A few years ago, the U.S. FDA approved a qualified health claim for animal foods that contain long-chain omega-3s:
“Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.” (FDA 2004)
In 2000, FDA announced a similar qualified health claim for dietary supplements (i.e., fish or algae oil) containing EPA and DHA.
Fish, shellfish, algae, and eggs from chickens fed DHA are the only foods that provide substantial amounts of EPA and/or DHA.
Key Points
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Finding in mice reveals an important new way that omega-3s guard arteries.
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Finding adds a fifth protective mechanism to the four discovered previously.
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Only omega-3s from fish deliver the full benefits associated with this class of fats. |
Long-chain omega-3s (EPA and DHA) are the only kind the body actually uses.
The short-chain omega-3s in plant foods such as leafy greens, walnuts, and flaxseed do not have the same documented heart benefits. And the body only turns two to 10 percent of plant-source omega-3s into EPA and DHA.
Findings shed new light on omega-3s’ artery effects
It’s been thought that omega-3s reduce the risk of strokes, sudden cardiac death, and second heart attacks by doing four things:
- Lower blood triglyceride (fat) levels.
- Raise levels of “good” (HDL) cholesterol.
- Lower levels of all non-HDL cholesterol
- Reduce risk of arrhythmias
New evidence from Columbia University Medical Center expands our understanding of how fish-derived omega-3 fatty acids may reduce the risk of cardiovascular disease (Chuchun L et al. 2009).
In fact, their findings suggest a new, fifth way in which omega-3s reduce cardiac risks.
A team led by Richard J. Deckelbaum, M.D., found that in mice, a diet rich in omega-3s prevented accumulation of fat in the main artery (aorta) leaving the heart.
The beneficial actions of fish oil that block cholesterol buildup in arteries were observed even at high fat intakes.
The study involved three groups of mice, each fed a distinctly different diet:
- Balanced diet.
- Western-style diet high in saturated fat.
- Diet rich in omega-3 fatty acids from fish oil.
The Columbia University team found that the omega-3s in fish oil reduced the entry of LDL cholesterol into artery walls.
As a result, the mice fed fish oil collected much less cholesterol in their aortas.
They found that this effect was related to the ability of omega-3s to markedly decrease levels of a molecule called lipoprotein lipase, which — in mice and humans alike — traps LDL in artery walls.
This discovery could help explain the documented heart-health benefits of higher-than-average fish and omega-3 intake.
Dr. Deckelbaum advises those interested in increasing omega-3 intakes to either eat more fatty cold water fish or take fish oil supplements (CUMC 2009).
We heard Dr. Deckelbaum speak eloquently about an overlooked nutritional cause of heart disease — namely, Americans’ excessive intake of omega-6 fatty acids — at Dr. Andrew Weil’s 2005 Nutrition & Health Conference.
Read on to learn more about that, and how omega-3s affect the different kinds of cholesterol found in the blood, to beneficial effect.
Clarifying the cholesterol and arterial impacts of omega-3s
Remember that when doctors talk about types of cholesterol such as LDL and HDL, they are really talking about different lipoprotein “packages” in which cholesterol is carried.
The body uses high-density lipoproteins (HDLs) to remove cholesterol from the blood, and it uses various kinds of low-density lipoproteins (LDLs) to carry cholesterol through the blood.
Having high levels of HDL cholesterol is good for cardiovascular health, but it is critical to understand that having “high” levels of LDL cholesterol is not inherently unhealthful.
In fact, the statistical links between LDL levels and heart risk are weak, with many persons dying from heart disease despite having “low” cholesterol levels, and vice versa.
Instead, the arterial plaque-buildup that defines arteriosclerosis and resulting cardiovascular disease gets created when LDL and other low-density carriers of cholesterol become oxidized by free radicals.
And those free radicals result from inflammation in the artery wall and blood.
This is why researchers at the National Institutes of Health (and around the world) increasingly point to excessive — hence, pro-inflammatory, artery-irritating — intake of omega-6 fatty acids as the true nutritional cause of cardiovascular disease.
(Omega-6 fatty acids abound in common vegetable oils, the packaged and prepared foods made with these oils, and in grain-fed meats, poultry, and farmed fish.)
Of course, other factors — primarily stress, sedentary lifestyles, diets high in empty calories, and genetic profiles – also play major roles in cardiac risk.
