A recent study supports growing evidence that eating too much meat may be unhealthy. Researchers from the U.S. National Cancer Institute found that a diet rich in red and processed meats increased the risk of death, particularly from cancer and heart disease.
In the study, published in the Archives of Internal Medicine, researchers analyzed data from more than half a million people (aged 50-71) who were enrolled in the National Institutes of Health-AARP Diet and Health Study. Meat intake was estimated through a food questionnaire.
People in the high-intake group for red meat ate an average of 4.5 ounces daily, while those in the lowest-intake group ate a little more than half an ounce daily. For processed meat, people in the high-intake group ate an average of 1.5 ounces daily compared to 0.11 ounces in the low-intake group.
During the 10-year follow-up period, the researchers recorded the number of deaths and their causes. They adjusted for other risk factors, such as age, smoking, obesity and alcohol consumption.
By the end of the study, 47,976 men and 23,276 women died from various causes. In those who ate the most red meat, the overall risk of death increased by 31 percent in men and 36 percent in women, compared to those who ate the least. The risk of fatal cancer increased by 22 percent in men and 20 percent in women, and the risk of fatal heart disease increased by 27 percent in men and 50 percent in women.
In those who ate the most processed meat, the overall risk of death increased by 16 percent in men and 25 percent in women, compared to those who ate the least. The risk of fatal cancer increased by 12 percent in men and 11 percent in women, while the risk of fatal heart disease increased by nine percent in men and 38 percent in women.
In contrast, people who ate higher proportions of white meat, such as turkey, chicken or fish, were less likely to die during the study period than those who ate the lowest proportions.
These results are somewhat limited by the study design because the data relied on the participants' memories of what they ate.
It has been suggested that cancer risk may be increased by compounds called heterocyclic amines (HCAs), which are formed when red meat is cooked at high temperatures. HCAs have been linked to various cancers, including stomach, colorectal, pancreatic and breast cancers in humans.
Red meat also contains high amounts of saturated fats, which have been shown to increase the risk of heart disease.
In a related study, published in the American Journal of Epidemiology, diets rich in red meat were linked to age-related macular degeneration (AMD), the leading cause of blindness in aging Americans. In the study, 6,734 people (aged 58-69) completed food frequency questionnaires in 1990-1994. During the follow-up period (2003-2006), the participants were monitored for the development of AMD.
The researchers found that people who ate red meat 10 or more times per week were 47 percent more likely to develop AMD than those who ate it less then 4.5 times per week. The authors suggest that these effects may be attributed to compounds in the meat that cause oxidative damage.
Additional research is needed to determine exactly how red meat might increase the risk of AMD.
Chong EW, Simpson JA, Robman LD, et al. Red meat and chicken consumption and its association with age-related macular degeneration. Am J Epidemiol. 2009 Apr 1;169(7):867-76. Epub 2009 Feb 20.
Sinha R, Cross AJ, Graubard BI, et al. Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med. 2009 Mar 23;169(6):562-71.
This article appeared in the April 2009 issue of the Integrative Medicine Newsletter published by Natural Standard.