Foods For A Diet: Number

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Tuesday, May 21, 2013

The Diet-Heart Myth: Why Everyone Should Know Their LDL Particle Number

cholesterol test

To read more about heart disease and cholesterol, check out the special report page.

Cardiovascular disease is one of the most misdiagnosed and mistreated conditions in medicine. In the first article in this series, I explained the evidence suggesting that eating cholesterol and saturated fat does not increase cholesterol levels in the blood for the majority of the population.

In this article, I will debunk the myth that high cholesterol in the blood is the cause of heart disease.

Part of the confusion about cholesterol and its role in heart disease is caused by imprecise terminology. So, before I explain why high cholesterol is not the underlying cause of heart disease, we have to cover some basics.

Cholesterol is not technically a fat; rather, it’s classified as a sterol, which is a combination of a steroid and alcohol. It’s crucial to understand that you don’t have a cholesterol level in your blood. Cholesterol is fat-soluble, and blood is mostly water. In order for cholesterol to be transported around the body in the blood, it has to be carried by special proteins called lipoproteins. These lipoproteins are classified according to their density; two of the most important in cardiovascular disease are low-density lipoprotein (LDL) and high-density lipoprotein (HDL).

I know this can get confusing quickly, so let me use an analogy to make this more clear. Imagine your bloodstream is like a highway. The lipoproteins are like cars that carry the cholesterol and fats around your body, and the cholesterol and fats are like passengers in the cars. Scientists used to believe that the number of passengers in the car (i.e. concentration of cholesterol in the LDL particle) is the driving factor in the development of heart disease. More recent studies, however, suggest that it’s the number of cars on the road (i.e. LDL particles) that matters most.

The crucial test for heart disease risk you’ve probably never heard of.

Coronary arteries are essentially hollow tubes, and the endothelium (lining) of the artery is very thin—only one cell deep. The blood, which carries lipoproteins like LDL, is in constant contact with the endothelial lining. So why does the LDL particle leave the blood, penetrate the endothelium and enter the artery wall? The answer is that it’s a gradient-driven process. Going back to our analogy, the more cars there are on the road at one time, the more likely it is that some of them will “crash” into the fragile lining of the artery. It’s not the number of passengers (cholesterol) the cars are carrying that is the determining factor, but the number of cars on the highway.

The significance of this in terms of determining your risk of heart disease is profound. When you go to the doctor to get your cholesterol tested, chances are he or she will measure your total, LDL and HDL cholesterol. This tells you the concentration of cholesterol (passengers) inside of the lipoproteins (cars), which is not the driving factor behind plaque formation and heart disease. Instead, what should be measured is the number of LDL particles in your blood.

LDL cholesterol levels and LDL particle number are often concordant (i.e. when one is high, the other is high, and vice versa), and this is probably why there is an association between LDL cholesterol and heart disease in observational studies. The elevated LDL cholesterol was more of a proxy marker for elevated LDL particle number in these cases. But here’s the kicker: they can also be discordant. In layperson’s terms, it’s possible to have normal or even low cholesterol, but a high number of LDL particles. (1) If this person only has their cholesterol measured, and not their particle number, they will be falsely led to believe they’re at low risk for heart disease. Even worse, the patients that are the most likely to present with this pattern are among the highest risk patients: those with metabolic syndrome or full-fledged type 2 diabetes. The more components of the metabolic syndrome that are present—such as abdominal obesity, hypertension, insulin resistance, high triglycerides and low HDL—the more likely it is that LDL particle number will be elevated. (2)

On the other hand, patients with high LDL cholesterol (LDL-C) and low LDL particle number (LDL-P) are not at high risk of heart disease. In fact, studies suggest they’re at even lower risk than patients with low LDL-C and low LDL-P. (3) Yet they will often be treated with statin drugs or other cholesterol lowering medications, because the clinician only looked at LDL-C and failed to measure LDL particle number. This is a concern for two reasons. First, statin drugs aren’t harmless. (I’ll go into more detail on this in the third post of the series.) Second, studies suggest that low cholesterol can increase the risk of death, especially in women and the elderly.

In one study of over 52,000 Norwegians, researchers found that women with total cholesterol levels below 195 mg/dL had a higher risk of death than women with cholesterol levels above that cut-off. (4) And a study published in the American Journal of Medicine found that people over 70 years of age with total cholesterol levels below 160 mg/dL had twice the risk of death than those with cholesterol levels between 160-199 mg/dL. (5) Low cholesterol is also associated with increased risk of disease—especially mental health and brain disorders. For example:

A study in the Journal of Psychiatric Research found that men with low total cholesterol levels were 7 times more likely to die prematurely from unnatural causes such as suicide and accidents than other men in the study. (6)A 1993 study published in The Lancet found that depression was 3 times more likely in men over 70 with low cholesterol than in those with normal or high cholesterol. (7)A Swedish study found that women with the lowest cholesterol suffered significantly more depressive symptoms than other women in the study. (8)A study in the journal Neurology showed that low cholesterol is associated with increased risk of dementia. (9)A paper published in the European Journal of Internal Medicine linked low cholesterol levels with Alzheimer’s disease. (10)

It’s important to note that all of these studies were observational, which means that they don’t prove that low cholesterol was the cause of the increased risk of death or disease that was observed. It’s possible, for example, that these patients had another disease that caused both the lower cholesterol and increase in disease or mortality. However, given what we know about the important roles of cholesterol in the body, it’s certainly plausible that low cholesterol is capable of contributing to these problems directly.

