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Why heart attack risk goes well beyond LDL-C

Heart Health Cholesterol Genetics

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If you’re like most people, you go to the doctor once or twice a year to get blood drawn. A few weeks later, you get a call to go over the numbers. If the numbers are good, you rest easy. If they’re bad, you explore your options which often include some form of prescription medication. Once the results are in, and the plan has been set, most of us get back to our everyday lives and forget about the medical stuff until the next checkup. We don’t think to ask for additional data, we assume we have all the data we need.

But do we?

What if I told you that most people receive only very basic blood tests that don’t give the full picture of their risk for a heart attack?

For example, most Americans don’t get tested for Lp(a), which is a genetic marker associated with a modest, but consistent, increase in risk of developing heart disease, especially when levels exceed 50 mg/dl (R). Celebrity trainer Bob Harper, of Biggest Loser fame, had high levels of Lp(a) when he suffered a heart attack a few years ago. Harper didn’t know he was at increased risk for heart disease until he had a heart attack. None of the doctors he had been seeing tested for Lp(a).

Celebrities like Bob Harper offer a cautionary tale, but our standard blood tests haven’t caught up. Basic lipid panels don’t just miss Lp(a), they also fail to include markers like APOB or LDL-P, which as we will learn in a moment, are the single most important metrics anyone interested in heart health can know. (R)

Instead, we get LDL-C, total cholesterol, Triglycerides, and HDL, which are all important, but don’t always give us an accurate assessment of where things stand with our heart health.

What has developed is a system where there are two classes of testing. Those that have the best doctors get their blood sent to labs like Boston Heart Diagnostics which use the latest technology to offer patients the full spectrum of biomarkers relevant to their health. The second group, like Bob Harper before his heart attack, remains in the dark.

What is the solution?

The best one is to find a doctor who uses Boston Heart, True Health Diagnostics, or another lab that offers a full breakdown of not only lipids, but other important markers like hsCRP and homocysteine.

If you don’t have access to one of these labs it is possible to use combinations of basic tests to roughly estimate your LDL-P number, but as we will see in a minute, it’s far from an exact science.

But before I get to that, first a rundown of why the famous LDL-C “bad cholesterol” isn’t an accurate stand alone indicator of risk for a heart attack.

Why testing LDL-C alone isn’t enough

Science Grade

LDL-C is known as the “bad cholesterol,” but it’s not really cholesterol at all. Instead, LDL-C represents the amount of cholesterol within low density lipoproteins, which are the “taxis” that move cholesterol around the body (R). LDL are thought to be bad because they can carry their cholesterol passengers into the wall of an artery and leave them there, which over time causes heart disease as these plaques accumulate. So, it’s the role of LDL in transporting cholesterol, not the cholesterol itself, that causes danger.

But here’s the thing: cholesterol isn’t the only passenger carried by LDL taxis.

LDL also carry triglycerides, a type of fat the body uses for energy. And this is why measuring LDL-C isn’t enough: focusing only on the cholesterol cargo doesn’t tell us the total number of taxis on the road.

Only testing for LDL-P, which measures the total number of LDL carrying both triglycerides and cholesterol, can do that. The problem is very few people know their LDL-P numbers. As we learned from the tragic death of the former host of Meet the Press, Tim Russert, LDL can do damage with triglycerides just as it can with cholesterol. Before his heart attack at age 58, Russert had low levels of LDL-C (less than 70 mg/dl), but high levels of triglycerides. The NY Times article detailing his battle with heart disease wonders out loud whether LDL-P / APOB would have been a better marker to gauge his risk of a heart attack than LDL-C.

What is APOB?

APOB, which stands for apolipoprotein B, is the protein that makes up each LDL particle. There is one APOB protein for every LDL particle which means you can gauge APOB from the LDL-P number and visa versa. LDL-P is of utmost importance because it represents the total number of chances that fat could be deposited into your arteries.

Lipid expert Peter Attia breaks it down this way:

If you want to stop atherosclerosis, you must lower the LDL particle number. Period

The tragedy of Tim Russert teaches us that high LDL-C is only a risk factor for heart disease when it matches with the LDL-P number.

As a practical matter, if you have low LDL-C and high LDL-P, it means that the LDL particles in your blood are rich in triglycerides, which is most often seen in people with very high blood sugar, sometimes called “insulin resistant” people. This means your blood sugar numbers could clue you in on the state of your LDL-P in the absence of more advanced testing.

My experience measuring LDL-C vs. LDL-P

In my case, I have consistently good HbA1C, fasting glucose and insulin numbers almost irrespective of what I eat, but my lipids and levels of plant sterols can go slightly out of range. As I have written about previously, I have elevated Lp(a) which to date has ranged from about 33mg/dl to 49 mg/dl.

Because I am not insulin resistant and have consistently low triglycerides (meaning there aren’t a ton of LDL particles carrying triglycerides in my blood), my LDL-C will usually track closely with my LDL-P (and numerous blood tests have confirmed this), so LDL-C is a more useful metric for me than some who have issues with high triglycerides.

When my LDL-C goes up, my LDL-P usually goes up. When my LDL-C goes down, my LDL-P usually goes down. In other words, my particle and LDL cholesterol numbers are very often concordant. However, it is worth noting that this is not always the case. After a recent 36 hour fast, I had an odd situation where my LDL-C and APOB (particle wasn’t measured at this draw) were discordant.

My LDL-C spiked to 119 mg/dl, but my APOB was in the green at 79 mg/dl. This small experiment demonstrates the importance of measuring LDL-P. While the LDL-C test is designed to get an idea of LDL-P, the two don’t always match. If a doctor had just looked at my LDL-C number without referencing my APOB of 79 mg/dl, she might have suggested a statin. The APOB result actually makes the LDL-C number look far less dangerous, even benign depending on who you ask. In fact, in the world of discordant LDL-P and LDL-C results, the lowest risk group is those who have elevated LDL-C and low LDL-P. (R) By contrast, the highest risk group is the Tim Russert group where LDL-C is low, but LDL-P is high.

For more on the possible variations between LDL-P and LDL-C, I recommend this excellent blog by Peter Attia. It’s a much deeper dive into the topics I am touching on here.

Using basic blood tests to estimate LDL-P

Let’s say all you have are basic blood tests and don’t have access to a lab like Boston Heart but want to get an idea of your LDL-P number.

What can you do?

Look at your last blood draw. If your doctor tested for HbA1c, which represents your average blood glucose over the last two months, you’re in luck. Because people with insulin resistance are often the ones with discordant LDL-C and LDL-P, you can guess that your LDL-C will be a good predictor of your LDL-P number if the HbA1c is low. The higher the HbA1c number goes, the better chance you will have discordance between your LDL-C and LDL-P.

If you don’t have ready access to these labs, you can do a “tandem” at home test with a company like Everlywell for a rough estimate of your LDL-P / APOB number. If you order a lipid panel and a blood sugar panel, the LDL-C will approximately reflect the state of your LDL-P if the blood sugar numbers are in the green.

If LDL-C is low and blood sugar is high, there is a higher likelihood that LDL-P is high and that the particles are triglyceride rich. This is the Tim Russert phenotype and represents one of the highest risk group for heart “events.” (R)

Although it’s not an exact science, and again, an APOB or LDL-P test is preferable, this is an easy way to start tracking your own data right away.

Not everyone has access to some of the more high flying blood tests, and it’s better to have some data than no data.

John O'Connor

John O'Connor is the founder of Gene Food, host of the Gene Food Podcast and a health coach trained at Duke's Integrative Medicine Program. Read his full bio here.

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