We all know that fatty fish contain mercury-but now researchers are suspecting that many processed foods and drinks contain the toxic metal too. Bryan Hubbard reports
There's no such thing as a safe dose of mercury, not that anyone seems to want to say so. Drug manufacturers have consistently denied that the mercury-based preservative thiomersal (thimerosal in the US) might cause autism, yet they have quietly removed it from all their vaccines; dental associations have always claimed that amalgam fillings-which are 50 per cent mercury-are perfectly safe, and now they are under pressure from European legislators to stop using the compound, and several countries have already done so.
And, of course, everyone knows that oily fish like tuna and halibut have high concentrations of mercury in their bodies from swimming in polluted waters, yet the agencies that promote the fishing industry always seem to forget that fact.
But there's a source of mercury that nobody suspects-and one that our children are ingesting every day-and it could hold the key to a host of childhood developmental health problems, including autism and ADHD (attention-deficit/hyperactivity disorder).
It's not even seen as a health threat: instead it is celebrated as a breakthrough in food production.
The HFCS connection
Over the past 30 years, food manufacturers have slowly been replacing sucrose as a food and drink sweetener with high-fructose corn syrup (HFCS)-or 'glucose corn syrup' as it's known in the UK. In 1970, more than 83 per cent of the sweeteners consumed in the US were sucrose. However, by 1997, sucrose-containing food and drink had dropped to just 43 per cent, with 57 per cent using HFCS instead.
Nowadays, HFCS is found in virtually every processed food and drink-from Coca-Cola, Pepsi and Kellogg's breakfast cereals to processed breads and cakes.
But this advance in food processing may be delivering a new health threat, one that only a handful of researchers is uncovering: the sweetener contains mercury and may be a heftier source of the toxic heavy metal than even fish.
Renee Dufault found mercury levels in nine of the 20 HFCS samples she collected from processing plants. But the US Food and Drug Administration (FDA) did nothing in response to her findings, so she 'went public' with the information after she retired.
Dufault had discovered levels of mercury ranging from 0.005 to 0.570 microgrammes (mcg)/g of HFCS and as the average daily consumption of the sweetener per person is around 50 g in the US, consumers are very likely-and unwittingly-ingesting every day up to 28.5 mcg of mercury, one of the most toxic metals known to man.
As the standard 20-oz bottle of Coca-Cola contains around 17 teaspoons' worth of HFCS, it's easy to see why processed snack foods and soft drinks are easily a far greater source of mercury than fish.1
Snacking on mercury
Alerted by Dufault and her colleagues' findings, Dr David Wallinga and other researchers at the Institute for Agriculture and Trade Policy (IATP), an independent lobby group based in Minneapolis, Minnesota, went out and bought a range of commonly consumed soft drinks and snack foods sweetened with HFCS, and tested them for mercury.
Of the 55 items they randomly purchased, including products made by Quaker, Kraft and Nutri-Grain, the researchers found that one-third contained mercury. The amount of mercury varied enormously, with the highest level being twice the amount of the lowest. The highest levels were found in barbecue sauces, whereas colas and soft drinks contained no mercury.
Nevertheless, Wallinga and the other IATP researchers strongly emphasize in their report-entitled 'Not So Sweet: Missing Mercury and High-Fructose Corn Syrup'-that their findings are only a snapshot based on just a one-off purchase.
More important, they believe that the food and drink manufacturers are probably unaware that their products contain mercury, and may not even realize that mercury-grade caustic soda is being used in the processing of the sweetener.
And judging by the website of the UK's HFCS industry group, the IATP may have a point. As can be seen on its website www.highfructosecornsyrup.co.uk, the group reiterates that the FDA regards HFCS as a "natural product as the only two elements present in HFCS are fructose and glucose. Both fructose and glucose are naturally occurring sugars, and they also happen to be the sugars which form the disaccharide sucrose, which is commonly known as sugar".
While that is true as far as it goes, the HFCS advocacy site fails to mention that the sweetener is derived from corn syrup, a glucose-heavy product that would never contain fructose in its original form. In other words, the "natural" claim is being used out of context: fructose is indeed natural, but not in association with corn syrup.
And there's also no mention of the industrial processing required to get fructose into the product.
