最後更新日期 十一月 15, 2021.
High cholesterol and triglyceride are singled out by numerous studies as the culprit of many cardiovascular and cerebrovascular diseases, such as coronary heart disease and stroke. Many patients with high cholesterol give up eating egg yolks, squid, offal, and other foods high in cholesterol, only to be disappointed by an insignificant change in their cholesterol level — because cholesterol and triglyceride in foods are not the only causes to blame. Only about 30% of the cholesterol in the blood comes from diet, and the rest is made by the liver. Nonetheless, trans fat and saturated fat are 2 mischievous baddies to look out for in foods, as they may also lead to high blood cholesterol and increased risk of cardiovascular disease, namely.
This article will guide you through the concept of cholesterol and give you some tips on lowering your cholesterol.
Learn more about cholesterol
Cholesterol is a type of fat mostly made by the liver. After cholesterol is combined with various lipoproteins in the blood, it will be transported to various parts of the body for use. Cholesterol is divided into “bad” cholesterol — low-density lipoprotein (LDL) cholesterol, which easily accumulates and deposits on the inner wall of blood vessels; and “good” cholesterol — high-density lipoprotein (HDL) cholesterol, which helps transport excessive “bad” cholesterol in the blood back to the liver for degradation. In healthy individuals, cholesterol levels are sufficiently managed through self-regulation in the body.
Daily recommendation for total fat intake
According to the Centre for Food Safety, of the recommended daily caloric intake of 2,000 calories per day for men and 1,500 calories for women, 20-35% should come from fat. Men should take no more than 65g (about 13.3 teaspoons) of fat per day, while women should take no more than 50g (about 10 teaspoons) of fat per day.
Risk of high blood cholesterol level
Blood cholesterol exceeding the optimal level poses a threat to health. If the “bad” LDL cholesterol content increases but the “good” HDL cholesterol content is low, the excess cholesterol and triglycerides cannot be effectively removed. Owing to the unbalanced eating habits of many busy Hong Kongers, coupled with the lack of exercise and overwhelming mental stress, the “bad” LDL cholesterol is forced to rise gradually. The “bad” LDL cholesterol increases the accumulation of plaque on the inner wall of the blood vessels over time, not only narrowing the blood vessels but in severe cases, gradually becoming atherosclerotic plaques that hinder blood circulation. The consequences, such as stroke and heart attack, can be detrimental.
A nutritional science expert from the University of Toronto, Professor David J.A. Jenkins proposed a cholesterol-lowering diet — portfolio diet. The rationale of the diet is to reduce blood cholesterol levels by incorporating different foods with cholesterol-lowering properties into the diet. As compared to a low-saturated-fat therapeutic diet (as the control), portfolio diet resulted in a greater cholesterol-lowering effect. The following are different cholesterol-lowering foods recommended by portfolio diet:
Soluble fiber, a type of dietary fiber, is responsible for removing “bad” LDL cholesterol in the blood.
Oats, fruits and vegetables, legumes, and whole grains are good sources of soluble fiber. Oats contain a variety of soluble fiber, including β-glucan. According to a review article published by Oxford Academic , the proposed mechanism by which oat β-glucan may lower blood cholesterol levels is by adhering to bile acids for excretion, thereby increasing the synthesis of bile acids from cholesterol to replace the lost bile acid and reducing the circulation of “bad” LDL cholesterol in the blood. A daily intake of at least 3g of oat β-glucan (which is equivalent to 100g of raw oats) is required to reduce total cholesterol and “bad” LDL cholesterol significantly.
Foods that are rich in soluble fiber include chia seeds, barley, apples, strawberries, and eggplants.
Studies showed that the protein in soybeans and other beans helps reduce the amount of cholesterol produced by the liver. As the proposed mechanism suggests, soy protein can inhibit the absorption of cholesterol in the intestines, thus lowering the blood cholesterol level. Isoflavones in soybeans also decrease the total and “bad” LDL cholesterol level while increasing the “good” HDL cholesterol level. Moreover, soy protein is low in saturated fat and is, therefore, an ideal protein source for red meat for vegetarians and vegans. As shown in a meta-analysis of 46 studies, an intake of 25g of soy protein per day (equivalent to 300g of tofu or 600ml of soy milk) can reduce blood cholesterol levels by 5-6%.
Other than soybeans, lentils, chickpeas, and other beans are good choices of plant protein to lower blood cholesterol levels.
Plant sterols or stanols
Fruits and green leafy vegetables, along with vegetable oils, nuts and seeds provide rich sources of plant stanols or sterols, which work like soluble fiber by competing with cholesterol for absorption to decrease cholesterol levels in the body. A 2013 review article revealed that sterols or stanols mimic cholesterol and compete with it, reducing its absorption.
It is hard to consume sufficient sterols or stanols from a normal diet, so they are often fortified into common foods, such as yogurt, beverages (e.g. orange juice,) and margarine.
There are 2 active forms of omega-3, EPA and DHA.
The Overview of Omega-3 Fatty Acid Therapies pointed out that the EPA and DHA in fatty fish can help reduce triglycerides. Among them, DHA can help reduce “bad” cholesterol and increase good cholesterol. It also inhibits the synthesis of triglycerides. On the other hand, EPA also affects lowering blood cholesterol, and it helps prevent thrombosis, a condition characterized by blood clotting inside blood vessels that obstructs blood flow eventually.
Fish with rich sources of omega-3 fatty acids include salmon, tuna, and mackerel. The American Heart Association recommends including fatty fish in your diet at least twice a week for the optimal cholesterol-lowering effect.
High cholesterol foods to avoid
Some foods with high saturated fat
Examples of saturated fats include fatty meat, full-fat milk, butter, bacon, foie gras (goose liver), pork belly, pork ribs, lard, etc. Some hidden sources of saturated fats are solid fats at room temperatures, such as chicken skin, pork bone soup, coconut, coconut milk, coconut oil, coconut milk, whole milk foods, cakes, instant noodles and palm oil.
According to the Food and Agriculture Organization of the United Nations, it is recommended that no more than 5% of the daily caloric intake comes from saturated fat. The recommended number is equivalent to saturated fat of no more than 22g (about 4.4 teaspoons) per day for men, and no more than 16g (about 3.2 teaspoons) per day for women.
Foods with high trans fat
Trans fats are artificial fats in foods like margarine, butter cake, cookies, french fries, shortening, croissant, egg tart, etc. Ruminants also produce trans fat, although their effect on cholesterol is not the same industrial trans fat.
The recommendation for intake of trans fats is straightforward: the less the better. If it cannot be avoided, it must be lower than the daily recommendation of fat intake (including saturated fat and trans fat).