How Bad Is Bacon for You, Really?

It's a debate that plays out in everyone's head during a weekend brunch: Should I be eating this much bacon? Researchers have been diving into the question, too, specifically as it relates to cancer.

The question once again jumped to the forefront of people's minds with the recent release of a meta-analysis that concluded that bacon and several other types of meat are tied to an increased risk of breast cancer.

The research, published in September in the International Journal of Cancer Research, looked at 15 previous studies, including a total of more than1.2 million women, focused on the link between breast cancer and processed meat. The researchers found that individuals who consumed the most processed meat — between 0.9 ounces and 1 ounce (25 and 30 grams) a day — had about a 9 percent higher risk of breast cancer compared with those who ate the least processed meat, which was 0 to 0.07 ounces or 0.17 ounces (2 to 5 grams) a day. [11 Ways Processed Food Is Different from Real Food]

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Not every paper looking into this relationship has come to the same conclusion, however: A World Health Organization-affiliated study from 2015, for example, did not, though it did decide these foods increased the risk of colorectal cancer. If there are inconsistencies, what, then, should bacon lovers take away from the piles of papers that are published?

Dr. Marji McCullough, a senior scientific director of epidemiology research at the American Cancer Society, noted that breast cancer is a common disease in women, and that salamis, hot dogs and other processed meats are popular food choices. Together, those factors mean the risk the food poses, even if small, is worth paying attention to, especially since an earlier meta-analysis on the topic that has reached similar conclusions.

Limitations to keep in mind

Still, it's important to know that there are limitations to the type of research that aims to link certain foods to the risk of health conditions. In this case, the research available to study meant that the authors could only assess the impact of high- and low-processed meat consumption — there wasn't enough data available to see what risks consumers run when they eat 0.35 ounces to 0.5 ounces (10 or 15 grams) of the product. What's more, the studies included in the meta-analysis relied on participants remembering what their diet had been like at certain points in the past. This research technique that depends on memories has a lot of room for under- and overestimation, said Andrew Milkowski, a meat science researcher and an adjunct professor of animal sciences at the University of Wisconsin-Madison who was not involved with the new report. (Before joining the University of Wisconsin in 2006, Milkowski worked for Oscar Mayer.)

But Maryam Farvid, the lead author on the latest project and a researcher at the Harvard T. H. Chan School of Public Health, said her team tried to counteract this last problem by relying only on studies that surveyed women before they received any diagnosis. That method, Farvid told Live Science, means women were less likely to confuse their pre- and post-cancer diets. [Top 10 Cancer-Fighting Foods]

Ideally, researchers could administer controlled diets to participants before they're diagnosed with anything, and closely watch for changes in their health — though those conditions are extremely difficult to pull off, Milkowski told Live Science. "If I were smart enough to figure that out, I'd be promoting that type of research — I don't know if it's a solvable problem," he added.

Milkowski also said that the 9 percent increase in risk that this report found could be a statistical error, and is not enough to warrant alarming people — a point that others have made when criticizing the 2015 WHO-associated report, which labeled processed meats as "likely carcinogens" after finding the food increased colon cancer risk by 18 percent.

But Farvid said that other dietary factors have also been associated with breast cancer risk, such amount of fiber or fruits and vegetables in a person's diet, and may decrease or increase risk of the disease by similar margins, yet there's much less alarm around these findings.

Small but meaningful

Indeed, the small advantages to eating less processed meat could be especially meaningful, seeing as some other breast cancer risk factors are unchangeable, such as whether women have the breast cancer gene or how young they were when they started menstruation, Farvid said. "You may say it's hard to change your diet," she said, "but that at least is modifiable."

Both Farvid and McCullough advise paying attention to how much processed meat you consume, which, as McCullough said, is part of the American Cancer Society’s current dietary recommendations for minimizing the risk of cancer.

"Rich in plants and low in red and processed meats is a recommendation similar to other healthy diet patterns," McCullough told Live Science. As time goes on, researchers will be better equipped to investigate risk factors for subtypes of cancers, she adds, which could provide more details about what snacks, exactly, play a role in our health. 

Originally published on Live Science.