Is acrylamide in your toast really going to give you cancer?

Acrylamide has been in the news today, and this might be the understatement of the year. Front page newspaper headlines have been yelling everything from “Brits officially warned off chips” to “Over-cooked potatoes and burnt toast could cause cancer” to the marginally more restrained “What is the real cancer risk from eating roast potatoes or toast?” All this has been accompanied by radio interviews with everyone from actual scientists to professional chefs to people keen to share their roast potato recipes. I expect there have been television interviews too – I haven’t had a chance to watch.

Hey, what could be more traditional, or more fun, than a food-health scare in January?

Acrylamide

Acrylamide

Never fear, the Chronicle Flask is here to sort out the science. Let’s get to the facts: what is acrylamide?

It’s actually a rather small molecule, and it falls into a group of substances which chemists call amides. Other well-known amides include paracetamol and penicillin, and nylon is a polyamide – that is, lots of amide molecules joined together. Amide linkages (the CO-NH bit) are a key feature of proteins, which means they appear in all kinds of naturally-occurring substances.

And this is where the food-acrylamide link comes in. Because acrylamide, or prop-2-enamide to give it its official name (the one only ever used by A-level chemistry students), forms when certain foods are cooked.

Acrylamide occurs naturally in fried, baked, and roasted starchy foods.

Acrylamide occurs naturally in fried, baked, and roasted starchy foods.

It begins with an amino acid called asparagine. If you’re wondering whether, with that name, it has anything to do with asparagus, you’d be on the right track. It was first isolated in the early 1800s from asparagus juice. It turns out to be very common: it’s found in dairy, meat, fish and shellfish, as well as potatoes, nuts, seeds and grains, amongst other things.

This is where the trouble begins. When asparagine is combined with sugars, particularly glucose, and heated, acrylamide is produced. The longer the food is heated for, the more acrylamide forms. This is a particular issue with anything wheat or potato-based thanks to the naturally-occurring sugars those foods also contain – hence all the histrionics over chips, roast potatoes and toast.

How dangerous is acrylamide? The International Agency for Research on Cancer have classified it as a Group 2A carcinogen, or a “probable” carcinogen. This means there’s “limited evidence” of carcinogenicity in humans, but “sufficient evidence” of carcinogenicity in experimental animals. In other words (usually) scientists know the thing in question causes cancer in rats – who’ve generally been fed huge amounts under strictly controlled conditions – but there isn’t any clear evidence that the same link exists in humans. It’s generally considered unethical to lock humans in cages and force feed them acrylamide by the kilo, so it’s tricky to prove.

screen-shot-2017-01-23-at-22-10-46At this point I will point out that alcoholic beverages are classified as Group 1 carcinogens, which means there is “sufficient evidence” of carcinogenicity in humans. Alcohol definitely causes cancer. If you’re genuinely concerned about your cancer risk, worry less about the roast potatoes in your Sunday roast and more about the glass of wine you’re drinking with them.

But back to acrylamide. In animals, it has been shown to cause tumours. It’s one of those substances which can be absorbed through the skin, and after exposure it spreads around the body, turning up in the blood, unexposed skin, the kidneys, the liver and so on. It’s also been shown to have neurotoxic effects in humans. BUT, the evidence that it causes cancer in humans under normal conditions isn’t conclusive. A meta-analysis published in 2014 concluded that “dietary acrylamide is not related to the risk of most common cancers. A modest association for kidney cancer, and for endometrial and ovarian cancers in never smokers only, cannot be excluded.” 

The dose makes the poison is an important principle in toxicology (image credit: Lindsay Labahn)

The dose makes the poison (image credit: Lindsay Labahn)

As I so often find myself saying in pieces like this: the dose makes the poison. The people who have suffered neurotoxic effects from acrylamide have been factory workers. In one case in the 1960s a patient was handling 10% solutions of the stuff, and “acknowledged that the acrylamide solution frequently had splashed on his unprotected hands, forearms and face.” The earliest symptom was contact dermatitis, followed by fatigue, weight loss and nerve damage.

Because of these very real risks, the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have set occupational exposure limits at 0.03 mg/m3 over an eight-hour workday, or 0.00003 g/m3.

Let’s contrast that to the amount of acrylamide found in cooked food. The reason all this fuss erupted today is that the Food Standards Agency (FSA) published some work which estimated the amounts of acrylamide people are likely to be exposed to in their everyday diet.

The highest concentrations of acrylamide were found in snacks (potato crisps etc), and they were 360 μg/kg, or 0.00036 g/kg or, since even the most ardent crisp addict doesn’t usually consume their favoured snacks by the kilo, 0.000036 g/100g. (Remember that those occupational limits are based on continuous exposure over an eight-hour period.)

In other words, the amounts in even the most acrylamide-y of foodstuffs are really quite tiny, and the evidence that acrylamide causes cancer in humans is very limited anyway. There is some evidence that acrylamide accumulates in the body, though, so consuming these sorts of foods day in and day out over a lifetime could be a concern. It might be wise to think twice about eating burnt toast every day for breakfast.

Oh yes, and there’s quite a lot of acrylamide in cigarette smoke. But somehow I doubt that if you’re a dedicated smoker this particular piece of information is going to make much difference.

As the FSA say at the end of their report:

Your toast almost certainly isn't going to kill you.

Your toast almost certainly isn’t going to kill you.

“The dietary acrylamide exposure levels for all age classes are of possible concern for an increased lifetime risk of cancer. The results of the survey do not increase concern with respect to acrylamide in the UK diet but do reinforce FSA advice to consumers and our efforts to support the food industry in reducing acrylamide levels.”

This is not, I would suggest, QUITE the same as “Crunchy toast could give you cancer, FSA warns” but, I suppose, “FSA says risk hasn’t really changed” wouldn’t sell as many newspapers.

