Omega-3 fatty acids don't improve cardiovascular risk factors in type 2 diabetes patients

By Nathan Seppa

Web edition: June 12, 2012

Ingredients in fish oil widely considered to have heart-healthy powers may not deliver in some people. People with type 2 diabetes, including many with a history of heart disease or hypertension, don’t seem to get a cardiovascular benefit from omega-3 fatty acids, the key ingredients in fish oil, researchers report June 11 in the New England Journal of Medicine.

“This is surprising,” says Paul Marik, a physician and nutritionist at Eastern Virginia Medical School in Norfolk. “Why it didn’t show a benefit is unclear.” Previous research has suggested that fish oil can also help against depression, sepsis, cancer, joint pain and neurological disorders. “I’m not sure that, based on this study, we should throw fish oil out the window,” Marik says.

The omega-3 fatty acids in fish oil lower blood levels of triglycerides, which have been linked to cardiovascular disease.

For the international study, Jackie Bosch, a medical epidemiologist at McMaster University in Hamilton, Ontario, and colleagues tracked 12,536 people with type 2 diabetes or prediabetic conditions who had been randomly assigned to take capsules of omega-3s or olive oil. Although people getting the omega-3s saw their triglyceride levels improve substantially more than those getting olive oil, people in the omega-3 group were no more or less likely to die of heart problems or even develop them. About 9 percent of people in the six-year study died of a heart ailment, regardless of their study group.

When no difference emerged between the groups, Bosch acknowledged being disappointed but says diabetes patients might represent a special group.

“We’re seeing that the population being studied actually matters,” she says.

Eating fish might have a greater effect than supplements, says Daan Kromhout, a nutritional epidemiologist at Wageningen University in the Netherlands. Omega-3 fatty acids in fish oil are valuable, he says, but full benefits might arise “from a combination of those nutrients plus selenium and vitamin D in fish. The whole package could play a role.”