ROCKVILLE, MD. — While bread is a source of potentially carcinogenic compounds, bread intake is not associated with increased cancer risk, according to a study published in the December issue of Current Developments in Nutrition. Whole wheat bread intake is associated with lower cancer risk.

The study, “Bread Consumption and Cancer Risk: Systematic Review and Meta-Analysis of Prospective Cohort Studies” was written by a team led by Glenn Gaesser, a professor at Arizona State University. Other contributors include Siddartha S. Angadi of the University of Virginia, Craig Paterson of Bristol Medical School and Julie Miller Jones of St. Catherine University. Gaesser chairs the scientific advisory committee of the Grain Foods Foundation.

Explaining the basis for the study, the researchers highlighted bread’s role as a staple food that provides numerous nutrients while also noting it is a source of potentially harmful compounds formed during baking, including acrylamide. The compound forms as part of Maillard browning, “which is crucial for color and flavor in bread,” they explained.

“Bread could also conceivably increase cancer risk via glycemic index (GI),” the researchers said. “Many breads have a moderate to high GI. Several meta-analyses have demonstrated that a high dietary GI is associated with increased cancer risk.”

They also cited studies suggesting ultra-processed foods, including bread, are associated with higher cancer risk and that acrylamide content is a reason bread ought to be avoided.

After studies showing acrylamide causes cancers, the International Agency for Research on Cancer in 1994 listed acrylamide as “probably carcinogenic to humans.” Similarly, the US National Toxicology Program classified acrylamide as “reasonably anticipated to be a human carcinogen.”

In the years since then, “results from epidemiologic studies assessing the association between dietary acrylamide exposure and cancer risk have been inconclusive,” the researchers said.   Still, health institutions continue to believe acrylamide is a “concern to human health,” they added.

As a result, the researchers conducted what they believe was the first systematic review or meta-analysis examining the “association between bread intake and site-specific cancer risk.”

For the data review Gaesser and Angadi reviewed peer-reviewed prospective cohort studies that provided measures of cancer risk and looked at bread as a distinct food. The researchers settled on 24 studies, of which 21 were from Europe, 2 were from the United States and 1 from Japan. A total of 1,887,074 adults were included across the 24 studies.

None of the studies indicated a higher rate of all cancer mortality associated with intake of bread, the researchers said. One study showed a significantly lower risk. For colorectal cancer, 32 studies showed no connection between bread intake and cancer incidence, while 8 indicated lower incidence was associated with higher bread consumption and 8 indicated higher incidence associated with higher bread consumption.

For breast cancer, five studies generated 19 different outcomes, 16 of which were not statistically significant. In the case of prostate cancer, 14 of 15 outcomes showed no significant association between bread intake and prostate cancer incidence or mortality.

“The results of this systematic review and meta-analysis show that bread consumption is not associated with increased cancer incidence or mortality,” the authors said. “Nearly 90% (97 of 108) of the outcomes from the 24 cohort studies indicated either no association between bread consumption and cancer incidence or mortality, or a reduced incidence or mortality rate associated with higher bread intake. To our knowledge, our site-specific cancer meta-analysis is the first to show that bread consumption is not associated with risk for colorectal, breast or prostate cancer. The 10% lower cancer mortality rate among those in the highest bread intake group for whole grain or nonwhite bread (using all results from the supplemental analysis) is consistent with findings from previous meta-analyses that reported that whole grain bread consumption was associated with an ~10% to 15% lower risk of cancer mortality.”

In the discussion of their findings, the researchers noted that numerous studies have found over the years that intake of whole grains was associated with reduced cancer risk, especially colorectal cancer. The benefit generally has been attributed to the fiber and antioxidant content of whole grains.

“Interestingly, acrylamide concentrations in whole grain bread and related foods are generally higher than white bread,” the researchers said.

While the systematic review demonstrated numerous strengths in the studies included, “limitations of nutritional epidemiology must be acknowledged, especially for cancer,” the authors said. Because most of the studies were from European countries, the findings may not be representative of bread consumption elsewhere, they added.