Do you use fish oil or vitamin D? Large studies provide long-awaited answers about who does and does not benefit from these popular nutrients.
Fish oil taken by healthy people, at a dose found in many supplements, showed no clear ability to reduce heart or cancer risks. Same for vitamin D.
But higher amounts of purified, prescribed fish oil cut heart problems and heart-related deaths in people with high triglycerides, a type of fat in the blood and other risks for heart disease. Doctors applauded the results and said they could propose a new treatment option for hundreds of thousands of patients like this.
Up to 10 percent of American adults use fish oil. Even taking more vitamin D, despite no major studies to support the many health claims that have been made.
"Those who distribute it promote it as good for everything," but in this final test, vitamin D showed "a great deal of nothing," said Dr. James Stein, a cardiac specialist at the University of Wisconsin-Madison. He had no role in the studies or links with the companies involved.
The results were unveiled on Saturday at an American Heart Association conference in Chicago and published by the New England Journal of Medicine.
About fish oil
These oils, also called omega-3 fatty acids, are found in salmon, tuna and certain other fish. They reduce triglycerides and inflammation and can have other effects. There are different types, including EPA and DHA.
In one study, 4 grams per day was prescribed Vascepa from Amarin Corp., which is concentrated EPA, in more than 8,000 patients with high triglycerides and a greater risk of heart problems for various reasons. They already used a statin such as Lipitor or Zocor to lower their cholesterol. Half got Vascepa and the rest as capsules for mineral oil.
After five years, about 17 percent of those who had Vascepa had one of these problems – a heart attack, stroke, heart-related death, or clogged arteries requiring medical care – compared to 22 percent of the others.
That was 25 percent less risk. Individually reviewed, heart attacks, heart-related deaths and strokes were all lower with Vascepa. Only 21 people should take Vascepa for five years to prevent one of the major problems studied – favorable opportunities, Stein said.
Side effects can be a concern: more people on Vascepa were hospitalized for an irregular heartbeat – 3 percent versus 2 percent of the comparison group. Doctors say that this is enigmatic, because other research suggests that fish oil lowers that risk.
The concern with cardiac arrhythmia is that it can increase the risk of a stroke, but there are fewer strokes among those on Vascepa, said research leader Dr. Deepak Bhatt from Brigham and the Women & # 39; s Hospital in Boston.
Vascepa costs about $ 280 per month; many insurers cover it. Amarin sponsored the study and some study leaders worked or consulted for the company.
In the other study, a lower daily dose of 1 gram of another type of fish oil was tested – an EPA / DHA combo sold as Lovaza or Omacor and in generic form – in 26,000 people without previous heart problems or cancer.
After about five years, the figures for a combination of heart attacks, strokes and other problems were similar for users of fish oil and a comparison group. Cancer rates and deaths were also similar.
There were fewer heart attacks in the fish oil group – 145 versus 200 in the reference group. The study leader, Dr. JoAnn Manson at Brigham and Women & # 39; s called that "a substantial benefit," but several independent experts disagreed with the way the study was set up to keep track of this and certain other results.
"These findings are speculative and should be confirmed in a separate study," said Dr. Steven Nissen, the Clinic of the Cleveland Clinic.
Both studies share a problem: the oils used for the reference groups, which may not have been a real placebo. The Vascepa study used mineral oil, which disrupts statin medicines, increases cholesterol and makes the comparison group worse and has made Vascepa look better than it really was.
In the other study, olive oil was used, which might have helped the comparison group better and possibly mask the possible benefit to the others of fish oil.
Leaders of both studies say that each effect of the comparison oils is not enough to change the main results, and independent experts agreed. But Nissen, who is conducting another fish oil study, uses corn oil as a comparison.
The & # 39; sunshine & # 39; vitamin
The Manson study also tested vitamin D, which makes the skin from exposure to the sun. It is difficult to get enough of food such as milk, eggs and oily fish, although there is now a lot of food enriched with it. Some studies have shown that people with lower D levels are more likely to develop cancer, but it is unknown whether supplements change that risk.
Participants in the study 2000 2000 international units D-3 (the most active form of vitamin D, also called cholecalciferol) or counterfeit vitamin pills.
Vitamin D did not affect the risk of heart attack or stroke or cancer development. After excluding the first two years of use, researchers saw fewer deaths from cancer among those on the vitamin – 112 versus 149 in the placebo group.
"Cancer can take years to develop", so a difference may not immediately appear, Manson said. "This looks promising" and people will be studied longer to see if the trend continues, she said.
Several other experts said that these figures merely indicate a possible benefit that requires more study.
"These" positive "results should be interpreted cautiously & # 39 ;, #, wrote Dr. Clifford Rosen of the Maine Medical Center Research Institute and Dr. John Keaney Jr. of the University of Massachusetts in a comment in the medical journal.