Studies examining the effect of omega-3 fatty acids in healthy people have consistently shown a 20% to 50% reduction in triglyceride levels from consuming 2–3 grams of omega-3 per day. This effect is even greater in people with elevated triglycerides, including those with diabetes. Reductions in triglycerides and increases in HDL (high-density lipoprotein, or “good”) cholesterol have been reported in people with both Type 1 and Type 2 diabetes who consume omega-3 fatty acids, generally DHA and EPA together.
Reductions in LDL (low-density lipoprotein, or “bad”) cholesterol have also been shown in similar studies of people with both types of diabetes, although increases have also occurred. These increases are most likely offset by increases in HDL cholesterol and decreases in triglycerides. Furthermore, the type of LDL cholesterol that is produced in people who consume more omega-3 is less likely than others to cause heart disease. This is because it contains more omega-3 fatty acids, giving it a larger particle size. Ingestion of omega-3 fatty acids also reduces blood pressure in people with either Type 1 or Type 2 diabetes.
Recent research has not convincingly shown that omega-3 fatty acids improve blood glucose control in people with diabetes — but studies conducted so far may not have had enough subjects, so larger studies are still needed to examine this issue. So far, no studies of humans have looked at whether diabetic complications may be reduced by omega-3 fatty acids, but experiments with animals have suggested that omega-3 may prevent diabetic neuropathy (nerve damage).
Clinical trials in progress will further examine the effects of omega-3 fatty acids in people with diabetes. These include ASCEND (A Study of Cardiovascular Events in Diabetes), which will look at people with Type 1 and Type 2 diabetes, and the AFORRD (Atorvastatin in Factorial with Omega-3 fatty acids Risk Reduction in Diabetes) trial, which will examine people with Type 2 diabetes. Preliminary results from AFORRD have demonstrated reductions in triglycerides of 5.6% but no reduction in cardiovascular disease risk.
The ORIGIN (Outcome Reduction with Initial Glargine Intervention) trial will examine the use of diabetic insulin glargine — a synthetic, long-acting insulin — and omega-3 fatty acids in over 12,000 people with diabetes. This trial will be particularly important for understanding the use of omega-3 fatty acids in diabetes control, due to the large number of people enrolled in it.
Omega-3 fatty acids and heart disease
People with diabetes have a risk of developing heart disease three to four times greater than the general population. Studies of omega-3 fatty acids and heart disease are therefore of particular interest to people with diabetes. The consumption of high levels of omega-3 fatty acids, both DHA and EPA, for heart health has been referred to as “the Eskimo diet,” based on several studies showing that Greenland Inuits (Eskimos) have a lower prevalence of coronary heart disease than Western Europeans, specifically Scandinavians. Other populations that consume high levels of fish, such as the Japanese and Alaskans, similarly have a decreased incidence of death from coronary heart disease. Several studies of omega-3 fatty acids in Western populations have found that a higher omega-3 fatty acid intake predicts a lower incidence of heart disease.
Eating omega-3–rich diets has been shown to prevent heart attacks, possibly because omega-3 fatty acids prevent blood clotting and heart irregularities in addition to lowering triglyceride levels and increasing HDL cholesterol. In fact, the American Heart Association recommends that people eat fish high in both EPA and DHA — particularly fatty fish such as mackerel, sardines, albacore tuna, and salmon — at least twice a week. It also recommends that people with documented coronary heart disease increase their intake of total DHA and EPA to about 1 gram per day, either in the form of fish or in a supplement. People with elevated triglycerides should consider consuming 2–4 grams per day, although according to the association, people who take over 3 grams daily should be monitored by a physician due to a theoretical increased risk of bleeding, despite the lack of firm clinical evidence of this. For more about these recommendations, visit www.americanheart.org/presenter.jhtml?identifier=4632.