It used to be simple. Sticking to a low-fat diet was the healthy way to eat. As we have learned more about types of fats and how they work in the body, it has gotten more complicated.
A recent study published in the American Medical Association’s journal JAMA Internal Medicine found that people who ate more fat from plants than from animals had better heart health and lived longer. In the study, more than 600,000 people filled out diet-recall questionnaires and were followed for 24 years. During that time, people who got more calories from plant fat than animal fat had up to a 30 percent lower risk of death.
This study confirmed what other studies have found. Not all fats are bad for you, and some are really good. The JAMA study had some design flaws, such as the fact that a single dietary recall was used to predict a diet over a 24-year period. Most people don’t keep the same diet for 24 years. People move; schedules, habits, taste preferences, and medical science all change.
The study also compared plant fats to animal fats, without accounting for some plant fats that are not good for you and some important animal fats that are very good for you. A better way to understand the good-fat diet is to compare saturated fats to unsaturated fats.
It’s also important to know that all fats have a role in healthy nutrition. Fats are an essential source of energy. Gram for gram, fat provides twice the calories for energy use as a gram of protein or carbohydrate. Fats also help keep your skin healthy, and you need fats to absorb and transport the essential vitamins A, D, E, and K. You don’t make these fats. They need to come from your diet. Without fats, you can’t absorb and transport them. Fats provide satiety, reduce inflammation, provide texture, and give flavor to foods. That being said, some fats are better than others.
Saturated fats
Saturated fats should be limited or avoided. Most of these fats are animal fats. They become solid at room temperature, like butter or lard. The American Heart Association (AHA) recommends limiting calories from saturated fat to less than 6 percent of your total calories. If you take in about 2,000 calories in a day, no more than 120 calories should be from saturated fat, which would be about half of a cheeseburger. Saturated fats increase you bad cholesterol, which deposits fats and cholesterol inside the arteries that supply your heart and your brain.
Among the worst types of saturated fats are those from processed meats like bacon, sausage, salami, and hot dogs. These foods are loaded with saturated fats and preservatives that have been linked to cancer. Cookies, pastries, and fast foods are also on the list. Other sources include lamb, pork, and poultry, although poultry without the skin is not high in saturated fat. Saturated fats from plants include coconut, coconut oil, and palm oil.
According to the Harvard School of Public Health’s Nutrition Source, Americans get most of their saturated fats from pizza, cheese, whole milk, butter, ice cream, sausage, bacon, beef, and hamburgers.
Trans fats
The worst of all saturated fats are called trans fats. These manufactured fats, which are made by adding hydrogen to vegetable oils, were invented to save money for food processing companies and fast-food restaurants. They enable food to be kept on the shelves longer, make vegetable oils solid, and can be reused many times for frying fast foods. Partially hydrogenated oil is another word for trans fats.
According to Harvard University, every two calories from trans fats increases your risk of coronary heart disease by 23 percent. Luckily, these fats have been all but eliminated from the American food supply by the FDA, but you should still look for the word trans fats or partially hydrogenated oils on any processed food labels.
Good unsaturated fats
Good fats are unsaturated and are liquid at room temperature. There are two types, monounsaturated and polyunsaturated. Unsaturated fats can improve good cholesterol, ease inflammation, and keep your heart beating normally. Numerous studies now agree that substituting unsaturated fats for saturated fats helps you live longer.
Monounsaturated fats are found in olive, peanut, and canola oils. Avocados are the best vegetable source. Almonds, hazelnuts, and pecans are the best nut sources, as well as pumpkin and sesame seeds. Polyunsaturated fats are found in sunflower, corn, canola, soybean, and flaxseed oils, walnuts, and flax seeds.
All these oils come from plants, with one important exception, and that is animal fats from fish. Fish are high in a polyunsaturated fat called omega-3. Like the fat-soluble vitamins, omega-3 fats are not made in the body and need to come from your diet. That’s why the AHA advises eating fish two to three times per week.
Numerous studies show that omega-3s
may lower the risk of heart disease, stroke, sudden blood clots, cancer, Alzheimer’s dementia, and age-related macular degeneration.
Bottom line on fats
The JAMA study research team calculated that replacing just 5 percent of the animal fat in your diet with plant fat was associated with up to a 25 percent decrease in death over the 24 years of their study.
Substituting unsaturated fat for carbohydrates (sugars) is also good for you. A review of more than 60 trials found that replacing carbs with unsaturated fats decreases bad cholesterol, increases good cholesterol, lowers blood pressure, and reduces the risk of cardiovascular disease.
One final and important reminder: All fats are high in calories, even the good ones. Too many calories can lead to being overweight or obese.
