Types of Dietary FatThere are three main types of dietary fat: unsaturated, saturated, and trans.
Unsaturated Fats: Often referred to as the “good” fats, unsaturated fats are either monounsaturated or polyunsaturated. According to the Harvard Medical School, unsaturated fats are usually liquid at room temperature and are found mainly in plant–based sources. Polyunsaturated fats are referred to as essential fats because the body requires them for good health but cannot synthesize them on its own, so they must be obtained from food.
Unsaturated fats can be found in olive, peanut, sunflower, corn, soybean, and flaxseed oils; avocados; nuts; seeds; and fish. Unsaturated fats are considered to be beneficial because they may help improve and maintain blood cholesterol levels, reduce blood pressure, ease inflammation, and stabilize heart rhythms.
Saturated Fats: According to the American Heart Association (AHA), “From a chemical standpoint, saturated fats are simply fat molecules that have no double bonds between carbon molecules because they are saturated with hydrogen molecules.”
These fats can be found in red meat, butter, whole milk, dairy products made with whole or 2 percent milk, cheeses, palm and coconut oils, and many commercially prepared baked goods and fried foods.
Interestingly, recent research has called the association between saturated fats and cardiovascular disease into question. A systematic review and meta-analysis examining the association between dietary fatty acids and coronary heart disease (CHD) published in the March 18, 2014 Annals of Internal Medicine, concluded that, “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.” A meta-analysis of 21 studies that appeared in the March 2010 issue of The American Journal of Clinical Nutrition found that there was not enough evidence to conclude that saturated fat increases the risk of CHD or cardiovascular disease (CVD).
Despite this conflicting evidence, the AHA recommends limiting saturated fats to less than 7 percent of one’s total daily calories because “Decades of sound science has proven it can raise your “bad” cholesterol and put you at higher risk for heart disease.”
Trans Fats: There are two types of trans fats in the diet: those formed naturally and those created during food processing.
Those formed naturally are produced in the gut of some grazing animals. According to the AHA, trans fats that are created during processing (also called “partially hydrogenated oils”) “are created in an industrial process that adds hydrogen to liquid vegetable oils to make them more solid.”
The primary source of trans fats in the American diet are foods containing industrially–modified and partially–hydrogenated vegetable oils such as fried foods, pizza dough, pie crust, margarine, chips, and commercially baked goods such as pastries, cookies, doughnuts, and crackers.
Artificial trans fats are harmful because they raise bad (LDL) cholesterol levels and lower good (HDL) cholesterol levels, which are risk factors for heart disease. The AHA recommends limiting artificial trans fats to less than one percent of total daily calories.
Benefits of FatsAlthough the excessive consumption of some fats can cause serious health issues, individuals should not cut out fats altogether because fats are essential to health. In addition to providing the body with energy, fats serve many other important functions; according to Harvard Medical School, fats aid in:
- The absorption of the fat-soluble vitamins A, D, E and K as well as carotenoids
- Blood clotting
- Muscle movement
- Building cell membranes
- Building the sheaths that surround nerves