Cholesterol is a fatty molecule found in different tissues of the body and circulated through the blood. It is produced within the body tissues, mainly by the liver, and also gets absorbed from the diet consumed. Cholesterol also called lipid molecules, are found in the walls of cells in all parts of the body, more so in the nervous system. It gets stored in the liver and adipose tissue. The body uses cholesterol to make cell membranes, hormones, bile acids, vitamin D, and other substances. Cholesterol circulates to and fro to the tissues but needs to be attached to specific protein molecules in the bloodstream. These lipid-protein complexes are called lipoproteins, which have cholesterol (lipid) inside and protein outside. Two specialized kinds of lipoproteins that carry cholesterol in the blood are low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL is also called the “bad” cholesterol because it carries cholesterol to tissues. HDL is also called the “good” cholesterol because it carries cholesterol from tissues to the liver, where it gets degraded or transformed. Most of the circulating cholesterol is in the LDL form. The higher the serum cholesterol concentration, the higher the chance of its deposition in the tissues leading to disease manifestations of coronary artery disease and cerebrovascular disease.
Serum cholesterol is determined by many risk factors broadly classified as non-modifiable (genetic predisposition, age, and sex) and modifiable risk factors (diet, physical activity, and weight) of the patients. Diet is the most crucial factor in maintaining cholesterol levels. So, in addition to maintaining an active lifestyle and healthy weight, the intake of a low cholesterol diet is the key to address this significant health concern.
Current issues of concern about dietary cholesterol include its well-known risk associated with the most common medical illnesses, and also concerns of constantly changing diet recommendations. The most important issue of concern regarding cholesterol intake is noncompliance within the general population. In spite of the well-documented correlation between high cholesterol diet and all-cause mortality from cardiovascular diseases through various studies for more than five decades, these diseases continue to be the prominent cause of morbidity and mortality. This fact clearly emphasizes the lack of adherence to the guidelines and the importance of the need for measures to improve not only awareness but also adherence to the food restrictions. Historically it has been recommended to restrict overall fat intake, but the latest randomized control trials have emphasized modifying the quality of fat consumed and its food sources, not the overall fat intake. The recommended quality of fat intake is a diet that has low saturated fat, low trans fat, and rich in minimally processed fat. Foods that are rich in healthy fats, including nuts, avocados, seeds, and fish, should be encouraged.
If there is excessive cholesterol in the blood circulation, some of the excesses can become trapped in arterial walls, over time, this builds up and forms plaques. These plaques can narrow blood vessels and make them less flexible; this process is called atherosclerosis. Atherosclerosis of the coronary circulation results in coronary arterial disease (CAD), and atherosclerosis of the carotid and vertebral arteries results in stroke manifestations. CAD causing ischemic heart disease is the leading cause of death worldwide, followed by stroke-related deaths. Together, both of these pathologies remained as the leading causes of death globally in the last 15 years, accounting for 15.2 million deaths in 2016. Trans fats have adverse effects on lipid and lipoprotein metabolism and promote endothelial dysfunction, insulin resistance, inflammation, and arrhythmias.
There is enough evidence showing that the buildup of plaque in arteries begins in early childhood and correlates to adult atherosclerotic disease. Therefore, regardless of risk factors, all children should be encouraged to follow a healthy diet and lifestyle. Hence, inculcating the habits of healthy eating early on can reduce the risk of cardiovascular disease over time. All children two years and over should be encouraged to consume foods rich in fruits, vegetables, whole grains, nuts, seeds, and fish. We need to limit sugar-rich foods and drinks. Childhood obesity is another growing health menace in the current day lifestyles associated with the intake of foods high in cholesterol.
Even though the low cholesterol diet and its health benefits have a very good overall awareness in the general population, due to more recent studies showing new evidence, there is a need for a more dynamic role from all the healthcare teams. Due to the complexity of cholesterol metabolism and various effects on the disease process, proper education, and clear indications about the current guidelines and recommendations are essential in current-day medicine. Current dietary guidelines recommend that saturated fats should be limited to less than 10 percent of daily calories, replacing them with polyunsaturated fatty acids. But in patients with predisposing conditions, it is recommended to aim for less than 5 to 6 percent of daily calories from saturated fat. The main sources of saturated fatty acids are animal products, such as butter, dairy, meat, salmon, and egg yolks, and some plant products such as chocolate and cocoa butter, coconut. On the other hand, restrict calories from trans fats to less than 1 percent of energy or as low as possible. There are two common sources of trans fats, animal transfat (foods originating from ruminant animals such as cows and sheep) and industrial trans fat (foods containing partially hydrogenated vegetable oils - PHVO). Primary education should be to avoid foods containing PHVO, e.g., vanaspati or stick margarine, commercially baked goods, deep-fried fast foods, and street vendor foods with poor oil quality. Due to strict regulations in the food industry, there has been a considerable reduction in the intake of industrial trans fat; thus, the dietary source of trans fat is now animal foods. Both industrial and animal trans fats have likely similar adverse effects on body cholesterol levels. When fats are necessary for cooking and dressing, use plant oils from fruits, seeds, and nuts with high amounts of monounsaturated and/or polyunsaturated fatty acids, especially canola oil, soybean oil, and olive oil. Replace foods that have high solid fats (e.g., red and processed meats) with foods that have low solid fats. These include seafood, legumes like beans and peas, nuts, seeds, lean meats, poultry, and eggs. Even though there is a divergence of data regarding the health effects of dairy fats, recent guidelines continue to recommend low-fat dairy products. Butter spreads could have high transfat, and a better healthier alternative is liquid margarine or soft margarine, especially look for margarine that says zero gram trans fat on the label. These suggestions are generally consistent with the 2015 Dietary Guidelines for Americans and mostly recommended by ACC and AHA.
Essential to note while providing comprehensive dietary intake goals are, not to focus on restricting total fat intake; instead, replace trans fat and saturated with mono and polyunsaturated fat. Caution should is advisable as many foods marketed as “low-cholesterol” may have high levels of saturated fat or trans fat. Emphasis should also be to increase the consumption of bioactive foods like fruits, nuts, seeds, vegetables, legumes, whole-grain products, and plant-oils, which are linked to lower risk of cardiovascular diseases, diabetes, and obesity. Reduce consumption of processed meats, which are high in trans fat, which in turn contribute to the high serum cholesterol levels. Processed meats are any meat that uses smoking, curing, or salting, or additional chemical preservatives for preservation. To lower cholesterol, eating a heart-healthy diet in conjunction with 40 minutes of moderate to vigorous aerobic exercise, at least three to four times a week, is strongly recommended. Recent literature published study results that intake of all meats, either red or white (chicken and turkey), can raise blood cholesterol levels significantly. On the other hand, soy protein shown to reduce LDL levels by a small but significant amount; eating 25 grams of soy protein per day, studied over six weeks, lowered LDL levels by about 3% to 4% was published in recent nutrition journals. Soy is obtainable from foods like tofu, soy milk, meatless veggie burgers, and soy-based protein powders.
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