The carcinogenicity of dietary acrylamide intake: a comparative discussion of epidemiological and experimental animal research

Our plain-English summary of The carcinogenicity of dietary acrylamide intake: a comparative discussion of epidemiological and experimental animal research, by J.G. Hogervorst, B.J. Baars, L.J. Schouten, et al (Critical Reviews in Toxicology, 2010).

The study

• Authors: J.G. Hogervorst, B.J. Baars, L.J. Schouten, E.J. Konings, R.A. Goldbohm, P.A. van den Brandt
• Journal: Critical Reviews in Toxicology
• Published: 2010;40(6):485-512
• Type of article: Review
• Cited by: 106 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Since 2002, it is known that the probable human carcinogen acrylamide is present in commonly consumed carbohydrate-rich foods, such as French fries and potato chips. In this review, the authors discuss the body of evidence on acrylamide carcinogenicity from both epidemiological and rodent studies, including variability, strengths and weaknesses, how both types of evidence relate, and possible reasons for discrepancies. In both rats and humans, increased incidences of various cancer types were observed. In rats, increased incidences of mammary gland, thyroid tumors and scrotal mesothelioma were observed in both studies that were performed. In humans, increased risks of ovarian and endometrial cancers, renal cell cancer, estrogen (and progesterone) receptor-positive breast cancer, and oral cavity cancer (the latter in non-smoking women) were observed. Some cancer types were found in both rats and humans, e.g., endometrial cancer (observed in one of the two rat studies), but there are also some inconsistencies. Interestingly, in humans, some indications for inverse associations were observed for lung and bladder cancers in women, and prostate and oro- and hypopharynx cancers in men. These latter observations indicate that genotoxicity may not be the only mechanism by which acrylamide causes cancer. The estimated risks based on the epidemiological studies for the sites for which a positive association was observed were considerably higher than those based on extrapolations from the rat studies. The observed pattern of increased risks in the rat and epidemiological studies and the decreased risks in the epidemiological studies suggests that acrylamide might influence hormonal systems, for which rodents may not be good models.

In plain English

This article was a review, not an original study, and its subject was acrylamide in food, not asbestos. The authors compared two long-term studies in Fischer 344 rats, three mouse studies, and published human studies of dietary acrylamide and cancer. Studies of workers exposed to acrylamide on the job were left out. Both rat studies found more thyroid tumors, more mammary gland tumors in females, and more mesothelioma of the scrotal lining (around the testis) in males. The authors noted that these mesotheliomas were considered secondary to Leydig cell tumors, which are common in this rat strain. In humans, the Netherlands Cohort Study reported higher risks of endometrial cancer in never-smoking women, of ovarian cancer and of renal cell cancer at the highest versus lowest intake, and a lower risk of lung cancer in women. No study found a higher risk of breast cancer overall. The authors concluded that dietary acrylamide may raise the risk of postmenopausal endometrial and ovarian cancers. They suggested a hormonal mechanism and stressed that the findings need confirmation in other studies.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review comparing rodent carcinogenicity studies and epidemiological studies of dietary acrylamide and cancer
• Who was studied: Published studies: two chronic carcinogenicity studies in Fischer 344 rats, three mouse studies, and case-control and prospective cohort studies of dietary acrylamide intake and human cancer (found through PubMed)
• Exposure: Acrylamide: given in drinking water or by other routes in the animal studies, and taken in through the diet in the human studies. Occupational acrylamide exposure studies were excluded. No asbestos exposure was studied.
• Main results:
  • In male rats, mesothelioma of the scrotal lining (listed as peritestis mesothelioma) was increased in both rat studies. Johnson et al. (1986): 11/60 at 0.5 and 10/60 at 2.0 mg/kg body weight per day, versus 3/60 in controls. Friedman et al. (1995): 13/75 at 2.0 mg/kg, versus 4/102 in each of the two control groups.
  • The authors reported that these tunica vaginalis mesotheliomas in male rats were considered secondary to Leydig cell tumors, which are highly prevalent in F344 rats, and that it had been suggested this mode of action is not relevant to humans.
  • None of the human studies found an increased risk of total pre- or postmenopausal breast cancer with acrylamide intake.
  • Endometrial cancer, Netherlands Cohort Study: in never-smoking women, the risk ratio for the highest versus lowest quintile of intake was 1.99 (95% CI 1.12 to 3.52), p-trend 0.03.
  • Ovarian cancer, Netherlands Cohort Study: the risk ratio for the highest versus lowest quintile was 1.78 (95% CI 1.10 to 2.88) in all women and 2.22 (95% CI 1.20 to 4.08) in never-smokers. An Italian-Swiss case-control study and the Swedish Mammography Cohort found no association.
  • Renal cell cancer, Netherlands Cohort Study (the only prospective cohort study of this cancer): the risk ratio for the highest versus lowest quintile was 1.59 (95% CI 1.09 to 2.30), p-trend 0.04.
  • Lung cancer in women, Netherlands Cohort Study: an inverse association, with a risk ratio for the highest versus lowest quintile of 0.45 (95% CI 0.27 to 0.76), p-trend 0.01. There was no association in men.
  • The risks observed in human studies for endometrial, ovarian and renal cell cancers were at least 10-fold to 100-fold higher than predicted from the rat studies.
• The authors' conclusion: The authors concluded that acrylamide at current dietary exposure levels may raise the risk of postmenopausal endometrial and ovarian cancers. They hypothesized that acrylamide may alter hormonal balances, raising some cancer risks and lowering others.
• Limitations the authors state:
  • The observed associations need to be investigated in other studies to tell true associations from chance findings.
  • The human studies were too heterogeneous to pool, so no pooled results per cancer site were calculated.
  • Some subgroup findings rested on few cases (for example, 14 cases in the obesity analyses) and have to be interpreted cautiously.
  • The tumor sites seen in rats may have little relevance to humans.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Genotoxicity.

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