Recent research results from Sweden and huge EPIC study reinforce cancer risks from processed and red meats: findings affirm the superior safety profile of seafood and poultry productsby Craig Weatherby
For those who like meat, sausage, salami, hot dogs, and other processed meat products made from beef and pork hold a strong allure. But satisfaction of these cravings seems to exact a high price. Evidence that processed meats raise the risks of getting cancers of the stomach, colon, pancreas and blood continues to accumulate.
The newest revelations concerns stomach cancer, which accounts for nearly one in ten cancer deaths. And when a review of the epidemiological evidence concerning processed meats and the risk of stomach cancer landed in our e-mail inbox we were surprised to learn that it was the first such analysis ever conducted.
Processed meats have long been the butt of comedians' jokes, thanks to their presumed cancer-promoting properties. But while the connections between processed meats and colorectal cancer are quite clear, the assumed link between processed meats and stomach cancer had never been subjected to a rigorous evidence review.
This blank spot on the medical map led researchers at Sweden's famed Karolinska Institute to review the best-designed studies, in the hope that they could arrive at a firm conclusion concerning the risk of stomach cancer and high intake of processed meats.
Risky byproduct of sausage inspired law-making
In addition to being made from the cheapest, least desirable parts of the sources of “red” meats (beef, pork, veal, and lamb), the processed products made from them—like sausage, hot dogs, ham, bacon, and cold cuts—present two kinds of risk factors:
- Processed meats are often salted or smoked
- Processed meats usually contain nitrite preservatives that convert to cancer-promoting compounds called nitrosamines
We've all heard the old adage that you don't want to watch sausage-making or law-making. But in this case, fear of the consequences of the former inspired some of the latter.
In the late 1960's it was discovered that vitamin C inhibits the formation of nitrosamines, and in the early 1970's, the US government responded to growing evidence of the dangers of nitrites in processed meat by requiring manufacturers to add tiny amounts of vitamin C (ascorbic acid) to their products (Most use an isomer of ascorbic acid called erythorbic acid).
However, in the past two decades, American's consumption of nitrites fell ten-fold as manufacturers responded to pressure to reduce levels in meat. And the great majority of American's “body load” of nitrites stems from consumption of vegetables, which contain nitrates that break down into nitrites in the gut.
Nitrites remain likely suspects in the alleged cancer-promoting effects of processed meats, along with salt and certain byproducts of smoking (polycyclic hydrocarbons and heterocyclic amines).
And together with findings from a 2003 study at the National Cancer Institute (Michaud DS 2003), the results of the Multiethnic Cohort Study—a large epidemiological trial from Hawaii (Nothlings U 2005)—suggest that nitrosamines remain the likeliest candidate as the primary cancer-risk factor in processed meats.
The authors of the investigated associations between intake of meat, other animal products, fat, or cholesterol and rates of pancreatic cancer among 190,545 participants over a seven year period, during which they administering dietary surveys.
The participants who reported the highest intake levels of processed meats had a 68 percent higher risk compared with those reporting the lowest intake, while high intakes of red meat were associated with a 50 percent higher cancer risk, compared with the lowest intake levels.
The results of the Hawaiian Multiethnic Cohort Study revealed no link between pancreatic cancer risk and intake of poultry, fish, dairy products, eggs, total fat, saturated fat, or cholesterol.
While the authors noted that carcinogenic substances related to smoking and other preparation methods, rather than nitrosamines, might be responsible for the link between processed meat and increased risk of pancreatic cancer, they ruled out fat and saturated fat as major risk factors.
As they said, “Red and processed meat intakes were associated with an increased risk of pancreatic cancer. Fat and
saturated fat are not likely to contribute to the underlying carcinogenic mechanism [i.e., cancer risk] because the findings for fat from meat and dairy products [both of which contain high levels of fat and saturated fat] differed.”
While the role of nitrosamines in raising cancer risk remains unquantifiable, the results of the new evidence review—and those of the enormous EPIC study—indicate that there is something decidedly dangerous about eating too much processed meat.
Further, the EPIC study results suggest that heavy fish-eaters may enjoy a low risk of stomach cancer, if only by crowding processed meats out of their diets.
Swedes' analysis supports suspicions of processed meats
The Karolinska Institute in Stockholm is Sweden's largest center for medical training and research and one of Europe's largest medical universities. Scientists there analyzed the results of six prospective cohort studies involving 2,209 stomach cancer patients, and nine case–control studies involving 2,495 patients published since 1965 (Larsson SC 2006).
Their analysis of the cohort studies showed that the relative risks of stomach cancer rose 15 percent for every increase in processed meat consumption of 30 grams (just over one ounce), while the risk rose 38 percent among people in the case–control studies.
Three cohort and four case–control studies examined the association between bacon consumption and stomach cancer, and the researcher's analysis indicates that, compared with the participants with the lowest bacon intake, the relative risk of stomach cancer was 37 percent higher among the participants with the highest intake.
The authors characterized the results as “unequivocal” and co-author Susan Larsson made these comments to the media, “…our results… show very clearly that there is an association between increased consumption of processed meat products and stomach cancer. We hope that further studies will clarify the interaction between the consumption of processed meats and other factors, such as other dietary factors and the effects of different bacteria on the incidence of stomach cancer,” Larsson said.
EPIC study finds fish reduces cancer risk
A year before the Swedish review was published researchers at the International Agency for Research on Cancer in Lyon, France released the results of a another substantial study: findings that serve to support the dangers of processed meat and highlight the protective power of fish (Norat T 2005).
This prospective cohort study was part of the huge European Prospective Investigation into cancer and nutrition, or EPIC, and it involved 478,040 men and women from 10 European countries.
