Cholesterol

food

Poor cholesterol—so misunderstood. All animal cells require cholesterol for proper structure and function. The vast majority of cholesterol in the body does not come directly from foods like eggs and meat, but from the liver, which can make cholesterol out of anything we eat. So, if cholesterol-rich foods don’t cause high cholesterol, what does?

WHAT IS CHOLESTEROL?

Most people have no idea what cholesterol actually is.

Life without cholesterol would be impossible. Cell membranes, which wrap around and protect the inner contents of all cells, must contain cholesterol in order to function properly. Cholesterol contributes firmness to membranes and keeps them from falling apart. But wait, there’s more!

All of the following critical body components are made from cholesterol:

  • Estrogen
  • Testosterone
  • Progesterone
  • Cortisol (anti-inflammatory stress hormone)
  • Aldosterone (regulates salt balance)
  • Vitamin D
  • Bile (required for fat and vitamin absorption)
  • Brain synapses (neurotransmitter exchange)
  • Myelin sheath (insulates nerve cells)

WHAT IS THE DIFFERENCE BETWEEN FAT AND CHOLESTEROL?

Cholesterol is made of carbon, hydrogen, and oxygen, just like fat is, but it is not fatty; it is a hard, waxy substance that contains no fat. A molecule of fat looks like this:

whereas a molecule of cholesterol looks like this:

As you may be able to appreciate just by looking at them, they are very different from each other.

Fat is a simple long chain, whereas cholesterol is mainly a complicated combination of rings—3 hexagons plus a pentagon; in medical school we affectionately called it “three rooms and a bath.” Fat is relatively easy to build (11 chemical steps from acetyl-coA to triacylglycerol), whereas cholesterol is hard to construct—more than 30 chemical steps are required to build one molecule of cholesterol (from acetyl-coA to cholesterol). The body would not go to the trouble of making it for no reason. Especially since, as it turns out, once it’s built, it’s impossible for the body to break it down—we do not have any way to take apart its complex ringed structure.

CHOLESTEROL IN FOODS

How much cholesterol do we need to eat?

NONE.

Cholesterol is so important that the body can make cholesterol out of ANYTHING—fats, carbohydrates, or proteins. You don’t have to eat cholesterol to make cholesterol. Even if you eat a completely cholesterol-free diet, as vegans do, your body will still make cholesterol. Type “vegans with high cholesterol” into your search engine and you will find plenty of accounts of vegans whose cholesterol is too high—despite the fact that they eat ZERO grams of cholesterol.

Which foods contain cholesterol?

Since every single animal cell contains cholesterol, all animal foods contain cholesterol.

Many people don’t realize that all muscle meats (chicken, fish, beef, pork, etc.) contain about the same amount of cholesterol per serving.

Certain animal foods—liver, egg yolk, dairy fats, glandular organ meats, and brain— are especially high in cholesterol.  Why is that?  Liver is where the body manufactures cholesterol. Egg yolks contain concentrated cholesterol because the growing baby chick needs it to build new cells. Milk fat contains lots of cholesterol because the growing baby calf needs it to build new cells. Glandular organ meats (pancreas, kidney, etc.) contain more cholesterol because glands make hormones, and hormones are made from cholesterol. Brain contains very high amounts of cholesterol in its myelin sheaths, which insulate its electrical circuits.

All plant foods are considered “cholesterol-free.” Well, it would be more accurate to say that plant foods do not contain any animal cholesterol. Plants contain their own special forms of cholesterol called “phytosterols”, but phytosterols are toxic to human cells, so our intestines wisely refuse to absorb them.

So, in most cases, animal foods contain some cholesterol that the body can absorb and use, and all plant foods contain cholesterol that our body cannot absorb. The only exceptions I know of to these rules are shellfish.

