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Medical Author:

Betty Kovacs, MS, RD

Betty Kovacs, MS, RD

Betty is a Registered Dietitian who earned her B.S. degree in Food and Nutrition from Marymount College of Fordham University and her M.S. degree in Clinical Nutrition from New York University. She is the Co-Director and Director of nutrition for the New York Obesity Research Center Weight Loss Program.

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Medical Editor:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Fats

Dietary fat does not equal body fat. There is a huge misconception that fat in the diet will always lead to weight gain. As mentioned previously, excess calories are responsible for weight gain, not any one nutrient. Dietary fat is essential for our health and should be a part of everyone's diet.

Dietary fat is required for

• energy: Fat is the most concentrated source of calories in the diet, providing 9 calories per gram compared with 4 calories per gram from either carbohydrates or protein;



• transport of fat-soluble vitamins: A, D, E, and K and carotenoids;



• maintenance of healthy skin;



• regulation of cholesterol metabolism; and



• precursor of prostaglandins (hormone-like substances that regulate many body functions).

Fat is composed of the same three elements as carbohydrates: carbon, hydrogen, and oxygen. The fat that we consume is primarily in the source of triglycerides. This means that there are three fatty acids combined with a glycerol backbone. These fatty acids are

• monounsaturated: olive oil, olives, peanut oil, canola oil, avocado, and nuts;



• polyunsaturated: safflower oil, sunflower oil, corn oil, fish, flaxseeds, and walnuts; and



• saturated: butter, lard, red meat, poultry skin, whole milk, coconut oil, and palm oil.

Each triglyceride will have varying levels of each one of these fatty acids. The ones that have a higher percentage of monounsaturated and polyunsaturated fats are considered the healthiest sources. Some examples are

• olive oil: 15% saturated fat, 10% polyunsaturated fat, and 75% monounsaturated fat;



• lard: 43% saturated fat, 10% polyunsaturated fat, and 47% monounsaturated fat; and



• flaxseed oil: 9% saturated fat, 73% polyunsaturated fat, and 18% monounsaturated fat.

Along with these fatty acids, there are also trans fats and cholesterol in your diet. Trans fat can be found in some margarines, vegetable shortenings, cookies, crackers, snack foods, and other foods made with or fried in partially hydrogenated oils. Unlike other fats, the majority of trans fat is formed when food manufacturers turn liquid oils into solid fats. A small amount of trans fat is found naturally, primarily in some animal-based foods.

Trans fat has been found to be the most dangerous for our health. It's so dangerous that the guidelines are not to consume any in your diet. Recently, trans fat has been added to the food labels so that you can now determine if there is any present in the food. The one limitation is that you will only see foods with over 0.5 grams of trans fat per serving list any trans fat on their label. This means that if the serving size is two cookies and there is .4 grams of trans fat in two cookies, the trans fat content will be listed as 0 grams. However, if you eat eight cookies, you will actually be consuming 1.6 grams of trans fat. The way to determine if there is any trans fat present is to read the list of ingredients and look for hydrogenated or partially hydrogenated oil.

The cholesterol in your blood comes from your liver and your diet. The dietary sources are animal foods like meat, poultry, fish, and dairy products. The reason our livers produce cholesterol is because our body needs it. Cholesterol is used for producing cell membranes and some hormones, and serves other needed bodily functions.

The effects that dietary fat has on your blood cholesterol levels will help you choose which ones to consume. According to the American Heart Association, LDL (low-density lipoprotein) is the "bad" cholesterol because when too much of it circulates in the blood, it can slowly build up in the walls of the arteries that feed the heart and brain. HDL (high-density lipoprotein) is the "good" cholesterol because it helps remove "bad" cholesterol from arteries and prevent blockage. The goal is to have a

• total blood cholesterol less than 200 mg/dL;



• LDL less than 100 mg/dL; and



• HDL greater than 40 mg/dL for men and 50 mg/dL for women.

The effect that your diet has on each of these is

• saturated fat increases total cholesterol and LDL levels: the goal is for this to be less than 7% of your fat;



• trans fat increases total cholesterol and LDL levels and lowers HDL levels; and



• cholesterol over 300 mg/day can raise total cholesterol and LDL levels.

While these fats can harm your health, there are fats that are essential for optimal health. The essential fatty acids are the polyunsaturated fats omega-3 and omega-6 fatty acids. You need to consume these because your body cannot produce them. We need an equal amount of each of these fats. The typical American diet has an abundance of omega-6 fatty acids with a limited amount of omega-3 fatty acids. On average, Americans consume 11 to 30 times more omega-6 fatty acids than omega-3 fatty acids. Research has shown that omega-3 fatty acids can reduce blood triglyceride levels, reduce blood pressure, improve morning stiffness and joint tenderness in rheumatoid arthritis, protect the heart in people who have had a heart attack, decrease the risk of stroke, reduce the risk of atherosclerosis, and possibly have an impact on depression. The dietary sources of omega-3 fatty acids are mackerel, lake trout, herring, sardines, albacore tuna, and salmon.

The following are Dietary Guidelines for fat:

• Consume less than 10% of calories from saturated fatty acids and less than 300 mg/day of cholesterol, and keep trans fatty acid consumption as low as possible.



• Keep total fat intake between 20%-35% of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.



• When selecting and preparing meat, poultry, dry beans, and milk or milk products, make choices that are lean, low-fat, or fat-free.



• Limit intake of fats and oils high in saturated and/or trans fatty acids, and choose products low in such fats and oils.

The following are Dietary Reference Intakes for fat consumption:

• Adults should get 20%-35% of their calories from fat.



• Infants and younger children should get 25%-40% of calories from fat.



• The report doesn't set maximum levels for saturated fat, cholesterol, or trans fatty acids, as increased risk exists at levels above zero; however, the recommendation is to eat as little as possible while consuming a diet adequate in important other essential nutrients.



• Recommendations are made for linoleic acid (an omega-6 fatty acid) and for alpha-linoleic acid (an omega-3 fatty acid).

Dietary fat is a necessary nutrient in our diet. Many people have turned to fat-free products, assuming that they are healthier, but this is not always the case. Fat-free products are often high in sugar. You may find that you actually need to increase the amount of fat that you consume. You will need to cut back on another nutrient to avoid going above your calorie needs. It is also important to focus on the kinds of fat that you are consuming. Making the change from consumption of saturated and trans fat to monounsaturated and polyunsaturated fats is lifesaving.