The industry response
American corn producers have been among the chief beneficiaries of the explosion in HFCS use, so it's not very surprising that its industry group, the Corn Refiners Association (CRA), was quick to refute Dufault's findings. But it did not respond to the IATP study and its discovery of mercury in a substantial number of snacks sweetened with HFCS.
CRA's president, Audrae Erickson, says the Dufault study was based on "outdated information of dubious significance". She claims that the industry has used mercury-free processing plants for several years-and yet, according to the IATP, four of the eight plants in the US still use mercury-based technology, and there may be many more plants around the world still reliant on mercury.
Erickson also reports that the FDA deemed HFCS safe in 1983 and again in 1996, whereas it was not made aware of Dufault's findings until 2005-since which time it has not issued any new statements on the safety of HFCS.
Erickson concludes by repeating the claim that HFCS is "natural" as it contains no artificial or synthetic ingredients or additives. But it seems to be something of a stretch to claim that any product is 'natural' after it has passed through three industrial processes and used enzymes to come up with its final form.
As Michael Jacobson, director of the Center for Science in the Public Interest, a US nutrition advocacy group, has said: "You're causing a change in the molecular structure and that shouldn't be considered natural." Instead, he believes that HFCS should be reclassified as an artificial sweetener.
So how did the mercury get into the HFCS samples in the first place? Although its advocates describe HFCS as 'natural' and even 'organic', it's nothing of the sort. While other sweeteners are based on cane and beet sugars, HFCS is a derivative of corn starch-and it comes about only as a result of various industrial processes.
In 1957, scientists discovered an enzyme that could convert the glucose in corn syrup into fructose, a process that was finally perfected only in the 1970s, thereby paving the way towards mass production of HFCS.
The process involves several steps and three different enzymes, and the result is a syrup with a 90 per cent fructose content. This is then blended down with untreated glucose-only syrup into a mix that is either 42 per cent or 55 per cent fructose.
Around 50 processing plants around the world, including eight in the US and three in the UK, are currently producing HFCS. And some of these plants-more correctly known as 'industrial chlorine' or 'chlor-alkali' plants-still use caustic soda (sodium hydroxide) in the manufacture of HFCS, although it's an outmoded form of manufacturing that's been replaced by safer technology in some plants. Other food ingredients, such as citric acid, are also manufactured at these plants.
The caustic soda is referred to as 'mercury-grade' or 'rayon-grade', which indicates that these plants are reliant on mercury for part of the process. Astonishingly, the plants regularly report that some of the mercury mysteriously disappears. In just one year, four plants in the US still using caustic soda each reported that around seven tonnes of mercury had been unaccountably lost.
The three UK plants report a similar story, although the environmental lobby group Oceana says that the mercury loss isn't so mysterious-it's pumped out into the air and into the general water supply, in its view.
In fact, according to the group's report 'Poison Plants', the three plants are responsible for a third of all mercury emissions in the air and nearly half of all emissions in the water supply of the UK.
It's not an enormous leap of imagination to suspect-given such cavalier safety procedures-that some of the so-called missing mercury may well be getting into the HFCS itself, as Dufault and her colleagues suspect.
The mercury load
While we are generally aware of the amount of mercury we are exposed to from the fish we eat and the amalgam in our dental fillings, no one so far has taken into account the additional mercury load we may be unwittingly ingesting from our snacking and drinking habits. If Dufault and her co-workers are correct in their analyses, the average person is swallowing an additional 28.5 mcg/day of mercury-and this figure may be even higher among children and teenagers, as they tend to eat more snack foods and drink more colas and sodas.
Some critics accuse Dufault and the IATP of being alarmist. Toxicologist Carl Winter, of the FoodSafe Program at the University of California at Davis, says that the most toxic form of mercury is methylmercury, the type found in the fish we eat, as this form is more easily absorbed into the body.
It's possible, he says, that Dufault and Wallinga have been measuring elemental mercury, thought to be not so dangerous. Not so, says the World Health Organization, which states that elemental mercury is "toxic to the central and peripheral nervous systems".
Even so, there's no such thing as 'safe mercury' in any form, and high doses can cause damage to the heart, kidneys, lungs and immune system.
