Evidence review evaded key points, didn’t address other omega-3 benefits 07/25/2018
Last week witnessed publication of a review examining clinical studies on omega-3s and heart health.
The paper was commissioned by the Cochrane Collaboration, a well-respected organization dedicated to raising the standards and rigor of biomedical research.
All the authors were from British universities, and most — including study leader Lee Hooper, Ph.D. — were from the University of East Anglia.
The negative conclusions reached in the new Cochrane Collaboration review echo others that made headlines in recent years — despite their flaws and/or unfair framing of the evidence.
And as we reported last year, two recent evidence reviews came to positive conclusions: see Take Heart! Value of Omega-3s Vindicated, Again.
Importantly, the benefits of omega-3s from seafood extend well beyond their potential to protect heart health — which provides critical perspective when discussing their role in heart health.
These benefits include support for optimal brain health, eye health — and control of the chronic inflammation that drives major diseases ranging from cancer and other immune disorders to arthritis and cardiovascular disease.
And this past May, the American Heart Association issued a scientific advisory, the press release for which was titled “Keep saying yes to fish twice a week for heart health”.
The AHA advisory didn’t recommend omega-3 fish oil supplements for preventing heart disease, citing “… a lack of scientific evidence …”.
Regardless, a large body of clinical evidence supports the value of omega-3 fatty acid supplements for brain, immune, eye, developmental, and overall health.
To learn more, visit our Newsletter Archive, and click any of the health topics listed in the right-hand column under "Omega-3 Fatty Acids".
What did the new review conclude?
The authors of the new Cochrane Collaboration review examined 79 randomized clinical trials involving 112,059 people — but judged only 25 studies “highly trustworthy” — i.e., well designed and conducted.
Most of those 25 better-designed studies compared the effects of taking omega-3 fish oil supplements or placebo pills on the risk for developing cardiovascular disease, falling victim to sudden cardiac death, and experiencing a heart attack or stroke.
Only a few studies measured the effects of fish intake on heart health, versus supplemental omega-3s.
All the clinical trials covered by the review lasted at least 12 months and involved both men and women — some healthy and others with existing cardiovascular illnesses — from North America, Europe, Australia, and East Asia.
The Britain-based Cochrane team concluded that supplemental omega-3 fish oil provides little if any benefit on most outcomes that they measured, including adverse cardiovascular events (e.g., sudden cardiac death, heart attack, stroke) and the risk of death from any cause.
However, they did find that seafood-source omega-3s modestly reduce blood levels of triglycerides and some other fats, while raising levels of HDL ("good") cholesterol: changes believed to help protect against heart disease.
As lead author Lee Hooper, Ph.D., said in a press release, “The review provides good evidence that taking long-chain omega 3 (fish oil, EPA or DHA) supplements does not benefit heart health or reduce our risk of stroke or death from any cause [and] while oily fish is a healthy food, it is unclear from the small number of trials whether eating more oily fish is protective of our hearts.”
That’s a sweeping conclusion, to say the least, especially since it flies in the face of other recent reviews of the clinical evidence, and downplays or ignores critical “confounding factors”, most of which were stressed by one of the scientists whom the Cochrane Collaboration asked to comment on the findings.
Let’s examine at those critical comments, and review reasons why it’s still very smart to eat plenty of fatty fish and take omega-3 fish (or vegan algae) oil supplements.
Expert commenter stressed the review’s strict limitations
The Cochrane Collaboration solicited comments from three British scientists not involved in the study.
Two of those commenters endorsed the reviews conclusions, but their comments were remarkably superficial, and failed to note its rather obvious shortcomings.
Fortunately, points made by the third scientist asked to comment — nutrition/diet professor emeritus Tom Sanders, PhD of King's College London — were right on target.
As Dr. Sanders noted, the evidence reviewers failed to account for several important factors. For clarity and ease of reading, we’ve paraphrased his original, technically-worded comments:
- Most of the clinical trials covered by the review involved people with pre-existing cardiovascular disease (CVD), making it unsafe to extrapolate the authors’ negative conclusions to people currently free of CVD.
- Most population studies indicate that high dietary intakes or blood levels of omega-3s reduce the risk for sudden cardiac death, which accounts for half of all heart-related deaths.
- Unsurprisingly, most trials involving cardiac patients found that supplemental omega-3s don’t deliver further, substantial risk reductions among those already taking blood pressure or cardiac drugs such as statins, aspirin, and beta-blockers.
- Most population studies link higher fish intakes with reduced risk of cardiovascular disease. (Fish — especially fatty fish like sardines, mackerel, and salmon — are the only food sources of the key long-chain omega-3s, EPA and DHA.)
