Home & Garden Home The Problem With the Paleo Diet By Melissa Breyer Editorial Director Hunter College F.I.T., State University of New York Cornell University Melissa Breyer is Treehugger’s editorial director. She is a sustainability expert and author whose work has been published by the New York Times and National Geographic, among others. our editorial process Melissa Breyer Updated May 21, 2020 ©. hlphoto Share Twitter Pinterest Email Home Sustainable Eating Pest Control Natural Cleaning DIY Family Green Living Thrift & Minimalism New research finds that a heart disease biomarker is linked to the 'caveman' diet. On paper, the paleo diet makes sense. The gist of it is to eat like a hunter-gatherer, because, its advocates say, the human body is optimally designed to eat in the ways we did before the onset of agriculture some 10,000 years ago. The diet – alternatively known as the Paleolithic diet, Stone Age diet, hunter-gatherer diet and caveman diet – is very popular. And why wouldn't it be? The desire to reject the modern food system seems pretty smart. People on a paleo diet usually rave about how great they feel; many report losing weight. The mix of meats, fish, vegetables, nuts and seeds typically comprise a lower-carb diet absent of modern-day junk food. No dairy products, legumes, grains, salt, processed oils, and refined sugar; no cookies! No wonder people feel good. But just like most low-carb diets – from Atkins and keto to the rest – the abundance of meat and a dearth of whole grains is cause for controversy. Paleo Diet and Gut Bacteria And now, the world's first major study examining the impact of the paleo diet on gut bacteria has come to a troubling conclusion: People who follow the paleo diet have twice the amount of a key blood biomarker linked closely to heart disease. Researchers from Edith Cowan University compared 44 people on the diet with 47 following a traditional Australian diet. They measured the amount of trimethylamine-n-oxide (TMAO) in the study participants' blood. TMAO is an organic compound in the gut, of which high levels are associated with an increased risk of heart disease. Lead researcher Dr. Angela Genoni said that as the diet continues to grow in popularity, it was prudent to gain a better understanding of the impacts it may have on one's health. "Many Paleo diet proponents claim the diet is beneficial to gut health, but this research suggests that when it comes to the production of TMAO in the gut, the Paleo diet could be having an adverse impact in terms of heart health," she said. "We also found that populations of beneficial bacterial species were lower in the Paleolithic groups, associated with the reduced carbohydrate intake, which may have consequences for other chronic diseases over the long term." Heart Health and Whole Grains Heart-healthy diets always include a lot of whole grains, of which any low-carb diet will obviously exclude. And Genoni says that the reason TMAO was so high in paleo eaters diet appeared to be the absence of whole grains. "We found the lack of whole grains were associated with TMAO levels, which may provide a link between the reduced risks of cardiovascular disease we see in populations with high intakes of whole grains," she said. In addition, they found higher concentrations of the bacteria that produce TMAO amongst the paleo group. "The Paleo diet excludes all grains and we know that whole grains are a fantastic source of resistant starch and many other fermentable fibres that are vital to the health of your gut microbiome," Genoni said. "Because TMAO is produced in the gut, a lack of whole grains might change the populations of bacteria enough to enable higher production of this compound." Red Meat and Cardiovascular Disease And then there's the elephant in the room: The meat. "Additionally, the Paleo diet includes greater servings per day of red meat, which provides the precursor compounds to produce TMAO," Genoni said. But ramping up one's meat intake is also a miserable thing for the planet, not to mention the animals. We are ripping out essential rainforest to make room for cows; and raising animals for meat is just too resource intensive to sustain for the billions of people now inhabiting the planet. If anything, we need to be cutting way back on our meat intake. For people in the United States, for example, a comprehensive new report concluded we need to be reducing our meat consumption by nearly half of current levels. But in the end, if one is not worried about the animals or the planet, personal health concerns remain. As the authors conclude, "high fat and low carbohydrate intake may not be beneficial for long-term health." The research, "Long-term Paleolithic diet is associated with lower resistant starch intake, different gut microbiota composition and increased serum TMAO concentrations," was published in the European Journal of Nutrition.