Low-carb Lab Testing — Part 8: The CAC Test – A Better Way to Evaluate Cardiovascular Health

Low-carb Lab Testing — Part 8: The CAC Test – A Better Way to Evaluate Cardiovascular Health

What is the CAC test and why should you care?

If you’ve been following a low-carb or ketogenic diet for a while, there’s a chance your cholesterol has gone up.  And not just your HDL, but also your LDL—the so-called “bad cholesterol” (even though that’s a total misnomer).  Maybe your cholesterol has actually gone sky-high, and your doctor not only wants you to start taking medication immediately, but she’s also ordered you to quit your “crazy” high fat diet.  Even if you follow some other kind of diet—Paleo, vegetarian, low fat, or no special plan at all—maybe your cholesterol is high, and you’ve been told you need medication, or that you should exercise more.

Your doctor is only looking out for your best interest, but if they’re not up on the latest research, they might not know that your cholesterol level tells you very little about your risk for cardiovascular disease or a heart attack:

There’s “a growing volume of knowledge that challenges the validity of the cholesterol hypothesis and the utility of cholesterol as a surrogate end point.” (DuBroff, 2017)

It’s possible to have low cholesterol but massive heart disease, or to have very high cholesterol but be in great cardiovascular shape.

If you don’t want to start a war with your doctor, but you also don’t want to abandon a way of eating that’s helped you lose weight, have more energy, and maybe even reduce or eliminate diabetes medications, you can experiment with lowering your cholesterol by using the Feldman Protocol, which we featured here at Heads Up Health.  But there’s a much better way to evaluate your cardiovascular health than just looking at cholesterol.  It’s called the coronary artery calcium test (CAC).  We’ll explore it in detail in a bit.  First, let’s look a little closer at the problems with using cholesterol as an indicator of heart health.

Cholesterol is Protective

Evidence continues to build that cholesterol levels—including LDL—are not accurate indicators of cardiovascular disease risk, and that the medical community as a whole may have gotten “the cholesterol story” very wrong.  For starters, there’s the inconvenient truth that many people who have heart disease or experience a heart attack have “normal” or even low cholesterol.  Low cholesterol is no guarantee against a heart attack, nor is high cholesterol a one-way ticket to heart disease and sudden death.

In fact, evidence suggests that higher cholesterol—again, including LDL—may actually be beneficial, especially in your golden years.  A growing body of research indicates that high LDL cholesterol (LDL-C) is inversely associated with mortality in most people over sixty years of age.  Inversely associated means, the higher the LDL, the lower the risk for mortality.  To be fair, everyone’s risk for mortality is 100%, at least so far as we know.  So when we say there’s a lower risk for mortality, it means that someone has a smaller chance of dying from anything other than a nice old age.  This finding—that high LDL seems protective in some ways—has given researchers “reason to question the validity of the cholesterol hypothesis.”

This is especially true for older people.  Epidemiological and observational studies show that, for most people over 60 years of age, high LDL-C is inversely associated with mortality.  Researchers have also noted a “reverse epidemiology” among the elderly wherein slightly higher blood pressure, BMI, and cholesterol seem to be protective for health.

 

High Cholesterol Is Not a Disease

Cholesterol is a surrogate indicator.  It’s a measurement, not an illness.  Neither high total cholesterol nor high LDL-C, in particular, is a disease, in and of itself.  They have long been considered markers for cardiovascular disease or risk of heart attack, but this ignores the crucial fact that neither the number of LDL particles in your blood nor the amount of cholesterol carried in them indicates anything about the degree of atherosclerotic plaque built up in your major arteries.

Measuring the amount of cholesterol in your blood provides no information whatsoever about the accumulation of calcified plaques in coronary arteries—that is, how “clogged” your arteries are—or are not.  With this in mind, the obsessive focus on lowering cholesterol by any means necessary may have actually worsenedthe very epidemic of heart disease these treatments were intended to stop.  The authors of one paper made a powerful case that “the epidemic of heart failure and atherosclerosis that plagues the modern world may paradoxically be aggravated by the pervasive use of statin drugs,” and proposed “that current statin treatment guidelines be critically reevaluated.”

