Which fats are good fats?

The healthiest oils are olive, sunflower, safflower, peanut and canola.

Polyunsaturated fatty acids lower the production of total blood cholesterol as well as HDL (good) and LDL (bad) cholesterols. Main food sources are corn, safflower, soybean, sesame and sunflower oils.

Monounsaturated fatty acids lower the production of total blood cholesterol and LDL (bad) cholesterol. However, they raise the production of HDL (good) cholesterol. Main food sources are canola, nut and olive oils.

Omega-3 fatty acids (EPA and DHA) may help reduce blood clot- ting and prevent hardening of the arteries. Main food sources are various types of seafood -- especially fatty fish, such as albacore tuna, mackerel and salmon. Walnuts as well as soy, canola and flaxseed oil provide alpha-linoleic acid, which the body converts to omega-3s.

We forget that fat is a nutrient just like carbohydrates and protein. Even though fat has a bad reputation, it has important functions such as: protecting out body organs, producing hormones and a body reservoir for energy. As a registered dietitian, my recommendation is consuming 30 percent of your diet with healthy fats including olive, canola and peanut oil, avocado and nuts.

The Dietary Guidelines for Americans recommend the majority of dietary fat come from two sources: monounsaturated and polyunsaturated fat, which are mostly derived from oils in plants. Common examples of monounsaturated fats are canola, olive and peanut oils. Sources of polyunsaturated fats include corn and soybean oils as well as many seeds, nuts and their oils.

You've probably heard about good fats, those that are needed by the body to maintain healthy cells and brain function. Essential omega-3 and omega-9 fatty acids are crucial for the prevention of heart disease, arthritis, joint problems and immune system weakness. Good sources include salmon and other ocean fish, almonds, walnuts, avocados, ground flaxseeds, olive oil and fish oil supplements (with EPA/DHA). Heart-healthy, plant-derived fats do not have to be cut from your meal plan entirely, including monounsaturated oils such as olive or canola oils. Fat is not your ultimate enemy despite what we've been brainwashed to believe over the years. So don't eliminate fat entirely, because it helps to keep you satisfied and makes food taste better. Just use it sparingly and wisely and you won't feel as deprived because the food you eat tastes good!

These are the major types of fat found in food: saturated, trans, polyunsaturated, and monounsaturated. Monounsaturated fats should make up most of the fat you consume since this type of fat may help lower your "bad" LDL cholesterol and triglycerides. Good sources of monounsaturated fats include olive and canola oils, olives, avocados, nuts and nut products.

Polyunsaturated fat is also preferred over saturated fat, but with some considerations. It lowers LDLs but may also lower HDLs, your "good" cholesterol. Omega-3 fatty acids are a healthy type of polyunsaturated fat that have been linked to additional health benefits. Omega-3 fatty acids are found in some fatty fish, including salmon, tuna, herring, bluefish and mackerel.

Saturated fat is the type of fat to avoid the most since it can raise LDL blood cholesterol levels, which can increase the risk of heart disease. It is found in meats and milk products, which is why Weight Watchers recommends eating reasonable portions of lean meats and low-fat milk products.

Trans fatty acids (also called trans fat) are also a concern because they raise LDL cholesterol and lower HDL cholesterol. Trans fatty acids are formed during a manufacturing process called hydrogenation. This turns liquid oils into a more solid fat. The bulk of trans fat in the American diet comes from processed foods, such as crackers, baked goods, and margarine.

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Polyunsaturated and monounsaturated (both called unsaturated fatty acids) are fats you should be including in your diet because they are linked to disease prevention. Monounsaturated fats are healthiest, so aim to get the most of these, while polyunsaturated fats are next in line.

Monounsaturated fatty acids are considered healthy because they don't raise low-density lipoprotein (LDL—the "bad" cholesterol that contributes to clogged arteries and heart disease) and they do raise high-density lipoprotein (HDL—the "good" form that actually removes cholesterol from your body). Plus, they've been linked to greater insulin sensitivity. Nearly all the monounsaturated fat in our diet comes from oleic acid.

Polyunsaturated fatty acids, which fall into the healthy fat category because they do not raise LDL, include two types: Omega-3 fatty acids and Omega-6 fatty acids. Omega-3 fats, found in fish oil and in some plant foods, like walnuts and flaxseed, have been linked to prevention of type 2 diabetes.

Good fats include:

• Monounsaturated fats. They come in two forms—omega-3 fatty acids and omega-6 fatty acids, in the form of fish (3s) and nut oils (3s and 6s). The omega-3's have been shown to improve arterial and brain function. They're found in olive oil, canola oil, fish oils, flaxseeds, avocados and nuts (especially walnuts). They've also been shown to reduce blood pressure and lipid levels when used in place of carbohydrates. Bottom line: make about 30 to 40 percent of your fats the monounsaturated variety.
• Polyunsaturated fats. These are like monounsaturated except they contain more than one unsaturated bond. They are usually present in vegetable oils and sesame oils. The may improve arterial and brain function, and will help keep up your satiety levels. Bottom line: make 20 to 40 percent of your fats polyunsaturated.

