What Are Dietary Fats?
Dietary fats are a type of nutrient in food. "Fat" used to be a bad word in nutrition. Years ago, your doctor might have recommended that you limit or avoid fat in your diet to prevent weight gain and health problems like heart disease and diabetes. Now, doctors know that all fats aren't bad. Some fats lower your cholesterol level and help keep you healthy. You need some fat in your diet.
Fats have many important functions in your body. They:
- Give you energy
- Keep your body warm
- Build cells
- Protect your organs
- Help your body absorb vitamins from foods
- Make hormones that help your body work the way it should
The key is to get a good balance of fats and other nutrients in your diet. Eat the healthiest kinds of fats, in the right amounts. Unsaturated fats are the healthy fats. Saturated and trans fats are generally not as good for you.
Saturated vs. Unsaturated Fats
The difference between dietary fats lies in their chemical structure. All fats are made up of a chain of carbon atoms that are linked -- or bonded -- to hydrogen atoms.
- In saturated fats, the carbon atoms are totally covered, or "saturated," with hydrogen atoms. This makes them solid at room temperature.
- In unsaturated fats, fewer hydrogen atoms are bound to carbon atoms. These fats are liquid at room temperature.
A diet rich in saturated fats can drive up your total cholesterol and tip the balance toward more harmful LDL cholesterol, which can lead to blockages in arteries in your heart and other parts of your body. LDL cholesterol raises your risk for heart disease.
You'll find saturated fat in foods like these:
- Red meat like beef, lamb, and pork
- Skin-on chicken and other poultry
- Whole-milk dairy products like milk, cheese, and ice cream
- Palm and coconut oils
There’s some debate in the medical community over saturated fats. Some studies have found no evidence that these fats directly contribute to heart disease. And some types of saturated fat, like those in milk, might be better for you than others, such as red meat.
In general, the American Heart Association recommends that you get no more than 5% or 6% of your daily calories from saturated fat. So if you eat 2,000 calories a day, limit saturated fat to 120 of those calories or 13 grams of saturated fat per day.
What you use in your diet instead of saturated fat also matters. For example, eating polyunsaturated fat instead of saturated fat might lower your heart disease risk. But replacing saturated fats with carbohydrates might raise your heart disease risk.
Unsaturated fats come mainly from vegetables, nuts, and fish. They're liquid at room temperature. Because these fats are good for your heart and the rest of your body, experts recommend that you eat them in place of saturated and trans fats.
Unsaturated fats come in two forms:
Monounsaturated fats have one unsaturated chemical bond. Oils that have these fats are liquid at room temperature, but they turn solid when you refrigerate them.
You'll find monounsaturated fats in foods like:
- Olive, canola, and peanut oils
- Almonds, hazelnuts, pecans, and other nuts
Polyunsaturated fats have many unsaturated chemical bonds. Polyunsaturated oils stay liquid at room temperature and in the refrigerator.
You'll find polyunsaturated fat in foods like:
There are two types of polyunsaturated fats: omega-3 and omega-6 fatty acids.
Omega-3 fatty acids come in three forms:
- Eicosapentaenoic acid (EPA), found mainly in fish
- Docosahexaenoic acid (DHA), also found mainly in fish
- Alpha-linolenic acid (ALA) from plant sources like flaxseed, vegetable oils, and nuts
Studies show that eating fish high in omega-3 fatty acids lowers your risk of cardiovascular disease. Yet taking omega-3 supplements may not have the same benefit. Researchers are also looking at whether omega-3s might help prevent or slow Alzheimer's disease and other forms of dementia.
You need to get these essential fats from food because your body doesn't make them. To get enough omega-3 fatty acids in your diet, eat fish like salmon, mackerel, and herring at least two times a week.
Omega-6 fatty acids are found in foods like leafy green vegetables, seeds, nuts, and vegetable oils. Doctors used to think that omega-6 fatty acids contributed to heart disease. Now, evidence suggests that these fatty acids are actually good for your heart.
The American Heart Association recommends that you get 5% to 10% of your daily calories from omega-6 fatty acids. Most people already get this amount in their diet.
Small amounts of trans fats happen naturally in animal-based foods like meat and milk. But most trans fats are made in an industrial process. Companies add hydrogen to liquid vegetable oils to make them solid at room temperature, so foods last longer. It also gives them a satisfying taste and texture.
You may find trans fats in these foods:
- French fries and other fried foods
- Cakes, pies, biscuits, cookies, crackers, doughnuts, and other baked goods
- Stick or tub margarines
- Microwave popcorn
- Frozen pizza
Trans fat might taste good, but it's not good for you. This unhealthy type of fat raises your LDL cholesterol level, making you more likely to have heart disease, stroke, and type 2 diabetes. It also lowers "good" HDL cholesterol. The American Heart Association recommends that you get no more than 1% of your daily calories from trans fats. Some places have banned trans fats altogether.
Are trans fat-free foods healthy foods?
Not always. Some trans fat-free foods might still have a lot of unhealthy saturated fat in them. They might contain lots of sugar and salt that aren’t good for you, either. Read labels carefully before eating packaged or processed foods.
The bottom line: To keep your heart -- and the rest of you -- healthy, get most of your fats from unsaturated sources. And get the bulk of your nutrition from healthy, low-fat foods like vegetables, fruits, whole grains, and lean protein such as fish and skinless poultry.