Exploring the sense and nonsense of food and health

A Fish Story

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Diet supplement - omega 3 fish oil-based

Diet supplement – omega 3 fish oil-based (Photo credit: Wikipedia)

Are you taking a fish oil supplement?  Have you seen the latest headlines?  “Fish Oil Fizzles”  “Fish oil does not prevent heart attacks” and on and on.

I did my research for my dissertation on fish oils and breast cancer compared to corn oil in the diet –  (we found no differences in cancer rates, by the way).  But with heart disease, the early research seemed so promising.  What is happening?  Read on………

A great deal of research in the past few decades has suggested that EPA and/or DHA (omega-3 fatty acids) reduce blood pressure, reduce triglycerides and inflammation, increase brain blood flow and a give nerve cells structural strength thus reducing heart disease risks as well as providing neurological benefits.  The World Health Organization’s recommends that pregnant and nursing women should consume at least 300 milligrams of omega-3’s daily for fetal brain development and has strongly been supported in clinical trials.

A new study has cast doubt on the cardiovascular benefits of fish-oil pills. A meta-analysis of 20 randomized trials with fish oil supplementation totaling 68, 680 participants found no significant association of reduced risk of stroke, heart attack, all-cause mortality, cardiac death or sudden death compared with those taking fish oil  compared to a placebo.  All the studies lasted at least a year and the average dose was 1500 mg. daily. Americans spend about $15 billion a year on fish oil supplements.  A spokesperson for an omega-3 industry trade group called the review “flawed,” citing the possibility of confounding by heart medications and saying dosages in the trials were low. (JAMA, 2012)

Another review of 14 studies that included a total of 20,485 patients found no significant difference in cardiovascular outcomes between those taking or not taking fish oil supplements.  These studies lasted 1 to 4.7 years and used 400 mg to 4800 mg of EPA and/or DHA per day.  (Archives of Internal Medicine, 2012.)

When diabetics with a history of cardiovascular disease were studied, there was no reduction in cardiovascular events even though they were given 900 mg of EPA and DHA daily for 6 year in comparison to an olive oil placebo. Many of these participants were taking heart medications and already had a median intake of 210 mg of omega-3 fats from their diets which the authors stated may have masked the effects of the fish oils. (NEJM, 2012).

Should you give up on fish oil’s proposed claims?  Not necessarily.  There may be some reasons why these results occurred.

  • In recent years, many of us have gotten more of these beneficial fats in our diets than a few decades ago.  According to the U.N. Food and Agricultural Organization; per capita fish consumption has doubled since 1961. Omega-3 fats have entered the food supply via fortified foods (eggs, margarine), and flax-seed and flax-seed oil in the last decade.  So adding more to an already adequate intake may not do much good.
  • Another reason may be that most of the trials included in the above analyses involved people who already have heart disease or established risk factors; very little research has been done on healthy people.
  • Also assessing heart patients in more recent years involves many of them taking statins and aspirin for proposed heart health.  For example, half of the studies included in the JAMA paper were conducted after statins became commonplace.  In a 2012 analysis of a large European trial, it was reported that fish oil supplements did not prevent a second heart attack among people taking statins, but that it cut the risk by half with people who were not taking them, although this finding did not reach statistical significance due to a small sample size of statin users.
  • Differences in fish oil preparations in the studies are not equal.  Recently, found that when they reviewed 35 products on the market at the present time, only 24 passed quality testing that met their requirements of freshness, purity, and EPA/DHA concentration claims or lack of contamination.
  • Another controversy surrounding the omega fats is the ratio of omega- 6-omega-3 in the diet. Omega-6 fats (also essential for survival) are far more prevalent in American diets than omega-3s.  To put it simply, the more omega-6s in the diet, the less effective the addition of omega 3’s may be.

Several sources of information suggest that human beings evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids (EFA) of approximately 1/1;  whereas in Western diets the ratio is 15/1-16.7/1.  So the ratio of omega-6:omega-3 may be a factor in the prevention of many chronic diseases. For example:

  • In the secondary prevention of cardiovascular disease, a ratio of 4/1 was associated with a 70% decrease in total mortality.
  • A ratio of 2.5/1 reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4/1 with the same amount of omega-3 PUFA had no effect.
  • The lower omega-6/omega-3 ratio in women with breast cancer was associated with decreased risk.
  • A ratio of 2-3/1 suppressed inflammation in patients with rheumatoid arthritis, and a ratio of 5/1 had a beneficial effect on patients with asthma, whereas a ratio of 10/1 had adverse consequences.

It is also important to remember that just taking single nutrient via a supplement (in this case fish oil) will not overcome the lack of an overall healthy diet. Just consuming fish oil without watching the rest of one’s diet is a recipe for disaster.

Should you take a fish oil supplement? Most researchers agree that it is much better to get your omega-3 fats from fish such as mackerel, tuna, and salmon.  At this point, if you do not eat fish or get omega-3 fats from other sources, if you have heart disease and not taking other medications – omega-3 supplements may be beneficial since they appear safe and offer no harm. .  Getting some omega-3s is better than getting none – but the choice is yours in knowing the facts and hopefully opt for a couple of fishmeals a week.  Before taking any supplement, consult with your doctor – you may not need it.

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