What Is Cholesterol?
Cholesterol is a type of fat (sterol) used to build cell membranes, hormones, and vitamin D. You get cholesterol from different animal-based foods such as eggs, meat, butter, and whole-milk dairy products. This fat is often seen as the “bad guy” since many people worldwide struggle with high blood cholesterol levels. But low cholesterol can be equally problematic, although much less common.
Properly balanced cholesterol levels are vital for dietary nutrient absorption, hormone levels, reproductive health, fluid and salt balance, as well as for your calcium status. In the adrenal cortex, cholesterol is broken down to pregnenolone, which is used to make all sex hormones [1, 2].
What’s more, it helps cells communicate and transfers various important molecules into or out of cells. No cell in your body could do without it .
Most cholesterol is created in the liver and gut, while smaller amounts are made in other organs .
The starting point for producing it in the body is lanosterol. On average, humans make 10 mg/day of cholesterol per kg of body weight – but this is highly individual and depends on many factors. If you eat foods high in cholesterol, less needs to be made in the body [1, 3, 3].
Most people associate cholesterol only with negative health consequences. And this is true – although a certain amount of cholesterol is vital for your health, high levels can be very dangerous.
High cholesterol is a common problem – mostly due to an unhealthy diet or lifestyle, although genetic factors can also play a large role. High levels can increase your risk of heart disease by clogging the arteries. They can also contribute to a diverse array of disorders, such as liver disease, Alzheimer’s disease, and other cognitive or brain-related issues [1, 1, 4].
Importantly, it’s not just a matter of whether you have high cholesterol in general. Not all cholesterol is the same, LDL being the more dangerous type. HDL, on the other hand, is usually protective. Their ratio is much more important than total cholesterol levels.
- Total cholesterol
- High-density lipoprotein (HDL) cholesterol
- Low-density lipoprotein (LDL) cholesterol
While total cholesterol is the easiest and cheapest parameter to measure, you should measure LDL and HDL as well if you want to get a better sense of your heart disease risk. To keep things simple, you want to make sure that your good cholesterol (HDL) is high and your bad cholesterol (LDL) and triglycerides are low .
These tests are a bit controversial, and if you are at a higher risk of heart disease you will probably want to keep track of more than just these markers (check tests such as ApoB, Lp(a), and LDL particles). But for most, a routine lipid panel is a great place to start taking care of your heart health!
LDL, HDL, and VLDL
Cholesterol can be converted to LDL, HDL, and VLDL cholesterol. More specifically, the less-talked-about VLDL makes LDL, which can clog the arteries, while HDL may protect them and help prevent heart disease [3, 7, 8, 9].
Overall, LDL and HDL work together to maintain cholesterol levels. LDL delivers cholesterol from the liver to organs that use it. HDL gathers unused cholesterol from organs and returns it to the liver for reuse .
Diet heavily influences the relationship between cholesterol and these fats. Generally, low-cholesterol diets help the liver clear both LDL and VLDL and keep their levels low. With cholesterol-heavy diets, the clearance of VLDL decreases and both LDL and HDL production increase. Diet should always be personalized and depends on numerous other factors, your overall health status, and food sensitivities [3, 3].
But LDL and HDL levels are much more important to analyze. However, even these values are only somewhat loose indicators of health. Two people with the same cholesterol levels may differ up to 4.5 times in their risk of stroke, depending on other factors like genetics, diet, blood pressure, other diseases, and smoking .
Below are LDL guidelines for people with low risk of heart disease .
- Normal: 100-129 mg/dL
- Borderline high: 130-159 mg/dL
- High: 160-199 mg/dL
- Very high: > 200 mg/dL
Recommendations encourage LDL levels < 70 mg/dL for individuals with high heart disease risk .
Higher HDL cholesterol levels have been repeatedly shown to protect against cardiovascular disease, so low levels of HDL will increase your risk. Low levels of HDL may also contribute to inflammation and metabolic diseases such as type 2 diabetes [15, 16, 17, 18].
Cholesterol levels are very tightly regulated by the body. Therefore, slightly and temporarily increased cholesterol is usually not a problem. Consistently increased cholesterol levels, on the other hand, can be dangerous.
This will be problematic if LDL is high as well. A buildup of LDL can clog arteries and lead to poor circulation in the heart, brain, and rest of the body. Eventually, LDL can completely block arteries and lead to a heart attack or stroke [1, 20, 8, 20, 8].
- Cholesterol gallstones
- Liver dysfunction
- Irregular yellow patches on the skin (xanthomas)
- Alzheimer’s disease
- Chest pain (angina pectoris)
- Vision problems
- Clogging of blood vessels that supply the brain
Although we know much less about unhealthy lower cholesterol ranges, < 140 mg/dL of total cholesterol may produce negative effects .
