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Choosing Healthy Fats

Good Fats, Bad Fats, and the Power of Omega-3s

Salmon with lemon

For years we’ve been told that eating fat will add inches to your waistline, raise cholesterol, and cause a myriad of health problems. But now we know that not all fat is the same. While bad fats can wreck your diet and increase your risk of certain diseases, good fats can protect your brain and heart. In fact, healthy fats—such as omega-3s—are vital to your physical and emotional health. By understanding the difference between good and bad fats and how to include more healthy fat in your diet, you can improve your mood, boost your energy and well-being, and even lose weight.

What are dietary fats?

Fat is a type of nutrient, and just like protein and carbohydrates, your body needs some fat for energy, to absorb vitamins, and to protect your heart and brain health. Despite what you may have been told, fat isn’t always the bad guy in the health and waistline wars. “Bad” fats, such as artificial trans fats and saturated fats, are guilty of the unhealthy things all fats have been blamed for—weight gain, clogged arteries, and so forth. But “good” fats such as unsaturated fats and omega-3s have the opposite effect. In fact, healthy fats play a huge role in helping you manage your moods, stay on top of your mental game, fight fatigue, and even control your weight.

Dietary fat and cholesterol

Dietary fat also plays a major role in your cholesterol levels. Cholesterol is a fatty, wax-like substance that your body needs to function properly. In and of itself, cholesterol isn’t bad. But when you get too much of it, it can have a negative impact on your health. As with dietary fat, there are good and bad types of cholesterol.

  • HDL cholesterol is the "good" kind of cholesterol found in your blood.
  • LDL cholesterol is the "bad” kind.
  • The key is to keep LDL levels low and HDL high, which may protect against heart disease and stroke.
  • Conversely, high levels of LDL cholesterol can clog arteries and low HDL can be a marker for increased cardiovascular risk.

Rather than the amount of cholesterol you eat, the biggest influence on your cholesterol levels is the type of fats you consume. So instead of counting cholesterol, it’s important to focus on replacing bad fats with good fats.

Good fats vs. bad fats

Since fat is an important part of a healthy diet, rather than adopting a low-fat diet, it’s more important to focus on eating more beneficial “good” fats and limiting harmful “bad” fats.

Healthy or “good” fats

Monounsaturated fats and polyunsaturated fats are known as the “good fats” because they are good for your heart, your cholesterol, and your overall health. These fats can help to:

  • Lower the risk of heart disease and stroke.
  • Lower bad LDL cholesterol levels, while increasing good HDL.
  • Prevent abnormal heart rhythms.
  • Lower triglycerides associated with heart disease and fight inflammation.
  • Lower blood pressure.
  • Prevent atherosclerosis (hardening and narrowing of the arteries).
Healthy Fats
Type Good sources

Monounsaturated fat

  • Olive, canola, peanut, and sesame oils
  • Avocados
  • Olives
  • Nuts (almonds, peanuts, macadamia, hazelnuts, pecans, cashews)
  • Peanut butter

Polyunsaturated fat

  • Sunflower, sesame, and pumpkin seeds
  • Flaxseed
  • Walnuts
  • Fatty fish (salmon, tuna, mackerel, herring, trout, sardines) and fish oil
  • Soybean and safflower oil
  • Soymilk
  • Tofu

Unhealthy or “bad” fats

Trans fat. Small amounts of naturally occurring trans fats can be found in meat and dairy products but it’s artificial trans fats that are considered dangerous. This is the worst type of fat since it not only raises bad LDL cholesterol but also lower good HDL levels. Artificial trans fats can also create inflammation, which is linked to heart disease, stroke, and other chronic conditions and contributes to insulin resistance, which increases the risk of developing Type 2 diabetes.

  • In the U.S., the FDA is making inroads into outlawing the use of artificial trans-fats in commercially prepared food, but it’s still important to carefully read food labels.
  • No amount of artificial trans fat is considered safe so aim to eliminate it from your diet.

Saturated fat. While not as harmful as trans fat, saturated fat can raise bad LDL cholesterol and too much can negatively impact heart health, so it’s best consumed in moderation. While there’s no need to cut out all saturated fat from your diet, most nutrition experts recommend limiting saturated fat to 10% of your daily calories.

