4.7: SPECIAL TOPIC: THE PALEO DIET
Given the impact of diet on every health condition discussed so far in this chapter, you may be considering changing what you eat. But what diet to follow? Given your interest in human evolution, have you ever wondered about the Paleo diet? Popularized by the 2002 book, The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You Were Designed to Eat, by professor of nutrition and exercise physiology Loren Cordain, the Paleo diet is an eating plan based on the idea that eating like our ancestors is protective against weight gain, metabolic disorders, and other maladies of modern life. Its publication spawned an entire industry of diets, exercise plans, cookbooks, and other products based on the “Paleolithic prescription.”
Recommendations of the Paleo diet include eating high amounts of protein, fewer carbohydrates, more fiber, certain fats, and foods rich in plant phytochemicals, vitamins, minerals, and antioxidants. Sounds good so far, but let’s dive a little deeper. Protein in the Paleo diet consists of lean meats (including organ meats), fish, and seafood. And not industrially produced versions of these. The meat should be grass- not grain-fed, and the fish should be wild caught, not farmed. All fruits are included in the diet, but only non-starchy vegetables make the cut, meaning no tubers like potatoes. The recommended carbohydrates have a low Glycemic Index, meaning they are more slowly digested and metabolised causing a lower, slower rise in blood glucose and insulin levels. There are also no cereals, no legumes (beans), no dairy products, no processed foods, no refined sugars (including honey), and no added salt. The primary fats in the diet are monounsaturated, polyunsaturated, and omega-3 fats, rather than the trans fats and saturated fats most often found in contemporary diets (Cordain 2002).
Particular attention is given to counteracting what many people think of as high-protein foods. Hamburger, eggs, and cheese, which are 24%, 34%, and 28% protein, respectively, are off the list, as opposed to skinless turkey breast (94% protein) and shrimp (90%). There is also the idea that current Western diets are more acidic than alkaline, reducing calcium levels in the body by promoting excretion of calcium in the urine. Cereals, dairy products, legumes, meat, fish, eggs, and salty processed foods elevate acid loads in the body, while fruits and non-starchy vegetables produce net alkaline loads. The diet advises eating 35% of your daily calories as fruits and veggies to balance out the high recommended protein intake. These recommendations are based on the premise that this represents a typical diet of hunter-gatherers in our ancient past before the transition to agriculture. Given what you have learned about human evolution from this text, what might be some problems with this assumption? How about with the diet itself?
To begin, there is no such thing as the Paleo diet. Hominins occupied a variety of ecological niches, with corresponding variety in what they ate (Lucock et al. 2014), including wide variation in their consumption of meat (Wrangham 2009). There is also archaeological evidence and dietary analysis of teeth demonstrating that hominin foragers ate cooked grains as far back as two million years ago (Zuk 2013). Although modern foragers are not an analogue for the past, they vary widely in their dietary intake. Meat forms 99% of the traditional Inuit diet (McElroy and Townsend 2009), while the diet of the !Kung of sub-Saharan Africa is mostly vegetarian (Lee 2013). In the case of the Inuit, they have genetic mutations related to the processing of omega-3 fatty acids that allow them to live on such a high-protein, high-fat diet without the cardiovascular disease and metabolic issues found in other populations (Fumagalli et al. 2015). Similarly, some pastoral populations became lactase persistent over time, allowing their members to digest milk as adults (Crow and Kimura 1970), and there are genotypes favored among peoples with high-starch diets that improve the digestion of starches (Marciniak and Perry 2017) and promote resistance to infectious disease (Lucock et al. 2014). Clearly, not all humans ate the same things, and natural selection favored genotypes that allowed populations to survive as they encountered new food sources and their diets changed. The modern Paleo diet also does not take into account the difficulty of procuring the lean protein that it recommends in the absence of hunting it yourself. Furthermore, it leaves out fermented foods, like pickled vegetables, yogurt, and cheeses, that contribute to a healthy microbiome (Graber 2014), something researchers are coming to find is essential to health (Shreiner et al. 2015).
What, then, to eat? As with Paleo diets, what humans eat today varies by geography, economics, and cultural preferences, among other factors. The burgeoning science of nutrigenomics hopes to one day be able to provide each individual with a customized diet based on analysis of your own DNA, lifestyle, and disease risk (Neeha and Kinth 2013). Until that time, World Health Organization dietary recommendations for the prevention of chronic diseases like cardiovascular disease, diabetes, and cancer emphasize diets that are low in saturated fat, salt, and sugar, high in fiber, and feature lean proteins (including nuts and fish) and carbohydrates from whole grains, legumes (beans), fresh fruits, and vegetables (WHO 2018c). Fiber, in particular, has been shown to be protective. Epidemiological and clinical studies demonstrate that intake of dietary fiber from plants and whole grains is inversely related to obesity, Type 2 diabetes, colon cancer, and cardiovascular disease (Lattimer and Haub 2010). Newer research suggests diets high in fiber also boost immune function, mood, and cognition (Kaczmarczyk et al. 2012).
Can these recommendations be met with a vegetarian or vegan diet? Research suggests this is the case, if one is conscientious and knowledgeable about the combination and timing of foods to obtain essential nutrients (McEvoy et al. 2012; Woo et al. 2014). Research introduced earlier in this chapter regarding the negative health effects of cooked meats suggests that eating meat four times per month or less, eating it rare, and avoiding processed meats altogether, is less likely to result in cancer, diabetes, and hypertension (Abid et al. 2014; Liu 2018; Liu et al. 2018; Trafialek and Kolanowski 2014). Additionally, according to the EAT-Lancet Commission on healthy diets from sustainable food systems, global consumption of foods such as red meat and sugar will have to decrease by half to make sure the Earth will be able to feed a growing population of 10 billion people by 2050. At the same time, people will need to double the amount of plant-based foods they eat, including nuts, fruits, vegetables, and legumes (Willett et al. 2019).
