Men who regularly eat red meat have a higher risk of developing an inflammatory bowel condition called diverticulitis than men who don't have much red meat in their diet, a new study finds.
The men in the study who ate six or more servings of red meat weekly were 58 percent more likely to develop diverticulitis during the 26-year study than the men in the study who ate the least amount, which was 1.2 servings weekly on average.
Diverticulitis occurs when the wall of a person's gut bulges out from its usual position and forms a small sac — called a diverticulum — and this sac becomes inflamed, according to the study, published today (Jan. 9) in the journal Gut. Although such bulges can happen anywhere in the gut, they're most common in the large intestine. [11 Surprising Facts About the Digestive System]
Diverticulitis leads to about 210,000 hospitalizations each year in the United States, and the total cost of treating patients with the condition is more than $2 billion, the researchers wrote. (In severe cases of diverticulitis, people may need intravenous antibiotics or surgery, according to the Mayo Clinic.)
However, it's not entirely clear what causes the condition, and what puts someone at risk for developing it, the researchers wrote in the study. The research was led by Yin Cao, a research fellow in nutrition at the Harvard University T. H. Chan School of Public Health.
Some risk factors for diverticulitis include smoking, taking nonsteroidal anti-inflammatory drugs (or NSAIDs) and a lack of physical activity. However, little is known about what dietary factors, beyond not eating enough fiber, may play a role, according to the study.
In the study, the researchers analyzed data collected from more than 46,000 men enrolled in the ongoing Health Professionals Follow-Up Study. Every two years, the men in the study filled out questionnaires about their medical histories and any illnesses they had, and every four years, they completed a questionnaire to give researchers a sense of their diets. None of the men included in the study had problems related to diverticulitis, inflammatory bowel disease or a gastrointestinal cancer at the beginning of the study.
In the dietary questionnaires, the men were asked several questions about their meat intake, including how often they ate red meat, processed red meat, poultry and fish.
During the 26-year follow-up period, 764 men developed diverticulitis, the researchers found. Aside from finding the link between red meat and an increased risk of diverticulitis, the researchers also found that other types of animal protein were associated with a decreased risk of diverticulitis. For example, substituting one serving of red meat with a serving of fish or poultry was associated with a 20 percent lower risk of developing the condition during the study period, the researchers found.
The researchers noted that men who reported eating more red meat also smoked more, took NSAIDs more often and did less vigorous exercise than men who reported eating less red meat. However, the link between red meat and diverticulitis remained even after the researchers accounted for these other risk factors. [Kick the Habit: 10 Scientific Quit-Smoking Tips]
The study did not prove there is a cause-and-effect relationship between eating more red meat and developing diverticulitis. However, there are several hypotheses for why red meat may play a role in diverticulitis. For example, higher red meat intake is linked to higher levels of chronic inflammation, which may increase a person's risk for the condition, the researchers wrote. In addition, red meat intake may alter the gut microbiome in a way that increases a person's risk, they added.
Though processed red meat is often implicated in health problems (for example, bacon made headlines in 2015 when the World Health Organization linked the processed meat to cancer), unprocessed red meat was found to be the major driver of the link between red meat and diverticulitis, the researchers wrote in the study.
Compared with processed meat, unprocessed meat, such as steak, "is usually consumed in larger portions, which could lead to a larger undigested piece in the large [intestine] and induce different changes" in the gut microbiome, the researchers said. Another hypothesis for unprocessed red meat's role is that the higher cooking temperatures used to prepare the food may also influence gut bacteria or inflammation levels, they wrote. However, these factors need to be studied further, they added.
The study had limitations, including that the men reported their own red meat intake, according to the study. In addition, because the study included only men, it is unclear if the results also apply to women, the researchers wrote.
Originally published on Live Science.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.