There has been so much controversy as to whether omega-3 fatty acids have any beneficial effects on heart disease risk or all-cause mortality. I have a special fondness for these fatty acids since they were the topic of my graduate school dissertation. As I remember at that time, these fats were not even mentioned much in the nutrition world and research on their proposed benefits was just beginning (back in the 1980’s that is). So here are a few new studies on these complex, but intriguing fats.
A meta-analysis published in the Journal of the American Medical Association analyzed 20 randomized controlled trials that covered 68,680 patients using fish oil supplements. No significant effects of the supplements were found on any of the following endpoints:
- All-cause mortality
- Cardiac death
- Sudden death
- Myocardial infarction
Fish oil supplements are risky when it comes to getting products you can count on. According to ConusmerLab.com, “contamination, mislabeling and other problems were found in 11 of 35 (30 %) fish oil/omega-3 supplements.” They tested fish oil, krill oil, algal oil and calamari oil supplements. Other problems exist in the study designs themselves such as dose, adherence, baseline intake and the cardiovascular risk groups themselves.
However, two recent studies reported positive results. One was an animal study and the other measured plasma levels of omega-3 fatty acids in elderly patients 65 and older.
The first study fed two groups of mice either a control diet or a DHA-enriched fish oil diet for 5 weeks. B cells were collected from selected tissues and then stimulated in culture. Simply stated, B cells or B lymphocytes produce antibodies that circulate through the lymph and blood to protect us by destruction of antigens (foreign substances) that they encounter. They found that the diet enriched with fish oil enhanced B cell activation and antibody production suggesting that this will enhance immune responses associated with the destruction of pathogens and/or lessen the inflammatory response, according to the authors.
I personally have had some experience in studying the effects of fish oil versus corn oil on antibody responses. In my study I fed rats either a low or high corn oil or fish oil diet for 22 days. All the rats were immunized with a suspension of sheep red blood cells. Thirteen days later, fasted rats were anesthetized and blood samples containing B cells were drawn. Antibody titers (response) were conducted to the sheep red blood cells in a micro titer plate and compared to a control using saline and sheep red blood cells. Each response was inspected to measure the highest dilution at which agglutination (the combining of the antigen and antibody) occurred. The results were as follows:
There were no significant differences in antibody responses between the low corn oil and high corn oil diets or between the low fish oil and high fish oil diets. However, the animals fed either the low fish oil or high fish oil diets produced a significantly (p<0.05) higher antibody titer in response to sheep red blood cells than those fed the low or high corn oil diets. This suggests that the type of dietary fat influences the antibody-mediated component of the immune system in some way and that the omega-3 fats showed a more favorable response. This was part of my dissertation and it should be noted that it was not peer-reviewed or published but presented as a poster session at the Federation of American Societies for Experimental Biologists (FASEB).
The second study conducted by Dariush Mozzaffarian, MD, DrPH and colleagues of the Harvard School of Public Health and reported online in Annals of Internal Medicine measured plasma levels of omega-3 PUFA (EPA, DPA and DHA) in 3, 941 Cardiovascular Health Study patients from 1992 to 1993. They excluded patients taking omega-3 supplements and those with CVD, so 2,692 patients remained. Outcome measures included cause-specific mortality and total coronary heart disease (fatal and nonfatal) and stroke through 2008.
When comparison was done of quintiles of omega-3 PUFAs in plasma, a significant 27% lower risk of death (p<0.001) was observed in the highest quintile. The largest effect on mortality related to the deaths were due to cardiac arrhythmias, which were reduced by almost 50% in patients with the highest versus lowest quintiles. “Patients in the highest quintile lived an average of two more years after age 65 than those in the lowest quintile”, the authors noted.
These studies also avoided the many problems encountered when diets and food intake are reported using food questionnaires with human subjects. Many of these studies involve self-reporting of food intake, which is always subject to error.
Bottom Line: I would continue to eat fish at least two times a week as recommended by many health experts. The word on supplement benefits is yet to be determined. If you are taking supplements, make sure the brand is one you can trust. Dr. Mozaffarian,, said that “the most beneficial levels could be achieved by consuming an average of 400 milligrams of omega-3s a day — the equivalent of weekly consumption of about 3.5 ounces of farmed salmon, 5 ounces of anchovies or herring, or 15 to 18 ounces of cod or catfish.”