Bottom line: statin drugs do lower cholesterol, but having lower cholesterol doesn’t guarantee protection against heart attack or heart disease.  Plus, statins don’t just lower cholesterol.  The biochemical mechanism by which they do so comes along with a host of other effects, some of which have drastic implications for cardiovascular health.  To name just two, statins interfere with healthy mitochondrial function and also impair the synthesis of crucial vitamin K2.  Vitamin K2 is a “traffic cop” for calcium: it helps deposit it where it belongs, like in your bones and teeth, and helps steer it away from places you don’t want it, like your artery walls, your joints, and your kidneys.  So you can see how a deficiency in this critical vitamin could lead to arterial calcification, and it has nothing to do with the amount of cholesterol in your blood.  (You can learn more about this fascinating but underappreciated vitamin in the book, Vitamin K2 and the Calcium Paradox.)

 

Enter the CAC Test

Since people who have heart disease or suffer heart attacks run the gamut from low cholesterol to high cholesterol and everything in between, using total cholesterol or even LDL as the determinant of whether someone’s at risk for a cardiovascular event is as misguided as gauging metabolic health and carbohydrate tolerance solely through measurements of blood glucose, while ignoring the crucial role of insulin.

With all this in mind, more physicians are taking advantage of the coronary artery calcium scan.  Unlike serum cholesterol measurements, which, again, are only surrogates, the CAC provides direct observation of arterial calcification that has already occurred.  Not atherosclerosis an individual might or might not be at risk for based on their cholesterol, but the actual disease in progress.  Why rely solely on surrogates when you can have a picture of the actual state of your arteries?

Data is accumulating that confirms what many doctors already know, even if they’re hesitant to admit it: cholesterol levels often don’t correlate with atherosclerosis.  Data show that “significant ASCVD [atherosclerotic cardiovascular disease] risk heterogeneity exists among those eligible for statins according to the new guidelines. The absence of CAC reclassifies approximately one-half of candidates as not eligible for statin therapy.”  In plain English: half the people who would be put on statins based on cholesterol measurements were not candidates for these potentially dangerous drugs when their actual coronary artery calcification was measured.

Other studies bear similar findings.  According to a study in Korean adults, over 50% of individuals for whom statin therapy was recommended had a CAC score of zero – no calcification.  Based on actual arterial calcification—or, rather, the lack thereof—these individuals were at low risk for cardiovascular events, but without having gotten the CAC test, they might have been treated with statins based solely on the surrogate measurement of LDL.

What about the other side of this?  What about people with normal or even “low” cholesterol?  Does that go hand-in-hand with low risk for a cardiovascular event?

Not quite.  Just as people with high cholesterol might have little to no arterial calcification, people with normal or low cholesterol could have high CAC scores and be at greater risk for heart disease, heart attack, or sudden death.  This exact scenario played out in a study of CAC in low-risk women—low-risk, meaning they had cholesterol in the conventionally “normal” range: “Among women at low ASCVD risk, CAC was present in approximately one-third and was associated with an increased risk of ASCVD and modest improvement in prognostic accuracy compared with traditional risk factors.”  Plain English translation again: one third of women assessed to be at low risk for atherosclerosis already had measurable arterial calcification.  Say it with me for emphasis, folks: the amount of cholesterol in your bloodstream tells you nothing about the amount of atherosclerotic plaque in your arteries.

 

What is Coronary Artery Calcium and Why Test It?

Unlike your cholesterol, your CAC score gives you visual proof of arterial plaque.  The reason to measure calcium, specifically, is, “Coronary artery calcification is part of the development of atherosclerosis; it occurs exclusively in atherosclerotic arteries and is absent in the normal vessel wall.”  In other words, whether your cholesterol is low, high, or somewhere in the middle, if you have detectable coronary artery calcium, you have atherosclerosis.

And the reason to measure the extent of calcified plaque is that these plaques can rupture, break away from the artery wall, and block the artery, cutting off blood flow to the heart—which is one way heart attacks happen.

If you’re wondering why calcium might end up in your arteries, the main reason is that it’s one of the ways your body repairs damaged blood vessels.  According to Ivor Cummins and Jeffry Gerber, MD, in their book, Eat Rich, Live Long:

“The body’s response to damaged coronary arteries is always the same, and that response is what the CAC scan directly observes and quantifies.  Your body tries to repair itself by depositing calcium in the damaged areas of the arterial wall.  As the damage continues, these repair processes quicken.  They desperately attempt to shore up the arterial walls before a rupture occurs.  This growing calcium becomes the telltale sign of imminent danger—the ultimate canary in the coal mine.”