Since cholesterol is important for brain cell communication, very low levels have been linked to mental health problems. In a study of 394 people, those will low cholesterol were 3 times more likely to suffer from depression. Other studies linked low levels to increased suicidality, but only in men. Other studies found links between low cholesterol and antisocial personality disorders and anxiety[24, 25, 26, 27, 28, 29, 30].
Aside from effects on the brain, very low cholesterol has been linked to cancer. In a study of 12k people, those with low cholesterol levels (< 159 mg/dL) had higher chances of developing cancer. In another study of 70k people, those with higher LDL levels had a 43% decreased risk of developing cancer [23, 33, 34].
Low levels in childhood can lead to a wide variety of different syndromes, which are mainly due to genetic problems in creating cholesterol. Dietary cholesterol supplements may help in such cases [35, 35].
What Increases Cholesterol?
Diet is perhaps the biggest and most diverse contributor for most people. One’s diet plays a crucial role in balancing cholesterol. High levels of saturated fat can increase blood cholesterol levels dramatically. This increase is worsened by obesity .
The body has many protective mechanisms to stop drastic increases in cholesterol. The health risks due to high cholesterol levels take many years to develop and are a result of eating high-fat foods consistently .
The main sources of cholesterol come from eggs, dairy products, and meat. It is estimated that 24.6% of the total cholesterol intake in the U.S. diet comes from eggs. Chicken and beef make up 12.5% and 11%, respectively .
Whether cholesterol from the diet can cause heart disease is still unclear. According to a large meta-analysis (of 40 studies and 362k patients), it may not. In the U.S., it’s still not recommended to consume more than 300 mg/day of cholesterol [37, 38].
Lifestyle factors such as smoking can also influence cholesterol levels. Quitting smoking can increase HDL levels by 24 times, as seen in a study of 1.5k smokers .
Lack of Exercise
Some people have reduced activity of genes that break down cholesterol (ATP-binding cassette (ABC) transporters). This can increase cholesterol levels and a lower response to cholesterol medication .
Familial hypercholesterolemia is a heritable disease that is caused by mutations in several genes, including those that make :
- The LDL receptor
- Apolipoprotein B
It causes problems in clearing LDL .
Additionally, your Apolipoprotein E (APOE) variants can have a large impact on your cholesterol and triglyceride levels, aside from affecting your Alzheimer’s risk. APOE helps transport fats in the blood. A well-functioning APOE lowers cholesterol levels, reduces heart disease risk, supports brain health, and decreases excessive inflammation. Your variants can also impact the type of diet that might work better for you, along with other factors like your labs, health status, and food tolerances.
Underactive Thyroid & Kidney Problems
How to Lower Cholesterol
Lifestyle modifications can go a long way in helping maintain healthy levels of cholesterol. In one study of 923 adult smokers, quitting smoking increased HDL levels by 2.4 mg/dL .
A study comparing women smokers and non-smokers also found that smokers had greater total cholesterol levels (197 mg/dL vs. 189.1 mg/dL) and had lower HDL levels (45 mg/dL vs. 52.1 mg/dL) .
Increasing exercise can reduce cholesterol levels. In a study of 123 children, increasing exercise helped increase HDL levels, while decreasing LDL and total cholesterol .
The same effect is seen in adults. A meta-analysis of 51 studies and 4,700 adults found that aerobic exercises such as jogging, running, and biking increased HDL by 4.6% and decreased LDL by 5%. Another study (RCT) of 235 adults showed that exercise also decreased total cholesterol [47, 48, 49].
The right diet can cause significant weight loss. In a study (DB-RCT) of 384 patients, weight loss caused total cholesterol levels to decrease by 25 to 30 mg/dL .
Remember, there is no one-diet-fits-all. You’ll need to experiment with healthy diets, track your labs and responses, and consult your doctor (especially if you’re on prescription medication).
Step 2 diet
A healthy diet is crucial to weight loss. The American Heart Association Step 2 diet, which consists of increasing fish, vegetable, fruit, and low-fat dairy products while decreasing salt and alcohol intake, lowers total cholesterol. This diet also reduces LDL by up to 20% [51, 52, 53].
Low Cholesterol and Low Saturated Fat Diet
With low-cholesterol diets, the liver rapidly clears both LDL and VLDL, so LDL levels in the blood remain low .
In a study of 155 adults, replacing saturated fats with polyunsaturated fats for eight weeks reduced LDL by 10% .
Reducing saturated fat intake lowered LDL in children in a meta-analysis .
In a study of 8,433 people, a “healthy” diet was associated with lower LDL. This diet included high intake of whole grains, fruit, dairy, vegetables, and unsaturated oil, and low intake of fast food, sugary beverages, poultry, processed meat, and flavored rice .
