Dear Mark,
Could you write an article on blood “markers” (cholesterols, triglycerides, blood sugar and … C-reactive protein)??? What are they? How can they be monitored and managed? Thanks mucho! Can’t wait for your book.
Thanks to Rob for the question today. Blood markers are essentially detectable and measurable substances in the blood. Their interpretations are based on the levels found and their correlations with disease or other health concerns the medical/research community has assigned to these substances. A blood workup can vary and run into the hundreds of markers, but (for today at least) let me focus on the key categories Rob mentioned.
The logical first set of readings is, of course, the cholesterol set (total, HDL, LDL, triglycerides) – a.k.a. lipid profile. It’s the one everyone gets (and insurance pays for) because the medical establishment continues to put more emphasis on cholesterol over many other heart health factors. The “total cholesterol” is calculated as the full amount of cholesterol (represented as mg/dL) being carted around in the blood by the various lipoprotein particles. In and of itself, it offers little information about heart risk or desirable/undesirable lipid profile.
The HDL particles (high-density lipoproteins) transport cholesterol from the body’s tissues to the liver, where it gets excreted through bile. A higher HDL is seen as favorable, but a more specific measure most doctors look for now is the HDL/LDL ratio. On the other end of picture is LDL (low-density lipoproteins), which transfers “new” cholesterol from the liver to the body’s tissues where it can be used for all manner of vital cell building and functioning. While HDL is often called the “good” cholesterol and LDL the “bad” cholesterol, they’re both really just two ends of the body’s self-regulatory lipid processing system. Finally, triglycerides are another form that fat takes as it travels to the body’s tissues through the bloodstream.
Now let’s get the chart on the table and then dissect. The American Heart Association offers the following recommendations for lipid profile measures:
HDL: “normal” readings vary between 40-50 mg/dL for men and 50-60 mg/dL for women; above 60 mg/dL considered “protective”
LDL: less than 130 mg/dL considered good; less than 100 considered “optimal”
Triglycerides: less than 150 mg/dL considered “normal”
Total Cholesterol (add 1/5 triglyceride measure to LDL and HDL numbers): under 200 mg/dL considered “desirable”
As for the HDL/LDL ratio, between a .3 and .4 (or higher) is generally seen as desirable.
Scalpel, please? First off, most people get their cholesterol profiles done every five years (what most insurance pays for (especially for younger folks) unless they’re currently diagnosed with heart disease or labeled “at risk.” Your lipid profile is much more flexible than a five-year window suggests. Even a few weeks (or, in some cases, a few days) will alter numbers substantially. In other words, a single reading is a snapshot and that’s about it. Nonetheless, let’s see what we can salvage.
First let me take on triglycerides. I think this measure gets short shrift. While the other lipid measures, I’ve said before, can act as red herrings, this marker can be telling in and of itself and is very often linked to other “bad” lipoprotein readings – low HDL and high LDL, including high VLDL (very low density lipoproteins – bigger, more pillowy particles that are largely composed of triglycerides). High triglycerides are considered a “lifestyle” measure and strongly correspond with a high carb diet, smoking and low physical activity. They correlate with not only an increased risk of heart disease in general but inflammation and insulin resistance. Another reason lipid analysis cannot stand on its own….
Another point? LDL and HDL measures are only the tip of the iceberg. These lipoproteins, usually measured as single categories, actually contain particles of varying size and alleged corresponding detriment. Smaller particles, many experts suggest, are more risky or at least less desirable. In essence, smaller HDL particles are less protective, and smaller LDLs are believed to be bigger contributors to artery plaque. And guess what kind of diet fuels high numbers of smaller low density lipoproteins? Not saturated fat, but… (drum roll) All together now: a high carb diet! Surprise, surprise….
It’s important to mention that a relatively small but increasing number of medical specialists would say that the traditional lipoprotein blood tests may not be the best way to measure your lipid profile. Better testing, many believe, can be achieved with other lipoprotein analysis tests such as liquid chromatography, Gel Electropheresis (GGE), density gradient centrifugation or NMR (Nuclear Magnetic Resonance). These techniques provide more detailed analysis of actual lipoprotein subfractions and can offer a fuller picture of particle size breakdowns.