There are two types of shellfish: crustaceans (lobsters, shrimp, crabs, etc.) and mollusks (clams, oysters, mussels, etc.). Crustaceans—giant sea insects who hunt for their food—contain animal cholesterols that can be absorbed by the body, but mollusks—who gather nutrients by filtering seawater—contain a different type of cholesterol that we can’t absorb.

In fact, plant cholesterols and mollusk cholesterols are not only rejected by our intestinal cells, they actually interfere with the absorption of animal cholesterols. This is how margarines such as Benecol® work. The manufacturer has added a chemically altered form of plant cholesterol to the spread, which interferes with the absorption of animal cholesterol.

WILL EATING CHOLESTEROL RAISE MY CHOLESTEROL?

Yes, but only if your body needs more cholesterol.

The cells lining the small intestine each contain transporter molecules (NPC1L1) that absorb cholesterol. [The cholesterol-lowering drug Zetia® works by blocking NPC1L1 yet does not reduce risk of heart disease]. However, if the body does not need any more cholesterol, there is another molecule (ABCG4a) that pumps the cholesterol right back out into the intestines to be eliminated from the body. This is one reason why it is virtually impossible for cholesterol from food to cause “high cholesterol.” The intestinal cells know exactly how much is needed and will not allow extra to be absorbed.

This is brilliant when you think about it (the body is so smart)—it is impossible for the body to break down the complex structure of the cholesterol molecule, so it would make no sense to absorb too much—once it’s inside the body there’s only one way to get rid of it, and that is to excrete it in the bile. Why take in more than necessary, if it’s just going to have to be eliminated?

However, if your body cholesterol levels are low, the intestinal cells will not kick it out, and it will make it into your bloodstream—because you need it.

What’s more, cholesterol is recycled very efficiently by our bodies, because it is so hard to make. Why make more from scratch if you don’t have to? Remember that it’s also impossible for the body to break down cholesterol, so the only way to get rid of it is to excrete it. The liver gets rid of any excess by excreting free cholesterol into the intestines along with bile. This free form of cholesterol is the only form that intestinal cells are able to absorb. Most of the cholesterol molecules in food (85 to 90% of them) are not free; they are in the form of “cholesterol esters.” [Cholesterol esters are just cholesterol molecules with a fatty acid attached]. Intestinal cells are incapable of absorbing cholesterol ester, which is the major form of cholesterol in food. Therefore, if the intestinal cells sense that the body needs more cholesterol, it will typically reabsorb most of what the body needs from the bile, not from food.

To summarize the relationship between food cholesterol and blood cholesterol:

  1. Most cholesterol from foods does not get absorbed unless body levels are low.
  2. The amount of cholesterol you eat has almost no effect on your cholesterol levels.
  3. The vast majority of cholesterol in your body is made by your body’s own cells. Remember that creepy line from the movie When a Stranger Calls? “The call is coming from inside the house.” The excess cholesterol is coming from inside your body, not from the food you eat.

How does the body make cholesterol?

All cells can make their own cholesterol, but liver cells are especially good at it. Only liver cells are capable of making more than they need for themselves—and shipping it out to other parts of the body.

Remember how it takes more than 30 chemical reactions to build one molecule of cholesterol? The most important of all of these steps is step #3. In this step, a critical enzyme called “HMG-CoA reductase” converts a molecule called HMG-CoA into another molecule called mevalonate. Once this step occurs, there’s no turning back, so it’s a big commitment. This reaction is the one that determines whether or not cholesterol gets made. Therefore, the enzyme that runs this reaction, HMG-CoA reductase, is very important—it’s like the foreman in charge of the cholesterol assembly line. This enzyme needs to be carefully controlled, because we don’t want cells wasting their time and energy building expensive cholesterol molecules willy-nilly.

The activity of this critical enzyme HMG-CoA reductase is controlled primarily by two things:

1) cholesterol levels inside the cell

2) insulin levels in the blood.

