Can these 2 ancient diets curb chronic disease?

Doctors and nutritionists—and everyone in between—have spent decades trying to find the perfect diet. From miracle foods to can’t-miss fads, the diet industry is worth some $72 billion, and yet millions struggle to keep off pounds.

Could the answer have been there all along, in the form of ancient diets?

Many Americans have tried two of the latest diet trends—Paleo and Primal. Both are rooted in primitive humans’ food sources and, though similar, they have important differences. The Paleo diet is modeled on the foods that people living during the Paleolithic era (from around 2.5 million years ago to 10,000 BC) would have eaten. The Primal diet is similar, but specifically eliminates foods that have been introduced in the past 100,000 years and places greater emphasis on overall lifestyle changes in addition to diet, like frequent movement and high-intensity training.

Despite gaining massive popularity in the last decade, many health-conscious foodies remain skeptical of the Paleo and Primal approach to eating. The logic that underpins the diets seems sound: Early humans had lower rates of chronic diseases like obesity, heart disease, and diabetes because of their diets, so if we want to lower rates of chronic disease, we should model our diets after theirs. However, few studies have evaluated the effectiveness of these diets.

Still, absence of evidence isn’t evidence of absence. Here’s where these two diets succeed and fall short in boosting health and preventing chronic disease, according to the data we do have.

Paleo diet

At its core, the Paleo diet is based on what people would have eaten during the Paleolithic era, with the idea that humans are not genetically suited for metabolizing many of the foods produced by modern agriculture. This places an emphasis on foods like lean meats, fish, fruits, nuts, and vegetables. It eliminates dairy, legumes, and grains, as well as anything processed. It’s heavy on healthy fats and oils and it avoids artificial sweeteners or any trans fats. Good-bye soda, hello coconut oil.

Though increasingly popular, the Paleo diet and its potential health benefits are still under scientific investigation. A few peer-reviewed studies have looked at the diet and offer some insight into its effectiveness.

A 2019 meta-analysis published in Nutrition Journal reported a positive association between the Paleo diet and weight loss, along with significant reductions in waist circumference and body mass index. In participants who followed the Paleo diet for up to 24 months, investigators found a mean weight loss of 3.52 kg (or 7.76 lb) compared with those who followed other diets.

Another weight-loss specific study published in the European Journal of Clinical Nutrition found that its 14 participants lost an average of 5 lb and their BMI decreased by 0.8 after a 3-week intervention. Participants reduced their energy intake by 36% and saw improvements in fat composition, antioxidants, and potassium-sodium rates. However, decreases in healthy calcium intake were also observed.

Because excess weight is associated with a significantly greater risk of mortality as well as several chronic diseases, it’s reasonable to assume that in some cases the Paleo diet can help people curb chronic disease and even lower the risk of mortality. But the evidence isn’t wholly convincing in this area and a causal link hasn’t been established. In the meta-analysis above, researchers found mixed results—most studies noted improvements in the risk of type 2 diabetes, metabolic syndrome, cardiovascular disease, and cancer, while one study found adverse effects (worsening cholesterol levels), and one found no effect at all. Further research is sorely needed.

Other studies have looked at specific processes within the body. In February 2020, the Journal of Clinical Medicine published a systematic review and meta-analysis of four studies involving 98 subjects to determine how the Paleo diet affects glucose and insulin levels as compared with other popular diets, including the Mediterranean diet and a diabetes-centric diet. The study found that the Paleo diet offered similar results as diets that have been studied for their positive outcomes on glucose and insulin levels, highlighting a potential link between the Paleo diet and the possibility of diabetes prevention or control.

Another study, published in Cardiovascular Diabetology, had 13 people with type 2 diabetes follow the Paleo diet or a more typical diet for diabetes, each for 3 months. Not only did following the Paleo diet lead to more weight loss, it also led to a bigger decrease in HbA1C and a higher increase in HDL cholesterol levels—more evidence that the diet has beneficial effects relevant to diabetes control.

Many studies have found short-term benefits with a small number of participants, but few studies have looked at long-term effects. A study in the European Journal of Clinical Nutrition followed 70 postmenopausal, obese women in Sweden for 2 years. Those on the diet saw significant results in the first 6 months, including reduced waist circumference and fat loss. However, the fat loss did not continue at the same pace for the entire 24 months, though triglycerides remained lower.

Authors of an article in the Harvard School of Public Health Diet Review stated, “The Paleo diet includes nutrient-dense whole fresh foods and encourages participants to steer away from highly processed foods containing added salt, sugar, and unhealthy fats. However, the omission of whole grains, dairy, and legumes could lead to suboptimal intake of important nutrients. The restrictive nature of the diet may also make it difficult for people to adhere to such a diet in the long run. More high-quality studies including randomized controlled trials with follow-up of greater than one year that compare the Paleo diet with other weight-reducing diets are needed to show a direct health benefit of the Paleo diet. Strong recommendations for the Paleo diet for weight loss cannot be made at this time.”

Primal diet

The Primal diet was developed in 2009 by Mark Sisson, a noted triathlete. The concept of this diet is similar to that of the Paleo diet in that it focuses on the foods that were accessible to our primal ancestors. Similar to the Paleo diet, the Primal diet focuses on fish, vegetables, nuts, healthy fat, and lean meats. And like the Paleo diet, it restricts any artificial or processed foods.

The main differences between the two diets center around milk-based products. The Primal diet encourages consuming raw, full-fat dairy, including cheese, while the Paleo diet nearly eliminates it. It’s important to note that raw milk can carry germs such as E. coli and Salmonella and is illegal in some states.

Other differences include the drinking of coffee (Primal says yes, Paleo says no), and the consumption of so-called nightshade vegetables like tomatoes, peppers, and eggplant (Primal says yes, Paleo is less enthusiastic).

Though eating foods prescribed in the Primal diet has been linked to some health benefits, like improvements in HDL cholesterol, it’s important to note that there has yet to be any significant studies on the diet’s effectiveness. Furthermore, many of the claims regarding the diet’s effectiveness are devised from studies of individual habits that the Primal diet recommends, rather than any large-scale studies of the Primal diet itself. In other words, since the Primal diet is so similar to other diets, like Paleo and the Mediterranean diet, proponents may support the Primal diet’s efficacy by using data from studies that tested similar diets. But the Primal diet differs in important respects that have not yet been scientifically tested, so these comparisons have to be treated with caution.

Are these diets effective?

Both of these diets are based on the ways our ancestors ate, eschewing highly-processed foods in favor of lean meats and high-fat products. The diets claim to not only help with weight and fat loss, but studies show that they also benefit cholesterol and glucose levels, and help to reduce blood pressure.

This means that these two diets could make a big difference for those looking to treat or prevent chronic diseases like diabetes, cardiovascular disease, cancer, and others. But the fact remains that although the Paleo and Primal diets share characteristics with other successful diets, both are dogged by a lack of full-scale, scientific research. The Paleo diet has been the subject of a number of studies, although most have been short-term and focused on a small number of participants. And, according to a search of the National Library of Medicine, there has yet to be any peer-reviewed study on the Primal diet’s effectiveness.

Because eating highly processed foods can, according to a 2019 study in Cell Metabolism, contribute to overeating and weight gain, avoiding them and eating more fresh foods, as laid out in both diets, makes sense.

However, due to the lack of research, it’s prudent to approach both diets with caution and to wait until more studies have been done before concluding that they can curb chronic diseases.