Omega-3 fish oils reduce heart disease, vitamin D and fish oils do not seem to affect cancer.

At the recent American Heart Association and Congress of Cardiology, two very important studies were presented. The first (VITAL) trial followed 26,000 people over five years, some had vitamin D, some had fish oils (1 g daily), some have both and some have none. They looked at the incidence of cancer, and also cardiovascular events which they described as heart attacks, strokes and heart deaths. The conclusion was that there was no significant benefit from either vitamin D or fish oils, however, when they looked at just heart disease (and removed stroke) there was a 30% reduction in heart attack and heart deaths. (Because this was not prespecified, and was called a subgroup analysis, people are saying this is a negative trial!)

At the same meeting, the REDUCIT trial was published, with 3 g of fish oils taken daily, and in the study there was a 25% reduction in heart attack, cardiac events and death. This was incredibly significant (p<00000005), even more so because many of these people were already on full medical management including statin drugs.

It is amazing how the profession does its best to ignore complementary treatments, but I don't think there is any doubt now that omega-3 fish oils, provided it is quality oil (mercury free and pure) and taken an adequate doses does make an enormous difference to people with heart disease, or more importantly people at risk of heart disease. It is such an easy and innocuous preventive treatment, particularly when compared with most of the drugs we have available.
I believe that everybody at risk of heart disease or with disease should be taking 3 g of omega-3 fish oils per day.