What's worse, this unsuspected additional mercury load from snacks and soft drinks might also be a contributing factor to the alarming rise we've seen in recent years of cases of attention-deficit/hyperactivity disorder (ADHD), autism and behavioural problems among our youngsters.
As Wallinga says, "For me, the take-home message is really that this [HFCS] is a totally avoidable, unnecessary exposure to mercury."
10 un-green bottles
In 1970, sucrose was the standard sweetener in food and drinks, and was used in around 83 per cent of all products. By 1997, this had dropped to just 43 per cent of processed foods and drinks, and had been replaced by HFCS. Today, virtually all processed food and drinks, including breakfast cereals, breads and cakes, are sweetened with HFCS.
40 times too much
Currently, the US Environmental Protection Agency uses a Reference Dose (RfD) of 0.1 mcg of mercury consumption per kilo of body weight per day as the safe upper limit for a woman planning to have a child. So, for a woman weighing 70 kilos (154 pounds), the safe upper limit is 0.7 mcg of mercury a day. If the average daily consumption of mercury from HFCS is now 28.5 mcg, a 70-kilo pregnant woman would be ingesting 40 times more mercury than is considered safe for her child. At least 300,000 US newborns may have increased risk of learning disabilities from mercury exposure.
HFCS and obesity
There are a number of researchers who firmly believe that the introduction of high-fructose corn syrup into our food and drink has played a considerable role in the obesity epidemic that is very much in evidence in many countries.But frustratingly for them, they have been unable to provide evidence of a direct causal connection, although they can point to national statistics of population and health that appear to support their argument.
Human consumption of HFCS increased by 1,000 per cent between 1970 and 1990 while, over that same time period, obesity levels in the general US population climbed from 23 per cent to 30 per cent.
As HFCS was the only significant dietary change seen at that time, it's reasonable to assume, they argue, that it has played a major part in the obesity crisis.
In a study of 1,400 schoolchildren, around one-third of their caloric intake was from added sugars instead of the sugars found naturally in fruit and vegetables.1
In that same year, the Corn Refiners Association also reported that the average American had consumed more than 42 lb (19 kg) of HFCS.
Dr George Bray, a diabetes specialist at the Pennington Biomedical Research Center at Louisiana State University, has been a leading advocate of the obesity connection,2 and has come up with a novel explanation for why HFCS can make us fat.
He says that the fructose in HFCS is metabolized differently from ordinary sugar. "Table sugar gives the body 'satiety' signals, whereas fructose and HFCS do not," he says. In other words, you don't get sick of consuming HFCS, whereas you soon feel you've had enough of table sugar.
It's a view supported by the research of Peter Havel at the University of California at Davis. He has discovered that the body metabolizes fructose in a way that promotes weight gain. It does not trigger the release of insulin and leptin, hormones that help to suppress appetite, nor does it slow the body's production of the hormones that increase hunger.3
Nevertheless, other researchers have so far failed to establish that HFCS is indeed the main culprit behind obesity. The Center for Food, Nutrition and Agriculture Policy at the University of Maryland created an expert panel to look into the claims and reported that the evidence was either unreliable or inconclusive, while research comparing the effects of HFCS and general sucrose consumption has never been done.4
Researchers at the University of Rhode Island were also unable to provide compelling evidence of the harmful effects of HFCS over and above those that come from any other form of refined sugar. They also found no differences in the body's metabolic responses to HFCS and sucrose in lean women.5
And that seems to be the real point: all refined sugars-whether fructose, sucrose or HFCS-are bad for you and should be avoided by everyone. And, of course, the findings by Dufault and the IATP (see main story) that HFCS is contaminated by mercury offer a further reason to avoid the additive.
Some physicians have advocated the use of fructose for diabetics, believing it to be a safer form of sugar than sucrose, as it doesn't adversely affect blood glucose regulation.
But nutritionist Dr Alan Gaby warns that this is bad advice. Fructosecan badly affect other aspects of metabolism and plays a key role in the ageing process, he says. Worse, it can exacerbate the eye, circulatory and kidney problems that are already major health concerns in diabetic people.
