What to do about triglycerides
Are triglycerides a problem?
Dyslipidemia refers to abnormal levels of lipids in the blood: typically, elevated levels of total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C), elevated triglycerides (TG) and/or low levels of high density lipoprotein cholesterol (HDL-C). There is debate as to whether high TG themselves contribute to cardiovascular risk, or whether they are just a marker of risk because high triglycerides are linked to low HDL-C, obesity and type 2 diabetes . Whether high TG are a participant in- or just a spectator of - increased cardiovascular risk remains unclear.
What level should we aim for?
In Australia, reducing LDL cholesterol is the primary treatment target for the prevention and treatment of CVD, and is incorporated in absolute risk calculators recommended for use in general practice. However, in a full lipid profile blood test TG is usually measured as well. While there are no formalised Australian and New Zealand recommendations, the Victor Chang Cardiac Research Institute has developed targets in collaboration with lipid management experts :
IDEAL Less than 1.7mmol/L
HIGH More than 2.5mmol/L
Can triglycerides levels be lowered by diet and lifestyle?
The primary non-drug treatment for hypertriglyceridaemia is weight loss via energy restriction, increased exercise, high intake of long chain omega-3 fats (pharmacological doses), and little or no alcohol. In terms of diet type, the same principles apply as for cholesterol lowering: a well balanced, plant-based diet low in saturated and trans fats. However, high carbohydrate diets are not recommended because they have the adverse effect of increasing TG and reducing HDL, while lower carbohydrate diets lower TG and increase HDL-C.
This begs the question: how low in carbohydrate do you go? And, what do you replace the carbohydrate with?
How low (carb) do you go?
The US Institutes of Health Heart, blood and lung Institute says no more than 50% of energy should come from carbohydrates in people with high triglycerides and low HDL-C, and not even high-fibre intake has been convincingly shown to counteract the adverse effect of high carbohydrate intake . A meta-analysis of low carbohydrate diets for weight loss found significantly greater reductions in TG, even when weight loss was similar However the source of carbohydrate and the total dietary context do matter, as shown by the DASH diet which contained around 55% carbohydrate but it was delivered in 8-10 servings of vegetables and fruits, wholegrains and low fat dairy foods with limited discretionary foods and showed no adverse effects on TG. The OmniHeart Study and Women's Health Initiative Study did not show adverse effects of a higher carbohydrate intake within a healthy plant-based eating pattern either2. A higher proportion of fat (more than 30%E) in the diet reduces TG levels and especially so in people with type 2 diabetes . The type of fat you replace the carbohydrate with is important: unsaturated fats are best, especially polyunsaturated fats which are slightly better at lowering both TG and LDL-C . Epidemiological evidence as well as intervention trials show a Mediterranean style eating pattern is also good for prevention and management of high TG.
A recent study by Australian researchers at the CSIRO achieved good results on a very low carb diet in obese subjects with type 2 diabetes. They demonstrated beneficial changes in TG and HDL-C as well as LDL-C in a hypocaloric, very low carbohydrate, high unsaturated fat diet : 14% carbohydrate (
What about type of carbohydrate?
Dietary management guidelines for elevated lipids include advice to choose wholegrain, high fibre, lower GI and less refined carbohydrate choices. Higher fibre diets have been shown to lower TG in people with type 2 diabetes, and be associated with lower TG levels in non-diabetic populations. There are likely to be benefits of diets low in glycemic index (GI) or glycemic load (GL) but the published evidence is mixed with some studies showing improved TG levels with low GI or GL diets, and others finding no effect. This may be attributable to methodological issues with measuring and reporting GI in dietary intake data.
What about sugars?
The US NHANES 1999-2006 data found the lowest TG levels were associated with added sugars intakes of less than 10%E . A New Zealand meta-analysis of randomised controlled trials found that higher free sugar intakes were associated with raised triglyceride levels , however the heterogeneity of the lower sugar study diets (in both sugar type and amount) did not suggest an optimal target, and the analysis did not account for starch content or GI. Fructose increases TG, although in very high amounts that bear little resemblance to typical intakes. A meta-analysis examining the effects of swapping other carbohydrates for pure fructose in people with diabetes found TG raising effects from more than 60g daily for up to four weeks. Few people actually consume pure fructose in Australasia (although it is available as a low GI tabletop sweetener) and an estimate of total daily 'free sugars' intake in Australian adults is 65g suggesting our fructose intake is low.
The bottom line
Weight loss reigns supreme when it comes to lowering triglycerides and it doesn't appear to matter as much how this is achieved in terms of macronutrient profile of the diet – which ever diet causes the best weight loss and can be sustained, wins. In term of diet quality, a healthful eating pattern is imperative, containing a low proportion of saturated fat as per current guidelines for lipid management. Reduction or moderation in carbohydrate quantity and replacing this with unsaturated fat is effective, as is improving carbohydrate quality by choosing wholegrain, high fibre and lower GI sources although the effect is smaller. Limiting added sugars as per Dietary Guidelines is prudent in achieving optimal carbohydrate intake.
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AHA Scientific Statement. Triglycerides and cardiovascular disease. Circulation 2011;123:2292-2333. Available at URL http://circ.ahajournals.org/content/123/20/2292.full, accessed 16.4.16
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