This is where things get really interesting. It makes sense that HMG-CoA reductase would respond to the cell’s cholesterol levels—if the cell’s levels are low, you want to turn that enzyme on, so you can make more cholesterol, and if the cell has enough cholesterol, you want to turn that enzyme off and stop making cholesterol. But what is insulin doing in the mix?

We think of insulin as a blood sugar regulator, but its real job is to be a GROWTH HORMONE. Insulin is supposed to turn on when we need to grow. What do we need to make in order to grow? More cells. What do we need to form new cells? Cholesterol. So, at times when we need to grow (babies, teenagers, pregnant women), insulin turns the enzyme HMG-CoA reductase ON, which tells cells to make more cholesterol, so we can build new cells.

What causes high cholesterol?

Why would the body make more cholesterol than it needs?

Now here’s the problem: when people eat too many sugars and starches, especially refined and high glycemic index foods, blood insulin levels can spike. When insulin spikes, it turns on HMG –CoA reductase, which tells all of the body’s cells to make cholesterol, even if they don’t need any more. This is probably the most important reason why some people have too much cholesterol in their bloodstream. Sugars and starches can raise insulin levels, which fools the body into thinking it should grow when it doesn’t need to. This is how low glycemic index diets and low-carbohydrate diets lower LDL levels—these diets reduce insulin levels, which in turn lower HMG-CoA reductase activity.

“Statin” drugs, such as Lipitor®, which are prescribed to lower cholesterol levels, work partly by interfering with the activity of HMG-CoA reductase. If your cells happen to need more cholesterol under certain circumstances, but the statin drug is blocking this critical enzyme, your cells may not be able to make cholesterol when needed. And what’s worse is that the cholesterol synthesis pathway doesn’t just make cholesterol; branches of this same pathway are responsible for synthesizing a wide variety of other important molecules, including: Vitamin A, Vitamin E, Vitamin K, and Coenzyme Q. So, you may want to think twice before you artificially interfere with this pathway by taking a statin drug.

When you eat less carbohydrate, you are not artificially blocking the pathway; you are simply allowing HMG-CoA reductase to listen to other more important signals (such as cholesterol levels and growth requirements) and decide naturally when it should turn on and when it should turn off.

So, to recap: refined carbohydrates speed up the cholesterol assembly line and statins slow it down. Which approach would you rather take to manage your “cholesterol problem”—taking a drug that artificially slows down this assembly line, or changing your diet so that the assembly line only runs when it’s supposed to? [Hint: Dietary changes require no monthly co-pays, and have no potentially dangerous side effects.]

Chances are: if you have “high cholesterol” you do not have a cholesterol problem—you have a carbohydrate problem.

Good Cholesterol and Bad Cholesterol

This gets into the very complicated relationship between cholesterol blood tests and heart disease risk. This is an enormous topic that will be covered in future articles on this site. I’ll summarize some basic points here now, but please stay tuned for more detailed information.

“Good” cholesterol = HDL

HDL particles collect extra cholesterol from around the body and carry it back to the liver to be eliminated from the body if we don’t need it.

“Bad” cholesterol = LDL

LDL particles carry extra cholesterol made in the liver out to the rest of the cells in the body.

The cholesterol inside of HDL and LDL particles is exactly the same, it’s just that, for the most part, HDL is carrying it in one direction and LDL is carrying it in the opposite direction. The reason why LDL has been dubbed “bad” and HDL has been dubbed “good” is that numerous epidemiological studies (most famously, the Framingham Heart Study) tell us that high LDL levels are associated with a higher risk of heart attack, and that high HDL levels are associated with a lower risk of heart attack.

We used to think that HDL was good because it acted like a garbage truck, clearing evil cholesterol out of our bodies, and we used to think that LDL was bad because it burrowed its way into our coronary arteries, depositing evil cholesterol there—forming plaques and causing heart attacks.