The impetus behind this arm of the EPIC study was a lack of good information on fish and the risk of colorectal cancers. As the EPIC team said, “…high red meat intake is associated with increased colorectal cancer risk. High fish intake may be associated with a decreased risk, but the existing evidence is less convincing.”
To clarify the situation, the researchers collected information on participants' diets and lifestyles at the outset, and again after an average of 4.8 years. During the study period, 1,329 subjects were diagnosed with colorectal cancer, and at the end the EPIC team analyzed the data to detect any relationships between intakes of red and processed meat, poultry, and fish with rates of colorectal cancer.
Poultry intake had no apparent impact on the risk either way, but, unsurprisingly, the highest risk occurred in participants who ate more than 5.7 ounces (160 grams) of red and processed meat per day.
Fish, however, fell on the opposite end of the scale. The EPIC results indicated that risk of cancer drops with increasing seafood intake, since the lowest risk of colorectal cancer appeared among those who averaged more than 2.8 ounces (80 grams) every day.
“Our data confirm that colorectal cancer risk is positively associated with high consumption of red and processed meat and support an inverse association with fish intake.”
Salmon or poultry products offer safer choices
Many of us savor the characteristic flavor of sausage, but the results of these studies certainly suggest that it's unsafe to indulge in sausage, bacon, cold cuts, ham, hot dogs, and other highly processed products made from red meats (beef, pork, veal, and lamb).
These findings indicate, quite clearly, that it is safer to curb your cravings for sausage, hot dogs, and the like by enjoying nitrite-free alternatives made with poultry or fish. And they confirm that fish presents the lowest cancer risk possible among sources of animal protein.
It also makes sense to avoid deep-fried meat, fish or poultry products entirely, because their oil-soaked batters deliver loads of pro-inflammatory (hence cancer- and heart disease-promoting) omega-6 fatty acids and heat-damaged fatty acids.
Most Americans consume omega-6 fatty acids in enormously excessive amounts, thanks to their dominance in the oils used most commonly in home cooking and in packaged, prepared, and restaurant foods (i.e., vegetable oils from soy, corn, canola, safflower, sunflower, and cottonseed).
- Larsson SC, Orsini N, Wolk A. Processed meat consumption and stomach cancer risk: a meta-analysis. J Natl Cancer Inst. 2006 Aug 2;98(15):1078-87.
- Norat T, Bingham S, Ferrari P, et al. Meat, fish, and colorectal cancer risk: the European Prospective Investigation into cancer and nutrition. J Natl Cancer Inst. 2005 Jun 15;97(12):906-16.
- Michaud DS, Giovannucci E, Willett WC, Colditz GA, Fuchs CS. Dietary meat, dairy products, fat, and cholesterol and pancreatic cancer risk in a prospective study. Am J Epidemiol. 2003 Jun 15;157(12):1115-25.
- Nothlings U, Wilkens LR, Murphy SP, Hankin JH, Henderson BE, Kolonel LN. Meat and fat intake as risk factors for pancreatic cancer: the multiethnic cohort study. J Natl Cancer Inst. 2005 Oct 5;97(19):1458-65. Erratum in: J Natl Cancer Inst. 2006 Jun 7;98(11):796.
- Collins K. How Risky Is Red Meat? Accessed online August 12, 2006 at http://health.msn.com/centers/coloncancer/articlepage.aspx?cp-documentid=100108484
- Jakszyn P, Gonzalez CA. Nitrosamine and related food intake and gastric and oesophageal cancer risk: A systematic review of the epidemiological evidence. World J Gastroenterol. 2006 Jul 21;12(27):4296-4303.
- Strumylaite L, Zickute J, Dudzevicius J, Dregval L. Salt-preserved foods and risk of gastric cancer. Medicina (Kaunas). 2006;42(2):164-70.
- Marques-Vidal P, Ravasco P, Ermelinda Camilo M. Foodstuffs and colorectal cancer risk: a review. Clin Nutr. 2006 Feb;25(1):14-36. Epub 2005 Nov 14.
- Sandhu MS, White IR, McPherson K. Systematic review of the prospective cohort studies on meat consumption and colorectal cancer risk: a meta-analytical approach. Cancer Epidemiol Biomarkers Prev. 2001 May;10(5):439-46.
- Larsson SC, Bergkvist L, Wolk A. Processed meat consumption, dietary nitrosamines and stomach cancer risk in a cohort of Swedish women. Int J Cancer. 2006 Aug 15;119(4):915-9.
- Norat T, Lukanova A, Ferrari P, Riboli E. Meat consumption and colorectal cancer risk: dose-response meta-analysis of epidemiological studies. Int J Cancer. 2002 Mar 10;98(2):241-56.
- English DR, MacInnis RJ, Hodge AM, Hopper JL, Haydon AM, Giles GG. Red meat, chicken, and fish consumption and risk of colorectal cancer. Cancer Epidemiol Biomarkers Prev. 2004 Sep;13(9):1509-14.
- Gonzalez CA, Jakszyn P, Pera G, et al. Meat intake and risk of stomach and esophageal adenocarcinoma within the European Prospective Investigation Into Cancer and Nutrition (EPIC). J Natl Cancer Inst. 2006 Mar 1;98(5):345-54.
- van den Brandt PA, Botterweck AA, Goldbohm RA. Salt intake, cured meat consumption, refrigerator use and stomach cancer incidence: a prospective cohort study (Netherlands). Cancer Causes Control. 2003 Jun;14(5):427-38.
- Archer DL. Evidence that ingested nitrate and nitrite are beneficial to health. J Food Prot. 2002 May;65(5):872-5.