Triglycerides and small LDL particles, small LDL and triglycerides: Like the Odd Couple, Oscar Madison and Felix Ungar, they come together in an uncomfortable situation.

Why would such an odd couple exist in the body? And why does it matter?

It all starts with triglycerides.

Consume any carbohydrate-candy, cookies, whole grain bread-and it turns to sugar within minutes after swallowing. In the liver, sugars are converted to triglycerides, which are then released into the bloodstream as very low-density lipoproteins, or VLDL.

VLDL particles are triglyceride-rich, commonly 30-60% triglycerides by weight. Because VLDL enters the bloodstream that is crowded with a number of other lipoproteins, such as LDL and HDL, VLDL particles influence the composition of these other particles. VLDL generously contributes triglycerides to LDL and HDL particles.

Once LDL and HDL particles are enriched in triglycerides, they become the target of an abnormal metabolic pathway that converts them to small LDL particles and small HDL particles. Small LDL particles are much more likely to cause heart disease, since they are more likely to provoke inflammatory reactions and are more oxidation-prone. Small HDL particles are less effective at providing the protective functions, including antioxidant functions.

So the first "domino" for this effect are the increased triglycerides and VLDL caused by . . .  carbohydrates.

Now, a quick quiz:

Question: What increases blood sugar more, whole wheat bread or a Snickers® bar?

Answer: Whole wheat bread increases blood sugar more than a Snickers® bar. (The glycemic index of whole wheat bread is 72, Snickers® bar is 41.)

In fact, with few exceptions, whole wheat and other grain products increase blood sugar more than any other known food. Yes, the foods we are advised to eat more of, "healthy, whole grains," raise blood sugar higher than many candy bars. (The exceptions are dried powdered starches, like cornstarch, potato starch, rice starch, and tapioca starch. Incidentally, these are the foods used to make most "gluten-free" foods.)

So carbohydrates, especially wheat products, also increase triglycerides and VLDL, which thereby increase production of small LDL and small HDL particles. 

Just about anybody who consumes sufficient carbohydrate can increase triglycerides and thereby small LDL. National guidelines advise keeping triglycerides at 150 mg/dl or less. At what level of triglycerides do small LDL particles begin to appear? 60 mg/dl and higher. So a "normal" triglyceride level of 120 mg/dl can be associated with a flagrant overabundance of small LDL particles.

The question over whether increased triglycerides are a risk factor for heart disease has been debated for years. While nearly all evidence point to the increased cardiovascular risk with triglycerides, skeptics argue that triglycerides do not predict heart disease independently, i.e., over and above risk identified by other measures, such as low HDL and small LDL particles.