Cholesterol, Carbohydrates and Heart Disease

However, this simplistic way of thinking about cholesterol and heart disease is changing before our very eyes. It turns out that it is more complicated than this. LDL, for example, exists in a variety of forms. It can be big and buoyant or small and dense. The new thinking is that small, dense, oxidized LDL may be the only type of LDL that is associated with heart disease.  Therefore, instead of thinking of all LDL as “bad”, it would be more accurate to say that all LDL is not created equal—big fluffy LDL is “good” and small, dense, oxidized LDL is “bad.”

Unfortunately, standard blood tests can’t tell you which type of LDL you have because it lumps all types of LDL particles together.  Standard tests can only estimate how much of your cholesterol is travelling inside of LDL particles.  They can’t tell you how many LDL particles you have, how big they are, how dense they are, or how oxidized they are.  [For a detailed explanation of the complexities involved in interpreting cholesterol blood test results, I recommend Dr. Peter Attia’s blog at www.eatingacademy.com.]

What we do know from research studies is that people who eat a diet high in refined carbohydrates tend to have a higher number of “bad” (smaller, denser, oxidized) LDL particles. This makes sense, because we know that carbohydrates are “pro-oxidants” —meaning they can cause oxidation.

There is also lots of evidence telling us that refined carbohydrates can cause inflammation.  Just because doctors find cholesterol inside artery-clogging plaques does not mean that cholesterol causes plaques. It is now well established that heart disease is a disease of inflammation. It is not simply that an innocent, smooth, buoyant sphere of fat and cholesterol traveling through the bloodstream decides to somehow randomly dig its way into a healthy coronary artery. The first step in the development of a vessel-clogging plaque is inflammation within the lining of the artery itself. When doctors cut into plaques they don’t just find cholesterol—they find many signs of inflammation (such as macrophages, calcium, and T cells). Wherever there is inflammation in the body, cholesterol is rushed to the scene to repair the damage—because we need cholesterol to build healthy new cells. Jumping to the conclusion that coronary artery plaques are caused by the cholesterol found inside of them is like assuming that all car accidents are caused by the ambulances that are found on the scene.

The latest research suggests that diets high in refined and high glycemic index carbohydrates increase the risk of inflammation throughout the body, especially in blood vessels. Diabetes, a disease which is intimately associated with high blood sugar levels, is infamous for causing damage to blood vessels in the retina, kidneys, and tiny vessels that feed nerve endings in the feet. It is well established that people with diabetes are also at higher risk for heart disease. It should therefore not be a stretch for us to imagine that all people with high blood sugar and/or insulin levels due to diets rich in refined carbohydrates may also be at increased risk for cardiovascular disease.

Cardiology researchers are now turning away from the notion that saturated fat and cholesterol cause heart disease. After all, how could saturated fat and cholesterol, which we have been eating for hundreds of thousands of years, be at the root of heart disease, which is a relatively new phenomenon? Cardiologists are finding instead that refined carbohydrate (such as sugar and flour), which we have only been eating in significant quantities for about a hundred years, is the single most important dietary risk factor for heart attacks:

“Strong evidence supports …associations of harmful factors, including intake of trans-fatty acids and foods with a high glycemic index or load.”

“Insufficient evidence of association is present for intake of…saturated and polyunsaturated fatty acids; total fat,… meat; eggs; and milk.” [Mente et al 2009].

Sweetheart?  

There are several plausible mechanisms for how refined carbohydrate could increase risk for heart disease and change cholesterol profiles:

  • Diets high in refined carbohydrate lower HDL levels and set the stage for high insulin levels, oxidation, and inflammation throughout the body, including in the coronary arteries.
  • High blood sugar and insulin levels turn big, fluffy, innocent LDL particles into small, dense, oxidized LDL particles, which are associated with increased risk for heart disease.
  • High insulin levels turn on the cholesterol building enzyme HMG-CoA reductase, forcing the body to make more cholesterol than it needs.

It is becoming increasingly obvious that cholesterol is innocent until corrupted by refined carbohydrate.