 

What is the CAC Test?

The CAC test, also called a “heart scan,” is a non-invasive, special x-ray of the heart and coronary arteries, performed via CT scan (computerized tomography).  The scan itself takes only 20-30 seconds, but the whole procedure, from start to finish, takes about 10-15 minutes.  Fasting is not required, but you may be asked to refrain from smoking or consuming caffeine for four hours before the scan, since an elevated heart rate can reduce the image quality.  Many insurance companies cover this test, but if yours doesn’t, or your doctor won’t order one for you, you can pay for it out of pocket, for about $150 in the U.S.

Test results are usually given as a number called an Agatston score.  This number reflects a composite measurement of the total area of calcium deposits, and the density of the calcium.  According to the Mayo Clinic, a score of zero means no calcium is present, and risk of heart attack is low.  When calcium is present, the higher the score, the higher the risk for heart attack in the long term.  A score of 100 to 300, considered “moderate plaque deposition,” is associated with a high risk of heart disease or heart attack over the next three to five years, and a score over 300 indicates very high to severe risk.

The key thing to know here is, many people (especially low-carbers) have very high cholesterol, but CAC scores of zero.  Even if your score isn’t zero, if it’s very low, that might put your doctor’s fears to rest even if you have high cholesterol.  Keeping the peace with your doctor isn’t a bad reason to have a CAC test, but an even better one is to put your own mind at ease.  

The exact meaning of different coronary calcium scores differ depending on the source cited, but here’s a general guide, according to Axel Sigurdsson, MD:

Coronary calcium score 0: No identifiable plaque. Risk of coronary artery disease very low (<5%)

Coronary calcium score 1-10: Mild identifiable plaque. Risk of coronary artery disease low (<10%)

Coronary calcium score 11-100: Definite, at least mild atherosclerotic plaque. Mild or minimal coronary narrowings likely.

Coronary calcium score 101-400: Definite, at least moderate atherosclerotic plaque. Mild coronary artery disease highly likely. Significant narrowings possible

Coronary calcium score > 400: Extensive atherosclerotic plaque. High likelihood of at least one significant coronary narrowing.

Here’s another look at CAC scores, from Eat Rich, Live Long:

Data adapted from Cardiac CT Imaging: Diagnosis of Cardiovascular Disease

 

However, a high CAC score doesn’t mean you’re automatically in imminent danger.  If your plaques are stable—that is, they don’t keep increasing over time—your risk for a cardiovascular event remains pretty low.  On the other hand, even if you start out with a relatively low score, if that score increases substantially over time, your risk is much higher.  Remember, as arterial damage worsens, calcium deposition increases, so if your CAC score is going up, your arteries are in worse shape.

From Eat Rich, Live Long:

 

Not a Perfect Test

Although a low CAC score generally indicates low risk for cardiovascular events or disease, it’s not a full guarantee.  Unstable coronary plaques vulnerable to rupture may be present in the absence of calcium deposition.  And a high CAC score increases the chances that you have vulnerable plaques, but it doesn’t identify specific places where a rupture or blockage might occur.  Dr. Sigurdsson wrote:

“The presence and extent of coronary calcium are first and foremost markers of the extent of atherosclerosis within the coronary arteries. Nonetheless, it is important to understand that the coronary calcium score does not necessarily reflect the severity of narrowing (the degree of stenosis). Still, a patient with a high calcium score is more likely to have a significant narrowing of a coronary artery than a patient with a low calcium score.  An individual without coronary artery calcification is very unlikely to have a severe narrowing of a coronary artery.  Although cardiovascular events can occur in patients with very low calcium scores, the incidence is very low.”

 

Take Action

If your CAC score is zero or very low, keep doing what you’re doing!  But if you have a high score, don’t let fear overtake you.  Instead, use that knowledge to spur you to action.  Specifically, consider adopting a

low-carb, higher-fat diet.  Nothing’s more damaging to your blood vessels than chronically high blood sugar or insulin.  Low carb and ketogenic diets have been shown time and again to reduce inflammation, reverse metabolic syndrome, and be beneficial for cardiovascular health.

