Cholesterol, like fat, is a member of a family of molecules called lipids. It is a waxy substance that your body requires for essential bodily functions such as hormone synthesis and cell membrane maintenance. The cholesterol in your body comes from two sources. Approximately 25% of cholesterol comes from the fats in your diet and the other 75% is manufactured in your body by the liver.
Because cholesterol circulates in your blood, too much cholesterol can be a risk factor for developing coronary artery disease, which can lead to heart attacks or strokes. Cholesterol can form a thick, hard deposit that can narrow the arteries and make them less flexible. This condition is known as atherosclerosis. According to the American Heart Association, high cholesterol is one of the major risk factors for coronary heart disease but if you also have high blood pressure, diabetes, or smoke, you are at an even higher risk for heart disease.
We know we can’t always control genetic predispositions to heart disease, so what can we do about controlling cholesterol in the diet? The latest 2015-2020 Dietary Guidelines for Americans (DGA) no longer recommend limiting the consumption of dietary cholesterol to 300 milligrams per day, as did previous guidelines. The focus on dietary cholesterol alone has been downgraded in the current DGAs and more attention is now being placed on the influence of saturated and trans fat on blood cholesterol.
Eggs have long been banned from low cholesterol diets, but a 2008 report from the Physicians’ Health Study supports the idea that eating an egg a day is generally safe for the heart. But remember, this does not give consumers a free pass to eat foods high in cholesterol when building healthy eating patterns. The Institute of Health still suggests that individuals should minimize dietary cholesterol as much as possible while consuming a healthy eating pattern. Often, foods that are higher in dietary cholesterol, such as fatty meats and high-fat dairy products, are also higher in saturated fats. The current DGA recommends limiting saturated fats to less than 10 percent of your calories per day and to replace them with unsaturated fats.
It is important to understand the science of what happens to fat when it enters your body. Oils, butter, margarine, nuts, and salad dressings are examples of fats in the diet. After you ingest fat, it travels to your stomach where it hangs around for quite some time. It then empties into your small intestine where it gets broken down by bile acids and enzymes in order for the body to absorb its vital nutrients. From here, fat is sent off to the liver where it is used for many bodily functions as mentioned earlier.
Like fat, cholesterol molecules don’t mix with water, which is the major component of blood. So, the liver packages the fat together with cholesterol and protein, and sends it through the bloodstream on carriers called “lipoproteins”. The main lipoproteins involved in carrying fat and cholesterol through your body are LDL (low-density lipoprotein), commonly referred to as “bad cholesterol”, HDL (high-density lipoprotein) known as “good cholesterol”, and VLDL (very low-density lipoprotein). Each one of the lipoproteins has a job to do. The VLDL travels through your bloodstream, unloading fat along the way. With the fat gone, the remaining cholesterol and protein pieces form the LDL. The LDL then carries the cholesterol to different parts of your body. Yeah, that’s a lot of science! Hang on, there’s more.
As LDL travels through your bloodstream, some cholesterol pieces can get stuck on blood vessel walls. This can lead to narrowing of the blood vessel walls, causing blockages that can result in heart disease. HDL cholesterol helps free some of the LDL cholesterol left in the blood vessels and returns it back to the liver, where it is repackaged into new VLDL or it is excreted from the body. Having high levels of HDL in your bloodstream is desired because they act like cleaners, helping to get rid of the excess cholesterol.
Maintaining a diet that is low in saturated and trans fats, and high in soluble fiber and unsaturated fats (poly and mono) can help lower cholesterol and lower your risk for heart disease. Here are some examples of fats found in our diets:
- Polyunsaturated fat (PUFA) is found in vegetable oils like sunflower, corn, soybean, and cottonseed oils. Seeds that include sesame, sunflower, pumpkin, and flax seeds are also good sources, as are some nuts. Omega-3 fatty acids are a type of PUFA found in seafood, such as salmon, trout, herring, tuna, and mackerel, and in flax seeds and walnuts.
- Monounsaturated fat (MUFA) is found in olive, canola, peanut, sunflower, and safflower oils, and in avocados, peanut butter, and most nuts. Some animal fats also contain MUFAs.
- Saturated fat is found in animal products (especially in the skins of poultry and heavily marbled beef) but is also found in coconut and palm kernel oils, and higher fat dairy like butter and cream. Some nuts, like macadamia, are high in saturated fats, as well.
- Trans fat is primarily a man-made fat but some animal sources naturally contain it. Hydrogenating oils turn them into unhealthy fats. The Food and Drug Administration (FDA) authorizes food labels to state “0 grams” of trans fat if the food contains less than 0.5 grams per serving. So, if you see “partially hydrogenated” in the ingredients list, make sure to avoid these foods. Individuals should limit their intake of trans fats to as low as possible. In 2018, TFA’s (Trans Fatty Acids) will be banned from foods altogether, per FDA regulations.
Fiber is an important nutrient for our health. By definition, dietary fiber consists of polysaccharides (carbohydrates) and lignin in plants that are resistant to being broken down by our bodies’ digestive enzymes. The Institute of Medicine concluded (2001-2002) that fiber helps to prevent constipation, lowers cholesterol and blood sugar, helps the immune system, and improves gastrointestinal bacterial fermentation. The recommended daily amount of fiber is 25 grams for women and 38 grams for men. After age 50, the fiber needs drop to 21 grams for women and 30 grams for men. Soluble fiber helps to lower LDL cholesterol. Good sources of this include oats, oat bran, psylium, barley and legumes. Try to achieve 10 grams of soluble fiber per day for heart health.
Mediterranean-style and vegetarian eating patterns have been associated with positive health outcomes in many evidence-based research studies. Other lifestyle interventions to help reduce heart disease risk are getting regular exercise, avoiding tobacco smoke, and losing weight. A regular exercise program can help raise your HDL cholesterol and promote gradual weight loss which will help you keep the pounds off. Changing your lifestyle is an effective way to lower or maintain your cholesterol, but it can take up to six months to see changes in your cholesterol numbers.
It’s important to have your cholesterol monitored by your doctor, especially if there is known heart disease in your family. They may decide to put you on medication if lifestyle changes, like diet and exercise, don’t make a big difference in your lab results. A registered dietitian can educate you on which specific foods to eat in your diet to help lower your cholesterol and to successfully maintain an overall heart healthy program.