Before concluding, I’d like to point out that although LDL particle number is superior to LDL cholesterol as a marker for heart disease, it’s still just that—a marker. A marker is not a disease. It’s a risk factor for a disease. Having a risk factor for a disease does not guarantee that you will get that disease—it just increases the chance that you will. There are still several gaps in our knowledge about LDL-P and its usefulness in a clinical setting. For example:

Imagine two people with an LDL-P above 2,000, which puts them in the highest risk group. Person A follows a Paleo diet and lifestyle, gets plenty of sleep, manages stress and has no other significant risk factors for heart disease. Person B eats a Standard American Diet, doesn’t exercise, doesn’t get enough sleep, is stressed out and has several other risk factors for heart disease. Logic would dictate that Person A would be at much lower risk for heart disease than Person B, but there isn’t any comparative data to quantify the difference in risk and it’s unlikely such a study will ever be done. (Who would pay for it?)Imagine two people following a healthy Paleo-type diet and lifestyle. Person C has no conventional risk factors for heart disease. Person D has no conventional risk factors either, but does have an LDL-P of 2,000. Logic here would dictate that Person D is at higher risk than Person C, but again, we don’t have actual data to quantify the difference in risk.

Heart disease is a complex, multifactorial process. The likelihood that we’ll have a heart attack depends on numerous factors, including genetics, diet, lifestyle and living environment. The purpose of this article is not to suggest that LDL-P is the only risk factor that matters, or that other risk factors shouldn’t be taken into consideration. It is simply to point out that existing evidence suggests that LDL-P is a much better predictor of heart disease risk than LDL or total cholesterol, and that it appears to be one of the better markers available to us now.

I was going to follow this article with one on statin drugs. But I’m almost certain that all of you are going to ask what increases LDL particle levels after reading this, so I think I’ll cover that next and then move on to statins after that.

Note: if you’re interested in a much more thorough discussion of how to determine your risk of heart disease and how to use diet, supplements and lifestyle changes to protect yourself and those you love, check out the High Cholesterol Action Plan.

Tagged as: cardiovascular, cholesterol, Heart Disease, LDL-C, LDL-P, particle number, risk

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What Causes Elevated LDL Particle Number?

genetics To read more about heart disease and cholesterol, check out the special report page.

In the last article in this series, I explained that LDL particle number (LDL-P) is a much more accurate predictor of cardiovascular disease risk than either LDL or total cholesterol. In this article, I’m going to briefly outline the five primary causes of elevated LDL-P.

Conventional medicine is primarily focused on suppressing symptoms. If your blood pressure is high, you take a medication to lower it. If your blood sugar is high, you take a medication to lower it. If your cholesterol is high, you take a medication to lower it. In most cases there is rarely any investigation into why these markers are high in the first place, with the possible exception of some basic (but often incorrect) counseling on diet and exercise.

On the other hand, functional medicine—which is what I practice—focuses on treating the underlying cause of health problems instead of just suppressing symptoms. If your blood sugar, blood pressure or cholesterol are high, the first question a functional medicine practitioner will ask is “why?” If we can identify the root cause of the problem, and address it at that level, medication is often unnecessary.

To use a simple analogy, if you have weeds in your garden, what happens if you just cut the weeds from the top? They grow right back—and sometimes faster than before! If you really want to get rid of them once and for all, you have to pull them up by their roots.

With this in mind, let’s look at some of the potential causes of elevated LDL particle number. If your LDL-P is high, it makes sense to test for and treat any of the conditions below (with the exception of the last, which is genetic and thus can’t be treated) before—or at least along with—taking pharmaceutical drugs.

5 common causes of elevated LDL particle number that can increase your risk of heart disease.

LDL particles don’t just carry cholesterol; they also carry triglycerides, fat-soluble vitamins and antioxidants. You can think of LDL as a taxi service that delivers important nutrients to the cells and tissues of the body.

As you might expect, there’s a limit to how much “stuff” that each LDL particle can carry. Each LDL particle has a certain number of cholesterol molecules and a certain number of triglycerides. As the number of triglycerides increases, the amount of cholesterol it can carry decreases, and the liver will have to make more LDL particles to carry a given amount of cholesterol around the body. This person will end up with a higher number of LDL particles.

Consider two hypothetical people. Both have an LDL cholesterol level of 130 mg/dL, but one has high triglycerides and the other has low triglycerides. The one with the high triglyceride level will need more LDL particles to transport that same amount of cholesterol around the body than the one with a low triglyceride level.