Not only can you slow the progression of arterial calcification, but you can actually reverse it.  This was virtually unheard of in the past, but that’s because the only things recommended to people with high CAC scores was a low-fat diet and cholesterol-lowering medications.  Since coronary artery calcium has virtually nothing to do with your cholesterol and a lot more to do with repairing damage to blood vessels injured by chronically high glucose and insulin, it’s no wonder a high-carb diet and cholesterol medications made no impact.

On the other hand, a ketogenic or low-carb, high-fat diet might be just the thing to help those blood vessels heal and restore your cardiovascular system to its best functioning.  Use the tracking system here at Heads Up Health to record your CAC score and keep track of all your other health data in one convenient place.

Low-carb Lab Testing — Part 8: The CAC Test – A Better Way to Evaluate Cardiovascular Health

Low-carb Lab Testing — Part 8: The CAC Test – A Better Way to Evaluate Cardiovascular Health

What is the CAC test and why should you care?

If you’ve been following a low-carb or ketogenic diet for a while, there’s a chance your cholesterol has gone up.  And not just your HDL, but also your LDL—the so-called “bad cholesterol” (even though that’s a total misnomer).  Maybe your cholesterol has actually gone sky-high, and your doctor not only wants you to start taking medication immediately, but she’s also ordered you to quit your “crazy” high fat diet.  Even if you follow some other kind of diet—Paleo, vegetarian, low fat, or no special plan at all—maybe your cholesterol is high, and you’ve been told you need medication, or that you should exercise more.

Your doctor is only looking out for your best interest, but if they’re not up on the latest research, they might not know that your cholesterol level tells you very little about your risk for cardiovascular disease or a heart attack:

There’s “a growing volume of knowledge that challenges the validity of the cholesterol hypothesis and the utility of cholesterol as a surrogate end point.” (DuBroff, 2017)

It’s possible to have low cholesterol but massive heart disease, or to have very high cholesterol but be in great cardiovascular shape.

If you don’t want to start a war with your doctor, but you also don’t want to abandon a way of eating that’s helped you lose weight, have more energy, and maybe even reduce or eliminate diabetes medications, you can experiment with lowering your cholesterol by using the Feldman Protocol, which we featured here at Heads Up Health.  But there’s a much better way to evaluate your cardiovascular health than just looking at cholesterol.  It’s called the coronary artery calcium test (CAC).  We’ll explore it in detail in a bit.  First, let’s look a little closer at the problems with using cholesterol as an indicator of heart health.

(more…)

Low-carb Lab Testing — Part 7 — The Kraft Test (Hyperinsulinemia)

Low-carb Lab Testing — Part 7 — The Kraft Test (Hyperinsulinemia)

In many people, high insulin (hyperinsulinemia) is the primary driver of chronic metabolic illness, even when blood glucose is normal. For people concerned with achieving and maintaining optimal health, few things are more important than healthy gluco-regulation—that is, your body’s blood glucose and insulin levels, and how they respond to the foods you eat. Here at Heads Up Health, we’re committed to helping you realize your health goals. Past posts on our blog have explained how to interpret various lab tests for people on low carb diets, such as fasting glucose and hemoglobin A1c. We emphasized that besides just measuring your glucose, it’s imperative to keep track of your insulin levels. Fasting insulin is the most important test most doctors don’t even order.

Another measurement, called HOMA-IR, is the relationship between your fasting glucose and insulin—it tells you how much insulin your body needs in order to keep your blood glucose at a certain level. Because it factors in insulin and not just glucose, HOMA-IR is often a better indicator of metabolic status than glucose alone. But what should you do if your fasting insulin level is normal, but you think you have signs and symptoms of chronic hyperinsulinemia? Is this even possible? Can you have a normal fasting insulin level but have high insulin at other times? Yes! Enter the Kraft test.   

What’s the Kraft Test?

If you’ve never heard of the Kraft test, don’t worry; you’re not alone. It’s not a well-known test in conventional medicine, but it’s gaining popularity among doctors who use low carb and ketogenic diets with their patients. If you’re familiar with the oral glucose tolerance test (OGTT), the Kraft test is a variation on it. In case you don’t know what the OGTT is, let’s start there.

