Fats (Lesson 6)

Sandra May  |  12/19/2009 12:58:19 AM

Introduction and Objectives

Fats are the most concentrated source of food energy, providing 9 calories per gram. Fats are a healthy part of our diet; however, we should be careful about what kinds of fat we eat and the amount of fat we eat.

Recommendations about fat intake have changed. According to the 2010 Dietary Guidelines for Americans, we should consume a diet low in saturated fat, trans fats and cholesterol. Only 20-35 percent of daily calories should come from fat.

Dietary fats are found in both animal and plant foods. All fats have one common characteristic: they are water-insoluble; they don't dissolve in water.

In this lesson, some of the things you will learn include:

  • Different types of fat and their effect on health.
  • How much fat is recommended as part of a healthy diet.
  • Food sources of fat.
  • How to identify foods that lower the LDL cholesterol.
  • How to decrease the total amount of saturated fat, trans fat and cholesterol in your diet.

Facts about Fats

Fats can be saturated and unsaturated. Saturated fats are solid at room temperature. Sources of saturated fats include animal products, palm oil and coconut oil. They raise blood cholesterol more than other forms of fat.

Unsaturated fats can be monounsaturated or polyunsaturated. Unsaturated fats (found in oils) are liquid at room temperature. They become rancid more quickly than saturated fats when exposed to air or heat or over time. Unsaturated fats are found in plants, vegetable oils, fatty fish, nuts and seeds, and soy foods. Olive and canola oils are good sources of monounsaturated fats. Corn, soybean and safflower oils are good sources of polyunsaturated fats.

Trans fats are a type of unsaturated fat. Trans fats can be found in margarine, shortenings, baked or fried goods, dairy products, beef and lamb. Saturated fats have no trans fats. Oils (unsaturated fats) are converted to saturated fats by hydrogenation. Hydrogenation may improve the taste and cooking properties of fats and also increase the shelf life. High intake of trans fatty acids may lead to high blood levels of LDL cholesterol, a risk factor for cardiovascular disease. Therefore, it is recommended that we consume a diet low in saturated fats and trans fats.

Fat is stored in special cells called adipose (fat) cells. Most fat is stored as triglycerides. All triglycerides are made up of the same skeleton: one molecule of glycerol (glucose-like substance) and three fatty acids. Some triglycerides, though, may have only one or two fatty acids. There are several types of fatty acids found in triglycerides. Their structure determines if a fat molecule is saturated or unsaturated.

Some fatty acids cannot be synthesized by the body and need to be obtained from the diet. Those are called essential fatty acids. Omega-3 and omega-6 fatty acids are two types of essential fatty acids. The essential fatty acids are important to maintaining good health. They reduce blood pressure and blood clotting. They also reduce the risk for stroke and heart attack. Good sources of essential fatty acids are:

  • Vegetable oils (canola, soybean, corn and safflower oil)
  • Walnuts
  • Flax seed
  • Fish (tuna, sardines, salmon)

Cholesterol

Cholesterol is a fat-like substance found only in animal products (meats, egg yolks, milk products such as butter and cheese, organ meats, etc.). Not all cholesterol, though, comes from the diet. Our body also produces cholesterol in the liver (about 1,000 milligrams each day). Cholesterol is not used for energy in the body.

There are three types of blood cholesterol:

  1. Low-density lipoprotein or LDL cholesterol
  2. High-density lipoprotein or HDL cholesterol
  3. Very low-density lipoprotein or VLDL cholesterol

Lipoproteins are made up of cholesterol, triglycerides and proteins.

LDL cholesterol is called “bad" cholesterol because a high level of LDL is a risk factor for heart disease. The HDL is called “good" cholesterol, and high levels are heart healthy. An HDL of 60 mg/dL or higher helps protect against heart disease. However, your risk of heart disease, including a heart attack, increases if your HDL cholesterol level is less than 40 mg/dL.

Although it is important for us to get some cholesterol, it is recommended that the total daily cholesterol intake should be fewer than 300 mg/day. People with high levels of LDL should consume less than 200 mg of dietary cholesterol every day. Saturated fats and trans fats also increase blood LDL or "bad" cholesterol. It is recommended that the total blood cholesterol level should be less than 200 mg/dL, and LDL should be 130 mg/dL or less. HDL can be low in people who smoke or are obese (BMI higher than 30) or in postmenopausal women. How can we increase HDL levels? Two good methods are physical activity and losing weight (if overweight). What about LDL? A diet high in soluble fiber may help decrease LDL levels.

VLDL contains the highest amount of triglycerides.  VLDL is considered a type of "bad" cholesterol. Having a high VLDL level means that you may have an increased risk of heart disease, which can lead to a heart attack or stroke.  There is no simple or direct way to measure VLDL cholesterol, which is why it's normally not mentioned during a routine cholesterol screening.  VLDL cholesterol is usually estimated as a percentage of your triglyceride value.  A normal VLDL cholesterol level is between 5 and 40 mg/dL.

Digestion of Fat

We get triglycerides and cholesterol from two sources: from foods we eat and also from the liver. The liver supplies the body with triglycerides and cholesterol.

Excess dietary fat, carbohydrates and protein are stored as fat in the adipose (fat) cells. It is important to think about the amount of fat we need each day and also the recommended number of calories we need.

