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Omega-3s Seen to Fight Metabolic Syndrome
11/23/2006
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Scourge of developed world soluble by stressing exercise, veggies, beans, and seafood

by Craig Weatherby



As we’ve reported in the past, EPA and DHAthe long-chain marine omega-3s found only in fish and shellfishappear to aid weight control efforts in several ways.


But a growing body of evidence indicates that fatty fish and omega-3 supplements may also help prevent or ameliorate so-called "metabolic syndrome," when combined with exercise and Mediterranean-style diets rich in beans and colorful vegetables.


Key Points

  • US study finds omega-3 DHA blocks formation of fat cells in human cell cultures.
  • Evidence reviews detail ways omega-3s inhibit aspects of metabolic syndrome.
  • French studies link metabolic syndrome risk to omega-6 overload.
In contrast, metabolic syndrome is promoted by sedentary lifestyles and diets high in fried foods, sugary-starchy foods (white bread, pastries, pasta, and sweets), cooking and salad oils high in omega-6 fatty acids (corn, soy, canola, and cottonseed), and hydrogenated or trans fats (packaged and fast foods).


According to the American Heart Association, more than 50 million Americans have metabolic syndrome, which raises their risks of developing cardiovascular disease, stroke, and type 2 diabetes.


Metabolic syndrome is defined as having three or more of a half-dozen metabolic risk factors:

  • Abdominal obesity (excessive fat tissue in and around the abdomen).
  • High blood triglycerides, low HDL cholesterol and high LDL cholesterol: a state that fosters plaque buildups in artery walls.
  • Elevated blood pressure.
  • Insulin resistance or glucose intolerance (the body can’t properly use insulin or blood sugar).
  • Pro-thrombotic state that promotes dangerous clots (e.g., high fibrinogen or plasminogen activator inhibitor–1 in the blood).
  • Pro-inflammatory state (e.g., elevated C-reactive protein in the blood).

While there isn’t agreement on the precise parameters that push each of the above factors into the danger zone, there is no disagreement that the syndrome is very real and is largely responsible for the epidemic of cardiovascular disease and diabetes that’s exploding throughout the developed and developing worlds.


While no single nutrient can work miracles against metabolic syndrome, it’s looking more and more as though marine omega-3s rank number one among the dietary factors that can, along with increased exercise and reduced caloric intake, make a real dent in this dangerous trend.


We’ve come across five intriguing studies—four from this year and one from 2004—whose results do three things:

  1. Strengthen the case in favor of omega-3s as anti-obesity agents;

  2. Expand our understanding of omega-3s' role in the fight to maintain a youthful metabolism;

  3. Demonstrate the metabolic dangers of over-consuming omega-6 fatty acids, which dominate diets in developed Western countries and developing nations like China, which increasingly emulate unhealthful Western lifestyles.

Study #1: Georgia group finds omega-3 DHA blocks fat cell formation

In the newest study, lead author Hye-Kyeong Kim and his colleagues at the University of Georgia report that docosahexaenoic acid (DHA)one of the two main omega-3s in fish fat derails developing fat cells.


They proposed that if this finding raises people's omega-3 intakes, this would lead to leaner bellies and reductions in the risk of obesity and metabolic syndrome.


Previous studies have shown that omega-3s can cut body fat in rodents, but the mechanism behind these effects were unclear, and its been uncertain whether intake levels higher than average in America, but low enough to be easily attainable, could block development of fat cells and actually aid weight management.


The new results appear to provide positive, albeit preliminary, answers to both questions since they illuminate the mechanism of action and indicate that DHA can work at various tissue levels, which correspond to varying intake levels.


The Georgia-based team examined at the effects of DHA on cell growth, differentiation, cell death (apoptosis), and fat breakdown in human fat cells.


When they DHA to cells called pre-adipocyteswhich can develop into fat cells (adipocytes)they recorded a reduction in the number of fat cells that actually developed, even at the lowest levels of added DHA.


The researchers attributed this to DHA’s ability to induce apoptosis (programmed cell death) among the pre-adipocytes that were becoming fat cells.


They also reported that DHA decreased the accumulation of fat in the pre-adipocytes significantly, and did it in the dose-dependent manner that proves the omega-3 was really responsible for the effect.


As Dr. Kim’s team wrote, “These results demonstrate that DHA may exert its anti-obesity effect by inhibiting differentiation [of pre-adipocytes] to adipocytes. Therefore, it could mediate a reduction in body fat.”


