Taking fish oil or vitamin D? Great studies provide long-awaited answers to who does and do not benefit from these popular nutrients.
Fish oil taken by healthy people, in a dose found in many supplements, showed no clear ability to lower the risk of heart disease or cancer. Same for Vitamin D.
But higher amounts of purified prescription fish oil crushed heart problems and heart related deaths among people with high triglycerides, a type of fat in the blood and other risks of heart disease. Doctors cheered the results and said they could propose a new treatment option for hundreds of thousands of patients like these.
Up to 10 percent of American adults take fish oil. Even more, vitamin D, despite no major studies, supports the many health claims made for it.
"Those who peddle promote it so well for everything," but in this definitive test, vitamin D showed "a great deal nothing", says Dr. James Stein, a cardiac specialist at the University of Wisconsin-Madison. He had no role in the studies or ties to the companies concerned.
The results were revealed 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 some other fish. They reduce triglycerides and inflammation and may have other effects. There are different types, including EPA and DHA.
One study tested 4 grams per day of Amarin Corps Prescription Vascepa, which is concentrated EPA, in more than 8,000 patients with high triglycerides and a greater risk of cardiac problems for various reasons. Everyone already took a statin like Lipitor or Zocor to lower cholesterol. Half received Vascepa and the rest, mineral oil capsules as a comparison.
After five years, approximately 17 percent of them on Vascepa suffered from one of these problems – heart attack, stroke, heart related death or obstructive arteries who require medical care – against 22 percent of the others.
It served a 25 percent reduction in risk. Looked at individually where heart attacks, heart related deaths and strokes were all lower with Vascepa. Only 21 people would have to take Vascepa for five years to prevent one of the most important problems being studied – favorable odds, Stein said.
Side effects can be a problem: More people at Vascepa in hospital for an irregular heartbeat – 3 percent compared to 2 percent of the comparison group. Doctors say it's puzzling because other research suggests that fish oil reduces the risk.
The cause of the cardiac rhythm problem is that it may increase the risk of stroke, but there were fewer strokes among them at Vascepa, says study leader Dr. Deepak Bhatt from Brigham and Women's Hospital in Boston.
Vascepa costs around $ 280 a month; Many insurance companies cover it. Amarin sponsored the study and some study leaders work or consult for the company.
The second study tested a lower dose of 1 gram of another type of fish oil – an EPA / DHA combination sold as Lovaza or Omacor and in generic form – in 26,000 people without previous heart problems or cancer.
After about five years, the rate for a combined action of heart attacks, stroke and other problems was similar to fish oil users and a comparison group. Cancer rates and deaths were also similar.
There were fewer heart attacks in the fish oil group – 145 to 200 in the comparison group. The study leader, Dr JoAnn Manson at Brigham and Women, called that "a big advantage", but several independent experts were dissatisfied due to the way the study was set up to track this and some other results.
"These results are speculative and would have to be confirmed in a separate attempt," said Cleveland Clinic Dr Steven Nissen.
Both studies share a problem: the oils used for the comparison groups, which may not be true placebos. The Vascepa study used mineral oil that interferes with statins medicine, raises cholesterol and may have made the comparative group more dangerous and made Vascepa better than it really was.
The second study used olive oil, which may have helped the comparison group, better, possibly masking any benefit for the other from fish oil.
Leaders of both studies say no effect from comparison oils are not enough to change the main results, and independent experts agree. But Nissen, who leads another fish oil study, uses corn oil as a comparison.
Manson's investigation also tested vitamin D, as the skin does from sun exposure. It's hard to get enough of food like milk, eggs and oily fish, but many foods are now reinforced with it. Some studies have shown that people with lower levels of D are more likely to develop cancer, but it is not known if dietary supplements change the risk.
Study participants took 2000 international units of D-3 (the most active form of vitamin D, called cholecalciferol) or fake vitamin pills for five years.
Vitamin D does not affect the odds of having a heart attack or stroke or developing cancer. After eliminating the first two years of use, researchers saw fewer cancer deaths in vitamin 112 compared with 149 in the placebo group.
"Cancer can take years to develop," so a difference may not appear immediately, says Manson. "It looks promising" and people will be studying longer to see if the trend is on, she said.
Several other experts said that these figures only indicate an advantage that needs more study.
"These" positive "results must be interpreted with caution, says Dr. Clifford Rosen of the Maine Medical Center Research Institute and Dr. John Keaney Jr. of the University of Massachusetts in a commentary in medical journal.