Roles of Fats

Fats have an important place in our diet. These are a few of the important roles of fats:

  • Give us energy and essential fatty acids.
  • Carry the fat-soluble vitamins.
  • Are part of cell membranes.
  • Are a source of antioxidants.
  • Make us feel full longer.
  • Make foods taste better.
  • Help maintain body temperature (insulation).
  • Protect body organs (insulation).

Fat Labeling

The U.S. Food and Drug Administration (FDA) requires the total amount of fat, saturated fat, trans fat and cholesterol per serving to be listed on the Nutrition Facts label. Also, standard definitions like “fat-free” or “low-fat” have to be used on food labels. Here are some definitions:

  • “Fat-free” (example: fat-free milk) – less than 0.5 g fat per serving.
  • “Low-fat” – 3 g or less of fat per serving.
  • “Low-saturated fat” – 1 g or less of saturated fat and 0.5 g or less of trans fats.
  • “Cholesterol-free” – less than 3 mg cholesterol per serving.
  • “Low-cholesterol” – 20 mg or less per serving.
  • “Healthy” – no more than 60 mg of cholesterol, 3 g of fat and 1 g of saturated fat per serving.
  • “Light” or “lite” – half the fat than in the regular product.
  • “Reduced cholesterol/fat” – 25% less cholesterol or fat than in the regular product.

Where we should look for dietary fats? Sometimes it is easy to identify foods that contain fat. Here are some examples:

  • Butter
  • Margarine
  • Shortening
  • Cooking oils

Other foods may be high in fat, but we may not think of those foods as sources of fat. These are called “invisible fats.” Some examples:

  • Egg yolk
  • Milk (whole milk is higher in fat than 2% or 1% milk)
  • Cheese
  • Meat, fish, chicken (especially the skin), burgers
  • Pies, cakes, cookies, biscuits
  • Nuts, seeds
  • Avocado
  • French fries
  • Chips
  • Crackers

Health Claims

Health claims are statements approved by Food and Drug Administration (FDA) that describe the relationship between certain nutrients and health-related conditions. FDA approves health claims only for products that are not high in fat, saturated fat and cholesterol. There are a couple of FDA-approved health claims related to fat, saturated fat, and cholesterol. This is one example:

“Development of heart disease depends on many factors. Eating a diet low in saturated fat and cholesterol and high in fruits, vegetables and grain products that contain fiber may lower blood cholesterol levels and reduce your risk of heart disease.”



Fat substitutes

Fat substitutes are used to replace the fat in some foods and to reduce calories. Fat substitutes can be carbohydrate-based (oat fiber), protein-based (Simplesse), fat-based (Benefat) or combinations (Olestra). There are more than 60 fat substitutes on the market. Fat substitutes may help lower blood cholesterol levels.

Summary Recommendations for Fat Intake

 

Keep total fat intake between 20% and 35% of calories, with most fats coming from unsaturated fat (fish, nuts and vegetable oils). Cutting back on fat can help you consume fewer calories. Replace saturated and trans fat with unsaturated (polyunsaturated and monounsaturated) fatty acids. Use liquid vegetable oils instead of solid shortening or lard. Replace solid with liquid.

  • Consume a diet with less than 10% calories from saturated fat.
  • Limit cholesterol intake to fewer than 300 mg/day.
  • Consume a diet low in trans fats. Use soft tub margarine instead of stick margarine.
  • Consume at least 8 ounces per week of a variety of seafood. Eat seafood baked or broiled rather than fried.
  • When selecting and preparing meat, poultry, dry beans, and milk and milk products, choose lean, low-fat or fat-free.
  • Eat more vegetables, fruits and whole-grain products instead of cakes, cookies and french fries.

The U.S. Food and Drug Administration (FDA) requires the total amount of fat, saturated fat, trans fat and cholesterol per serving to be listed on the Nutrition Facts label. Also, standard definitions like “fat-free” or “low-fat” have to be used on food labels. Here are some definitions:

  • “Fat-free” (example: fat-free milk) – less than 0.5 g fat per serving.
  • “Low-fat” – 3 g or less of fat per serving.
  • “Low-saturated fat” – 1 g or less of saturated fat and 0.5 g or less of trans fats.
  • “Cholesterol-free” – less than 3 mg cholesterol per serving.
  • “Low-cholesterol” – 20 mg or less per serving.
  • “Healthy” – no more than 60 mg of cholesterol, 3 g of fat and 1 g of saturated fat per serving.
  • “Light” or “lite” – half the fat than in the regular product.
  • “Reduced cholesterol/fat” – 25% less cholesterol or fat than in the regular product.

A food label may contain the claim that the product is "trans fat free" or may show 0 g trans fat on the Nutrition Facts label. By law, the item may still contain up to 0.5 g of trans fat. To be sure that the product truly contains no trans fats, check the ingredients list. If the list contains the words "hydrogenated" or "partially hydrogenated," then the product does contain trans fat.

Where we should look for dietary fats? Sometimes it is easy to identify foods that contain fat. Here are some examples:

  • Butter
  • Margarine
  • Shortening
  • Cooking oils

Other foods may be high in fat, but we may not think of those foods as sources of fat. These are called “invisible fats.” Some examples:

  • Egg yolk
  • Milk (whole milk is higher in fat than 2% or 1% milk)
  • Cheese
  • Meat, fish, chicken (especially the skin), burgers
  • Pies, cakes, cookies, biscuits
  • Nuts, seeds
  • Avocado
  • French fries
  • Chips
  • Crackers
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