We should note that omega-3s often raise levels of LDL cholesterol slightly, but that happens mostly in people with high triglyceride levels, and — for the reasons we just explained — is not in itself a cause of concern.
This is why we are always careful to note that omega-3s do not “lower cholesterol” in the way that statin drugs (e.g., Lipitor) — which lower LDL cholesterol levels very substantially — are designed to do.
However, omega-3s tend to lower levels of all non-HDL types of cholesterol.
This effect of omega-3s is very significant, for three reasons (Bays H 2008; Bays HE et al. 2008):
- Non-HDL cholesterol includes all of the cholesterol carried by oxidation-susceptible — hence, plaque-promoting — lipoproteins, not just LDL;
- Having high blood levels of all non-HDL cholesterol predicts risk of arteriosclerosis better than high LDL levels alone do;
- After LDL-lowering treatment goals have been reached, reduction of total non-HDL cholesterol is a recommended secondary treatment target in patients with high blood triglyceride levels (200 mg/dl or more).
Discovery of new protective power supports stronger health claim
When it comes to evaluating a nutrient’s potential to help prevent disease, scientists look for three things.
First, epidemiological studies must link higher intake of a given nutrient and reduced rates of a disease.
Second, positive indications from epidemiological studies must be backed by evidence from solidly designed clinical trials (randomized, double-blind, and placebo-controlled).
Last, but not least, laboratory evidence from test tube and animal studies must demonstrate ways in which the nutrient could reduce disease risk.
Interestingly, U.S. drug-approval regulations do not require laboratory evidence showing how or why a drug works, before the FDA can authorize its use.
Consequently, we still don’t know how many major drugs work, decades after they were approved for use.
In fact, if understanding of mechanisms were required under U.S. law, we’d have to pull dozens of major pain, heart, and depression drugs off the market.
Sources
- Bays H. Rationale for prescription omega-3-acid ethyl ester therapy for hypertriglyceridemia: a primer for clinicians. Drugs Today (Barc). 2008 Mar;44(3):205-46.
- Bays HE, Tighe AP, Sadovsky R, Davidson MH. Prescription omega-3 fatty acids and their lipid effects: physiologic mechanisms of action and clinical implications. Expert Rev Cardiovasc Ther. 2008 Mar;6(3):391-409. Review.
- Columbia University Medical Center (CUMC). Columbia Research Shows Novel Benefits of Fatty Acids in Arteries. February 5, 2009. Accessed online at http://www.cumc.columbia.edu/news/press_releases/090205DeckelbaumFishOil.html
- Davidson MH, Stein EA, Bays HE, Maki KC, Doyle RT, Shalwitz RA, Ballantyne CM, Ginsberg HN; COMBination of prescription Omega-3 with Simvastatin (COMBOS) Investigators. Efficacy and tolerability of adding prescription omega-3 fatty acids 4 g/d to simvastatin 40 mg/d in hypertriglyceridemic patients: an 8-week, randomized, double-blind, placebo-controlled study. Clin Ther. 2007 Jul;29(7):1354-67.
- FDA. FDA Announces Qualified Health Claims for Omega-3 Fatty Acids. FDA News, September 8, 2004. Accessed online at http://www.fda.gov/bbs/topics/news/2004/new01115.html
- Jung UJ, Torrejon C, Tighe AP, Deckelbaum RJ. n-3 Fatty acids and cardiovascular disease: mechanisms underlying beneficial effects. Am J Clin Nutr. 2008 Jun;87(6):2003S-9S.
- Qi K, Fan C, Jiang J, Zhu H, Jiao H, Meng Q, Deckelbaum RJ. Omega-3 fatty acid containing diets decrease plasma triglyceride concentrations in mice by reducing endogenous triglyceride synthesis and enhancing the blood clearance of triglyceride-rich particles. Clin Nutr. 2008 Jun;27(3):424-30. Epub 2008 Mar 24.
- Simoens CM, Deckelbaum RJ, Massaut JJ, Carpentier YA. Inclusion of 10% fish oil in mixed medium-chain triacylglycerol-long-chain triacylglycerol emulsions increases plasma triacylglycerol clearance and induces rapid eicosapentaenoic acid (20:5n-3) incorporation into blood cell phospholipids. Am J Clin Nutr. 2008 Aug;88(2):282-8.
