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| [Image: Healthy fats] |
| [Image: Nuts are a source of healthy fats] |
Introduction & 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 in recent years. According to the 2005 Dietary Guidelines for Americans, we should consume a diet low in saturated fat, trans fats and cholesterol. It is recommended that 20% - 35% 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, which means they don’t dissolve in water.
In this lesson, you will learn about:
Ø Different types of fat and their effect on health.
Ø How much fat is recommended as part of a healthy diet.
Ø Food sources of fat.
Ø Foods that lower the LDL cholesterol.
Ø How to decrease the total amount of saturated fat, trans fat and cholesterol in your diet.
Facts about Fats
Fats can be saturated or unsaturated. Unsaturated fats can be monounsaturated or polyunsaturated. Saturated fats are solid at room temperature; unsaturated fats (also called oils) are liquid. Unsaturated fats become rancid more quickly when exposed to air or heat over time.
Sources of saturated fats include animal products, palm oil and coconut oil. It raises blood cholesterol more than other forms of fat. Unsaturated fats are found in plants, vegetable oils, meats and dairy products. 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 or 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 of the products in which it is used. High intake of trans fat may lead to high blood levels of LDL cholesterol, which is a risk factor for CVD (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 3 fatty acids. Some triglycerides, though, may have only 1 or 2 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 2 types of essential fatty acids. The essential fatty acids are important to maintain 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:
Ø vegetable oils (canola, soybean, corn and safflower oil)
Ø walnuts
Ø flaxseed
Ø 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 800 milligrams each day). Cholesterol provides no calories, so it is not used for energy in the body.
There are 3 types of blood cholesterol:
- LDL cholesterol
- HDL cholesterol
- VLDL cholesterol
LDL –cholesterol is also called “bad cholesterol.” Why? Because high levels of LDL is a risk factor for heart disease. On the other hand, the HDL is called “good cholesterol.” High levels of HDL are heart-healthy.
Although it is important for us to get some cholesterol, it is recommended that the total daily cholesterol intake should be less 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 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 cholesterol should be higher than 60 mg/dl.
HDL can be low in people who smoke or are obese (BMI > 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.
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, as well as 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:
Ø give us energy and essential fatty acids
Ø carry the fat-soluble vitamins
Ø are part of cell membranes
Ø are a source of antioxidants
Ø make us feel full longer
Ø make foods taste better
Ø help maintain body temperature (insulation)
Ø protect body organs (insulation)
Fat and Nutrition Facts Label
The U.S. Food and Drug Administration (FDA) requires that total amount of fat, saturated fat, trans fat and cholesterol per serving 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:
Ø “Fat-free” (example: fat-free milk) - less than 0.5 g fat per serving.
Ø “Low-fat” – 3g or less of fat per serving
Ø “Low-saturated fat” – 1g or less of saturated fat and 0.5 g or less of trans fats per serving
Ø “Cholesterol-free” - less than 3 mg cholesterol per serving.
Ø “Low-cholesterol” – 20mg or less per serving
Ø “Healthy” – no more than 60mg of cholesterol, 3g fat and 1g saturated fat per serving
Ø “Light” or “lite” – half the fat as in the regular product
Ø “Reduced cholesterol/fat” – 25% less cholesterol or fat as 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:
Ø Butter
Ø Margarine
Ø Shortening
Ø Cooking oils
There are some other foods, though, that may be high in fat; however, we may not think of those foods as sources of fat. These are called “invisible fats.” Here are some examples:
Ø Egg yolk
Ø Milk (whole milk is higher in fat than 2% or 1% milk)
Ø Cheese
Ø Meat, fish, chicken (especially the skin), burgers
Ø Pies, cakes, cookies, biscuits
Ø Nuts, seeds
Ø Avocado
Ø French Fries
Ø Chips
Ø Crackers
Health Claims
Health claims are statements approved by 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 to reduce calories. They can be carbohydrate-based (oat fiber), protein-based (Simplesse), fat-based (Benefat) or combinations (Olestra). There are over 60 fat substitutes on the market. Fat substitutes may help lower blood cholesterol levels.
Summary Recommendations for Fat Intake
Ø Keep total fat intake between 20% and 35% of daily 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 (i.e. replace solid fat with a liquid fat).
Ø Consume a diet with fewer than 10% of calories from saturated fat.
Ø Limit cholesterol intake to less than 300 mg/day.
Ø Consume a diet low in trans fats. Use soft tub or spray margarine instead of stick margarine.
Ø Due to their health benefits, we should consume at least 2 servings of fish (1-oz serving) every week. Eat fish baked or broiled rather than fried.
Ø When selecting and preparing meat, poultry, dry beans, and milk and milk products, choose lean, low-fat or fat-free.
Ø Eat more vegetables, fruits and whole-grain products instead of cakes, cookies and French fries.
Web sites to Visit
2005 Dietary Guidelines for Americans (Consumer Brochure)
http://www.health.gov/dietaryguidelines/dga2005/document/html/brochure.htm
Eating for the Healthy Heart
http://www.fda.gov/opacom/lowlit/hlyheart.html
Cooking the Heart Healthy Way
http://www.nhlbi.nih.gov/health/public/heart/other/syah/index.htm
Empower Yourself: Know Your Cholesterol Number!
http://www.nhlbi.nih.gov/health/public/heart/other/chdblack/empower.htm
High Blood Cholesterol - What You Need to Know
http://www.nhlbi.nih.gov/health/public/heart/chol/hbc_what.htm