Coming soon for Valentine’s Day:  an exposé of CHOCOLATE!

[To be notified of new blog posts as they become available, please sign up in the registration are at the upper right hand side of this page.]

References

[1]
Barclay AW et al. Glycemic index, glycemic load, and chronic disease risk—a meta-analysis of observational studies. Am J Clin Nutr 2008; 87: 627–37.
[2]
Boden G et al. Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes. Annals of Internal Medicine 2005; 142: 4030441.
[3]
Brownlee M. The pathology of diabetic complications: a unifying mechanism. Diabetes 2005; : 1615-1625.
[4]
Djoussé L, Gaziano JM.. Dietary cholesterol and coronary artery disease: a systematic review. Atheroscler Rep 2009; 11(6): 418-22.
[5]
Eaton SB et al. Stone agers in the fast lane: chronic degenerative diseases in evolutionary perspective. Am J Med 1988; 84: 739-749.
[6]
Esposito K et al. Inflammatory cytokine concentrations are acutely increased by hyperglycemia in humans: role of oxidative stress. Circulation 2002; 106: 2067-2072.
[7]
Greco TP et al. xidized-LDL/beta(2)-glycoprotein I complexes are associated with disease severity and increased risk for adverse outcomes in patients with acute coronary syndromes. Am J Clin Path; 133: 737-743.
[8]
Halton TL et al. Low carbohydrate diet score and risk of cardiovascular disease in women. New England Journal of Medicine 2006; 355: 1991-2002.
[9]
Jakobsen MU et al. Intake of carbohydrates compared with intake of saturated fatty acids and risk of myocardial infarction: importance of the glycemic index. Am J Clin Nutr 2010; 91: 1764-8.
[10]
Mente A et al. A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Archives of Internal Medicine 2009; 169(7): 659-69.
[11]
Siri-Tarino PW et al. Saturated fat, carbohydrate, and cardiovascular disease. Am J Clin Nutr 2010.
[12]
Welsh JA et al. Caloric sweetener consumption and dyslipidemia among US adults. JAMA 2010; 303(15): 1490-1497.
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Westman EC et al. Low-carbohydrate nutrition and metabolism. Am J Clin Nutr 2007; 86: 276-84.
[14]
Willett, W. The Great Fat Debate: Total Fat and Health. J Am Diet Assoc 2011; 111(5): 660-662.
  • bill

    Your 4 part series is very well presented. Thank you for doing this.

    • http://diagnosisdiet.com/ Dr. Ede

      Thanks for reading it, Bill; I’m so glad you liked it.

  • Judith

    Why would someone who went from years on a major junk food diet (living on crackers, cakes, cookies, soda, noodles and occasionally a decent meal) actually have a significant increase in total cholesterol (from 240 to 280) and LDL cholesterol (from 160 to 180) even 2 years after following a clean, low carb diet with no weight loss in the past 1 year? (60 pounds were lost the first year.) HDL hasn’t changed from about 55. Fasting triglycerides have ranged up and down between 50 and 170 during this time. Fasting blood glucose is normal (87) and fasting insulin is 10. Daily total carb intake averages 30-50 grams.

    • http://diagnosisdiet.com/ Dr. Ede

      Hi Judith
      It is actually fairly common for LDL (and total) cholesterol to rise on a low-carb diet, and it is not usually any cause for concern. As noted in the above article, LDL is a poor indicator of heart disease risk and overall health because it exists in various forms that are not routinely tested for. Triglycerides and HDL are more helpful indicators. High cholesterol is not generally a sign of trouble if everything else looks ok.

      • Judith

        Thank you. My doctor has suggested a statin drug, but I have declined due to concerns about the side effects. The only other concern is that my blood pressure has been hard to get and keep down. I don’t take anything for it, but I’m hoping to resolve somewhat high bp other ways, such as supplements. Everything else is normal.

