Controlling cholesterol and triglycerides: are omega-3s helpful?
Triglycerides are the main constituent of animal and vegetable fats. In the bloodstream, fats are transported by lipoproteins, large complexes composed of proteins and fat molecules. Cholesterol and triglycerides travel through the blood within these complexes.
The cause of atherosclerosisDietary fats, sugars, and proteins consumed in excess of immediate energy requirements are converted into triglycerides by the liver.
They are transported from the bloodstream to all body districts: to fat cells, where they are deposited, or to other cells, where they are used as "fuel."
A certain amount of triglycerides in serum is therefore normal, indeed essential. However, an accumulation is deleterious: high blood triglyceride levels are thought to be a major cardiovascular risk factor. For this reason there is much interest in the components of the diet that can influence triglyceride levels.
Omega-3s in the reduction of triglycerides
Excess triglycerides and cholesterol in the blood can be controlled by long-chain omega-3 fatty acids.
This fact has been extensively documented by many studies. By long-chain omega-3 we mean some particular omega-3s:eicosapentaenoic acid (EPA) anddocosahexaenoic acid (DHA).
Their almost exclusive sources are fish oil and fat. It is precisely these molecules that can have important effects on our health because of their effectiveness in lowering triglycerides and non-HDL cholesterol.
A diet rich in Omega-3 EPA and DHA has an important effect on fat metabolism, as it causes a decrease in triglycerides both on an empty stomach and after meals.
These data were confirmed both in healthy volunteers and in those with hypertriglyceridemia, a pathological condition characterized by an excess of triglycerides in the blood.
The minimum required dose of omega-3 EPA and DHA to achieve a tangible effect on triglycerides is 1 gram per day, the amount that is taken from a diet rich in fatty fish. A comparison of several human clinical studies allowed even more precise conclusions to be drawn.
Consumption of 3-4 grams per day of EPA + DHA can result in a 25-45% reduction in blood triglycerides. This is confirmed for subjects with a high starting level of blood triglycerides, while the reduction is less significant for healthy subjects.
The increase in HDL cholesterol
Omega-3 consumption also influences total lipoprotein composition, particularly helping to raise "good" (HDL) cholesterol , thereby improving the cardiovascular risk profile.
Some clinical studies have focused on women, with a breakdown by age group. At menopause, consumption of 2.4 grams of EPA and 1.6 grams of DHA reduces plasma triglyceride levels by 26 percent, and reduces the triglyceride/HDL cholesterol ratio by 28 percent.
This report is very important for the prevention of coronary heart disease, as it provides reliable insights into the cardiovascular risk profile.
Reduction of cardiovascular riskThe reduction in TG/HDL ratio could mean a net prevention of heart disease for 27% of the women in the study. In contrast, no change due to hormone replacement therapy was observed. Similar data were obtained in a group of women of childbearing age.
A clinical study in hyperlipidemic children showed that a daily consumption of 1.2 grams of DHA increased the synthesis of antiatherogenic lipoprotein (HDL), known as the "good" cholesterol.
These inhibit the formation of fibrous plaques on the artery wall, plaques that at the origin of aneurysms or thrombotic events, and reduces the synthesis of atherogenic lipoproteins (LDL) significantly.
A recent study has shown that taking nutritional supplements (fish oil, bran, plant sterols) together with regular exercise can lower total cholesterol concentrations by 8-26%, but more markedly in LDL (8-30%) and triglycerides (12-39%), while increasing HDL cholesterol percentages by 2-8%.