Unhealthy Fats
Type Primary sources

Trans fat

  • Commercially-baked pastries, cookies, doughnuts, muffins, cakes, pizza dough
  • Packaged snack foods (crackers, microwave popcorn, chips)
  • Stick margarine, vegetable shortening
  • Fried foods (French fries, fried chicken, chicken nuggets, breaded fish)
  • Anything contained hydrogenated vegetable oil, even if it claims to be “trans fat-free”

Saturated fat

  • Red meat (beef, lamb, pork)
  • Chicken skin
  • Whole-fat dairy products (milk, cream, cheese)
  • Butter
  • Ice cream
  • Lard
  • Tropical oils such as coconut and palm oil

But I’ve read that saturated fat is no longer considered unhealthy…

For decades, doctors, nutritionists and health authorities have told us that a diet high in saturated fats raises blood cholesterol and increases the risk of heart disease and stroke. However, recent studies have made headlines by casting doubt on those claims, concluding that people who eat lots of saturated fat do not experience more cardiovascular disease than those who eat less.

So does that mean it’s OK to eat as much saturated fat as you want?

What these studies highlight is that when cutting down on saturated fats in your diet, it’s important to replace them with the right foods. For example, swapping animal fats for vegetable oils—such as replacing butter with olive oil—can help to lower cholesterol and reduce your risk for disease. However, swapping animal fats for refined carbohydrates, such as replacing your breakfast bacon with a bagel or pastry, won’t have the same benefits. That’s because eating refined carbohydrates or sugary foods can also have a negative effect on cholesterol levels, your risk for heart disease, and your weight.

Limiting your intake of saturated fats can still help improve your health—as long as you take care to replace it with good fat rather than refined carbohydrates. In other words, don’t go no fat, go good fat.

The power of omega-3s

Omega-3 fatty acids are a type of polyunsaturated fat and are especially beneficial to your health. There are different types of omega-3s: EPA and DHA are found in fish and algae and have the most health benefits, while ALA comes from plants and is a less potent form of omega-3, although the body does convert ALA to EPA and DHA at low rates.

Research has shown that a diet rich in omega-3s may help to:

  • Prevent and reduce symptoms of depression, ADHD, and bipolar disorder
  • Protect against memory loss and dementia
  • Reduce the risk of heart disease, stroke, and cancer
  • Ease arthritis, joint pain, and inflammatory skin conditions
  • Support a healthy pregnancy
  • Help you battle fatigue, sharpen your memory, and balance your mood
The Best Sources of Omega-3s
Fish: the best source of omega-3 (high in EPA and DHA)
  • Anchovies
  • Herring
  • Salmon
  • Mackerel
  • Sardines
  • Trout
  • Tuna
  • Mussels
  • Oysters
  • Halibut
Vegetarian sources of omega-3s (high in ALA)
  • Algae such as seaweed (high in EPA and DHA)
  • Eggs (small amounts of DHA)
  • Flaxseeds and flaxseed oil
  • Chia seeds
  • Canola and soybean oil
  • Walnuts
  • Mayonnaise
  • Edamame
  • Beans (refried, kidney, etc.)
  • Brussels sprouts
  • Kale
  • Spinach

How much omega-3s do you need?

The American Heart Association (AHA) recommends that people with documented heart disease get about 1 gram of EPA plus DHA per day. For the rest of us, the AHA recommends eating at least two 3.5-ounce servings of fish per week.

  • Fatty fish like salmon, mackerel, herring, lake trout, sardines and albacore tuna are highest in omega-3 fatty acids.
  • If you don’t care for fish or you want to be sure to get your daily omega-3s, you may want to take an omega-3 supplement, widely available over the counter.
  • Include a variety of ALA-rich oils, nuts, seeds, and vegetables in your diet.

What to do about mercury in fish

Despite the health benefits, nearly all seafood contains traces of pollutants, including the toxic metal mercury. The concentration of pollutants increases in larger fish, so avoid eating shark, swordfish, tilefish, and king mackerel.

Most adults can safely eat 12 ounces (two 6-ounce servings) of cooked seafood a week. For women who are pregnant, nursing mothers, and children under 12, choose fish lower in mercury, such as shrimp, canned light tuna, salmon, pollock, or catfish. You can also protect yourself by varying the types of fish that you eat.

Omega-3 supplements

While omega-3s are best obtained through food, there are many omega-3 and fish oil supplements available. Although the contents of supplements aren’t directly regulated by the FDA, several studies have shown that the commonly available brands in reputable stores contain the stated ingredients. Fish oil contains no mercury (mercury binds to protein, not fat) and very low amounts of other contaminants.

  • One capsule a day usually supplies about 200 to 400 mg of EPA plus DHA, and should be enough for most people.
  • If you need to substantially lower your triglycerides, your doctor may recommend prescription fish oil, which has been concentrated to contain about 900 mg of EPA plus DHA per capsule.
  • For strict vegetarians or vegans, as well as obtaining ALA from food sources, look for capsules containing DHA and EPA extracted from algae, the original source of omega-3s for fish.