We could talk forever and a day about lipids, but there are so many other nifty blood markers to discuss. Onward, shall we? Now for a favorite category of blood markers: blood sugar. We’ll include glucose and A1C levels here. A simple blood glucose test is usually administered after an 8 hour fast. A blood sample is taken to measure fasting glucose levels, or sometimes a fasting reading is followed by an oral glucose tolerance test (OGTT), in which the person drinks a glucose solution and has his/her glucose levels subsequently tested at given time intervals to see how well the body “processes” the sugar. The American Diabetes Association offers the following guidelines for glucose testing levels:
Fasting Glucose
70-99 mg/dL (3.9-5.5 mmol/L) considered “normal”
100-125 mg/dL (5.6-6.9 mmol/L) considered “impaired”
126+ mg/dL(7.0 mmol/L) suggests diabetes if measured on more than one occasion
OGTT (values not valid during pregnancy)
(As measured 2 hours following intake of 75 gram glucose solution)
<140 mg/dL (7.8 mmol/L) considered “normal”
140-200 mg/dL (7.8 to 11.1 mmol/L) considered “impaired”
200+ mg/dL (11.1+ mmol/L) suggests diabetes if measured on more than one occasion
Beyond standard glucose readings, A1C measures represent “longer term” glucose levels. Last year we reported on a New Zealand study involving 47,000 people (without diabetes) that correlated higher blood sugar levels (as measured by A1C levels) with greater mortality risk in the 4-year study window. (Causes of death: “endocrine, nutritional, metabolic, and immunity disorders” as well as “diseases of the circulatory system.”) The correlation of higher A1C levels with higher mortality risk was observed in A1C values that many hospitals consider the “normal” range. The initial “reference category” for the study was between 4.0 and 5.0%, and the highest category was 7.0% and higher, (7.0% marking a threshold defined by several health organizations including the American Diabetes Association). “Healthy” A1C readings are commonly interpreted between 4-6%, but the lower end of that range is preferable.
Finally, tests for inflammation markers like C-reactive protein are becoming more common. (I’d suggest including it in a blood workup for heart health or asking your doctor about it if you’re concerned about systemic inflammation or the possibility of an autoimmune disorder.) CRP, as it’s known, is produced by the liver and is generally only seen in trace amounts with blood tests. Its presence in the blood can be associated with infection or with systemic inflammation caused by various medical conditions, pregnancy or certain medications.
To help assess heart disease risk, the hs-CRP (highly sensitive test) is by far the better test. Though there’s some disagreement on a professional level and inconsistency in labs regarding “normal” levels, the American Heart Association offers the following guidelines for hs-CRP interpretation.
There are, indeed, other more newly recognized blood markers for inflammation out there (such as resistin, a strong biomarker for heart failure), but an hs-CRP is likely the one your doctor is most familiar with and your insurance most likely to pay for if you’re just looking for a general health overview and don’t show specific risk factors. If test results show reason for concern, your doctor can always order more specialized tests.
As mentioned, the list of blood marker tests is a mile long, and these few options are simply among the most common you’ll see. This overview is just the tip of the iceberg, I know, and I might come back to the subject in future posts if folks are interested. For now, let me say this about blood workups in general. Though the numbers might seem telling, they usually mean little in and of themselves or may indicate something seemingly unrelated (i.e. not what they talk about on the Pharma commercials). Cholesterol levels, for example, are influenced by everything from hypothyroidism to birth control pill use. Medications like anti-depressants and some blood pressure prescriptions can elevate glucose levels. An hs-CRP test can be influenced by something as mundane as a recent hard workout. And even among the most common tests, there’s sometimes an appreciable difference between one lab’s results and another’s testing the same sample (look for an upcoming post on that soon).
A blood workup can give you some hard evidence to work with in assessing your health, but you’ll need a good discussion with a doctor you trust who knows your background (with perhaps some second opinions/perspectives from other practitioners and sometimes even a bit of your own digging) to connect the dots and make sense of where your numbers come from. Whether you’re investigating the possibility of a particular condition or sketching an overview of your general health, by far the longer but more important stage of the game will be piecing it all together. There might be a number of paths suggested by the tests, or they may suggest nothing when you know in your gut that something is awry. Blood markers are tools, to be sure, but the full story behind them is seldom as black and white as the numbers on the page.
Have your thoughts to add? Thanks as always for your questions and comments. Keep ‘em coming!
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