Study #2: How omega-3s prevent/ameliorate metabolic syndrome

The French authors of a recent review article detailed the ways in which omega-3s help prevent or ameliorate metabolic syndrome and thereby reduce the risks of diabetes and heart disease (Carpentier YA et al 2006):

  • Help repair insulin resistance and prevent type 2 diabetes.
  • Reduce blood levels of triglycerides and raise blood levels of “good” HDL cholesterol.
  • Reduce blood pressure, inflammation and the stickiness of blood.
  • Improve the performance of the endothelial tissues that line human arteries.

Interestingly, the authors said that these benefits stem in part from marine omega-3s’ ability to reduce the accumulation of fatty acids in people’s muscles and livers: which appears to be the reason why intravenous omega-3s seem to have saved some at-risk infants (see “Fish Oil Saves “Premie” Babies’ Livers and Lives”).


As they concluded, “The use of n-3 PUFAs [marine omega-3s] should be considered in more global strategies including changes in lifestyle, such as adhering to a healthy Mediterranean type of diet and practicing regular physical exercise.”


Study #3: Separate French review blames metabolic disorders on omega-6 excess

A team at the University of Nice, France published an evidence review indicating that the ratio of omega-3 to omega-6 fatty acids holds one key to preventing metabolic syndrome (Ailhaud G et al 2006).


This French group noted recent findings showing that unlike other fatty acids, including omega-3s, the main omega-6 in meats and poultry (arachidonic acid) promotes the formation of fatty adipose tissue. Arachidonic is believed to exert this effect via its influence on major pro-inflammatory metabolic pathways controlled by two families of enzymes: cyclooxygenase COX) and lipooxygenase (LOX).


Two key COX enzymes, called COX-1 and COX-2, are the targets of anti-inflammatory agents including aspirin and the now-withdrawn COX-2 inhibitor drugs Celebrex and Vioxx. Their pro-inflammatory actions are also inhibited by omega-3s and by the antioxidant pigments in turmeric (curcumin) and unrefined salmon oil (astaxanthin).


Study #4: Czechs find omega-3/omega-6 imbalance fuels obesity

The results of a  revealing animal study published two years ago (Ruzickova J et al 2004) support prior research suggesting that when nursing mothers and infants eat diets high in omega-6 fatty acids and low in omega-3s, it promotes the development of adipose (fatty) tissue in children.


The Czech researchers fed pregnant and nursing mice one of two diets containing equal numbers of calories:

  1. A diet high in omega-6 linoleic acid (LA): the omega-6 fatty acid that is extremely over-abundant in most Americans’ diets.
  2. A diet with a healthy balance of omega-3 and omega-6 fatty acids.

The mice borne by mothers fed the omega-6-heavy diet weighed 40 percent more than the mice borne by mothers fed diet #2, which was properly balanced between omega-3 and omega-6 fatty acids.


Remarkably, the weight difference persisted even after the omega-6-heavy diet group stopped eating the imbalanced diet.


Study # 5: French links today’s obesity epidemic to shifts in fatty acid balance

Another French team wondered whether the balance of omega-3 and omega-6 fatty acids has changed, and whether that change has promoted the observed rise in obesity (Ailhaud G et al 2006).


They examined US government data and found that the “adiposity indices” for 6- to 11 month-old infants increased 1.9-fold and 1.7-fold for boys and girls, respectively, from 1976 to 1994 (The adiposity index measures the proportion of fatty tissue in a person’s body).


As they said, the omega-6 (LA) content of human breast milk in major industrialized countries has also increased while the omega-3 content has remained unchanged, thus producing a continuous increase in the ratio of omega-6 to omega-3 fatty acids in breast milk.


The study authors also noted that while manufacturers of infant formula have added omega-3s to more closely match the average omega-6/omega-3 ratio found in human breast milk, two problems remains:

  1. The average omega-6/omega-3 ratio is probably much higher than it was historically, so the formula ratio is still imbalanced.
  2. The percentage of omega-6 fat in formulas remains higher than in human breast milk.

The authors also noted that there has been a striking increase in the omega-6/omega-3 ratio in France from 1960 to 2000. During these four decades, consumption of plant-derived omega-3 ALA dropped by 40 percent, which resulted in a 2.9-fold increase in the omega-6/omega-3 intake ratio in France.


In addition, the daily fatty acid intake in Francea country with dietary habits better than those in the USincreased by 40 percent from 1960 to 2000.


As the French researchers said:


These profound quantitative and qualitative alterations can be traced in the food chain and appear to be due to changes in human food habits as well as in the feeding pattern of breeding stock [cattle, pigs, poultry]. Thus, we believe that preventing obesity deserves a thorough reevaluation of the… status [of fatty acid intake patterns]...”


Given the tidal wave of metabolic disease looming just over the horizon, that’s putting it mildly. Some already think it makes sense to tax nutritionally dangerous foods as we now tax cigarettes, and for the same reason: to discourage consumption. But we won’t hold our breath.



Sources

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