Biosynthesis of cholesterol is directly regulated by the cholesterol levels present, though the homeostatic mechanisms involved are only partly understood. A higher intake in food leads to a net decrease in endogenous production and vice versa.
The main regulatory mechanism is the sensing of intracellular cholesterol in the endoplasmic reticulum by the protein SREBP (Sterol Regulatory Element Binding Protein 1 and 2). In the presence of cholesterol, SREBP is bound to two other proteins: SCAP (SREBP-cleavage activating protein) and Insig-1.
When cholesterol levels fall, Insig-1 dissociates from the SREBP-SCAP complex, allowing the complex to migrate to the Golgi apparatus, where SREBP is cleaved by S1P and S2P (site 1/2 protease), two enzymes that are activated by SCAP when cholesterol levels are low.
Cholesterol is primarily synthesized from acetyl CoA through the HMG-CoA reductase pathway in many cells/tissues. About 20–25% of total daily production (~1 g/day) occurs in the liver, other sites of higher synthesis rates include the intestines, adrenal glands and reproductive organs.
For a person of about 150 pounds (68 kg), typical total body content is about 35 g, typical daily internal production is about 1 g and typical daily dietary intake is 200 to 300 mg. Of the 1,200 to 1,300 mg input to the intestines (via bile production and food intake), about 50% is typically reabsorbed into the bloodstream.
Cholesterol is a steroid lipid, found in the cell membranes of all body tissues, and transported in the blood plasma of all animals. Most cholesterol is not dietary in origin, it is synthesized internally.
It is present in higher concentrations in tissues which either produce more or have more densely packed membranes; for example the liver, spinal cord, brain and atheroma.
Cholesterol plays a central role in many biochemical processes, but is best known for the association of cardiovascular disease with various lipoprotein cholesterol transport patterns in the blood.
The name originates from the Greek chole- (bile) and stereos (solid), as researchers first identified cholesterol in solid form in gallstones.
Heart disease is caused by narrowing of the coronary arteries that feed the heart. Like any muscle, the heart needs a constant supply of oxygen and nutrients, which are carried to it by the blood in the coronary arteries.
Many people assume that high cholesterol is a problem that affects middle-aged adults only. In fact, many people don’t even worry about their cholesterol when they are younger, eating all the fatty convenience foods they want, assuming that their early diet makes no difference.
Nothing could be further from the truth. More children today suffer from high cholesterol. In fact, the numbers of children who are taking cholesterol drugs is on the rise! Some studies have suggested that a childhood of poor eating choices can contribute to higher cholesterol later in life.
Besides this, many of the eating habits learned in childhood affects eating in adulthood. Children who are used to eating high-fat foods and convenience foods are more likely to make the same choices as adults. Switching to healthy foods in adulthood may be harder for children who have made less-than-heart-healthy food choices all their lives. For all these reasons, controlling food intake and lifestyle choices even in early life can contribute to life-long heart health and good cholesterol levels.
When you have chosen your lean cuts of meat, you can make these foods even healthier by reducing the amount of fat you use in preparing them. For example, marinating poultry and other meats in lemon juice and fresh dill or in pureed fruits and vegetables is a heart-friendly way to get plenty of flavor into your cooking without adding fat.
At many fish shops, you can get planks of cedar that are perfect for baking or grilling fish – simply place the fish on the cedar, cover with lemon juice and possibly herbs and grill or bake until done.
All meat processed in plants which sell their products across State lines must, under Federal law, be inspected for wholesomeness by USDA’s Food Safety and Inspection Service. This mandatory inspection program is paid for by tax dollars.
Combine your favorite fresh fruits in a blender with fresh fruit juice and a small squirt of honey. Combine until blended. This makes an excellent and very healthy snack. It can also be a great quick breakfast on days when you are in a rush.
Experiment with different fruit combinations to find different tastes. Chilling or even freezing some of the fruit before serving can produce a nice chilled drink that is perfect for summer. If you are craving desserts, you can add a small amount of very low fat frozen yogurt to this recipe and use frozen fruits to get a tasty and heart-friendly alternative to ice cream and other desserts.
Desserts and Snacks:
Limiting desserts and snacks in general can help you control your weight and your calories intake and so keep your heart healthy. If you absolutely crave a dessert or snack, though, try to stave off the craving with fresh fruit.
There are a number of pastas available, from fresh pasta or dried pasta to vegetable pastas and rice pastas. All can be made into delicious and heart-friendly meals in minutes. Simply cook the pasta in a pot.
Shred your favorite vegetables or cut them into very small pieces. Combine the vegetables with some low-sodium and low-fat chicken or vegetable broth and cook until vegetables are softer but still crisp.
Add the pasta and toss until the vegetables are the desired consistency. Add your favorite fresh herbs (basil is a good choice) and combine. This can be a very tasty combination and is still quite healthy for you.
You can make similar meals with rice or even low-fat tofu. Many prepared pasta dishes use plenty of salt or cream-based sauces, but some combination of this recipe can give you a tasty meal with less fat.