Diet, Blood Sugar and Cancer Risk Among Various Species
Most people recognize the detrimental effects of uncontrolled blood sugar. Risk for heart disease, stroke, and kidney disease are a few chronic conditions that can develop over time. According to the CDC, nearly 16% of US adults are diagnosed with diabetes, while 4.5% are undiagnosed. 1
A new study by researchers at Arizona State University evaluated the link between diet, blood sugar, and cancer among various animal species. It turns out that birds have higher blood sugar levels, but live longer than their equally sized mammals and reptiles. They also have reduced rates of cancer. 2
Primary carnivores- animals that typically eat other vertebrates- are more likely to develop tumors than herbivores, especially when they are domesticated.
The results of the study were published in the journal Nature Communications. They question previous assumptions and propose that some species have developed natural biological defenses against cancer. Metabolic adaptations and protective cellular mechanisms could provide natural defense and encourage new cancer prevention and treatment approaches in humans.
Study co-author Carlo Maley said, “We knew that birds get less cancer than mammals, and they also have very high levels of glucose in their blood. That made us wonder if there was some connection”. Maley is a researcher with the Biodesign Center for Biocomputing, Security and Society, a professor with the School of Life Sciences, and director of the Arizona Cancer Evolution Center.
Birds break the mold
Data from up to 273 species of vertebrates were evaluated, including their diet, average blood sugar levels, and cancer prevalence. A major discovery was that even though their blood sugar was high, birds have lower rates of cancer than mammals and reptiles.
This wasn’t expected since in humans and other animals, high blood sugar levels are usually linked with increased cancer risk. The researchers discovered that the association between cancer risk and blood sugar wasn’t consistent among all vertebrates.
The trend was observed among major groups- birds, mammals, and reptiles. When evaluated separately, no clear link between cancer and blood sugar levels was seen within the groups. This may mean birds have developed unusual biological traits that protect them from cancer despite elevated blood sugar levels. These traits may not be seen in mammals and reptiles. Understanding these changes could provide valuable information for cancer prevention.
The impact of diet
The study also looked at whether diet impacts blood sugar and cancer prevalence. Despite past studies suggesting that carnivores have a higher cancer risk than herbivores, the research in nonhuman vertebrates evaluated diet groups in more detail, considering amounts of fruit, plants, invertebrates, and vertebrate meat in an animal’s diet.
Results showed no statistically significant connection between diet and blood sugar levels in nonhuman vertebrate species, which suggests that blood sugar regulation is likely impacted more by evolutionary and biological changes than by diet alone. Diet impacts blood sugar levels in humans and other species, but is not universal across other vertebrates.
One reason could be that different species have adapted traits to manage blood sugar, despite their diet. Birds maintain high blood sugar despite diverse diets, including nectar-rich versus meat-based. Likewise, some carnivorous mammals have stable blood sugar levels with protein-rich diets. Certain herbivores show variability that’s not related to a plant-based diet.
One of the researchers noted, "The lack of an overall connection between diet and blood sugar in the species examined in this study suggests that these animals are largely consuming foods designed for them, as their diet was not manipulated for the study. Even when our lab fed birds diets high in fat or sugar, which are known to increase blood sugar and cancer risk in humans, the birds show no changes in their blood sugar response. They are remarkably resilient animals."
Blood sugar may vary among species and may still influence the risk of cancer. The study discovered that primary carnivores had a higher tumor prevalence compared to herbivores. One reason is that damaging compounds build up in the food chain, making meat intake a possible risk for tumor development.
The researchers also found that domesticated species typically have a higher cancer prevalence because of reduced genetic diversity and softer evolutionary pressures. This leads them to believe natural selection could help reduce cancer development in wild populations. While the study focuses on patterns across species, it doesn’t prove that consuming domesticated animals increases the risk of cancer in humans.
Implications for humans
While this study was done in nonhumans, the findings could provide new information on cancer prevention in people. Humans and other mammals do not display the same evolved natural defenses against cancer as birds do.
The researchers suggest that birds may have developed defenses against cancer, such as a higher metabolism, reliance on fat metabolism versus glucose, and cellular changes that prevent oxidative damage. Comprehending these changes could provide more insights into how species develop natural cancer defenses.
Moving forward, humans should continue with public health advice of a balanced diet with limited processed and red meat and manage blood sugar through healthy lifestyles, including consistent exercise. Researchers will continue evaluating if nature’s cancer-resistant species can provide new ways to prevent cancer moving forward.
To reduce your risk of diabetes as well as cancer:
· Don’t smoke or use other tobacco-containing products.
· Be moderate with alcohol intake.
· Maintain a healthy weight throughout your life.
· Eat a plant-forward diet including a variety of fruits and vegetables
· Include more high-fiber, whole grains such as rolled oats, whole grain breads and cereals, barley, bulgur, farro, and quinoa.
· Add beans, lentils, and unprocessed soy foods like edamame or tofu to your diet.
· Avoid processed and cured meats like bacon, bologna, hot dogs, pepperoni, salami, sausage, and other deli meats.
· Limit red meat, fatty cuts of pork, butter, trans fat, and fried foods.
· Avoid fast food and ultra-processed frozen meals, snacks, and high-calorie desserts.
· Exercise regularly to maintain or reduce blood sugar and weight.
Lisa Andrews, MEd, RD, LD
References:
Stefania E. Kapsetaki, Anthony J. Basile, Zachary T. Compton, Shawn M. Rupp, Elizabeth G. Duke, Amy M. Boddy, Tara M. Harrison, Karen L. Sweazea, Carlo C. Maley. The relationship between diet, plasma glucose, and cancer prevalence across vertebrates. Nature Communications, 2025; 16 (1) DOI: 10.1038/s41467-025-57344-1
