The Blood Triglyceride:HDL Ratio and LDL Particle Size: Critical Issues for Determining Risk of Coronary Heart Disease!

Just about anyone who is health-conscious knows that LDL-cholesterol is nicknamed ‘the bad cholesterol’. It has long been known that individuals with elevated levels of LDL face an increased risk of coronary heart disease (CHD), which can result in heart attack, coronary artery bypass surgery, or stent placement. With approximately 100 million Americans having abnormal blood cholesterol levels, it is no wonder that statin drugs are one of the most commonly prescribed medications in our society.

What you may not know about LDL-cholesterol is that not all LDLs are the same. While some LDLs in our blood are relatively small in size and rather dense (heavy), other LDLs are larger and less dense (fluffy). Doctors and other health professionals often refer to LDL particle size when discussing this issue. Over the past two decades, it has become apparent that LDL particle size plays a very important role in determining the risk of CHD.^1,2 As shown below in Figure 1, people with LDLs that are primarily small and dense face a much greater risk of CHD than people with LDLs that are larger and less dense. In other words, two people with the same elevated LDL value might actually be at very different levels of risk!

At this point, you may be thinking to yourself that your doctor has never mentioned your LDL particle size. Most labs at the present time simply report the overall LDL value instead of providing information about LDL particle size. Historically, this has been a cost issue more than anything else. However, scientists in the mid-1990s found that in most people, the ratio of blood triglyceride level to HDL-cholesterol level (known as the Trig:HDL ratio) provides an indirect but reasonably accurate estimate of LDL-cholesterol particle size. Here are two examples:

1) Steve has an LDL-cholesterol level of 160 mg/dL, blood triglyceride level of 100 mg/dL and an HDL-cholesterol level of 50 mg/dL. His Trig:HDL ratio is 100 / 50 = 2.0

2) Michelle also has an LDL-cholesterol level of 160 mg/dL, but has a blood triglyceride level of 280 mg/dL and an HDL-cholesterol level of 40 mg/dL. Her Trig:HDL ratio is 280/40 = 7.0

While there are no established standards for the Trig:HDL ratio, the higher the ratio, the more indicative that the individual has the more dangerous small/dense LDL particle size. So even though Steve and Michelle have the same LDL-cholesterol level of 160 mg/dL, Steve is much more likely to have the large and fluffy LDL particle size (lower risk), while Michelle is much more likely to have the small and dense LDL particle size (higher risk).

The Trig:HDL ratio provides additional valuable information regarding CHD risk in that it provides an indirect measure of insulin resistance. A brief review: insulin is a hormone produced by the beta cells of the pancreas. Its main role is to assist in the transport of glucose and amino acids from the blood into the cells. Insulin resistance is  a condition where a normal insulin production leads to a sub-normal uptake of blood glucose by the tissues. Therefore, people who are insulin resistant tend to have elevated blood glucose levels, and are much more likely to develop prediabetes and type 2 diabetes than people who are not insulin resistant. A high Trig:HDL ratio is usually a good indicator of the presence of insulin resistance. Using the examples above and with all other factors being equal, Steve would be much less likely to have insulin resistance than Michelle. Therefore, Steve would be at a lower risk of developing CHD than Michelle.

Do Exercise, Diet, and Weight Loss Affect all of This?

Yes, and that is a huge understatement!

• Exercise helps to increase HDL-cholesterol levels and decrease blood triglyceride levels. It also helps to convert the small and dense LDLs into the larger/fluffier LDLs, and makes insulin work better. So, with all other factors being equal regular exercisers tend to have lower Trig:HDL ratios, larger and fluffier LDLs, and are much less likely to develop insulin resistance and subsequent prediabetes and type 2 diabetes when compared with non-exercisers. This in turn leads to a lower risk of CHD.
• A decrease in saturated and trans fat, as well as a decrease in simple sugar intake is a good first step from a dietary perspective. This is especially true when accompanied by an increase in dietary monounsaturated and polyunsaturated fat intake (especially omega-3s found in fatty fish). Adding to this an increased intake of unrefined plant-based foods and reduced-fat dairy will often help to decrease elevated blood triglyceride levels, improve insulin function, and reduce resting blood pressure if it is elevated. All of these steps would then be associated with an improved Trig:HDL ratio, larger/more fluffy LDLs, decreased risk of prediabetes and type 2 diabetes, and ultimately a decreased risk of CHD.
• People who carry too much body fat in the abdominal region have what is known as upper body or visceral obesity. Loss of abdominal fat through a combination of regular exercise and dietary changes often leads to increased levels of HDL-cholesterol and decreased blood triglyceride levels, as well as improved insulin function and decreased resting blood pressure. The result is a lower Trig:HDL ratio, larger/more fluffy LDLs and a decreased risk of prediabetes, type 2 diabetes, and CHD.

So, the next time you have blood work done, calculate your Trig:HDL ratio if you do not see this value on your report. Remember that the higher the ratio, the higher the risk of developing CHD and high blood pressure. While there are medications that can help decrease insulin resistance, blood pressure, LDL-cholesterol, and blood triglyceride levels, lifestyle changes cost nothing and have no side effects!

References

1. Lamarche, B., Lemieux, I., Despres, J.P. (1999). The small dense phenotype and the risk of coronary heart disease: epidemiology, pathophysiology, and therapeutic aspects. Diabetes Metab. 25:199-211.

2. Laakso, M. et al. (1993). Lipids and lipoproteins predicting coronary heart disease mortality and morbidity in patients with non-insulin dependent diabetes. Circulation. 88:1421-1430.