What is cholesterol?
Cholesterol is a fatty substance and is one of several different types of fats found in the body. It has several very important functions and is carried in the blood. If blood vessels are damaged, cholesterol can be deposited and eventually lead to narrowing of the blood vessels. This is more likely to happen if there are high levels of cholesterol in the blood.
Do cholesterol levels matter if I have kidney disease?
Yes, absolutely. Studies have shown that people with kidney disease have an increased risk of heart disease or stroke, especially if they are over the age of 50. They are also more likely to develop narrowing of blood vessels over time compared to other healthy people. This applies when chronic kidney disease is present, even if the kidneys appear slightly abnormal.
Vascular problems in people with kidney disease may be slightly different from those in people with normal kidneys because the minerals calcium and phosphate and vitamin D abnormalities may contribute to vascular disease. However, cholesterol is still an important factor.
Linking Cholesterol to Kidney Problems
Some of the first clues linking high cholesterol to kidney disease came from a study called the Physicians' Health Study. In it, researchers followed about 4,500 healthy men and collected blood samples from them over a period of more than 10 years.
The researchers looked at how the men's kidneys were working through creatinine tests. The test shows how your kidneys remove waste from your blood. They also looked at cholesterol levels.
When they looked at kidney function and cholesterol together, the researchers found that high total cholesterol and high low-density lipoprotein (LDL), or "bad" cholesterol, were seen more often in men with poor kidney function.
Men with poor kidney function also had lower levels of high-density lipoprotein (HDL), or "good," cholesterol. HDL cholesterol is good because it helps prevent cholesterol from building up in the blood vessels.
Another study of more than 15,000 men and women over 3 years also linked kidney disease to high blood lipids. Lower levels of "good" HDL cholesterol can increase the risk of kidney disease. But this study found a stronger link between kidney problems and high triglycerides, another type of fat in the blood.
The findings suggest that high levels of LDL "bad" cholesterol or low levels of HDL "good" cholesterol combined with high levels of other unhealthy lipids make people more likely to develop kidney problems. People with high cholesterol are about twice as likely to develop chronic kidney disease as disease over time.
People with kidney disease are at higher risk for heart disease. When your kidneys are not working properly, it also changes the way your body processes cholesterol and other lipids. As a result, kidney disease and high cholesterol often go hand in hand.
What can patients with kidney disease do to help them keep their blood vessels normal?
Keeping your blood vessels healthy is more than just watching your cholesterol levels. There are several things to keep in mind:
- If you smoke, stop smoking. Smoking is more dangerous than slightly high cholesterol and can lead to cancer as well as accelerated vascular disease.
- Exercise regularly and eat a healthy, balanced diet.
- Make sure you control your blood pressure.
- If you have diabetes, control it as much as possible.
- Make sure you follow a proper calcium and phosphate diet as recommended by your kidney nutritionist.
What causes high cholesterol levels?
Cholesterol levels depend on several factors. If someone's cholesterol levels are high, then other family members may have high cholesterol levels as well.
Kidney disease that causes protein leakage in the urine is associated with high cholesterol, and some kidney diseases are associated with high cholesterol, such as nephrotic syndrome and post-transplant, in part because of the medications used.
Diet and exercise also have a significant impact on cholesterol levels. Diets high in fat and cholesterol may lead to high cholesterol levels. People who are seriously ill and malnourished may have abnormally low cholesterol levels.
What is the ideal cholesterol level?
Research has shown that low cholesterol levels are beneficial and medical advice on ideal cholesterol levels is changing based on ongoing research.
The British Renal Association and the Society of Clinical Diabetologists have recommended (in 2021) that people with kidney disease who are at risk of vascular disease should have a total cholesterol level of less than 4.0 mmol/l.
Cholesterol is carried around the body in several different forms, and in addition to measuring total cholesterol levels, laboratories also measure other forms of cholesterol within the total level. One of these is HDL (high-density lipoprotein) cholesterol, which includes the cholesterol that comes out of the tissues and is taken back to the liver for "recycling". Therefore, higher levels of HDL cholesterol are a good cholesterol.
LDL (low-density lipoprotein) cholesterol is the part of cholesterol that is most closely related to the "bad" cholesterol. . The Kidney Association guidelines say that LDL cholesterol levels should be less than 2.0 millimoles per liter.
These "ideal" cholesterol levels are so low that not everyone can achieve them; the Kidney Association recommends that a reduction in total cholesterol from the initial 25% and 30% of LDL is sufficient.
The target levels given above are different from those in some other guidelines and will undoubtedly change in the future. Therefore, if someone's cholesterol levels do rise above these fairly strict targets, they should discuss with their doctor the benefits of lowering cholesterol levels in their individual situation.
What is the best diet for lowering cholesterol?
