerous substances. And there should be research into safer suspension fluids.

The principle of e-cigarettes is good, but there is evidence that this still very young product needs significantly more work to ensure that it is a safe substitute for tobacco.

Screens and eyes

For as long as we’ve had televisions they have been accused of damaging our eyes – but now, with screens everywhere, what’s the true picture?

When I was young, older people were always telling us not to sit too close to the TV or to spend too much time watching it. Yet back then, we only had a fraction of the screen time that most of us experience today. You may well spend all day at work looking at a computer screen, then come home to spend the evening in front of the TV. And what were you doing in between these times? Looking at your phone or tablet.

In 2014 there was a scare story that overusing smartphones may damage the eyes. The concern was that the light from LED screens contains more blue/violet light than the natural light that best suits our eyes, and the higher energy blue/violet light can overload the sensors on the retina, increasing the risk of macular degeneration, a common cause of blindness.

The story particularly highlighted the risks from smartphone use, where the screen is held considerably closer to the eyes than a computer or TV screen and is often used in lower lighting condi- tions, where the dilated irises of our eyes allow more light in.

We have to approach this story with a little caution. There is no study showing that exposure to screens, even smartphones, causes eye problems – this is extrapolating from laboratory-based evidence that light in this region can cause damage to the type of cells used in the retina. So at the very most, this is a precautionary warning as yet.

What is certainly true is that our eyes don’t respond well to being focused as closely as a smartphone requires (TVs are usually positioned at a better distance) for long periods of time, and this can cause eye strain. Taking a break from screens for at least five minutes in each hour, and a few longer breaks during the day is highly recommended. Furthermore, regular screen users – which is pretty well all of us – should have regular check-ups with an optician.

UPDATE: In December 2014 a different study showed that people who read backlit screens in before going to sleep produced less of the hormone melatonin. This can make it harder to get to sleep, and in the long term, sleep deficiency can produce significant health problems. As yet the evidence is relatively limited - this was a very small study with just six people on each kind of book. However if you do have trouble getting to sleep, and you read from a screen for your bedtime reading it is worth switching to a paper book (or an e-ink reader like a basic Kindle that doesn't have a backlight) to see if it helps make sleep more easy. Ideally avoid close backlit screens (including phones and computers as well as tablets and backlit e-readers) for a couple of hours before trying to sleep. TVs don't seem to be a problem as we don't sit anywhere near as close, so the blue backlight is a relatively small part of our incoming light - and the generally darker coloured picture of video is better than the stark white of a page to read. If you have to use a backlit e-reader, try turning down the brightness.

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

LINKS

• Chocolate
• Hand washing

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.

Phytoceramides

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.