- Nothing in the author’s conclusions contradict current worldwide dietary guidelines, which call for eating at least two portions of fish per week, including one serving of fatty, omega-3-rich fish. Two servings of fish per week delivers the equivalent of 200 to 400 mg of omega-3s (DHA and EPA) per day — a nearly perfect match for the 200 to 500 mg per day recommended by health authorities worldwide.
- The review detected evidence that — as found in prior studies — omega-3 fatty acids may help some patients with congestive heart failure.
Prominent voices push omega-6 fats, despite the absence of credible evidence
Widely quoted scientists like Walter Willet, M.D., of Harvard Medical School assert — based almost entirely on epidemiological, not clinical, evidence — that omega-6 polyunsaturated fats reduce heart risk, and that the dietary intake ratio of omega-6 to omega-3 fatty acids doesn’t matter to heart or overall health.
That “mainstream” position lacks scientific credibility, given that omega-3s reduce inflammation while excessive omega-6 intake promotes it — and a huge amount of lab, epidemiological, and clinical evidence links omega-3 fatty acids to better heart, brain, eye, and immune health.
Worse, the position taken by Dr. Willett and other widely quoted authorities ignores the large, growing body of evidence linking the average American’s historically unprecedented imbalance between intakes of omega-3 (too few) and omega-6 (too many) fats to damaging effects on heart, brain, immune, and metabolic health.
Twice — in 2015 and 2018 — Prof. Hooper’s Cochrane Collaboration team led reviews of the available clinical evidence concerning the effect of omega-6 fats on cardiovascular risk, and her team’s findings either failed to support or contradict mainstream advice to load up on those fats.
For their 2015 review, they looked for randomized, controlled clinical trials that tested the effects of increasing intake of omega-6 fats in healthy people and/or people at risk of heart disease — and found none:
“We found no studies examining the effects of either increased or decreased omega-6 on our primary outcome CVD clinical endpoints and insufficient evidence to show an effect of increased or decreased omega 6 intake on CVD risk factors such as blood lipids and blood pressure.” (Al-Khudairy L et al. 2015)
Hooper’s team characterized the follow-up evidence review published earlier this year as the most comprehensive to date: “This [2018 evidence review] is the most extensive systematic assessment of effects of omega-6 fats on cardiovascular health, mortality, lipids and adiposity to date, using previously unpublished data.”
And their conclusions don’t support the mainstream position on omega-6 fats: “We found no evidence that increasing omega-6 fats reduces cardiovascular outcomes other than MI [heart attack], where 53 people may need to increase omega-6 fat intake to prevent 1 person from experiencing MI. Increased omega-6 fats reduce serum total cholesterol but not other blood fat fractions or adiposity [being overweight or obese].” (Hooper L et al. 2018.)
While they found that increasing dietary intake of omega-6 fats might reduce the risk for heart attack in one out of 53 people, there’s ample evidence that that kind of increase would have damaging effects on their overall health — a devil’s bargain that no one should accept.
Omega-3s: Essential to brain, eye, bone, and immune health
Omega-3 EPA and DHA are essential to life itself, and a very large body of evidence indicates that diets rich in both promote optimal health.
To learn more about research on their roles in key body systems, click on the topics listed in our Newsletter Archive under “Omega-3 Fatty Acids” (e.g., Bone Health, Brain Health, Eye Health, Heart Health) in the right-hand column titled “Articles by Topic”.
In fact, there’s little doubt that the average American needs to consume more seafood-source omega-3s. A landmark Harvard study estimated that, as we reported, America's Omega-3 Deficiency May Cause 84,000 Premature Deaths.
And that disturbingly large number doesn't include the many more Americans thought to suffer ill health due to their shortage of dietary omega-3 fats and pro-inflammatory excess of omega-6 fats.
The fundamental, anti-inflammatory effects of omega-3s from seafood
The authors of the new evidence review did not focus on the proven anti-inflammatory power of seafood-source omega-3s.
That was a serious omission, since omega-3s are essential to resolving (ending) the chronic, inappropriate inflammation that underlies cardiovascular disease.
Chronic inflammation afflicts many Americans — without their knowledge — and it’s largely fueled by the heavy overload of omega-6 fats in the standard American diet.
America’s omega-6 overload stems largely from the cheap, omega-6-laden vegetable oils (corn, soy, safflower, sunflower, cottonseed) used in home cooking and the packaged, restaurant, and prepared deli dishes made with those oils.
