Nutrition, Paleo diet, heart disease, diabetes, scott lear
The Paleo Diet: Just how healthy is it?
As an expert in the prevention of heart disease, I am often approached to answer questions on the value of various diets. In recent years, many people have been interested in the ‘paleo’ or ‘caveman’ diet. This diet consists of eating high amounts of protein from animal sources and is based on the premise that our ancestors from thousands of years ago subsisted mostly on animals for food and ate less plant-based foods. However, this theory is not grounded in either historical or scientific evidence.
The domestication of plants began nearly 10 000 years ago, and the majority of the world’s population was participating in agriculture between 3000 to 5000 years ago. When early domestication of animals did occur, it was primarily for obtaining animal milk and not for meat - protein from animal meat was not a significant source of energy in these early days, as protein came from plant sources. Almost all of the world’s current population descended from these agricultural societies, and our bodies have adapted to this type of diet. For example, the average size of an adult gut is 1 litre and can expand 2 to 4 times. This allows us to ingest large quantities of nutrient-poor foods so that our bodies can extract enough of what is needed to meet our nutrition needs. Even in hunter-gatherer populations of the past, food mainly came from the gathering of plants rather than hunting of animals. This is because it was hard work to track and hunt down game for food with spears and blunt tools, taking days or weeks, compared to collecting berries and pulses.
So why would this and other high-protein diets be popular? To answer that, we must first acknowledge that many of us do not get enough protein in our diets. Second, we need to understand the inherent challenge and impact when changing foods in our diet. To thrive, we each need a certain minimal amount of energy (calories) in our diet, otherwise our health and well-being deteriorate. Whenever we eliminate something from our diet, we still need to get the calories from somewhere. It is not like smoking where the net healthy amount of cigarettes is zero. We need food to live, unless we are purposely restricting calories. As a result, it can be the food that we replace another food with that has a greater impact on our health than what we have decreased or removed from our diet.
When the war on fat began in the 1950’s and 60’s, over the following decades, the amount of fat in people’s diets decreased. However, a common way people went about reducing fat was by reducing or eliminating animal sources of fat, which resulted in people eating less protein as well. They chose to replace the lost energy from fat and protein with energy from carbohydrate sources. These were predominantly refined carbohydrates like high sugar foods and foods that have a high glycemic index (which makes the body increase sugar levels in the blood), such as white bread, potatoes, white rice and white pasta. Compared to complex carbohydrates and protein, these foods are rapidly broken down and cleared from our gut, resulting in the urge to eat again. Recent studies indicate that if fats are replaced with refined carbohydrates, this is likely to increase a person’s risk for conditions like diabetes and heart disease. Meanwhile, if one replaces the fats with fruits and vegetables, this becomes a healthier change.
In our St. Paul's Hospital cardiac rehabilitation program, patients often report eating a diet high in carbohydrates and low in protein and fat, so we often recommend they eat more protein. Many of these patients think they are asked to eat a high-protein diet, when in fact, it is just that their previous diet was too low in protein. As we age, we also need more protein to prevent our body from breaking down our muscle, but unfortunately, it is common for people to eat even less protein in their later years. A common rule of thumb is about 1 gram of protein per kilogram of body weight, and this can come from animal or plant sources.
So what is one to make of all of this? Is there a perfect diet? It is unlikely that one sort of diet or pattern of foods is going to be right for everyone, as we are all slightly different. For some people, eating gluten or lactose is a problem, while others may have allergies or metabolize food quicker or slower. In addition, people have different tastes and likes. Even the healthiest diet is worthless if it isn’t eaten because a person does not like the way it tastes.
A number of different diets and food patterns have been studied over the years to look at effects on health. Most of these studies have looked at the effect of diets on things like blood pressure and cholesterol. Some long-term studies have looked at the impact of certain foods on cancer and heart disease, but these are often association studies in which it is hard to know if it is the diet or some other factor that is contributing to a person's health. This is because those people who eat healthy diets also often do not smoke, are physically active and have a generally good well-being. As a whole though, the common components in the diets with good health outcomes include daily fruits and vegetables, complex carbohydrates with an emphasis on whole grains, lean meats and poultry, and fish, legumes (beans and peas), good fats (including nuts and seeds) and moderate intake of alcohol, while limiting saturated fats, salt and refined carbohydrates.
In the last decade, one diet has been shown to conclusively reduce and prevent heart disease in randomized trials. This diet has been labelled the Mediterranean diet, as it has been patterned off of traditional diets of people living around the Mediterranean Sea in Europe. One glaring factor of the Mediterranean diet is that it consists of getting 40% of one’s calories from fat sources. This would be considered a ‘high-fat’ diet compared to other heart-healthy diets that recommend less than 30% of other “heart-healthy” diets. The caveat here is that the sources of fat come from foods like fish, nuts and vegetable oils that are high in the good (unsaturated) fats, while having a low intake of saturated fats. It also emphasizes regular fruits and vegetables, and red meat is discouraged. Protein is instead obtained by eating white meat, fish and protein from plant sources, thereby distinguishing it from the Paleo Diet.
Eating healthy and having a well-balanced diet is an important factor to preventing disease and maintaining health. However, we must keep in mind that nutrition is only one factor of a healthy and happy life. Regular physical activity, not smoking and managing stress levels are also some factors that we should all engage in.
Dr. Scott Lear is the Director of Community Health Solutions, Professor at the Faculty of Health Sciences and the Department of Biomedical Physiology and Kinesiology, Simon Fraser University, and the Pfizer/Heart and Stroke Foundation Chair in Cardiovascular Prevention Research at St. Paul's Hospital