TCS Daily

I Smell a Rat

By John Luik - October 3, 2005 12:00 AM

Editor's note: This article is the third in a series on the alleged link between acrylamide intake and cancer in humans.

According to the Center for Science in the Public Interest (or as some toxicologists refer to it, the Center for Sorcery in the Public Interest, given its record of bad science), "dietary acrylamide causes an estimated 8,900 cancers" and "thousands of deaths" annually in the United States. The crucial question is: just who are these people and where do they live?

The answers to questions about the cancer risks posed to human populations, as opposed to rats and fruit flies, is to be found in the epidemiological studies that have looked at acrylamide. One of the more curious things about the crusade against acrylamide by CSPI, the World Health Organization (WHO) and California Attorney General Bill Lockyer, is that none of them wants to talk about what the scientific evidence of acrylamide in humans -- as opposed to rats -- actually says.

For example, in CSPI's petition to the FDA aimed at forcing food manufacturers to limit the amount of acrylamide in their products (a position since changed to forcing them to warn consumers that the products may be cancerous), it relied on lab studies about acrylamide in rats, except for one reference to an epidemiological study, which it said "provided the first evidence that acrylamide might cause cancer in humans."(p.6) That study by Marsh et al, published in Occupational and Environmental Medicine in 1999, however, did not, whatever CSPI's claim, find a statistically significant association between occupational exposure to acrylamide and cancer.

Speaking of their study, Marsh notes that it is "the most definitive study of the human carcinogenic potential of exposure to acrylamide conducted to date." As he notes in conclusion:

        "The contribution of 1115 additional deaths and nearly 60,000 person years 
        over the 11 year follow up period corroborate the original cohort study 
        findings of little evidence for a causal relation between exposure to acrylamide 
        and mortality from any cancer sites..."

As even WHO admitted in its report on acrylamide in March of this year in referencing the Marsh findings:

        "Epidemiological studies have been carried out on workers occupationally 
        exposed to acrylamide. Acrylamide exposure was not associated with overall 
        cancer mortality..."

The reason for this reticence to speak about the epidemiological evidence is that the science, without exception, suggests that acrylamide does not cause thousands of deaths per year from cancer. Indeed, based on the existing science it would be difficult to conclude that dietary acrylamide results in even one US death a year.

Probably the world's leading acrylamide epidemiologist is Lorelei Mucci of Harvard and Sweden's Karolinska Institute. Since the first reports of acrylamide in food, Mucci has done four studies of its effects in human populations, with the most recent published in July.

In her first study, published in 2003, Mucci and a research team looked at dietary acrylamide and cancer of the large bowel, kidney and bladder in a Swedish population. She concluded that "dietary exposure to acrylamide in amounts typically ingested by Swedish adults in certain foods has no measurable impact on risk of three major types of cancer." Even more interesting, however, was the fact that a "reverse trend was found for large bowel cancer", which means that acrylamide appeared to be protective against this form of cancer.

Similar results were found in a 2004 study by Mucci and others which looked for an association between acrylamide and the risk of renal cell cancer. As Mucci noted: "The results of this study... suggest there is no association between dietary acrylamide and risk of renal cell cancer."

In March of this year, Mucci published a prospective study which looked at whether there was a link between acrylamide intake and breast cancer risk. Examining the acrylamide intake of 43,404 women in the Women's Lifestyle and Health Cohort, she found that average daily acrylamide intake of the subjects of 25.9 micrograms per day. Fewer than 1.5 percent of the women consumed more than 1 milligram of acrylamide per kilogram of body weight per day, which is the level used in lab-based risk assessment models. Mucci found that the food contributing the highest amounts of acrylamide were coffee (54%), not fried foods, which are often painted as the villain in the acrylamide story.

More importantly, Mucci found that in comparing the women with the lowest daily acrylamide intake with those whose intake was higher, there was no increased risk of breast cancer. Nor did those subjects who ate the highest amounts of foods with acrylamide have an increased risk of breast cancer. As Mucci concluded "We found no evidence of an association between the amount of acrylamide consumed by these Swedish women and risk of breast cancer."

Finally, in July Mucci and her Swedish collaborators published a prospective study which looked at acrylamide and the risk of colorectal cancer. Using the Swedish Mammography Cohort of 61,467 women, Mucci found that the mean intake of acrylamide in the women's diet was 24.6 micrograms per day, with the majority intake again provided by coffee. They found that not only was "there no association between estimated acrylamide intake and colorectal cancer", but that the "intake of specific food items with elevated acrylamide (e.g. coffee, crisp bread and fried potato products) was not associated with cancer risk." The findings about "fried potato products" -- read French fries -- just might be something that California's Lockyer might want to consider given his proposed warning for fries that acrylamide is a "chemical known to the state of California to cause cancer."

What is especially curious in all of this is that as Mucci's studies were appearing, WHO acted as if they did not exist. WHO's Joint Expert Committee with the UN Food and Agriculture Organization met in Rome in February, 2005 and issued a report saying that "acrylamide levels in food should be reduced because of public health concerns" -- the same line pushed by CSPI. Only WHO's report came in 2005, three years after the initial acrylamide scare and after the publication of three studies had shown it to pose no cancer risk for humans. WHO could hardly be unaware of Mucci's first two studies, or indeed of the fact that her third study was due to be published just days after its meeting. So, just what might these health concerns be?

WHO's concerns were the same as they were in 2002, namely with those acrylamide-stuffed lab rats. In order for these rats to develop "mammary" tumors, they had to eat 300 micrograms of acrylamide per day, per kilogram of rat body weight. Translated into human terms and you come up with the 154 pound person needing to eat 300 pounds of breakfast cereal PER DAY for life to receive the same dose. As WHO reluctantly conceded, even those people eating the highest amounts of acrylamide per day would receive only 1.3% of the dose that produced breast cancer in rats.

WHO's contribution to bringing sound science to bear on the acrylamide scare consisted of ignoring the earlier epidemiological literature on acrylamide and human cancer and ignoring Mucci's study on acrylamide and breast cancer in humans and relying instead on rat studies which replicated in humans would require the impossible -- eating hundreds of pounds of acrylamide-laden food a day in order to reach the levels at which rats contract cancer.

Nor are Mucci's finding about no association between acrylamide and human cancer some epidemiological fluke. Italian Claudio Pelucchi of Milan in 2003 looked at a series of hospital-based case-control studies from Italy and Switzerland involving cancer of the oral cavity and pharynx, esophagus, larynx, large bowel, colon, rectum, breast and ovary and found no statistically significant association between acrylamide-rich food intake and cancer. As he noted

        "Our data provide reassuring evidence for the lack of an important association 
        between consumption of fried/baked potatoes and cancer risk."

Of course, CSPI may still argue that acrylamide causes cancer in humans, and Bill Lockyer might continue to push for his warning for acrylamide laden foods. But if they do they have an obligation to tell us what they know that the scientific community doesn't.

NEXT: The Acrylamide Saga and California.

John Luik is writing a book on health policy.


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