For more on this topic, see our Omega-3/6 Balance page, and the “Out of Balance” video found at the top, which features interviews with leading fatty acid scientists.
Vital Choice founder Randy Hartnell recently heard a powerful presentation by from Harvard Medical School’s Dr. Jing Kang, M.D., Ph.D., concerning omega-3s and inflammation
Dr. Kang summarize the growing evidence that omega-3s are essential to controlling the chronic inflammation that undermines cardiovascular, brain, and immune health — a “silent” plague driven by the average American’s sedentary lifestyle and poor diet, high in refined carbohydrates and omega-6 fats.
In other words, many Americans need more seafood-source omega-3s just to counterbalance the deleterious long-term effects of their diets.
People who consume omega-3 and omega-6 fats in the approximately equal amounts that humans consumed until very recently may not need very much fish or supplemental omega-3s to achieve optimal health — but the diets of very few Americans fit that description.
What do omega-3s do in the body?
Omega-3 fatty acids come in two basic forms, with distinctly different health impacts:
- Short-chain (polyunsaturated) omega-3 ALA from certain plant foods.
- Long-chain (highly unsaturated) omega-3s (EPA and DHA) from seafood and fish oil.
The body only needs omega-3 EPA and DHA to survive and thrive, and can only make very small amounts of EPA from plant-source omega-3 ALA.
Omega-3 ALA abounds only in flaxseed, walnuts, chia seed, hemp seed, with much smaller amounts occurring in dark leafy greens like spinach, collards, chard, and kale. (Avocados also contain small amounts of ALA, but 10 times more competing omega-6 fat.)
Our bodies can only convert a small proportion of EPA into DHA, making it smart to get ample amounts of both omega-3s — especially DHA — from seafood or supplements.
Fish, shellfish, zooplankton (e.g., krill), algae, and certain aquatic plants (e.g., seaweed) are the only food sources of EPA and DHA — which explains why EPA and DHA are sometimes called "marine" omega-3s.
Among marine foods, fatty fish like salmon, tuna (especially albacore), sardines, mackerel, herring, anchovies, and sablefish are the richest sources of EPA and DHA, by far.
Omega-3 DHA and EPA occur in almost all human cells and are essential to our survival and health:
Omega-3 DHA (docosahexaenoic acid) plays essential roles in the brain, eyes, nervous system, and immune system, including inflammation control:
- Essential to development of the growing brain.
- Plays key roles in the regulation of oxidation and inflammation.
- Essential to the human brain and nervous system, and to thinking and memory. Brain tissues average 50 percent fatty acids by weight, and DHA averages about 15 percent of those.
- Regulates the expression of dozens of "working" genes in the brain and stimulates growth of the connections between brain cells (neurons).
- Essential to eye structure and functions, and to infants' eye development.
- DHA is the dominant fatty acid in sperm and is critical to male reproductive health.
Omega-3 EPA (eicosapentaenoic acid) is essential to the immune system, especially inflammation control, and appears to support and promote healthy mood and good mental health.
In short, while most people can survive if they consume only plant-source omega-3s, the average American can thrive only if he or she gets plenty of seafood-source omega-3s.
- Al-Khudairy L, Hartley L, Clar C, Flowers N, Hooper L, Rees K. Omega 6 fatty acids for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2015 Nov 16;(11):CD011094. doi: 10.1002/14651858.CD011094.pub2. Review.
- American Heart Association. Keep saying yes to fish twice a week for heart health. May 17, 2018. Accessed at https://newsroom.heart.org/news/keep-saying-yes-to-fish-twice-a-week-for-heart-health
- Cochrane Collaboration. New Cochrane health evidence challenges belief that omega 3 supplements reduce risk of heart disease, stroke or death. Wednesday, July 18, 2018. Accessed at https://uk.cochrane.org/news/new-cochrane-health-evidence-challenges-belief-omega-3-supplements-reduce-risk-heart-disease
- Cochrane Collaboration. Scientific expert reaction to Cochrane Review on omega-3 fatty acids. Wednesday, July 18, 2018. Accessed at https://www.cochrane.org/news/scientific-expert-reaction-cochrane-review-omega-3-fatty-acids
- Hooper L et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Heart Group, 18 July 2018 DOI: 10.1002/14651858.CD003177.pub3. Accessed at http://cochranelibrary-wiley.com/doi/10.1002/14651858.CD003177.pub3/full
- Hooper L et al. Omega-6 fats for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2018 Jul 18;7:CD011094. doi: 10.1002/14651858.CD011094.pub3. [Epub ahead of print] Review.