The OGTT is typically used to diagnose type 2 diabetes or gestational diabetes (diabetes during pregnancy). It measures your body’s glucose levels in response to 75 grams of liquid glucose. It’s performed in a lab or a doctor’s office, and it starts off with a baseline or fasting glucose measurement. After that sample is taken, you drink the glucose solution, and then your blood glucose is measured one and two hours later. (Occasionally some labs will include tests at the 30 and 90-minute marks as well.)

Here’s what the American Diabetes Association says about the results.

At the two-hour mark, if your blood glucose is:

  • <140 mg/dL – you are not diabetic
  • 140 – 199mg/dL – you have pre-diabetes
  • ≥200 mg/dL – you have type 2 diabetes

The Kraft test goes beyond the standard OGTT in two ways: 

  1. It measures insulin along with glucose
  2. Instead of only two hours, the test is extended to five hours

With these two small changes, the Kraft test gives you a staggering amount of information you won’t get from the standard OGTT.

Why’s it called the Kraft test? Well, the man who created it was Joseph Kraft, MD. It can also be called an “oral glucose tolerance test with insulin assay,” but in the low carb community, it’s usually referred to as the Kraft test, to honor the man whose work was some of the earliest in uncovering the detrimental effects of chronically high insulin.

By including insulin measurements and extending the test to five hours, what Kraft discovered was nothing short of mind-blowing. As he wrote in his book, Diabetes Epidemic & You, “There are far too many who are told, ‘Don’t worry, your fasting blood sugars are normal.’” And indeed, many people do have normal fasting blood sugar, but that’s only thanks to sky-high insulin. (HOMA-IR can help identify this situation.) And what if your fasting sugar and fasting insulin are both normal, but you suspect your unresolved health issues could be due to high insulin at other times of the day? This is where the Kraft test shines.

To describe the situation of normal glucose with high insulin, Dr. Kraft coined the phrases diabetes in-situ, and occult diabetes—occult meaning “hidden”—the diabetes (that is, the high glucose), is hidden, or masked, by the high insulin. And as we explained in the Heads Up Health post on fasting insulin, even when glucose is normal, chronically high insulin is a major contributor to abdominal obesity, gout, hypertension, PCOS, skin tags, and more. And remember—the official diagnostic criteria for type 2 diabetes are based on glucose measurements alone, not insulin! This is why quite literally millions of people with diabetes in-situ remain undiagnosed, and their medical care team fails to connect hyperinsulinemia to the issues they’re dealing with–because they’re not testing insulin.

The Kraft test shows you your glucose and insulin responses to an oral glucose load. Here’s how it works:

Kraft’s original tests called for 100 grams of glucose solution, but some doctors may use 75 grams. Just as with the standard OGTT, your baseline glucose and insulin levels are recorded via fasting levels. You consume the liquid glucose, and then your glucose and insulin are both measured at the 30-minute mark, and then again at one hour, two, three, four, and five hours.

Kraft identified five distinct patterns of elevated insulin:

Hyperinsulinemia - Kraft Test

Image courtesy of Theodore Naiman, MD

 

Pattern 1 – Metabolically healthy: In response to a glucose load, the insulin level rises quickly, but moderately, and it comes back down relatively quickly. Fasting insulin and glucose levels are normal, and the peak insulin level is reached at about 30 minutes. By about 3 hours later, it’s back to baseline. Glucose and insulin responses are both normal.

Pattern 2 – Delayed insulin peak: In response to a glucose load, the insulin level rises quickly, but it rises higher than that for the healthy person in pattern 1. Fasting insulin level is normal, and the peak level is reached at 30-60 minutes. In addition to rising higher, insulin takes longer to come back down, not returning to baseline until about 4-5 hours after. Glucose response is normal, but insulin is elevated higher than normal, and it remains elevated for a prolonged amount of time. This pattern indicates hyperinsulinemia.

Pattern 3 – Delayed insulin peak: In response to a glucose load, insulin rises even higher than the already hyperinsulinemic example in pattern 2, but it doesn’t reach its peak until even later. Fasting insulin is normal, but the peak level isn’t reached until the 2 or 3-hour mark. This is a delayed peak, and it takes even longer to come back to baseline. Glucose response may be normal or at diabetic levels; insulin is elevated higher than normal, and it remains elevated for a prolonged amount of time. This pattern indicates hyperinsulinemia.