Numerous studies have found an association between increased LDL particle number, and metabolic syndrome. One study measured ApoB, a marker for LDL particle number, in a group of 1,400 young Finns with no established disease. The participants with the highest LDL particle number were 2.8 times more likely to have metabolic syndrome than those with the lowest levels of LDL-P. (1) A much larger study of over 300,000 men also found a strong association between LDL-P and metabolic syndrome and its components (i.e. insulin resistance, abdominal obesity, high blood pressure, etc.). (2)

Poor thyroid function is another potential cause of elevated particle number. Thyroid hormone has multiple effects on the regulation of lipid production, absorption, and metabolism. It stimulates the expression of HMG-CoA reductase, which is an enzyme in the liver involved in the production of cholesterol. (As a side note, one way that statins work is by inhibiting the HMG-CoA reductase enzyme.) Thyroid hormone also increases the expression of LDL receptors on the surface of cells in the liver and in other tissues. In hypothyroidism, the number of receptors for LDL on cells will be decreased. This leads to reduced clearance of LDL from the blood and thus higher LDL levels. Hypothyroidism may also lead to higher cholesterol by acting on Niemann-Pick C1-like 1 protein, which plays a critical role in the intestinal absorption of cholesterol. (3, 4)

Studies show that LDL particle number is higher even in subclinical hypothyroidism (high TSH with normal T4 and T3), and that LDL particle number will decrease after treatment with thyroid hormone. (5)

Another cause of high cholesterol profile is infection. Multiple studies have shown associations between bacterial infections like Chlamydia pneumoniae and H. pylori, which is the bacterium causes duodenal ulcers, and viral infections like herpes and cytomegalovirus and elevated lipids. (6) For example, H. pylori leads to elevated levels of total cholesterol, LDL cholesterol, lipoprotein (a), ApoB or LDL particle number, and triglyceride concentrations as well as decreased levels of HDL. (7)

Several mechanisms have been proposed to explain the association between infections and elevated blood lipids. Some evidence suggests that viral and bacterial infections directly alter the lipid metabolism of infected cells, and other evidence suggests that lipids increase as a result of the body’s attempt to fight off infection. Other evidence suggests that LDL has antimicrobial properties and is directly involved in inactivating microbial pathogens. This has been confirmed by studies showing that mice with defective LDL receptors—and thus very high levels of LDL—are protected against infection by gram-negative bacteria like H. pylori. (8)

One of the primary functions of the intestinal barrier is to make sure that stuff that belongs in the gut stays in the gut. When this barrier fails, endotoxins such as lipopolysaccharide (LPS) produced by certain species of gut bacteria can enter the bloodstream and provoke an immune response. Part of that immune response involves LDL particles, which as I mentioned above, have an anti-microbial effect. A protein called LPS-binding protein, which circulates with LDL particles, has been shown to reduce the toxic properties of LPS by directly binding to it and removing it from the circulation. (9) Studies have also shown significant increases in LPS-binding protein (and thus LDL particles) in cases of endotoxemia—a condition caused by large amounts of circulating endotoxins. (10)

Though more research is needed in this area, the studies above suggest that a leaky gut could increase the level of LPS and other endotoxins in the blood, and thus increase LDL particle number as a result. I have seen this in my practice. I recently had a patient with high LDL-P and no other risk factors. I tested his gut and discovered H. pylori and small intestine bacterial overgrowth (SIBO). After treating his gut, his LDL-P came down to normal levels.

The final cause of elevated LDL-P is genetics. Familial hypercholesterolemia, or FH, involves a mutation of a gene that codes for the LDL receptor or the gene that codes for apolipoprotein B (ApoB). The LDL receptor sits on the outside of cells; the LDL particle has to attach to the LDL receptor in order to deliver the nutrients it’s carrying and be removed from the circulation. ApoB is the part of the LDL particle that binds to the receptor. If we use a door lock as an analogy, apolipoprotein B would be the key, and the LDL receptor is the lock. They both need to be working properly for LDL to deliver its cargo and to be removed from the bloodstream.

Homozygous carriers of FH have two copies of the mutated gene. This condition is very rare. It affects approximately 1 in a million people. And people that are homozygous for this mutation have extremely high total cholesterol levels, often as high as 1000 mg/dL. And unfortunately they usually die from severe atherosclerosis and heart disease before the age of 25.

Heterozygous carriers, however, only have a single copy of the mutated gene, and the other copy is functioning normally. This is much more common. The prevalence is between 1 in 300 to 1 in 500 people, depending on which study you look at. These heterozygous carriers of FH have total cholesterol levels that often range between 350 and 550 mg/dL, along with very high LDL particle number. They have about three times higher risk of death from heart disease than people without FH if it goes untreated.

It’s important to note that people with FH have primarily large, buoyant LDL particles, and yet are still at much higher risk for cardiovascular disease. While it’s true that small, dense, oxidized LDL particles are more likely to cause atherosclerosis, large, buoyant particles can also be harmful when their concentration is high enough. This is one reason why LDL particle number is a superior marker to LDL particle size.

In the next article in this series, I will debunk the myth that statins extend lifespan in healthy people with no pre-existing heart disease.

Tagged as: cholesterol, conditions, genetics, infection, insulin resistance, LDL-P, metabolic syndrome, thyroid