Many studies have shown that eating too much red meat is bad for your health; but, a new study has found that eating processed meat significantly increases the risk of colorectal cancer in some people.
Eating five or more servings per week of processed meat more than doubles the risk of colorectal cancer in people who have certain variants of a specific gene, according to Jane Figueiredo of the University of Southern California's Keck School of Medicine. Colorectal cancer is a leading form of cancer disease and death worldwide.
The findings are based on a meta-analysis of 10 earlier studies involving 18,000 people in the United States, Canada, Australia and Europe, which looked at the health effects of eating meats that contain nitrates as preservatives.
"It's anything that is cured, dried, smoked, cooked [or] packaged. And so the most common items around the countries we were studying would include bacon, ham, hot dogs, sausages, pate, cold cuts," said Figueiredo.
The scientists compared the blood samples of some 9,000 people with colorectal cancer to 9,000 people without the disease, looking at one particular region of the genome. Colorectal cancer is a complex illness with some 30 genetic variations tied to an increased risk of developing it.
The researchers found the people with two of the genetic variants that were the focus of the study, and who ate processed meats almost every day, had the highest risk for colorectal cancer.
Figueiredo says the potentially harmful alleles - or changes in a specific gene - are extremely common.
“It happens in one in three individuals; that these individuals are actually at even at higher risk of the carcinogenic effects in processed meat," she said.
Does that mean that people with two copies of the genetic variants can eat more bacon and ham than those at the highest cancer risk?
“People have asked me that and I think that we should also limit our consumption of processed meat. It still more modestly increases risk at least in individuals that don’t have this variant allele. But it still is a small effect. It's just a much larger effect in individuals that carry certain genetic changes," said Figueiredo.
Her team systematically sifted through millions of genetic variants of the study participants, identifying those that are associated with the effects of meat, fiber, fruit and vegetable consumption. Figueiredo says the investigation is the first to look at whether genes modify the impact of food on health.
The study by Jane Figueiredo and colleagues is published in the journal PLoS Genetics.