Much of the confusion happens when people make generalizations about fat in the diet. Many diet books, media outlets and blogs talk about fats as though they were all the same. In reality, dozens of fats are common in the diet, and each one has a different role in the body and effects on your health. Even within groups of fats like saturated, unsaturated and polyunsaturated, specific fats still have different roles. Fat is an important part of your diet, but figuring out how much to eat can be confusing.
Decades ago, common sense was to eat fatty foods because it was the most efficient way to get energy. Fat contains more calories by weight than any other nutrient. Over time, scientists began to understand that some fats are healthier than others. In the 1930s, Russian scientists found that feeding animals very high cholesterol diets caused atherosclerosis. This is a condition where plaque builds up in the arteries, narrowing them and increasing the risk of heart disease. Atherosclerosis is the most prominent cause of heart disease and stroke. In the 1940s and ‘50s, heart disease in multiple countries decreased. Many attributed this phenomenon to wartime rationing in World War II. This fueled the belief that fat and cholesterol, which were high in the restricted foods, contributed to heart disease. Though there are many factors to heart disease, not all fats are bad or the problem.
Along with protein and carbs, fat is one of the three macronutrients in your diet. Most of the fats you eat are long-chain fatty acids. Short-chain fatty acids are mainly produced when bacteria ferment soluble fiber in your colon, although milk fat also contains small amounts. Long-chain and very-long-chain fats are absorbed into the bloodstream and released into the body’s cells as needed. However, short-chain and medium chain fats are taken up directly by the liver to be used as energy.
Monounsaturated fatty acids (MUFAs) have one double bond in their carbon chains. MUFA food sources are typically liquid at room temperature and fairly stable for cooking purposes. The most common MUFA is oleic acid, which olive oil contains in high amounts. Monounsaturated fat is linked to several health benefits, including a reduced risk of serious diseases such as heart disease and diabetes.
Polyunsaturated fatty acids (PUFAs) contain two or more double bonds. They can be divided into groups depending on the location of the double bonds. These include omega-3s and omega-6s. These double bonds make PUFAs more flexible and fluid than saturated fats. On the other hand, they’re also far more prone to damage and rancidity. Studies have found that long-chain omega-3 fats have benefits for inflammation, heart disease, diabetes, depression and other health conditions. Although you need some omega-6 fats, they can be inflammatory when consumed in excess, especially if omega-3 PUFA intake is low.
Saturated fatty acids (SFAs) have no double bonds in their carbon chains, so the carbons are said to be “saturated” with hydrogen. They are very stable at high temperatures and far less likely to be damaged during cooking than polyunsaturated fats. SFA intake can raise LDL (“bad”) cholesterol levels in some people, although this depends in part on the specific fatty acids consumed. It should also be noted that HDL cholesterol typically goes up as well.
In a trans fats molecule, hydrogens are positioned across from each other rather than side by side. Small amounts of trans fats occur naturally in dairy and other animal foods. However, nothing is natural about the trans fats used in processed foods. These trans fats are produced by adding hydrogen to unsaturated fats to create a product that functions more like a saturated fat. Ingredient labels often list them as “partially hydrogenated” fats. Consuming trans fats can lead to a number of health problems. Artificial trans fats are linked to inflammation, unhealthy cholesterol changes, impaired artery function, insulin resistance and excess belly fat.
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