What Makes a Fat "Healthy"?
In the world of nutrition and dietetics we tend to stay away from the terms “good” and “bad” to instead promote the idea of things being healthier than others. Avocados are currently a hot topic because of all the popularity they’ve gained from being labeled as a “good fat”. Avocados are not a good fat because there is no such thing as a bad fat. Fat is needed in the diet to sustain life, it helps build cell membranes, absorb vitamins and minerals and is a major source of energy; so how can some of it be bad? Avocados though are a healthier fat than say ice cream, but that doesn’t mean we should add them to every meal or completely avoid ice cream; just that they can be held to higher standards than ice cream. There are four different types of fats; trans, saturated, monounsaturated and polyunsaturated. Current recommendations for fats say that you should minimize intake of trans fatty acids, which are found in animal fats including hydrogenated oils, meat and dairy. (1) Saturated fats are primarily found in animal fats, meat and dairy and should be consumed in moderation. (2) Monounsaturated and polyunsaturated fats, which includes fish oils, nuts/seeds and avocados, are the “healthy” fats. So why are some fats more beneficial than others?
Fats all have the same base chemical structure, a chain of carbon atoms attached to hydrogen atoms, but they differ in the length of the carbon chain and the number of hydrogen atoms. These differences change the function of the fat. Trans fats are man made through a process called hydrogenation. This process basically makes the fats shelf stable for mass production. Trans fats raise our harmful LDL cholesterol and lowers the beneficial HDL cholesterol, which causes clogged arteries, heart disease, and strokes. (3) They are found in most junk and fast foods as well as hydrogenated oils like margarine. Saturated fats are found in meat and dairy products and mass-produced junk foods. (2) They are saturated because their chemical structure holds as many hydrogens as possible and are solid at room temperature. A diet high in saturated fat raises the harmful LDL cholesterol which can lead to clogged arteries and heart disease. It is recommended that you consume less than 10% of your total calories a day from saturated fats. (4) Monounsaturated and polyunsaturated fats are naturally found in vegetables, nuts, seeds and fish. They have fewer hydrogen atoms in their chemical structure (unsaturated) and are liquid at room temperature. Monounsaturated fats are found in olive oil, avocados and nuts and are the main nutrient in a Mediterranean style way of eating. (5) This style promotes a diet high in these healthier fats to reduce risk of heart disease and stroke. Polyunsaturated fats are essential fat; meaning they are required from the diet because your body can’t make them. There are two types: omega-3 and omega-6. Omega-3 are found in things like flax, soybean, salmon, and walnuts and reduce blood pressure, raise the beneficial HDL cholesterol and prevent heart disease. Omega-6 are found in soybean, sunflower and corn oils and help to prevent heart disease. (4) The average adult in the US is currently overconsuming omega-6 and under-consuming omega-3 based on the AI (Adequate Intake set by the Institute of Medicine of the National Academies). The AI for omega-6 is between 10-17 grams/day for an adult; currently the average intake is 20-25 grams/day. The AI for omega-3 is between 1.0-1.6 grams/day with the average actual intake only being 0.2-0.4 grams/day. (6) There is some controversy on this though as AI’s are set when there isn’t enough research to make solid recommendations, but it is known that when mono and polyunsaturated fats are used instead of trans and saturated fats they have beneficial effects on the body.
So, are avocados the end all to heart disease and unhealthy diets? Not exactly, even though mono and polyunsaturated fats have been shown to lower the risk of heart disease and are heavily promoted as “healthy fats” there is still conflicting research on this topic. Currently there is not an RDA (Recommended Dietary Allowance set by the Institute of Medicine of the National Academies) for fats because there isn’t enough research that all points to the same conclusion for consumption of mono and polyunsaturated fats.7 All we know right now is that consumption of trans and saturated fats should be decreased in order to protect your heart health and promote an overall healthy life.