One last thing, there’s acrylamide in coffee – it forms when the beans are roasted. There’s more in instant coffee and, perhaps counterintuitively, in lighter-roasted beans. No one seems to have mentioned that today, possibly because having your coffee taken away in January is just too terrifying a prospect to even contemplate. And also perhaps because coffee seems to be associated with more health benefits than negatives. Coffee drinkers are less likely to develop type 2 diabetes, Parkinson’s disease, dementia, suffer fewer cases of some cancers and fewer incidences of stroke. Whether the link is causal or not isn’t clear, but coffee drinking certainly doesn’t seem to be a particularly bad thing, which just goes to show that when it comes to diet, things are rarely clearcut.

Pass the crisps, someone.


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Does drinking alcohol actually cause dehydration?

alcohol-effects

Today I came across this article: Drinking water doesn’t prevent a hangover, study says, which includes the memorable line: “[the] study concluded, the only way to prevent a hangover is to drink less alcohol.”

Now, at first sight, you might think that surely this simply another piece of work from the University of the Bleedin’ Obvious.

But hang on. Alcohol does dehydrate you, doesn’t it? Everyone knows that! After all, don’t you wee more when you go drinking, and wake up all sweaty and with a dry mouth after a ‘heavy night’? Surely this is all evidence of fluid loss? Am I really about to suggest we should consign ‘alcohol causes dehydration” to the collection of alcohol-based myths such as mixing drinks gives you a worse hangover (only if you drink more as a result), a night cap will help you sleep (only temporarily, overall it tends to disrupt sleep), drinking beer will cause a ‘beer belly’ (too much of any type of drink can cause weight gain), and so on?

Well…

1024px-Ethanol-3D-balls

There are many alcohols; ethanol is the one we drink.

Firstly, what is alcohol or, more specifically (the word ‘alcohol’ actually refers to a group of compounds), ethanol? It’s a simple molecule, containing only two carbon atoms, an oxygen and some hydrogen atoms. It’s produced, as we all learned at school (or possibly when attempting home-brewing), by yeast during the process of fermentation. Feed this clever little single-celled organism some sugar and voilà, it produces ethanol (C2H5OH) and carbon dioxide via a remarkably simple equation:

C6H12O6 –> 2C2H5OH + 2CO2

220px-Marula01

Marula fruit naturally ferments.

Humans learned this trick a long time ago and have been brewing for literally thousands of years. In fact it doesn’t even require human intervention – marlula fruit is particularly famous for becoming naturally alcoholic (although stories of monkeys and elephants using it to get drunk might be somewhat exaggerated).

We like drinking because, of course, of what it does to us. In medical terms, it’s a central nervous system depressant with significant psychoactive effects (sounds fun, eh?) In English, it reduces anxiety, making drinkers feel relaxed and happy. This accompanies a decrease in motor skills of course, which is why drinking and driving is illegal virtually everywhere (although exact definitions of what this means do vary).

But while alcohol is all natural, it’s not what you’d consider healthy. Every now and then someone drags out some data that suggests that low to moderate alcohol intake is good for you, but this sadly appears to be more wishful thinking than good science. In terms of disease, alcohol consumption has been linked with stroke, high blood pressure, several liver diseases, pancreatitis, a weakened immune system and a handful of cancers including mouth, throat, liver and breast cancers.

In fact, alcohol has been categorised by the International Agency for Research on Cancer as a group 1 carcinogen, which puts it in the company of such other delights as asbestos, radium isotopes, ultraviolet radiation, diesel exhaust and tobacco.

Enjoying-Dinner-copy

Give up alcohol before you worry about your latte ingredients.

Of course, the dose makes the poison. Lots of people enjoy low to moderate alcohol consumption quite safely. Still, I have to admit to being amused by health nuts that insist on a diet consisting of little more than raw vegetables, make a fuss about so-called GMOs, campaign for additives (none of which are anywhere close to being group 1 carcinogens) to be removed from food, and then post pictures of themselves drinking wine. You really want to improve your health? Never mind caramel colour IV in your latte, give up the booze.

So, alcohol isn’t a health food, or indeed drink. But to get back to the original question, does it cause dehydration? Well, it would appear that while it does do a lot of bad stuff health-wise, that’s not one of the bad things it does. In a study, men drank six pints of beer and were then subjected to a number of tests. As the subsequent PubMed article states: “All subjects had a slight hangover, but none was fluid depleted”.

Screen Shot 2015-08-29 at 18.22.08

Twin doctors Chris and Xand van Tulleken in a recent BBC documentary.

In a recent BBC Horizon documentary, twin doctors Chris and Xand van Tulleken collected all their urine during a night in which Xand drank 21 units of alcohol in one sitting (while his brother only had one drink), and next morning demonstrated that the volumes were the same. In other words, the excessive alcohol consumption had not, as is widely believed, had a significant diuretic effect.

Admittedly, this was only two people, and the PubMed study only involved six participants – small sample size is often an issue with such work. The Dutch study I mentioned at the start was much larger, which is one reason it’s useful. In that study, drinking water appeared to make little difference to the severity of the hangover experienced. The only thing that really mattered was, not surprisingly, how much alcohol had been consumed.

In fact it’s not well-understood what does cause hangovers. It would appear it’s linked to an immune system response. In very simple terms, getting blind drunk is a little like self-imposed flu. Drinking plenty of fluids won’t do you any harm, but it’s not actually a solution. Of course, there’s no virus involved here to keep the immune system on the warpath, so for most healthy people the best, and probably only, hangover cure is time.

So in summary, yes, we probably can chuck “alcohol causes dehydration” in with all the other alcohol myths floating around out there, but that’s not an excuse to have a pint after your workout.

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