Thursday, June 23, 2011

How to interpret your cholesterol test: The Basics

Despite the fact that nearly every adult American has these tests done at some point, it never ceases to surprise me when I’m asked what the tests mean. I order this test fairly regularly, but additionally, I have patients ask me to explain what the tests mean when their MD has ordered them. It’s an unfortunate fact that doctors often don’t fully explain the tests they are ordering, what the results mean, and what to do about it. I’m going to avoid speaking to the question of what to do about it, except in general terms, in order to provide a brief explanation of what’s being tested and what it means.

Total Cholesterol
Cholesterol is a small molecule found almost everywhere in the body, and which serves a wide variety number of functions, most of them beneficial. However, the reason doctors test for it is because excessively high levels of cholesterol in the blood have been linked to increased risk for heart disease. The basic mechanism is this – overly high levels of cholesterol in the blood mean increased amounts of cholesterol being deposited in artery walls, causing the walls to become stiff and inflexible. This damage leads to other disease further on down the road.

As medicine has learned more, cholesterol isn’t tested alone, but is parsed out into HDL and LDL. One important thing to understand is that cholesterol includes molecules aside from HDL and LDL (such as IDL and VLDL), so when you add your HDL and LDL counts together, it may not add up to your total cholesterol. While an ideal cholesterol count is below 200 mg/dL, patients with counts between 200 and 230 don’t necessarily need medication, especially if modifiable factors are identified that could be contributing to high cholesterol – these include lack of exercise and poor diet.

First, ‘good cholesterol’. The reason HDL is referred to as ‘good cholesterol’ is because higher counts of HDL are actually protective against heart disease. HDL is a molecule that travels throughout the bloodstream taking cholesterol out of blood vessel walls, thus reducing damage. Ideal HDL counts are between 45 and 60 mg/dL, though higher levels (above 60) may confer additional protection. Among the things found to increase HDL in the blood are exercise and fish oil.

LDL has earned the term ‘bad cholesterol’, because LDL travels the blood depositing cholesterol into blood vessel walls, opposite to HDL. Ideal numbers most people are 100 to 129 mg/dL, though many people, especially those with a family history of heart disease, will need to aim for levels lower than 100. When a high LDL is seen in conjunction with a low HDL, this is often an indication that dietary and lifestyle factors are at fault. LDL can be lowered by exercise and dietary fiber.

Triglycerides (TAGs) are more complicated than simple cholesterol, but provide a great piece of information. Though TAGs are tested along with fat molecules, they are actually made from sugars, and thus reflect dietary intake of carbohydrates, especially simple carbohydrates and sugar. While elevations in triglycerides don’t indicate diabetes, people with type II diabetes (adult onset diabetes) often have elevated triglycerides. Ideal levels of TAGs are below 150 mg/dL, and these tend to decrease fairly quickly in response to dietary changes.

While not specifically part of cholesterol testing, these are often ordered at the same time, because diabetes is a major contributor to cardiovascular disease. Type II diabetes is very controllable with diet and lifestyle changes, and can actually be reversed in some cases. Ideal levels are below 100 mg/dL after an overnight fast. Many doctors are now also testing hemoglobin A1c (HbA1c) to assess for long-term exposure to high blood sugar levels, so you may start seeing that appearing on your lab tests in the future, if you haven’t already.

CRP or hsCRP
Many of you will have seen this on lab tests as well. These molecules are generally interpreted as indicators of inflammation in the body. There have been efforts to link them to heart disease, because they are elevated as a result of artery wall damage, but unfortunately they are not very specific, as they can become elevated due to a variety of factors including acute illnesses. While the search for a reliable marker for vessel wall damage is important, and it’s laudable that people are looking, this test isn’t as reliable as we’d like it to be.

Conclusion: Metabolic Syndrome
This disease has gone through a number of names, including Syndrome X and Metabolic Syndrome X. It’s important to be aware of Metabolic Syndrome because it’s a major health problem in the US, especially among men, and it’s largely a result of diet and lifestyle. While the tests discussed can be affected by a variety of diseases, when they add up to Metabolic Syndrome, diet and lifestyle changes can have a major impact. Metabolic Syndrome is defined as the presence of three of the following five criteria: abdominal obesity, high triglycerides, low HDL, high blood pressure, and high fasting blood glucose. The guideline numbers can be found here.

A basic prescription for Metabolic Syndrome is this: moderate fat consumption (with a focus on healthy fats), low sugar consumption, and an exercise regimen.  Because Metabolic Syndrome is induced by lifestyle, lifestyle is the way out, and it requires work – my advice is to find a qualified naturopathic doctor or primary care medical doctor to work with you on this, to help you set and reach goals. In the age of the internet, it’s increasingly possible for consumers to become educated about their healthcare, and I encourage you to do so. While it’s important to be knowledgeable about health, don’t forget that being healthy is hard work, and you’ll need help along the way – find a good doctor who you work well with. Form a therapeutic alliance and use that person as a trusted advisor. Not every disease is caused by diet or lifestyle, but many are, and it’s important to have someone in your corner working for you.