Studies continue to be published indicating that high levels of cholesterol in the blood increase the risk of developing heart disease. That's been known for decades, but some recent data have changed dietary recommendations for lowering blood cholesterol. I thought it might be helpful to clarify the distinction between different blood and dietary fats and share recent findings and resultant dietary recommendations.
Cholesterol is a white, waxy, fat-like substance needed by the body to make various hormones and cell membranes, and to help the liver with fat digestion. The liver produces about 1,000 milligrams of cholesterol per day on its own. Most people take in another several hundred milligrams a day in their food.
The body produces the cholesterol it needs, without the addition of dietary intake. However, in a varied diet, some fat is inevitable and healthy. How to sort this out? First, some background about blood fats.
Being so closely related to fat, cholesterol doesn't dissolve in water. So, to travel through the bloodstream, it attaches to proteins, forming lipoproteins. There are several different types of lipoproteins circulating in our bloodstreams. Think of these lipid (fat) molecules as little balls of varying size: The high-density lipoproteins (HDL) are the smallest, the low-density lipoproteins (LDL) are medium, and the very low-density lipoproteins (VLDL) are the largest.When you have your blood fats analyzed by a physician, tests show the total cholesterol level as well as the percentages of the HDL, LDL and VLDL. The significance of this breakdown is essential to your heart health.
The HDL cholesterol (smallest molecules) are actually thought to be protective of the arteries, acting almost like little detergent bubbles to keep the larger fat molecules (LDL, VLDL) from building up in the arteries. So, the higher your HDL level and the lower your LDL and VLDL levels, the better.
Another component of this analysis is your triglyceride level. High levels of these blood fats are also linked to heart disease and managed by the dietary and lifestyle recommendations for lowering cholesterol.
There are several lifestyle factors that contribute to a healthy blood-fat profile. Exercise -- even 20 minutes a day of cardiovascular activity such as walking, swimming or biking -- can help elevate the good cholesterol and lower the bad. Controlling blood sugar, if you have diabetes, also will help decrease triglycerides and protect the heart.
Dietary recommendations for managing cholesterol have changed dramatically over the past decades. While it used to be thought that eggs and shrimp, high in dietary cholesterol, should be avoided, we now know that they are fine in moderation (not fried or soaked in butter). The real culprits appear to be saturated fats and trans-fats. Following is an explanation:
Saturated fats are solid at room temperature. The white marbling in meat, whole-milk dairy products such as butter and cheese, and coconut and palm oil (plentiful in commercial baked goods) are the sources of these fats which raise LDL cholesterol.
Trans-fatty acids are contained in margarine and vegetable shortening and act in ways similar to saturated fats to raise LDL cholesterol levels and lower HDL. These are fats produced by heating vegetable oils in the presence of hydrogen. This hydrogenation process makes the fat harder at room temperature and is used to extend the shelf-life of baked goods.
Polyunsaturated fats are liquid at room temperature and are found in vegetable oils -- corn, safflower, soybean, etc. While it was once thought that these fats reduced cholesterol, research is divided now. Some studies suggest that while they don't raise LDL levels, they may lower HDL (good) cholesterol levels. Other studies show that they decrease LDL and raise HDL. Since the data don't seem to be complete, it might be a good idea to limit intake.
Monounsaturated fats are the predominant fats in olive and vegetable oils, and also found in nuts and avocados. These fats are healthy, decreasing LDL and increasing HDL. Nonetheless, if you're watching calories, be aware that all fats have the same number of calories, so being healthful in your choices of fats may not result in a decrease in calories or weight loss.
Omega-3 fatty acids are polyunsaturated and found mostly in seafood (salmon, mackerel and herring), but also available in flaxseeds/oil, walnuts and soybeans.
The current data tell us that the fats to be avoided are saturated fats and trans-fats. Favor the monounsaturated fats, and be moderate with the polyunsaturated fats.
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