Lipids are a class of essential nutrients found in foods and in the human body. Lipids are complex organic molecules that include triglycerides, phospholipids, and sterols.
This article will focus on triglycerides since the majority of dietary fats and oils, as well as stored fats in the human body, are in the form of triglycerides. Triglycerides are composed of a glycerol molecule with three fatty acids attached.
Body fat serves important roles for humans, such as energy stores, cushion to the organs, and insulation to protect against temperature extremes. Dietary fats and oils provide us with essential fatty acids (omega-3 and omega-6 polyunsaturated fatty acids), have 9 calories per gram, and add a feeling of satiety to our meals. Although collectively, the American culture has suffered from fat phobia since the 1970s (think of all of the food products that are marketed as fat-free, but are supposed to have fat in them, e.g. ice cream), a healthy adult requires 20-35% of total daily calories from fats and oils.
Fatty acids along the glycerol molecule differ in chain length and degree of saturation. Fatty acids are considered “saturated” when the chain is complete with hydrogen atoms; they tend to be solid at room temperature. Unsaturated fatty acids have hydrogen atoms missing along the chain; they tend to be liquid at room temperature (i.e. oils). If the fatty acid has one point of unsaturation (where a hydrogen atom is missing) along the chain, it is considered to be monounsaturated. If the fatty acid has two or more points of unsaturation along the chain, it is considered to be polyunsaturated.
Foods tend to be a combination of saturated and unsaturated fatty acids, but whichever is more present, that is what will determine the food’s physical properties (solid versus liquid at room temperature).
Trans-fatty acids result from a food processing method called hydrogenation. Food scientists discovered that by adding hydrogen atoms to unsaturated fatty acids, foods would resist rancidity, thus have a longer shelf life. Unfortunately, through this process of hydrogenation, trans-fatty acids result. Trans-fatty acids are rare in nature, but common in highly processed foods. These trans-fatty acids have an oddly shaped bond with which our body is unfamiliar, therefore problematic in the metabolic process. Excessive trans-fatty acid intake increases the risk of cardiovascular disease by raising LDL (bad) cholesterol and lowering HDL (good) cholesterol, and increasing tissue inflammation.
How does one know if the food one is eating has trans-fatty acids? The Nutrition Facts label is not always forthright. The Food and Drug Administration (FDA) allows food manufacturers to claim “trans-fat free” while the food can have up to 0.4 grams of trans-fatty acids per serving. That can add up if several servings of that food item are consumed in a day. The key is to read the ingredients list. If the word “hydrogenated” appears on the list, one can deduce there are trans-fatty acids in the product. Certain packaged cookies, cakes, granola bars, breads, and cereals may have hydrogenated oils in them. Read the ingredients list so that you can make informed decisions.
As stated previously, the average healthy adult requires 20-35% of total daily calories from fats and oils. Of that percentage, less than 10% ought to come from saturated fats. Saturated fat is higher in animal sources (e.g., red meat, eggs, butter, and full-fat dairy) and tropical “oils” (coconut and palm oils). Excessive dietary saturated fat is associated with cardiovascular disease, obesity, and cancer. Monounsaturated and polyunsaturated fats will make up for the remaining balance of dietary fat recommendations (e.g., seeds, nuts, vegetable oils, and fatty fish). The American Heart Association recommends that less than 1% of our total daily calories come from trans-fatty acids.
If you are curious about your dietary fat intake, there is an on-line tool you can use for diet analysis. It is free to use; you just need to register on the website to create an account. Go to www.SuperTracker.usda.gov, create an account, and follow the instructions. Once you have entered your diet and physical activity (three days provides a more accurate view), the program can generate reports and analysis based on the information you have entered. You might be surprised (or even alarmed) at the results.
The next article will cover the Mediterranean diet and its link with longevity. When in Rome!
James Davlin photo.