June 30, 2002
Focus: The killer question
Does fried food cause cancer? As evidence mounts of a hidden toxin in our diet, John Elliott and Jonathan Leake investigate the discovery that could change our eating habits for ever
On the seventh floor of the World Health Organisation (WHO) headquarters in Geneva last Thursday, an air of excitement and apprehension was building. Excitement, because for three days 25 top scientists from across the globe had been closeted in a small conference room, their heads bent in urgent discussion over a scientific discovery of global significance. Apprehension, because the nature of that discovery was one that would raise serious concerns over the most basic aspect of our daily lives - our eating habits. The reason why these men and women had flown to Geneva was a chemical called acrylamide. Until recently its presence had been detected only in specialist products and cigarettes. Although known as a probable cancer-causing agent, its use was confined to industrial processes such as paper manufacturing and the production of plastics, or in water filtration where any exposure could be controlled and monitored.
However, on Thursday afternoon it was time for the scientists to announce that acrylamide could be playing an unwanted, sinister and previously unknown role in our lives.
Acrylamide is present, they stated, in a huge range of foods that form a staple part of most western diets. Tests on chips, crisps and high-starch fried foods showed alarming results, with acrylamide levels up to 400 times over the recommended limit. In health terms the news could not have been more bleak.
“It is likely that this is causing cancer in the human population,” said Dr Jorgen Schlundt, head of food safety at the WHO. “It’s a genotoxic substance - which means it goes into the genes and changes something and causes cancer.”
Schlundt explained that he was not talking about just another food scare. “The experts were unanimous and clear that this is a major concern,” he said, adding that a “significant” proportion of the 30%-40% of cancers that are linked to diet could be caused by acrylamide.
In Britain experts are openly comparing the discovery of acrylamide’s role to the breakthrough in establishing a link between smoking and cancer. Several are warning their own families to avoid eating high-risk foods, such as chips, until more is known about the dangers.
At present the unanswered questions are as troubling as the discovery itself. First, nobody has any idea how acrylamide came to be in our food. Tests have shown that fried or baked products pose a particular risk, and that it is the cooking process rather than the foods themselves that seem to be responsible.
Second, it is difficult to estimate the extent of the impact on our health of acrylamide in foods. Members of the Swedish team speculated that it could be responsible for “hundreds” of cancer cases in their country. Others fear that the figure could be much higher.
Either way the scientific community worldwide is unanimous in declaring that more research is needed. Until then, both the WHO and Britain’s Food Standards Agency (FSA) have simply restated the need to eat a balanced diet.
In California, of course, things are moving in a different way. According to health campaigners, a lawyer has already demanded that McDonald’s and Burger King place a cancer warning on their chip packets, in accordance with the state law on carcinogens.
The story of acrylamide begins in the Hallandsasen hills in southern Sweden in 1997 with a disastrous project to build a five-mile rail tunnel. Work was progressing at a snail’s pace when, because of problems with ground-water levels, workers plastered huge quantities of a cheap sealant over the interior of the tunnel.
That is where the real problems started. The sealant, Rhoca-Gil, contained acrylamide. Water seeped out from the tunnel into the ground- water. Dozens of local water-wells were found to be contaminated and the public was advised not to drink from them. High levels of acrylamide were found in salmon in local rivers and in cows grazing nearby which had shown mysterious symptoms of paralysis.
Of the tunnel workers, 20 out of an initial 77 examined had begun to experience numbness in their hands and the feeling of pin-pricks on their fingers. Other symptoms included numbing of the legs and arms, headaches, dizziness, eye and lung irritation. Among the 45 workers with the highest exposure, 30% showed symptoms of damage to the nervous system.
Professor Margareta Tornqvist, of Stockholm University’s environmental chemistry department, investigated how much acrylamide the workers had been exposed to. Her findings were surprising and were to lead ultimately to last week’s emergency conference. Tornqvist measured the levels of acrylamide in the workers’ blood and compared them to the levels in an outside control group. Her findings were puzzling: the control group also had high levels of the chemical in their blood.
“So then we started trying to find the sources of this,” said Tornqvist last week, “We thought it might be something to do with the diet.”
Her team tested individual foods for the presence of acrylamide. Soon a pattern began to emerge: fried and baked carbohydrates showed the highest levels.
Initially her findings were treated with scepticism by the global scientific community. Public health bodies in Britain, Germany, Switzerland and Norway ordered studies to investigate the claims. Their results replicated the Swedish findings.
European rules limit the acrylamide left on food from packaging to 10 parts per billion (ppb). But in Britain the FSA found 12,800 ppb in overcooked chips, up to 1,280 in varieties of crisps and up to 4,000 in types of crispbread. Acrylamide was also found in breakfast cereals.
There was no escaping the fact that a huge range of everyday foods contained potentially dangerous levels of a cancer-causing toxin.
After many more experiments, learned papers, conferences and announcements - all of which will take many years - we may come to some understanding of why acrylamide occurs in cooked food and how we might prevent it from doing so. We may even find a way to diminish the spiralling rates of cancer in western society.
Between 1950 and 1999, the proportion of deaths because of cancer increased from 15% to 27% for men in England and Wales, and from 16% to 23% for women. One in three people now develops a cancer in his or her lifetime, and one in four people will die from it. Between 1971 and 1997, the number of new cancer cases recorded each year increased from 149,000 to 221,000.
In part, this is because exposure to carcinogens such as tobacco and asbestos has increased. Conversely, improved treatment of other infectious diseases has led to greater longevity and the older you are the more likely you are to die from cancer than from other illnesses.
Yet the the acrylamide story fits into a wider emerging picture of the key role that diet plays both in causing and in preventing cancer, as research in the field has grown.
The importance of a balanced diet with plenty of fresh fruit and vegetables has long been known. But where the science is changing is in establishing specific links between particular foods and the levels of cancer-causing agents that they may contain. In Central America, for example, surging rates of stomach cancer were traced to milk from cows eating toxic brackens. In some areas of France, high levels of gut cancer in regions known for veined cheeses were traced to chemicals known as aflatoxins, a by-product of the fungi that produce the cheeses’ special taste.
Aflatoxins - one of the deadliest cancer-causing agents known - also attack nuts, dried fruits, cereals and spices, prompting regulators such as the FSA to put out regular alerts about high levels in imports.
Another group of carcinogens, known as aromatic hydrocarbons, are formed - like acrylamide - by overcooking or browning food, especially meat.
Although such chemicals may cause some cancers, none is sufficiently widespread to explain the rise in cancers throughout the developed world, even though studies show that the increase must have a dietary factor. Acrylamide, however, is different. It occurs in so many fried and baked foods and at such high concentrations that anyone eating a seemingly healthy western diet is exposed to it.
Tim Lang, professor of food policy at Thames Valley University, who helped influence the government into setting up the FSA, believes acrylamide and chemicals like it could show why cancer is so common in developed countries.
“Britons have a much better diet than they did in the past and much better than many countries do now - but we and other western peoples increasingly tend to die prematurely from diet-related disease such as cancer,” he said.
“This is a conundrum that has baffled scientists but the discovery of acrylamide could be the explanation we need. It means that these deaths could be caused by modern food processing and cooking techniques.”
If that is the case, then the eating habits of tomorrow could well make today’s health fads seem tame.
Additonal reporting:
Fiona Fleck in Geneva and Steve Strid in Stockholm