High Monounsaturated Fat (MUFA) Diet
In a study (DB-RCT) of 22 healthy adults, consuming any of three high-MUFA diets (using either olive oil, peanut oil, or peanuts and peanut butter) lowered LDL by 14% on average. These diets also reduced LDL oxidation compared to a standard American diet [59, 60].
Consuming a moderate-MUFA diet (10% of calories from MUFAs) and high-MUFA diet (14% of calories from MUFAs) both lowered LDL in a study of 35 participants with high cholesterol. The high-MUFA diet produced the greatest benefits .
Reducing stress can help lower cholesterol levels. In a study of 26 adults, increased mental stress increased total cholesterol levels. The cholesterol remained high even once the stress went away, pointing to long-term consequences .
Another study of 40 college teachers and 40 housewives compared the stress levels between the 2 groups. The housewives showed greater environmental, psychological, and physiological stress, which caused higher total cholesterol and LDL levels .
Cut Down on Alcohol
Alcohol intake may increase oxidized LDL but is also associated with lower overall LDL levels.
In a study of 587 adults, alcohol consumption was positively associated with oxidized LDL .
Moderate wine drinking may be an exception. Wine is rich in resveratrol and drinking about a glass of wine a day generally reduces heart disease risk. Additionally, wine intake was linked to reduced oxidized LDL in a study of 551 older Italian adults .
In a study (DB-RCT) of 30 adults, taking 3 grams of soluble fiber supplements daily for 12 weeks decreased LDL by 18% .
A meta-analysis (of 17 RCT studies) showed that beta-glucan consumption of more than 3g/day reduces LDL by 8 mg/dL in people with high cholesterol .
In a meta-analysis (of 21 RCT studies and 1,717 people with high cholesterol), psyllium (3 – 20.4 g/day) reduced LDL by an average of 11 mg/dL .
In a study (RCT) of 68 adults, adding 15 g of psyllium to cholesterol-lowering medication was as effective as taking more medication without psyllium .
Black and Green Tea
In a meta-analysis (of 39 RCT studies and 2,298 subjects with high cholesterol), consuming garlic for at least 2 months decreased LDL 9 mg/dL on average .
Most studies used garlic powder (600–5,600 mg/day), while some used garlic oil (9 – 18 mg/day), garlic extract (1000–7200 mg/day), and raw garlic (4 – 10g/day). Aged garlic extract had the strongest effects .
In a study (RCT) of 40 older adults, daily consumption of a beverage made up of various berries lowered LDL .
In a study (DB-RCT) of 30 type 2 diabetes patients, cranberry extract lowered LDL .
Berries can also lower oxidized LDL. Frozen berries (bilberries, lingonberries, black currants) lowered oxidized LDL in a study (RCT) of 60 healthy adults .
In a study of 21 healthy men, drinking cranberry juice daily for 2 weeks lowered oxidized LDL .
The average effective dose is 1.6 g/day, with the largest effects at around 3 g/day .
According to a meta-analysis (of 13 RCT studies), taking at least 500 mg/day of vitamin C for at least 4 weeks lowered LDL by 7.9 mg/dL on average .
Taking 150 mg of coenzyme Q10 daily for 2 weeks lowered LDL by 12.7% in a study of 53 healthy men. Importantly, coenzyme Q10 also reduced unhealthy (small, dense) LDL particles .
In a study (DB-RCT) of 100 healthy adults, taking 200 mg/day of coenzyme Q10 for 1 week removed cholesterol from immune cells (macrophages). This improves blood flow by shrinking the fatty plaques in the arteries .
As a supplement to standard therapy, 1 g/day of curcumin lowered LDL in a study (RCT) of 100 patients with high heart disease risk .
Black cumin (Nigella sativa) lowered LDL by an average of 22 mg/dL according to a meta-analysis (of 7 studies) .
Spirulina consumption greatly reduced LDL – by 41 mg/dL on average – according to a meta-analysis (of 7 RCT studies and 522 people). The Spirulina doses were between 1-10 g/day, taken for 2-12 months. Longer supplementation, but not dose, was linked with reduced LDL .
Note: We at SelfHacked are not advocates of cholesterol-lowering drugs. We are providing information from the scientific literature, as requested by our readers who were prescribed these drugs.
Please discuss your medication with your doctor.
If your cholesterol levels are high, your doctor is most likely to prescribe statins. Statins decrease the amount of cholesterol the liver makes, increase LDL uptake in the liver, and raise HDL cholesterol [8, 4].
Therapies that reduce cholesterol can cause side effects. Statins can cause muscle pain (myalgia) or inflammation (myositis) in 8 to 9% of patients .
Statins may also increase the risk of type 2 diabetes, as seen in a meta-analysis of 13 trials and 91k patients .
If you have been prescribed cholesterol-lowering drugs and experience side effects, contact your healthcare provider.