Paleo Diet Study Links 'Caveman' Regime to Heart Disease Biomarker

Scientists who studied a small group of paleo diet followers found a substance linked to heart disease in their bodies, according to a study.

The research published in the journal European Journal of Nutrition involved 44 people who said they followed the Paleolithic diet, also known as "paleo" or "caveman" for at least a year, and 47 people who largely stuck to the regime recommended by the Australian government. Dr Angela Genoni of Edith Cowan University and colleagues wanted to check whether claims the paleo diet promotes gut health stand up.

Inspired by what our ancestors—who lived in the Paleolithic era, between 2.5million to 10,000 years ago—are thought to have eaten, the regime features a lot of lean meats, fish, fruits, vegetables, nuts, and seeds. But it is low in foods that require farming, like dairy products, grains, and legumes. In the new study, participants qualified for the paleo group if they ate no more than one serving per day of grains and dairy products.

Researchers separated the paleo devotees into two categories: "strict": those who excluded grains and dairy; and "pseudo": those who ate a lower than average level of resistant starch. The authors also collected information on the participants' age, gender, diet, and body fat percentage. Participants also provided blood, and a stool sample so the researchers could examine the make-up of their gut bacteria.

All of the paleo participants were found to have higher levels of Hungatella, a bacteria which produces trimethylamine-n-oxide (TMAO), a metabolite linked to red meat and a biomarker associated with heart disease. One study published in 2017, found people with high levels of TMAO had a 62 percent increased risk of having a major cardiovascular event, and a 63 percent higher risk of dying overall.

And compared with the control group, the strict paleo group had higher levels of TMAO in their blood. In contrast, those who ate whole grains had lower levels of TMAO.

This link is potentially concerning. In the U.S., around 610,000 people die of heart disease each year, making up one in four deaths, according to the Centers for Disease Control and Prevention.

The authors of the latest study wrote: "Although the PD [the Paleolithic diet] is promoted for improved gut health, results indicate long-term adherence is associated with different gut microbiota and increased TMAO. A variety of fiber components, including whole grain sources may be required to maintain gut and cardiovascular health."

Genoni and colleagues are among scientists inspired to investigate the potential harms and benefits of paleo as it has gained popularity in recent years. Some of its adherents stand by what is known as the discordance hypothesis, arguing that the human body isn't equipped to cope with diets featuring farmed foods. They claim the regime can help you lose weight, and avoid conditions like heart disease and diabetes.

But experts are worried about the effects of cutting out whole grains and dairy, which it is feared could lead to nutritional deficiencies, and problems related to not eating enough fiber. Eating a lot of meat, meanwhile, has been linked to heart disease and diabetes.

The authors of one study published last year on low-carb diets—including paleo— warned regimens low in carbohydrates are unsafe and should be avoided.

Dr. Angela Genoni, lead author of the study, commented in a statement: "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.

Genoni said she believes a lack of whole grains could be to blame.

"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.

"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."

Genoni said whole grains "are a fantastic source of resistant starch and many other fermentable fibres that are vital to the health of your gut microbiome."

She argued: "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."

Victoria Taylor, senior dietician at the British Heart Foundation told Newsweek: "The role of gut health in the prevention of heart and circulatory diseases is a new but growing area of research.

"The research is not encouraging reading for anyone considering a paleo diet to lower their risk of heart and circulatory diseases," she said.

Taylor concluded: "The paleo diet may seem to be a healthier type of low carb/high protein diet because it includes fibre-rich fruit, vegetables, nuts and seeds. However, this study suggests that we need to think about the types of fibre we consume as well as how much we eat. By excluding grains and legumes, you may miss out on the different types of fibre as well as the other nutrients that these foods provide."

Aisling Pigott, a qualified dietitian and spokesperson for the British Dietetic Association told Newsweek: "It is difficult to define a paleo diet as diet and lifestyle have changed so much since paleolithic times that accessing that type of food would be impossible. In addition, different people interpret 'paleo' in different ways."

She advised readers to "always question and investigate what you are being told. If it sounds too good to be true, it probably is. There is no 'one size fits all' approach when it comes to diet and lifestyle."

This article has been updated with comment from Victoria Taylor, and Aisling Pigott.