Changing your diet can have a big impact on your blood cholesterol levels. The goal of the diet is to reduce the intake of harmful fats and maintain a balanced diet with moderate amounts of protein, carbohydrates, and fresh fruits and vegetables. The optimal diet varies from person to person, and if some obvious dietary measures fail to lower high cholesterol levels, consultation with a renal dietitian is usually recommended.
Foods high in cholesterol include dairy products, eggs, and the fatty portions of red meat. Many processed foods may contain high levels of cholesterol and the data on the label should be checked. The types of fats that increase blood cholesterol levels are often called "saturated fats", while "unsaturated fats" (including olive oil) may be less harmful. It's not just foods containing meat that may be high in fat; cookies, for example, may also be high in fat.
What medications are available to lower cholesterol?
If diet and weight loss do not lower blood cholesterol to an acceptable level, medications may be used. You will also need to consider treatment to slow the leakage of protein in the urine.
The most commonly used types of medications have an effect on the liver and can reduce cholesterol production. These drugs are called "statins". There are several different drugs in the statin class, and all of them have names ending in -statin. There are subtle differences between the different statins, and the prescribing doctor will recommend the one that is best for a particular person.
In many parts of the country, there is a preferred statin that is usually the most cost effective, but if this is not right for someone, alternatives are available. All statins have side effects. Some people usually experience nausea or sickness and may have to stop taking the drug if this persists. Statins can cause muscle soreness, which is a serious side effect and should be seen by a doctor immediately
There are several other types of medications that can be added to statins or used when statins are intolerant. These affect either the absorption of cholesterol from food or the way it is processed in the body.
All medications used to treat cholesterol need to be monitored by blood tests and may require dose increases over time to maintain target blood cholesterol levels. These medications are not a substitute for a low-fat diet, weight loss, or quitting smoking. It is important to maintain measures in all areas to combat vascular disease.
Who should take medications to lower cholesterol levels?
In people without kidney disease, statins are prescribed to people who are at 20% (two-tenths) or more risk of having a heart attack or stroke in the next 10 years. This includes anyone who has already had a heart attack or stroke; otherwise the risk is estimated based on age, sex, cholesterol and blood pressure levels, and whether the patient has diabetes. Unfortunately, doctors are unsure when to recommend statins for patients with kidney disease.
National cholesterol treatment guidelines recommend treating cholesterol in stages 3 and 4 of CKD. Many guidelines recommend treating cholesterol if you are over 50 and have moderate kidney disease (eGFR <60 ml.min); or younger with increased risk factors. In more mild kidney disease, doctors may estimate the risk of heart attack and stroke, and based on this calculation may consider whether statins may be helpful.
This recommendation is based on the experience of senior kidney specialists because although statins have been shown to reduce the risk of heart attack and stroke in people without kidney disease, those with severe kidney disease (including transplants) have not been included in any studies.
When researchers study the effects of statins on people on dialysis, the benefits are less clear. Nephrologists now do not usually start statins after starting dialysis, but if they have started them, they do not routinely stop using them. Sometimes they are even stopped. However, there are clear benefits to chronic kidney disease over people on dialysis and kidney transplants.
How to manage high cholesterol and kidney disease?
Cholesterol-lowering medications can help reduce the risk of heart attack and stroke. But can you take them if you have kidney disease?
Research shows that if you have early kidney disease, taking medications to lower your cholesterol is usually a good idea. In most cases, doctors will prescribe drugs called statins for this purpose. Studies have shown that this treatment can lower cholesterol and help reduce the risk of heart disease or stroke.
It's less clear whether they help once kidney disease has progressed further. Statins may not be recommended if you need dialysis or have had a kidney transplant. It's also less clear whether cholesterol-lowering treatments help prevent kidney disease from getting worse.
Another way to lower cholesterol in kidney disease is to eat right and adopt other healthy lifestyles. For example, one study showed that a high-fiber diet can lower cholesterol in people with kidney disease.
To reduce unhealthy fats in your diet, you can.
- Limit red meat and processed meats.
- Choose nonfat, low-fat or fat-free dairy products over full-fat dairy products.
- Avoid fried foods.
- Cook with healthy oils such as vegetable oils.
- Eat more fruits, vegetables, whole grains, poultry, fish and nuts.
- Skip foods and beverages that contain sodium or sugar.
Other lifestyle factors that may help include:
- Exercise
- Not smoking
- Losing excess weight
If you have high cholesterol and kidney disease or think you are at risk, talk to your doctor about what you can do to help reduce these risks.
References：
1. Cholesterol and Your Kidneys: A Fatal Connection - Cholesterol
2. Cholesterol and kidney Disease | National Kidney Federation
Explore More Blog
The Promising of Cholesterol Testing