Healthy diet and cholesterol
Fats and Lipids
Dietary fats are composed chiefly of three fatty acids attached to a glycerin molecule. All fats are a combination of both saturated and unsaturated fatty acids. Fat is the most calorically dense nutrient supplying 9 calories per gram. Reducing total fat intake and adhering to an exercise program can help an individual achieve weight loss.
Saturated fats are fatty acids with no double bonds. With the exception of palm, palm kernel, and coconut oils, saturated fats are solid at room temperature. and come primarily from animal fats. These fats contribute to atherogenesis by raising serum LDL cholesterol levels in animals and humans alike.
Unsaturated fats are classified as either polyunsaturated or mono-unsaturated. Fatty acids with one double bond are mono-unsaturated fats. Fatty acids with two or more double bonds are polyunsaturated fats. Both of these types of fats found in fish and plant-food products are generally liquid at room temperature.
The two major categories of polyunsaturated fats are omega-3 and omega-6 fatty acids. Vegetable oils such as corn, sunflower, safflower, and soybean contain omega-6 fatty acids. Polyunsaturated fats from these sources provide essential omega-6 fatty acid, linoleic acid, which is essential because it cannot be synthesized by the body and therefore, must be consumed in the diet. It is required by the body to synthesize arachidonic acid, the precursor of prostaglandins. Essential fatty acid deficiency can result in dry scaly dermatitis, increased susceptibility to infection, and impaired wound healing Substituting foods rich in polyunsaturated fat for those high in saturated fat has been shown to decrease cholesterol levels. Low-fat diets may also lower HDL levels in some individuals.
Fish oils contains omega-3 fatty acids and have been shown to decrease blood pressure and triglyceride levels and increase clotting time. Recent research has also shown that individuals who consumed at least one meal per week of fatty fish rich in omega-3 acids had a lower incidence of heart attacks compared to those who ate fatty fish less often. Because omega-3 acids are concentrated in fish and shellfish, current recommendations advise including these foods in the diet at least once a week. Fresh or canned tuna, salmon, sardines, and herring are good sources of omega-3 fatty acids. Patients with very high triglyceride levels may be prescribed of fish oil supplements to produce a more rapid effect.
Recently, mono-unsaturated fats have received attention because they do not raise LDL cholesterol levels. Canola and oleic oils contain the highest percentage of mono-unsaturated fat. Oleic acid is the major fatty acid found in these oils. High mono-unsaturated oils are especially good for cooking because they develop fewer free radicals when overheated than polyunsaturated oils. Other sources of mono-unsaturated fat include olives, peanuts, avocados, almonds, pistachio nuts and pecans.
Trans fatty Acids
Hydrogenation, the addition of hydrogen atoms to an unsaturated fat changes the fat's structure forming a trans fatty acid. The process is often used by food manufacturers to give longer shelf life to foods by making them less likely to turn rancid, such as crackers, cookies, potato chips, and puddings. Recent evidence suggests that trans fatty acids may raise LDL cholesterol levels narly as much as saturated fatty acids.
WHAT TO CHOOSE
The NCEP advises that eliminating red meat altogether from the diet is not necessary because of the value of its high iron content, zinc,and vitamin B12 content. Rather, suggest leaner red meat substitutions that are lower in saturated fat, and limit intake to 10 to 20% of total calories. Processed meats such as sausage, luncheon meats (bologna or salami), and hot dogs also are high in saturated fat and should be eaten only in limited amounts. Generally, if the food contains more than 3 grams of fat per 100 calories, it contains more than the recommended 30 % of calories from fat.
Because white meat turkey and chicken have decreased amounts of total fat and saturated fat compared to red meat, they should be included in the diet as an alternative. White meat turkey with only 8% fat, is leaner than white meat chicken, which contains approximately 24% total fat. However, the fat content of both turkey and chicken increases significantly when the skin and the dark meat is eaten. Also, most turkey or chicken hot dogs contain approximately 70% fat is less than a regular hot dog which contains 80% total fat.
Fish and Shellfish
Fish and shellfish are good alternatives to meat and poultry because of their low fat and saturated fat content. The cholesterol content in shellfish vary widely, but all shellfish is very low in total fat and saturated fat. As stated above, fish and shellfish are also rich sources of omega-3 fatty acids. Therefore, it is recommended to increase intake of fish, preparing it with lemon and herbs on the grill or in the broiler rather than frying it.
Certain dairy products such as regular cheese and whole milk contain a significant amount of saturated fat. Therefore, determining the amounts and types of dairy products consumed daily is important. Because dairy products are an excellent sources of calcium, completely eliminating them from the diet is not advised, especially for women. Non-dairy creamers, whipped toppings and half and half are laden with saturated fats and should be avoided. Evaporated skim is an acceptable substitute for whipped cream and coffee creamers and in recipes that call for heavy cream.
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