Fructose can also cause bowel problems such as diarrhoea and, paradoxically, may be responsible for the current increases in diabetes, obesity and non-alcoholic fatty-liver disease.6
1. Nutr Rev, 2005; 63: 133-57
2. Am J Clin Nutr, 2004; 79: 537-43
3. Am J Clin Nutr, 2008; 87: 1194-203; J Clin Endocrinol Metab, 2004; 89: 2963-72
4. Crit Rev Food Sci Nutr, 2007; 47: 561-82
5. Nutrition, 2007; 23: 103-12
6. Altern Med Rev, 2005; 10: 294-306
Mercury - deadly in any guise
Throughout history, mercury-in all its various forms-has often been at the centre of health alarms. In recent times the focus has been on the methylmercury found in fish that swim in contaminated waters and in amalgam dental fillings, and that was used as a preservative in vaccines.
Mercury in all of its guises is toxic, although its effects depend on the way we absorb it. Mercury poisoning can result from vapour inhalation, ingestion, injection or absorption through the skin, and the most commonly affected organs are the brain, kidneys and stomach.
Organic mercury is most commonly found in antiseptics, fungicides, laundry products and wood preservatives. Of all the types of mercury, this is the most devastating to the central nervous system. It comes in three forms: amyl; short chain (more commonly known as 'methylmercury'); and long chain.
This form is more easily taken up by the body, and can even cross the blood-brain barrier and placenta. As it's the type found in industrial waste, this may be the kind of mercury found in HFCS-containing products, despite the claims of critics that it's most likely 'elemental' mercury.
Elemental mercury (Hg) comes in liquid form and its most common usages are in thermometers, barometers, dental amalgam fillings, paints and light bulbs.
It can be very damaging if it's breathed in, as it can then penetrate into the central nervous system and cause long-lasting neurological damage. But it's only mildly toxic when ingested by mouth.
Inorganic mercury is commonly found in car batteries, cosmetics, perfumes, antisyphilitic agents, perfumes, spermicidal jellies and wood preservatives. This form is highly toxic, and can be taken in orally and through the skin. It can cause life-threatening kidney damage and affect the central nervous system.
Until the Dufault and IATP reports, it was thought that the most common exposure to mercury was through eating contaminated fish. The unborn child in the womb is especially at risk, leading America's Environmental Protection Agency (EPA) to advise pregnant women, breastfeeding mothers and young children to avoid eating fish with a high mercury content such as shark, swordfish, mackerel and tuna. (Tinned tuna is not on the list.)
Health Canada advises that these fish should not be consumed more than once a week or, if you're a woman of childbearing age or a young child, no more than once a month.
Thiomersal (also known as thimerosal), the mercury-containing preservative used in vaccines since the 1930s, has been suspected of causing autism and other neurological problems in children.
In 1999, the US Public Health Service and American Academy of Pediatrics concluded that thiomersal should be reduced or eliminated from all vaccines. The result is that nowadays no vaccines contain the preservative.
Amalgam dental fillings have also been suspected of causing neurological problems, and several European countries have banned the use of such fillings in pregnant women and breastfeeding mothers.
What you can do
One:The simplest answer to the HFCS problem is to stop consuming any snacks or drinks that mention 'high-fructose corn syrup', 'HFCS' or 'glucose corn syrup' on the label. Not only does this mean that it contains a sweetener that may be contaminated by mercury, but it's also an indication that the snack is highly processed and also high in added carbs that can contribute to weight issues.
Two:If you have young children and so have more control over what they eat, try introducing more whole and unprocessedfoods into their diet. The best sources of natural sugars are fruit and vegetables.
Three:If you have teenagers, get them to read thisarticle and then have them show it to theirfriends too.
Four: Aside from the threat to their health and weight, HFCS may also be adding to their mercury exposure. For this reason it's important to reduce their overall exposure in other ways too, such as avoiding fish that may be contaminated by mercury. Check out the IATP website at www.healthobservatory.org for its Smart Fish Guide.
Also, if you have a mouthful of amalgam fillings, you may want to have them removed. This can be an expensive procedure, and it's crucial that you find a dentist who is experienced in doing the procedure. Often, in inexperienced hands, excessive mercury fumes are released into the body as the fillings are removed, and this may be more dangerous than leaving them in the teeth in the first place.