Pattern 4 – Insulin Resistance: Fasting insulin level is elevated (>10 μU/mL). In response to a glucose load, the already elevated baseline insulin level skyrockets, takes a very long time to come back down, and when it does eventually come down, it comes down only to the baseline, which was already abnormally high. Glucose response is usually at diabetic levels. This pattern is diagnostic for insulin resistance.

Pattern 5 – Insulinopenic (low insulin): Fasting insulin is very low. In response to a glucose load, insulin barely budges, but glucose reaches diabetic levels (possibly as high as ≥300mg/dL). All tested values for insulin over the five hours are <30 μU/mL. When all insulin measurements are low and glucose is elevated, this pattern is suggestive of type 1 diabetes.

To see a more detailed breakdown of the different patterns with both insulin and glucose, check out the guide from Meridian Valley Lab.

A Word of Caution for Low Carbers

Some people who’ve been following a long-term low carb or ketogenic diet will show pattern 5, low insulin. When insulin measurements are low and glucose is also low, this is not considered pathological. (It’s only a problem when glucose is high.) This is known to occur in some long-time low carbers.

BUT: it’s been suggested that people who’ve been following a low carb or ketogenic diet for a while should “carb up” for a week or so to prepare for an OGTT or Kraft test. They should consume about 100-150 grams of carbohydrate for several days in order to get their body re-acclimated to metabolizing a significant amount of carbohydrate. Without this readjustment period, there’s a risk of getting a false result—of appearing to have extremely elevated insulin and/or glucose, when it’s really just that the body isn’t accustomed to dealing with a big wallop of glucose all at once.

Should You Do a Kraft Test?

If you’re satisfied with the results you’re getting from your diet and lifestyle, there isn’t much of a pressing reason to do the Kraft test. (After all, why would you want to drink 75+ grams of liquid glucose, even if you’re not on a low carb diet?) Also, there are other indicators that, taken together, can tip you off as to whether your insulin levels are chronically elevated (such as high triglycerides, low HDL, and a high waist-to-height ratio).

But if you feel like you’ve been doing everything right, yet you’re still dealing with signs & symptoms of a condition that’s known to be driven primarily by high insulin, it might be worth it to see your glucose and insulin in action—especially if your fasting levels for both are normal.

Once you know for sure how your body responds, you can put that data to work for you and let it guide you onto a path to better health. Use the tracking software here at Heads Up Health to do just that. We make it easy to monitor trends in your glucose, ketones, insulin, body measurements, temperature (good for thyroid function), and more, plus you can even track your fasts. Even your Bristol stool score!

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Tracking the Feldman Protocol with Heads Up

Tracking the Feldman Protocol with Heads Up

The Feldman protocol…picture this scenario….

You’ve been following a low carb or ketogenic diet. You’ve lost weight, your acid reflux is gone, your blood pressure’s normal for the first time in years, your blood sugar’s better, you’ve been able to ditch some of your type 2 diabetes meds, you have more energy, and your joints no longer feel like you need to spray them with WD-40. You feel like a new person! Your doctor is thrilled with all this … until your cholesterol results come back. (more…)

Low-carb Lab Testing — Part 6 — Thyroid Panel

Low-carb Lab Testing — Part 6 — Thyroid Panel

Thyroid function is a hotly debated topic in the low-carb world. While most people typically experience fat loss, better energy levels, and improved overall vitality on a low-carb diet, in some individuals, measurements of thyroid-related hormones suggest that a low carbohydrate intake might be having adverse effects on the thyroid gland. Is it possible that a way of eating that has such wonderful benefits for so much of the body could be harmful for the thyroid?

This is the fifth installment of a series exploring lab tests for people following low-carb diets. Due to the effects of the low-carb or ketogenic ways of eating on overall metabolism, interpreting certain lab tests requires a slightly different perspective compared to results from people following high-carb diets.

Previous posts have explored blood glucose testing, fasting insulin, and HOMA-IR (and remember: if you’d like to get some tests your doctor isn’t familiar with, or to test more frequently than your insurance will cover, this recent Heads Up Health post will show you how to order your own lab tests).

Keeping track of your numbers is an important step for anyone who wants to transform their health. Heads Up Health was created to empower you to manage all of your health data, including your lab test results, in one secure location. You can learn more on our homepage or by clicking below to create your account and start building your own centralized health portfolio.

START TRACKING!

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