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Fish oil & Vitamin D: do they help prevent disease?

Dr Ross Walker
Friday, November 23, 2018

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In a recent addition of the New England Journal of Medicine, there were two original articles and an editorial discussing a large placebo controlled, randomised study of 25,871 people in the United States, using what’s known as a 2 X 2 factorial design, which involved fish oil, vitamin D and placebo. There were four possible combinations i.e. fish oil /placebo; Fish oil/vitamin D; vitamin D/placebo; double placebo.

The participants in the treatment arm received fish oil in a dose of 1g a day, which included 840mg of omega three. The dose of vitamin D was 2,000 international units. The study went for just over five years and the participants involved were males over 50 and females over 55, who had no prior history of heart disease or cancer.

The headlines in the popular media basically said vitamin D and fish oil supplements are of little benefit to heart health. I wrote an article a few months ago on a large meta-analysis of 79 trials, suggesting that fish oil was of no benefit for the prevention of heart disease involving around 112,000 participants.

The new study basically showed that the trial failed to reach its primary endpoints, which were a combination of major cardiovascular events and invasive cancer. Or in other words, taking fish oil in the dose administered in the trial along, with a modest dose of vitamin D for just over five years, didn’t appear to prevent much in the way of our common killers.

As I have stated in my previous blogs, you can’t take any short-term evidence i.e. five years or less, as proof for lack of benefit for supplementation. These studies reinforce this point but say nothing about the long-term benefits of regular supplementation. Interestingly, in this trial, there was a 28% reduction in non-fatal heart attack in the people taking the omega three preparation and a very difficult to explain 77% reduction in heart attack in the African-American population.

Thus, these particular trials won’t stop me recommending omega three and vitamin D because all the indirect evidence points to low vitamin D levels being associated with a number of diseases and good doses of omega 3 have been very beneficial for cardiovascular disease, albeit not showing reduction in cardiac death in the short term. But the encouraging trend in the reduction in heart attack, even over the short five-year period. A large meta-analysis published in Mayo Clinic Proceedings in January 2017, again showed no benefit from Omega 3 supplements in the short term but an 18% reduction in cardiovascular events in trials over five years.

Interestingly, at the recent American Heart Association meeting, there was a presentation using a pure form of omega 3 supplementation, known as Icosapent Ethyl (Vascepa) 4GMS daily in 8,179 people, with either existing heart disease (70% of those in the trial) or at high risk for the disease, which did appear to have dramatic effects in reducing cardiovascular disease in people already well treated with other cardiovascular medications. The dose of omega 3 used was much higher than used in the trials mentioned above and all the people in the trial had high triglyceride levels, which is another blood fat. This trial that went for just under five years, showed a 25% reduction in all major cardiac events.

Also, a large meta-analysis of 70 trials published as a Cochrane review, headed by Prof Philippa Middleton from Adelaide, has suggested that commencing omega 3 fatty acids at the 12-week mark in pregnancy reduces the risk for a premature birth less than 37 weeks by 11%, 42% reduction for a premature birth less than 34 weeks and the risk for a small baby by 10%. The review suggested that the dose of omega 3 needs to be somewhere between 500mg-1000mg daily, with at least 500mg of the specific omega 3, DHA.

 There’s a variety of other benefits for omega 3 fatty acids but as I constantly say, we must be in this for the long haul. If you wish to take supplements, whether they be a multi vitamin, omega 3s or any other supplement that has a reasonable evidence base, taking it for a few years will not have a particularly long-term impact on your health. It’s a bit like diet and exercise-being on a diet for a few months or exercising for a few months is of no real value, it must, and should be, a lifelong commitment.

Published: Friday, November 23, 2018

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