Triglycerides

Triglycerides are the fats in which your body stores and transports energy: three fatty acids on a glycerol backbone, the same molecules as the fat in your food and in your fat tissue. After a meal your gut packs the fat from your food into large particles that carry it to muscle and fat tissue. Between meals your liver makes them itself, from surplus sugar and alcohol, and sends them into the bloodstream in particles. What is not burned right away goes into your fat tissue. Triglycerides are therefore a mirror of your energy balance. They rise after a meal, with alcohol, and persistently with a metabolism taking in more than it processes. With insulin resistance that happens most strongly: the liver keeps making triglycerides and the muscles take them up more slowly, so the value stays high even fasting. Your report shows one number in millimoles per litre (mmol/L). Because the value responds so strongly to food, it matters whether you were fasting, and that is why triglycerides have more than one limit: a measured range of what healthy people have, and separate limits for fasting and non-fasting blood. The table further down sets them side by side.

Raised triglycerides are rarely the main culprit, but they are one of the earliest signals of a metabolism tipping over. They belong to a recognisable pattern: belly fat, insulin resistance, little exercise, a low HDL. In that pattern the LDL particles are smaller and denser too, and those are the ones that enter the artery wall easily. High triglycerides therefore say something about your risk, even when your LDL looks normal, and often years before your blood sugar rises. For anyone who wants to stay healthy that is the value of the number: it responds first, in both directions. Anyone who changes what they eat sees it here first, weeks before LDL moves. The link with cardiovascular disease is weaker than for LDL, though, which is why there is no target: bringing triglycerides down alone with drugs did not clearly lower the risk. What does work is tackling the pattern beneath them, and triglycerides respond to that faster than any other blood fat value. At very high values the question changes. Above 10 mmol/L it is no longer about your arteries but about your pancreas: triglycerides can then trigger an inflammation of the pancreas, and that is the only situation in which they are treated in their own right.

A raised value almost always comes from the metabolic pattern: belly fat, little exercise, plenty of fast carbohydrates and sugar, alcohol, and poorly controlled diabetes. Very high values without an identifiable cause are rare and can be inherited. A low value is not a finding. It usually means you were drawn fasting, that you use little sugar and alcohol, or that a change is working; there is no lower limit below which something is wrong. Triglycerides are the blood fat value that responds most to lifestyle, often within weeks. The levers, in order of effect: less alcohol, because your liver turns it directly into triglycerides; less sugar, soft drinks, juice and fast carbohydrates, for the same reason; losing weight around the middle; and daily exercise, which sets the muscles to using triglycerides as fuel. Oily fish and more fibre help too. Then measure fasting again, as the previous time, or you are comparing two different things. To read your own number it helps to remember two limits and treat the rest as nuance: drawn non-fasting, above 2 mmol/L is abnormal, and above 10 mmol/L the pancreas comes into view. The nuance: measured fasting, above 1.7 mmol/L already counts as a marker of increased risk, and if the non-fasting value comes out above 5 mmol/L it is repeated fasting, because a meal can lift the value a good deal temporarily. Always read triglycerides beside HDL and LDL: high triglycerides with a low HDL is the pattern that deserves attention, and with high triglycerides the calculated LDL becomes unreliable and non-HDL is the better number.