Dietary Fats and Blood Cholesterol

There are different types of fats in our food, including cholesterol, saturated fats, and unsaturated fats. Cholesterol and saturated fats increase blood cholesterol levels, while unsaturated fats lower them. To limit saturated fat intake, it's crucial to check product labels. Many labels now disclose the amount of saturated fat present. If not, two rules can help identify saturated fats: they remain solid at room temperature, and dairy products and foods from animal sources are usually high in saturated fat. However, palm oil and coconut oil are exceptions. Despite being vegetable-based, they are high in saturated fat.

To reduce saturated fat consumption, avoid or limit foods like solid shortenings, fatty meats, animal fat products, and dairy products. Dairy products like cream, butter, and whole milk contain saturated fat and cholesterol. Lower-fat options with labels indicating lower percentages, like 2%, 1%, or .5%, are available. The American Heart Association recommends .5% milk (skim milk) for adults and children over two years old.

Saturated fats raise blood cholesterol levels and should be limited in our diets. They are usually solid at room temperature and found in animal-derived and dairy products. Coconut and palm oils should also be avoided due to their high saturated fat content. Using the two rules of thumb can help make informed choices for low-fat products.

What are Polyunsaturated Fats?

Polyunsaturated fats are a type of fat found in various foods and can help lower cholesterol levels. Sources include fish oils and liquid vegetable oils, but palm and coconut oils are exceptions and not considered polyunsaturated fats. These fats can solidify through hydrogenation, behaving like saturated fats and increasing cholesterol levels. Partially hydrogenated oils, commonly found in margarine, can still be labeled as low-fat options. Reading food labels is essential to determine if a food is suitable for a low-fat diet. A 2:1 ratio of polyunsaturated to saturated fats is recommended to maintain stable cholesterol levels, while consuming more polyunsaturated fats can lower cholesterol.

Examples of polyunsaturated vegetable fats include corn oil, sunflowerseed oil, safflower oil, soybean oil, cottonseed oil, and liquid vegetable oils in general.

Polyunsaturated fats can be divided into vegetable polyunsaturates and fish oils. While vegetable polyunsaturates have been widely discussed, fish oils were initially overlooked. However, a significant study showed that Eskimos in Greenland, whose diet consisted mainly of fish, had a low incidence of heart disease. This led researchers to investigate fish oils and their potential benefits. It was discovered that certain polyunsaturated fats found in cold-water fish effectively lower blood cholesterol levels. Compared to vegetable polyunsaturates, fish oil polyunsaturates have a greater impact on reducing cholesterol, but it can be challenging to consume enough fish oils through regular food intake. Consequently, fish oil capsules and gelatin supplements have been developed for easier consumption.

The difference between vegetable polyunsaturates and fish oil polyunsaturates lies in their chemical structure and how the body utilizes the fat. The desaturation position of the fatty acids plays a significant role in their cholesterol-lowering abilities. Vegetable polyunsaturates are desaturated at the omega-6 position, while fish oils are desaturated at the omega-3 position. This difference affects the effectiveness of fish oil polyunsaturates in lowering cholesterol compared to vegetable polyunsaturates. Fish oils also tend to have longer and more unsaturated fatty acid chains, particularly rich in a long-chain omega-3 fatty acid called EPA. Despite containing cholesterol, omega-3 polyunsaturated fats still contribute to reducing blood cholesterol levels. Some fish oil supplements are now cholesterol-free, and it is recommended to choose these options. In summary, polyunsaturated fats from any source have a cholesterol-lowering effect.

Not all polyunsaturated fats and oils are equal. While oils and fats contain different types of fats, including saturated, polyunsaturated, and monounsaturated fats, their effects on cholesterol levels vary. Monounsaturated fats, a subtype of polyunsaturated fats, have only one double bond and generally do not impact LDL cholesterol levels. However, certain monounsaturated fats with desaturation in the omega-3 position can help lower LDL cholesterol. On the other hand, saturated fats primarily raise total cholesterol by increasing LDL levels. Polyunsaturated fats, in general, lower total cholesterol. Therefore, it is recommended to choose oils with a higher proportion of polyunsaturated fats. Caloric intake does not affect the type of oil chosen since all fats and oils provide 9 calories per gram.

Here are some examples of oils and fats with their percentages of saturated and polyunsaturated fats:

  • Olive oil: 9% polyunsaturated, 14% saturated
  • Palm oil: 2% polyunsaturated, 81% saturated
  • Sunflower oil: 64% polyunsaturated, 10% saturated
  • Corn oil: 58% polyunsaturated, 13% saturated
  • Soybean and cottonseed oils: 40% polyunsaturated, 13% saturated
  • Peanut oil: 30% polyunsaturated, 19% saturated
  • Butter: 4% polyunsaturated, 61% saturated
  • Coconut oil: 2% polyunsaturated, 86% saturated

It is important to note that while the focus is on the saturated and polyunsaturated fat ratios, some oils also contain significant amounts of monounsaturated fats.

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