*Geek Box: Triglycerides & CVD Risk
Triglycerides are known to increase on higher carbohydrate diets, and decrease on low-carbohydrate diets. This is often oversimplified to ‘high = bad, low = good’, when in fact this is contextual. What is often measured is fasting circulating triglycerides, not the triglyceride content of lipoproteins that transport lipids through the blood.
Circulating blood plasma triglycerides are an indiscriminate measure of all triglyceride-carrying lipoproteins, regardless of their size and density [i.e., it does not differentiate between triglycerides in chylomicrons, VLDL, or LDL].
This is important, because while historically there have been strong associations between measured TGs and cardiovascular risk, these associations fall away when non-HDL-cholesterol is adjusted for. Non-HDL-C provides an estimate of all atherogenic lipoproteins – VLDL, IDL, LDL – and thus it appears that elevated TGs as a risk was in fact a proxy for atherogenic triglyceride carrying lipoproteins.
High triglycerides alone may not necessarily be an indication of anything adverse, as evidence by a condition known as ‘familial chylomicronaemia’, in which TGs in chylomicrons and large VLDL are significantly elevated. However, atherosclerosis does not develop due to the size of these lipoproteins preventing their penetrating the arterial intima.
Conversely, combined elevated cholesterol and TGs may result in the accumulation of atherogenic triglyceride-rich lipoproteins.. High triglycerides in the context of high LDL and low HDL is a distinctly high-risk profile, known as the ‘atherogenic lipoprotein phenotype’. A further issue is what to measure: there is gathering support for post-prandial triglycerides being more predictive of heart disease than fasting triglycerides.