Good fats are mono and poly unsaturated fatty acids. These fats are liquid at room temperature and make up healthy cells. Mono and poly unsaturated fats decrease unhealthy LDL cholesterol when substituted for saturated fats found in high fat animal products and packaged snack foods and increase healthy HDL cholesterol. Some healthy fats are soybean oil, flaxseed oil, olive oil, canola oil, nuts, seeds, avocados, walnuts and fish oil.

An example of a good fat is extra virgin olive oil, which has been shown to reduce heart attacks, reduce diabetes and help with weight loss. Other type of good fat is monounsaturated fats. Sources of this good fat are:

• Avocados
• Nuts like almonds, walnuts, pecans (not peanuts) and macadamia nuts
• Seeds like pumpkin, sesame, chia and hemp

All of these items are full of great fats that should be a regular part of your diet. In fact, you should probably have five or six servings of these good fats every day.

There is another type of fat that is also possibly good, but there is a lot of controversy surrounding it. It is saturated fats. We've been taught this type is bad, but I believe it is actually a great part of a healthy diet.

Fats are not the dieter's enemy! Say yes to these good fats:

Monounsaturated fat is good fat. It comes from oils that are liquid at room temperature, or better still, plant foods (avocados, nuts, peanut oil, canola oil, tahini, olives, fish). Research suggests that these fats may actually reduce your LDL (bad) cholesterol level without lowering the HDL (good) cholesterol, helping to reduce your risk of cardiovascular disease.

Omega-3 fats are found in fatty fish (anchovy, mackerel, salmon, sardines, shad and tuna), flaxseed and nuts. Studies show that omega-3 fats reduce the risk of blood clots and abnormal heart rhythms and improve blood cholesterol and triglycerides. Another type of omega-3 fatty acid is alpha-linolenic acid, which is found in flaxseeds, canola oil, soybean oil, walnuts and dark green leafy vegetables.

Polyunsaturated fat comes from oils that are liquid or soft at room temperature, including corn, safflower, sesame, soybean and sunflower oils. While polyunsaturated fat lowers LDL or "bad" cholesterol, it also lowers your HDL or "good" cholesterol, which you want to move up. (Caution note: there are some findings indicating that a diet high in polyunsaturated vegetable oils encourages the synthesis of pro-inflammatory prostaglandins, the group of hormones that intensify the inflammatory response. That’s why choosing more omega-3 fatty acids (salmon, sardines, walnuts, flax seeds or oil and soy foods), which increase the production of inhibitory prostaglandins, is important in your daily diet.)

Not all dietary fats are bad, but it can be confusing to keep them all straight. Saturated fats and trans fats are the fats that raise your cholesterol. Animal products, such as fatty beef and whole fat dairy, tend to be high in saturated fat. Margarine and baked goods may also be high in saturated fat; they used to also contain trans fat (sometimes called partially hydrogenated oils), but manufacturers have removed them in many cases (always check nutrition labels). These fats are usually solid at room temperature. Polyunsaturated and monounsaturated fats are healthy fats that contain omega-3 and omega-6 fatty acids. These are found in walnuts, almonds, olive oil and canola oil. These "good" fats can help reduce levels of LDL or "bad" cholesterol in your blood.

Saturated fats, so-called because they are “saturated” with hydrogen atoms, raise cholesterol levels and are found in animal products like meat, butter and cheese. Yet there are some exceptions: Coconut oil, for instance, although technically more saturated than butter, not only doesn’t raise LDL (bad cholesterol) levels, but may also actually help to increase HDL (good cholesterol).

Many medical experts believe that trans fats have even stronger adverse effects than saturated fats. Typically found in processed, fried and fast food, trans fats are primarily produced through hydrogenation—a process that turns liquid vegetable oils into solids, such as the shortening and margarine often used in baked goods and snack foods. Trans fats are thought to increase insulin resistance and thus raise the risk of developing type 2 diabetes. They also raise levels of LDL and lower HDL levels. In fact, their effects are so pernicious that replacing just 2 percent of calories from trans fats with calories from unsaturated fats (for instance, using canola or olive oil instead of hydrogenated or partially hydrogenated vegetable oil) is associated with an astonishing 53 percent lower risk of coronary heart disease, according to a report from Harvard’s ongoing Nurses’ Health Study.

What’s remained somewhat murky, until now, is an understanding of the precise mechanism by which trans fats send blood levels of cholesterol and triglycerides soaring. Scientists at the Dana-Farber Cancer Institute discovered that trans fat consumption triggers a biochemical switch in the liver, which “turns on” the genes that push cholesterol production into overdrive. (Unsaturated fats do not activate gene activity to the same degree, which is why they don’t raise cholesterol as saturated and trans fats do.)

Certain fats are more beneficial than others; not all fats were created equal. It is very important to focus on monounsaturated and polyunsaturated fats, including omega-3s and omega-6s. These fats are anti-inflammatory and prevent chronic diseases, and they have been proven to be beneficial for your body.