· By Craig Morantz
Fat: Friend or Foe?
Traditional dinner party etiquette admonishes the discussion of religion, politics, and money, noting that these topics can quickly polarize a room and create an air of uncomfortableness. However, in my experience, nothing seems to divide a room quite like a discussion about diet.
If you’re already vegan, you’ll likely agree that plant-based eating is a fantastic way to lose weight, improve blood glucose, lower cholesterol, normalize blood pressure, eat healthier, and lead a harm-free lifestyle (1). Where vegans tend to disagree is the ideal ratio of carbs to fat to protein needed to achieve said benefits. In light of the keto craze, many vegans have switched to a high fat/low-carb diet, while others have remained steadfast believers in the teachings of McDougall and Barnard, adhering to an 80/10/10 diet or a high-carb/low-fat way of eating. So, what’s a vegan to do?
The first step is moving away from our biases and assumptions and taking an objective look at the research. However, it’s important to understand that nutrition research can often leave us with more questions than answers. Studying human nutrition is incredibly challenging given the number of variables to control for, such as stress, exercise, sleep, and other dietary components. Plus, there are those variables like genetics that can’t be controlled, yet still have a significant impact on a study’s outcomes. All this to say that even after diving headfirst into the latest health and nutrition research, we may not find all the answers we are looking for.
"It’s important to understand that nutrition research can often leave us with more questions than answers."
A Brief Overview of Dietary Fats
In sorting out the confusion surrounding the ideal macronutrient ratios, the most logical place to start is with a detailed discussion on fat, given that it is this nutrient that separates the low-carb from the high-carb eaters.
All fats are made up of carbon chains of varying lengths connected to hydrogen atoms. A fat is saturated when there are no double bonds, or extra space, in between the carbon atoms, leaving them “saturated” with hydrogen. Saturated fats can be further classified based on their carbon chain length from short to very-long chain fatty acids.
Saturated fat is predominantly found in foods of animal origin but is also found in high concentrations in coconut and palm oil. Compared to unsaturated fats, which are liquids at room temperature, saturated fats are usually solid.
What differentiates an unsaturated fat from a saturated fat is the presence of one or more double bonds along its carbon chain. When only one double bond is present, the fat is termed monounsaturated; when there are multiple double bonds, the fat is polyunsaturated. Foods high in monounsaturated fat include canola oil, high-oleic safflower oil, macadamia nuts, and avocado. Two of the most common types of polyunsaturated fats are omega 6, found in vegetable oils, nuts and seeds, and some animal products, and omega 3, found in flax, chia, hemp, algae and fish.
Trans fats are unsaturated fats that are naturally found in very small amounts in foods of animal origin. However, humans have discovered that they can create trans fats by turning an unsaturated fat into a saturated fat through a process called hydrogenation. Common examples of foods containing hydrogenated fats include cake frosting, stick margarine, crackers, fried fast food, and frozen pizza. And while trans fat is beneficial to the food industry since it prolongs a product’s shelf life, it has been consistently linked to cardiovascular disease and will therefore be banned from use in Canada in 2018 (2).
Fats in our food are categorized as saturated, monounsaturated, or polyunsaturated based on the type of fat that they are predominantly made up of. For example, because olive oil is 73% monounsaturated (and only 11% polyunsaturated and 14% saturated), it is classified as a monounsaturated fat.
"Fats in our food are categorized as saturated, monounsaturated, or polyunsaturated based on the type of fat that they are predominantly made up of."
Dietary Fats and Human Health
Rather than head down a long and boring road that details the impact of fats on all health conditions, I want to zero in on those that I am most often asked:
1) What’s the deal with saturated fat? Is it really no longer linked to heart disease?
2) Should I avoid oil?
3) Is keto-vegan the way to go?
Saturated Fat and Heart Disease
Prominent organizations, such as the American Heart Association and the World Health Organization, have been advocating for a reduction in the intake of saturated fat ever since it was linked to an increase in LDL cholesterol (also known as “bad” cholesterol), a risk factor for cardiovascular disease. However, in 2014, a paper that looked at the combined results of 72 studies concluded that trans fat was the only dietary fat clearly linked to cardiovascular disease and suggested that conventional advice on dietary fats be revised (3). However, a closer look at the study’s design, and the nature of dietary studies used, added plenty of grey into this black and white statement.
What decades of research has demonstrated is that when polyunsaturated fats replace saturated fats, the risk of cardiovascular disease decreases (4). However, the same can’t be said for carbohydrates unless those carbohydrates come from whole grains, such as quinoa, oatmeal, bulgur, and barley(4).
"A healthy diet is one that includes carbs, protein, and fat; what matters most is the source of these nutrients and the overall dietary pattern that you follow."
Whole-Foods Plant-Based, No Oil?
Most of the well-known plant-based physicians, including Greger, Barnard, and Esselstyn, advocate for the avoidance of vegetable oils stating that they impair endothelial function (i.e. cause stiff and inflamed blood vessels) which is an important risk factor for heart disease (5). However, not all studies have duplicated this finding, with a recent systematic review and meta-analysis suggesting that olive oil may in fact decrease inflammation and improve endothelial function (6). That said, there are still plenty of valid reasons for someone to reduce their intake of added oils, which we’ll discuss shortly.
What’s the Deal with Keto?
A keto diet is one that restricts the dietary intake of carbohydrates, causing the body to deplete its glucose stores and produce ketones which are then used for energy. Keto diets have been around for a lot longer than most people realize; they were originally considered a therapeutic diet in the treatment of childhood epilepsy, but are used today as a means to lose weight. While there’s no denying that eating keto will help you to lose weight in the short-term (given that calories are restricted, satiety is increased, and a significant amount of water weight is being lost), the long-term impact of eating keto on weight and health is still largely unknown. Most importantly, it’s clear that you don’t need to eat keto if you are already following a whole-foods, plant-based diet given that research shows that those following such a dietary pattern have lower body mass indexes, greater nutrient intakes, and ideal cardiometabolic profiles (1).
The key message to take away is that fat doesn’t need to be feared. A healthy diet is one that includes carbs, protein, and fat; what matters most is the source of these nutrients and the overall dietary pattern that you follow. I encourage everyone to follow an unprocessed, whole-foods vegan diet, limiting the intake of saturated fat and using oil (preferably high-quality extra-virgin olive oil) on an as-needed basis and ideally in an uncooked form. When oils are heated, free radicals are introduced that are known to contribute to cell damage. Furthermore, oils are still a processed food that are high in calories and low in nutrients. Aim to meet your fat needs through healthy, unprocessed foods like flax, chia, hemp, avocado, nuts, seeds, and nut or seed butter. Lastly, keto diets do not confer any additional benefit to someone already following a whole-foods plant-based diet, especially when you consider the planetary and ethical advantage of avoiding animal products.