Tips for taking supplements

For some, fish oil capsules can be hard to swallow and may leave a fishy aftertaste after burping. Keeping the capsules in the freezer before taking them can help or try odorless or deodorized capsules.

Choosing healthy oils

Vegetable oils lower LDL cholesterol and triglycerides, and raise HDL cholesterol. Vegetable oils such as corn, sunflower, safflower, and soybean oil contain a type of polyunsaturated fat known as omega-6s that may also reduce insulin resistance and inflammation.

  • Less processed oils, such as cold-pressed extra virgin olive oil, also contain potentially beneficial phytochemicals from the oil seeds.
  • Use naturally occurring unhydrogenated vegetable oils such as olive oil, canola, safflower, sunflower oil most often.
  • If you like olive oil, look for extra virgin olive oil, which likely has extra heart benefits beyond regular olive oil.

What about tropical oils, such as coconut and palm oil?

The food industry likes to tout the benefits of tropical oils, while dietary guidelines shun these oils. Who is right?

These oils have complex effects on blood cholesterol levels—for example, raising “bad” LDL cholesterol but also raising “good” HDL cholesterol. Unfortunately, their effects on other risks for heart disease are not yet clearly known.

  • For now, it’s safer to stick to vegetable oils since there’s stronger evidence that these oils are heart healthy.
  • If you do want to eat something once in a while that contains coconut or palm oil, enjoy it as a treat—it’s better than eating something with trans fat, which these tropical oils often replace.

Tips for adding more healthy fats to your diet

Instead of obsessively counting fat grams, aim for a diet rich in a variety of vegetables, fruit, nuts, and beans, with two or more weekly servings of fatty fish, moderate amounts of dairy (reduced-fat), small amounts of red meat, and only occasional fried or processed meals.

This might mean replacing fried chicken with fresh fish, swapping out some of the red meat you eat with other sources of protein such as fish, chicken, or beans, or using olive oil rather than butter. Following a Mediterranean diet can also help ensure you’re getting enough good fats in your diet and limiting the bad ones.

  • Try to eliminate trans fats from your diet. Check food labels for trans fats. Limiting commercially-baked goods and fast food can go a long way.
  • Limit your intake of saturated fats by replacing some of the red meat you eat with beans, nuts, poultry, and fish, and switching from whole milk dairy to lower fat versions. But don’t make the mistake of replacing saturated fat with refined carbohydrates and sugary foods.
  • Eat omega-3 fats every day. Include a variety of fish sources as well as plant sources such as walnuts, ground flax seeds, flaxseed oil, canola oil, and soybean oil.
  • Cook with olive oil.Use olive oil for stovetop cooking rather than butter, stick margarine, or lard. For baking, try canola oil.
  • Eat more avocados. Try them in sandwiches or salads or make guacamole. Along with being loaded with heart- and brain-healthy fats, they make for a filling meal.
  • Reach for the nuts. You can add nuts to vegetable dishes, use them instead of breadcrumbs on chicken or fish, or make your own trail mix with nuts, seeds, and dried fruit.
  • Snack on olives. Olives are high in healthy monounsaturated fats and make for a low-calorie snack. Try them plain or make a tapenade for dipping.
  • Dress your own salad. Commercial salad dressings are often high in unhealthy fat or added sugars. Create your own healthy dressings with olive, flaxseed, or sesame oils.

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Resources and references

General information on dietary fats

Healthy Eating for a Healthy Heart - Information on the different kinds of fats and their affect on cholesterol (Harvard University, School of Public Health)

Healthy Fats – Explains the different types of fats and how much of them should be included in a healthy diet. (University of Michigan)

Saturated Fats – Outlines the long-held view that saturated fats raise cholesterol and increase the risk of heart disease and stroke. (American Heart Association)

Fats – Differentiates between healthy fats and unhealthy fats, including saturated fat, which should be limited for people with diabetes to prevent heart disease and stroke. (American Diabetes Association)

Fats and cholesterol

Fats and Cholesterol – Information on the different kinds of fats and their effect on cholesterol (Harvard University, School of Public Health)

Omega-3s

Omega-3 fatty acids – Comprehensive article on omega-3 fatty acids and the role they may play in preventing several diseases and conditions. (University of Maryland Medical Center)

Fats: dietary guidelines

Dietary Guidelines for Americans – Summary of dietary guidelines, including recommended saturated fat limits. (USDA)

Authors: Robert Segal, M.A. and Lawrence Robinson. Last updated: October 2017.