A study released last month by Australian scientists linked an increased risk of heart disease to the paleo diet, but experts say that this study points to a larger issue about the direction of the diet industry.
"[This study] supported everything I thought about the diet," said Zachary Clayton, a postdoctoral researcher at the University of Colorado Boulder who is specializing in nutrition and physiology. "We can trust this data. But is more information needed? Yes."
The paleo diet is based on foods eaten during the Paleolithic era. A typical dietary plan for participants includes lean meats, fish, fruits, vegetables, nuts and seeds. People should avoid eating grains, legumes, dairy products, refined sugar, salt, potatoes and highly processed foods.
A 2018 study conducted by the International Food Information Council Foundation found that 7% of the 36% of Americans who followed a specific eating pattern or diet in that year participated in the paleo diet. Some studies have suggested that the paleo diet can aid in weight loss, boost glucose tolerance, lower triglycerides, and improve blood pressure control and appetite management, according to the Mayo Clinic.
Published in the European Journal of Nutrition, the July 2019 study screened 44 participants following the paleo diet against 47 who followed an Australian diet by asking individuals to state their dietary patterns. Scientists measured the amount of trimethylamine-n-oxide (TMAO) in the study participants’ blood. TMAO is an organic compound made by bacteria in the gut and is associated with an increase in cardiovascular disease risk. TMAO bacteria production is increased by nutrients like choline, which is found in red meat and eggs: two foods that Paleo dieters consume in high amounts.
“Many paleo diet proponents claim the diet is beneficial to gut health, but this research suggests that when it comes to production of TMAO in the gut, the paleo diet could be having an adverse impact in terms of heart health,” said Angela Genoni, lead study scientist and lecturer at Australia’s Edith Cowan University.
Clayton says that concluding a correlation exists between TMAO and increased cardiovascular disease is “a little strong to say.”
“[Scientists] showed that regardless of the diet they’re on, there’s no difference in blood pressure, systolic or diastolic, with these individuals,” Clayton said. “So right away, that tells me that the diet they’re on isn’t directly impacting their cardiovascular health.”
The study’s findings illustrated a positive impact for some cardiovascular disease risk factors, and a negative impact for others. Paleo increased participants' HDL, or high-density lipoprotein, which is known as “good” cholesterol because it helps remove other forms of cholesterol from your bloodstream and is linked to a lower risk of heart disease. The diet also shows a lower sugar intake, which is directly associated with lower cardiovascular disease risk. However, on the negative side, the paleo diet has a lower dietary and soluble fiber intake, which results from a lack of carbohydrate consumption.
“I think the public should be cautious when adopting a paleolithic diet; however, I don’t think this study is something to be ultra-concerned about,” Clayton said. “It’s an initial observation that paleo increases TMAO. I don’t think [people should stop diets] because things like the paleo diet might be getting these people to eat a lot more vegetables. I think there are certain things about the paleo practice that are absolutely great for human health broadly.”
The format of the Australian study was cross-sectional, which is observational and analyzes data from a population, meaning that causality cannot be proven. Clayton said future research could use an intervention-based study to understand the effects of a non-paleo diet versus a paleo diet in Americans. Clayton’s proposed intervention-based study would entail recruiting participants and placing half on a standard diet and half on paleo, taking measurements before and after their diets started, and switching them halfway.
Dr. David Jenkins of the University of Toronto said that his concern about the paleo diet is its abundance of meat and lack of whole grains. Increasing meat intake is not sustainable for the planet, and also brings “excess consequences” for the consumers, according to Jenkins. The sodium level in processed red meat is a risk factor for hypertension and vascular stiffness, both of which may increase the risk of mortality caused by stroke, heart failure and other factors, according to a study conducted by Harvard University professors. Jenkins recommends that people follow a balanced, plant-based diet, which offers more fiber and lowers cholesterol.
“There are two sources of health [with food],” said Jenkins, who is a professor in the Departments of Medicine and Nutritional Sciences. “You have to look at the aspect of human health and if it’s environmentally healthy. There’s no point in having an ideal diet if you’re destroying the planet.”
Genoni told NBC she hopes that her study encourages people to seek professional advice from a registered nutrition professional and to focus on a balanced diet that includes the fiber found in plant foods and whole grains.
Certified dietician Mary Jane Detroyer says that people tend to eliminate all starches because they don’t know how to follow a balanced eating pattern.
“[I] never ever, ever recommend any diet,” Detroyer said. “People are too easily swayed by diet culture. There is absolutely no research that correlates weight with health, no research that says people that are heavier die sooner than people that are smaller, or get more diabetes and heart disease. If you look at the research, it has to do with lifestyle.”
Detroyer does not encourage clients to follow diets unless it is for a health reason, such as celiac disease. Instead, she works to turn clients away from diet culture by helping them understand that fad diets like paleo lead people into yo-yo dieting, which is when people go on and off of a diet because it is not sustainable and thereby leads them to put on more weight than when they started.
“One of the things I’ll tell [clients] is to get off Instagram,” Detroyer said. “I encourage people to look at how their relationship with food develops. [Some] people are trying to achieve a goal that the only way they can achieve it is to starve themselves and over exercise.”
She noted that diet culture is getting worse. Detroyer said she has seen American culture move from women who didn’t exercise because it wasn’t “ladylike,” to women exercising to be very thin and control their weight. Now, women exercise and expect themselves to have perfectly sculpted bodies.
“It’s gone from nothing to expectations that are almost impossible to achieve,” Detroyer said. “Exercise has become almost like the diet. Women have felt guilty if they don’t get up and do it. And then they don’t feel like they can eat.”
She said that when it comes to eating patterns, the country is operating on two extremes: people that eat perfectly, and others who eat a highly processed diet that is full of chemicals.
“That’s where I’d like to see more research,” Detroyer said. “What micronutrients are missing in [these peoples’] bodies? What happens to people who just eat protein and no carbohydrates? I think so many people are messing with their muscles. So many of them think they’re building muscles, but many of them aren’t. They’re not eating enough food. They’re not eating the starches to give their brains the carbohydrates it needs.”
The American healthcare system is also not geared towards educating people and giving them the necessary support if they struggle with their eating patterns, according to Detroyer. She believes that doctors are perpetuating diet culture. They use body mass index (BMI) to determine whether people should diet. BMI was created for large population studies and was not designed to be used in individual situations.
“Even though the research says diets don’t work, doctors continue to tell people they need to go on a diet and need to lose weight,” Detroyer said. “Really, what [doctors] need to do is send [patients] to dieticians to find out what’s going on. Some people need help changing the behaviors and need to start exercising and learn to eat in a way that matches their budget. Then, there are the insurance companies who don’t provide the help people may need.”
Detroyer said that improving diet culture begins with education. Parents and schools need to read and learn more about the incidence of eating disorders, and how they talk to children about their bodies and diets.
“Diet culture is very psychological about how it catches on,” Detroyer said. “A father is walking down the street with his daughter and makes a comment about some woman. That impacts his daughter, and sometimes for a lifetime. We’re not aware of the impact.”