Almost all foods contain some fat. Even quintessential fat-free foods like carrots and lettuce contain small amounts of this nutrient. That's a testament to how important fats are for life. Fat provides a terrific source of energy as well as a great depot for storing it. It is an important part of cell membranes, helping govern what gets into cells and what comes out. The body uses cholesterol as the starting point to make estrogen, testosterone, vitamin D, and other vital compounds. Fats are also biologically active molecules that can influence how muscles respond to insulin's "open up for sugar" signal; different types of fats can also fire up or cool down inflammation.


Fat and cholesterol can't dissolve in water or blood. The body gets around this basic chemistry problem by packaging fat and cholesterol into tiny, protein-covered particles called lipoproteins. Although lipoproteins can carry quite a bit of fat, they mix easily with blood and flow with it. Some of these particles are big and fluffy, others small and dense. The most important ones are low-density lipoproteins, high-density lipoproteins, and triglycerides.
  • Low-density lipoproteins (LDL) carry cholesterol from the liver to the rest of the body. Cells latch onto these particles and extract fat and cholesterol from them. When there is too much LDL cholesterol in the blood, these particles can form deposits in the walls of the coronary arteries and other arteries throughout the body. Such deposits, called plaque, can narrow arteries and limit blood flow. When plaque breaks apart, it can cause a heart attack or stroke. Because of this, LDL cholesterol is often referred to as bad, or harmful, cholesterol.

  • High-density lipoproteins (HDL) scavenge cholesterol from the bloodstream, from LDL, and from artery walls and ferry it back to the liver for disposal. Think of HDL as the garbage trucks of the bloodstream. HDL cholesterol is often referred to as good, or protective, cholesterol.

  • Triglycerides make up most of the fat that you eat and that travels through the bloodstream. As the body's main vehicle for transporting fats to cells, triglycerides are important for good health. But as is the case for so many things, an excess of triglycerides can be unhealthy.
In general, the lower your LDL and the higher your HDL, the better your chances of preventing heart disease and other chronic conditions.



Diet and Cholesterol: How Fat and Cholesterol in Food Affect Blood Levels

The types of fat in the diet determine to a large extent the amount of total and LDL cholesterol in the bloodstream. Cholesterol in food matters, too, but not nearly as much.



Good Fats: Unsaturated Fats


Unsaturated fats are called good fats because they can improve blood cholesterol levels, ease inflammation, stabilize heart rhythms, and play a number of other beneficial roles. Unsaturated fats are predominantly found in foods from plants, such as vegetable oils, nuts, and seeds. They are liquids at room temperature.

There are two types of unsaturated fats:
  • Monounsaturated fats are found in high concentrations in canola, peanut, and olive oils; avocados; nuts such as almonds, hazelnuts, and pecans; and seeds such as pumpkin and sesame seeds.

  • Polyunsaturated fats are found in high concentrations in sunflower, corn, soybean, and flaxseed oils, and also in foods such as walnuts, flax seeds, and fish. Omega-3 fats, which are fast becoming the darling of the supplement industry, are an important type of polyunsaturated fat. The body can't make these, so they must come from food. An excellent way to get omega-3 fats is by eating fish two or three times a week. Good plant sources of omega-3 fats include chia seeds (sold as Salvia), flax seeds, walnuts, and oils such as flaxseed, canola, and soybean.

Bad Fats: Saturated Fats

Our bodies can make all the saturated fat we need, so we don't need to eat any of it. That's why saturated fat can be in the bad category—because we don't need to eat any of it, and it has undesirable effects in cardiovascular disease. In the United States and other developed countries, saturated fats come mainly from meat, seafood, poultry with skin, and whole-milk dairy products (cheese, milk, and ice cream). A few plant foods are also high in saturated fats, including coconut and coconut oil, palm oil, and palm kernel oil. Saturated fats boost total cholesterol by elevating harmful LDL. Like all dietary fat, saturated fat also raises the protective HDL. Unsaturated fat is much preferable since it lowers the bad cholesterol and raises the good.

As a general rule, it's a good idea to keep your intake of saturated fats as low as possible. Saturated fats are part of many foods, including vegetable oils that are mainly unsaturated fats, so we can't eliminate them from our diets. Seven percent of total calories or lower is a good target. Red meat and dairy fats are the main sources of saturated fat in our diets, so keeping these low is the primary way to reduce intake of saturated fat.


Very Bad Fats: Trans Fats


Trans fatty acids, more commonly called trans fats, are made by heating liquid vegetable oils in the presence of hydrogen gas, a process called hydrogenation. Partially hydrogenating vegetable oils makes them more stable and less likely to spoil. It also converts the oil into a solid, which makes transportation easier. Partially hydrogenated oils can also withstand repeated heating without breaking down, making them ideal for frying fast foods. (Fully hydrogenating a vegetable oil creates a fat that acts like a saturated fat.) It's no wonder that partially hydrogenated oils have been a mainstay in restaurants and the food industry.

Most of the trans fats in the American diet come from commercially prepared baked goods, margarines, snack foods, and processed foods, along with French fries and other fried foods prepared in restaurants and fast food franchises.

Trans fats are worse for cholesterol levels than saturated fats because they raise bad LDL and lower good HDL. They also fire inflammation, an overactivity of the immune system that has been implicated in heart disease, stroke, diabetes, and other chronic conditions.



Recommendations for Fat Intake

Although the different types of fat have a varied—and admittedly confusing—effect on health and disease, the basic message is simple: Out with the bad, in with the good. As you limit the amount of trans and saturated fats in your diet, as the American Heart Association, National Cholesterol Education Program, and others recommend, keep in mind that there is no good evidence that replacing saturated fat with carbohydrates will protect you against heart disease, while there is solid proof that replacing saturated fat with unsaturated fats will help.
  • Try to eliminate trans fats from partially hydrogenated oils. Check food labels for trans fats; avoid fried fast foods.
  • Limit your intake of saturated fats by cutting back on red meat and full-fat dairy foods. Try replacing red meat with beans, nuts, poultry, and fish whenever possible, and switching from whole milk and other full-fat dairy foods to lower fat versions.
  • In place of butter, use liquid vegetable oils rich in polyunsaturated and monounsaturated fats in cooking and at the table.
  • Eat one or more good sources of omega-3 fats every day—fish, walnuts, canola or soybean oil, ground flax seeds or flaxseed oil.


Any feedback or suggestions, please feel free to Comment or send an email to dhnair@gmail.com.

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