        • http://diagnosisdiet.com/ Dr. Ede

          Hi Judith
          Please do not think of my reply as medical advice for your particular situation, only as a general response about cholesterol patterns on low-carb diets. It would be wise to find a physician who understands the new science behind diet and cholesterol to guide you–luckily they are growing in number.

  • Erika

    Hi Dr. Ede,

    Love the website!! It is really fun browsing around.

    So my husband has high cholestorol. Period. We are toying with the idea of ketogenic diet as a way to address this. However, if he does this diet strictly for let’s say, 3 months, his cholestorol profile will still be high when they check it. Correct? Is there a test that can differentiate the good and bad cholestorol in your body?

    Cheers!

    • http://diagnosisdiet.com/ Dr. Ede

      Hi Erika

      Glad you are enjoying the website–thanks for the positive feedback! Does your husband simply have high LDL or does he also have high triglycerides and low HDL? It is true that low-carbohydrate diets, including ketogenic diets, do not tend to lower LDL for many people, but they do tend to improve HDL and triglyceride levels. Yes, there are tests that can differentiate between good and bad LDL cholesterol. In fact, I had my own cholesterol fractionated recently with a test my doctor ordered called a VAP cholesterol panel, and will be posting the results next week as part of my ketogenic diet month 2 update. Your husband may not need to go to the extreme of a ketogenic diet to improve his profiles–he may simply need to try a low glycemic index diet or a low-carbohydrate diet. Cheers to both of you, too!

  • justmeint

    Have been sharing this easy to read – what I have called Cholesterol 101 with many people who are considered statin damaged. Doctors insist on prescribing and telling people to eat less fat. They do not understand nutrition at all :-(
    Thanks for the work you are doing.

  • Keith Taylor

    Dear Dr. Ede,
    I have found this website only now, but better late than never, as the saying goes. I am a strong proponent of a high animal fat and animal protein diet. The reason is that I literally “took my life into my own hands” when the medications and diet prescribed for a diagnosed angina pectoris appeared to make it WORSE! I switched to high fat and sufficient animal protein … and the angina “attacks” stopped almost immediately. It is now more than six years later and I need no medication at all.
    Thank you for a truly well-informed website: I will link to it in my blog.

    • http://diagnosisdiet.com/ Dr. Ede

      Hello, Keith
      What a fabulous story–thank you so much for sharing it here with us! I am so glad you are finding the website helpful.

  • Jason

    Hi I was reading your site n found it very informativw. I have had low cholesterol for a while at 122, my hdl is 34 ldl 74 and triglycerides are 68. I eat a high protein n low carb diet. My hormones are hurting bc of it I think. Do u know reasons why its low or could it be something more serious. I was told it should be at least 160-180. Thank you
    Jason

    • http://diagnosisdiet.com/ Dr. Ede

      Hi Jason

      I can’t be sure, but you say that you eat a high protein, low carb diet, without mentioning how much fat you eat. It is possible that you are simply not eating enough fat…but more importantly, cholesterol levels are a terrible measure of health, especially LDL levels, so the question is whether you are healthy and feel well or not. I’m glad you are finding the website informative!

  • erin

    Hypocholesteremics will be dangerously misled by this. You need to change this and explain some people do not make enough cholesterol

  • 777serenity

    I started the 100 because I have been trying for years to find a way to lower my blood pressure and lose weight with out prescribed medicine. My doctor never had any solutions to my high blood pressure except to prescribe medicines with side effects The 100 specifically controls sugar carbs. I still eat carbs but this way has lowered my blood pressure and sugar cravings. I am losing weight at a healthy rate, have lost 20 pounds and still losing. I don’t get sleepy anymore after lunch. I can’t explain the sense of well being I feel physically. This website has explained so much to me about cholesterol that I will never hear in the mainstream heart disease protocol. I have been passing your message on. People I love need to know this.

Last Modified: Jan 29, 2013 at 6:56pm