Ask an expert: Fat facts

Q: First, fat was bad. Then some fat was good and some was bad. Now we’ve got trans fats to worry about. It’s getting so complicated! Please explain the differences between fats and what I need to know about them.

Answer provided by Terese Scollard, MBA, RD, LD, regional clinical nutrition manager for Providence Nutrition Services, and Diane Reiner, RN, quality coordinator for Providence Heart and Vascular Institute:

We're learning more and more about fats and the roles they play in health. Too much fat, or the wrong kind of fat, can increase your risk of heart disease, high blood cholesterol, diabetes and some cancers. Here are some facts about fats – the good, the bad, and the ugly.

The bad guys: saturated fat
Let's start with the bad guys. Saturated fat and trans fat – along with dietary cholesterol – raise the level of LDL “bad” cholesterol in the blood. High LDL is not good. According to the National Institutes of Health, “The higher the LDL cholesterol, the greater the risk for coronary heart disease, the main form of heart disease and a leading cause of death, illness and disability in the United States.”

Saturated fats are typically solid at room temperature. The main sources are animal products such as fatty meat, chicken skin, butter and full-fat dairy products (cream, milk, cheese and some yogurt).

The Dietary Guidelines for Americans, 2015  recommends that healthy Americans consume less than ten percent of their total calories from saturated fats. Adults with high LDL levels are urged to cut saturated fats even more, to less than seven percent of total calories.

Lowering the amount of saturated fat in your diet will help lower your cholesterol level and improve your cardiovascular health. You’ll find some great pointers and recipes in the Northwest Guide to Heart-Healthy Living, produced by Providence Heart and Vascular Institute.

The truly ugly: trans fat
Trans fat is even nastier than saturated fat. It significantly raises LDL cholesterol – much more markedly than saturated fat does – and it lowers HDL cholesterol, the good cholesterol that helps prevent LDL cholesterol from building up in arteries.

Trans fats are created when companies add hydrogen to vegetable oil – a process called hydrogenation. Hydrogenation turns vegetable oil into a semi-solid (it's the difference between natural peanut butter that must be stirred and peanut butter that is uniformly creamy). Partially hydrogenated oils keep cakes tender and crackers crisp, give shape to stick margarine, and extend the shelf life of baked products. We are learning, however, that this process does nothing to extend the lives of people who consume these products.

A report from top nutritionists at the Harvard School of Public Health stated: “By our most conservative estimate, replacement of partially hydrogenated fat in the U.S. diet with natural unhydrogenated vegetable oils would prevent approximately 30,000 premature coronary deaths per year, and epidemiologic evidence suggests this number is closer to 100,000 premature deaths annually.” 

The Danish government effectively banned partially hydrogenated oils after a report of the Danish Nutrition Council stated: “The results [of four population studies] suggest that the intake of trans fatty acids compared to saturated fatty acids per gram is associated with a 10-fold higher risk increment for the development of coronary heart disease.” 

The new Dietary Guidelines for Americans recommend minimizing trans fat in your diet by avoiding, or at least strictly limiting, processed foods that contain this harmful fat. A small amount of trans fat exists naturally in some animal products, but these are not the problem. The big problem is commercially baked goods and processed fats.

About 80 percent of the trans fat in Americans' diets come from processed and restaurant foods. The main culprits: crackers, cookies, deep-fried chicken and fish, margarine, bread, pie crust, donuts, French fries, potato chips and corn chips.

Most shortening and margarine also is high in trans fat. (A noteworthy exception is margarine enriched with plant sterols, which block the absorption of cholesterol and can help lower LDL cholesterol by about ten percent.

Tommy Thompson, the former secretary of Health and Human Services, has suggested that the FDA may recommend limiting trans fat to less than two grams a day.

Look for trans fat on the label
Thanks to new labeling regulations that took effect in 2006, trans fat content is now included on every Nutrition Facts label – you’ll find it on the line below saturated fat.

There is one caveat, however: Manufacturers are allowed to list trans fat content as zero as long as the actual content is half a gram or less per serving. If you eat several servings of foods with half a gram of trans fat each, you could quickly consume more than two grams a day. If you want to avoid even small amounts of trans fat, check the ingredients list. If the words “partially hydrogenated” or “shortening” appear among the ingredients, the product contains trans fat. 

In restaurants, where there are no food labels, beware of deep-fried foods, which are common sources of trans fats. Some restaurants have switched to trans-fat-free oils in their fryers, but these oils are still very high in total fat and calories. Limit your consumption of fried foods in general, and don't order them at all in restaurants that haven't made the switch to healthier oils.

The good fats: monounsaturated and polyunsaturated fats
By replacing the saturated fats in their current diet with monounsaturated and polyunsaturated fats, most people can nudge down their LDL cholesterol level.

The Dietary Guidelines recommend keeping total fat intake moderate: 20 to 35 percent of total calories for healthy adults, 25 to 35 percent of total calories for children ages 4 to 18, and 30 to 35 percent for children ages 2 to 3 years. (The recommendation for people with high triglycerides or diabetes, however, typically is not less than 25 percent.)

Polyunsaturated fat
Polyunsaturated fats include safflower, corn, sunflower, soy and cottonseed oils and certain fish oils.

Omega-3 fatty acids are an especially heart-friendly type of polyunsaturated fat. Salmon, albacore tuna, sardines and herring are among the fish rich in omega-3s. Canola oil, soybeans, English walnuts and flaxseed also contain omega-3s in smaller amounts. Read the American Heart Association's recommendations regarding omega-3 fatty acids.

Studies show that omega-3s pack quite a punch. They decrease the likelihood of blood clot formation (thus decreasing the chances of heart attack), lower blood pressure, help reduce blood triglyceride levels, inhibit the growth of arterial plaque, reduce the risk of arterial inflammation, and protect against arrhythmias – the irregular heartbeats that can cause sudden cardiac death.

Replacing saturated fats with omega-3s is a particularly effective way to lower LDL cholesterol levels. That can be as simple as choosing baked salmon off the menu instead of steak with blue cheese; using canola or soy oil in place of butter or shortening when baking cookies; and adding tofu instead of chicken to a stir fry.

Monounsaturated fat
Monounsaturated fats offer the added benefit of protecting the artery walls against inflammation and other damage.

Olive, peanut and canola oils and avocados are high in monounsaturated fats. Most seeds and nuts – including Oregon's own hazelnuts – are high in poly- or monounsaturated fats and full of nutrients and protein. (Brazil nuts, with 23 percent of their fat as saturated, are an exception.)

Use canola, olive and peanut oils in place of highly saturated fats. Canola oil, for example, has only one gram of saturated fat per tablespoon; olive oil has two; and butter has seven. Some context: A healthy intake of saturated fat is 10-15 grams per day. Visualize a small paper clip. It weighs one gram.

The bottom line
All fats pack a double-dose of calories, so overdoing a good fat can still crank up your weight beyond what's best. You may feel virtuous dipping bread in olive oil instead of smearing it with butter, but bread can sop up a whole lot of olive oil – and at 120 calories per tablespoon, you can see where that's heading.

Bottom line: Avoid trans fats and saturated fats as much as possible; substitute mono- and polyunsaturated fats (especially omega-3s) for those unhealthy fats; and keep total fat intake at modest levels.